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  • 1995-1999  (2,641)
  • 1960-1964  (3,703)
  • 1920-1924  (3,032)
  • Inorganic Chemistry  (8,508)
  • Atomic, Molecular and Optical Physics  (830)
  • Alkaloids
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Material
Years
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Further Alkaloids Common to Ants and Frogs: Decahydroquinolines and a Quinolizidine (1999)
    Springer
    Journal of chemical ecology 25 (1999), S. 1179-1193 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; mass spectrometry ; infrared spectroscopy ; amphibians ; ants ; decahydroquinolines ; quinolizidines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Three alkaloids—two minor decahydroquinolines (DHQs) and a major quinolizidine—were detected in an extract of a Brazilian myrmicine ant (Solenopsis (Diplorhoptrum) sp. picea group). One DHQ (3) was identical to a known frog-skin alkaloid, cis-195A (cis-5-methyl-2-propyldecahydroquinoline), while the second DHQ, an isomer of 3, designated 195J, was assigned a tentative cis-2-methyl-5-propyldecahydroquinoline structure (2) based on mass and infrared spectra. The third alkaloid proved identical to the frog-skin alkaloid 195C, for which a structure had not been previously proposed. Mass and infrared spectral analysis, including chemical ionization tandem mass spectrometry, indicated a 4-methyl-6-propylquinolizidine structure (1) for 195C. The four possible diastereomers were synthesized and the (6Z,10E)-4-methyl-6-propylquinolizidine diastereomer (1b) was identical to the natural alkaloid. Skin extracts of a population of a Madagascan mantelline frog contained, among other alkaloids, minor amounts of the same alkaloid triad 1–3 with 1 again predominating. The common occurrence of alkaloids 1–3 in both ant and frog supports the hypothesis that ants are a likely dietary source for sequestered frog-skin alkaloids and brings to six, the alkaloid classes common to ant and frog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020898229304
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis Mediated by Ring-Closing Metathesis - Applications in the Synthesis of Azasugars and Alkaloids (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 959-968 
    Details
    ISSN: 1434-193X
    Keywords: Heterocycles ; Alkaloids ; Castanospermine ; Metathesis ; Azasugars ; Manzamine A ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The application of the ring-closing metathesis (RCM) reaction to the construction of a wide variety of nitrogen-containing ring systems is described. The examples include pyrrolizidine, indolizidine, and quinolizidine derivatives related to azasugars. A formal total synthesis of castanospermine (5) is presented. The utilisation of two RCM steps in the synthetic sequence leading to the multicyclic ABCDE nucleus 7 of the complex alkaloid manzamine A (6) is discussed.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    A Stereoselective Synthesis of Nonracemic (+)-Desoxoprosophylline by a Tandem Wittig [2+3]-Cycloaddition Reaction (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1407-1414 
    Details
    ISSN: 1434-193X
    Keywords: L-Ascorbic acid ; (+)-Desoxoprosophylline ; Lactones ; Alkaloids ; Domino reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -L-Ascorbic acid serves as chiral starting material for the synthesis of (+)-desoxoprosophylline. The synthetic pathway includes the formation of an O-protected 5-azido-2,3-dideoxysugar which is subjected to a tandem Wittig [2+3]-cycloaddition reaction, leading to the heterocyclic core unit of (+)-prosophylline. Stereoselective hydrogenation and chain elongation yields the desired alkaloid.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Plakinamines C and D and Three Other New Steroidal Alkaloids from the Sponge Corticium sp. (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 697-701 
    Details
    ISSN: 1434-193X
    Keywords: Corticium sp. ; Steroids ; Alkaloids ; Secondary metabolites ; Cytotoxic activity ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Five new steroidal alkaloids, plakinamines C (1) and D (2), and the related compounds 3-5 have been isolated from the Vanuatu sponge Corticium sp. Their structures have been elucidated by a detailed spectroscopic analysis, including 2D-HMBC and ROESY correlation experiments. The new compounds show significant in vitro cytotoxicity against human bronchopulmonary non-small-cell lung carcinoma cells (NSCLC-N6) with IC50 values of 〈 3.3-5.7 μg/mL. When tested against T leukemia virus type one (HTLV-I), compounds 1, 4 and 5 were found to exhibit slight anti-HIV activity.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Syntheses of Batzelline A, Batzeline B, Isobatzelline A, and Isobatzelline B (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1173-1183 
    Details
    ISSN: 1434-193X
    Keywords: Marine alkaloids ; Pyrroloquinoline ; Total synthesis ; Heterocycles ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Batzellines A and B (1a, b) and isobatzellines A and B (2a, b) are 1,3,4,5-tetrahydropyrrolo[4,3,2-de]quinoline-containing marine alkaloids characterized by the presence of a methylthio substituent at C-2 of the tricyclic system. We describe here the total synthesis of these natural compounds following the synthetic strategy that we have used previously for the synthesis of damirones A and B, batzelline C, isobatzelline C, discorhabdin C, and makaluvamines A, B, C, and D. The introduction of the methylthio group by electrophilic substitution of a pyrrolo[4,3,2-de]quinoline, appropriately substituted and in a suitable oxidation state, is the key step in the success of these syntheses.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Lewis Acid Assisted Vinylogous Mannich and Mukaiyama Aldol Reactions: A Route to Densely Hydroxylated Indolizidine Alkaloid Analogues (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1395-1400 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Vinylogous Mannich reaction ; Vinylogous Mukaiyama aldol reaction ; Glycosylation inhibitors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -The hydroxymethyl-substituted indolizidines 6 and 7, representative members of a ring-B-expanded alexine-australine subclass, are readily accessible by starting with furan-based silyloxydiene 12 and hydroxymethyl hemiaminal 11, through a synthesis sequence involving a scantily exploited vinylogous version of the Mannich reaction. The key iminium electrophilic acceptor 11 is, in turn, available through a vinylogous intermolecular Mukaiyama aldolization process between pyrrole-based silyloxydiene 8 and (S)-glyceraldehyde 9.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    A Unified Synthetic Strategy for the Indolopyridine Alkaloid Group (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 373-378 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cross-coupling ; N-Heterocycles ; Palladium ; Synthesis design ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Thermal or acetyl chloride induced cyclization of bromoenamide 10 affords the pentacyclic derivative 12 with high yield and regioselectivity. From this common synthetic intermediate, palladium-catalyzed reactions allow the total synthesis of indolopyridine alkaloids 1-6.Supporting information for this article is available on the WWW under -http://www.wileY-Vch.de/contents/jc_2046/1999/98332_s.pdf or from the author.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New Piperidine Alkaloids from Two Ladybird Beetles of the Genus Calvia (Coccinellidae) (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 1749-1755 
    Details
    ISSN: 1434-193X
    Keywords: Natural products ; Piperidines ; Alkaloids ; Coccinellidae ; Calvia14-guttata ; Calviaguttata ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alkaloids of two coccinellid beetles, Calvia14-guttata and C.10-guttata have been studied. The major alkaloid of these two species is the new piperidinic cis-lactone 1a, for which the name calvine has been coined. The corresponding trans-lactone 1b (2-epicalvine) is also present as a minor constituent (±10%) in both species. We report here the structure determination and the total synthesis of these compounds. Kept in methanolic solution, these lactones undergo epimerisation as well as opening of the lactone ring leading to a complex mixture of nine main components.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    A General Approach to Indolizidine Alkaloids From 1-Benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols: Synthesis of (+)-Monomorine I (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 3277-3280 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Asymmetric synthesis ; Palladium ; Amino alcohols ; Natural products ; Monomorine I ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A versatile method for the preparation of indolizidine alkaloids from 1-benzyloxy-5-(p-toluenesulfonamido)-3-alken-2-ols as stereodefined key intermediates has been developed. The utility of this approach was demonstrated by the synthesis of (+)-monomorine I.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    An Efficient Synthesis of 5-(or 6-)Arylbenzoindolizidine and -quinolizidine Derivatives (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2345-2352 
    Details
    ISSN: 1434-193X
    Keywords: Horner reaction ; Enamides ; Reductions ; Cyclizations ; Alkaloids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new methodology for the synthesis of (hetero)arylated benzoindolizidine and benzoquinolizidine derivatives through sequential reduction of pyrrolidine- and piperidine-based aromatic enamides, and ultimate cyclization, is reported.
    Additional Material: 2 Ill.
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  • 11
    Electronic Resource
    Electronic Resource
    Iodocyclisation of 1,4-Dihydropyridines; Synthesis and Reactivity of 1-Iodoindolo[2,3-a]quinolizidines (1999)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1999 (1999), S. 2997-3003 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Cyclizations ; Iodine ; Nitrogen heterocycles ; Oxidations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The addition of iodine (or related species) to β-acyl-N-alkyl-1,4-dihydropyridines 1, which possess an N-substituent with an appropriate nucleophile moiety, leads to the corresponding 3-iododihydropyridinium ions, which undergo an internal nucleophilic attack to give, regio- and stereoselectively, the iodobi(poly)heterocyclic ring systems 2a-f in good yields. Reactivity studies on the iodoindoloquinolizidines 2e,f lead to the pentacyclic cyclopropane systems 4a,b, azides 5 and 6, norderivative 9 and, by a base-induced elimination, dihydropyridine 10, a precursor of the zwitterionic alkaloids flavopereirine and 6,7-dihydroflavopereirine.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Modes of Action of Allelochemical Alkaloids: Interaction with Neuroreceptors, DNA, and Other Molecular Targets (1998)
    Springer
    Journal of chemical ecology 24 (1998), S. 1881-1937 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; molecular targets ; neuroreceptors ; DNA intercalation ; DNA polymerase ; reverse transcriptase ; protein biosynthesis ; membrane stability ; nicotine receptor ; muscarinic receptor ; serotonin receptor ; adrenergic receptors
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Several alkaloids are toxic to insects and vertebrates and, in addition, can inhibit the growth of bacteria and plant seedlings. In vitro assays were established to elucidate their modes of action and to understand their allelochemical properties. Basic molecular targets studied, present in all cells, included DNA intercalation, protein biosynthesis, and membrane stability. The degree of DNA intercalation was positively correlated with inhibition of DNA polymerase I, reverse transcriptase, and translation at the molecular level and with toxicity against insects and vertebrates at an organismic level. Inhibition of protein biosynthesis was positively correlated with animal toxicity. Molecular targets studied, present only in animals, included neuroreceptors (alpha1, alpha2, serotonin, muscarinic, and nicotinic acetylcholine receptors) and enzymes related to acetylcholine (acetylcholine esterase and choline acetyltransferase). The degree of binding of alkaloids to adrenergic, serotonin, and muscarinic acetylcholine receptors was positively correlated in G-protein-coupled receptors. Receptor binding and toxicity was correlated in insects. The biochemical properties of alkaloids are discussed. It is postulated that their structures were shaped in a process termed “evolutionary molecular modeling” to interact with a single and, more often, with several molecular targets at the same time. Many alkaloids are compounds with a broad activity spectrum that apparently have evolved as “multipurpose” defense compounds. The evolution of allelochemicals affecting more than one target could be a strategy to counteract adaptations by specialists and to help fight off different groups of enemies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022315802264
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  • 13
    Electronic Resource
    Electronic Resource
    A sponge/dinoflagellate association in the haplosclerid sponge Haliclona sp.: cellular origin of cytotoxic alkaloids by Percoll density gradient fractionation (1998)
    Springer
    Cell & tissue research 293 (1998), S. 365-373 
    Details
    ISSN: 1432-0878
    Keywords: Key words Sponges ; Alkaloids ; Nematocysts ; Percoll density gradient fractionation ; Secondary metabolites ; Dinoflagellates ; Symbiodinium microadriaticum ; Sponge ; Haliclona sp. (Porifera)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Light-microscopic and electron-microscopic studies of the tropical marine sponge Haliclona sp. (Order: Haplosclerida; Family: Haliclonidae) from Heron Island, Great Barrier Reef, have revealed that this sponge is characterized by the presence of dinoflagellates and by nematocysts. The dinoflagellates are 7–10 μm in size, intracellular, and contain a pyrenoid with a single stalk, whereas the single chloroplast is branched, curved, and lacks grana. Mitochondria are present, and the nucleus is oval and has distinct chromosomal structure. The dinoflagellates are morphologically similar to Symbiodinium microadriaticum, the common intracellular symbiont of corals, although more detailed biochemical and molecular studies are required to provide a precise taxonomic assignment. The major sponge cell types found in Haliclona sp. are spongocytes, choanocytes, and archaeocytes; groups of dinoflagellates are enclosed within large vacuoles in the archaeocytes. The occurrence of dinoflagellates in marine sponges has previously been thought to be restricted to a small group of sponges including the excavating hadromerid sponges; the dinoflagellates in these sponges are usually referred to as symbionts. The role of the dinoflagellates present in Haliclona sp. as a genuine symbiotic partner requires experimental investigation. The sponge grows on coral substrates, from which it may acquire the nematocysts, and shows features, such as mucus production, which are typical of some excavating sponges. The cytotoxic alkaloids, haliclonacyclamines A and B, associated with Haliclona sp. are shown by Percoll density gradient fractionation to be localized within the sponge cells rather than the dinoflagellates. The ability to synthesize bioactive compounds such as the haliclonacyclamines may help Haliclona sp. to preserve its remarkable ecological niche.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004410051128
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  • 14
    Electronic Resource
    Electronic Resource
    An Expeditious Synthesis of the Dendrobatid Indolizidine Alkaloid 167B (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 865-870 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Enaminones ; Indolizidines ; Sulfide contraction ; Total synthesis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the racemic title alkaloid 1 has been accomplished in eight steps and 7.2% overall yield from pyrrolidine-2-thione (5) and ethyl hex-2-enoate (6). Key steps include a ring closure that takes advantage of the nucleophilicity of a vinylogous urethane 8, and stereoselective reduction of the C=C double bond of a bicyclic vinylogous amide 12.
    Type of Medium: Electronic Resource
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  • 15
    Electronic Resource
    Electronic Resource
    Cyclization of 3-Aminoacrylates - Total Synthesis of Pumiliotoxin C and Related Stereoisomeric Compounds (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 2641-2646 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Total synthesis/Pumiliotoxin ; PTX-C ; PTX isomers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is described for the synthesis of pumiliotoxin C (1a) and related stereoisomeric compounds 1c-1f. Starting from (+)- or (-)-3-methylcyclohexanone (6a,b), the oxo esters 7a and 7b were prepared. Condensation with (+)- or (-)-3-aminohexanol (8a,b) gave the stereoisomeric 3-aminoacrylates 9a, 9b and 9c. The hydroxy group of the amino-acrylates was transformed into bromide using the tosylate method. Cyclization of the bromides led to unsaturated quinoline ring systems. Finally, decarboxylation and catalytic hydrogenation gave the different cis- and trans-fused stereoisomeric alkaloids of the pumiliotoxin C type. The structures were verified by X-ray analysis.
    Type of Medium: Electronic Resource
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  • 16
    Electronic Resource
    Electronic Resource
    2-(Het)aryl-Substituted 7-Azabicyclo[2.2.1]heptane Systems (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1997-2001 
    Details
    ISSN: 1434-193X
    Keywords: Alkaloids ; Acetylcholine receptor ; Palladium ; C-C coupling ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Epibatidine (1) is a recently discovered trace alkaloid found in the skin of a Latin-American poisonous frog. Its remarkably high analgetic activity is accompanied by high toxicity. Therefore, in order to tune its biological activity, a convergent and efficient synthetic pathway was sought to synthesize epibatidine derivatives with different (het)aryl substituents. The hydro(het)arylation of the key intermediate 7-azabicycloheptene (10) represents such an approach. The synthesis of 10 by a Diels-Alder reaction of an N-activated pyrrole (7) with ethynyl p-tolyl sulfone (6) and subsequent steps has been optimized. The crucial last step, the reductive cleavage of the vinyl sulfone 9, has been replaced by a high-yield fluoride-induced degradation of the β-silylated sulfone 12 to give 10. A number of structurally different racemic epibatidine analogs (16b-e) can be prepared by palladium-catalyzed hydro(het)arylation of 10 with iodo(het)arenes 15b-e in good yields.
    Type of Medium: Electronic Resource
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  • 17
    Electronic Resource
    Electronic Resource
    Stereoselective Total Synthesis of Enantiomerically Pure 1-Trifluoromethyl Tetrahydroisoquinoline Alkaloids (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 435-440 
    Details
    ISSN: 1434-193X
    Keywords: β-Iminosulfoxides ; Quaternary stereocentre ; Pictet-Spengler reaction ; Alkaloids ; Fluorine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure 1-trifluoromethyl-tetrahydroisoquinoline alkaloid analogues, in which C-1 is a quaternary stereogenic centre, have been synthesized by stereoselective intramolecular Pictet-Spengler reaction of the N-arylethyl γ-trifluoro-β-iminosulfoxide (R)-3, and subsequent elaborations of the sulfinyl auxiliary. The absolute stereochemistry of the stereogenic centre was determined by X-ray diffraction on the α-phenylpropionic ester (1R,2′S)-10.
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  • 18
    Electronic Resource
    Electronic Resource
    Synthesis of 5-epi-Isofagomine via Asymmetric Chelate-Enolate Claisen Rearrangement (1998)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1998 (1998), S. 1155-1159 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; Alkaloids ; Chelates ; Rearrangements ; Glycosidases ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Polyhydroxylated piperidines are an interesting class of glycosidase inhibitors. Chelate enolate Claisen rearrangement of N-protected chiral amino acid esters gives rise to γ,δ-unsaturated amino acids, which can be converted to this type of alkaloids. The potential glycosidase inhibitor 5-epi-isofagomine (5) was synthesized by this approach in a highly stereoselective fashion.
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  • 19
    Electronic Resource
    Electronic Resource
    Effect of acetylsalicylic acid on secondary metabolism ofCatharanthus roseus tumor suspension cultures (1997)
    Springer
    Plant cell reports 16 (1997), S. 287-290 
    Details
    ISSN: 1432-203X
    Keywords: Catharanthus roseus ; Acetylsalicylic acid ; Aspirin ; Alkaloids ; suspension cultures ; tumor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Addition of various concentrations (0.5–20 mM) of acetylsalicylic acid (ASA) to tumor lines ofCatharanthus roseus cultivatedin vitro and requiring corn starch as carbon source, produced remarkable effects on secondary metabolite production. An increase of 505% total alkaloids per culture (cells plus liquid medium), 1587% total phenolics (liquid medium), 612% total furanocoumarins (liquid medium) and 1476% total anthocyanins (liquid medium) was detected. 1 mM ASA in combination with other elicitors, such as homogenates ofAspergillus fumigatus or trans-cinnamic acid, did not further increase the metabolite content substantially. The results suggest that ASA could act as a new biotic elicitor of metabolite production inC. roseus cell suspension culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01088282
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  • 20
    Electronic Resource
    Electronic Resource
    On the dynamics of a linear and a nonlinear quantum oscillator with randomly changing harmonic frequency (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 265-272 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Numerical experiments with a nonlinear (λχ4) oscillator which has its harmonic frequency changing randomly with time reveal certain interesting features of its dynamics of quantum evolution. When λ = 0, the level populations are seen to oscillate. But, as the nonlinear coupling is switched on (λ 〉 0), a threshold is reached at λ = λc when the evolution is seen to be characterized by an abrupt transition dominantly to the highest available state of the unperturbed (initial) oscillator. It is shown that this transition probability is maximized at a particular value of λ. The time threshold for this transition decreases with increasing nonlinear coupling strength. The numerically obtained structures of the underlying quantum-phase spaces of the linear and nonlinear random oscillators are examined. Possible use of these results in a problem of chemical origin is explored. © 1997 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 21
    Electronic Resource
    Electronic Resource
    Electronic structure of testosterone: A semiempirical and ab initio assessment (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 279-289 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Testosterone (17β-hydroxy-4-androsten-3-one) was studied by the semiempirical AM1 and PM3 and ab initio STO-3G*, 3-21G*, and 6-31G* methods. The goals were to compare those methods and to know the electronic structure of the hormone. Full geometry optimization was performed, and two crystal conformers (T1 and T2), and experimental dipole moment in solution were used for comparison. One conformer with a dipole moment similar to the solvated conditions was generated. Total energy, entalphies, dipole moments, charges, electrostatic potentials, and highest occupied molecular orbitals (HOMO) and lowest unoccupied molecular orbital (LUMO) were calculated. Root-mean-square (RMS) index of the theoretical molecules against T1 and T2 showed best results with the 3-21G* and 6-31G* methods, while AM1 gave better energies than PM3. Dipole moments were directed toward the OH group and the botton face of the A ring. The frontier orbitals were located along the C4-C5 π bond, particularly the LUMO was split between C4 and C5, predicting the action of enzymes at C5 yielding to 5α and 5β-reduced androgens. Electrostatic potentials might be also of biological importance since they are coincidental with the dipole-moment orientation. Finally, it is interesting that the solvatedlike conformer, its properties, and the OH group laid between the same group of T1 and T2 and with a total energy between the crystals and the gas phase or in vacuo conditions. This results might also explain the biology of testosterone and use them to model the hormone-receptor interaction. © 1997 John Wiley & Sons, Inc.
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    Photoelectron spectra of molecules. II. Carboxylic acids and their esters (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 303-314 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: He I photoelectron (PE) spectra of four carboxylic acids and five esters are measured. Semiempirical and ab initio quantum chemical calculations are used for the interpretation of the spectra. The complex approach which uses empirically established relationships (the dependence of valence electron ionization energies on proton affinities in the gas phase, on the core level ionization energies, and on the structure) was developed. © 1997 John Wiley & Sons, Inc.
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    Molecular orbital analysis of chemical carcinogens (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 323-328 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simple molecular orbital calculations are employed in searching electronic parameters which may characterize the chemical carcinogens. Using frontier orbitals, the carcinogen-DNA bond formation is described as an electron transfer from the highest occupied molecular orbital (HOMO) of DNA to the lowest unoccupied molecular orbital (LUMO) of the carcinogen. Analysis of the DNA bases units shows that the electron donation occurs preferentially at the guanine site. The calculated low LUMO energy of several carcinogens indicate correctly the electrophilic character of these compounds. The difference between the carcinogen and the ultimate carcinogen is analyzed. Epoxides, free radicals, alkylating agents, and other metabolite forms are studied. A reasonable correlation is found between the LUMO energy and the carcinogenic function. © 1997 John Wiley & Sons, Inc.
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    Molecular dynamics simulation of the free surface of liquid formamide (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1123-1131 
    Details
    ISSN: 0020-7608
    Keywords: MD simulations ; liquid surface ; formamide ; molecular orientation ; molecular surface density ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular dynamics simulations of liquid formamide(HCONH2) were carried out using the GROMOS software. The formamide molecule is represented by all of its atoms with all internal degrees of freedom. In contrast to other simulations dealing with bulk properties, this study focuses on the interface liquid-vacuum for the first time. We show that the molecular plane is tilted out of the surface, exposing the HCO group to the vacuum.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1123-1131, 1997
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    A very accurate grid method for the solution of Schrödinger equations: The helium ground state (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1065-1078 
    Details
    ISSN: 0020-7608
    Keywords: very precise eigenvalues ; very accurate grid method ; general solution for Schrödinger equations ; rapidly convergent treatment for helium eigenvalues ; superconvergence ; optimization of grids ; treatment of continuum ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extension to the theory of Schrödinger equations has been made which enables the derivation of eigenvalues from a consideration of a very small part of geometric space. The concomitant unwanted continuum effects have been removed. The theory enables very convergent or “superconvergent” calculations. In the case of the helium ground state, E=-2.90372437703411987 Eh was obtained from 251 terms. The result is comparable to that from the largest variation calculations so far carried out reinforced by extrapolation techniques. The theory is extensible to atoms and molecules irrespectively of the number of electrons or nuclear centers. In these cases, the advantage of “superconvergent” calculations will be more pronounced than in the case of helium.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1065-1078, 1997
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    Noninteger principal quantum numbers increase the efficiency of Slater-type basis sets (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 1-11 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Roothaan-Hartree-Fock (RHF) calculations are carried out for the ground states of the atoms from helium to xenon using a minimal basis set of Slater-type functions whose principal quantum numbers are allowed to take variationally optimal noninteger values. The resulting energies are substantially superior to those obtained previously under the usual restriction that principal quantum numbers be positive integers. The energy lowering relative to the single-zeta wave functions of Clementi and co-workers ranges from 0.0066 Eh in He to 11.2 Eh in Xe. Our results are superior to those obtained by Höjer using a minimal basis set of unconventional binomially screened basis functions. Noninteger principal quantum numbers benefit d-orbitals the most; physically realistic negative d-orbital energies are obtained in all cases including those transition-metal atoms for which a conventional single-zeta STF basis leads to positive d-orbital energies. © 1997 John Wiley & Sons, Inc.
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    Ab initio study on the reaction of Sc+ + CH4 → Sc+(SINGLE BOND)CH2 + H2 (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 23-27 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An ab initio study on the reaction of the ground state (3D) and the excited state (1D) of Sc+ with methane was performed. Reaction channels on the singlet and triplet potential surface (PES) and the reaction mechanism are examined and discussed. Three regions of the potential surface was studied: the molecular complex, the C(SINGLE BOND)H insertion products, and the transition states for the reaction. Comparisons between singlet and triplet PESs show that the excited state (1D) of Sc+ has more reactivity with methane than does the ground state (3D) due to the spin quantum number conservation with the more stable insertion intermediate. © 1997 John Wiley & Sons, Inc.
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    Influence of hybridization displacement charge on the description of electrostatic potentials of molecules with multiple electrophilic sites (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 67-76 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The importance of the hybridization displacement charge (HDC) in describing molecular electrostatic potential (MEP) maps was demonstrated by studying six molecules; pyrazine N-oxide, para-nitropyridine, 5-nitropyrimidine, 3-nitropyridazine, N2, and N2O. It is shown that continuously distributed HDC-corrected Löwdin charges reproduce the MEP features of these molecules, most of which have competing electrophilic sites, in agreement with ab initio results. Further, it is found that for homonuclear diatomic molecules MEP minima can be located properly using HDC-corrected Löwdin (or HDC-corrected Mulliken) continuously distributed charges, but these features cannot be obtained using the conventional Löwdin (or Mulliken) charges. It was shown that the order of molecular electric field (MEF) values near the different electrophilic sites becomes changed when one moves away from the molecules. Thus, pyridine-type nitrogen atoms are the preferred binding sites close to the molecules, while at large distances, effects of oxygen atoms of the NO groups become dominant. © 1997 John Wiley & Sons, Inc.
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    Crystalline and local vibrations of paired bases in poly(dG)-poly(dC) interacting with the h-b-1 hydrogen bond (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 115-124 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Some types of atomic vibrations in a chain of the DNA type constructed of G-C pairs were studied. These are the atomic vibrations of the lateral groups of guanine and N(3)H(1)H(2) of cytosine connected by the hydrogen bond h-b-1 and the vibrations of the centers of masses of bases in the direction parallel to bonds h-b-i, i = 1-3. The vibrations mix partially due to the dependence of the energy of the bond h-b-1 on its length and split into two bands because of the interaction between neighboring base pairs. It was shown that the excitation of the bond h-b-1 results in the splitting off of the two local vibrations and in a small deformation of the chain in the vicinity of the pair with the localized hydrogen bond. The law of the dispersion of band vibrations, values of the split-off frequencies, and degree of poly(dG)-poly(dC) chain deformation were determined. © 1997 John Wiley & Sons, Inc.
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    Modeling properties of the HF dimer in argon clusters (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 55-65 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We compare geometry configurations, vibrational properties, and electronic structures of (HF)2 in a free state and inside argon atom shells Arn. For the first stage, molecular dynamics calculations for the (HF)2 · Ar62 heterocluster are performed with the help of model potentials HF(SINGLE BOND)HF, Ar(SINGLE BOND)Ar, and Ar(SINGLE BOND)HF. Then, ab initio quantum chemistry analysis is carried out for the smaller systems (HF)2 · Ar15 and (HF)2 · Ar6 when keeping the argon atoms closest to the trapped dimer. We conclude that the hydrogen-bonded complex (HF)2 gains some extra stability inside the argon shells, originating primarily from a decrease of intermolecular distance RFF. Electronic structure calculations are in accord with the changes in dynamical properties, namely, a noticeable increase in the vibrational frequency assigned to the F(SINGLE BOND)F stretching mode (+25 cm-1) and decrease in rms deviations for the corresponding coordinate δFF. In addition to these changes, the argon atoms of the nearest solvent shell donate a small fraction of electron charge which is spent for an increase of population of the antibonding orbital σ*Hf(SINGLE BOND)Ff of the free monomer unit and shift orbital energies primarily of the lone-pair fluorine species. These shifts are greater than the changes due to geometry alterations and the possible inaccuracies of the calculation scheme. © 1997 John Wiley & Sons, Inc.
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    Efficient evaluation of the algebrants of VB wave functions using the successive expansion method. I. Spin S = 0, ½ (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 245-259 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An efficient expansion method for the evaluation of VB matrix elements is introduced. The overlaps of VB wave functions of N electrons can be treated as algebrants, i.e., generalized determinants, of N × N matrices. An algebrant can be expanded with subalgebrants of lower orders in a successive way. By choosing Rumer spin bases and appropriately arranging the expansion, it is found that the number of unique subalgebrants involved in the expansion increases in a quite moderate way with N. In contrast to the traditional symmetric group approach, which explicitly utilizes all N! representation matrices, the new strategy incorporates the group theoretical factors in a simple way in the successive expansion. As only the unique subalgebrants are further expanded, the computational effort required by the new strategy scales in a very acceptable manner with the increasing number of electrons. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62: 245-259, 1997
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    Characters of two-row representations of the symmetric group (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 261-264 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Characters of irreducible representations (irreps) of the symmetric group corresponding to the two-row Young diagrams, i.e., describing transformation properties of N-electron eigenfunctions of the total spin operators, have been expressed as explicit functions of the number of electrons N and of the total spin quantum number S. The formulas are useful in various areas of theory of many-electron systems, particularly in designing algorithms for evaluation of spectral density moments. © 1997 John Wiley & Sons, Inc.
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    Computation of bond dissociation energy for sulfides and disulfides with ab initio and density functional theory methods (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 291-296 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The geometries and S-H, S-S, and S-C bond dissociation energies for hydrogen sulfide, hydrogen disulfide, methanethiol, dimethyl disulfide, and dimethyl disulfide were calculated with both ab initio (ROHF and MP2), hybrid (BHandH, BHandHLYP, Becke3LYP and Becke3P86), and nonlocal (BLYP and BP86) density functional theory (DFT) methods. In all studies the 6-31 + G(d) basis set is used. The computed results are compared to the experimentally obtained values, targeting the selection of a suitable ab initio or DFT method for the study of these systems. © 1997 John Wiley & Sons, Inc.
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    Theoretical study on the pyrolysis mechanism and kinetics of β-hydroxyketones (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 297-302 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mechanism and kinetics for the decomposition of β-hydroxypropaldehyde, primary and secondary β-hydroxyketones, were studied by using ab initio RHF/6-31G and RHF/6-31G* methods. The activation barriers of these reactions were refined to be 39.57, 40.10, and 36.80 kcal mol-1 at the MP2/ /RHF/6-31G* level, respectively. The calculated results show that each decomposition is a concerted process with hydrogen transferring and bond breaking via a six-membered cyclic transition state. The thermal rate constants of the decomposition of primary and secondary β-hydroxyketones were obtained by calculating microcanonical probability fluxes through each transition state. It is theoretically confirmed that methyl substitution at the hydroxyl carbon of β-hydroxyketones causes a small enhancement in rates. The theoretical investigations of the mechanism and the rate constants are in agreement with the experimental results. © 1997 John Wiley & Sons, Inc.
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    Numerical solution for the ground-state energy of the anisotropic Heisenberg model (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 13-21 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An analysis of the anisotropic Heisenberg model is carried out by solving the Bethe ansatz solution of the model numerically as a function of the anisotropy parameter for finite N. A brief introduction to the limit of the infinite chain is presented. The energy for a few special limiting cases of the anisotropy parameter in the Hamiltonian are worked out. Numerical results for finite cycles as well as for the infinite chain are given. Comparison can then be made with the case of finite increasing N. © 1997 John Wiley & Sons, Inc.
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    Evaluation of a characteristic atomic radius by an ab initio method (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 47-53 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The MELD program is employed to evaluate the Slater average potential v(r) felt by an electron at the point r within an atom. The characteristic radius R of the atom is then defined by the classical turning point equation v(R) = -I, where I denotes the first ionization potential of the atom. The atomic radii defined in this way have a close correlation with the van der Waals atomic radii. © 1997 John Wiley & Sons, Inc.
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    Accurate nonrelativistic energies for 2Pe states of the Li isoelectronic series (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 77-88 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Highly accurate upper bounds for several 2Pe states of the Li isoelectronic series obtained by extensive Hylleraas-Cl calculations are given. The best value for the 22Pe state (1s2p2) of Li is -5.21373920 au. The evaluation of the occurring integrals is given explicitly. Additionally, we present some expectation values and isotope energies of the Li isoelectronic series. © 1997 John Wiley & Sons, Inc.
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    Hydrogen-bonding effects, electrostatic potential, and the antitumor activity of flavone acetic acid and related compounds. III. Ab initio studies on the conformation space (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 97-113 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Restricted geometry optimizations at the ab initio SCF level with the 3-21G basis set were employed to investigate the conformation space of flavone acetic acid (FAA) and its related compounds. All the conformations are produced from a conformation which is, according to our previous work, probably the active conformation in terms of antitumor activity shown by these compounds. Detailed studies on FAA were carried out while only brief discussions are made on the analogs. The main results obtained are that (1) FAA is a very flexible molecule, e.g., with the energy barrier up to about 3 kcal mol-1 from the reference conformation, the important torsional angle τ1 can change from 27.0° to 117.0°, τ2 from -168.0° to 2.0°, and τ3 from -50.0° to 30.0°; (2) the hydrogen-bonding effect plays an important role in determining lower-energy conformations; (3) among all the FAA conformations considered, some are active and some are inactive; (4) it seems that the analogs will have similar behavior to FAA when the torsional angle τ3 is restricted to the values which are around the equilibrium values; and (5) the hypothesis put forward previously has been further developed in this work. Now, we postulate that efficient charge transfers will lower the energy and that proper charge transfers will activate the molecule. There are mainly two different types of charge transfer corresponding to two different types of conformation, which are specified in this article. © 1997 John Wiley & Sons, Inc.
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    Evaluation of screened nuclear attraction and electron repulsion molecular integrals over Gaussian basis functions (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 273-278 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Analytical solutions to the Yukawa-like screened Coulomb nuclear attraction and electron repulsion molecular basic integrals, as well as to the basic integrals required to compute the virial coefficient, over Gaussian basis functions, are derived and cast into a practical closed form, suitable to interface with modern codes for the calculation of molecular electronic structure. © 1997 John Wiley & Sons, Inc.
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    Power series with rational coefficients for two-electron atom energies (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1079-1089 
    Details
    ISSN: 0020-7608
    Keywords: large-order perturbation theory ; lie algebra ; three-body problem ; symbolic computations ; helium atom ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of o(4, 2) operator replacements is generalized. As a result, the series whose limiting values when the variable goes to  +∞ should correspond to the two-electron atom energies now have rational coefficients. This generalization allows one also to compute the series for the case of singlet S symmetry, a case which could not be considered in the previous original formulation of the method. Series with rational coefficients for the helium singlet and triplet S ground-state energy are calculated up to order 41 and 45, respectively. Moreover, symbolic computations also allow one to give the first few coefficients of these series for arbitrary values of the nuclear charge Z. Finally, a new method for analytic continuation to the limit  +∞ is presented for the energies of the helium singlet and triplet ground states.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1079-1089, 1997
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    A study of bond-cleavage and bond-formation processes in some simple metathesis reactions (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1099-1106 
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    ISSN: 0020-7608
    Keywords: metathesis reactions ; bond order ; free valence ; minimum energy path ; nonsynchronization ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A few simple atom-transfer reactions (i.e., Ȧ+X-A→A-X+Ȧ) are studied by quantum mechanical ab initio methods. Emphasis is given to the detailed analysis of density matrices rather than to the energetics. Results reveal that during these reactions a small free valence always develops on the migrating atom at the transition state. The barriers in these reactions arise from the greater extent of bond cleavage in the reactant than that of bond formation in the transition state. Analysis of bond orders estimated from bond lengths using Pauling's relation also leads to the fact that the bond-cleavage process is more advanced than is the bond-formation process in these reactions.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1099-1106, 1997
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    Theoretical study on Pd dimer and trimer interaction with the hydrogen molecule (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 29-45 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The H2 interaction with the Pd dimer and trimer were studied using multiconfigurational self-consistent field (MC-SCF) calculations with the relativistic effective core potential (RECP); the correlation energy correction was included in the extended multireference configuration interaction (MRCI), variational and perturbative to second order. Here, we considered the Pd2 first six states: 3Σ+u, 1Σ+g, 3Πg, 3Δxy, 1Σ+u, and 3Σ+g. For them, the four geometrical approaches included were the side-on H2 toward Pd2, for the hydrogen molecule in and out the Pd dimer plane; the perpendicular end-on H2 toward Pd2; and the perpendicular end-on Pd2 to H2. The Pd2 ground state is 3Σ+u, which only captures H2 in the C2v end-on approach, softly relaxing the H(SINGLE BOND)H bond. The closed-shell 1Σ+g captures the H2 molecule in all the approaches considered: The side-on approach of this state presents deep wells and relaxes the H(SINGLE BOND)H bond, and the end-on approach captures H2 with a relatively longer H(SINGLE BOND)H distance and also a deep well. The 3Πg state was the only one which did not capture H2. For the triangular Pd3 clusters, H2 was approached in the C2v symmetry in and out of the Pd3 plane. In the triangular case, H2 was absorbed in both spin states, with deep wells and relaxing the H(SINGLE BOND)H distance. The linear Pd3 singlet and triplet states capture outside of the Pd3 and break the H(SINGLE BOND)H bond. © 1997 John Wiley & Sons, Inc.
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    Total and partial decay widths in vibrational predissociation of the HeI2 van der Waals complex for lower initial vibrational excitations (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 89-96 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We presented a calculation of the total and partial decay widths of vibrational predissociation (VP) of the HeI2 molecule for low initial vibrational excitations from the lowest van der Waals (vdW) state with total angular momentum J = 0. A time-dependent golden rule wave-packet method was employed in our numerical calculations for the decay widths. The computed total decay widths, lifetimes, and rates of VP are in fairly good agreement with those extrapolated from the experimental data available. Predicted total decay widths as a function of initial vibrational levels exhibit a highly nonlinear behavior. These results demonstrate that a quantum mechanical decay mode for low vibrational excitation remains as well. The total propagation time needed in the time-dependent golden rule wave-packet calculations is much shorter than is the lifetime of the predissociation of HeI2. It is shown that the final-state interaction between the fragments is important for determining the final rotational-state distribution (partial decay width). We find that the major peak position in the final rotational-state distribution shifts to lower rotational energy levels with increase of the initial vibrational quantum number, which is evidently different from that for higher vibrational levels. This fact can be clearly explained by the dependence of the amount of kinetic energy released to the product degrees of freedom on the initial vibrational state. © 1997 John Wiley & Sons, Inc.
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    Enantiospecific Synthesis of 2,5-Disubstituted Piperidine Derivatives: Synthesis of (+)-Pseudoconhydrine (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1267-1272 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Enantiospecific synthesis ; Chiral building blocks ; 2,5-Disubstituted piperidines ; (+)-Pseudoconhydrine ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel methodology for the synthesis of any one of the four stereoisomers of a 2,5-disubstituted piperidine in optically pure form is described, starting from readily available chiral building blocks 10 and 11 (or their antipodes). The utility of this approach is demonstrated in the total synthesis of (+)-pseudoconhydrine hydrochloride, the structure of which was confirmed by X-ray analysis.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/jlac.199719970633
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    Biotransformation of Ergot Alkaloids by Haloperoxidase from Streptomyces aureofaciens: Stereoselective Acetoxylation and Propionoxylation (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2379-2383 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Enzyme catalysis ; Oxidases ; Peroxides ; Acylations ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Agroclavine (1) was oxidized, by haloperoxidase from Streptomyces aureofaciens, to 2,3-dihydro-6,8-dimethyl-3β-acetoxy-8-ergolen-2-one (2) in the presence of sodium acetate and bromine ions. Acetate was incorporated into the above product during oxidation. In a propionate buffer, incorporation of propionate into the product was observed, yielding 2,3-dihydro-6,8-dimethyl-3β-propionoxy-8-ergolen-2-one (4). The biotransformation proceeded faster in the propionate buffer, affording also the higher oxidation product (4aS),(10bS)-7-amino-3,4,4a,5,6,10b-hexahydro-2,4-dimethyl-6-oxobenzo[f]quinoline (3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971129
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  • 46
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    Synthesis of rac-Midpacamide and the spiro-Cyclization of Its Precursor (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1525-1528 
    Details
    ISSN: 0947-3440
    Keywords: Alkaloids ; Biomimetic synthesis ; spiro-Cyclization ; Marine sponges ; Natural products ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The alkylidene hydantoin 8 was synthesized as an analogue of the marine natural product oroidin (1) by employing a Horner-Wadsworth-Emmons reaction. Treatment of 8 with bromine in acetic acid induced a biomimetic spiro-cyclization forming the ACD ring system of dibromophakellin (2) in one step. rac-Midpacamide (10) was obtained from the same precursor through a chemoselective, ruthenium-catalyzed hydrogenation leaving the brominated pyrrole moiety intact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970731
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  • 47
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    Chemistry of Opium Alkaloids, XLIIIPart XLII. M. de Grauw, E. F. Muller, R. H. Woudenberg, L. Maat, Recl. Trav. Chim. Pays-Bas 1996, 115, 58. - A PM3 Computational Approach to the Selectivity in the Diels-Alder Reactions of Thebaine and Analogues with Methyl Propenoate (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 13-19 
    Details
    ISSN: 0947-3440
    Keywords: 6-Demethoxythebaine ; Ethenoisomorphinans ; Ethenomorphinans ; Calculations, semiempirical ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Geometrically fully-optimized transition structures are calculated for the Diels-Alder adducts of methyl propenoate and the 3-demethoxy derivatives of the dienes thebaine, 6-demethoxythebaine, 5β-methylthebaine, and 5β-methyl-6-demethoxythebaine using the semiempirical PM3 method. The number of calculated forms is limited according to a search of the conformational space of methyl propenoate and of the dienes. The lengths of the incipient bonds in the transition structures vary from 2.0 to 2.4 Å, but the average value of the lengths of these two bonds in the same structure is much more constant: 2.18 ± 0.02 Å. The effects of the methoxycarbonyl group and of the 6-methoxy group on the lengths of the incipient bonds are in agreement with the relative magnitudes of the frontier orbital coefficients. Comparison of the energetic data with experimental results shows that the prediction of the stereo- and regioselectivities from the Gibbs energy of activation differences is good as far as it concerns the main products. The absence of minor products and the formation of the remarkably large amount of 8β-ethoxycarbonyl-6β,14β-ethenomorphinan from 5β-methyl-6-demethoxythebaine does not follow from the calculations.
    Additional Material: 6 Tab.
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    URL: http://dx.doi.org/10.1002/jlac.199719970105
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  • 48
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    Synthese und Konformation von Hexahydro-isochino[1,2-b][3]benzazepinen (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 447-457 
    Details
    ISSN: 0947-3440
    Keywords: Isoquino[1,2-b][3]benzazepines ; Iso-C-homoberbines ; Conformation analysis ; Bischler-Napieralski reaction ; Methyl ∊-hydroxycarboxylates ; Heterocycles ; Alkaloids ; Drug research ; Medicinal chemistry ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Conformation of Hexahydro-isoquino[1.2.-b][3]benzazepinesThe synthesis of the six hexahydro-isoquino[1,2-b][3]benzazepines 13a-f is described; their conformation is investigated by NMR spectroscopic methods, X-ray analysis and dehydrogenation with mercury(II) acetate.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970225
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    Dihydrocolchicine 8,12-Endoperoxide: A Novel Starting Material for Convenient Syntheses of the Allocolchicinoids N-Acetylcolchinol O-Methyl Ether and Androbiphenyline (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 2275-2279 
    Details
    ISSN: 0947-3440
    Keywords: Semisynthetic colchicine analogues ; Endoperoxide transformations ; Colchicine-allocolchicine rearrangement ; Axial chirality ; Biaryls ; Alkaloids ; Colchicum autumnale ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Optically pure dihydrocolchicine-8,12-endoperoxide 2 is used as the starting material for the synthesis of some bioactive allocolchicinoids. Depending on the reaction conditions and reagents employed, different modifications of the C ring of colchicine (1) are achieved. Triphenylphosphane deoxygenation of 2 leads to the well known N-acetylcolchinol O-methyl ether (NCME, 6, 40% yield from 1). Treatment of the endoperoxide 2 with CH3OH/CH2Cl2/silica gel provides the plant alkaloid androbiphenyline (11) in a yield of 60% from 1. Triethylamine-catalysed transformation of 2 yields (-)-colchicine-8,12-dione (12) (17% yield), together with a mixture of interconverting tetracyclic hemiketals 8a and 8b. For the formation of the allo colchicinoids 6 and 11 plausible reaction pathways are suggested. In contrast to what is found in the literature, the assignment of the absolute configuration of natural (-)-colchicine (1), and the allo-congeners 6 and 11, should be (M,7S) or (aR,7S) instead of (aS,7S).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719971115
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  • 50
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    Solanum Alkaloids, 139 - Photolysis of N-Chlorospirosolanes (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1589-1592 
    Details
    ISSN: 0947-3440
    Keywords: Photolysis ; N-Chlorospirosolanes, photolysis of ; 23-Chloro- and 23,23-dichlorospirosolanes ; Steroids ; Alkaloids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: UV irradiation of N-chlorosoladulcidine (2) in trifluoroacetic acid, followed by separation and hydrolysis of the obtained 3-O-trifluoroacetates affords (23R)-23-chlorosoladulcidine (5) and 23,23-dichlorosoladulcidine (7). Similar treatment of N-chlorotomatidine (9) affords 23,23-dichloro-22-isotomatidine (12).
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/jlac.199719970741
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    Resonances and antibound states in a Morse potential (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 239-244 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We calculate the resonant and antibound state energies for a Morse potential with a centrifugal barrier using Siegert boundary conditions. Starting with a complex wave number k (purely imaginary for bound and antibound states), we integrate numerically from the origin up to a matching point using Numerov's method. The inward integration is performed using the corresponding (first-order) Riccati equation. The complex eigenvalues are found by matching the two logarithmic derivatives. We find narrow shape resonances within the well, above the dissociation limit, and broad resonances above the centrifugal barrier. Antibound states are found even with J = 0. © 1997 John Wiley & Sons, Inc.
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    A study of methanetetraol dehydration to carbonic acid (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 62 (1997), S. 315-322 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two alternative dehydration reactions C(OH)4 → (HO)2CO + H2O and C(OH)4 + H2O → (HO)2CO + 2H2O are studied by ab initio Becke3LYP/6-311 + G** and MP2/6-31G** methods. Calculated energy and geometry characteristics of intermediates and transition states predict a catalytic effect of one water molecule and the exothermism of the transformations. Relevant HF/6-311 + G**, HF/6-31G**, HF/6-31G, and HF/3-21G calculations were performed for comparison. © 1997 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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    Generalized relativistic effective core potential: Gaussian expansions of potentials and pseudospinors for atoms Hg through Rn (1997)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 63 (1997), S. 1107-1122 
    Details
    ISSN: 0020-7608
    Keywords: relativistic pseudopotentials ; heavy atoms ; method of molecular calculation ; electronic structure ; Gaussian approximation ; Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Gaussian expansions of the generalized relativistic effective core potential (GRECP) components are reported for elements Hg through Rn. The accuracy of the analytical GRECPs is estimated by calculations of atomic transition energies with the numerical one-configurational wave functions in comparison with Dirac-Fock calculations. The results of the corresponding calculations with the RECPs of other groups are also given. An “averaged error” in the reproduction of the transition energies without the change of the occupation number of the 5d-shell is an order of magnitude smaller than that for the RECPs of other groups. As is demonstrated for the transitions with the change of the occupation number of the 5d-shell in mercury, the largest absolute error of the GRECP is only 1.5-2 times smaller than that of the energy-adjusted pseudopotential (PP) or the RECP of Ross et al. with the same space of explicitly treated electrons. However, the dispersion of these errors is 19⋅10-4 au for the energy-adjusted PP, 35⋅10-4 au for the RECP of Ross et al. and only 4⋅10-4 au for the GRECP. One-configurational spin-averaged calculations of the molecular properties for HgH and HgH+ are carried out and compared with the corresponding results of Häussermann et al.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 1107-1122, 1997
    Additional Material: 17 Tab.
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    Asymmetric Catalysis, 105Part 104: Ref.. Stereoselective Hydrogenation of Folic Acid with Immobilized Optically Active Rhodium(I)/Diphosphane Catalysts (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 55-62 
    Details
    ISSN: 0009-2940
    Keywords: Diastereoselective hydrogenation ; Folic acid ; Immobilized optically active rhodium(I)/diphosphane catalysts ; Leucovorin ; HPLC analysis of 5-formyltetrahydrofolic acid derivatives ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: For the hydrogenation of the C=N bonds in the pyrazine ring of the vitamin folic acid (1) optically active rhodium(I)/diphosphane complexes immobilized on supports such as silica gel or Al2O3 were used. The reduction was carried out at 50 bar hydrogen pressure in an aqueous solution buffered to pH 7. Thus, 5,6,7,8-tetrahydrofolic acid (2) was obtained which contains a new asymmetric center at C-6 of the pterine system. Therefore, in combination with the (S) configuration of the natural L-glutamic acid part of the molecule two diastereomers with (6S,S) and (6R,S) configuration arise. The relatively unstable tetrahydrofolic acid (2) was converted into its 5-formyl derivative folinic acid (4) by treatment with methyl formate/formic acid in a 5:1 mixture of DMSO/pyridine. The Ca salt of folinic acid (4) is the widely used drug leucovorin. The diastereomers were separated by silica gel HPLC. To the column bovine serum albumine (BSA) is covalently bound. With optically active rhodium(I)/diphosphane catalysts, immobilized on silica gel supports, a diastereoselectivity of up to 90% could be achieved in the hydrogenation of folic acid (1).
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300109
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    Conformational Mobility and Preferences of Allyl-Type Organometallic Intermediates: Dodec-2-enylpotassium (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 83-88 
    Details
    ISSN: 0009-2940
    Keywords: Torsional (Z/E) isomerization ; Selectivity, regio- and stereo- ; Allylsilanes ; Allylic oxidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Alk-2-enylpotassium compounds having the endo conformation are synthetically very valuable precursors of (Z)-olefinic derivatives substituted at the outward allylic position. They may be generated by „stereoconservative‘ metalation of the readily available (Z)-alk-2-enes by using the superbasic mixture of butyllithium and potassium tert-butoxide or by metalation under similar conditions of stereorandom mixtures of alk-2-enes or alk-1-enes followed by torsional isomerization of the concomitantly formed exo conformers to the thermodynamically more stable endo species. The principal factors that dictate the rate and the extent of the endo/exo equilibration are the substrate geometry, the solvent, the temperature, the reagent stoichiometry, and catalysis.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19971300113
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    Organophosphorus Compounds, 114. Tetracyclic Phosphorus-Aluminium-Carbon Compounds - Synthesis by Cooligomerization of Kinetically Stabilized Phosphaalkynes with Trialkylaluminium CompoundsDedicated to Professor Michael Hanack on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 255-259 
    Details
    ISSN: 0009-2940
    Keywords: Phosphaalkynes ; Triorganoaluminium compounds ; Cooligomerization ; Cage compounds ; Aluminium compounds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When the trialkylaluminium reagents 5 are allowed to react with phosphaalkynes 4 in n-pentane, a highly selective phosphaalkyne cyclotrimerization with incorporation of two organometallic units occurs (→ 6). The tetracyclooctane derivatives 6a-e represent the first examples of phosphorus-aluminium-carbon cage compounds. The polycyclic products 6 are able to function as ligands in transition-metal complexes (→ 7), which is illustrated by the reactions of 6b, c with nonacarbonyldiiron and pentacarbonyl(tetrahydrofuran)tungsten, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300219
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    On the Ligating Properties of Sulfonate and Perchlorate Anions Towards Zinc (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 283-289 
    Details
    ISSN: 0009-2940
    Keywords: Zinc ; Sulfonate ligands ; Perchlorates ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Attempts are reported to incorporate sulfonate and perchlorate anions as ligands in zinc complexes of tripodal ligands. Using tris(benzimidazolylmethyl)amine (BIMA) only the aqua complexes [ (BIMA)Zn-OH2](RSO3)(ClO4) and [(BIMA)Zn-OH2](RSO3)2(R=CH3, CF3, p-tolyl) were accessible. Using substituted pyrazolylborates (Tp*), the same three sulfonate anions were found to be ligands in the complexes Tp*Zn-OSO2R. Spectroscopic evidence for perchlorate coordination in Tp*ZnClO4 · 2 DMSO conflicts with crystallograpic evidence against it in Tp*ZnClO4 · pyridine. The crystal structures of [(BIMA)Zn-OH2](CH3SO3)2, TpCum,MeZn-OS02CH3, TPtBu,MeZn-OSO2C6H4-p-CH3, and [TpCum,MeZn · NC5H5]ClO4 were determined.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300223
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    Multiple Bonds Between Main-Group Elements and Transition Metals, CLXIV. Alkylrhenium(VI) Oxides-Synthesis and Characterization (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 295-298 
    Details
    ISSN: 0009-2940
    Keywords: Rhenium ; Oxides ; Alkyl ligands ; Dirhenium compounds ; Metal-metal interactions ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Most alkylrhenium(VII) oxides, e.g. ((cyclo)-C3H5)Re03 (2) are rather sensitive to temperature and moisture with the prominent exception of methyltrioxorhenium (1). The corresponding alkylrhenium(VI) oxides of formula [RR′(O)- Re(μ-O)]2 [R=R′=(cyclo)-C3H5 (3), iPr (4); R=CH3, R′=C2H5 (5), R=CH3, R′=iPr (6)] are much more stable in this regard. They can be handled in air at room temperature. They were synthesized from Re207 and dialkylzinc precursors, fully characterized and are available in much higher yields than their ReVII congeners. Mixed tetraalkyltetraoxodirhenium(VI) complexes (R # R′) synthesized from 1 and dialkylzinc compounds form as a mixture of cis/trans isomers. They are oily liquids at room temperature. The Re=O and Re-Re stretching force constants as a measure of the bond strengths, were determined from IR and Raman data.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300225
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    Heterobimetallic Complexes with a Propynylidene C3-Bridge: General Synthetic Routes to Bimetallic Ethynylcarbene Complexes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 479-488 
    Details
    ISSN: 0009-2940
    Keywords: Heterobimetallic complexes ; Carbene complexes ; Alkynes ; Coupling reaction ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sequential reaction of the dimethylamino(trimethylsilylethylnyl)carbene complexes [(CO)5M'=C(NMe2)C≡CSiMe3] [M' = W (1a)] with KF/THFMeOH, nBuLi and transition metal halides, [XMLn], affords heterobimetallic propynyliden complexes of the type [(CO)5M'=C(N-Me2)C≡CMLn] [MLn = Ni(PPh3) Cp (4a, b). Ni(PMe2Ph)2- {Mes) (Mes=2,4,6-C6H2Me3) (5a), Rh(CO)(PPh3)2 (6a), Fe(CO)2Cp (7a,b)]. In contrast, reaction of 1a with MeLi · LiBr and [IFe(CO)2Cp] yields the novel N-metallated complex [(CO)5W=C{N(ME)Fe(CO)2Cp}C≡CSiMe3] (8a). The complexes [(CO)5M'=C(NMe2)C≡CMLn=Fe(CO)2Cp (7a, b), Ru(CO)2Cp (10a,b), Ru(CO)(PPh3)Cp (11a), Mn(CO)5 (12a), Re(CO)5 (13a)] are accessible by Pd-catalyzed coupling of the C-stannylated carbene complexes [(CO)5M'=C-(NMe2)C≡CSnBu3] (9a, b) with [XMLn]. The related monomethylaminocarbene complexes [(CO)5M'=C(NHMe)C≡ CSnBu3] (16a, b), obtained by stannylation of [(C))5M'=C(NHMe)C=CH] (15a, B) with Bu3SnNEt2, react with [IFe(CO)2Cp] to give the bimetallic complexes [(CO)5M'=C(NHMe)C≡CFe(CO)2Cp] (17a, b). The complexes 4a, 5a, 7a and 10a were characterized by X-ray structural analysis. The spectroscopic and structural data suggest that the two metal centers in 4-7, 10-13, and 17 interact only weakly.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300407
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    Diazosulfonate Substitutents: A Route to Transition-Metal Complexes with Switchable Water Solubility (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 515-520 
    Details
    ISSN: 0009-2940
    Keywords: Water-soluble ligands ; Diazo compounds ; Photolysis ; Cleavage reactions ; Zinc ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The single-crystal X-ray structure analysis of the diazosulfonate p-H2N-C6H4-N=N-SO3Na 3 features a Z configuration of the diazo moiety and a nitrogen-sulfur bond. Each sodium atom is coordinated by one diazosulfonate substitutent in a chelating manner. Upon reaction of 3 with excess salicylaldehyde, the highly water-soluble Schiff base ligand 6 is obtained in good yield. Treatment of ZnCl2 with 2 equiv. of 6 gives the zinc complex 7. In all cases, the solubilizing diazosulfonate groups can be cleaved off photolytically, which offers an opportunity to precipitate the molecules from their aqueous solutions.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300411
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    Organoamido- and Aryloxolanthanoids, 15Part 14: Ref. [1a].. Organometallic Compounds of the Lanthanoids, 116Part 115: Ref. [1b].. Syntheses of Low Coordination Number Divalent Lanthanoid Organoamide Complexes, and the X-ray Crystal Structures of Bis[(N-2,6-diisopropylphenyl)(N-trimethylsilyl)amido]bi(tetrahydrofuran)samarium(II)and -ytterbium(II) (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 409-415 
    Details
    ISSN: 0009-2940
    Keywords: Mercury ; Lanthanides ; Lanthanoid(II) complexes ; (N-2,6-Diisopropylphenyl)(N-trimethylsily)amide complexes ; Bis(trimethylsilyl)amide complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mercury(II) amide complex Hg[N(SiMe3)(2,6-iPr2C6H3)]2 (1) was prepared by reaction of HgBr2 with Li[N(SiMe3) 2,6-iPr2C6H3)] in diethyl ether solvent. Redox transmetallation reactions of 1 with elemental samarium, europium or ytterbium in THF solvent (THF = tetrahydrofuran), generated the novel divalent complexes Ln[N(SiMe3)(2,6-iPr2C6H3]2(THF)2 with Ln = Sm (2), Eu (3) and Yb (4). 4 was also synthesized by reaction of elemental ytterbium, HgPh2 and HN(SiMe3)(2,6-Me3)2]2(THF)2 [Ln = Sm (5), Yb (6)] by reaction of the metals with HgPh2 and HN(SiMe3)2. Thermal desolvation of 4 under high vacuum gave Yb(N)(SiMe3)2,6-iPr2C6H3)]2 (THF) (7), whereas under identical conditions 6 yielded the solvent-free complex [Yb[N{SiMe3)2]2]2. (8). The new compounds 1-4 and 7 are hydrocarbon soluble and 171Yb-NMR spectra were recorded for 4, 6, 7 and 8. X-ray crystal structure determinations of 2 and 4 revealed four-coordinate, distorted tetrahedral metal environments augmented by weak Ln…ipso-C(aryl) interactions.
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    URL: http://dx.doi.org/10.1002/cber.19971300316
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    Recent Developments in the Chemistry of Covalent Azides (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 443-452 
    Details
    ISSN: 0009-2940
    Keywords: Ab initio calculations ; Azides ; Density functional calculations ; Covalent azides ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The experimental and theoretical chemistry of covalently bound azides is an area that has seen considerable renaissance over the past 10 years. This review is not exhaustive in scope but rather focuses on and highlights certain aspects in this field. In particular, the stability and dissociation of HN3 is discussed at a very high level of theory (CASSCF and MCSCF-CI) and compared and contrasted with experimental data and results from „medium“-level ab initio computations (MP2, B-LYP). From these results credence is given to those values calculated for larger systems and heavy elements for which very high level computations are not possible. The experimentally well-characterized covalent halogen azides (XN3, where X = F, Cl, Br, I) as well as the heavy-element group-15 compound Sb(N3)3 are discussed. The review also includes discussion of the bond properties of the highly unstable N-bound azides ON-N3 and (FSO2)2N-N3. In the final chapter attention is drawn to the recently predicted and eventually experimentally verified elusive species OCN-NCO, which is isoelectronic to the hitherto unknown diazide N6.
    Additional Material: 11 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300403
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    Divalent Tin and Lead Compounds EX2 Acting as Bridging Ligands in [{(CO)5M}2EX2]2- (E = Sn, Pb; M = Cr, Mo, W): Preparation and PropertiesDedicated to Professor G. E. Herberich on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 687-699 
    Details
    ISSN: 0009-2940
    Keywords: Tin ; Lead ; 119Sn NMR ; Salt metathesis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of Na2[M2(CO) 10] (M = Cr, Mo, W) with SnHal2 (Hal = Cl, Br) is a well established procedure for the synthesis of anions of type A, [{(CO)5M)SnHal3]-. Conditions are described which, for the same type of procedure, result in the additional formation of dianions of type B, [{(CO)5M}2SnHal2]2-. Procedures for separating these two types of anions in the form of their stable [Ph4P]+ or [nBu4N]+ salts by appropriate salt metathesis are presented. The structures of theses species have been characterized by X-ray analysis of three salts containing type A anions and two salts containing type B anions. The reactivity of the type B salts containing the bulky cations [Ph4P]+ or [nBu4N]+, respectively, is remarkably low; the salts are, however, transformed into highly reactive sodium salts by further metathesis with Na[BPh4]. In such salts the halide substitutents are easily exchanged as shown by the synthesis of ]})CO(5Cr}2oxinato]- (4)- from [Na-(THF)x]2[{(CO)5Cr}2SnCl2] and sodium 8-oxoquinolate, Na[C9H6NO]. The structure of the anion, 4 is compared to the structure of [[(CO)5Cr)SnCl2· THF] and sodium 8-oxochinolate. The preparation of the dinuclear anions [{(CO)5Cr}2E(OOCCH3)2]2- (E = Sn, 2g; E = Pb, 3) is accomplished by the reaction of [Ph4P]2[Cr2(CO)10] with the corresponding acetates E(OOCCH3)2. While 2g and 3 are formal analogues of the type-B anions, their structures reveal an asymmetrical η2-coordination of the two acetato ligands, in each case ending up in a 4+2 coordination for the main group centres, instead of the four-coordination observed for [{(CO)5M}2SnHal2]2-, All compounds have been characterized by usual spetroscopic and analytical techniques. X-ray analyses have been performed for selected examples. 119Sn-NMR data are presented for all of the compounds which contain tin-centred ligands.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300604
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    Organophosphorus Compounds, 118Part 2: 117: Ref1. Reactions of 1-Chloro-1H-phosphirenes with Nucleophiles (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 711-723 
    Details
    ISSN: 0009-2940
    Keywords: Phosphorus heterocycles ; 1H-Phosphirenes ; Nucleophilic substitution reactions at 1H-phosphirenes ; Metal-complexation of functionalized 1H-phosphirenes ; Carbonyl complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The halogen atoms in the 1-chloro-1H-phosphirenes, 5a-c, are easily substituted on reaction with organolithium and Grignard reagents, 14a-p, with formation of the corresponding O-, N-, C-, Si-, and Ge-substituted 1H-phosphirenes, 15a-t. C1/H exchange reactions also occur on reaction with lithium metal hydrides (5a → 17). Furthermore, substitution reactions are also realized with the alkali metal borates, 18a-g (→19a-g); the same is true for reactions with trimethylsilyl cyanide and azide (→22a-d). Some of the substitution products have been characterized in the form of their metal complexes, 16, 23, 24, and 25.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19971300607
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    Synthesis of Germatranyl Derivatives of Esters of Carboxylic Acids via Organometallic (Si, Ge, Sn) Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 739-746 
    Details
    ISSN: 0009-2940
    Keywords: Germatranes ; Organotrihalogenogermanes ; Organometallic (Si, Ge, Sn) reagents ; Transmetallation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Trialkylstannyl esters of tris(2-hydroxyalkyl)amines, N(CH2CHROSnAlk3)3 (9-11 (R = H, Me; Alk = Et, Bu), react with X3GeC(R1)(R2)COOR3 (12-17) (X = Cl or Br; R1, R2=H, Me, Ph, SiMe3, COOEt; R3=Me, Et) to give esters of α-germatranylcarboxylic acids, N(CH2CHRO)3GeC(R1)(R2)-COOR3 (1-8), in high yields. The synthesis of esters 12-17 is reported. Esters of α-germatranyldiphenylacetic acid 24 and 25 can be obtained by treatment of diphenylketene with Et3SnOMe to give in situ Et3SnC(Ph2)COOMe (23), followed by reaction with GeCl4 to give in situ Cl3GeC(Ph2)COOMe (22 and further reactions with 9 or 11, respectively. Reduction of germatrane 6 with LiAlH4 in diethyl ether leads to cleavage of the germanium-carbon bond with subsequent formation of (2-hydroxyethyl)trimethylsilane. The crystal structures of 3, 6 and 7 are reported. 1-Acyloxygermatranes 26 and 27 are obtained by treatment of 1-methoxygermatrane (28) with diphenyl- and dichloroacetic acid, respectively.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300611
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    Base-Induced Synthesis of a Tetrastannatriazabicyclo[3.1.1]heptane from Tris)dimethylchlorostannyl)amineDedicated to Professor W. Sieber on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 765-769 
    Details
    ISSN: 0009-2940
    Keywords: Tin - Nitrogen cage compounds ; Sn—X—Sn intramolecular bridges ; Distannylamine pyridine adduct ; Tin ; Moessbauer spectroscopy ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tris(dimethylchlorostannyl)amine (2a) reacts with pyridine in a 3:4 molar ratio to produce the tin-nitrogen containing bicyclo[3.1.1]heptane (3) with elimination of the adduct Me2SnCl2·2 py. Treatment of the distannylamine 2,6-[Pr2H3N(SnMe2Cl)2 (4) with pyridine, however, leads to the formation of the 1:1 pyridine adduct 4 and this can be regarded as a model to explain the route to 3. The molecular structures of 3 and 5 were determined by multinuclear magnetic resonance spectroscopy in solution, as well as by X-ray structure analysis of their crystals. Typical structural features for both compounds are intramolecular Sn—X—Sn bridges. Support for the structures comes from MS fragmentation patterns, IR spectra, and the Mössbauer spectra.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300615
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    Thermal Reactions of 5-Alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-Phosphapyrazolines) - A Route to Various P—Heterocycles and to 2-PhosphabutadienesDedicated to Professor M. Hanack on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 779-788 
    Details
    ISSN: 0009-2940
    Keywords: 1,2,4-Diazaphospholes ; Phosphiranes, alkylidene- ; 2-Phosphabutadienes ; Phosphorus heterocycles ; pyrazolines, thermolysis ; Rearrangements ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 5-alkylidene-4,5-dihydro-3H-1,2,4(λ3)-diazaphospholes (4-phosphapyrazolines) are thermally much more stable than related compounds without the exocyclic double bond. Thermolysis reactions typically occur in the range 110-150°C in toluene solution, and different, mostly competing, reaction pathways are observed. Thermal extrusion of nitrogen from 8a-g gives rise to β-phosphanaylsiloxyalkenes 10, benzo[c]-phosphole derivatives 11, 14 and 115, (β-siloxyalkylidene)-Phosphiranes 12, and dihydro-1,3-oxaphospholes 13. The thermolysis of 5-alkylidene-4,5-dihydro-4-trimethylsilyl-3-trimethylsilyloxy-3H-1,2,4-dizaphospholes 17 afforded three products, including the highly substituted and stable 2-phosphabutadienes 18 formed by nitrogen extrusion and rearrangement. Finally, the 4-chloro-3-trimethylsilyloxy-substituted heterocycle 21 was transformed at 170°C into 4H-1,2,4-diazaphosphole 23. The structures of 13c and 18a were determined by single-crystal X-ray diffraction.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300617
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    N-Alkylation of Ammine - Undecahydro-Closo-dodecaborate(1-)Dedicate to Prof. Dr. Walter Siebert on the occasion of hbis 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 795-799 
    Details
    ISSN: 0009-2940
    Keywords: Boron ; Alkylations ; N ligands ; Dodecaborate ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of the ammine-undecahydro-closo-dodecaborate(1-) anion with alkyl halides have been studied in detail. The degree of alkylation of the nitrogen was found to be dependent upon the steric demands of the alkyl groups. The derivatives were characterized by NMR and infrared spectroscopy. Four compounds were crystallized for single crystal X-ray diffraction studies. The tetrahedral coordination of the nitrogen atom of the bis-alkylated derivatives was found to deviate towards planarity with increasing steric hindrance of the substitutents. - The syntheses, crystal structures, and spectral properties of four N-alkyl derivatives of [H3N—B12H11]-, ammine - undecahydro-closo-dodecaborate(1-) (3), are reported. Alkylation of 3 with ethyl iodide was achieved in dimethyl sulfoxide using potassium hydroxide as base. This led to orthorhombic crystals of [N(nC4H94][(CH3CH2)3N—B12H11] (4). The reaction of 3 with benzyl chloride resulted in the bisbenzylated product, isolated as triclinic crystals of [PPN][(C6H5CH2)2 NH—B12H11] (5). The alkylation of 3 with 2-bromopropane gave a mixture of the mono- and bisalkylated products. The monoalkylated derivative [PPN][(CH3)2CH)NH2-12H11] (6, crystallized in the triclinic space group p1) and the bisalkylated product [PPN]{[(CH3)2NH—B12H11) (7, monoclinic, P21./c) were separated on the basis of their different water solubilities. The solid-state structures of the compounds 4-7 revealed a slight distortion of the B12 icosahedron. The length of the B(1)-N(1) bond was found to be dependent on the steric requirements of the attached amine, e.g. primary amine 〈 secondary amine 〈 tertiary amine. This is demonstrated by the variation in the B—N bond length; from 157.8(2) pm for 6, 158.5(5) pjm for 5, 160.0(3) pm for 7, to 163.7(6) pm for 4.
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    URL: http://dx.doi.org/10.1002/cber.19971300619
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    Unusual Ring-Closure Reactions During the Oxidation of 1,1′-Bi(3-methylphosphol-2-ene) with Hexafluoroacetone  -  Formation of a Tricyclic Fluorine-Containing PhosphoraneDedicated to Professor Rudolf Taube on the occasion of hbis 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 819-822 
    Details
    ISSN: 0009-2940
    Keywords: Hexafluoroacetone ; Phosphorus, pentacoordinated ; Diphosphane diselenide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduction of the isoprene - PCl3 adduct 1 with magnesium powder, or with Si2Cl6, furnished P-chloro-3-methyl-phosphol-2-ene, 2, in satisfactory yield. Further reduction of 2 with Si2Cl6 gave the new trichlorosilyl-3-methylphosphol-2-ene, 3. The reaction of 2 with magnesium powder, with 3, or with 1/2 equivalent of Si2Cl6 provided the new γ3P-γP-diphosphane 1,1′-bi(3-methylphosphol-2-ene) 4. Reduction of 4 with Si2Cl6 led to 3. Oxidation of 4 with selenium gave the 1,2-diphosphane diselenide, 5. The oxidation of 4 with hexafluoroacetone led to a mixture of products, from which a novel tricyclic phosphorane 6 was separated. the structure of 196 was determined by X-ray diffraction; the coordination geometry at phosphorus in distorted trigonal bipyramidal, with a very long equatorial P - C(CF3)2 bond of 193.2(2) pm.
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    URL: http://dx.doi.org/10.1002/cber.19971300623
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    Organophosphorus Compounds, 119Part 118: Ref.. The Phosphaalkyne Cyclotetramer System  -  Syntheses, Valence Isomerizations, and Reactions (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 823-834 
    Details
    ISSN: 0009-2940
    Keywords: Phosphaalkynes ; Phosphaalkyne cyclotetramers ; Cage compounds ; Valence isomerization ; Cyclotetramerization ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In contrast to their all-carbon analogues, phosphaalkyne cyclooligomers only became accessible a few years ago. A milestone in the chemistry of cyclotetramers was the synthesis and structural characterization of the tetraphosphacubane 5, obtained as a thermolysis product of tert-butylphosphaacetylene (1). Since then, the construction of eleven cyclotetramers has been achieved, covering seven different frameworks (A-G). As a consequence of the use of kinetically stabilized phosphaalkynes as starting materials, all known cyclotetramers bear sterically demanding substituents (tert-butyl, tert-pentyl, 1-adamantyl). Cyclotetramerizations are not only achieved by thermolysis of 1, but also by alternative and selective routes such as transition-metal-mediated, Lewis acid- and base-induced processes, as well as by cycloadditions to phosphaalkyne cyclotrimers. Interestingly, these tetramers can be interconverted by various valence isomerizations. The results of thermal and photochemically-induced rearrangements are in good agreement with MO calculations carried out for the parent compounds. Phosphaalkyne cyclotetramers exhibit a highly interesting reactivity and other peculiar features. One outstanding example is the tetraphosphacubane 5, which shows unusual structural and spectroscopic properties as a result of its unique bonding arrangement.
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    URL: http://dx.doi.org/10.1002/cber.19971300703
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    2-Phosphanylphosphinines as Bridging Ligands for Dinuclear Transition Metal Carbonyls (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 843-849 
    Details
    ISSN: 0009-2940
    Keywords: P ligands ; Phosphorus heterocycles ; 2-Phosphanylphosphinines ; Dinuclear complexes ; Metal carbonyls ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2-phosphanyl-4,5-dimethylphosphinines 1-5 are powerful bridging ligands able to stabilize metal-metal single and triple bonds between low-valent transition metal centres. Their reaction with Mn2(CO)10 in refluxing xylene yields the corresponding Mn2(CO)8 complexes 6 and 7. Reaction with [Fe2Cp2(CO)4] under UV irradiation similarly yields the Fe-Fe-bridged Fe2Cp2(CO)2 complexes 8 and 9. An additional observation is that the 2-phosphininyl-3,4-dimethylphosphaferrocene 10 is formed upon reaction of the 2-phospholylphosphinine 5 with [Fe2Cp2(CO)4] at high temperature under CO pressure. A clean addition occurs at the Mo≡Mo triple bond of [Mo2Cp2(CO)4] to give the Mo-Mo single-bonded complexes 11-15. The thermolysis of these complexes succeeds when the phosphanyl group is a phosphonite P(OEt)2 (13) or P(OAr)2 (14), affording cleanly the Mo2Cp2(CO)4 triple-bonded complexes 16 and 17, respectively. The metal-metal triple bonds of these complexes readily add two molecules of CO to reform 13 and 14, or one molecule of tBu-N≡C to give 18 and 19. The X-ray crystal structure analysis of the MO2C2(CO)4 complex 13a, with the 2-P(OEt)2- phosphinine, shows a gauche orientation of the two Cp rings and very short P-Mo bonds of 2.3565(4) and 2.406(2) Å to the phosphinine and P(OEt)2 groups, respectively.
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    URL: http://dx.doi.org/10.1002/cber.19971300706
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    On the Polymorphism of White PhosphorusDedicated to Professor Gottfried Huttner on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1235-1240 
    Details
    ISSN: 0009-2940
    Keywords: Phosphorus ; Phase transitions ; Molecular crystal ; Crystal growth ; Low-temperature crystal structure ; Librational motion ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: White phosphorus occurs in three modifications. The α form, which exists at roomtemperature, transforms reversibly to the β form at -77°C. The α · β transformation may be strongly delayed. Quenching the α form to -185°C followed by slow warming results in an exothermic reactions with formation of the γ form which transforms into the β form at -120°C in an endothermic reaction. A transition β · γ is not observed. The γ form is characterized by its powder diagram. The structure of the β form is redetermined from a single crystal at -185°C (P., α = 547.88(5), b = 1078.62(11), c = 1096.16(11)pm, α= 94.285(8), β = 99.695(7), γ = 100.680(7)., V = 623.79(10) · 106 pm3, Z = 6 formula units per cell). The P4 molecules exhibit pronounced librational motion in spite of the low temperature of investigation. The arrangement of the centers of the tetrahedra corresponds to the atom positions in the γ-plutonium structure, which is discussed in relation to the bcc structure.
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    Chiral Polysiloxane-Fixed Metal 1,3-Diketonates (Chirasil-Metals) as Catalytic Lewis Acids for a Hetero Diels-Alder Reaction -Inversion of Enantioselectivity Upon Catalyst -Polymer Binding (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 879-885 
    Details
    ISSN: 0009-2940
    Keywords: Asymmetric catalysis ; Cycloadditions ; Lewis acids ; Polymers ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A dimethylpolysiloxane chain is covalently bound to the monomeric Lewis acid catalyst (1R)-(+)-oxovanadium(1V) bis[3- heptafluorobutanoylcamphorate] [(+)-5a] at the C-10 position of the camphor moiety yielding the novel chiral polymeric (1S)-( +)-oxovanadium(1V) bis[3-heptafluorobutanoylcamphorate] -dimethylpolysiloxane [( +)-6a][1]. The Lewis acid promoted hetero Diels-Alder reaction of trans-l-methoxy-3-(trimethylsilyloxy)- 1,3-butadiene (1) and benzaldehyde (2) is studied in the presence of the enantiomerically pure monomeric (5a, 5b) and polymeric (6a, 6b) catalysts. The monomeric and polymeric catalysts of identical chirality[1] invoke opposite enantioselectivities toward the formation of 2-phenyl- 2,3-dihydro-4H-pyrone (4). This remarkable result is corroborated by numerous control experiments. Thus, it is demonstrated that the environment of the active site of the catalyst is changed when the complex is fixed to a polymeric chain. In contrast to 5 and 6, the monomeric 12 and polymeric 13 europium(III) tris[3-heptafluorobutanoylcamphorates] of identical chirality invoke the same enantioselectivity toward the formation of 4. The concept of polymer attachment is utilized to recover the catalyst from the reaction mixture by precipitation and to recycle it for subsequent catalytic runs.
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    Cp3Zr(acetonitrile)+: Structure of an Electron-Rich Organometallic d0-Cation (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 899-902 
    Details
    ISSN: 0009-2940
    Keywords: Cp3Zr complexes ; Cationic organometallic Lewis acid ; d0-Configured metal complex ; Acetonitrile ; crystal structure analysis of Zirconium ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The organometallic salt [Cp3Zr(N≡C-CH3)]+ [CH3B-(C6F5)3]- (3a) has been prepared by treatment of Cp3ZrCH3 with B(C6F5)3 followed by the addition of acetonitrile. X-ray crystal structure analysis of 3a shows that its cation consists of three uniformly coordinated η5-cyclopentadienyl ligands about the zirconium atom. The acetonitrile ligand is end-on coordinated. In the linear [Zr] -N≡C-CH3 unit the C≡N triple bond [N-C2 1.126(5) Å] is slightly shorter than in the free acetonitrile molecule [dC≡N = 1.141(2) Å], the structure of which was determined as a reference by X-ray diffraction of a crystal obtained by IR-laser-induced zone melting on the diffractometer.
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    URL: http://dx.doi.org/10.1002/cber.19971300714
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  • 75
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    Benzophenoneimine Complexes of Copper(1)Dedicated to Professor J. Strähle on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 947-950 
    Details
    ISSN: 0009-2940
    Keywords: Copper ; N ligands ; Copper(I) complexes ; (Imine)copper(I) complexes ; Ketimines ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of [(MeCN)4Cu]BF4 with two or three equivalents of benzophenoneimine lead to the formation of [(Ph2C=NH)2]BF4 (1) and [ (Ph2C=NH)3Cu]BF4 (2), respectively. A further equivalent of the ligand does not coordinate to the cation of complex 2. The crystal structures of both compounds were determined. 1 shows a linearly two-coordinated copper(I) center with a Cu-N distance of 1.877(2) Å. In compound 2 a distorted trigonal planar coordination of copper is observed with N-Cu-N angles of 114.5(2), 112.9(2) and 132.4(2)°, corresponding to two nearly equal Cu-N distances [Cu-N2 1.947(5) and Cu-N3 1.934(5) Å] dnd a significantly longer third one (Cu-N1 2.011(5) Å]. A comparison of these data with recently determined structures of bis(benzophenoneimine)silver(I) and -gold(I) complexes shows that the covalent radii of the monovalent coinage metals decrease in the order Ag(I) 〉 Au(I) 〉 Cu(I).
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300721
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    Organoantimony Oxides: Preparation and Crystal Structures of [(2-PhOC6H4)O (C6H4)2Sb]2O2 and (o-Tol2Sb)4O6Dedicated to Prof. Dr. Gottfried Huttner on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 959-961 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Air oxidation of (Oxydi-2,1-phenylene)(2-phenoxyphenyl)stibane (1) gives the phenoxystibane oxide [(2-PhOC6H4)O(C6H4)2Sb]2O2 (2). Single crystals of (o-Tol2Sb)4- O4(O2)2 (3) were obtained by air oxidation of o-TolSb-(SiMe3)2. Crystal structures of 2 and 3 are reported.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300724
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  • 77
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    Zinc Pyrazolylborate Complexes with Phenoxide and Alkoxide LigandsDedicated to Professor Wolfgang Beck on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 975-980 
    Details
    ISSN: 0009-2940
    Keywords: Zinc complexes ; Phenoxide complexes ; Alkoxide complexes ; Terminal alkoxide ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The zinc hydroxide complexes Tp*Zn-OH of highly substituted pyrazolylborate ligands react with phenols, and alcohols, of sufficient acidity, in a condensation reaction with release of H2O. Starting with phenols the following were attached:phenolate, p-nitropehnolate, o-vanillinate, o-hydroxymethylphenolate, o,o-bis(hydroxymethyl) -p-methylphenolate. Whilst aliphatic alcohols and benzyl alcohol did not react, their derivatives, with highly electronegative substituents could be incorporated. Thus, the arylmethoxides OCH2C6F5 and OCH2C6H4NO2-p, as well as the alkoxides OCH2CF3 and OCH2CCl3, were attached. 2-Mercaptoethanol was bound via its thiolate function. The crystal structures of TpCum,Me ZN-OC6H4NO2-p,TpCum,Me ZN-OCH2-C6F5, TpCum,Me ZN-OCH2CF3, TpCum,Me ZN-OCH2CCl3 and TpCum,MeZn-SCH2CH2OH were determined.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300727
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  • 78
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    Pseudoelement Compounds, XPart IX: Ref. Synthesis and Crystal Structure of New Complexes of the Type trans-[Pt(H)X(PPh3)2 with Cyanamide and Cyanomethanide LigandsDedicated to Professor S. Engels on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1007-1012 
    Details
    ISSN: 0009-2940
    Keywords: Platinum ; Nitrocyanamide ; Nitrosodicyanomethanide ; 1,1,3, 3-Tetracyano-2-azapropenide ; 1,1,2,3,3-Pentacyanopropenide ; Hydrido complexes ; Coordination modes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The new coordination compounds trans-[Pt(H)X(PPh3)2] with NCN- and C(CN)2-functionalized anions (X- = [N(O)C(CN)2]-, [NO2NCN]-, [N{C(CN)2}2]-, [NCC{C-(CN)2}2]-, have been characterized by 1H-, 31P-, 13C-NMR, and IR spectroscopy and elemental analyses the crystal structures of trans-[Pt(H)N(O)C(CN)2(PPh3)2], trans- [Pt(H)N{C(CN)2}2(PPh3)2], and trans-[Pt(H)NCC{C(CN)2}2-(PPh3)2) have been determined by X-ray diffraction. Remarkably, [N(O)C(CN)2]- is coordinated through the central nitrogen atom, while [N{C(CN)2}2]- and [NCC(C(CN)2]2]- are bonded through terminal nitrogen atoms of a C(CN)2 unit.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300730
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  • 79
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    New Coupling Reactions and Phosphorylations Using Organozinc Reagents (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1021-1027 
    Details
    ISSN: 0009-2940
    Keywords: Zinc ; Chirality ; Cross-coupling ; Phosphorylations ; Catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This Microreview on the chemistry of organozinc reagents starts by briefly showing the methods of preparation of organozinc compounds and then discusses the considerable synthetic utility of zinc organometallics for the formation of new carbon-carbon bonds in the presence of transition-metal catalysts. Finally, the use of organozinc chemistry for the preparation of polyfunctional and chiral phosphanes is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300802
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  • 80
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    Synthesis and Structures of Bis(tetramethylipiperidino)aluminum Halides-X-ray Crystal Structures of tmp2AlX (X = Cl, Br, I) and [tmp2A1(μ-F)l2 (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1047-1052 
    Details
    ISSN: 0009-2940
    Keywords: Bis(tetramethylipiperidino)aluminum halides ; Alkoxy((tetramethylpiperidino)aluminum halides ; 27Al-NMR spectra ; Aluminum ; Amides ; Synthetic methods ; Bridging ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Lithio-2,2,6,6-tetramethylpiperidine [Li(tmp)] reacts with AlX3 (X = Cl, Br) in diethyl ether/ n-hexane solution to generate the products of substitution and ether cleavage, [tmpAl(X)(μ-OEt)], (la, X = Cl; 1b, X = Br). However, when the reaction is allowed to proceed in n-hexane alone, an almost quantitative yield of compounds tmp2AlX (2a, X = Cl; 2b, X = Br; 2c, X = I) is obtained. According to 27AI-NMR spectroscopy, mass spectroscopy, cryoscopy, and X-ray crystal structure determinations, these compounds are monomeric in the solid state, in solution, and in the gas phase. 2b reacts with AgBF4 yielding the fluoride-bridged dimer (tmp2AlF), 2d, as shown by X-ray crystal structure determination.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300805
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  • 81
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    Structure and Reactivity of Sodium Phenoxide - Following the Course of the Kolbe-Schmitt Reaction (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1461-1465 
    Details
    ISSN: 0009-2940
    Keywords: Kolbe-Schmitt reaction ; Solid-state structures ; Sodium phenoxide ; Solvent Complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent-free sodium phenoxide (NaOPh) crystallises as a polymer and forms a polymeric chain in the [0 0 1] direction. The low coordination of the sodium atoms, as evident in the crystal structure, is confirmed by the easy coordination of oxoligands (α-donors). Hence, the four-membered ring chain of the solvent-free sodium phenoxide is separated by oxoligands, and forms partial structures as the polymer fragments. Thus, NaOPh crystallises in THF with the formation of an Na6O6 core, consisting of two face-fused heterocubes, and in N, N, N′, N′-tetramethyl urea (TMU) with the formation of a Na4O4 heterocubane. The solvent-free NaOPh-CO2 complex obtained from the addition of CO2 to a solution of sodium phenoxide is, when exposed to a temperature of 80°C, subject to an irreversible phase transition, as demonstrated by FT-IR and DTA studies. The complex formed at 80°C is, apparently, another intermediate of the Kolbe-Schmitt reaction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301017
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    1,8-Bis(phosphanyl)naphthalenes: 1,8-Bis[(diethylamino)phosphanyl]-naphthalene, 1,8-Bis(dichlorophosphany)naphthalene, and 1, 3-Dichloro-2,-3-dihydro-1,3-dioxo-2-oxa-1,3-diphosphaphenaleneDedicated to Professor Huns Burger on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1485-1489 
    Details
    ISSN: 0009-2940
    Keywords: Naphthalenes ; Phosphanes ; Phosphorus heterocycles ; Protecting groups ; Strained molecules ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1.8-dilithionaphthalene 1 reacted with bis(dimethylamino)-chlorophosphane to form 1,8-bis[(diethylamino)phosphanyl]-naphthalene 2, whose structure was confirmed by X-ray crystal structure analysis; there are two independent molecules, in which the P(NEt2)2 groups adopt an eclipsed conformation. Reaction of 2 with gaseous HCl gave in low yield 1,8-bis-(dichlorophosphanyl)naphthalene 3, which was characterized by 1H- and 31P-NMR spectroscopy, mass spectrometry and elemental analysis. Attempted recrystallization of 3 led to oxidative hydrolysis which furnished 4, an anhydride of a bis(chlorophosphonic acid), whose structure was elucidated by X-ray crystal structure analysis. The geometry of 4 reveals a relief of strain from the bis (aminophosphane) 2; the naphthalene groups are less distorted and the P atoms are displaced less far from the naphthalene best plane.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301021
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    Coordination Compounds of Coinage Metals with Vinylidenebis(diphenyl-phosphane) and Its Disulfide and Their Reactivity towards NucleophilesDedicated to Professor P. Royo on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1513-1517 
    Details
    ISSN: 0009-2940
    Keywords: Gold ; Silver ; Diphosphane ; Diphosphane Disulfide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vinylidenebis(diphenylphosphane) reacts with gold(I) or gold(III) compounds to give dinuclear {[{Au(C6F5)]2[(PPh2)2C=CH2{] or [Au{PPh2C(=CH2)Ph2P)]2(ClO4)2] or mononuclear complexes ([Au(C6F5)3(PPh2C(=CH2)Ph2P)]}, respectively. The latter reacts with gold(I) or silver(I) compounds to afford dinuclear [[Au(C6F5)3[PPh2C(=CH2)Ph2P}AuX], X=Cl or C6F5) or trinuclear species {[{Au(C6F5)3{PPh2C(=CH2)Ph2P{]2M]ClO4, M=Au or Ag}. No addition of nucleophiles to the C=C double bond is observed in these complexes, which contain the diphosphane acting as bridging or monodentate ligand. (SPPh2)2C=CH2 reacts with AgClO4 to give [Ag{SPPh2C(=CH2)Ph2PS}]2-(ClO4)2or[Ag[PPh2C(=CH2)Ph2P]2]ClO4. The crystal structure of [Au(C6F5)3{PPh2C(=CH2)Ph2P}Au(C6F5)] has been established by X-ray crystallography, and confirms the expected square planar and linear geometry for the Au111 and Au1 centres, respectively.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301026
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  • 84
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    Diastereoselective Synthesis and Molecular Structure of a Bicyclic and a Cage Phosphane (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1547-1550 
    Details
    ISSN: 0009-2940
    Keywords: Phosphane ; 1,3α., 5,7β-Tetrakis(trifluoromethyl)-6,-9-dioxa-2-phosphabicyclo[3.3.1]nonane-3β, 7α-diol ; 1,7-Trifluoromethyl-3,5-methyl1-2,4.8-trioxa-6-phosphaadamantane ; Phosphorus heterocycles ; Ketones ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A two-step formal insertion of 1,1,1,5,5,5-hexafluoro- (2a) and 1,111-trifluoropentane-2,4-dione (2b) into the P-H bonds of phosphane gave the primary a-hydroxyphosphanes 3 and 4, precursors for the resulting secondary phosphanes, 6,9-dioxa-2-phosphabicyclo[3.3.l]nonane (6a) and 2,4,8-trioxa-6-phosphaadamantane (7), both formed diastereospecifically. The molecular structures of 6a and 7 were established by single-crystal X-ray structure analysis which revealed two independent molecules for 6a in the unit cell possessing a chair-boat conformation with a C-P-C angle of 95.4(2)°, and a characteristic heteroadamantane geometry for 7, with the corresponding angle being smaller by 4.9°.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301031
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  • 85
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    Reactions of Complex Ligands, LXXVII. Axial-Chiral Metal Carbenes: Synthesis and Structure of 1,1-Binaphthyl-Derived Carbonyl-Carbene Complexes of Chromium (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1605-1609 
    Details
    ISSN: 0009-2940
    Keywords: Axial-chiral complexes ; Biaryls ; Carbene complexes ; Circular dichroism ; Chromium complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Axial-chiral mono- and biscarbene complexes of chromium containing the 1,1-binaphthyl skeleton have been obtained in both racemic and enantiopure forms in a one-pot reaction starting from lithiated 2,2-dimethoxy-1,1-binaphthyl (1) and hexacarbonyl chromium via the Fischer route. An X-ray structure analysis of the biscarbene complex 2 reveals that the biscarbene functionalization significantly increases the dihedral angle defined by the biaryl planes. The enantiopure complexes have been characterized by CD spectroscopy.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301108
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    Evidence for Internal Ion Pair Formation upon Insertion of Reactive Alkene in the Zirconium-Carbon Bond of the cp2Zr(μ-C4h6)b(c6f5)3 Metallocene-Boron-Betaine Ziegler Catalyst System (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1261-1267 
    Details
    ISSN: 0009-2940
    Keywords: Single-component metallocene catalyst ; Olefin insertion ; Organometallic ions pairs ; (Alkene)metallocene complex ; Metallocene betaines ; C-C coupling ; Zirconium ; Homogeneous catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of the (butadiene)ML2 complexes 1 [ML2 = Cp2Zr (a), Cp2Hf (b), and (.-C5H4CH3)2Zr (c)] with B(C6F5)3 gives the 1:1 addition products (CH2CHCHCH2-B(C6F5_3)ML2 (3a-c). At -40°C the betaine complex 3a inserts one equivalent of methylenecyclopropane to give the regioisomeric insertion products 5a and 6a in a 60:40 ratio. These products exhibit the cyclopropylidene moiety in the α- and β-positions, respectively, relative to zirconium. The corresponding hafnocene complexes 5b and 6b are obtained in a 70:30 ratio starting from 3b. The reaction of 3(a-c) with allene gives a single insertion product (7a-c) in each case where the exo-methylene group is in the α-position to the metal center ([2,1]-insertion). The complexes 5-7 are chiral. They all exhibit a pronounced ·-interaction of the internal -C4H=C5H- double bond of the s̰-ligand chain with the metal center in addition to a metallocene/-C6H2-[B] ion pair interaction. The relative contributions of the cationic metallocene end of the dipolar complexes 5-7 are quite dependent on the steric and electronic properties of the respective metallocene units involved. This is revealed by a comparison to typical 13C-NMR parameters of the complexes 5-7 with a pair of suitable model complexes, namely the ethylene insertion product 4 into the betaine system 3a and its THF adduct 4.THF.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/cber.19971300914
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    Tripod Ligands Containing a Mixed P/N/S Doner Set: Synthesis and Coordination Chemistry (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1279-1294 
    Details
    ISSN: 0009-2940
    Keywords: Tripodal ligands ; Aminolytic cleavage of oxetanes ; Tripod molybdenum compounds ; Mixed donor set ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of neopentane-based tripod ligands CH3C(CH2X)(CH2Y)(CH2Z( 3 (X = NR2, NHR; Y = PR2; Z = PR2, SR, S-) in a convergent manner is described. The procedure is based on the aminolytic cleavage of functionalized oxetanes CH3C(CH2OCH2)CH2R 1 by primary or secondary amines, leading to functionalized amino alcohols CH3C(CH2NHR)(CH2OH)(CH2R) or CH3C(CH2NR2)-(CH2OH)(CH2R) 2. The appropriate activation of the R (e.g. OR) and OH groups present in 2 allows for substitution vs. SR or PR2 donor functions. Depending on the nature of the groups present in each reaction step, various protection and groups present in each reaction step, various protection and deprotection steps have to be taken in the course of this type of preparation of the tripod ligands 3. By reaction with (CH3CN)3Mo(CO)3, ligands 3 form Mo(CO)4 derivatives 4 or Mo(CO)3 derivatives 5, depending on the reaction conditions. In compounds 4, the ligands are coordinated in a bidentate mode with the soft donor atoms (P, S) coordinated and the hard donor function playing the role of the dangling arm. In the trihapto bonding mode present in 5, all three donor functions, two soft (P, S) and one hard (NHR′, NR′2), are coordinated. The two types of coordination compounds may be interconverted: 4e (X = NMe2′ Y = PPh2, Z = SiPr) with a non-coordinating CH2NMe2 group is transformed into 5c upon photolytic decarbonylation. Under 1 bar CO at 20°C, 5c reverts to 4e. X-ray structure analysis of a series of compounds of types 4 and 5 reveals characteristics of the relevant conformational patterns. All compounds have been fully characterized by the standard analytical techniques (NMR, MS), as well as elemental analysis.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300917
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    Neutral Gold(I) Complexes with Mixed Phosphorus LigandsDedicated to Professor Wolfgang Beck on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1333-1338 
    Details
    ISSN: 0009-2940
    Keywords: Gold ; Gold(I) complexes ; Phosphinite complexes ; Phosphite complexes ; Configuration determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of compounds (R3P) AuMe with diphenylphosphinous acid Ph2P(O)H affords methane and neutral complexes of the type (R3P(O)Ph2 (1a: R = Me; 1b: R = Ph, lc: R = o-Tol). 1a, b are obtained in high yield, but the yield of lc is lower owing to a side-reaction which leads to a different product: Ph2P(OH)-Au-P(O)Ph2 (2). The crystal structure of 1a was determined by a single-crystal X-ray diffraction study. The compounds is a monomer with a linear P-Au-P′ axis and the phosphane and phosphinite ligands in a staggered conformation. In solution (CHCl3, CH2Cl 2/) compounds 1a-c undergo a ligand redistribution, establishing equilibria that involve ionic isomers of the type [R3P)2Au]+ [Au-(P(O)Ph2)2]-, which are readily identified through their NMR data. The analogous reaction of (R3P)b AuMe with dimethylphosphite (MeO)2P(O)H gives methane and the corresponding dimethylphosphites of the type (R3P)AuP(O)(OMe)2 (3a: R = Me; 3b: R = Ph; 3c: R= o-Tol). The crystal structure of 3b has also been determined. It features a linear structure with an eclipsed conformation of the ligands. In polar solvents (CHCl3, methanol) there is again an eqilibrium between neutral and ionic isomers, the latter comprising bis(phosphane)gold cations [(R3P)2Au]+ and {Au[P(O)-(OMe)2]2)- anions, as confirmed by NMR spectroscopy and mass spectrometry.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/cber.19971300925
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    Regioselective Complexation of New Multiple Piperazine/Pyridine Ligands: Differentiation by 113Cd-NMR Spectroscopy (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1353-1359 
    Details
    ISSN: 0009-2940
    Keywords: 113Cd NMR ; Multidentate ligand ; Multinuclear metal complex ; Piperazine ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eleven novel piperazine containing open-chain ligands L1-L11 were designed to offer symmetrical and asymmetrical complexation sites for metal ions and were synthesized by repetitive synthetic method. The divergent use of aromatic bishalomethyl and mono-N-alkylated piperazine compounds as spaces led toa series of long (up to M. W. = 836) oligomeric multidentate N-ligands. Due to the lack of solid state methods for structure analysis, an NMR technique using 113 Cd nucleus as a probe in solution state was utilised. 113 Cd chemical shifts were observed to be dependend on the coordination site and similar coordination sites in different ligands gave characteristically similar 113 Cd chemical shifts. As a result 113 Cd-NMR spectroscopy proved to be an excellent tool to distinguish between the structures of the different complexation sites on a nearly quantitative level.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300929
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    Design of Self-Adapting N-Heteroaromatic Substituted Claw Ligands as E-/M+(E = P-Block Element, M = Main-Group Metal) Charge Spacers (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1365-1374 
    Details
    ISSN: 0009-2940
    Keywords: N ligands ; Chelates ; Coordination modes ; Ligand effects ; Structure-activity relationships ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monoanionic bi- and tridentate ligand systems emulating the structural features of the well-known poly(pyrazolyl)borates are created by bridging heteroaromatic rings with formally negatively charged p-block elements. Their properties and versatility are exemplified by their complexes with main group metals. Due to their N(σ)-donating and π-interacting ability, as well as the flexibility of the substituent bonding, these ligand systems have the potential to adapt both geometrically and electronically to the coordination requirements of the complexed metal. Within these complexes, the heteroaromatic substituents operate as charge spacers between the formally anionic center and the metal cation without encapsulating either site. This provides possible applications in the creation of reactive soft/hard bimetallic reagents, the realization of multinuclear arrays, and the design of preorganized CVD precursors, particularly en route to III/V-semiconducting thin films.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301004
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  • 91
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    Electronic Resource
    Cyclic and Bicyclic Poly(phosphane)borane Cations (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1411-1416 
    Details
    ISSN: 0009-2940
    Keywords: Phosphane-boranes ; Boranes ; Phosphanes ; Umpolung, attempted ; Bond polarity ; Configuration determination ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of (Me2S)BH2Br and (Me2S)BHBr2 with equimolar quantities of 1,2-bis(diphenylphosphanyl)ethene (1) or -benzene (2) lead to cyclic, cationic bis(phosphane)boranes [4[(1)BH2]+ Br-; 6: [(2)BH2]+ Br; 7: [(2)BHBr]+ Br-]. The Br counterions can be exchanged in metathesis reactions (e.g. with AgBF4 to afford 4a). The tritertiary phosphane bis[2-(diphenylphosphanyl)phenyl]phenyl-phosphane (3), reacts with (Me2S)BHBr2 to give bicyclic dicationic tris(phosphane)borane 8, [(3)BH]2+ Br-, which can be converted into the bis(hexafluorophosphate) 8a using NH4PF6. All compounds have been characterized by analytical and NMR-spectroscopic data. The crystal and molecular structures of 5 - 7 have been determined by single-crystal X-ray diffraction. The five-membered rings C2P2B have an envelope conformation and show no sign of electron delocalization. Attempts to deprotonate the B—H functions in 5 - 8 have not been successful. Clearly, the two (5 - 7) or three phosphonium centers (8) adjacent to the boron atom are not sufficient to induce an “umpolung” of the B—H group
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301009
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  • 92
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    Electronic Resource
    Reactivity of the Heavier Group-13 Monochlorides [{CH(SiMe3)2}2AlCl], InCl, TlCl, and of the Elements Ga and Hg Towards the Unsupported Ni-Ni Bond of [{(η5-Cp)Ni(PEt3)}2]  -  A Straightforward Synthetic Approach to the Synthesis of Mixed Main-Group/Transition-Metal Clusters Containing Unsupported Metal-Metal BondsDedicated to Prof. Dr. G Hutter on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1433-1440 
    Details
    ISSN: 0009-2940
    Keywords: Metal - metal bonds ; Insertion reactions ; Group-13 monochlorides ; Main-group elements ; Nickel ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dinuclear compound [{(η5 - Cp)Ni(PEt3)}2] (1) containing an unbridged Ni-Ni bond reacts with the heavier group 13 monochlorides [{CH(SiMe3)2)2}AlIIICl], InCl, and TlCl by scission of the metal-metal bond. In the case of InCl and TlCl the chloro-bridged dimmers [{(η5-Cp)Ni(PEt3)2ECl2Ecl}2] (E = In 2, Tl 5) were formed. The Tl compound 5 is unstable and decomposes via disproportionation a and formation of the halogen-free Tl [III] compound [{(η5-Cp)Ni(PEt3)}3Tl] (6). 2 can be dehalogenated with activated magnesium to yield the halogen-free In [III] compund [{(η5-Cp}Ni(PEt3)}3In] (4). The Ga analogue of 4 and 6 [{(η5-Cp)Ni(PEt3)}3Ga] (7) is accessible by a conproportionation of 1 with Ga metal in refluxing THF. In contrast to InCl and TlCl the aluminium (III) monochloride [{CH(SiMe3)2}2AlCl] reacts with 1 by a ligand redistribution reaction and formation of the salt [{(η5-Cp)Ni(PEt3)2]+-[{CH(SiMe3)2]2AlCl]2-. (8). Elemental Hg or Mg amalgam show the same activity as elemental Ga towards 1 and insert into the Ni—Ni bond by forming the linear Hg-bridged complex [(n3-Cp)Ni(PEt3)]2Hg] (9). The molecular structures of 2, 4, 8, and 9 were determined by X-ray crystallography. The In atom in 4 has a distorted trigonal-planar configuration with the central In atom being surrounded by three [(n5-Cp)Ni(PEt3)] fragments. 4 represents the first Ni-In cluster containing exclusively unsupported In - Ni bonds, as well as the first carbonyl-free Ni - In cluster. On the basis of spectroscopic data the same structure is assigned to the Ga and Tl analogues of 4. The Ni—Hg—Ni arrangement in 9 is exactly linear, as determined by X-ray crystallography.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301013
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  • 93
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    Hydrocarbon-Bridged Complexes, XL. Polyene-Bridged Iridium(III), Palladium(II), and Platinum(II) Complexes of Schiff Bases from α,ω-Polyene Dialdehydes and α-Amino Acids or o-AminophenolDedicated to Professor Dieter Seebach on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1467-1473 
    Details
    ISSN: 0009-2940
    Keywords: Schiff bases ; Polyene dialdehydes ; α-Amino acids ; Pantamethylcyclopentadienyl complexes ; P ligands ; Iridium ; Palladium ; Platinum ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Schiff bases 1—11 were synthesized from α-amino acids or o-aminophenol and crocetindialdehyde, 2,7-dimethyloctatrienedial, terephthalaldehyde, or β,β′ -p-phenylendiacroleine. The reactions of these Schiff bases with chloro-bridged complexes [(R3P)(Cl)M(η-Cl)]2 (M = Pd, Pt) and [(C5Me5)(Cl)Ir(°Cl)]2 gave the dinuclear complexes 12-31.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301018
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  • 94
    Electronic Resource
    Electronic Resource
    Enantioselective Catalysis. New Chiral Expanded Phosphanes Derived from Substituted Deltacyclenes (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1495-1498 
    Details
    ISSN: 0009-2940
    Keywords: Deltacyclenes ; Deltacyclanes ; P-H addition reactions ; Chiral phosphanes ; Enantioselective catalysis ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The suitability of enantiomerically pure deltacyclenes as building blocks in the synthesis of expanded phosphanes was examined. Different substituted deltacyclenes were irradiated with diphenylphosphane and three bisphosphanyl derivatives. With these P—H addition reactions, new chiral deltacyclane-derived phosphorus ligands were synthesized. They were tested in the Rh-catalyzed asymmetric hydrogenation of (Z)-(ã)-N-acetamidocinnamic acid and in the Pd-catalyzed asymmetric allylation of 1,5-dimethylbarbituric acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301023
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  • 95
    Electronic Resource
    Electronic Resource
    Masthead (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997) 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300101
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  • 96
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    Photochemical reactions of transition metal organyl complexes with olefins, 17Part 16: Ref.. Light-Induced [6+2] Cycloadditions of Dienes to Tricarbonyl(η6-1,3,5,7-cyclooctatetraene)chromium(0) (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 9-12 
    Details
    ISSN: 0009-2940
    Keywords: Chromium ; Chromium(0) complexes ; Cyclooctatetraene complexes ; Photochemistry ; Cycloadditions ; Photochemical [6+2] cycloadditions ; Dienes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tricarbonyl(η6-1,3,5,7-cyclooctatetraene)chromium (1) yields upon UV irradiation in ether at 233 K with 2,3-dimethyl-1,3-butadiene (2) or 2-methyl-1,3-butadiene (3) by [6+2] cycloadditions the correspondingly substituted tricarbonyl(η6-bicyclo[4.2.2]deca-2,4,7-triene)chromium complexes 4, 5a and 5b. With ammonium cerium(IV) nitrate the organic ligand of complex 4, 9-isopropenyl-9-methyl-bicyclo[4.2.2]-deca-2,4,7-triene (6) is liberated. The complexes 4, 5a and 5b were characterised by IR and NMR spectroscopy, the ligand 6 by NMR spectroscopy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300103
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  • 97
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    A Structural Study of Selenobenzamides: Crystal Structures and Dynamic 13C NMR (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 49-54 
    Details
    ISSN: 0009-2940
    Keywords: 4-(p-Bromoselenobenzoyl)morpholine ; 4-[(p-(Dimethylamino)selenobenzoyl]morpholine ; Hindered rotation ; Hammett treatment ; Selenoamides ; Amides ; Selenium compounds ; Structure elucidation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The solid-state structures of (p-bromoselenobenzoyl)morpholine (2a) and [p-(dimethylamino)selenobenzoyl]morpholine (2b) were determined by X-ray diffraction. Both molecules show a flat selenoamide group. The larger contribution of resonance stabilization by the aromatic ring carrying the p-dimethylamino substituent is reflected by the smaller interplanar angle Θ between the aromatic ring and the selenoamide group [53.3(1)° vs. 81.1(1)°] and by the shorter length of the C=Se bond [1.824(5) Å vs. 1.840(3) Å]. The Gibbs free energy of activation of C-N bond rotation (ΔG≠rot) of five p-substituted (selenobenzoyl)morpholines was determined by dynamic 13C NMR. The activation barriers were found to range from 61.6 kJ/mol (X = NNMe2) to 75.1 kJ/mol (X = H). The ΔG≠rot values of the corresponding (thiobenzoyl)morpholines were found to be from 3.2 kJ/mol (X = NMe2) to 5.0 kJ/mol (X = H) lower. In both cases, ΔG≠rot showed an excellent linear Hammett correlation with s̰+p.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300108
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  • 98
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    Synthesis and Characterization of Substituted Benzyl Zinc Derivatives - Molecular Structures of (tmeda) Li-CH (GeMe3)Ph, (tmeda)Zn(CH2Ph)2, (tmeda)Zn[CH(SiMe3)Ph]2, and (tmeda)Zn[CH(SiMe3)Ph]N(H)Si(SiMe3)3Dedicated to Professor Manfred Weidenbruch on the occasion of his 60th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1499-1505 
    Details
    ISSN: 0009-2940
    Keywords: Lithium ; Zine ; Dibenzylzinc ; Tmeda complexes ; Heteroleptic alkylzinc amide ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of lithium phenyl(trimethylsilyl)methanide with phenyl(trimethylsilyl)methylzinc chloride-tmeda in the presence of tmeda yields the addition product, a bis(tmeda)-lithium dialkylchlorozincate. The elimination of lithium chloride leads to the formation of a tmeda adduct of bis[phenyl-(trimethylsilyl)methyl]zinc. The metathesis reaction of phenyl(trimethylsilyl)methylzinc chloride-tmeda with lithium tris(trimethylsilyl)silylamide allows the isolation of the corresponding heteroleptic tmeda complex of an alkylzinc amide. The metalation of phenyl(trimethylstannyl)methane with butyllithium yields the transmetalation product benzyllithium. From the metathesis reaction of this lithium base with anhydrous zinc(II) chloride in the presence of tmeda, the tmeda adduct of dibenzylzinc crystallizes. The molecular structures of (tmeda)Li—CH(GeMe3)Ph, (tmeda)Zn(CH2Ph)2, (tmeda)Zn[CH(SiMe3)Ph]2, and (tmeda)Zn[CH(SiMe3)-Ph[N(H)Si(SiMe3)3 are reported. Whereas lithium bonds in an η3-fashion, the zinc atom forms a σ(Zn—C) bond. The extremely wide Zn—N—Si angle in (tmeda)Zn[CH(SiMe3)-Ph[N(H)Si(SiMe3)3 of 157° is remarkable.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301024
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  • 99
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    Unusual Dinuclear Hydridorhodium(III) Complexes Containing Bulky Phosphanyl(stibanyl)methanes as Chelating LigandsDedicated to Professor Luigi Venanzi on the occasion of his 70th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1529-1531 
    Details
    ISSN: 0009-2940
    Keywords: Rhodium ; Chelate complexes ; Hydrido complexes ; Bridging ligands ; P Ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mononuclear starting materials [Rh(η4-C8H12)(k2-P,Sb-iPr2PCH2SbR2)]PF6 (la, b) react with CF3CO2H in the presence of H2 to give the dinuclear hydridorhodium(II1) complexes [{RhH(k2-P,Sb-iPr2PCH2SbR2)]PF6 (2a, b) in almost quantitative yield. The X-ray crystal structural analysis of 2b (R = tBu) reveals a distorted octahedral geometry around the two metal centers with the two phosphanyl(stibanyl)methanes in a chelating and the two trifluoracetate ligands in a bridging coordination mode.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301028
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  • 100
    Electronic Resource
    Electronic Resource
    X-ray and Solution Structure of Inosine 5' -Monophosphate Coordinated to (Ethylenediamine)palladium(II).  - the Importance of Intramolecular Hydrogen Bonding (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1551-1555 
    Details
    ISSN: 0009-2940
    Keywords: Antitumor agents ; Nucleotides ; Palladium ; Hydrogen bonds ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The compound [Pd(en)(5′-IMP-N7)2].11 H2O, where 5′-IMP = inosine 5′-monophosphate, crystallizes in the tetragonal space group P4322 with the unit cell parameters: a = b = 12.060(5) and c = 28.510(5) Å, V = 4147(3) Å3, Z = 4. A head-to-tail orientation with A configuration is observed for the nucleotides which are coordinated through the N(7) positions such that d[Pd-N(7)] = 2.053(8) Å. The sugar moieties exhibit anti orientations toward the purine bases while their pukkers adopt C(3)′-endo conformation. The overall conformation about the phosphate backbone is gauche+. Intramolecular hydrogen bonding is observed between the phosphates and the NH groups of the en ligand with a donor-acceptor distance of 2.88 Å. The coordination mode of the solid-state structure is shown to be identical to that observed by 1H-NMR spectroscopy in solution under slightly acidic conditions, where the N (l) positions of the nucleotides are protonated. The results are discussed in reference to closely related systems reported in the literature with emphasis on the importance of hydrogen bonding in such complexes.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301032
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