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  • 1995-1999  (644)
  • 1998  (644)
  • General Chemistry  (643)
  • Nuclear reactions
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Space science reviews 84 (1998), S. 199-206 
    ISSN: 1572-9672
    Keywords: Nuclear reactions ; Nucleosynthesis ; Abundances ; Stars:Evolution ; Interior ; Rotation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We first recall the observational and theoretical facts that constitute the so-called 3He problem. We then review the chemical anomalies that could be related to the destruction of 3He in red giants stars. We show how a simple consistent mechanism can lead to the destruction of 3He in low mass stars and simultaneously account for the low 12C/13C ratios and low lithium abundances observed in giant stars of different populations. This process should both naturally account for the recent measurements of 3He/H in galactic HII regions and allow for high values of 3He observed in some planetary nebulae. We propose a simple statistical estimation of the fraction of stars that may be affected by this process.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 15-24 
    ISSN: 1434-1948
    Keywords: Chromium ; Organometallics ; Homogeneous catalysis ; Olefin polymerization ; Polyethylene ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chromium-based heterogeneous catalysts are used extensively for the polymerization of olefins. There are few homogeneous model systems that allow investigation of the reaction mechanisms and unique characteristics of chromium catalysts. Coordinatively unsaturated paramagnetic chromium alkyls containing a Cp*CrIIIR fragment (Cp* = η5-C5Me5, pentamethylcyclopentadienyl) catalyze the polymerization of ethylene and α-olefins. Correlations between molecular structure and catalytic activity are reviewed.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 25-27 
    ISSN: 1434-1948
    Keywords: Bite angle ; Catalysis ; P ligands ; Palladium ; Allylic alkylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the natural bite angle (βn) of diphosphane ligands on catalyst selectivity and activity in the palladium-catalyzed allylic alkylation was investigated. The selectivity and rate of the reaction are mainly determined by steric hindrance induced by the diphosphane ligands. The steric hindrance at the palladium center increases as the natural bite angle of the ligand becomes larger. This results in an increasing selectivity at larger bite angles, but at very large bite angles the rate of the reaction drops. The ligand with the largest calculated bite angle, Xantphos, induced 100% selectivity but the reaction rate became low.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 29-35 
    ISSN: 1434-1948
    Keywords: Catalysis ; Palladium ; C-C coupling ; Metallacycles ; Trisubstituted olefins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coupling reaction of 1,1-disubstituted olefins (α-methylstyrene, n-butyl methacrylate) with various aryl bromides (Heck reaction) has been studied as a new concept to synthesize trisubstituted olefins. Surprisingly, the nature of the base dramatically influences the product distribution. Thus, a systematic investigation on the role of base in Heck reactions of 1,1-disubstituted olefins was performed. Less coordinating bases like NaOAc, NaOBz or Na2CO3 yield a statistical distribution of regioisomers with the terminal olefin 10 as the major product. However, by using amines like Bu3N or diisopropylethylamine (DIPEA) as base internal olefins can be synthesized with high selectivities. With phosphapalladacycle 3 as catalyst precursor, we were able to obtain catalyst turnover numbers up to 1000, while Pd(OAc)2/2PPh3 was one order of magnitude less active. Analysis of the reaction profile by kinetic investigations led to the postulation of a reduction and subsequent oxidative addition of the catalyst precursor 3 to form 12 as catalytically active intermediate.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 43-54 
    ISSN: 1434-1948
    Keywords: Asymmetric catalysis ; Allylic alkylation ; 1,5-Dimethylbarbituric acid ; Palladium catalysts ; Chiral phosphane imine ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Allylation of 1,5-dimethylbarbituric acid (BS) with allyl acetate using in situ catalysts of palladium(II) acetylacetonate and chiral phosphane imine ligands results in the enantioselective formation of 5-allyl-1,5-dimethylbarbituric acid (ABS) as the main product with up to 34% ee and 3,5-diallyl-1,5-dimethylbarbituric acid (AABS) as a possible by-product, also with up to 34% ee. This reaction is a type of allylic alkylation, the stereoselectivity of which is difficult to control because the new stereocenter is formed in the nucleophile attacking from the side opposite to the metal atom. Classical optically active ligands do not give any enantioselectivity in this palladium-catalysed reaction. Chiral phosphane imine ligands, however, are a successful class of compound, synthesized by Schiff base condensation of 2-formylphenyl(diphenyl)phosphane with optically active primary amines. An optimisation of this ligand type showed that the substituents at the stereogenic center in the imine part should be a hydroxymethyl group and a bulky alkyl group, with the best ligand being the L-tert-leucinol derivative. A screening of other types of chiral ligand, e.g. phosphane amines and phosphane trisimines, has also been performed. NMR experiments and a molecular modelling study of the cation [(η3-allyl)Pd(2a)2]+ were carried out (tripos force field). The enantioselectivity of the phosphane imine ligands is explained by an interaction of the chiral side arm of one of the ligands, which extends to about 3 Å above the allyl plane, with the incoming nucleophile.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 55-59 
    ISSN: 1434-1948
    Keywords: Arsaalkenes ; Arsenic ligands ; Carbonyl complexes ; Chromium ; Iron ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of equimolar amounts of the metalloarsaalkene [(η5-C5Me5)(CO)2FeAs=C(NMe2)2] (1) with the carbonyl complexes [Ni(CO)4], [Fe2(CO)9], and [{(Z)-cyclooctene}Cr(CO)5], respectively, affords the adducts [(η5-C5Me5)(CO)2FeAs{M(CO)n}=C(NMe2)2] with [M(CO)n] = [Ni(CO)3] (2); [Fe(CO)4] (3), and [Cr(CO)5] (4). These feature η1 coordination of the arsaalkene ligand via the arsenic atom. The molecular structures of the complexes 3 and 4 have been determined by X-ray diffraction analyses.
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 37-41 
    ISSN: 1434-1948
    Keywords: Tripodal P ligands ; Rhodium ; Water-soluble complexes ; Immobilization ; Biphasic hydroformylation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the water-soluble tripodal phosphane ligand cis,cis-1,3,5-(PPh2)3-1,3,5-[CH2(OCH2CH2)xOCH3]C6H6 (x = 30-160) (5) has been achieved in a four-step reaction sequence. The alcohol Mo(CO)3[cis,cis-1,3,5-(PPh2)3-1,3,5-(CH2OH)3C6H6] (1) is converted to the corresponding alcoholate 2, which forms the polyethylene glycol derivative 3 in a polyaddition reaction with oxirane. After methylation of the end groups of 3, the ligand 5 is obtained by a combined photochemical/oxidative demolybdenation reaction. The water-soluble tripodal phosphane 5 and the methoxymethyl functionalized tripodal ligand 6 react with Rh(PPh3)3(CO)H to form the water-soluble and water-insoluble rhodium carbonyl hydrido complexes 5a and 6a, respectively. The catalytic activity of the rhodium complex 5a in the hydroformylation of 1-hexene was found to be comparable in a single-phase system (1-hexene/methanol) with that in the biphasic system (1-hexene/water). Only traces of alcohol were found, which demonstrates that the catalyst 5a displays higher selectivity in hydroformylation than in hydrogenation.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 67-72 
    ISSN: 1434-1948
    Keywords: Gallium ; Pentacoordination ; Salen(tBu) ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work is an exploration into the synthesis and reactivity of five-coordinate gallium complexes of the ligands, Salen(tBu)H2 [N,N′-ethylenebis(3,5-di-tert-butylsalicylideneimine), (1)], Salpen(tBu)H2 [N,N′-propylenebis(3,5-di-tert-butylsalicylideneimine), (2)], Salophen(tBu)H2 [N,N′-phenylenebis(3,5-di-tert-butylsalicylideneimine), (3)], and Salomphen(tBu)H2 [N,N′-(4,5-dimethyl)phenylenebis(3,5-di-tert-butylsalicylideneimine), (4)]. Fully characterized examples include those of general formula LGaX, where L = 1, X = Cl (5), Et (6); 3, X = Cl (7), Et (10); 4, X = Cl (8), Me (9) Et (11). X-ray structural data is presented for 6, 7, 9, 10, and 11. The ability of these complexes to undergo either alkane or salt elimination reactions is described. In one reaction the unusual salt: [{Salophen(tBu)Ga(MeOH)}2]+BPh-4 (12) is obtained.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 61-66 
    ISSN: 1434-1948
    Keywords: Arsenic ; Bioinorganic chemistry ; Dihydrolipoic acid ; Lipoic acid ; S ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The arsenic(III) dithiolate [PhAs(HlipS2)] (1, HlipS2-2 = reduced rac-lipoic acid) has been obtained via three different routes: (A) from (PhAsO)n and rac-dihydrolipoic acid, (B) from (AsPh)6 and rac-lipoic acid, and (C) from PhAsO(OH)2 and rac-dihydrolipoic acid. The latter method is also suitable for the preparation of [(4-NH2C6H4)As(HlipS2)] (2) from (4-NH2C6H4)AsO(OH)2. rac-Dihydrolipoic acid and Me2AsO(OH) react to give [(Me2As)2(HlipS2)] (3). These reactions indicate pathways by which mono- and diorganoarsenic compounds of various As oxidation states (I, III, and V) may inhibit enzymes that contain lipoic acid as a cofactor. X-ray structure analysis shows that 1 is a 2,4-disubstituted 1,3,2-dithiarsinane, i. e. a six-membered heterocycle. The phenyl group at the 2-position (As) adopts the axial orientation. (2RS,4RS)-1, which is the isomer found in the crystal, is thermodynamically more stable than the diastereomeric (2SR,4RS)-1 by 4.3 ± 0.8 kJ/mol (25°C). In solution, the epimerization by inversion of configuration at the ψ-tetrahedrally coordinated As atom is faster than expected, with acid catalysis (COOH groups!) being a possible cause.
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  • 10
    ISSN: 1434-1948
    Keywords: Nucleophilic phosphanylation ; Phosphanylphthalic acid ; Phosphanylphenylacetic acid ; Benzylaminophosphanes ; Water solubility ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral- and multiply-carboxylated phosphanes and phosphanyl derivatives of benzoic and phthalic acids (1-9) are accessible in high yields by nucleophilic phosphanylation of potassium or lithium salts of commercially available fluorobenzoic and 3-fluorophthalic acids with Ph2PH, Ph2PK, PhPLi2 Ph(K)P-(CH2)3-P(K)Ph in superbasic media (DMSO/KOH) or in THF and DME. The hitherto unknown phosphanylphenylacetic acids (10-13) and phosphanylbenzylamines RR′P-C6H4-CH2- NH2 (14-19, R, R′ = H, Me, Ph) with unsubstituted amino groups were also synthesized by this method. The diphenylphosphanyl derivatives 14-16 (R, R′ = Ph) are accessible by an alternative method involving LiAlH4 reduction of the phosphanylbenzonitriles (20-22), which were obtained in high yields by nucleophilic phosphanylation of the corresponding fluoro- or chlorobenzonitriles. The novel bidentate phosphanylbenzonitrile 23 has also been obtained using this synthetic route. All compounds were completely characterized by elemental analysis, NMR spectroscopy, and mass spectrometry.
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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 83-85 
    ISSN: 1434-1948
    Keywords: Phosphorus ylides ; Bis(ylene)phosphoranes ; Halogenophosphoranes ; X-ray structure analysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The iminophosphane (Me3Si)3C-P=N-Mes* (1) reacts with iodine to form the imino(methylene)phosphorane I-P(=N-Mes*)=C(SiMe3)2 (2). Upon subsequent treatment with AgCl, the corresponding chloro derivative 3 is obtained. Chlorine/bromine exchange in 3 with bromotrimethylsilane affords the bromo analogue 4. The structures of 2, 3 and 4 were confirmed by X-ray crystal structure analysis; each of the compounds features a trigonal-planar phosphorus atom.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 87-91 
    ISSN: 1434-1948
    Keywords: Imido complexes ; Titanium ; Heteroallylic ligands ; Benzamidinate ligands ; Diiminophosphinate ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Treatment of Ti(NtBu)Cl2(py)2 (1, py = pyridine) with bulky heteroallylic ligands in a 1:1 molar ratio affords the monosubstituted derivatives [PhC(NSiMe3)2]Ti(NtBu)Cl(py)2 (2), [MeOC6H4C(NSiMe3)2]Ti(NtBu)Cl(py) (3), and [Ph2P(NSiMe3)2]Ti(NtBu)Cl(py) (4). Similarly, 2:1 reactions afforded the disubstitution products [PhC(NiPr)2]2Ti(NtBu)(py) (6) and [Ph2P(NSiMe3)2]2Ti(NtBu) (7). The bis(pyridine) adduct Ph2P(NSiMe3)2Li(py)2 (5) was isolated as a by-product during the preparation of 4. The molecular structures of 7 has been established by X-ray crystallography.
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 93-99 
    ISSN: 1434-1948
    Keywords: 2-Methyl-1,2,3,4-tetrazole-5-thiolates ; 2-Phenyl-1,2,3,4-tetrazole-5-thiolates ; Palladium ; Platinum ; Copper ; Silver ; Gold ; Molecular structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular structures of nine transition metal tetrazolethiolates have been determined by X-ray structure determinations. The ligand is invariably coordinated through its sulfur atom to the metal center [M = PdII, CuI, AgI, AuI, AuIII, and Hg]. The M-S-C bond angles vary considerably, but this cannot be correlated with variations in the C-S bond lengths. Intermolecular association occurs for Ph3PAu(SCN4Me) via Au-S contacts, leading to dimeric strands in the solid state. The copper compound (Ph3P)3Cu4(SCN4Me)4 (5), possesses a rather asymmetric structure: one Cu atom is tricoordinated by 3 sulfur atoms, the other three are tetracoordinated by P and N as well as by S atoms.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 101-106 
    ISSN: 1434-1948
    Keywords: Phosphorus heterocycles ; Halogens ; Oxidations ; Electrophilic aromatic substitutions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(phosphonio)isophosphindolide iodide 1[I] reacts with an equimolar amount of I2 to yield the trihalide 1[I3], while treatment of 1[X] (X = Br, OTf) with excess Br2 furnishes the dibromophosphonium salt 6c[X]. The bromo-substituted bis- (phosphonio)isophosphindolide cations 5a and 5b are identified as intermediates in this reaction; 5b[Br] is also obtained in pure form by reaction of 6c[Br] with Zn or NEt3. Reaction of 1[OTf] with one equivalent of PhICl2 (7) affords the dichlorophosphonium salt 8a[OTf], which undergoes further substitution reactions in the presence of excess 7 and reacts with Me3SiI to give a mixture of 1[OTf] and I2 rather than a substitution product 9[OTf]. The results of a crystal-structure determination of 8a[OTf] are reported and the mechanistic aspects of the different oxidation/substitution reactions are discussed.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 1-14 
    ISSN: 1434-1948
    Keywords: One-dimensional multicomponent arrays ; Energy- and electron transfer ; Molecular motions ; Ruthenium ; Osmium ; Terpyridines ; Bis-terpyridines ; Bis-cyclometallating ligands ; Porphyrins ; Copper(I) rotaxane ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Transition metals are powerful three-dimensional templates, which can gather various functionalized ligands and orient them in a precise fashion so that complex multicomponent molecular systems can be obtained without constructing covalently-assembled edifices. The compounds thus prepared exhibit precise chemical or physical functions, which are governed by the design of the system. The construction of one-dimensional molecules around ruthenium(II) or osmium(II), using rigid ligands attached to the desired electroactive species, leads to systems that are able to undergo charge separation after photonic excitation. In other related compounds, a ruthenium(II)-based chromophore is, for example, connected to an osmium(II) complex by means of rod-like bridging ligand, thereby ensuring strict control over the Ru···Os distance. By tuning the length and the electronic properties of the bridge, one can control the efficiency of the electronic energy transfer between the two chromophores. In particular, the use of a bis-cyclometallating ligand is very conducive to energy transfer and allows the observation of this process up to a Ru…Os distance of ≈20 Å. By combining the building blocks of these inorganic systems with appropriate porphyrins, long-range (centre-to-centre distance between the donor and the acceptor porphyrins ≈30 Å) and relatively long-lived photoinduced charge separation has been demonstrated. Finally, with copper(I) as the template, compounds of the rotaxane family are obtained, which consist of a coordinating ring threaded by a string-like component. If this acyclic fragment is end-functionalized by two bulky stoppering groups and if it incorporates two different coordination sites (a bi- and a terdentate chelate site), novel dynamic properties are observed. The movement of a given fragment of the molecule is triggered by changing the metal oxidation state. This one-dimensional motion of the ring along the string on which it is threaded is controlled by redox manipulation, resulting in a primitive molecular machine.
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  • 16
    ISSN: 1434-1948
    Keywords: S ligands ; Transition metals ; Fluxionality ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation and characterization of RhI, PdII, and PtII complexes with chiral C2-symmetrical dithioether ligands derived from 1,1′-binaphthalene-2,2′-dithiol (BINAS) are reported. All complexes are fluxional in solution at room temp. Interconversion between the stereoisomers can take place through conformational equilibration of the chelate ring, and/or inversion of configuration at the stereogenic sulfur. In the solid state the palladium derivative of Me2BINAS shows a twisted chair conformation of the chelate ring, with both methyl groups in equatorial positions.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 107-112 
    ISSN: 1434-1948
    Keywords: Silicon ; Aminosilanes ; Aziridine ; Azetidine ; Molecular conformation ; Configuration determination ; Nitrogen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In a continuation of structural investigations of poly(amino)silanes, a series of silicon derivatives of aziridine and azetidine have been prepared. Analogies with the isoelectronic phosphorus ylide species and the high barrier to inversion at nitrogen in small N heterocycles were suggestive of steeply pyramidal and rather rigid configurations at the N atoms in the title compounds. Tetrakis(N-aziridino)silane (1) and tetrakis(N-azetidino)silane (2) have been synthesized from SiCl4 and LiN(CH2)x (x = 2, 3). Compound 1 is also formed when LiN(CH2)2 and HSiCl3 are used as starting materials, but with free aziridine a non-volatile product (1a) is obtained. In neither case could any trace of HSi[N(CH2)2]3 be detected. In contrast, RSiCl3 (R = Me, Ph) could readily be converted into the corresponding tris(N-aziridino)silanes (3, 4) by treatment with excess aziridine. Tris(N-azetidino)silane (5) was accessible from HSiCl3 and excess azetidine, but the product was found to contain an unknown impurity. In order to determine the local symmetry and the dynamics of the aziridine rings, 1H-NMR spectra were recorded at low temperature (-80°C). No splitting of the signals was observed, indicating that the inversion barriers are extremely low, even in the highly strained three-membered heterocycles. Nevertheless, single-crystal X-ray diffraction studies of the N-triphenylsilyl derivatives of aziridine (6) and azetidine (7) revealed an aziridinyl group with a steeply pyramidal configuration at nitrogen in 6 (sum of the angles at N 313.32°), and an azetidinyl group with a flat geometry in 7 (sum of the angles at N 350.96°). The Si-N bond is significantly shorter in 7 as compared to that in 6.
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  • 18
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 143-153 
    ISSN: 1434-1948
    Keywords: Azaboranes ; Six-coordinate nitrogen ; Deltahedral clusters ; Cluster opening ; Cluster closure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the majority of known azaboranes NaBbHc and their derivatives, the coordination number of the nitrogen atoms within the cluster does not exceed the classical values of 3 or 4. In the azaboranes closo-NB9H10, nido-NB10H13, and closo-NB11H12 and in their derivatives, however, the nitrogen atoms are 5- or 6-coordinate and thus represent a novel bonding situation. The synthesis, structure, and reactivity of these azaboranes are reviewed in this article.
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  • 19
    ISSN: 1434-1948
    Keywords: Arene complexes ; Catalysis ; Diazadiene complexes ; Iron ; Metal vapour ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two different routes to novel [(diene)(η6-2,6-dimethylpyridine)Fe] complexes are reported, both of which utilize metal vapour reactions. The presence of two small substituents on the 2,6-position of pyridine is essential for the η6-coordination of the heterocycle. Investigations on the reactivity and stability of the [(diene)(η6-arene)Fe] complexes are presented, including those of the benzene, phosphinine, and pyridine derivatives. These investigations give some hints to the relevant factors for determining the interaction between an iron atom and a π-coordinated neutral arene ligand, and their modification by a nitrogen or a phosphorus atom. Selective substitution of the 1,5-cyclooctadiene (COD) ligand of [(COD)(η6-arene)Fe] complexes by some 1,4-diaza-1,3-diene (DAD) derivatives is possible in the case of the benzene or phosphinine arene ligands, and [(DAD)(η6-arene)Fe] complexes are formed, but all DAD derivatives tested so far cause the complete disintegration of [(COD)(η6-2,6-dimethylpyridine)Fe]. [(DAD)(η6-arene)Fe] complexes exhibit a catalytic potential, which was evaluated by experiments on the catalytic cyclodimerization of 1,3-butadiene in the presence of [(Et2AlOEt)2] as a co-catalyst. This reaction yields up to 92% of 1,5-cyclooctadiene, and an almost quantitative butadiene conversion is possible in the presence of less than 0.1% of the catalyst. Structural investigations on [(N,N′-bis(cyclohexyl)ethylenediimine)(η6-toluene)Fe] 5a reveal some details of the Fe-DAD interaction. An effective electron back-donation from occupied iron d-orbitals into the π*-LUMO of the DAD is indicated.
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  • 20
    ISSN: 1434-1948
    Keywords: Bromine ; Imidazoline-2-selone ; Hypervalent Se compounds ; Dications ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidative addition of Br2 to the imidazoline-2-selone derivatives 1a-c has been studied by spectrophotometric and conductometric techniques. The experimental results clearly indicate that this reaction involves the dications 2a-c, containing an Se-Se bond, as intermediates in the formation of the hypervalent 10-Se-3 selenium compounds 3a-c containing the Br-Se-Br group. The crystal structure of 1,2-bis(3-methyl-4-imidazolin-2-ylium dibromoselenanide)ethane (3c), a new stable hypervalent 10-Se-3 compound, is also reported.
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  • 21
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 127-135 
    ISSN: 1434-1948
    Keywords: Tungsten ; Ditungsten complexes ; Acetylene complex ; Tritungsten complex ; W-W single bond ; W-W triple bond ; Photochemistry ; C-C bond formations ; Olefins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: [W2(η5-C5H5)2(CO)4(μ-η2:2-C2H2)] (1) and ethylene (A) react when irradiated with UV light at 253 K predominantly to [W2(η5-C5H5)2(CO)3(μ-η1:4-C4H5)(μ-H)] (3A), [W2(η5-C5H5)2(CO)4(μ-η1:3-C4H6)] (4A), and thermolabile [W2(η5-C5H5)2(CO)3(η4-C4H6)] (5A). Similarly, propene (B), 1-butene (C), and (E)-2-butene (D) yield mixtures of [W2(η5-C5H5)2(CO)3(μ-H)(μ-η1:4-1,3-dien-1-yl)] (3B, 3 C, 3D), [W2(η5-C5H5)2(CO)4(μ-η1:3-C4H5R] (4B, 4C), and [W2(η5-C5H5)2(CO)2(μ-η1:2-CO)(η4-1,3-diene) (5B, 5 C, 5D). With B and C also thermolabile [W2(η5-C5H5)2(CO)3(μ-η2:2-C2H2)(η2-C2H3R)] (2B, 2C) are formed. A by-product of the reaction of 1 with D is [W(η5-C5H5)(CO)(H){η4-(E)-C5H7CH3}], which is generated in two diastereomeric forms (6, 6′). In contrast, 1 yields no complexes with (Z)-2-butene (E) which contain ligands formed from coordinated acetylene and the olefin. From the reaction mixture only trinuclear [W3(η5-C5H5)3(CO)5(μ-η1:2-C2H3)] (7) was isolated, an alicyclic complex with a W-W single and a W-W triple bond. The crystal and molecular structures of 5D and 7 were determined by X-ray structure analysis. The constitutions of the other complexes were ascertained by IR and 1H-NMR spectroscopy.
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  • 22
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 159-161 
    ISSN: 1434-1948
    Keywords: Oxo clusters ; Titanium ; Metal alkoxides ; Sol-gel processes ; Carboxylato complexes ; Solid-state structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ti9O8(OPr)4(methacrylate)16 was obtained by the reaction of Ti(OPr)4 with an excess of methacrylic acid and analyzed by X-ray diffraction. The compound consists of a ring of nine [TiO6] octahedra linked by six μ2- and only two μ3-oxide bridges.
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  • 23
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 155-157 
    ISSN: 1434-1948
    Keywords: Bite angle ; Catalysis ; P ligands ; Palladium ; Cross-coupling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of the natural bite angle (βn) of diphosphane ligands on catalyst selectivity and activity in the palladium-catalyzed cross-coupling of sec-butyl magnesium chloride with bromobenzene was investigated. The calculated natural bite angles range from 78° for dppe (1,2-bisdiphenylphosphanoethane) to 110° for Xantphos. The natural bite angle of diphosphane ligands has a large effect on catalyst selectivity and activity. Both rate and selectivity of the cross-coupling reaction increase with increasing bite angle and reach a maximum value with DPEphos (βn = 102.7° ). Larger bite angles of the diphosphane ligands result in a decreased selectivity and activity.
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  • 24
    ISSN: 1434-1948
    Keywords: Pyridine ligands ; Bidentate bridging ligands ; Palladium ; Platinum ; N ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of the new potentially tridentate ligand 3,5-bis(dimethylaminomethyl)pyridine (3) is described. Coordination chemistry of this ligand has been investigated with PdII and PtII precursor compounds. Both a bidentate bridging bonding motif and a monodentate bonding mode is observed. The latter compounds incorporate 3 by coordination through the pyridinic N atom only. The former complexes contain ligand 3 bonded to 2 metal centres by bridging through coordination of one trialkyl N donor atom and the pyridinic N atom. The solid-state structure of a ligand bridged Pd dimer has been elucidated by single-crystal X-ray diffraction and corroborates with the solid-state IR data that suggested a trans-PdCl2 unit was present.
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  • 25
    ISSN: 1434-1948
    Keywords: Ligand field spectra ; Phosphonate complexes ; X-ray structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of transition-metal coordination compounds containing the ligand diethyl 2-quinolylmethylphosphonate (2-qmpe) is described. Complexes of CoII, MnII, NiII, CdII, and ZnII were found to be mutually isomorphous according to their X-ray powder diffraction patterns and IR spectra. The new coordination compounds were identified and characterized by elemental analysis, magnetic measurements, infrared and ligand-field spectra. The crystal structures of the complexes [M(2-qmpe)4(H2O)2](ClO4)2 (M = Ni, 1; Mn, 2) reveal six-coordinate [M(2-qmpe)4(H2O)2] cations with the qmpe ligand coordinating via the oxygen rather than via the nitrogen atom, as well as lattice perchlorate anions. The metal ion is octahedrally surrounded by the four oxygen atoms of the four organic ligands. The non-participation of the pyridine nitrogen atom is unusual. The two water molecules occupy the fifth and the sixth coordination sites in a trans configuration. The coordinated water molecules are strongly hydrogen-bonded to the pyridine nitrogen atom of the 2-qmpe, further stabilizing the solid-state structure. The geometry of the metal ion can be described as distorted octahedral. For the CuII complex, a hydroxo-bridged dinuclear structure of the type [Cu(2-qmpe)2(OH)(H2O)2]2(ClO4)2 is proposed, based on its spectroscopic and magnetic properties. Ligand-field spectra of the Co and Ni compounds were found to be in agreement with the tetragonally distorted octahedral geometry.
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  • 26
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 183-189 
    ISSN: 1434-1948
    Keywords: Tripodal ligands ; Cobalt complexes ; Bridging ligands ; Exchange coupling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Weak antiferromagnetic exchange interactions are observed in two CoII dimers of the general formula [{(triphos)Co}2(μ-dicarboxylato)](BF4)2 where the dicarboxylate is the dianion of fumaric acid [3 ·(BF4)2] or terephthalic acid [4 ·(BF4)2] and triphos is the tridentate phosphorus ligand 1,1,1-tris(diphenylphosphanomethyl)ethane. In these complexes the metal ions are separated by 8 and 10 Å, as determined by X-ray crystallography. Insight into the interaction pathway is gained through molecular orbital calculations performed on model compounds. The influence of bridging-ligand distortions and the stereochemistry around the two cobalt centres is discussed.
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  • 27
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 177-181 
    ISSN: 1434-1948
    Keywords: Silanes ; Rearrangements ; Polysilanes ; Hypersilylalcohols ; 1,2-Trimethylsilyl migration ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the presence of strong acids, such as HCl or H2SO4, 1-hydroxyalkyltris(trimethylsilyl)silanes (Me3Si)3Si-C(OH)R1R2 (1a-f) isomerize by 1,2-Me3Si/OH exchange to give the trimethylsilylmethylsilanols (Me3Si)2Si(OH)-C(SiMe3)R1R2 (4a-f) [R1,R2: a: Me, Me; b: H, 4-MeC6H4; c: H, 4-iPrC6H4; d: H, Mes; e: H, 2-Me2NC6H4; f: H, 2,4,6-(MeO)3C6H2]. A mechanism for the isomerization is proposed. In the case of the reaction of 1d with sulfuric acid, the silylsulfate (Me3Si)2Si(OSO3H)-C(SiMe3)HMes (5) was isolated. 5 is the intermediate in the H2SO4-catalyzed isomerization of 1d and was converted in situ with methanol, acetic anhydride, HF or HCl to give the respective methoxysilane 6, acetoxysilane 7, fluorosilane 8, or chlorosilane 9. Deprotonation of 4a, d, f with sodium hydride causes a further rearrangement, a 1,3-C,O-trimethylsilyl migration, to give the siloxanes (Me3Si)2(Me3SiO)Si-CHR1R2 (11a, d, f).
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  • 28
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 191-202 
    ISSN: 1434-1948
    Keywords: Polynuclear complexes ; Carbene complexes ; Bridging ligands ; Alkynyl complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The sequential reaction of two equivalents of the dimethylamino(ethynyl)carbene complexes [(CO)5M=C(NMe2)C≡CH] [M = W (1a), Cr (1b)] with two equivalents of nBuLi and one equivalent of a transition metal dichloride, [Cl2M′(Ln)], affords trinuclear biscarbene complexes of the type [(CO)5M=C(NMe2)C≡C-M′(Ln)-C≡CC(NMe)2=M(CO)5] [M′(Ln) = Ni(PEt3)2 (2a, b), Pd(PEt3)2 (3a, b), Pt(PEt3)2 (4a, b), Fe(dmpe)2 (6a), Hg (8a), Ti(η5-C5H5)2 (9a, b)] [dmpe = 1,2-bis(dimethylphosphino)ethane]. Treatment of 1a with equimolar amounts of first nBuLi and then [Cl2M′(Ln)] results in the formation of the monosubstitution products [(CO)5W=C(NMe2)C≡CM′(Ln)] [M′(Ln) = trans-Pd(PEt3)2Cl (5a), trans-Fe(dmpe)2Cl (7a)]. Additionally, the synthesis of the heterobimetallicethynylcarbene complex [(CO)5W=C(NMe2)C≡CPd(PEt3)2C≡CH] (10a), starting from 1a and [ClPd(PEt3)2C≡CH], is described. When three equivalents of 1a are treated, first with three equivalents of nBuLi and then with one equivalent of the trihalides PCl3 or BBr3, the novel tris(ethynylcarbene) complexes [{(CO)5W=C(NMe2)C≡C}3E] [E = B (11a), P (12a)] are obtained. The reaction of four equivalents of 1a,b with four equivalents of nBuLi, followed by addition of one equivalent of a group 14 tetrachloride [M′Cl4], yields the novel tetrakis(ethynylcarbene) complexes [{(CO)5M=C(NMe2)C≡C}4M′] [M′ = Si (13a, b), Ge (14a), Sn (15a, b)]. The complexes 8a, 9a, 12a, and 15a were characterized by X-ray structural analyses. All spectroscopic and structural data suggest that the carbene fragments and the central transition metal or heteroatom in these new bis-, tris-, and tetrakis(ethynylcarbene) complexes interact only weakly.
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  • 29
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 203-210 
    ISSN: 1434-1948
    Keywords: Gallium(III) halides ; Indium(III) halides ; Phosphanes, polydentate ; Complexes ; Crystallography ; Lewis acid catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of gallium and indium trihalides with 1,2-bis(diphenylphosphanyl)benzene (DP) and bis[(2-diphenylphosphanyl)phenyl]phenylphosphane (TP) lead to a variety of molecular and ionic complexes. Treatment of InCl3 with DP results in [(DP)2InCl2]+[InCl4]- (1). With InBr3 or InI3 molecular 1:1 complexes (DP)InX3 (2: X = Br, 3: X = I) and ionic 1:2 complexes [(DP)InX2]+[InX4]- (4: X = Br, 5: X = I) are obtained. With GaBr3 and GaI3 only the ionic complexes [(DP)GaX2]+[GaX4]- (6: X = Br, 7: X = I) are generated. According to single-crystal X-ray analyses the environment of the metal center is octahedral in the cation of 1, square pyramidal in 3, and tetrahedral in the cations of 5 and 7. The reactions of TP with GaI3 or InI3 afford ionic complexes [(TP)MI2]+[MI4]- (8: M = Ga, 9: M = In). As shown by 31P-NMR studies and X-ray analyses, TP acts as a bidentate ligand in both complexes. The central phosphorus atom is not engaged in coordinative bonding. The 31P resonances of all compounds appear at higher field as compared to the free ligand. This phenomenon calls for further investigations and a detailed theoretical treatment.
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  • 30
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 221-226 
    ISSN: 1434-1948
    Keywords: Polysilanes ; Polysilyl anions ; Silylpotassium ; Silicon ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method is presented for the synthesis of tertiary, secondary, and primary polysilylpotassium compounds. Reaction of potassium tert-butoxide, in either DME or THF, with a suitable precursor molecule, proceeds by cleavage of a trimethylsilyl- polysilanyl bond, and formation of trimethylsilyl tert-butyl ether and a polysilanylpotassium compound. This route allows easy and flexible access to a number of novel polysilanylpotassium compounds, avoiding the hitherto common use of poisonous mercury compounds.
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  • 31
    ISSN: 1434-1948
    Keywords: Rhenium ; Oxacyclocarbene complexes ; Vinylidene comlexes ; Alkynols ; Tripodal ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Various β-, γ-, and δ-alkynols have been reacted with the 16e- fragment [(triphos)Re(CO)2]+ generated in situ by H2 elimination from [(triphos)Re(CO)2(η2-H2)]BF4 [triphos = MeC(CH2PPh2)3]. Irrespective of the length of the alkyl chain between the C≡C and OH functional groups in the ω-alkynol, 2-oxacyclocarbene complexes are obtained. These include the 2-oxacyclopentylidene derivatives [(triphos)Re(CO)2{=CCH2CH2CH2O}]BF4 and [(triphos)Re(CO)2{=CCH2CH2CH(Me)O}]BF4, the 2-oxacyclohexylidene dervivatives [(triphos)Re(CO)2{=CCH2CH2CH2CH2O}]BF4 and[(triphos)Re(CO)2{=CCH2CH2CH2CH(Me)O}]BF4, and the 2-oxacycloheptylidene complex [(triphos)Re(CO)2{=CCH2CH2- CH2CH2CH2O}]BF4. The latter compound contains a unprecedented seven-membered oxacarbene ring. The rhenium-assisted δ-alkynol to 2-oxacyloheptylidene rearrangement proceeds via the hydroxybutylvinylidene kinetic intermediate [(triphos)Re(CO)2{C=C(H)CH2CH2CH2CH2OH}]BF4, which has been characterized in both the solid state and solution. An X-ray analysis has been carried out on a single crystal of [(triphos)Re(CO)2{=CCH2CH2CH(Me)O}]BF4. The structure of this complex consists of [(triphos)Re(CO)2{=CCH2CH2CH(Me)O}]+ cations and tetrafluoroborate anions with no interspersed solvent molecules. A facial triphos ligand, two cis-disposed carbonyl groups and a 2-oxacyclopentylidene ligand coordinate the Re centre in a slightly distorted octahedral environment.
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  • 32
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 227-235 
    ISSN: 1434-1948
    Keywords: Hydrostannylation ; Phosphaalkynes ; 1,2-Dihydro-1,3-diphosphetes ; Homocubanes ; Carbonyl complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydrostannylation of phosphaalkynes 8 with tin hydrides 1 depends on the stoichiometry employed: Thus, the 1,2-dihydro-1,3-diphosphetes 10 are isolated when an excess of phosphaalkyne 8 is used. On the other hand, an increase in the tin hydride concentration favors the formation of the phosphanes 11 and 12. Synthesis of the 1,2-dihydro-1,3-diphosphetes 14 and 16 was achieved by the use of diorganotin hydrides 13 or chloro(organo)tin hydrides 4, respectively. An isolated and characterized by-product of the latter reaction was the phosphorus-carbon-tin cage 17. Furthermore, the following reactions of the 1,2-dihydro-1,3-diphosphetes 10 were performed: isomerization reactions, complexation reactions with transition-metal complexes, and substitution of the hydrogen atom by iodine.
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  • 33
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 237-244 
    ISSN: 1434-1948
    Keywords: Titanium complexes ; Amido-cyclopentadienyl ligand ; Titanium alkyl ; Intramolecular coordination ; Ethene polymerization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Titanium complexes containing a linked isopropyl- or benzylamido(tetramethylcyclopentadienyl) ligand C5Me4SiMe2NR (R = iPr, CH2Ph,) and one bidentate organyl group C6H4(CH2NMe2)-2, CH2C6H4(NMe2)-2, and {η5-C5H3(CH2NMe2)-2}Fe(η5-C5H5) were prepared by salt metathesis of the corresponding dichloro complex Ti(η5:η1-C5Me4SiMe2NR)Cl2 with the lithium organyl. Single crystal X-ray structural analysis of Ti(η5:η1-C5Me4SiMe2NCH2Ph)- {C6H4(CH2NMe2)-2}Cl and of Ti(η5:η1-C5Me4SiMe2NiPr){CH2C6H4(NMe2)-2}Cl revealed the presence of intramolecular coordination with square pyramidal geometry around titanium. In the ferrocenyl derivative Ti(η5:η1-C5Me4SiMe2NCH2Ph)[{η5-C5H3(CH2NMe2)-2}Fe(η5-C5H5)]Cl the NMe2 group is not bonded at the titanium atom. Ethene polymerization catalyzed by these complexes upon activation with methylaluminoxane was examined.
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  • 34
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 245-252 
    ISSN: 1434-1948
    Keywords: Alkylamines ; Arylamines ; Zinc ; Cadmium ; Mercury ; X-ray diffraction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homoleptic intramolecularly stabilized organozinc, -cadmium, and -mercury compounds MR2, with R bearing an amino function, have been synthesized from the corresponding metal dichlorides MCl2 and the lithium salts LiC6H4CH2NEt2-2 (1), LiC6H3(CH2NMe2)2-2,6 (2), LiC6H3(CH2NEt2)2-2,6 (3), (LiCH2CH2CH2)2NMe (4), and LiCH2CH2CH2NC5H10 (5). The crystal structures of Hg(C6H4CH2NEt2-2)2 (1c), [M(CH2CH2CH2)2NMe]2 [M = Zn (4a), Hg (4c)], and of M(CH2CH2CH2NC5H10)2 [M = Zn (5a), Cd (5b)] have been determined by X-ray diffraction. 4a and 4c form dimers with an unusual coordination number (three) of the central metal.
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  • 35
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 253-256 
    ISSN: 1434-1948
    Keywords: Titanium ; Vinylidene complexes ; [2+2] Cycloaddition ; Metallacycles ; Azatitanacyclobutanes ; Clathrates ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The titanocene vinylidene intermediate [Cp*2Ti=C=CH2] (9) reacted with the carbodiimides R-N=C=N-R [R = p-CH3C6H4 (19a), C6H11 (19b)] to give the N=C-cycloaddition products [Cp*2Ti{-NR-C(=NR)-(C=CH2)-}] [(R = p-CH3C6H4 (20a), C6H11 (20b)]. The X-ray structure of 20a in form of a surprisingly stable n-hexane clathrate is presented. The azatitanacyclobutane [Cp*2Ti{-NPh-C(Ph)(H)-(C=CH2)-}] (22) was formed from the reaction between 9 and benzylidene aniline [PhN=C(Ph)H (21)]. Reactivity studies showed that azatitanacyclobutanes are unreactive upon typical ring-enlargement reactions as observed for other four-membered titanacycles.
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  • 36
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 257-261 
    ISSN: 1434-1948
    Keywords: Phosphorus heterocycles ; 2H-Azaphosphirene complexes ; Carbene complexes ; Tungsten ; Cyclizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High-yield synthesis of para-substituted pentacarbonyl(3-phenyl-2H-azaphosphirene)tungsten complexes is reported, using a multi-step rearrangement reaction. Spectroscopic and mass-spectrometric data of these heterocyclic complexes are discussed; the 31P-NMR-chemical shifts clearly reflect the electronic influence of the para-phenyl substituents and the correlation with Hammett σp-constants is almost linear.
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  • 37
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 263-270 
    ISSN: 1434-1948
    Keywords: Zinc complexes ; Pyrazolylborate ligands ; Phosphate ligands ; Hydrolytic cleavage ; Condensation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Five different (pyrazolylborate)zinc hydroxide complexes Tp*Zn-OH (1) were used as hydrolytic reagents towards esters of various acids of phosphorus. Trimethyl phosphate and trimethyl phosphite could not be cleaved. Dimethyl and diphenyl phosphite yielded TptBu,MeZn-OPHO(OR) (2, 3). Triphenyl phosphate reacted slowly producing moderate yields of Tp*Zn-OPO(OPh)2 (4). Tris(p-nitrophenyl) phosphate was cleaved rapidly, forming Tp*Zn-OPO(OC6H4NO2)2 (5) and Tp*Zn-OC6H4NO2 (6). Alkylbis(p-nitrophenyl) phosphates showed intermediate reactivity, losing p-nitrophenolate upon hydrolysis and producing Tp*Zn-OPO(OR)(OC6H4NO2) (7, 8). When phosphorus acid diesters were employed, condensation between the Zn-OH and P-OH functions occurred. This proved to be the convenient way of preparing the organophosphate complexes Tp*Zn-OPO(Ph)2 (9), Tp*Zn-OPO(OPh)2 (4), and Tp*Zn-OPO(OC6H4NO2)2 (5). Six structure determinations showed the structural variability of the resulting complexes.
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  • 38
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 271-274 
    ISSN: 1434-1948
    Keywords: Zinc complexes ; Pyrazolylborate ligands ; Hydrolytic cleavage ; Diphosphate ; Sulfonatophosphate ; Disulfonate ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Three (pyrazolylborate)zinc hydroxide complexes Tp*Zn-OH were used as hydrolytic reagents to cleave the P-O-P, P-O-S, and S-O-S linkages of organic diphosphates, sulfonatophosphates, and disulfonates. The resulting complexes of the types Tp*Zn-OPO(OR)2 and Tp*Zn-OSO2R could also be obtained by condensation reactions between Tp*Zn-OH and HO-PO(OR)2 or HO-SO2R. Two of them were characterized by structure determinations.
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  • 39
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 275-281 
    ISSN: 1434-1948
    Keywords: Molybdenum ; Peroxo complexes ; Hydrogen bonds ; Catalysis ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ring-opening reaction of epoxycyclohexane with 2-[3(5)-pyrazolyl]pyridine results in the formation of racemic trans-2-[3-(2-pyridyl)-1-pyrazolyl]cyclohexanol (1). Kinetic resolution with lipase B from candida antarctica gives the (1S,2S) enantiomer of 1, the solid-state structure of which was determined by X-ray crystallography, as an enantiomerically pure tridentate ligand. Investigation by NMR spectroscopy of the corresponding oxodiperoxomolybdenum complex 2, where 1 acts as a bidentate chelate, proves the formation of a weak intramolecular MoVI(O2)····HO-C bridge in CHCl3 solution. This H bonding is broken by solvents such as acetone, THF or DMF, which are capable of forming hydrogen bonds to alcohols. Intermolecular hydrogen bonds between the OH groups and molybdenum peroxo moieties are also found in the solid-state structure of 2, leading to a helical arrangement of the peroxo complexes.
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  • 40
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 283-289 
    ISSN: 1434-1948
    Keywords: Gold ; Chalcogenide ; Flux reaction ; Structure determination ; Metal-metal bonding ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel compounds K2AuPS4 (1), Tl2AuPS4 (2), K2AuAsS4 (3), and KAu5P2S8 (4) have been synthesized by direct reaction of the elements with a molten alkaline polythiophosphate(arsenate) flux at 550°C. The crystal structures of these compounds have been determined by single-crystal X-ray diffraction techniques. 1, 2, and 3 crystallize in the monoclinic space group P21/m. The structures of 1, 2, and 3 consist of infinite, one-dimensional anionic chains running along the crystallographic b axis. The chains are separated by potassium or thallium ions. Neighbouring Au atoms are bridged by MS43- tetrahedra (M = P, As) in a trans orientation. Compound 4 crystallizes in the space group P21/c. The anionic chains of 4 are built up from linear AuS2 dumbbell units and PS43- tetrahedra. The chains extend along the [110] and [110] direction and are separated by charge balancing K+ cations. Each of the compounds was investigated by differential thermal analysis, FT-IR, and solid-state UV/Vis diffuse reflectance spectroscopy.
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  • 41
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 291-293 
    ISSN: 1434-1948
    Keywords: Boron ; Iron ; Boryl complexes ; η1-Coordinated borazine ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of η1-borazine complexes were obtained by the reaction of trichloroborazine with Na[(η5-C5R5)Fe(CO)2]. The compounds [{(C5R5)(CO)2Fe}nCl3-nB3N3H3] (1a, n = 1, R = Me; 1b, n = 2, C5R5 = C5H4Me; 1c, n = 3, R = H) have one to three iron-boron σ bonds and Fe-B π-interactions can be ruled out from the spectroscopic and structural results. All new borazine complexes were isolated as orange crystalline solids and characterized by multinuclear NMR methods and IR spectroscopy. The structure of 1b in the crystalline state was also determined by a single-crystal X-ray study.
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  • 42
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 295-298 
    ISSN: 1434-1948
    Keywords: Conjugate addition ; Enones ; Steroids ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transmetallation of arylmagnesium halides or aryllithium with Me2AlCl results in the formation of aryldimethylaluminum compounds. These arylaluminum compounds are useful reagents for conjugate additions to enones in the presence of Ni(acac)2 as a catalyst. 3-Aryl ketones are obtained in good yields in these catalytic reactions. Starting from the 3-oxo-Δ1,4-steroids this method gives access to 1α-arylsteroids.
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  • 43
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 299-303 
    ISSN: 1434-1948
    Keywords: Calix[4]arenes ; Calix[4]arene complexes ; Molybdenum ; Tungsten ; Metal-metal bonding ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of p-tert-butylcalix[4]arene LH4 to the dinuclear compounds M2(NMe2)6 (M = Mo, W) results in the formation of [NH2Me2]2[L2M2] 1 (M = Mo) and 2 (M = W). Both compounds have been characterized by spectroscopic methods and single-crystal X-ray diffraction. The metal-metal distances of 1 and 2, of 2.194(1) Å and 2.293(1) Å, respectively, are consistent with the retention of the M≡M triple bond. Both „ate” complexes contain a [M≡M]6+ dimetal core, supported by two bridging μ2-κ2O,κ2O-calix[4]arene ligands in the solid state. These compounds are the first examples of a formally fourfold deprotonated calix[4]arene acting as a μ2-κ2O,κ2O bridging ligand for two transition metal centres. The calix[4]arenes in 1 and 2 are distorted from a cone conformation in the uncomplexed ligand, to an elliptical cone section. 1H-NMR data at variable temperatures suggest fluxional behaviour of 1 and 2 in solution.
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  • 44
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 305-310 
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; Carbene homologues ; Boron ; Isoelectronic analogues ; Heterocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: While Arduengo-type carbenes are now well established for the Group IVa elements carbon, silicon and germanium, they are experimentally unknown for the isoelectronic anions with the Group IIIa elements boron, aluminum, gallium, and indium. In the present quantum chemical investigations, the bonding features of this class of compounds are explored. As a result, they are predicted to be stable species with sizeable singlet-triplet energy separations and electron affinities. Hence, they may be considered as valid targets for experimental investigations. An analysis of the electron density distribution in the case of boron and aluminum reveals a strongly polar B-N bond for the former, and a half Al-N bond with positive charge at the aluminum, emphasizing the donor-acceptor formulation for the latter.
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  • 45
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 311-317 
    ISSN: 1434-1948
    Keywords: Molecular recognition ; Amides ; Aluminium ; Thallium ; Structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ligands containing aromatic nitrogen heterocycles play a leading role in the molecular self assembling processes that lead to macromolecular architectures. The inductive effect of various metal fragments on those building blocks has not yet been studied systematically. To evaluate this effect we synthesized the homologous series of Group-13 metal complexes [Me2AlPy2N] (1), [Me2GaPy2N] (2), [Me2InNPy2]2 (3), and [Me2TlNPy2]∞ (4) (Py = 2-NC5H4), and characterized them by low-temperature X-ray structure analysis and 15N-NMR spectroscopy in solution. The electronic equivalence of the central and the ring nitrogen atoms leaves the energetic hyperface of the anion quite flat, and the electron density is polarized according to the requirements of the metal. In the aluminum and the gallium complexes 1 and 2 the metal center is coordinated exclusively through the nitrogen atoms within the pyridyl rings. The complexes with these hard metals are close-contact ion pairs. In the indium complex 3 the cis-cis orientation gives rise to a dimeric structure, while the unprecedented cis-trans arrangement in the thallium compound 4 leads to a polymeric structure. The complexes 3 and 4 have to be regarded as separated ion pairs of Me2M+ cations and Py2N- anions without any covalent bonds between the anionic moiety and the dimethylmetal cations, even in the solid state. The series of complexes proves the bis(2-pyridyl)amide to be an excellent self-adapting ligand. These findings are substantiated by NMR-spectroscopic studies in solution. Not only do the steric requirements of N heteroaromatic ligands have to be considered in molecular self-assembling processes but also the inductive effect of the different metal fragments.
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  • 46
    ISSN: 1434-1948
    Keywords: Palladium ; Platinum ; Bidentate nitrogen ligands ; p-Quinone ; Alkenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Compounds of the type M(N∩N-κN)(nq)2 and M2(μ2-N∩N)(μ2-pbq)2, in which nq = 1,4-naphthoquinone, pbq = 1,4-benzoquinone, and N∩N is a monodentate or bridging ligand of the α-diimine type, were obtained from reactions of Pd(dba)2 in toluene with the 3,3′-annelated-2,2′-bipyridines: 4,5-diazafluoren-9-one (dafo) and 4,5-diazafluorene (dafe) in the presence of the appropriate p-quinone. In the corresponding reactions with 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 2,2′-bipyrimidine (bpym), N,N′-dicyclohexyl-1,4-diaza-1,3-butadiene (chex-dab), bis[N-(o,o′-diisopropyl)phenylimino]acenaphthene (o,o′-iPr2-bian) and 5,6-dihydro-1,10-phenanthroline (dh-phen) only complexes of the type M(N∩N-κ2N)(Q) were formed (Q = nq, pbq). The structures of the complexes have been established by NMR in solution and by X-ray diffraction in the solid state; crystal structures of Pd(bpy-κ2N)(η2-pbq) (1) Pd(dafo-κN)(η2-nq)2 (14) and Pd2(μ2-dafo)(μ2,η2:η2-pbq)2 (16) have been determined. Of the ligands, dafo and dafe are the only ones apt to form complexes containing a monodentate or bridging N∩N ligand. This behaviour is ascribed to the geometrical constraints of dafo and dafe; the annelation by one carbon atom at the 3,3′-positions in these ligands causes an increase in bite angle from approximately 77° to 82°.
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  • 47
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 331-337 
    ISSN: 1434-1948
    Keywords: Bis(pentamethylcyclopentadienyl)phosphanes ; Aminobis(pentamethylcyclopentadienyl)phosphanes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bis(1,2,3,4,5-pentamethyl-1,3-cyclopentadien-1-yl)phosphanes 3-7 are formed in good yields by the reaction of the halogenophosphanes 2a or 2b with the appropriate nucleophile. Following another route, the dialkylaminobis(pentamethylcyclopentadienyl)phosphanes 11a-c have been synthesized by the treatment of dichloro(dialkylamino)phosphanes with two equivalents of (pentamethylcyclopentadienyl)lithium. The compounds 3-11 have been characterized by multinuclear NMR spectroscopy and 3, 5, 6, and 11a have also been characterized by single-crystal X-ray diffraction studies. The molecular structure of 11a is governed by steric congestion, which typically would lead to a parallel arrangement of the two pentamethylcyclopentadienyl ligands at the phosphorus atom. However, surprisingly, the crystal structure of the (dimethylamino)phosphane 11a, exhibits a tilted, rather than a parallel, conformation of the pentamethylcyclopentadienyl groups [tilt angle: 130.6(1)°].
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  • 48
    ISSN: 1434-1948
    Keywords: Rhodium ; Phosphanes ; Ligand redistribution ; Dichloromethane activation ; Oxidative addition ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dichloromethane reacts with dinuclear rhodium complexes [{(PR3)2Rh}2(μ-Cl)2] to give the bridging-methylene complexes [{(PR3)2RhCl}2(μ-Cl)2(μ-CH2)] (PR3 = PEt3, PPh2Me). The structure of the PEt3 complex has been established by X-ray diffraction study. The early stages of the reaction of [{(C8H14)2Rh}2(μ-Cl)2] with monophosphanes have been monitored by 31P NMR, evidencing chloride bridges cleavage and phosphane redistribution processes.
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  • 49
    ISSN: 1434-1948
    Keywords: Carbene complexes ; Carbyne complexes ; Asymmetric synthesis ; Carbohydrates ; Chiral auxiliaries ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chiral carbene complexes [Cp(CO)2Mn=C(OR*)Ph] (4a-e) were prepared by reaction of [Cp(CO)2Mn=C(OAc)Ph] (2) with HOR* [HOR* = 1,2:3,4-di-O-isopropylidene-D-galactopyranose (3a), 2,3,4,6-tetra-O-acetyl-D-galactopyranose (3b), 2,3,4,6-tetra-O-acetyl-D-glucopyranose (3c), (S)- (3d) and (R)-1,2-O-isopropylideneglycerol (3e)]. The replacement of a CO ligand with PTol3 in 4a-e proceeded diastereoselectively to give [Cp(CO)(PTol3)Mn=C(OR*)Ph] (5a-e). The diastereoselectivity increased in the order a, b, c, d: de = 8% (5a), 33% (5b), 70% (5c), 〉 96% (5d). For (R)-5d the isomer with the (S) configuration at manganese (SMn) was formed predominantly. For (S)-5d, only (RMn,S)-5d was detected (de 〉 96%). Photolysis of (R)-4d in the presence of phosphites or phosphanes afforded (SMn)-[Cp(CO)(PR3)Mn=C(OR*)Ph] [PR3 = P(OPh)3 (8), P(OMe)3 (9), P(OMe)2Ph (10), P(OMe)Ph2 (11), PPh3 (12), P(C6H4Cl-p)3 (13)] with a de 〉 96%. Photolysis of (S)-4d in the presence of P(OMe)3 gave (RMn,S)-9. Complex (R)-14 [related to (R)-4d] was obtained from [Cp(CO)2Mn=C(OAc)Tol-p] and 3d. Replacement of CO by PR3 in (R)-14 gave (SMn,R)-[Cp(CO)(PR3)Mn=C(OR*)Tol-p] [R = Tol-p (15), OMe (16), C6H4Cl-p (17)] with a de 〉 96%. In solution, the PTol3-substituted complex 5d is configurationally stable whereas the P(OMe)3 complex 9 epimerizes slowly at room temperature in CH2Cl2, Et2O, and THF within about one week.
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  • 50
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 355-360 
    ISSN: 1434-1948
    Keywords: Gallium ; Indium ; Low-valent compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tetrakis[bis(trimethylsilyl)methyl]digallane(4) (1) with a Ga-Ga single bond and the corresponding diindane(4) 2 with an In-In single bond were treated with different protic reagents: tert-Butyl alcohol did not react with 1 at all, while phenol gave a mixture of unknown products, which could not be separated. The more acidic pentafluorophenol did not react as an acid, but C-F bonds were cleaved to form almost quantitatively the dimer (R2GaF)2 5, which was characterized by a crystal-structure determination. Water and 1 yielded the dimeric dialkylgallium hydroxide 6. The Ga-Ga bond was also cleaved by the reaction of 1 with durylthiophenol (duryl = 2,3,5,6-tetramethylphenyl), which gave two main products: R2Ga(SDuryl) 7 and RGa(SDuryl)2 8. In contrast, the chelating acid dibenzoylmethane reacted by means of a substituent exchange, with the release of two equiv. of bis(trimethylsilyl)methane for each formula unit of 1, to form 9, in which the Ga-Ga bond is retained and each chelating 1,3-diphenyl-1,3-propanedionato ligand is in a terminal position bonded to only one Ga atom, in more than 80% yield. The Ga-Ga bond is shortened [244.1(1) pm] compared to that in the starting compound tetraalkyldigallane(4) 1. The In-In bond of diindane(4) 2 is, however, cleaved in a similar reaction with dibenzoylmethane, and only the fragmentation product dialkyl(1,3-diphenyl-1,3-propanedionato)indium 10 could be isolated.
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  • 51
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 367-373 
    ISSN: 1434-1948
    Keywords: Phthalocyanines ; Indium ; Indium-carbon bond ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of highly soluble chloro(phthalocyaninato)indium(III) complexes RxPcInCl (3a: R1 = tert-butyl, R2 = H, x = 4 and 4a: R1 = R2 = n-pentyl, x = 8), and their reactions with R′MgBr [R′ = p-trifluoromethylphenyl- (b), m-trifluoromethylphenyl- (c), p-fluorophenyl- (d), perfluorophenyl- (e)] leading to the stable σ-bonded aryl(phthalocyaninato)indium(III) complexes 3b-e, 4b-e are described. All compounds were characterized by IR, UV/Vis, MS, 1H, 13C and 19F NMR as well as elemental analyses. Phenyl(phthalocyaninato)indium(III) (4f) was prepared by the reaction of (n-C5H11)8PcInCl (4a) with PhLi. The high solubility of the complexes 3a-e and 4a-f is, aside from the influence of the peripheral substituents, considered to be derived from the large dipole moments present which are due to the strongly electron withdrawing axial ligands, and from the lower tendency of axially substituted phthalocyaninato metal complexes to form aggregates.
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  • 52
    ISSN: 1434-1948
    Keywords: Phosphorus ; Phosphonic anhydrides ; Oligophosphonic acids ; Peptide synthesis ; Solid-state structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By reaction of RP(O)Cl2 with RP(O)(OSiMe3)2, phosphonic anhydrides (RPO2)3 (R = tBu, 2-methylphenyl, 2,4,6-trimethylphenyl) 1a-c are conveniently obtained. In contrast to 1b and 1c, compound 1a is remarkably stable against protolysis. Intermediates of hydrolysis of 1a, namely tris(tert-butyl)triphosphonic acid (2) and bis(tert-butyl)diphosphonic acid (3), can also be isolated in good yield. The structures of 1-3 were determined mainly by NMR spectroscopy (1 H, 13C, 31P). Assuming an energetic preference for the chair conformations in solution, and considering the steric requirements of the bulky substituents R, configurations Ia (point group Cs, two R in equatorial positions) for 1a and b, and IIa (point group C3v, all R equatorial) for 1c are suggested. - Reaction of 1a with N-benzyloxycarbonylglycine (4) in methanol affords strong evidence that in the first step of peptide synthesis with (RPO2)3, a mixed anhydride of triphosphonic acid and the N-protected amino acid is formed. - The crystal structure of 1a (monoclinic, space group P21/n) widely corresponds to the suggested configuration Ia, but reveals an envelope conformation for the six-membered ring with a P3O2 plane in the crystal. In the crystal structure of the octahydrate of the disodium salt of 2 (monoclinic, space group P21/c), it can be seen that the polar end groups of the anions [tBu3P3O7]2- together with the water molecules and the Na+ cations, form hydrogen-bonded double-layers, strictly separated from each other by the non-polar tert-butyl groups of the anions.
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  • 53
    ISSN: 1434-1948
    Keywords: α-Metallated amino acids ; Palladium ; Platinum ; Oxidative addition ; α-Bromoglycinate ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidative addition of methyl N-benzoyl-2-bromoglycinate to bis(dibenzylideneacetone)palladium, in the presence of 2,2′-bipyridyl, and to (Ph3P)2Pt(η2-C2H4) gives the α-metallated glycine esters 1a and 2a. Abstraction of bromide from 1a, 2a, using AgSbF6 or AgBF4, affords the cationic C,O-chelate complexes [(bpy)Pd-CH(CO2Me)NHC(Ph)O]+ (1b,c) and [(Ph3P)2Pt-CH(CO2Me)NHC(Ph)O]+ (2b), respectively, featuring coordination of the amide O atom. The complexes 1b and 2b have been characterized by X-ray diffraction.
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  • 54
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 381-388 
    ISSN: 1434-1948
    Keywords: Phosphanes ; Phosphorus ylides ; Nucleophilic addition ; Structure elucidation ; NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chlorophosphanyl and dichlorophosphanyl alkylidene- and benzylidenephosphoranes 6 and 8 are converted by reaction with LiAlH4 to the respective phosphanes 7 and 9. The former can be isolated, but decompose on heating or on protonation to give the ylidyl diphosphane 11 and the phosphonium ylide or phosphonium salt, respectively. The final products are the cyclooligophosphanes 15-17. Only the C-tert-butyl derivative 7c is stable in both regards. The conformation of the RPH group in 7 as compared to that of the RPCl group in 6 clearly reflects their different interaction with the ylide moiety.
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  • 55
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 397-400 
    ISSN: 1434-1948
    Keywords: Polychalcogenides ; Selenium ; Selenocarbamato complexes ; 77Se NMR ; Crystal structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of the potassium polyselenides „K2Se6” and „K2Se8” with [CpW(CO)3Cl] and 18-crown-6 in DMF lead to a mixture of the selenido complexes {[CpW(CO)3]2Se4} 1 and [(18-crown-6)K]+[CpW(Se4)2]- 3 and the Se-bonded selenocarbamato complex [CpW(CO)3SeC(O)NMe2] 2 in yields depending on the selenium content of the used potassium polyselenides („K2Se6” or „K2Se8”). A similar reaction in THF produces {[CpW(CO)3]2Se4} as the main product. X-ray structures of 1 and 2 were determined. In 1 the Se4-chain is bonded in a μ2-η1 fashion, with corresponding W-Se bond lengths of 264.0(1) and 264.3(1) pm. The Se-Se bond lengths lie in the range 232 to 237 pm. The first example of an η1 Se-bonded selenocarbamato ligand is observed in the crystal structure of 2, with a W-Se bond length of 263.1(1) pm. The 77Se-NMR data are compared with the corresponding data of related complexes.
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  • 56
    ISSN: 1434-1948
    Keywords: Rhodium ; N ligands ; Carbonyl complexes ; Methoxycarbonyl ; Dinuclear complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 1,4,7-trimethyl-1,4,7-triazacyclononane (Cn*) with [{(CO)2Rh(μ-Cl)}2] in methanol at 0°C, followed by the addition of NH4PF6, results in the formation of the mononuclear carbonyl complex [Cn*Rh(μ-CO)2]PF6 ([1]PF6), the dinuclear carbonyl complex [Cn*Rh(μ-CO)3RhCn*](PF6)2 {[2](PF6)2} and the dinuclear methoxycarbonyl complex [Cn*Rh(C(O)OMe)(μ-CO)2RhCn*]PF6 ([3]PF6). The reaction of [2](PF6)2 with NaOMe results in formation of [3]PF6 by the attack of the methoxide at a bridging carbonyl. Treatment of [3]PF6 with NH4PF6 regenerates [2](PF6)2, thus showing that the methoxylation of [2](PF6)2 is reversible. The structures of [1]PF6, [2](PF6)2 and [3]PF6 have been determined by single-crystal X-ray diffraction. For [3]PF6 an unprecendented facile, reversible, migration of the C(O)OMe ligand between the two rhodium centres of the Rh(μ-CO)2Rh core is observed.
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  • 57
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 389-396 
    ISSN: 1434-1948
    Keywords: Substitution mechanism ; Platinum ; Pressure dependence ; Kinetics ; Dinuclear complex ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both reaction steps observed for the substitution of water by thiourea in the complexes [Pt(en)(OH2)2]2+ and [Pt(phen)(OH2)2]2+ (en = ethylenediamine, phen = 1,10-phenanthroline) were investigated under pseudo-first-order conditions using the stopped-flow technique. The substitution of the second water molecule in each complex was also studied under high pressure. The observed pseudo-first-order rate constants kobs (s-1) obeyed the equation k1,2obs= k1,2[tu] (tu = thiourea), where “1” and “2” refer to the first and the second substitution reactions, respectively. Kinetic parameters associated with the substitution process are: k1en (25.0°C, pH = 3.0, I = 0.1 M) = 25.6 M-1 s-1, ΔH# = 51 kJ mol-1, ΔS# = -48 J K-1 mol-1; k2en (same conditions) = 12.1 M-1 s-1, ΔH# = 30 kJ mol-1, ΔS# = -124 J K-1 mol-1, ΔV# = -7 cm3 mol-1; k1phen (25.0°C, pH = 1.0, I = 0.1 M) = 2900 M-1 s-1, ΔH# = 41 kJ mol-1, ΔS# = -41 J K-1 mol-1; k2phen (same conditions) = 1170 M-1 s-1, ΔH# = 37 kJ mol-1, ΔS#= -61 J K-1 mol-1, ΔV# = -5 cm3 mol-1. The temperature and pressure dependence of all the processes studied suggest an associative substitution mechanism. The hydroxo-bridged dinuclear complex [{Pt(phen)(μ-OH)}2]2+ is formed from [Pt(phen)(OH2)2]2+ in aqueous solution unless the solution is very dilute and highly acidic. The X-ray structure of [{Pt(phen)(μ-OH)}2](F3CSO3)2 · 2 H2O was determined. It belongs to the triclinic space group P1­ and has one formula unit in the unit cell. The unit cell dimensions are a = 7.126(5), b = 9.665(5), c = 12.774(7) Å; α = 71.85(5), β = 85.52(5), γ = 73.12(5) deg; V = 799.9(8) Å3. The structure was solved with the Patterson method and refined to R = 0.061. A square planar coordination of the platinum centers is observed, with no deviations from planarity but distortions due to the small bite angle of phen and the four-membered ring. No significant lengthening of the Pt-O bond [mean value: 2.03(1) Å] is observed in comparison with [{Pt(NH3)2(μ-OH)}2]2+.
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  • 58
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 407-414 
    ISSN: 1434-1948
    Keywords: Ruthenium ; Phosphorus ; Triphos complexes ; Fluxionality ; Arm-off dissociation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structural fluxionality is apparent in the 1H- and 31P-NMR spectra of compounds of the type [Ru(L)(MeCN)(triphos)](CF3SO3), 2-5, at 25°C, where L represents a diorganyldithiocarbamate or a heterocyclic κ2N,S coordinating thioamide. In contrast, complexes [Ru(Et2NCS2)(Y)(triphos)]n+ (6, n = 1, Y = CO; 7, n = 0, Y = CN-; 8, n = 0, Y = H-) are stereochemically rigid in solution at this temperature, indicating that MeCN dissociation must occur for the crowded octahedral coordination spheres of 2-5. Reaction of [Ru(MeCN)3(triphos)](CF3SO3)2, 1, with Na(Et2NCS2) at a 1:2 molar ratio yields [Ru(Et2NCS2-κ2S)(Et2NCS2-κS)(triphos)], 9, which slowly converts to [Ru(Et2NCS2-κ2S)2(triphosO-κ2P)], 10, on recrystallization from ethanol/acetone under air [triphosO is O=P(Ph)2CH2C(CH3)(CH2PPh2)2]. A similar κ3P→κ2P arm-off dissociation leads to the formation of [Ru(mpy-κ2N,S)2(triphosO-κ2P)] (13) and [Ru(mmim-κ2N,S)2(triphosO-κ2P)] (14) (Hmpy = 2-mercaptopyridine, Hmmim = 2-mercapto-1-methylimidazole). Crystal structures are reported for [Ru(mbt-κ2N,S)(MeCN)(triphos-κ3P)](CF3SO3) (4) (Hmbt = 2-mercaptobenzothiazole), [Ru(mpym-κ2N,S)(mpym-κS)(triphos-κ3P)] (11) (Hmpym = 2-mercaptopyrimidine) and 14, the latter of which is present as the OC-6-13 isomer.
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  • 59
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 415-418 
    ISSN: 1434-1948
    Keywords: Pentacoordinate silicon ; Zwitterionic λ5Si-silicate ; SiO2N2C framework ; Hypervalent compounds ; Main-group elements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of (Me2N)3SiCH2CH2NMe2 with 2-amino-4-nitrophenol (molar ratio 1:2) in acetonitrile yields the zwitterionic spirocyclic λ5Si-silicate [2-(dimethylammonio)ethyl]bis[4-nitrobenzene-2-aminato-1-olato(2-)]silicate (7). Compound 7 was characterized by 1H, 13C, and 29Si solution-state and 29Si solid-state NMR spectroscopy, in addition to single-crystal X-ray diffraction. The SiO2N2C framework of 7 is characterized by five „normal” covalent bonds.
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  • 60
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 425-428 
    ISSN: 1434-1948
    Keywords: Ethylene polymerization ; Group 5 metal complexes ; Hydridotris(pyrazolyl)borates ; Alkyne ligands ; Migratory insertion ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Substituted hydridotris(pyrazolyl)borato (Tp′) niobium complexes of the type [Tp′NbMe2(PhC≡CMe)] polymerize ethylene (under 1 atm, at room temp. and in toluene) when treated with an equimolar amount of B(C6F5)3. A clear relationship is observed between the stereoelectronic nature of the complex and catalytic activity. This is discussed on the basis of electrochemical data for the dichloro complexes [Tp′NbCl2(PhC≡CMe)], and the rates of alkyl migration in [Tp′Nb(Cl)(R)(PhC≡CMe)] (R = CH2Me, CH2SiMe3). For a given electron density at the metal, the bulky TpMe2,4-Cl yields a catalyst which is more than 6 times as active as the unsubstituted Tp based catalyst.
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  • 61
    ISSN: 1434-1948
    Keywords: Alkyne complexes ; Titanium ; Zirconium ; Coordination mode ; Metallacycles ; Cyclopentadienes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The influence of metals, alkyne substituents, Cp substitution and additional ligands on the stability of bridged and unbridged η2-alkyne-titanocene and -zirconocene complexes has been investigated. The reduction of the complex [(η5-C5H4)-SiMe2-(η5-C5H4)]TiCl2 with magnesium in the presence of tolan (PhC2Ph) does not give the expected alkyne-titanocene complex [(η5-C5H4)-SiMe2-(η5-C5H4)]Ti(η2-PhC2Ph) but by coupling of two tolan molecules the corresponding titanacyclopentadiene [(η5-C5H4)-SiMe2-(η5-C5H4)]TiC4Ph4 (1) was obtained. In the analogous reaction with Me3SiC2SiMe3 the stable η2-alkyne complex without additional ligands [(η5-C5H4)-SiMe2-(η5-C5H4)]Ti(η2-Me3SiC2SiMe3) (2) was formed, due to the sterical influence of the alkyne substituents. The compounds without additional ligands (thi)2Ti(η2-PhC2Ph) (3) and (thi)2Ti(η2- Me3SiC2SiMe3) (5) were isolated from the unbridged titanocene complex (thi)2TiCl2 (thi = tetrahydroindenyl). Two equivalents of complex 3 reacted with one equivalent of water to yield the dimeric alkylidene-μ-oxo complex [(thi)2Ti(CPh=CHPh)]2(μ-O) (6). The reaction of the unbridged zirconocene compound (thi)2ZrCl2 gave the alkyne complex (thi)2Zr(THF)(η2-Me3- SiC2SiMe3) (7) which is stabilized by THF. At higher temperature THF was eliminated from the orange complex 7 forming the green complex (thi)2Zr(η2-Me3SiC2SiMe3). This behaviour was investigated in detail using NMR spectroscopy and compared to similar complexes such as Cp2Zr(η2-Me3SiC2SiMe3) (not stable without THF), (ebthi)2Zr(η2-Me3SiC2SiMe3) (ebthi = ethylenebistetrahydroindenyl; stable without THF) and Cp*2Zr(η2-Me3SiC2SiMe3) (Cp* = pentamethyl-Cp, stable without THF). All complexes were characterized by spectroscopic methods. X-ray structural determinations were conducted for the complexes 1, 3 and 7. Compound 3 is the first example of a structurally characterized tolan-titanocene complex without additional ligands.
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  • 62
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 433-436 
    ISSN: 1434-1948
    Keywords: Silicon amidinates ; Germanium amidinates ; Bidentate coordination ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of novel bis(amidinate) silicon and germanium complexes is described. The reaction of two equiv. of [MeC(NiPr)2]Li · THF (1) with SiCl4, GeCl4 or GeCl2·dioxane affords [MeC(NiPr)2]2SiCl2 (2), [MeC(NiPr)2]2GeCl2 (3) and [MeC(NiPr)2]2Ge (4), respectively. The complexes 2 and 4 have been structurally characterized. The crystallographic results confirm a bidentate coordination of the amidinate ligands at the Si/Ge center, as indicated by spectroscopic studies.
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  • 63
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 429-431 
    ISSN: 1434-1948
    Keywords: Osmium ; Thiolate ; Molecular wire ; Molecular devices ; Structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecule (p,p)-HSC6H4C≡CC6H4C≡CC6H5 has been attached to a triosmium cluster and characterized crystallographically. The complex Os3(CO)10(μ-H)(μ-SC6H4C≡CC6H4C≡CC6H5) (1) was obtained in 49% yield from the reaction of the thiol HSC6H4C≡CC6H4C≡CC6H5 with Os3(CO)10(NCMe)2. The sulfur atom bridges two metal atoms on the edge of a triangular cluster of three osmium atoms. The three aryl rings are nearly coplanar. The ligand is 18.27(2) Å in length from the sulfur atom to the para-carbon atom of the third aryl ring. This compound may serve as a model for the coordination of thiol-terminated molecular wires to metallic probe surfaces.
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  • 64
    ISSN: 1434-1948
    Keywords: Lead(1+) ; Indium(3+) ; Organylphosphanylamide complexes ; Phosphazene ; 207Pb-NMR spectra ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of PbCl2 with LiN(PPh2)2 (1) at -78°C affords the P-P coupled phosphazene Ph2P-N=PPh2-PPh2=N-PPh2 (2) as an oxidation product and, as a reduction equivalent, the novel lead(1+) complex [(Pb1+)2(μ-Ph2P···N···PPh2-)2](Pb-Pb) (3). The crystal structure determination of the red compound 3 shows a Pb-Pb bond length of 304.1(1) pm. The 31P- and 207Pb-NMR spectra of 3 are complicated due to the presence of a higher order spin system (AA′A′′A′′′X for the mono-207Pb isotopomer, AA′A′′A′′′XX′ for the bis-207Pb isotopomer). Simulations of the 31P and 207Pb spectra both on material with natural isotope abundance and on the 207Pb-labelled compound (3*) reveal a large Pb,Pb coupling constant of 7708 Hz, indicative of a covalent Pb-Pb bond. - Though InCl3 is diagonally related to PbCl2, no significant redox process is observed in the reaction between InCl3 and 1. The yellow crystals of [In3+(Ph2P···N···PPh2-)3] (4) that are obtained were also investigated by X-ray analysis. These show a propeller-like configuration of the three four-membered chelate rings with indium(3+) as the centre.
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  • 65
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 445-449 
    ISSN: 1434-1948
    Keywords: Cerium(IV) bisporphyrinates ; Sandwich complexes ; Diporphyrins ; π Radical-cations and dications ; Cerium(III) bisporphyrinate anions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Starting from 5-(4-hydroxyphenyl)-10,15,20-tris(4-methylphenyl)porphyrin (2a), the new bis(porphyrinyloxy)alkanes 4a and 4d were synthesized by ether formation with the α,ω-dibromoalkanes Br(CH2)nBr (n = 8, 11; 3a, 3d). 4a was obtained by a two-step reaction with the 5-[4-(8-bromooctyloxy)phenyl]-10,15,20-tris(4-methylphenyl)porphyrin (2b) as an intermediate. The diporphyrins 4a and 4d were metalated with cerium(III) acetylacetonate to yield the new (porphyrin)cerium sandwich complexes 1a and 1d which were characterized by UV/Vis, IR, 1H-NMR, 13C-NMR spectroscopy and cyclic voltammetry. The mono- and dications and the cerium(III) bisporphyrinate anions of 1a-d were produced by electrochemical oxidation and reduction, respectively, and were examined by UV/Vis/NIR spectroscopy. The length of the lateral chains does not have a specific effect on the first and second oxidation potentials of the porphyrin rings and the reduction potentials of the cerium ions in the bisporphyrinate systems, and on the energy of the NIR bands of the monocations.
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  • 66
    ISSN: 1434-1948
    Keywords: Calixarene ; Phosphinite ; Calixphosphane ; Transition metals ; X-ray diffraction ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A cone-shaped calix[4]arene-derived monophosphinite, 25,27-di(ethoxycarbonylmethoxy)-26-hydroxy-28-(diphenylphosphinooxy)calix[4]arene (L1), has been prepared in two steps from calix[4]arene. Treatment of L1 with [AuCl(tetrahydrothiophene)] in tetrahydrofuran gave the phosphinite complex [AuClL1] (1). Reaction of [PdCl2(PhCN)2] with two equivalents of L1 gave selectively trans-[PdCl2L12] (2). Complex 2 · 2 CH2Cl2 crystallizes in the triclinic space group P1¯. The molecule is centrosymmetric, leading to a divergent array of the two calixarene moieties. The palladium atom resides outside both cones. As a result of steric interactions, the meta and para carbon atoms of the PPh2-bearing aryl ring are significantly pushed to the interior of the cavity. The related platinum complex trans-[PtCl2L122] (3), was obtained similarly from [PtCl2(PhCN)2] and presents in the solid state a structure which is isomorphous to that of 2. The diphosphinite 25,27-di(ethoxycarbonylmethoxy)-26,28-bis(diphenylphosphinoxy)calix[4]arene (cone) (L2) has also been prepared and reacts with [PtCl2(PhCN)2] to yield oligomeric material.
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  • 67
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 459-463 
    ISSN: 1434-1948
    Keywords: 1,2-Diboraheterocycles ; Carbon monoxide insertion ; Isonitrile insertion ; Dimerisation ; Spiro insertion products ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The insertion of CO into the B-B bond of 1,2-bis(diisopropylamino)-2,5-dihydro-1H-1,2-diborole (1b) and 1,2-bis(diisopropylamino)-3-methylidene-1,2-diborolane (1c) leads to the dimeric spiro products 1,7,9,14-tetrakis(diisopropylamino)-6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4.2]tetradeca-2,10-diene (4b) and 1,7,9,14-tetrakis(diisopropylamino)bismethylidene-6,13-dioxa-1,7,9,14-tetraboradispiro[4.2.4.2]tetradecane (4c). Insertions of CO into the B-B bonds of the cyclic organo-1,2-diborane compounds 5, 6, and 7 are not observed. The reaction of 1b with tert-butyl isocyanide and 2,6-dimethylphenyl isocyanide in THF leads to the formation of the monomeric insertion products 1,3-bis(diisopropylamino)-2-tert-butylimino-1,3-diboracyclohex-4-ene (10b) and 1,3-bis-(diisopropylamino)-2-(2′,6′-dimethylphenylimino)-1,3-diboracyclohex-4-ene (11b). The treatment of 1cwith the isonitriles yields 2-tert-butylimino-1,3-bis(diisopropylamino)-4-methylidene-1,3-diboracyclohexane (10c) and 1,3-bis(diisopropylamino)-2-(2′,6′-dimethylphenylimino)-4-methylidene-1,3-diboracyclohexane (11c). The steric requirements of the isonitrile insertion products 10b, c and 11b, c prevent their dimerisation and rearrangement. 11b rearranges to 1-(diisopropylamino)-2-(diisopropylaminohydroxyboryl)-2-(2′,6′-dimethylphenylamino)-1-boracyclopent-3-ene (12b) upon reaction with water from sodium sulfate decahydrate. The compositions of the compounds are derived from the 1H-, 11B-, 13C-NMR data as well as from mass-spectral and C, H, N analyses. In the cases of of 4b and 12b they have been proven by X-ray structure analyses.
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  • 68
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 465-468 
    ISSN: 1434-1948
    Keywords: Boron ; Iron ; Boryl complexes ; Borylene complexes ; Iron-boron bond ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Depending on the nature of the amino group bound to the boron atom, the reactions of various aminodichloroboranes R2NBCl2 with Na[(η5-C5R′5)Fe(CO)2] yield either boryl or bridging borylene complexes of iron. The compounds [(C5R′5)(CO)2Fe{BCl(NR2)}] (1a, C5R′5 = C5H5, R = Me; 1b, C5R′5 = C5H4Me, R = Me; 1c, C5R′5 = C5Me5, R = Me) and [(η-BNR2)(μ-CO){(C5R′5)Fe(CO)}2] (2a, C5R′5 = C5H5, R = SiMe3; 2b, C5R′5 = C5H4Me, R = SiMe3) were isolated as orange (1a-c) or red (2a, b) crystalline solids, and characterized by multinuclear NMR methods and IR spectroscopy. The structures of 1c and 2b in the crystalline state were determined by single-crystal X-ray studies.
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  • 69
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    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 469-476 
    ISSN: 1434-1948
    Keywords: Cage compounds ; Crystal structure ; Hafnium ; Trimetaphosphimates ; Zirconium ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (trimetaphosphimato)hafnates and -zirconates Na4{Hf4(μ4-O)(μ-OH)6[(PO2NH)3]4} · 18 H2O [1, Pa3, a = 22.687(3) Å, Z = 8], Na4{Hf4(μ4-O)(μ-OH)6[(PO2NH)3]4} · 21 H2O [2, R3, a = 14.350(2), c = 50.348(10) Å, Z = 6], Na4{Zr4(μ4-O)(μ-OH)6[(PO2NH)3]4} · 18 H2O [3, Pa3, a = 22.693(3) Å, Z = 8], and Na4{Zr4(μ4-O)(μ-OH)6[(PO2NH)3]4} · 21 H2O [4, R3¯, a = 14.303(2), c = 50.284(10) Å, Z = 6] were obtained by the stoichiometric reaction of HfOCl2 · 8 H2O and ZrOCl2 · 8 H2O with an aqueous solution of Na3(PO2NH)3 · 4 H2O, followed by the diffusion-controlled addition of methanol. During these reactions compounds 1 and 2, or 3 and 4, crystallized simultaneously and the hafnium and zirconium complexes 1 and 3, as well as 2 and 4, were found to be isostructural and isomorphous. The characteristic structural feature which is central to 1, 2, 3, and 4 is the complex tetranuclear anion {M4(μ4-O)(μ-OH)6[(PO2NH)3]4}4- with M = Zr or Hf. The anion consists of five corner-sharing adamantanoid cages. The central cage, {M4(μ4-O)(μ-OH)6}8+, has a tetracoordinated oxygen atom in the middle, and the other cages are formed by the trimetaphosphimate ions acting as tridentate ligands which coordinate to Hf or Zr. The water content of the compounds 1-4 could not be determined unequivocally by chemical analyses since the compounds are always obtained as mixtures of the rhombohedral (2/4) and cubic (1/3) phases. Thermal decomposition of compounds 1-4 starts above 120°C and leads to the formation of HfP2O7 and ZrP2O7/NaZr2(PO4)3, with the evolution of H2O and NH3. DSC measurements gave no evidence that the compounds 1 and 2, or 3 and 4, might be transformed into each other by heating.
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  • 70
    ISSN: 1434-1948
    Keywords: Ruthenium ; Bridging bis(bidentate)tetraphosphane ligand ; Diruthenium(II) coordination complex ; Cyclometallation versus o-P,P′ chelation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The tetrakis(phosphane oxide) C6H2{CH2P(O)Ph2}4-1,2,4,5 (5), has been prepared in high yield from the Arbuzov reaction of C6H2(CH2Br)4-1,2,4,5 (4), with excess (7 equiv.) of Ph2POEt. Subsequent reduction of 5 with HSiCl3 (12 equiv.) in C6H4Cl2-1,2 afforded the new tetraphosphane C6H2(CH2PPh2)4-1,2,4,5 (6), in high yield. The reaction of 6 with [RuCl2(PPh3)4] in CH2Cl2 afforded the green dinuclear ruthenium(II) coordination complex [{RuCl2(PPh3)}2{C6H2- (CH2PPh2)4-1,2,4,5-P,P′,P′′,P′′′}]·0.5 CH2Cl2 (8), in 39% isolated yield. The solid-state molecular geometry of 8, determined by X-ray analysis, shows that the tetraphosphane is ortho-P,P′-chelated to each of the two [RuIICl2(PPh3)] units.
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  • 71
    ISSN: 1434-1948
    Keywords: Heterobimetallics ; μ-Isonitrile complexes ; μ-Aminocarbyne complexes ; Bis(diphenylphosphanyl)amine ; Iron ; Platinum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition of isonitriles to [(OC)3Fe(μ-CO)(μ-Ph2PNHPPh2)Pt(PPh3)] 1 produces the μ-isonitrile complexes [(OC)3Fe(μ-C=NR)(μ-Ph2PNHPPh2)Pt(PPh3)] 2, which are transformed to the μ-aminocarbyne complexes [(OC)3Fe{μ-CN(El)R}(μ-Ph2PNHPPh2)Pt(PPh3)]+;3 and 4 by electrophilic addition of [El][BF4] or [El][OSO2CF3] (El = H, Me). The dppa backbone of 4 is readily deprotonated by KOSiMe3 to yield the very stable zwitterionic aminocarbyne complex [(OC)3Fe{μ-CN(Me)2,6-xylyl}(μ-Ph2PNPPh2)Pt(PPh3)] 5.
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  • 72
    ISSN: 1434-1948
    Keywords: 2-Phenyl-4-R-5(4H)-oxazolones ; Iridium ; Palladium ; Platinum ; Iron ; Chromium ; C-o,N-Bridging 2-phenyloxazolone ; Peptide labelling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reactions of 2-phenyl-4-R-5(4H)-oxazolones (R = Me, CH2Ph, CHMeEt) with [(η5-C5Me5)IrCl2]2 afforded the cyclometallated complexes (η5-C5Me5)(Cl)Ir(L) (1-3) [L = 2-phenyl-4-R-5(4H)-oxazolone(C-o,N)]. 2-Phenyl-5(4H)-oxazolone reacts with [(η5-C5Me5)IrCl2]2 and palladium(II) acetate to give complexes with a C-o,N-bridging oxazolone [(η5-C5Me5)(Cl)Ir]2(μ-Cl)(μ-L-H+) (4) and Pd3(μ-ac)5(μ-L-H+) (5). 2-Phenyloxazolone anions were added to the π ligands of [(η5-C6H7)Fe(CO)3]+ and [(η7-C7H7)Cr(CO)3]+ to give the adducts 6-11. Dipeptide derivatives 12-18 were obtained by reaction of 1, 2 and by reaction of the adduct 6 from [(η5-C6H7)Fe(CO)3]+; and the anion of 2-phenyloxazolone with α-amino acid esters. These reactions may be used for the labelling of peptides. Saponification of 15-18 yields the organometallic substituted peptide acids 19-22. Their dianions (deprotonation of COOH and peptide amide) were used as ligands towards (Ph3P)2PtCl2 to yield the bimetallic complexes 23-25. The structures of 4, 5, 9 and 10 were determined by X-ray diffraction.
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  • 73
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 501-504 
    ISSN: 1434-1948
    Keywords: Metallomesogens ; Azo compounds ; Palladium ; Platinum ; Cyclopentadienyl complexes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The mesogenic 4,4′-bis[4-(n-octyloxy)benzoyloxy]azobenzene (HL) ligand reacts with [(PhCN)2PdCl2] to give the dinuclear cyclometalated complex [(μ-Cl)(L)Pd]2 (1), from which the mononuclear half-sandwich [(η5-C5H5)(L)Pd] (2) species has been obtained by reaction with Tl(C5H5). The PtII analogue of 2, [(η5-C5H5)(L)Pt] (4), has been prepared in a similar manner starting from [(μ-Cl)(L)Pt]2 (3). Both dinuclear complexes 1 and 3 display a smectic C phase (SC) stable over 80°C. Whereas 4 is the first example of an 18-electron PtII mesogen, both mononuclear 2 and 4 are mesomorphic materials that exhibit a nematic phase spanning a wide temperature range.
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  • 74
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    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 505-509 
    ISSN: 1434-1948
    Keywords: Chlorobis(dimethylamino)(3-indenyl)diborane(4) ; Bis(dimethylamino)bis(1-indenyl)diborane(4) ; Bis(dimethylamino)(1-indenyl)(3-indenyl)diborane(4) ; Bis(dimethylamino)bis(3-indenyl)diborane(4) ; Rearrangement ; X-ray structures ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Indenyllithium reacts with dichlorobis(dimethylamino)diborane(4) with formation of bis(dimethylamino)bis(1-indenyl)diborane(4) which rearranges on heating to the isomer bis(dimethylamino)bis(3-indenyl)diborane(4). The „mixed” bis(dimethylamino)(1-indenyl)(3-indenyl)diborane(4) is obtained from indenyllithium and chlorobis(dimethylamino)(3-indenyl)diborane(4). The main structural differences between the two isomers 3 and 4 are a slightly shorter B-B bond in 4, as well as a stronger twist about the B-B bond (89.9° vs. 67.4°) and, as expected, a shorter B-C bond. There is, however, no significant B-C π bonding.
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  • 75
    ISSN: 1434-1948
    Keywords: Gold(I) ; Silver(I) ; S-donor and N-donor ligand ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ligand properties of 2-(phenacylthio)pyridine towards gold(I) and silver(I) have been investigated. From the reactions of the ligand with acetone solutions of [M(PPh3)(acetone)]ClO4 (M = Ag, Au) under various experimental conditions, complexes [(AuPPh3)n{py{SCH2C(O)Ph}-2}](ClO)n, and [(AgPPh3)n(OClO3)n{py{SCH2C(O)Ph}-2}](n = 1-3) have been obtained. The crystal structures of the complexes [(AuPPh3){py{SCH2C(O)Ph}-2}]ClO4 and [(AgPPh3)(OClO3){py{SCH2C(O)Ph}-2}] have been determined by X-ray diffraction. In the cationic gold complex the metal is linearly coordinated to nitrogen and phosphorus, whereas the corresponding silver complex displays a trigonal planar geometry with pyridine, phosphane and perchlorato ligands.
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  • 76
    ISSN: 1434-1948
    Keywords: Bis(silyl)phosphanes ; Magnesium ; NMR spectroscopy ; Oligomers ; Phosphorus ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The metathesis reaction of (dme)LiPH2 and chlorodiisopropylsilane yields HP(SiHiPr2)2 (1) and P(SiHiPr2)3 (2). The metalation of 1 by n/sec-dibutylmagnesium in heptane leads to the formation of dimeric magnesium bis[bis(diisopropylsilyl)phosphanide] [(3)2]. A toluene solution of magnesium bis[bis(trimethylsilyl)phosphanide] (4) shows a dimer-trimer equilibrium in the 31P{1H}-NMR spectrum at -40°C with an increasing amount of the dimer with increasing temperature. A molecular mass determination by freezing-point depression in benzene yields a value of 516 g·mol-1, which lies between a monomeric and a dimeric molecule. Cooling of the toluene solution to -30°C leads to the precipitation of single crystals of monoclinic {(Me3Si)2P-Mg[μ-P(SiMe3)2]2}2Mg [(4)3].
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  • 77
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 523-536 
    ISSN: 1434-1948
    Keywords: Quantum chemistry ; Intermetallic compounds ; Transition metal cluster compounds ; Crystallography ; Electronic structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The “coloring problem,” as applied to the field of solid state chemistry, addresses the issues of structural preference as well as the distribution of different elements within a given structure. Both the connectivity and arrangement of elements in a solid affect physical and chemical properties, so a clear understanding of the forces controlling how elements will arrange themselves in a solid state structure creates the ability to predict structure-composition-property relationships. There are two fundamental energetic contributions that influence how elements in a structure order: the site energy and the bond energy. This review examines how these two parts of the total electronic energy work together to influence the observed structures, compositions, and properties of intermetallics and transition metal cluster compounds.
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  • 78
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 537-541 
    ISSN: 1434-1948
    Keywords: Lithium ; (Benzene)lithium complex ; (Carbonyl)lithium complex ; Ab initio calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complexes of CO and aromatic compounds were believed to be an exclusive domain of transition metals caused by their ability of backbonding to these ligands. But recently, (benzene)lithium and (carbonyl)lithium complexes were characterized by X-ray structure analysis and IR spectoscopy. In order to determine geometries of the complexes and the bonding energies of the benzene and CO molecule to the organolithium starting compound suitable models were chosen in combination with high-level ab initio calculations. For the carbonyl derivative a reaction enthalpy of -8 kcal/mol was found while the interaction with benzene reached unexpectedly -21 kcal/mol. This underlines the ability of lithium to act like a transition metal in subcoordinated organyl compounds without having d orbitals available for bonding.
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  • 79
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 543-545 
    ISSN: 1434-1948
    Keywords: Lanthanoid(II) complexes ; Ytterbium ; Thallium ; η2-Pyrazolate complexes ; Diphenylmercury ; Redox transmetallation ; X-ray crystal structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ytterbium metal reacts with thallium(I) 3,5-diphenylpyrazolate, or with diphenylmercury and 3,5-diphenylpyrazole (Ph2pzH) in tetrahydrofuran or 1,2-dimethoxyethane (DME) giving, after appropriate isolation, the first lanthanoid(II) pyrazolate complex, [Yb(Ph2pz)2(DME)2]. The molecular structure reveals eight coordinate ytterbium(II) with two cisoid η2-3,5-diphenylpyrazolate and two chelating 1,2-dimethoxyethane ligands.
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  • 80
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 547-549 
    ISSN: 1434-1948
    Keywords: Copper ; Trinuclear ; Formamidines ; Magnetism ; Crystal structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In situ reaction of CuII triflate with aminopyridine or aminopyrimidine and triethylorthoformate in ethanol results in unique linear trinuclear CuII complexes with the general formula [Cu3(L-)4](CF3SO3)2(EtOH)x (L = dehydronated ligand N,N′-bis(pyridine-2-yl)formamidine or the new ligand N,N′-bis(pyrimidine-2-yl)formamidine). The structure [Cu-Cu-Cu angle 175.19(2)°] consists of four nearly flat molecules of the ligand which contribute to the propeller-type structure around the Cu-Cu-Cu axis. A strong antiferromagnetic interaction between the CuII ions is observed, resulting in an S = 1/2 ground state below 100 K.
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  • 81
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 559-563 
    ISSN: 1434-1948
    Keywords: Metal(II) complexes ; Octanuclear complexes ; Supramolecular chemistry ; Zinc ; Cadmium ; Manganese ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of H2L1 and H2L2 with divalent metal ions leads to octanuclear bis(triple-helical) metal(II) complexes of the general composition [Zn8O2L26] (3) and [M8O2L16] (4: M = Cd2+; 5: M = Mn2+). NMR studies of the diamagnetic cadmium complex 4c show six equivalent ligands. Unambiguous characterisation of 5b was achieved by X-ray crystallographic analysis.
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  • 82
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 551-558 
    ISSN: 1434-1948
    Keywords: Planar-tetracoordinate carbon ; Zirconocene ; Acetylide complex ; Selective protonation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(alkynyl)zirconocene and -hafnocene complexes 4 react with (butadiene)zirconocene or -hafnocene, respectively, to yield the binuclear σ,π-acetylide bridged complexes [(Cp2M)2(μ-C≡C-R)2] 7 (M = Zr, Hf; R = CH3, C2H5, or CH2Ph). The complexes 7 are selectively protonated upon treatment with N,N-dimethylanilinium tetraphenylborate or tetrakis(pentafluorophenyl)borate to yield the dinuclear metallocene cation complexes [(Cp2M1)(μ-RCC1-H)(μ-C≡C-R)M2Cp2+] 13 (M1 = M2 = Zr, a-c; M1 = Zr, M2 = Hf, h; M1 = M2 = Hf, i) that contain a planar-tetracoordinate carbon atom (C1-H) bearing a hydrogen substituent. Complex 13a was characterized by X-ray diffraction. It reveals an agostic interaction of the C1-H moiety with the M2Cp2 unit. The planar-tetracoordinate carbon unit C1-H of 13a exhibits 13C/1H NMRchemical shifts of δ = 161.0 and -0.11 and a coupling constant of 1JCH = 103 Hz. Selective protonation of (μ-alkynyl)bis(group 4 metallocene) complexes containing other additional bridging ligands provides a rather general synthetic entry to planar-tetracoordinate carbon containing complexes of this type: [Cp2M1(μ-C≡C-CH3)(μ-Cl)M2Cp2] (10a-c, M1, M2 = Zr, Hf) and[Cp2M1(μ-C≡C-CH3)(μ-CH3)M2Cp2] (11a,b) selectively add a proton from [(HNMe2Ph)+(BAr4)-] at carbon atom C1 of the acetylide ligand to yield the corresponding “anti-van′t Hoff/LeBel complexes” [Cp2M1(μ-CH3CC1-H)(μ-X)M2Cp2+] (13d-g and k, X = Cl, CH3), respectively.
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  • 83
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 571-574 
    ISSN: 1434-1948
    Keywords: Phosphorus heterocycles ; 2H-Azaphosphirene complexes ; Carbene complexes ; Chromium ; Molybdenum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 3-phenyl-substituted 2H-azaphosphirene pentacarbonylchromium and pentacarbonylmolybdenum complexes is reported. New information on the rearrangement cascade, which finally leads to 2H-azaphosphirene ring formation, has been obtained through isolation of a reactive intermediate. A comparison of the 13C-, 15N-, 31P-NMR, and UV/vis spectroscopic data and single crystal X-ray structural data of 3-phenyl-substituted 2H-azaphosphirene chromium, molybdenum, and tungsten complexes is presented.
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  • 84
    ISSN: 1434-1948
    Keywords: Equilibrium ; Metal-metal bond ; Stability constants ; Platinum ; Thallium ; NMR ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new series of four binuclear platinum-thallium cyano compounds containing a direct and unsupported by ligands metal-metal bond has been prepared in aqueous solution. These compounds are represented by the formula[(NC)5Pt-Tl(CN)n-1](n-1)- (n = 1-4 for compounds I, II, III IV, respectively) and [(NC)5Pt-Tl-Pt(CN)5]3- (for compound V). The oligonuclear complexes are synthesised according to the reaction mPt(CN)42- + Tl3+ + nCN- █[PtmTl(CN)4m+n]3-2-n. Thus, there occurs a change of the coordination number of the Pt center from four (square planar) to six (octahedral). Consequently, the formation of binuclear platinum-thallium cyano compounds involves at least two steps: (i) formation of metal-metal bond and (ii) formation of (NC)5Pt- unit by a cyanide transfer process. - The complexes exist in an equilibrium, which also includes the parent complexes Pt(CN)42- and Tl(CN)n3-n (n = 0-4), and can be controlled by varying the cyanide concentration and/or pH of the solution. The stability constants of the compounds βN =[PtmTl(CN)4m+n3-2m-n{[Pt(CN)42-]m · [Tl3+] · [CN-]n} have been determined by means of multinuclear NMR (195Pt, 205Tl): logβN = 19.9±0.4, 30.7±0.3, 38.6±0.3, and 44.8±0.2 for I, II, III and IV(m = 1, n = 1-4), and 32.1±0.3 for V(m = 2, n = 2), respectively, (in 1 M NaClO4 as ionic medium, at 25 oC). To our knowledge, the present work constitutes the first detailed equilibrium study of metal-metal bonded compounds; it indicates that also other cluster formation reactions described in the literature may represent real equilibria.
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  • 85
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 575-578 
    ISSN: 1434-1948
    Keywords: Phosphorus heterocycles ; 2H-Azaphosphirene complexes ; Carbene complexes ; Tungsten ; Cyclizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The syntheses of 3-heteroaryl-substituted 2H-azaphosphirene pentacarbonyltungsten complexes are reported. The products were characterized by multinuclear NMR spectroscopy (1H, 13C, 15N, 31P, 183W); the structure of the 3-N-methylpyrryl-substituted 2H-azaphosphirene complex was determined by single-crystal X-ray structure analysis.
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  • 86
    ISSN: 1434-1948
    Keywords: Carbyne complexes ; Molybdenum complexes ; Oxidations ; Tungsten ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Oxidation of the phosphaalkenyl-substituted carbyne complexes [Tp′(CO)2M≡C-P=C(NR2)2] (1a: M = Mo, R = Me; 1b: M = W, R = Me; 2a: M = Mo, R = Et; 2b: M = W, R = Et) with molecular dioxygen cleanly affords the orange carbyne complexes [Tp′(CO)2M≡C-P(O)2C(NR2)2] [3a: M = Mo, R = Me; 3b: M = W; R = Me; 4a: M = Mo, R = Et; 4b: M = W, R = Et; Tp′ = HB(3,5-Me2HC3N2)3], which are functionalized at the methylidyne carbon atom by an α-carbenium phosphinate moiety. The novel compounds have been characterized by IR, 1H-, 13C-, and 31P-NMR spectroscopy. In addition, the molecular structure of 4a has been determined by a single-crystal X-ray structure analysis.
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  • 87
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 593-596 
    ISSN: 1434-1948
    Keywords: Yttrium ; Aminotroponiminate ; Cyclopentadienyl ; Dynamic NMR ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mixed aminotroponiminate ([ATI]-) cyclopentadienyl complexes were prepared using two different synthetic routes. Reaction of [[(iPr)2ATI]YCl2(THF)2]2 (1) with KCp* (Cp* = C5Me5) or Li[C5H3(SiMe3)2] affords [(iPr)2ATI]YCp2* (2a) and [(iPr)2ATI]Y[C5H3(SiMe3)2]2 (2b), respectively. Moreover, [(iPr)2ATI]YCp2* has also been obtained from the reaction of Cp2*Y(μ-Cl)2Li(OEt2)2 (3) and [(iPr)2ATI]K. The single crystal X-ray structure of [(iPr)2ATI]YCp2* shows that the steric demand of the [(iPr)2ATI]- ligand is somewhat similar to that of the well-known cyclopentadienyl group and diazadiene ligand. [(iPr)2ATI]Y[C5H3(SiMe3)2]2 shows a dynamic behavior in solution (1H NMR), which is essentially caused by rotation of the cyclopentadienyl group rather than by migration of the [(iPr)2ATI]- ligand.
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  • 88
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 583-591 
    ISSN: 1434-1948
    Keywords: Cytochrome c ; Hyperfine shift ; Magnetic susceptibility anisotropy ; NMR spectroscopy ; Heme proteins ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The binding of ammonia to oxidized horse heart cytochrome c has been studied by 1H-NMR, EPR, and CD spectroscopy at pH = 8.0. The affinity constant of the ligand is in the range 1.5-4 M-1. The 1H-NMR spectra of the heme group have been found to be similar to those of the high-pH forms, high-temperature forms, and cyanide adduct of the Met80Ala mutant of S. cerevisiae iso-1-cytochrome c. The assignment of a number of signals has led to the determination of the values of the magnetic anisotropy and of the orientation of its axes. The latter are similar to those of the Met80Ala cyanide derivative. The assignment of the high-temperature species has been further pursued during this research. The analysis of the NMR data of the NH3 adduct leads to the conclusion that substitution of Met80 at high pH or high temperature occurs through a ligand with cylindrical symmetry. This supports the suggestion that Met80 is substituted by a lysine at high pH.
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  • 89
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 597-603 
    ISSN: 1434-1948
    Keywords: Chirality ; P ligands ; Nickel ; Palladium ; Platinum ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Radical-initiated P-H addition of (1S,2S)-C5H8(PH2)2 to cycloalkenes gave bis(secondary phosphanes), (1S,2S)-C5H8[P(H)CnH2n-1-cyclo]2 (n = 5-8), as mixtures of RP,RP′, SP,SP′, and RP,SP′ diastereomers. The three diastereomers of the peralkylated chiral P2 ligand (1S,2S)-C5H8[P(CH3)C8H15-cyclo]2 and its complexes with NiCl2, PdI2, and PtI2 were prepared. The structures of [(1S,2S)-C5H8{P(CH3)C8H15-cyclo(R)}2NiCl2] · [(1S,2S)-C5H8{P(CH3)C8H15-cyclo-(S)}2NiCl2],(1S,2S)-C5H8{P(CH3)C8H15-cyclo-(R)}2PdI2, and (1S,2S)-C5H8{P(CH3)C8H15-cyclo-(R)}2PtI2 were determined by X-ray diffraction.
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  • 90
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 605-611 
    ISSN: 1434-1948
    Keywords: Enolates ; Nucleophilic additions ; Ruthenium ; S ligands ; Sulfenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Sulfene complexes [CpRu(PR′3)2(RHC=SO2)]PF6 (2a-d) are obtained from the corresponding sulfur dioxide complexes 1a-c and diazomethane or -ethane. Reaction of [CpRu(dppm)(SO2)]Cl (1d) and phenyldiazomethane gives the chlorobenzylsulfinato complex [CpRu(dppm)(SO2CHPhCl)] (3). Alternatively, 2a may be synthesized by sulfur dioxide addition to the carbene complex [CpRu(dppm)(CH2)]PF6 (5) which, in turn, is obtained from the corresponding methyl complex [CpRu(dppm)(CH3)] and [Ph3C]PF6. Treatment of 2a-d or 3 with the enolates of cyclic 2-methyl-1,3-diketones, methyl malonates, open-chain cyano or β-oxo esters, and cyclic β-oxo esters gives the C-C coupling products 6a, b, 7a-e, 8a-c, 9a-c in high yields and, in one case, with high diastereoselectivity as well. The functionalized sulfinate ligands thus formed may be alkylated and subsequently removed from the metal center by ligand substitution with acetonitrile. After MeCN/SO2 exchange, the ruthenium complex can be recycled.
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  • 91
    ISSN: 1434-1948
    Keywords: Dihydroxybiphenyl ; Iron chelation ; Formation constants ; Protonation constants ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new water-soluble iron(III) sequestering agent has been designed. The tris-bidentate tripodal ligand consists of three 2,2′-dihydroxybiphenyl subunits connected via amide linkages at their meta (4-) positions to a framework of the “tren” type. The key step of the synthesis involves the coupling of suitably substituted monophenyl moieties in order to obtain the biphenyl precursor. The deprotonation constants of the ligand, and the formation and deprotonation constants of the FeIII complex have been determined from potentiometric and spectrophotometric measurements. The results are compared with those of a previously described homologous ligand in which the chelating subunits are attached to the tren framework via the ortho (3-) position of the biphenyl rather than the 4-position.
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  • 92
    ISSN: 1434-1948
    Keywords: Nickel ; Oxidation ; Phenols ; Structure ; Dynamic NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of substituted phenols and dioxygen with Ni(PMe3)4 yields the low-spin tetracoordinate diphenolatonickel compounds Ni(OAr)2(PMe3)2 [ArOH = 2-tert-butylphenol (1), 2-tert-butyl-4-methylphenol (2), 2-tert-butyl-6-methylphenol (3), 2,4-di(tert-butyl)phenol (4), 2-tert-butyl-4-methoxophenol (5), 2-chloro-4-tert-butylphenol (6), 2-isopropylphenol (7), 3-tert-butylphenol (8)]. As is revealed by variable temperature 1H- and 13C-NMR spectroscopy the complexes constitute a mixture of two isomers, each of which can be observed separately at lower temperatures when interconversion is slower. An additional 6-carbaldehyde function transforms the phenolate into a chelating ligand, giving rise to a high-spin hexacoordinate compound Ni(OAr)2(PMe3)2 (9). X-ray crystal-structure determinations of 2 and 3 show a trans square-planar structure, and that of 9 shows a trans octahedral arrangement of donor atoms P2O4. Bulky substituents in the 3- or 4-position, or non-demanding substituents in the 2-position, are less effective in stabilizing molecular diphenolatonickel complexes.
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  • 93
    ISSN: 1434-1948
    Keywords: Alkyne complexes ; Carbonyl complexes ; Cobalt ; CO replacement ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of dicarbonyl(η5-cyclopentadienyl)cobalt (1) and some of the Cp-ring substituted congeners with bis(tert-butylsulfonyl)acetylene (BTSA) results in the replacement of one CO group by the BTSA moiety. The variation of the yields and reaction times indicates a dependence of the reactivity of 1-6 with BTSA as a function of substituents. X-ray investigations of the products show that the alkyne unit is strongly bound to the metal.
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  • 94
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 633-637 
    ISSN: 1434-1948
    Keywords: Ab initio calculations ; Boron ; Carboranes ; NMR spectroscopy ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydroboration of diethyl(1-propynyl)borane 1 with tetraethyldiborane(6) in the presence of a catalytic amount of trimethyl- or tributyltin chloride gave two new organo-substituted carboranes 6 and 7 with 2,3,5-tricarba-nido-hexaborane(7) and 2,3,4-tricarba-nido-hexaborane(7) skeletons, respectively, along with polymeric material and the known organo-substituted 1-carba-arachno-pentaborane(10) (3) and pentaethyl-1,5-dicarba-closo-pentaborane(5) (4). Selective 11B(5,6) decoupled 13C-NMR spectra indicate an unprecedented B(5)-ethyl-B(6) bridge in 7. This structure is supported by the agreement between experimental and calculated 11B- and 13C-chemical shifts on a model compound 7d with methyl groups in the 1,2,3,5,6-positions and an ethyl group bridging B(5) and B(6).
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  • 95
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 645-650 
    ISSN: 1434-1948
    Keywords: Aziridines ; Coordination ; Ring opening ; Metallacycle ; N-Chirality ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The photolytically induced CO substitution reactions of CpMn(CO)3 with N-phenylaziridine and of W(CO)6 with 2,2-dimethylaziridine lead to the N-coordinated aziridine complexes Cp(CO)2Mn{N(Ph)CH2CH2} and (CO)5W{N(H)CH2CMe2}. Both are stable with respect to thermal alkene elimination. The thermal reaction of Cp(CO)3MoCl with N-hydroxyethylaziridine leads to the metallaheterocyclic compound Cp(CO)2MoNH(CH2CH2OH)CH2CH2C(O). It might be formed by several reaction steps including a Cl migration with nucleophilic ring opening, a CO insertion reaction forming the β-aminoacyl ligand and finally a hydrolytic process. The X-ray structure analysis of Cp(CO)2Mn{N(Ph)CH2CH2} and (CO)5W{N(H)CH2CMe2} shows three-membered-ring ligands N-bonded to the metal atoms with a trigonal pyramidal configuration at the nitrogen atoms. The X-ray structure analysis of Cp(CO)2MoNH(CH2CH2OH)CH2CH2C(O) reveals a five-membered heterocyclic ring system, including the molybdenum atom, a carbonyl function and an ammonium center.
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  • 96
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    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 639-644 
    ISSN: 1434-1948
    Keywords: Manuscripts ; Scriptoria ; TXRF ; Micro-Raman spectroscopy ; Pigments ; Middle ages ; Azurite ; Gold initials ; Workshops ; Renaissance ; Mercatellis ; Codicology ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Assigning related medieval manuscripts to different workshops on the basis of codicological characteristics, is not straightforward. We present the first attempt to distinguish between scriptoria by means of a large-scale total reflection X-ray fluorescence (TXRF) analysis of pigment elements and an identification of pigment molecules with micro-Raman spectroscopy. We analyzed 324 colored items in 10 medieval manuscripts, of which 7 are folio-sized illuminated manuscripts, all ordered by Raphael de Mercatellis in the late 15th and early 16th century. Palettes in miniatures were not yet examined. Blue palettes are exclusively azurite-based and are easily differentiated by means of the respective amounts of Ti, Ba, and As. Differences for green palettes are also pronounced. The green Cu-based pigment was not yet identified, but it certainly is not malachite or verdigris. Red pigments used are HgS, vermilion, and Pb3O4, red lead. The Flemish gold-leaf technique is used. The 7 Mercatellis manuscripts show two different palettes, both different from the non-Mercatellis manuscripts. The grouping of the Mercatellis manuscripts according to date and to palettes is, in general, consistent with a grouping on the basis of a classical codicological analysis, although some conflicting results are obtained. A quantitative and qualitative reconstruction of palettes by means of TXRF- and Raman-spectra, provides with a complimentary and objective tool for distinguishing between scriptoria.
    Type of Medium: Electronic Resource
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  • 97
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 651-656 
    ISSN: 1434-1948
    Keywords: Secondary carbaboranyldiphosphane ; Transition-metal complexes ; Crystal structure ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When a mixture of stereoisomers of rac- and meso-1,2-bis(phenylphosphanyl)-1,2-dicarba-closo-dodecaborane(12) (1a, b; 1a/1b = 3:1) is treated with [Cp2ZrMe2] in boiling toluene for 2 h, the formation of three phosphorus-containing products, namely meso-[Cp2Zr(PPh)3] (3), (PPh)4 (4) and (PPh)5 (5), ratio 2.8:1.1:1.0, was observed by 31P-NMR spectroscopy. In the 11B-NMR spectrum of the reaction mixture, only signals for 1,2-dicarba-closo-dodecaborane(12) were observed. When zirconocene, prepared in situ from [Cp2ZrCl2] and BuLi, was treated with 1a, b at low temperature and then heated to reflux in toluene for 2 h, only formation of 3 and 1,2-dicarba-closo-dodecaborane(12) was observed. The mixture of stereoisomers of 1a, b reacts with CuCl in THF to give rac- and meso-[CuCl(THF){1,2-(PHPh)2C2B10H10}] (7a, b), which is only stable in THF solution and loses THF in vacuo over several hours to yield the insoluble colorless complex [CuCl{1,2-(PHPh)2C2B10H10}]n (8). In THF solution, 7 reacts with PPh3 to give the stable isolable complex [CuCl(PPh3){1,2-(PHPh)2C2B10H10}] (9). No reaction of 1a, b is observed with [Cp′Mo(CO)3]2 (Cp′ = C5H4Me) in boiling THF, while only decomposition occurs in boiling toluene. However, [(NBD)Mo(CO)4] (NBD = norbornadiene) reacts smoothly with 1a in toluene at room temperature to give cis-rac-[Mo(CO)4{1,2-(PHPh)2C2B10H10}] (10). Compounds 7, 9, and 10 were characterized spectroscopically (1H, 31P, 11B, 13C NMR, IR), and an X-ray structure determination was carried out on 10.
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  • 98
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 657-662 
    ISSN: 1434-1948
    Keywords: Cadmium ; Crown compounds ; Pentafluorophenyl ; Potassium ; S ligands ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Bis(pentafluorophenyl)cadmium, [Cd(C6F5)2], reacts with equimolar amounts of triphenylmethanethiol, TrtSH, in toluene to give [{Cd(C6F5)(STrt)}4] · 1.5 tol (1). The cuboidal complex of 1 has been transformed into the heterometallic cuboidal complex [{Cd(C6F5)(STrt)}3(OH)K(THF)3] (2) by reaction with KOH in tetrahydrofuran. In the presence of 18-crown-6, the compound [K(18-crown-6)(THF)2][{Cd(C6F5)- (STrt)}3(OH)] · THF (3) has been obtained instead of 2. X-ray structure analysis shows the anion of 3 to be an incomplete cuboidal complex, which alternatively can be described as a cyclic trimer of the {Cd(C6F5)(STrt)} unit stabilized by a μ3-hydroxo ligand. The compound [K(18-crown-6)(THF)2][Cd(C6F5)(STrt)2] (4) has been isolated from reaction mixtures containing 1, KSTrt and 18-crown-6. The cadmium atom in 4 is three-coordinated, in contrast to the cadmium atoms in 1-3, which are situated in strongly distorted coordination tetrahedra. Intramolecular C6H5···C6F5···C6H5 stacks in 4 are interpreted as resulting from attractive ligand-ligand interactions. Spectroscopic data, particularly from 13C-NMR and IR spectra, are consistent with the order of ligand deficiency: 1 〉 2 〉 3 〉 4. The macrocyclic, eight-coordinate complex [K(18-crown-6)(THF)2]+ in 3 and 4 contains trans arranged THF ligands.
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  • 99
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 663-674 
    ISSN: 1434-1948
    Keywords: Aminoethyl-functionalized cyclopentadienyl complexes ; d-Block elements ; Hemilabile N-ligands ; Intramolecular coordination ; Tethered aminoethyl groups ; Water-soluble organometallics ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The introduction of an aminoethyl side chain into cyclopentadienyl compounds of many d-block elements leads to interesting changes in structure and reactivity compared to the parent species: (i) A hemilabile bonding situation is observed in complexes with low-valent transition-metal centers; (ii) amino-group coordination to an adjacent metal or nonmetal center creates novel types of bimetallic compounds; (iii) complexes with a tethered ammoniumethyl group often show good solubility in protic solvents, relevant with regard to organometallic chemistry in water. These features together with others are described in this review, which informs about the synthesis and properties of this new type of transition-metal complexes.
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  • 100
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1998 (1998), S. 675-692 
    ISSN: 1434-1948
    Keywords: Tripodal ligands ; Pyrazolyl donors ; Molybdenum ; Hydrogen bonds ; 2D-NMR ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chlorine functions of CH3C(CH2Cl)3, 1, may be replaced by pyrazolyl (pz) as well as imidazolyl (im) residues under the conditions of nucleophilic substitution leading to tripodal ligands CH3C(CH2X)3, X = pz, 2; X = im, 3. As a means of introducing two nitrogen donors and one phosphorus donor into a tripod ligand, substitution of the Br and OMs functions in O(CH2)2C(CH2Br)(CH2OMs), 8, by nitrogen nucleophiles and subsequent cleavage of the oxetane ring by a phosphide nucleophile to give HOCH2C(CH2PPh2)(CH2X)2 has been developed, furnishing 10a (X = pz) and 10d (X = NEt2), respectively. For the synthesis of 10a, K-pz was used as the nucleophile, while 10d was prepared using azide in the initial step, which then had to be transformed into NEt2 in two subsequent steps. The nucleophugic functions of the oxetane 8 undergo selective substitution by K-pz and KPPh2 in THF to produce O(CH2)2C(CH2PPh2)(CH2pz), 9b. Phosphide cleavage of the oxetane function leads to HOCH2C(CH2PPh2)(CH2PR2)(CH2pz), R = Ph, 10b; R = 3,5-Me2(C6H3), 10c. - The tris(pyrazolyl) tripod ligand 2 reacts with (MeCN)3Mo(CO)3to give 2 · Mo(CO)3(MeCN), 12a, in which only two of the three donor functions are coordinated. Upon reaction with 10a, the same reagent gives 10a · Mo(CO)4, 12b, with one pyrazolyl coordinated and the other involved in intramolecular hydrogen bonding to the CH2OH function (N···H-O distance 280 pm). Blocking of the OH function of 10a by etherification, i.e. to form EtOCH2C(CH2PPh2)(CH2pz)2, 11, does not dramatically affect the coordination capabilities with 11 · Mo(CO)3(MeCN), 12d, being formed upon treatment with (MeCN)3Mo(CO)3. Again only one pz function is coordinated to the metal. Bidentate coordination by two phosphorus donors of 10c is observed in 10c · Mo(CO)3(MeCN), 12d. The dangling arm pz donor function and the CH2OH group are intermolecularly hydrogen-bonded in this case. When the bulky P[3,5-Me2(C6H3)]2 substituent of 10c is replaced by the less sterically demanding PPh2 donor in 10b, η3-coordination is finally observed with the formation of 10b · Mo(CO)3, 13. The coordination capabilities of the new ligands are rationalized in terms of the size (six-, seven-, and eight-membered rings) and interference of the chelate cycles. All compounds have been characterized by the usual analytical and spectroscopic methods, with a complete assignment of the NMR data achieved by a combination of 2D-NMR techniques in some cases. The structures of the coordination compounds have additionally been deduced by X-ray methods.
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