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  • 1
    Electronic Resource
    Electronic Resource
    Conformational Analysis of Sulfur-Containing Heterocycles, Part I. Synthesis and Structural Determination of Diastereomerically Pure 4,6-Bis-(phenoxymethyl)-1,2,5-trithiepanes (1998)
    Springer
    Structural chemistry 9 (1998), S. 139-148 
    Details
    ISSN: 1572-9001
    Keywords: 4,6-Bis-(phenoxymethyl)-1,2,5-trithiepanes ; variable-temperature NMR ; conformational analysis ; ring interconversion ; HF/6-31G* ; transition state
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some diastereomerically pure 4,6-bis-(phenoxymethyl)-l,2,5-trithiepanes were synthesized and unambiguously assigned. Their conformational properties and dynamic behavior were investigated by various NMR spectroscopic methods and quantum-chemical calculations at the HF/6-31G* level. The ground states of these compounds proved to be twist-chairs. A ring interconversion can occur in the meso-isomers as well as in the (±)-isomers. This interconversion can be described as a simultaneous inversion of the disulfide bridge. In the case of the meso-isomers, both ground states are mirror images of each other and the transition state is a highly symmetrical chair. The barrier heights of interconversion were determined to be in the range of 50 kJ/mol by variable-temperature NMR measurements. The ground states as well as the transition state of the (±)-isomers were found to be nonsymmetrical. However, those dynamic processes that are fast with respect to the NMR time scale lead to averaged NMR spectra at room temperature. A further dynamic process found through the quantum-chemical calculations is a “flapping” of the meth-ylene groups of the rings. The energy barrier of this flapping was calculated to be very small (〈 20 kJ/mol) and could not be observed by low-temperature NMR measurements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022416021618
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  • 2
    Electronic Resource
    Electronic Resource
    Structure and Reactivity of Sodium Phenoxide - Following the Course of the Kolbe-Schmitt Reaction (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1461-1465 
    Details
    ISSN: 0009-2940
    Keywords: Kolbe-Schmitt reaction ; Solid-state structures ; Sodium phenoxide ; Solvent Complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solvent-free sodium phenoxide (NaOPh) crystallises as a polymer and forms a polymeric chain in the [0 0 1] direction. The low coordination of the sodium atoms, as evident in the crystal structure, is confirmed by the easy coordination of oxoligands (α-donors). Hence, the four-membered ring chain of the solvent-free sodium phenoxide is separated by oxoligands, and forms partial structures as the polymer fragments. Thus, NaOPh crystallises in THF with the formation of an Na6O6 core, consisting of two face-fused heterocubes, and in N, N, N′, N′-tetramethyl urea (TMU) with the formation of a Na4O4 heterocubane. The solvent-free NaOPh-CO2 complex obtained from the addition of CO2 to a solution of sodium phenoxide is, when exposed to a temperature of 80°C, subject to an irreversible phase transition, as demonstrated by FT-IR and DTA studies. The complex formed at 80°C is, apparently, another intermediate of the Kolbe-Schmitt reaction.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971301017
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  • 3
    Electronic Resource
    Electronic Resource
    Pn-Liganden mit maximaler Elektronendonorfähigkeit, 7. Dreikomponentenreaktion von P4-Phosphor mit [CpxRh(CO)2] in Gegenwart von [Cr(CO)5THF] oder [CpMn(CO)2THF]. - Eine Methode zum Studium des Transformationsweges vom P4-Tetraeder zum planaren cyclo-P4-LigandenHerrn Professor Gerhard Fritz zum 75. Geburtstag gewidmet. (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 251-257 
    Details
    ISSN: 0009-2940
    Keywords: Tetraphosphorus ligands ; Bond cleavage in P4, stepwise ; Rhodium P4 complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Pn Ligands with Maximum Electron-Donor Capacity, 7. - Three-Component Reaction of P4-Phosphorus with [CpxRh(CO)2] in the Presence of [Cr(CO)5THF] or [CpMn(CO)2THF]. - A Method of Studying the Pathway from Tetrahedral P4 to the Planar cyclo-P4 LigandHerrn Professor Gerhard Fritz zum 75. Geburtstag gewidmet.The reaction of P4 with [CpxRh(CO)2] (Cpx = Cp′, Cp′′; Cp′ = η5-C5H4tBu, Cp′′ = η5-C5H3tBu2-1,3) in the presence of [Cr(CO)5THF] leads to [CpxRh(CO)(η1:1-P4){Cr(CO)5}4] (1a, b), [Cp′′Rh(η4-P4){Cr(CO)5}3] (2b), and [Cp′Rh(η4-P4){Cr-(CO)5}4] (3a). In the corresponding reaction with [CpMn-(CO)2THF] no P4 takes part, and [(Cp′′RhCO)(CpMnCO)(μ-CO)2] (4) is formed. An X-ray structure determination of [CpxRh(CO)(η1:1-P4){Cr(CO)5}4] (1) and [Cp′Rh(η4-P4)-{Cr(CO)5}4] (3a) indicates a stepwise (PP) bond cleavage as the transformation pathway from the P4 tetrahedron to the cyclo-P4 ligand by passing a bicyclotetraphosphane. In the cyclo-P4 ligand complex 3a all P atoms are able to coordinate to [Cr(CO)5] groups. However, in [Cp′′Rh(η4-P4){Cr(CO)5}3] (2b) the additional tBu group at the Cpx ligand sterically influences the coordination behavior of the P atoms, and only three of them are able to coordinate to [Cr(CO)5] units. In these syntheses the [Cr(CO)5] moieties promote the reaction and stabilise intermediates along the reaction pathway. Variable-temperature 31P{1H}-NMR measurements indicate for 2b the freezing of the Cp′′ rotation at low temperature and reveals a ΔG≠c (at the coalescence temperature) of 36 kJ mol-1. Surprisingly, in [(Cp′′RhCO)(CpMnCO)(μ-CO)2]-(Rh-Mn) (4) the Cpx ligands are cis-oriented whereas in [(Cp*RhCO)(CpMnCO)(μ-CO)2](Rh-Mn) a trans arrangement is observed. This indicates the unusual behavior of the Cp′′ ligand as a “rod” and not as an “enlarged disk” like Cp* in the crystal lattice of these compounds.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280308
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  • 4
    Electronic Resource
    Electronic Resource
    Metallorganische CO2-Speichersysteme aus Nickel(0)-1-azadieneinheiten und ihre Reaktivität bei der Carboxylierung von Acetophenon (1995)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 128 (1995), S. 281-287 
    Details
    ISSN: 0009-2940
    Keywords: Carbon dioxide fixation ; 1-Azadiene ligands ; Nickel(0) complexes ; Carboxylation ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Organometallic CO2 Reservoires from Nickel(0)-1-Azadiene-Type Ligands and Their Reactivity in the Carboxylation of Acetophenone1-Azadiene-type ligands yield with nickel(0) binuclear organometallic compounds of the type [Ni(1-azadiene)n,]2 (n = 1, 2). The structures of the complexes 1 (n = 2, ligand A) and 3 (n = 1, ligand C) have been characterized by X-ray crystallography. 1 is unreactive towards CO2, 3 and similar compounds are able to react with CO2 to give metallacyclic carbamato complexes of Ni(II). In these compounds CO2 is activated and can carboxylate acetophenone to yield benzoylic acid upon protolysis. These reactions mimic biologic conversion reactions of CO2 into organic material by organometallics. - The addition of two moles of the (bpy)Ni(0)-fragment [from (bpy)Ni(COD)] to 3 gives the tetranuclear complex 6. The X-ray analysis of the monomeric model compound (bi-py)Ni(A) (11) shows that only the olefin part is coordinated. 6 and 11 can also react with CO2. Cu(I) complexes with 1-azadiene-type ligands are not reactive towards CO2.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19951280312
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  • 5
    Electronic Resource
    Electronic Resource
    Complex Catalysis, XLIXPart XLVIII: R. Taube, H. Windisch, S. Maiwald, H. Helming, H. Schumann, J. Organomet. Chem. 1996,513, 49-61 On the Coordination of Olefins and Secondary Amines at the Cationic [2,6-Bis(diphenylphosphanylmethyl)pyridine]rhodium(I) Fragment [Rh(PNP)]+ - Synthesis and Characterization of [Rh(PNP)(L)]X (L = Ethylene, Styrene, HNR2; X = BF4, PF6, CF3SO3)Dedicated to Prof. Dr. Wolfgang Beck on the occasion of his 65th birthday. (1997)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 939-945 
    Details
    ISSN: 0009-2940
    Keywords: Rhodium ; Cations ; Tridentate ligand ; Alkene complexes ; P Ligands ; N ligands ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The cationic rhodium(1) complexes [Rh(PNP)(C2H4)]X; X = BF4 (1a), PF6 (1b), CF3SO3 (1c ) were prepared by addition of the tridentate ligand 2,6-bis(diphenylphosphanylmethyl)pyridine (PNP) to a solution of [Rh(C2H4)2(solv)2]X (solv = acetone or THF) under ethylene. The complexes were characterized by IR and 1H-, 13C-, and 31P-NMR spectroscopy. The coordination of two ethylene molecules at the [Rh(PNP)]+ fragment could be detected by dynamic proton resonance of a solution of 1a under free ethylene. The styrene complex [Rh(PNP)(styrene)]BF4 (4) was obtained by substitution of the ethylene from 1a with an excess of styrene. The π coordination of C2H4 and styrene in 1a and 4 respectively was confirmed by X-ray crystal structure analysis. The olefin complexes react with an excess of the secondary amine to give the corresponding amine complexes [Rh(PNP)(HNR2)]X; HNR2 = piperidine (5), HNMe2 (6 ), HNEt2 (7). Conversly, the amine could be released from the amine complexes with an excess of ethylene at low temperature by the formation of the ethylene complex 1.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19971300720
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  • 6
    Electronic Resource
    Electronic Resource
    On the Mechanism of n-Butyl Vinyl Sulfide Formation with [K(18-crown-6)SBu] as catalyst (1996)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 338 (1996), S. 264-269 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: n-Butyl mercaptane reacts with acetylene in the presence of [K(18-cr-6)SBu] as catalyst to give n-butyl vinyl sulfide. In toluene the reaction is of zeroth order with respect to BuSH and first order with respect to [K(18-cr-6)SBu]. The reaction rate depends on the solvent in the following order: toluene 〉 triglyme ≈ BuSH ≈ dioxane ≫ BuOH. In toluene, BuOH added in equimolar amounts accelerates the reaction indicating a complex formation [K(18-cr-6) (BuOH)SBu] with a higher catalytic activity. [K(18-cr-6)SBu] is monomeric in the solid state with d(K-S) = 3.051(2) Å. Potassium is displaced out of the mean plane defined by the six oxygen atoms of the crown ether by 0.626(3) Å. [K(18-cr-6)SBu] is a strong electrolyte in alcohols but practically no electrolytic dissociation takes place in solvents with low dielectric constants such as toluene and n-butyl mercaptane. From the results a reaction mechanism is derived with the addition of non-dissociated [K(18-cr-6)SBu] to acetylene as the rate-determining step.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19963380152
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  • 7
    Electronic Resource
    Electronic Resource
    Synthesis, Crystal Structure, Spectroscopy, and Theoretical Investigations of Tetrahedrally Distorted Copper(II) Chelates with [CuN2S2] Coordination Sphere (1999)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 1999 (1999), S. 1393-1403 
    Details
    ISSN: 1434-1948
    Keywords: Copper chelates ; EPR spectroscopy ; Electronic structure ; Schiff base ligands ; Structure elucidation ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of tetrahedrally distorted copper(II) complexes with thiolate and imine coordination were synthesized. Schiff bases derived from 4-benzoyl-3-methyl-1-phenyl-2-pyrazoline-5-thione and various diamines were used as tetradentate ligands to obtain tetrahedrally distorted metal chelates with [CuN2S2] complex units. Crystal structures of the complexes 1, 2, 5 and 6 and of ligand H25 have been determined by means of single-crystal X-ray structure analysis. The structure data show a strong influence of the diamine building blocks on the tetrahedral distortion of the copper(II) complexes. Results of Extended Hückel LCAO calculations correlate strongly with structural, electrochemical, UV/Vis- and EPR-spectroscopic features obtained experimentally. The calculations confirm for the whole complex series a strong delocalization of the frontier orbitals. The highest fully occupied molecular orbital shows a weak contribution, resulting from thiolate donor atoms, whereas the antibonding singly occupied molecular orbitals (SOMOs) are distributed between the copper(II) centre (ca. 35-40%) and the N2S2 donor set. The SOMO energy significantly lowers with increasing tetrahedral distortion of the coordination sphere. The influence of the tetrahedral distortion of copper(II) complexes on redox potentials, UV/Vis and EPR spectra is discussed.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Structure of monomeric 1-aryl-2-nitroso-prop-1-enes (1995)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 337 (1995), S. 686-687 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.199533701144
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  • 9
    Electronic Resource
    Electronic Resource
    dad-Verbindungen des Niobs und Tantals: Musterbeispiele für die strukturelle Flexibilität von dad-LigandenDiese Arbeit wurde vom Fonds der Chemischen Industrie und von der Deutschen Forschungsgemeinschaft gefördert. dad = 1,4-Diaza-1,3-butadien, tBu-dad = N,N′-Bis(tert-butyl)-1,4-diaza-1,3-butadien. (1995)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 107 (1995), S. 2865-2867 
    Details
    ISSN: 0044-8249
    Keywords: 1,4-Diaza-1,3-dien-Komplexe ; Heterodienverbindungen ; Niobverbindungen ; Tantalverbindungen ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19951072310
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  • 10
    Electronic Resource
    Electronic Resource
    Synthese und Insertionsreaktionen von Cp2′HfCl{As(SiMe3)2} (Cp′ = C5H4Me)Professor Kurt Dehnicke zum 65. Geburtstag gewidmet (1996)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 622 (1996), S. 683-688 
    Details
    ISSN: 0044-2313
    Keywords: Hafnocene monoarsenido complex ; Insertion reactions ; Crystal structures ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Insertion Reactions of Cp2′HfCl{As(SiMe3)2} (Cp′ = C5H4Me)The reaction of Cp2′HfCl2 (Cp′ = C5H4Me) with Li(THF)2,5As(SiMe3)2 (1 : 1) at room temperature gives the terminal hafnocene arsenido complex Cp2′HfCl{As(SiMe3)2} (1) in high yield. 1 inserts CS2 and PhNC into the Hf—As bond yielding Cp2′HfCl{η2-S2CAs(SiMe3)2} (2) and Cp2′HfCl{η2-N(Ph)CAs(SiMe3)2} (3). The thermally sensitive complexes 1-3 were characterised spectroscopically and crystal structure determinations were carried out on 1 and 3 which shows the η2 bonding mode of the N(Ph)CAs(SiMe3)2 ligand in the latter.
    Notes: Die Reaktion von Cp2′HfCl2 (Cp′ = C5H4Me) mit Li(THF)2,5As(SiMe3)2 (1 : 1) bei Raumtemperatur liefert den terminalen Hafnocen-Monoarsenido-Komplex Cp2′HfCl{As(SiMe3)2} (1) in guter Ausbeute. 1 reagiert mit CS2 oder PhNC unter Insertion in die Hf—As-Bindung und Bildung von Cp2′HfCl{η2-S2CAs(SiMe3)2} (2) und Cp2′HfCl{η2-N(Ph)CAs(SiMe3)2} (3). Die thermisch labilen Verbindungen 1-3 wurden spektroskopisch charakterisiert; an 1 und 3 wurden Röntgenstrukturanalysen durchgeführt. Demnach liegt in 3 ein η2-koordinierter N(Ph)CAs(SiMe3)2-Ligand vor.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19966220419
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