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  • 1
    Electronic Resource
    Electronic Resource
    CO2-Aktivierung an Übergangsmetallzentren: Simulation enzymatischer CO2-Fixierungs- und Transferreaktionen durch elektronenreiche (Diazadien)magnesium- und -mangan-Komplexe (1992)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 125 (1992), S. 1529-1536 
    Details
    ISSN: 0009-2940
    Keywords: Carbon dioxide fixation ; Metal complexes ; Diazadiene ligands ; Carboxylation ; Enzyme models ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Activation of CO2 at Transition-Metal Centres: Simulation of Enzymatic CO2 Fixation and Transfer Reactions by Electron-Rich (Diazadiene)magnesium and -manganese ComplexesElectron-rich diazadiene complexes of Mg and Mn can be used as model compounds for enzymatic carboxylation reactions e.g. the „dark reaction“ of the photosynthesis or in biotinedependent CO2 conversion reactions. The activity of the complexes to fix and transfer carbon dioxide strongly depends on the nature of the metal (Mg and Mn are active central atoms, other transition metals are inactive), the π aciditiy of the chelate ligand, and the structure of the complexes. The dimeric manganese complex IIa, the structure of which could be determined by X-ray structure analysis, is one of the most active compounds. NMR studies reveal that the CO2 transfer to substrates with active C - H bonds takes place in the coordination sphere of the metal atom. Carrier of activated CO2 is the N - COO group.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19921250703
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  • 2
    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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  • 3
    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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    Paper (German National Licenses)
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