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The use of a cis-dioxomolybdenum(VI) dinuclear complex with quadradentate 1,4-benzenediylbis(benzyldithiocarbamate)(2-) as model compound for the active site of oxo transfer molybdoenzymes: Reactivity, kinetics, and catalysis

Moradi Shoeili, Z ; Sharif University of Technology | 2012

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  1. Type of Document: Article
  2. DOI: 10.1016/j.saa.2011.12.033
  3. Publisher: 2012
  4. Abstract:
  5. Dinuclear cis-dioxomolybdenum(VI) complex [{MoO 2(Bz 2Benzenediyldtc)} 2] coordinated by a quadradentate dithiocarbamate (Bz 2Benzenediyldtc 2- = 1,4-benzenediylbis(benzyldithiocarbamate)(2-)) has been prepared and characterized by elemental analysis, 13C NMR, IR and UV-vis spectroscopy. The kinetics of the oxygen atom transfer between [{MoO 2(Bz 2Benzenediyldtc)} 2] and PPh 3 was studied spectrophotometrically in CH 2Cl 2 medium at 520 nm and four different temperatures, 288, 293, 298 and 303 K, respectively. The reaction follows second order kinetics with the rate constant k = 0.163(2) M -1 S -1 and its increasingly strong absorption at 520 nm clearly indicate the formation of a μ-oxo molybdenum(V) species as a product. Despite the steric restrictions imposed by the ligand structure to prevent the formation of Mo(V) species, experimental evidence confirms its interference during the process. The product can then be formulated as [MoO 2(Bz 2Benzenediyldtc) 2Mo 2O 3(Bz 2Benzenediyldtc) 2MoO 2] which has one μ-oxomolybdenum(V) moiety. An Eyring plot allows the activation parameters ΔH ‡ = 64.2(1) kJ mol -1 and ΔS ‡ = -45.1(6) J K -1 mol -1 to be determined from the temperature dependence of the rate constant, suggesting an associative transition state for the oxo transfer reaction. Catalytic oxygen atom transfer reaction from DMSO to PPh 3 was also followed by monitoring the chemical shift changes in 31P NMR spectroscopy. The substrate oxidation process follows a well-defined catalytic cycle capable of 100% conversion for the reaction of PPh 3 and DMSO without intervention of Mo(V) formation during about 36 h
  6. Keywords:
  7. Triphenylphosphine ; UV-vis spectroscopy ; Dithiocarbamates ; Molybdenum complex ; Oxo transfer ; Triphenyl phosphines ; Atomic spectroscopy ; Catalytic oxidation ; Chlorine ; Coordination reactions ; Enzyme kinetics ; Molybdenum oxide ; Nuclear magnetic resonance spectroscopy ; Rate constants ; Ultraviolet spectroscopy ; Ultraviolet visible spectroscopy ; Reaction kinetics ; Benzyldithiocarbamic acid ; Dimethyl sulfoxide ; Organophosphorus compound ; Oxidoreductase ; Thiocarbamic acid derivative ; Biocatalysis ; Biological model ; Chemical structure ; Chemistry ; Enzyme active site ; Metabolism ; Synthesis ; Time ; Ultraviolet spectrophotometry ; Biocatalysis ; Catalytic Domain ; Dimethyl Sulfoxide ; Kinetics ; Magnetic Resonance Spectroscopy ; Models, Biological ; Models, Molecular ; Molybdenum ; Organophosphorus Compounds ; Oxidoreductases ; Oxygen ; Spectrophotometry, Ultraviolet ; Thiocarbamates ; Time Factors
  8. Source: Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy ; Volume 88 , 2012 , Pages 210-215 ; 13861425 (ISSN)
  9. URL: http://www.sciencedirect.com/science/article/pii/S1386142511011073