Kinetics of oxygen-atom transfer reactions involving molybdenum dithiolene complexes (original) (raw)

Oxo transfer reactions from [MoO 2 (mnt) 2 ] 2Ϫ [mnt 2Ϫ = 2,3-disulfanylmaleonitrile dianion (1,2-dicyanoethylenedithiolate)] to the abiological oxygen acceptors PPh 3Ϫx Et x (x = 0-3) have been studied spectrophotometrically in acetonitrile. The pseudo-first-order rate constants depend linearly on the concentration of the oxo acceptors. The sequence of reactivity is PEt 3 > PEt 2 Ph > PEtPh 2 > PPh 3 , reflecting the basicities of the phosphines, while the steric influence of the substituents on the phosphorus atom appears to be of minor importance. The activation entropies for the reaction with PEt 3 and PPh 3 are negative. These observations are in agreement with the proposal that in the intermediate the entering phosphine binds to the molybdenum complex through the oxygen ligand. Oxidation of HSO 3