METHANE ACTIVATION BY OS(II) COMPLEXES - THEORETICAL-STUDY OF METHANEOXIDATIVE ADDITION TO ISOMERIC OSCL2(PH3)(2) COMPLEXES BY RHF, MP2, AND DFT METHODS

The oxidative addition of methane to a model Os(Cl)(2)(PH3)(2) complex was theoretically studied using restricted Hartree-Fock (RHF) calcula tions refined by taking into account electron energy correlation by th e MP2 and DFT methods. The calculation predicts the existence of a num ber of stable isomers of Os(Cl)(2)(PH3)(2). Quantum chemical analysis of methane reactions with three isomers suggests the formation of sigm a-complexes (eta(2)-CH4)Os(Cl)(2)(PH3)(2) for some isomers. The pathwa ys of the oxidative addition reaction to three isomers were calculated . The initial tetrahedral isomer forms the most stable sigma-complex w ith methane, although it is incapable of activating a C-H bond. Only s quare-pyramidal isomer activates methane by oxidative addition with lo w activation energy and yields a methylosmium hydride product.