Adducts of hydrogen and methane with Os(II) and Os(IV) complexes: Theoretical analysis of (η 2-H 2)OsCl 2(PH 3) 2 and (η-CH 4)OsCl 2(PH 3) 2 molecular complexes by RHF, MP2 and DFT methods

Abstract

A theoretical study of model OsCl 2(PH 3) 2 complex and its adducts with hydrogen and methane is reported. Geometry of two isomers of OsCl 2(PH 3) 2 complex and structures of possible σ complexes (η 2-H 2)OsCl 2(PH 3) 2, (η 2-CH 4)OsCl 2(PH 3) 2 have been calculated using density functional theory and MP2-method. It was shown that some isomers of weakly bonded hydrogen σ-complex OsH 2Cl 2(PH 3) 2 can form stable methane adducts followed by reductive elimination of hydrogen. Calculations of the reaction pathways for methane oxidative addition to isomers of 14-electron intermediate OsCl 2(PH 3) 2 have been performed. For the isomer active in this reaction, structures of the transition state and methylhydride product were calculated. Frequencies of vibrations of stable σ-complex (η 2-CH 4)OsCl 2(PH 3) 2 along with its deuterated form (η 2-CD 4)OsCl 2(PH 3) 2 have been computed in the MP2/LAN1DZ approximation.