Theoretical investigation of substituent effects on the silicon-metal bond for a series of transition metal-substituted base-stabilized silylene complexes

Hartree-Fock ab initio calculations were used to investigate the effects of various silicon substituents on the silicon-ruthenium bond for four transition metal-substituted base-stabilized silylene complexes. To provide comparison information, one silyl complex, Cp*(PMe3)(2)Ru-Si[S(Tol-p)](3), and four base-free silylene complexes ([Cp*(PMe3)(2)Ru=SiMe2]BPh4, Cp*(PMe3)(2)Ru=Si[S(Tol-p)][Os(CO)(4)], a bis(silylene)nickel compound and [trans-(P(Cy-3)(2)(H)Pt=Si(SEt)(2)]BPh4) were also studied. Results of the calculations indicate that the order of promotion of silylene character for base groups is NCMe > OTf much greater than S(Tol-p). Of those considered, the best substituent group in terms of transition metal-silicon double bond promotion is methyl followed by triflate. The worst group with respect to this property is S(Tol-p). (C) 2001 Elsevier Science B.V. All rights reserved.