Theoretical studies of the bonding in cationic ruthenium silylenes

Hybrid Hartree-Fock/DFT calculations were performed on several model complexes of the general formula CpL2Ru=SiX2+ (L = PH3, PMe3, CO, X = H, Me, SH) as well as Cp(PH3)(2)Ru=CH2+ and analyzed through the use of NBO, CDA, and properties of atoms in molecules. Silicon to ruthenium multiple bonds of low order were found in all of the examined complexes with the exception of Cp(PH3)(2)RuSi(SH)(2)(+). Multiple bonding in these complexes is strengthened through the use of trialkylphosphine ligands on the ruthenium and weakened through the use of pi-acids on the ruthenium or substituents other than hydrogen on the silicon. Suggested formulations for improving the pi-system are presented.