Silyl, hydrido silylene or alternative bonding modes: The many possible structures of [(C₅H₅)(PH₃)IrX]⁺ (X = SiHR₂ and SiR₃; R = H, CH₃, SiH₃, and Cl)

DFT calculations with the B3LYP functional are carried out on the systems [Cp(PH3)Ir(SiHR2)]+ and [Cp(PH 3)Ir(SiR3)+ (Cp = C5H5, R = H, CH3, SiH3, Cl), which are representative examples of experimental complexes where the silylene ligand can exist. Geometry optimization for the different systems gives a large variety of structures, including the conventional silyl and hydrido silylene isomers, but also other less usual bridged structures, with a variety of groups taking a bridging position. Analysis of the large amount of data, together with those previously reported for [(dhpe)Pt(SiHR2)]+ and [(dhpe)Pt(SiR 3)]+ (dhpe = H2P-CH2-CH 2-PH2), leads to a better understanding of the general factors governing the relative stabilities of the possible isomeric forms. © 2006 American Chemical Society.