Abstract
Density functional calculations at the BP86/TZ2P level were carried out to understand the ligand properties of the 16‐valence‐electron(VE) Group 14 complexes [(PMe~3~)~2~Cl~2~M(E)] (1ME) and the 18‐VE Group 14 complexes [(PMe~3~)~2~(CO)~2~M(E)] (2ME; M=Fe, Ru, Os; E=C, Si, Ge, Sn) in complexation with W(CO)~5~. Calculations were also carried out for the complexes (CO)~5~W–EO. The complexes [(PMe~3~)~2~Cl~2~M(E)] and [(PMe~3~)~2~(CO)~2~M(E)] bind strongly to W(CO)~5~ yielding the adducts 1ME–W(CO)~5~ and 2ME–W(CO)~5~, which have C~2__v__~ equilibrium geometries. The bond strengths of the heavier Group 14 ligands 1ME (E=Si–Sn) are uniformly larger, by about 6–7 kcal mol^−1^, than those of the respective EO ligand in (CO)~5~W‐EO, while the carbon complexes 1MC–W(CO)~5~ have comparable bond dissociation energies (BDE) to CO. The heavier 18‐VE ligands 2ME (E=Si–Sn) are about 23–25 kcal mol^−1^ more strongly bonded than the associated EO ligand, while the BDE of 2MC is about 17–21 kcal mol^−1^ larger than that of CO. Analysis of the bonding with an energy‐decomposition scheme reveals that 1ME is isolobal with EO and that the nature of the bonding in 1ME–W(CO)~5~ is very similar to that in (CO)~5~W–EO. The ligands 1ME are slightly weaker π acceptors than EO while the π‐acceptor strength of 2ME is even lower.