Transition-metal complexes [(PMe₃)₂Cl ₂M(E)] and [(PMe₃)₂(CO)₂M(E)] with naked group 14 atoms (E = C-Sn) as ligands; part 2: complexation with W(CO) ₅

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 [(PMe₃)₂Cl₂M(E)] (IME) and the 18-VE Group 14 complexes [(PMe₃)₂(CO)₂M(E)] (2ME; M = Fe, Ru, Os; E = C, Si, Ge, Sn) in complexation with W(CO) 2. Calculations were also carried out for the complexes (CO)₅W-EO. The complexes [(PMe₃)₂Cl₂M(E)] and [(PMe₃) ₂(CO)₂M(E)] bind strongly to W(CO)₅ yielding the adducts IMEW(CO)₅ and 2ME-W(CO)₅, which have C _2v equilibrium geometries. The bond strengths of the heavier Group 14 ligands IME (E = Si-Sn) are uniformly larger, by about 6-7 kcal mol-1, than those of the respective EO ligand in (CO)₅W-EO, while the carbon complexes IMC-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 IME-W(CO)₅ is very similar to that in (CO)₅W-EO. The ligands 1IME are slightly weaker jt acceptors than EO while the Jt-acceptor strength of 2ME is even lower.