Transition-metal complexes [(PMe(3))(2)Cl(2)M(E)] and [(PMe(3))(2)(CO)(2)M(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 [(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(2v) 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 pi acceptors than EO while the pi-acceptor strength of 2ME is even lower.
Parameswaran
Pattiyil
P
Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032 Marburg, Germany.
Frenking
Gernot
G