Structural and electronic features of triphenylstibine-functionalized Fischer carbene complexes of molybdenum(0)

Abstract

The synthesis and characterization of the first triphenylstibine-containing Fischer carbene complexes of Mo(0) with general formula [(SbPh3)(CO)4MoC(OEt)(Ar)] with Ar = 2-thienyl (1), 2-furyl (2), 2-(N-methyl)pyrrolyl (3), and 2,2′-bithienyl (4) are reported. The solid state crystal structures of these complexes show a syn conformation of the 2-thienyl and 2,2′-bithienyl groups relative to the ethoxy group, and an anti conformation of the 2-furyl group relative to the ethoxy group. Density functional theory calculations using natural bonding orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations gave insight into the electronic structure and preferred conformations of these novel complexes. X-ray photoelectron spectroscopy measurements show that the binding energy of the Mo 3d5/2 photoelectron line for the 2-(N-methyl)pyrrolyl-containing Fischer carbene complex, 3, is the smallest; followed by 2 and then 1. This implies that the Mo metal centre is more electron rich in 3, relative to the 2-furyl or 2-thienyl containing Fischer carbene complexes, 2 and 1, respectively.