Significant π bonding in coinage metal complexes OCTMCCO− from infrared photodissociation spectroscopy and theoretical calculations

Abstract

A series of coinage metal complexes in the form of TMC(CO)n- (TM=Cu, Ag, Au; n = 0-3) were generated using a laser ablation-supersonic expansion ion source in the gas phase. Mass-selected infrared photodissociation spectroscopy in conjunction with quantum chemical calculations indicated that the TMC(CO)3- complexes contain a linear OCTMCCO- core anion. Bonding analyses suggest that the linear OCTMCCO- anions are better described as the bonding interactions between a singlet ground state TM+ metal cation and the OC/CCO2- ligands in the singlet ground state. Besides the strong ligands to metal σ donation bonding components, the π-bonding components also contribute significantly to the metal-ligands bonding due to the synergetic effects of the CO and CCO2- ligands. The strengths of the bonding of the three metals show a V-shaped trend in which the second-row transition metal Ag exhibits the weakest interactions whereas the third-row transition metal Au has the strongest interactions due to the relativistic effects.