Observation of Carbon–Carbon Coupling Reaction in Neutral Transition-Metal Carbonyls

Abstract

Neutral titanium-metal carbonyl complexes with the chemical formula Ti(CO)n (n = 4–7) are produced in the gas phase by the reactions of titanium atoms with carbon monoxide in a pulsed laser vaporization–supersonic expansion source. Their infrared absorption spectra in the carbonyl stretching frequency region are measured by infrared plus vacuum ultraviolet (IR+VUV) two-color ionization spectroscopy based on a tunable VUV free electron laser. Infrared spectroscopy in conjunction with quantum chemical calculations confirm that all of these complexes have unexpected titanium ketenylidene OTiCCO(CO)n−2 structures. Bonding analysis indicates that the OTiCCO core structure can be described by the bonding interactions between a TiO+ cation in the doublet ground state and a doublet ground state of CCO–. The results reveal that the C–O bond breaking and C–C bond formation proceed efficiently in the reactions between laser-vaporized titanium atoms and carbon monoxide.