文摘
A series of yttrium oxide–carbonyls are prepared via a laser vaporization supersonic cluster source in the gas phase and identified by mass-selected infrared photodissociation (IRPD) spectroscopy in the C–O stretching region and by comparing the observed IR spectra with those from quantum chemical calculations. For YO(CO)4+, all four CO ligands prefer to occupy the equatorial site of the YO+ unit, leading to a quadrangular pyramid with C4v symmetry. Two energetically nearly degenerate isomers are responsible for YO(CO)5+, in which the fifth CO ligand is either inserted into the equatorial plane of YO(CO)4+ or coordinated opposite the oxygen on the C4 axis. YO(CO)6+ has a pentagonal bipyramidal structure with C5v symmetry, which includes five equatorial CO ligands and one axial CO ligand. The present IRPD spectroscopic and theoretical study of YO(CO)n+ extends the first shell coordination number of CO ligands in metal monoxide carbonyls to six. The transition from equatorial to axial CO chemisorption in these yttrium oxide–carbonyls is fortunately observed at n = 5, providing new insight into ligand interactions and coordination for the transition metal oxides.