LAUSR

The chemical bonding and electronic structure of heteronuclear metal–nickel carbonyls MNi(CO)n− (M = Sc, Y; n = 2–6) have been investigated by mass-selected photoelectron velocity map imaging spectroscopy and quantum chemical calculations. Two CO bonding modes (side-on-bonded and terminal carbonyls) are involved in the n = 2 cluster. The building block composed of three kinds of different CO modes (side-on-bonded, bridging, and terminal carbonyls) is favored at n = 3, the structure of which persists up to n = 6. The additional CO ligands are preferentially coordinated in the terminal mode to the Sc atom and then to the Ni atom in the larger clusters. The present findings would promote the understanding of CO molecule activation and chemisorbed CO molecules on metal surfaces.