Ligand-mediated reactivity in CO oxidation of yttrium-nickel monoxide carbonyl complexes

A series of heteronuclear yttrium-nickel monoxide carbonyl complexes YNiO(CO)_n⁻ (n = 1–5) were generated in a pulsed-laser vaporization source and characterized by mass-selected photoelectron velocity-map spectroscopy combined with theoretical calculations. CO ligand-mediated reactivity in CO oxidation of yttrium-nickel monoxide carbonyl complexes was experimentally and theoretically identified. During the consecutive CO adsorption, a μ²-O linear structure was most favorable for YNiO(CO)_n⁻ (n = 1, 2), then a structure in which the terminal O was bonded to the Y atom became favored for YNiO(CO)₃⁻, and finally a structure bearing a CO₂ moiety was most favorable for YNiO(CO)_n⁻ (n = 4, 5). Theoretical calculations indicated that the Ni atom acted as an electron acceptor and accumulated electron density at n ≤ 3, and then served as an electron donor along with the Y atom to contribute electron density in the rearrangement that accompanied CO oxidation at n > 3.