ELECTRONIC-STRUCTURES AND GAS-PHASE REACTIVITIES OF CATIONIC LATE-TRANSITION-METAL OXIDES

The structures, relative stabilities, and multiplicities of the cation ic, late-transition-metal oxides FeO+, CoO+, NiO+, and CuO+ are ration alized on the basis of ab initio computations. The bonding situation i n these cations is analogous to that in the dioxygen molecule with a b iradicaloid pi-bonding, and hence the electronic ground states of thes e metal oxide cations correspond to their high-spin variants, FeO+ ((6 ) Sigma(+)), CoO+ ((5) Delta), NiO+ ((4) Sigma(-)), CuO+ ((3) Sigma(-) ). Density functional theory augmented with CASPT2D computations is us ed to explore the reaction surface of FeO+ + H-2 and to unravel the ro ots of the extremely low reactivity observed for this system. Accordin g to these calculations, the reaction violates spin-conservation rules and involves a curve crossing from the sextet ground state to the exc ited quartet surface, giving rise to a multicentered, energetically lo w-lying transition structure, from which the hydride iron hydroxide ca tion H-Fe-OH+ is formed as the initial oxidation product. The implicat ions of these results with respect to other ion/molecule processes of metal oxide cations with oxidizable organic substrates are discussed.