CO Oxidation by Group 3 Metal Monoxide Cations Supported on [Fe(CO)4]2−.

Infrared photodissociation spectroscopy of mass-selected heteronuclear cluster anions in the form of OMFe(CO)5− (M=Sc, Y, La) indicates that all these anions involve an 18-electron [Fe(CO)4]2− building block that is bonded with the M center through two bridged carbonyl ligands. The OLaFe(CO)5− anion is determined to be a CO-tagged complex involving a [Fe(CO)4]2−[LaO]+ anion core. In contrast, the OYFe(CO)5− anion is characterized to have a [Fe(CO)4]2−[Y(η2-CO2)]+ structure involving a side-on bonded CO2 ligand. The CO-tagged complex and the [Fe(CO)4]2−[Sc(η2-CO2)]+ isomer co-exist for the OScFe(CO)5− anion. These observations indicate that both the ScO+ and YO+ cations supported on [Fe(CO)4]2− are able to oxidize CO to CO2. Theoretical analyses show that [Fe(CO)4]2− coordination significantly weakens the MO+ bond and decreases the energy gap of the interacting valence orbitals between MO+ and CO, leading to the CO oxidation reactions being both thermodynamically exothermic and kinetically facile. [ABSTRACT FROM AUTHOR]