Surface Organometallic Chemistry: Formation of HFe₃(CO)₁₁⁻ from Fe₃(CO)₁₂ and Fe(CO)₅ on Silica, Alumina, Magnesia, and Zinc Oxide

This paper describes, at a molecular level, the organometallic chemistry that occurs during the adsorption of Fe₃(CO)₁₂ and Fe(CO)₅ on silica, alumina, magnesia, and zinc oxide. Fe(CO)₅ and Fe₃(CO)₁₂ are only weakly adsorbed on silica. In contrast on alumina, magnesia, and zinc oxide there is formation of the anionic hydride HFe₃(CO)₁₁⁻M⁺ (M = Al, Mg, Zn), which has been characterized in the adsorbed state by infrared, UV, and ¹H NMR spectroscopy and which has been extracted from the surface by ion exchange with Et₄NCl. The results indicate that the surface hydroxyl group of alumina, magnesia, or zinc oxide can make a nucleophilic attack at the coordinated CO as it occurs in solution with formation of the stable surface hydrido cluster. The result is also the first example of a grafted cluster where the grafting occurs by ionic interaction with a surface cation of the oxide lattice. It is possible that the anionic cluster interacts with such a surface cation via the oxygen lone pair of the bridging carbonyl ligand.