Hydrogenation of Carbon Monoxide by Tetranuclear Rare Earth Metal Polyhydrido Complexes. Selective Formation of Ethylene and Isolation of Well-Defined Polyoxo Rare Earth Metal Clusters

The reaction of the tetranuclear rare earth metal polyhydrido complexes {Cp‘Ln(μ-H)2}4(THF) (Cp‘ = C5Me4SiMe3, Ln = Y (1a), Lu (1b)) with carbon monoxide (1 atm) yielded ethylene and the corresponding tetraoxo cubane complexes (Cp‘Ln)4(μ3-O)4 (Ln = Y (5a), Lu (5b)). Stepwise formation of some key reaction intermediates, such as oxymethylene complexes (Cp‘Ln)4(μ-OCH2)(μ-H)6(THF) (Ln = Y (2a), Lu (2b)), enolate species (Cp‘Y)4(OCHCH2)(μ-O)(μ-H)5(THF) (3), and dioxo complex (Cp‘Y)4(μ3-O)2(μ-H)4(THF) (4), was confirmed. The molecular structures of 2a, 4, and 5b were determined by X-ray diffraction studies.