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 (mu-H) 24 (THF) (Cp' = C5Me4SiMe3, Ln = Y (1a), Lu (1b) ) with carbon monoxide (1 atm) yielded ethylene and the corresponding tetraoxo cubane complexes (Cp'Ln) 4 (mu3-O) 4 (Ln = Y (5a), Lu (5b) ). Stepwise formation of some key reaction intermediates, such as oxymethylene complexes (Cp'Ln) 4 (mu-OCH2) (mu-H) 6 (THF) (Ln = Y (2a), Lu (2b) ), enolate species (Cp'Y) 4 (OCH=CH2) (mu-O) (mu-H) 5 (THF) (3), and dioxo complex (Cp'Y) 4 (mu3-O) 2 (mu-H) 4 (THF) (4), was confirmed. The molecular structures of 2a, 4, and 5b were determined by X-ray diffraction studies.