Cationic carboxylato complexes of dirhodium(II) with oxo thioethers: catalysts for silane alcoholysis under homogeneous and liquid-liquid biphasic conditions

A set of cationic dirhodium(II) complexes with oxo thioethers was prepared and employed as catalysts for the silane alcoholysis reaction. The complexes were found to be highly active under homogeneous conditions, both in the absence and in the presence of a solvent, including coordinating solvents such as N,N-dimethylformamide ; the catalysts could be conveniently employed in concentrations as low as 0.01 mol%, and a maximum TON of 30000 was recorded after 24 h. The same catalysts were also employed under liquid-liquid biphasic conditions with an ionic liquid as the catalyst-containing phase: comparable catalytic activity was observed under these conditions, and the catalyst-containing phase could be recovered and recycled. A chiral cationic dirhodium(II) complex was also prepared in the frame of this work; kinetic resolution of a racemic alcohol was attempted with this catalyst, unfortunately without success.