Mechanisms of hydrogenation. Part VIII. Bis(pyridine)dimethylformamidedichlororhodium borohydride as a catalyst for homogeneous hydrogenation

Abstract

A complex, (py)₂(dmf)(RhCl₂)BH₄(py = pyridine, dmf = dimethylformamide) which is a highly active catalyst for homogeneous hydrogenation is obtained from (py)₃RhCl₃ and sodium borohydride in dimethylformamide. The borohydride residue and molecular hydrogen are shown to be alternative hydride sources in hydrogenation. The pyridine ligands in the complex or excess of pyridine undergoes slow hydrogenation, and derived complexes containing pipericine have been isolated. The hydrogenation of cycloalkenes is discussed, and the complex is also shown to catalyse the hydrogenation of –NN–, –NC, and NO₂ groups.