Aerobic oxidation of primary benzylic amines to amides and nitriles catalyzed by ruthenium carbonyl clusters carrying N,O-bidentate ligands.

Abstract

Four trinuclear ruthenium carbonyl clusters, (6-BrPyCHRO)2Ru3(CO)8 (R = 4-OCH3C6H4, 1a; R = 4-BrC6H4, 1b) and (2-OC6H4-HC[double bond, length as m-dash]N-C6H4R)2Ru3(CO)8 (R = 4-OCH3, 2a; R = 4-Br, 2b), were synthesized from the reactions of Ru3(CO)12 with the corresponding N,O-bidentate ligands (two pyridyl alcohols and two Schiff bases) respectively in a ratio of 1 : 2. Three new complexes 1b, 2a and 2b have been fully characterized by elemental analysis, FT-IR, NMR and X-ray crystallography. The catalytic activity of these ruthenium complexes for the aerobic oxidation of primary benzylic amines to amides and nitriles in the presence of t-BuOK was investigated, of which the Schiff base complex 2a was found to exhibit the highest activity.