Reduction of imines catalysed by NHC substituted group 6 metal carbonyls

Abstract The catalytic activity of a series of metal carbonyls [M(CO) 6 ], and the corresponding NHC substituted [M(CO) 5 (NHC)], (M = Cr, Mo, W) complexes was examined in the reduction of N -benzylideneaniline and acetophenone using silyl hydrides and isopropanol/KOH as reductants. The use of various additives and ultraviolet irradiation to promote the reduction of imines using silyl hydrides as reductants was explored. From a comparison of the reactivity of [Mo(CO) 6 ], [Mo(CO) 5 (NHC)], and [Mo(CO) 4 ( bis NHC)] it was inferred that electron density on the metal centre plays a key role in the catalysis. Four of the best catalysts were then tested in the reduction of a variety of imines with different electronic and steric properties.