The catalytic hydrogenation of some N-substituted salicylideneimines and their metal complexes

Abstract

The C=N bonds in N-arylsalicylideneimines are readily reduced by hydrogen in the presence of Adams's platinum catalyst, forming N-aryl-o-hydroxybenzylamines. Copper(II), cobalt(II), and cobalt(III) complexes of the imines are reduced to the metal and appropriate benzylamine but larger amounts of catalyst are required for complete reduction of the complexes than are necessary to reduce the free bases. The C=N bonds of uncoordinated quadridentate ligands such as NN?-ethylenebis-(salicylideneimine) may be similarly reduced but neither the C-=N bonds nor the metal ions can be reduced in the Cu, Ni, or Co complexes derived from these and related ligands even in the presence of very large amounts of catalyst. The bidentate o-hydroxybenzylamines do not react with nickel, cobalt, zinc, or manganese ions but the formation of copper complexes has been demonstrated by continuous variation studies and the isolation of complexes of the form Cu(II)L. CH₃COO. The quadridentate amines, however, react readily with bivalent metals.