Heteroleptic binuclear copper(I) complexes bearing bis(salicylidene)hydrazone ligands: Synthesis, crystal structure and application in catalytic N-alkylation of amines

A new series of heteroleptic binuclear Cu(I) bis(salicylidene)hydrazone complexes (1-4) bearing triphenylphospine coligands have been synthesized from the reactions of copper(II) precursor complex [CuCl2(PPh3)(2)] with oxadiazole compounds A-D, respectively. It has been observed that the oxadiazole compounds u ndergo ring cleavage with in situ reduction of Cu(II) ion, during the formation of complexes (1-4). The oxadiazoles (A-D) and the Cu(I) complexes (1-4) have been characterized by analytical and spectroscopic methods. Single crystal X-ray diffraction study of complex 2 has revealed a distorted tetrahedral geometry around each Cu(I) center. Catalytic efficiency of the new complexes on the N-alkylation of amines using alcohols was studied under optimized conditions. The new complexes have also been tested for their catalytic activity towards the direct N-alkylation of 2-nitropyridine. (C) 2014 Elsevier Ltd. All rights reserved.