Synthesis, structural characterization, and thermal properties of monomeric (Mn, Co, Ni, and Zn) and polymeric (Cd) complexes of thiocyanates with benzyl carbazate as an ancillary ligand

Abstract

Five complexes [M(NCS)2(bc)2] M = Mn (1), Co (2), Ni (3), Zn (4), and [Cd(NCS)2(bc)]n (5), (bc) = benzyl carbazate (benzyl hydrazinecarboxylate), have been synthesized and characterized by physico-chemical and spectroscopic methods. The crystal structures of all five complexes have been confirmed by X-ray structural analysis. These results confirm that 1–4 are isotypes, and all four are centrosymmetric, with two mutually trans N,O chelating (bc) ligands in equatorial positions and a pair of trans-thiocyanate anions in the axial positions. The cadmium complex (5) is a coordination polymer. The asymmetric unit contains a square planar CdN2OS core, in which the (bc) ligand adopts an N, O bidentate coordination mode together with N and S bound thiocyanato anions. Polymer expansion increases the coordination number to six with the N and S bound thiocyanate ligands linking two adjacent complexes. This expansion results in double layers of cadmium octahedra propagating along the c axis direction. The thermal analyses of these compounds show endothermic decomposition processes to give respective metal thiocyanates as intermediates. For the Mn, Co, Ni, and Zn compounds these intermediates decompose exothermically to form metal oxides, whereas the Cd complex forms cadmium sulfide as the end product.