Synthesis and crystal structure of a heterometallic tetra-nuclear copper(II)–cadmium(II) complex and its anion modulated conversion into a trinuclear species

Abstract

A tetra-nuclear, heterometallic copper(II)–cadmium(II) complex, [{CuL(H 2O)} 2(CuL)Cd](ClO 4) 2·H 2O ( 1) has been synthesized by reacting the “ligand complex” [CuL] with Cd(ClO 4) 2 where H 2L is the tetradentate di-Schiff base derived from 1,3-propanediamine and 2-hydroxyacetophenone. Complex 1 transforms into a trinuclear species, [(CuL) 2Cd(NCS) 2] ( 2) on treatment with an ammonium thiocyanate solution. Both complexes have been characterized by X-ray single crystal structure analyses. In both structures, the central Cd(II) ion has a six-coordinate distorted octahedral environment being bonded to six oxygen atoms from three Cu(II) units in 1 and to four oxygen atoms from two [CuL] units along with a couple of thiocyanate nitrogen atoms in complex 2. Complex ( 1) exhibits reversible reductive (Cu(II)/Cu(I); Epc, −1.03 V) and oxidative (Cu(II)/Cu(III); Epa, +1.04 V, respectively) responses in cyclic voltammetry. The generated Cu(I) species for both the complexes are unstable and undergo disproportionation.