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

A tetra-nuclear, heterometallic copper(II)-cadmium(II) complex, [{CuL(H2O)}(2)(CuL)Cd](ClO4)(2)center dot H2O (1) has been synthesized by reacting the "ligand complex" [CuL] with Cd(ClO4)(2) where H2L is the tetradentate di-Schiff base derived from 1,3-propanediamine and 2-hydroxyacetophenone. Complex 1 transforms into a trinuclear species, [(CuL)(2)Cd(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. (C) 2010 Elsevier Ltd. All rights reserved.