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(H₂O)} ₂(CuL)Cd](ClO₄)₂•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) 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.