Synthesis and characterization of a copper–zinc heterobinuclear complex of 2,2′-bipyridine

Abstract

The synthesis of the heterobinuclear copper–zinc complex [CuZn(bz)3(bpy)2]BF4 from benzoic acid and bipyridine is described. Single crystal X-ray diffraction of the heterobinuclear complex reveals the geometry of the benzoate-bridged Cu(II)–Zn(II) center. The copper and zinc ions are five coordinates, having distorted square pyramidal geometry. The Cu–Zn distance is 3.384 Å. The complex is normal paramagnetic having μeff value equal to 1.75 BM, ruling out the possibility of Cu–Cu interaction in the structural unit of the complex. The ESR spectrum of the complex in CH3CN at RT exhibits an isotropic four-line spectrum centered at g = 2.082 and hyperfines coupling constants Aav = 63 × 10−4 cm−1, characteristic of mononuclear square-pyramidal copper(II) complexes. At LNT, the complex shows anisotropic spectra with g║ = 2.260 and g = 2.070 and A║ = 170 × 10−4 cm−1, respectively, characteristic of distorted square-pyramidal geometry. The complex is an efficient catalyst for oxidation of alcohols to aldehydes and ketones.