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

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 angstrom. The complex is normal paramagnetic having 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 A(av)=63x10(-4)cm(-1), characteristic of mononuclear square-pyramidal copper(II) complexes. At LNT, the complex shows anisotropic spectra with g(parallel to) = 2.260 and g=2.070 and A(parallel to)=170x10(-4)cm(-1), respectively, characteristic of distorted square-pyramidal geometry. The complex is an efficient catalyst for oxidation of alcohols to aldehydes and ketones.