Efficient oxidation of benzene catalyzed by Cu(II) tetrazolato complexes under mild conditions

Two new coordination complexes containing 5-(4-chlorophenyl)tetrazolato (4-Clptz) and polypyridyl ligands, [Cu2(bipy)2(4-Clptz)4] [1, bipy = 2,2′-bipyridine] and [Cu2(phen)2(4-Clptz)4] [2, phen = 1, 10 phenanthroline] have been synthesized following metal ligated [2 + 3] cycloaddition reaction between copper bound azide polymer containing polypyridyl and 4-chloro benzonitrile. Both the complexes have been fully characterized by different spectroscopic techniques. Single crystal X-ray diffraction study reveals that the complexes are dimeric in nature with penta-coordinated geometry around the Cu(II) centre through N-donor sites. These complexes have been explored as homogeneous catalysts for the selective oxidation (in presence of hydrogen peroxide) of benzene to phenol and benzoquinone under mild conditions in an open atmosphere condition.