The first tris-heteroleptic copper cage, ligated by germsesquioxanes, 2,2′-bipyridines and 3,5-dimethylpyrazolates. Synthesis, structure and unique catalytic activity in oxidation of alkanes and alcohols with peroxides

Self-assembly reaction of copper(II) ions and triple set of ligands (phenylgermaniumsesquioxane, 2,2′-bipyridine, 3,5-dimethylpyrazolate) results in the formation of the first example of tris-heteroleptic copper cage product (PhGeO2)10Cu6(2,2′-bipy)2(3,5-Me2Pz)2 (1). The ligation styles of complex’ components are different and includes (i) O-coordination from two cyclic pentamembered germsesquioxanes, (ii) N-coordination from two deprotonated 3,5-dimethylpyrazoles, (iii) N-ligation from two 2,2′-bipyridines. These features as well as other details of structure of 1 were established by X-day diffraction study. Analysis of the regioselectivity parameters found for the oxidation of linear and branched alkanes led to a conclusion that the reaction mechanism includes the formation of HO• radicals. However, the kinetic peculiarities of the cyclohexane oxidation with H2O2 in acetonitrile allowed to assume that the oxidation proceeds predominantly in a cavity generated inside of the tris-heteroleptic copper cage but not in the solution volume.