Si10Cu6N4 Cage Hexacoppersilsesquioxanes Containing N Ligands: Synthesis, Structure, and High Catalytic Activity in Peroxide Oxidations

The synthesis, composition, and catalytic properties of a new family of hexanuclear Cu­(II)-based phenylsilsesquioxanes are described here. Structural studies of 17 synthesized compounds revealed the general principle underlying their molecular topology: viz., a central metal oxide layer consisting of two Cu3 trimers is coordinated by two cyclic [PhSiO1.5]5 siloxanolate ligands to form a skewed sandwich architecture with the composition [(PhSiO1.5)10(CuO)6]2+. In addition to this O ligation by the siloxanolate rings, two opposite copper ions are additionally coordinated by the nitrogen atoms of corresponding N ligand(s), such as 2,2′-bipyridine (compounds 1–9), 1,10-phenanthroline (compounds 10–13), mixed 1,10-phenanthroline/2,2′-bipyridine (compound 14), or bathophenanthroline (compounds 15–17). Finally, the charge balance is maintained by two HO– (compounds 1–7, 10–13, and 15–17), two H3CO– (compound 8), or two CH3COO– (compounds 9 and 14) anions. Complexes 1 and 10 exhibited a high activity in the oxidative amidation oxidation of alcohols. Compounds 1, 10, and 15 are very efficient homogeneous catalysts in the oxidation of alkanes and alcohols with peroxides.