SiCuN 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 Cu trimers is coordinated by two cyclic [PhSiO] siloxanolate ligands to form a skewed sandwich architecture with the composition [(PhSiO)(CuO)]. 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 HCO (compound 8), or two CHCOO (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.