Si 10 Cu 6 N 4 Cage Hexacoppersilsesquioxanes Containing N Ligands: Synthesis, Structure, and High Catalytic Activity in Peroxide Oxidations
Résumé
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 3 trimers is coordinated by two cyclic [PhSiO 1.5 ] 5 siloxanolate ligands to form a skewed sandwich architecture with the composition [(PhSiO 1.5) 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 H 3 CO − (compound 8), or two CH 3 COO − (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.
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