A Family of Hexacopper Phenylsilsesquioxane/Acetate Complexes: Synthesis, Solvent‐Controlled Cage Structures, and Catalytic Activity
Anna Y. Zueva, Аlexey N. Bilyachenko, Ivan S. Arteev, Victor N. Khrustalev, Павел В. Дороватовский, Lidia S. Shul’pina, Nikolay S. Ikonnikov, Evgenii I. Gutsul, Karim G. Rahimov, Elena S. Shubina, Nuno Reis Conceição, Kamran T. Mahmudov⧫, M. Fátima C. Guedes da Silva, Armando J. L. Pombeiro
Abstract
Abstract Convenient self‐assembly synthesis of copper(II) complexes via double (phenylsilsesquioxane and acetate) ligation allows to isolate a family of impressive sandwich‐like cage compounds. An intriguing feature of these complexes is the difference in the structure of a pair of silsesquioxane ligands despite identical (Cu 6 ) nuclearity and number (four) of acetate fragments. Formation of particular combination of silsesquioxane ligands (cyclic/cyclic vs condensed/condensed vs cyclic/condensed) was found to be dependent on the synthesis/crystallization media. A combination of Si 4 ‐cyclic and Si 6 ‐condensed silsesquioxane ligands is a brand new feature of cage metallasilsesquioxanes. A representative Cu 6 ‐complex ( 4 ) (with cyclic silsesquioxanes) exhibited high catalytic activity in the oxidation of alkanes and alcohols with peroxides. Maximum yield of the products of cyclohexane oxidation attained 30 %. The compound 4 was also tested as catalyst in the Baeyer‐Villiger oxidation of cyclohexanone by m‐ chloroperoxybenzoic acid: maximum yields of 88 % and 100 % of ϵ‐caprolactone were achieved upon conventional heating at 50 °C for 4 h and MW irradiation at 70 or 80 °C during 30 min, respectively. It was also possible to obtain the lactone (up to 16 % yield) directly from the cyclohexane via a tandem oxidation/Baeyer‐Villiger oxidation reaction using the same oxidant.