Supported Tetrahedral Oxo-Sn Catalyst: Single Site, Two Modes of Catalysis

• Published in: Journal of the American Chemical Society Vol. 138; no. 13; pp. 4294 - 4297
• Main Authors: Beletskiy, Evgeny V, Hou, Xianliang, Shen, Zhongliang, Gallagher, James R, Miller, Jeffrey T, Wu, Yuyang, Li, Tiehu, Kung, Mayfair C, Kung, Harold H
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 06-04-2016; American Chemical Society (ACS)
• Subjects: INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/jacs.5b13436

Mild calcination in ozone of a (POSS)-Sn-(POSS) complex grafted on silica generated a heterogenized catalyst that mostly retained the tetrahedral coordination of its homogeneous precursor, as evidenced by spectroscopic characterizations using EXAFS, NMR, UV–vis, and DRIFT. The Sn centers are accessible and uniform and can be quantified by stoichiometric pyridine poisoning. This Sn-catalyst is active in hydride transfer reactions as a typical solid Lewis acid. However, the Sn centers can also create Brønsted acidity with alcohol by binding the alcohol strongly as alkoxide and transferring the hydroxyl H to the neighboring Sn–O–Si bond. The resulting acidic silanol is active in epoxide ring opening and acetalization reactions.