Sn(IV) centers have been grafted onto mesoporous MCM-41 using different RnSnX4-n precursors. For a successful incorporation of the tin, one or two alkyl substituents are beneficial. The calcined samples are able to activate a carbonyl bond for nucleophilic attack as it could be shown by in situ IR spectroscopy. The resulting catalysts are active for the Baeyer-Villiger oxidation of various substrates with hydrogen peroxide and achieve good conversions and selectivities. Chemoselective oxidations toward unsaturated lactones are obtained from unsaturated ketones. The Lewis acidity and the catalytic performance of the grafted Sn(IV) centers are very similar to the directly synthesized Sn-MCM-41, but lower than those of the Sn-Beta zeolite. (C) 2003 Elsevier Inc. All rights reserved.