The reaction of tetrabutyltin with an alumina-containing inorganic oxide such as alumina, silica-alumina or boria-alumina, gives active catalysts for olefin metathesis. Infrared results obtained with tin-modified gamma-alumina and boria-alumina suggest that the active sites arise from an interaction between (n-Bu)(4)Sn and a coordinatively unsaturated Al site, which is created when bridging OH groups react with the tetraalkyltin compound. (C) 1999 Elsevier Science B.V. All rights reserved.14941671275282