Organometallic complexes on alumina

Abstract

Three aspects of the surface chemistry and catalytic activity of organometallic complexes on alumina are covered with particular attention to the effect of the surface concentration of OH − present after various degrees of dehydroxylation. (1) The formation of Lewis acid-Lewis base pair sites during dehydroxylation of alumina. (2) The effect of the degree of dehydroxylation upon the course of the reaction of Mo(CO) 6 with the surface of alumina during heating in He and in H 2. Variously activated Mo(CO) 6 Al 2O 3 are catalysts for the hydrogenation of propylene, the exchange of alkanes with D 2, the hydrogenolysis of alkanes, the hydrogenolysis of cyclopropane, the hydrogenation of CO, and the metathesis of olefins. Metallic Mo(0) Al 2O 3 is among the most active catalysts known for the first three reactions. (3) Organoactinide complexes on alumina. The complexes (Cp′) 2Th(CH 3) 2, (Cp′) 2U(CH 3) 2, and (Cp′) 2ThH 2 (where Cp′ is pentamethylcyclopentadienyl) lead to very active catalysts for the hydrogenation of propylene at −63 °C and the polymerization of ethylene at 25 °C. The surface chemistry of the reactions of the complexes with the surface of alumina during activation has been partially elucidated. High catalytic activity is favored by nearly complete dehydroxylation of the alumina support.