Entrapment of metallic palladium and a rhodium(I) complex in a silica sol-gel matrix - Formation of a highly active recyclable arene hydrogenation catalyst

A combined palladium-rhodium catalyst, generated by silica sol-gel-co-entrapment of metallic palladium and [Rh(cod) (mu-Cl)](2), catalyzes under ambient conditions the hydrogenation of toluene and other simple benzene derivatives. The catalyst is perfectly recyclable and promotes at 80 degreesC and 400 psi, also the hydrogenation of polycyclic and sterically hindered arenes that are capable of penetrating the matrix pores. A synergistic effect is assumed to exist between the two metals, as either of the entrapped metallic components is a less active catalyst than the combination of both. (C) 2002 Elsevier Science B.V. All rights reserved.