Improved palladium and nickel catalysts heterogenised on oxidic supports (silica, MCM-41, ITQ-2, ITQ-6)

Two series of solid catalysts in which a chiral palladium or nickel complex with Schiff bases as ligands have been immobilized on ordered mesoporous silica supports (MCM-41), delaminated ITQ-2, ITQ-6 zeolites and amorphous silica have been prepared. Hydrogenation of alkenes and imines was studied with the homogeneous as well as with the counterpart heterogenized catalysts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs of 1,000,000 h(-1). A moderate acidity in the support increases the catalytic activity considerably, and the easy recoverable immobilized catalysts can duplicate the activity of the homogeneous analogues. No deactivation of the catalysts was observed after repeated recycling.