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Soluble Gold and Palladium Complexes Heterogenized on MCM-41 Are Effective and Versatile Catalysts



Chiral Schiff base–gold and –palladium complexes were immobilized on ordered mesoporous silica supports (MCM-41), and their catalytic hydrogenation ability is studied and compared with that of their homogeneous counterparts. The high accessibility introduced by the structure of the supports allows the preparation of highly efficient immobilized catalysts with TOFs of up to 6000 h–1 for the hydrogenation of diethyl itaconate. The easily recoverable immobilized catalysts duplicate the activity of their homogeneous analogues, and no deactivation of the catalysts is observed after repeated recycling. Gold(III) homogeneous or heterogenized complexes also catalyze the homocoupling of arylboronic acids or alkynes to afford symmetrical biaryls, whereas the respective gold(I) and palladium(II) complexes catalyze the corresponding cross-coupling reaction.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)