HYDROGENATION AND HYDROSILYLATION ACTIVITY OF HOMOGENEOUS AND IMMOBILIZED DICARBONYL(2,4-PENTANEDIONATO)RHODIUM COMPLEXES

A series of homogeneous R-C(COCH3)2Rh(CO)2 complexes (where R=H, n-C3H7, (CH3)3Si(CH2)3 and (C2H5O)3Si(CH2)3) was prepared. The immobilized analogues were synthesized using (C2H5O)3Si(CH2)3CH(COCH3)2 in the following ways: (i) by reaction of the complex (C2H5O)3Si(CH2)3C(COCH3)2Rh(CO)2 with untreated silica; (ii) by reaction of Rh2(CO)4Cl2 With silica functionalized by (C2H5O)3Si(CH2)3CH(COCH3)2; (iii) by treatment of Rh2(CO)4Cl2 with a polycondensate prepared by hydrolysis and condensation of (C2H5O)3Si(CH2)3CH(COCH3)2 and tetraethoxysilane; (iv) by sol-gel processing of (C2H5O)3Si(CH2)3C(COCH3)2Rh(CO)2 and tetraethoxysilane. The homogeneous complexes and their immobilized analogues are efficient catalysts for hydrogenation and hydrosilylation of alkenes. Their activities are discussed in relation to their structures and method of preparation.