Rhodium(I) and iridium(I) complexes of the formula [(cod)Rh(OSiMe3(PPh2)] (1). [(cod)RhtOSiMe(2))(PCy1) [(2).] (cod)Rh(OSiMe3)](2) (3). [(cod)Ir(OSiMe3)(PCy3)] (4), and [(cod)[r(OSiMe3)](2) (5). used as catalyst of hydroformylation of the vinylsilanes. Me3SiCH=CH2. Me2PhSiCH=CH2, (MCO)(3)SiCH=CH2. and Me2PhSiCH=CHPh at 80 C and 10atm of H-2/CO tHCO = 1). produced aldehydes (n + iso) as the main products with yields of up to 100%. In the presence of the iridium Complexes (4) and 05). some amounts of ethylsilanes, up to 40%, were obtained, besides aldehydes as a result of hydrogenation of the substrates, In the presence of the rhodiurn complexes (1) and (2). isomerization of iso-aldehydes to 1-siloxypropenes was observed under the reaction conditions. Under Mann of H-2, the rhodium complexes appeared. to be very effective catalysts of vinylsilanes hydrogenation. The hydrogenation reaction products. in addition to ethylsilanes. also included products of homocoupling of vinylsilanes (hydrogenated and non-hydrogenated). (c) 2005 Elsevier B.V. All rights reserved.