HOMOGENEOUS HYDROGENATION OF CYCLOHEXENE CATALYZED BY COMPLEXES OF RHODIUM AND IRIDIUM

The synthesis and characterization of RhClHN(CH//2CH//2PPh//2)//2 and IrClHN(CH//2CH//2PPh//2)//2 and their catalytic activity in the homogeneous hydrogenation of cyclohexene over the temperature range 20-50 C and 0. 4-1 atm H//2 partial pressure have been investigated. The dependence of the rate of hydrogenation on factors such as the catalyst concentration, the substrate concentration, H//2 pressure and the temperature is reported. A mechanism has been proposed in which the catalysts activate molecular hydrogen by forming dihydrido species of the type MClL(H)//2 left bracket M equals Rh(I), Ir(I) and L equals HN(CH//2CH//2PPh//2)//2 right bracket followed by transfer of hydrogen to the olefin to form the saturated product.