| Abstrakt: |
The interaction of molecular hydrogen with [Rh(PPh3)3]+(1a) “immobilized” in the interlamellar spaces of montmorillonite resulted in the formation of a monohydrido complex, [RhIIH(PPh3)3] (2a), characterized by electrochemical data of the clay-loaded electrode, IR, EPR and hydrogen absorption studies. Heterogenized homogeneous catalytic hydrogenation of cyclohexene catalysed by 1awas investigated in the temperature range 283–313 K. The order of reaction with respect to cyclohexene and hydrogen concentration is fractional and first order with respect to catalyst concentration. Thermodynamic parameters ΔH0and ΔS0corresponding to the formation of the monohydrido species were found to be 18 kcal mol−1and 61 e.u., respectively. The activation enthalpy, ΔH‡, and entropy, ΔS‡, for the hydrogenation of cyclohexene by the RhII—H complex in clay are more negative by about 2 kcal mol−1and 7 e.u. compared to Wilkinson's catalyst, RhCl(PPh3)3(1), in homogeneous solution. |
