HYDROGENATION AND ISOMERIZATION OF OLEFINS WITH DIPHENYLPHOSPHINOMETHYL HYDRIDE ZIRCONIUM, [CP2ZRH(CH2PPH2)]N, A SELECTIVE HOMOGENEOUS CATALYST

Various linear and cyclic mono- and di-olefins and aromatic substrates have been investigated for catalytic hydrogenation and isomerization with the diphenylphosphinomethyl hydride compound [Cp2ZrH(CH2PPh2)]n. Selective formation of cycloheptene, cyclooctene and 1,2,3,4-tetrahydroanthracene is obtained from cycloheptatriene, cyclooctadiene (1,5- or 1,3-COD) and anthracene, respectively. Catalytic isomerization of 1-hexene to E-2-hexene and 1,5-COD to 1,3-COD occurs rapidly at 80-degrees-C. The kinetic study of the catalytic selective hydrogenation of 1,3-COD to cyclooctene with [Cp2ZrH(CH2PPh2)]n has been investigated. The dependence of the hydrogenation rate as a limiting step and the half order observed for the catalyst in the kinetic law make it possible to propose an active homobimetallic Zr(IV)Zr(II) species in which both zirconium atoms are bridged by the diphenylphosphinomethyl ligand. A mechanism for the hydrogenation of conjugated diolefins is postulated.