Dicyclopentadienyl-titanium and dicyclopentadienyl-zirconium complexes as catalysts for hydrogenation of olefins

The catalytic hydrogenation of 1-hexene, 4-methyl-2-pentene (65% cis), cyclohexene, styrene, isoprene, 1,3-cyclooctadiene and 1,5-cyclooctadiene has been studied by using different metallocene-type complexes of stoichiometry [Cp2MX2], (M  Ti or Zr), containing equivalent, mixed ansa and bridging cyclopentadienyl ligands. The dichloro complexes (X  Cl) were reduced previously with an excess of magnesium, activated by the addition of a small amount of HgCl2, in the presence or absence of PMePh2. Cyclohexane solutions of the dialkyl derivatives (X Me, CH2SiMe3, CH2PPh2, CH2Ph, Ph, p-MeC6H4 or PPh2) were used in reactions generally carried out in dihydrogen at 7 bar pressure and 90°C, with a concentration of catalyst of around 10−3 M and an olefin-to-catalyst molar ratio of between 300 and 500. The isolation and structural characterization of the new complexes [Ti(η5-C5H5)(η5-C5Me5)Cl(CH2PPh2)], [Ti(η5- C5H5)(η5-C5Me5)(p-MeC6H4)]2], [Ti{μ2-η5-η5-(C5H4)2SiMe2}(CH2PPh2) 2] and [Ti(η5-C5Me5)(η5-C5H4CH2CH2PPh2)Cl2] are also reported.
We thank the Comisión Interministerial de Ciencia y Tecnología (Project PB89-0208) for financial support and Repsol Quimica for a Fellowship to J.C.F.