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

Abstract

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 [Cp 2MX 2], (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 HgCl 2, in the presence or absence of PMePh 2. Cyclohexane solutions of the dialkyl derivatives (X Me, CH 2SiMe 3, CH 2PPh 2, CH 2Ph, Ph, p-MeC 6H 4 or PPh 2) 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(η 5-C 5H 5)(η 5-C 5Me 5)Cl(CH 2PPh 2)], [Ti(η 5- C 5H 5)(η 5-C 5Me 5)( p-MeC 6H 4)] 2], [Ti{μ 2-η 5-η 5-(C 5H 4) 2SiMe 2}(CH 2PPh 2) 2] and [Ti(η 5-C 5Me 5)(η 5-C 5H 4CH 2CH 2PPh 2)Cl 2] are also reported.