Early Transition Metal Permethylpentalene Complexes for the Polymerization of Ethylene

A series
of group 4 permethylpentalene–cyclopentadiene mixed
sandwich complexes have been synthesized including the mono- and bis-cyclopentadienyl
derivatives Pn*MCp2–xClx (Pn* = η8-C8Me6, M = Ti, Zr, Hf, x = 0, 1) and the monopentamethylcyclopentadienyl
species Pn*MCp*Cl (Pn* = η8-C8Me6, M = Ti, Zr, and Hf). The compounds were all characterized via a
range of techniques including single crystal X-ray diffraction allowing
for comparison of trends descending the group as well as the effect
of permethylation of the cyclopentadienyl moiety. The complexes have
been tested for their efficacy as catalysts for the solution polymerization
of ethylene, and Pn*ZrCpCl was found to give the highest activity
of 6993 kg mol–1 h–1 bar–1 at 80 °C with a [MAO]0/[Zr]0 ratio of
1000 and 2 bar pressure of ethylene gas in hexane.