Group 4 metallocene complexes bearing cholestanol-derived substituents at the Cp-rings-their synthesis and use in propene polymerization catalysis

Article abstract of DOI:10.1016/0022-328X(94)87161-2

Two series of Group 4 bent metallocene complexes bearing cholestanol-derived substituents at their Cp-rings have been prepared. 5α-Cholestan-3α-ol was converted to the 3α-mesylate.Nucleophilic substitution with CpNa, followed by deprotonation and treatment with ZrCl4(THF)2 gave bis<η⁵-5α-cholestan-3β-yl)cyclopentadienyl>zirconium dichloride 3β-5. 5α-Cholestan-3-one 6 was converted to the corresponding fulvene, methyl lithium was added and deprotonation and addition to ZrCl4(THF)2 furnished bis<η⁵-(3β-methyl-5α-cholestan-3α-yl)cyclopentadienyl>zirconium dichloride (11b).Treatment of the chiral Cp-substituted zirconocene dichlorides with a large excess of methyl alumoxane gave homogeneous Ziegler catalysts.Propene polymerization proceeded with overall stereochemical chain end control to give partly isotactic polypropylene.Keywords: Zirconium; Cholestanol; Polymerization