Isotope Effects Associated with α‐Olefin Insertion in Zirconocene‐Based Polymerisation Catalysts: Evidence for an α‐Agostic Transition State

The hydrodimerization of trans ‐ and of cis ‐1‐deuterio‐l‐hexene to the threo ‐ and erythro ‐isomers of 6‐deuterio‐5‐deuteriomethylundecane with the chiral pre‐catalyst rac ‐ethylenebis(tetrahydroindenyl)zirconium dichloride gave diastereomeric ratios of 2.4:1, which, depending on ( E )‐ or ( Z )‐configuration of the diene, reverse. The results confirm observations by Pino et al. that α‐olefins insert into Zr—H and Zr—alkyl bonds with opposite enantiofacial orientation.