Synthesis of racemic chiral-at-metal complexes of the Group 4 metals

A protocol for asymmetric synthesis of chiral-at-metal complexes is describ ed, but enantiomerically-enriched products can not be isolated due to forma tion of complexes between the Group 4 metallocene products and the borane b y-products. An efficient method for synthesis of racemic chiral-at-metal me tallocenes, through lithium chloride catalysed ligand redistribution reacti ons, is described. Sterically-hindered racemic chiral-at-metal complexes ar e prepared by nucleophilic substitution of prochiral dichlorides. (C) 2000 Elsevier Science S.A. All rights reserved.