Predetermination of chirality at octahedral centres with tetradentate ligands: prospects for enantioselective catalysis

Methods for creation of chiral-at-metal architectures, principally at octahedral metal centres using tetradentate ligands are reviewed. Where achiral ligands are employed, one chiral racemic topography may be formed selectively, and complex resolution strategies have been successfully applied to furnish optically pure systems. The use of chiral ligands has allowed the diastereomeric formation of complexes with stereogenic metal centres, and this area is becoming quite well developed. A number of applications to stoichiometric and catalytic syntheses are described. In certain instances, chiral-at-metal systems outperform their traditional chiral ligand+metal counterparts as a result of the excellent expression of chirality in the active site(s). Prospects for future developments are indicated. (C) 2003 Elsevier B.V. All rights reserved.