The central chirality of the metal atom and configurational relations in asymmetric reactions catalysed by metal complexes

The recently published data on the dependence of the configuration of the reaction product on the structure of a catalytic metal complex (or an intermediate determining the asymmetric induction) in asymmetric catalytic reactions of hydrogen-transfer hydrogenation of acetophenone, hydroformylation of styrene, allylic alkylation of 1,3-diphenylprop-2-enyl acetate and alkylation of benzaldehyde with dialkylzinc are systematised. The applicabilities of octant and quadrant projections of the complexes are compared in order to establish the relationships between their structures and the enantioselectivities of the reactions. The known mechanisms of asymmetric induction in these reactions are discussed with regard to the C₁ or C₂ symmetry of the catalytic complex. The reasons for a decrease in the enantioselectivities of hydrogen-transfer hydrogenation, hydroformylation and alkylation by dialkylzinc [in the absence of Ti(OPrⁱ)₄] when performed with complexes with chiral C₂-symmetric ligands (as compared with complexes with asymmetric ligands) are considered.