Chiral nonracemic metal complexes

In principle a metal atom may also be stereogenic (and therefore influence the stereoselectivity), but a separate category is not needed since chiral nonracemic metal complexes containing achiral ligands are rare in asymmetric synthesis [53]. 

The effectiveness of various substituted BINOL ligands 12-16 in the Zr(IV)-or Ti(IV)-catalyzed enantioselective addition of allyltributyltin to aldehydes was also investigated by Spada and Umani-Ronchi [21], The number of noteworthy examples of asymmetric allylation of carbonyl compounds utilizing optically active catalysts of late transition metal complexes has increased since 1999. Chiral bis(oxazolinyl)phenyl rhodium(III) complex 17, developed by Mo-toyama and Nishiyama, is an air-stable and water-tolerant asymmetric Lewis acid catalyst [23,24]. Condensation of allylic stannanes with aldehydes under the influence of this catalyst results in formation of nonracemic allylated adducts with up to 80% ee (Scheme 3). In the case of the 2-butenyl addition reac-... 

One of the most elegant methods for the selective formation of C—O bonds is the catalytic Jacobsen-Katsuki epoxidation, the enantioselective synthesis of optically active epoxides by oxygen-transfer reactions with chiral, nonracemic manganese 0x0 salen complexes. These complexes have been suggested as the catalytically active species in epoxidations catalyzed by metal-salen and porphyrin complexes [78]. One of these complexes was for the first time isolated and characterized by Feichtinger and Planner through ESI-MS studies [79]. 

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