Topologically chiral metal complexes

Abstract In general, asymmetric catalysts are based on the combination of a chiral organic ligand and a metal ion. Here we show that future research should also focus on complexes in which the chirality resides only at the metal center, as the result of a given topology of coordination of achiral ligands to the metal ion. Here we make a brief presentation of the methods available for preparing such compounds as well as the very few examples of enantioselective reactions catalyzed by chiral-at-metal complexes. 

There are also chiral topological supramolecular structures in molecular knots, rotaxanes, catenanes, and Borromean rings with metal complexes.73,74... 

Bis 8-quinolmato metal complexes are representative examples of distorted octahedral structures of the type (87). It was noted that these systems bear a topological resemblance to the chiral, octahedral, active metal sites that have been proposed for supported Ziegler-Natta catalysts, and are interesting for modeling catalytic properties. Similar comportment has been observed with diamine bis (phenolate) ligands. ... 

Organometallics as a novel class of SDAs also offer the chance to generate new framework topologies, and this has in fact been accomplished in one case (see below) In particular, it might also be possible to discover the "Holy Grail" of synthetic zeolite chemistry, namely, the preparation of a chiral zeotype structure by using metal complexes as SDAs with a chiral shape. 

The wide diversity of topologies that can today be found for NHC-precursors, together with the different efficient metallation strategies [6], have provided a large set of Ir—NHC complexes among which monodentate, bis-chelate and chiral... 

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