Total Spontaneous Resolution of Chiral Covalent Networks from Stereochemically Labile Metal Complexes
✍ Scribed by Anna Johansson; Mikael Håkansson; Susan Jagner
- Publisher
- John Wiley and Sons
- Year
- 2005
- Tongue
- English
- Weight
- 235 KB
- Volume
- 11
- Category
- Article
- ISSN
- 0947-6539
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✦ Synopsis
Abstract
Stereochemically labile copper and zinc complexes with the N,N′‐dimethylethylenediamine ligand (dmeda) have been shown to be promising precursors for the total spontaneous resolution of chiral covalent networks. (N,N′)‐[Cu(NO~3~)~2~(dmeda)]~∞~ crystallises as a conglomerate and yields either enantiopure (R,R)‐1 or enantiopure (S,S)‐1. A mixed‐valence copper(I/II) complex, [{Cu^II^Br~2~(dmeda)}~3~(Cu^I^Br)~2~]~∞~ (2), which crystallises as a pair of interpenetrating chiral (10,3)‐a nets, is formed from CuBr, CuBr~2~ and dmeda. One net contains ligands with solely (R,R) configuration and exhibits helices with (P) configuration while the other has solely (S,S)‐dmeda ligands and gives rise to a net in which the helices have (M) configuration. The whole crystalline arrangement is racemic, because the interpenetrating chiral nets are of opposite handedness. With zinc chloride (R,S)‐[ZnCl(dmeda)~2~]~2~[ZnCl~4~] (3) is obtained, which is a network structure, although not chiral. Total spontaneous resolution of stereochemically labile metal complexes formed from achiral or racemic building blocks is suggested as a viable route for the preparation of covalent chiral networks. Once the absolute structure of the compound has been determined by X‐ray crystallography, a quantitative determination of the enantiomeric excess of the bulk product can be undertaken by means of solid‐state CD spectroscopy.