Howson, Suzanne E., Allan, Laura E. N., Chmel, Nikola P., Clarkson, Guy J., Deeth, Robert J., Faulkner, Alan D., Simpson, Daniel H. and Scott, Peter. (2011) Origins of stereoselectivity in optically pure phenylethaniminopyridine tris-chelates M(NN′)3n+ (M = Mn, Fe, Co, Ni and Zn). Dalton Transactions, Vol.40 (No.40). pp. 10416-10433. ISSN 1477-9226

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Abstract

One-pot reactions of 2-pyridinecarboxaldehyde, chiral phenylethanamines and Fe(II) give single diastereomer fac diimine complexes at thermodynamic equilibrium so that no chiral separations are required (d.r. > 200 : 1). The origins of this stereoselectivity are partly steric and partly a result of the presence of three sets of inter-ligand parallel-offset pi-stacking interactions. Mn(II), Co(II), Co(III), Ni(II) and Zn(II) give similar fac structures, alongside the imidazole analogues for Fe(II). While most of the complexes are paramagnetic, the series of molecular structures allows us to assess the influence of the p-stacking present, and there is a strong correlation between this and the M-N bond length. Fe(II) is close to optimal. For the larger Zn(II) ion, very weak pi-stacking leads to poorer measured stereoselectivity (NMR) but this is improved with increased solvent polarity. The mechanism of stereoselection is further investigated via DFT calculations, chiroptical spectroscopy and the use of synthetic probes.

Item Type:	Journal Article
Divisions:	Faculty of Science > Chemistry
Journal or Publication Title:	Dalton Transactions
Publisher:	Royal Society of Chemistry
ISSN:	1477-9226
Date:	2011
Volume:	Vol.40
Number:	No.40
Number of Pages:	18
Page Range:	pp. 10416-10433
Identification Number:	10.1039/c1dt10588d
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
URI:	http://wrap.warwick.ac.uk/id/eprint/39641

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