fac-Specific syntheses of homochiral [Fe(NN ')(3)](2+) complexes (NN ' = pyridine keto-hydrazone); origins of the stereoselectivity
Sebli, Cynthia Paul, Howson, Suzanne E., Clarkson, Guy J. and Scott, Peter. (2010) fac-Specific syntheses of homochiral [Fe(NN ')(3)](2+) complexes (NN ' = pyridine keto-hydrazone); origins of the stereoselectivity. Dalton Transactions, Vol.39 (No.18). pp. 4447-4454. ISSN 1477-9226Full text not available from this repository.
Official URL: http://dx.doi.org/10.1039/c000815j
The 2-pyridinehydrazones (from condensation of pyridine-2-carbaldehyde and hydrazines) have previously been noted to have poor ligating ability as a result of a sterically demanding planar conformation. Destabilisation of this conformation is achieved through simple use of the ketohydrazones, and as a result the diamagnetic chiral tris-bidentate diimine complexes fac-[FeL3](2+) are readily isolated. In the solid state, inter-ligand pi-pi stacking and complex/counter-ion H-bonding are apparent, and these features persist in solution according to dynamic NMR spectra, which also indicate extremely high stereoselectivity for the fac isomers (> 200 : 1). The compounds crystallise as conglomerates, and time-resolved CD spectra of non-racemic samples indicate a high degree of persistence of chirality (racemisation t(1/2) ca 77 min). Variations of solvent and counter-ion indicate that H-bonding is unimportant in determining the structure of the cation. The fac-selectivity arises in the induction of a chiral conformation in the coordinated ligand, and the fact that such non-planar ligands can only be accommodated about the Fe(II) centre if they all have the same absolute configuration. Adding a hydrazine N-methyl group increases the steric demand further, while retaining the novel non-planar conformation, and as a result paramagnetic chiral bis-bidentate complexes such as [FeL27(CH3CN)(2)](2+) are readily available.
|Item Type:||Journal Article|
|Subjects:||Q Science > QD Chemistry|
|Divisions:||Faculty of Science > Chemistry|
|Library of Congress Subject Headings (LCSH):||Stereochemistry, Pyridine, Chelates, Complex compounds -- Synthesis|
|Journal or Publication Title:||Dalton Transactions|
|Publisher:||Royal Society of Chemistry|
|Number of Pages:||8|
|Page Range:||pp. 4447-4454|
|Funder:||Engineering and Physical Sciences Research Council (EPSRC), Yayasan Sarawak Tunku Abdul Rahman Sarawak Scholarship Scheme|
1 A. Grabulosa, M. Beley and P. C. Gros, Eur. J. Inorg. Chem., 2008,
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