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fac-Specific syntheses of homochiral [Fe(NN ')(3)](2+) complexes (NN ' = pyridine keto-hydrazone); origins of the stereoselectivity
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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. doi:10.1039/c000815j ISSN 1477-9226.
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Official URL: http://dx.doi.org/10.1039/c000815j
Abstract
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 | ||||
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Subjects: | Q Science > QD Chemistry | ||||
Divisions: | Faculty of Science, Engineering and Medicine > 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 | ||||
ISSN: | 1477-9226 | ||||
Official Date: | 2010 | ||||
Dates: |
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Volume: | Vol.39 | ||||
Number: | No.18 | ||||
Number of Pages: | 8 | ||||
Page Range: | pp. 4447-4454 | ||||
DOI: | 10.1039/c000815j | ||||
Status: | Peer Reviewed | ||||
Publication Status: | Published | ||||
Funder: | Engineering and Physical Sciences Research Council (EPSRC), Yayasan Sarawak Tunku Abdul Rahman Sarawak Scholarship Scheme |
Data sourced from Thomson Reuters' Web of Knowledge
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