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Stereochemical rearrangements of dibromides of hexacoordinated germanium containing amidomethyl and lactamomethyl chelate ligands

Negrebetsky, Vadim V.; Bylikin, Sergey Y.; Shipov, Alexander G.; Baukov, Yuri I.; Bassindale, Alan R. and Taylor, Peter (2003). Stereochemical rearrangements of dibromides of hexacoordinated germanium containing amidomethyl and lactamomethyl chelate ligands. Journal of Organometallic Chemistry, 678(1-2) pp. 39–47.

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For the first time a slow (on the NMR time scale) dynamic exchange between two diastereomers of hexacoordinated dibromogermanes containing two amidomethyl and lactamomethyl C,O-chelate ligands has been observed at room temperature in solution. The influence of temperature and solvent on the ratio of diastereomers was studied. At higher temperatures only one set of signals of the products were detected in the NMR spectra. Based on the dynamic NMR and quantum-chemical calculations (ab initio FR 3-21G), as well as on the structures determined for these compounds in the solid state, a cis-configuration of monodentate ligands was proposed for one of the diastereomers and an all-trans-configuration for the other. At low temperatures interconversion of enantiomers in the cis-diastereomer was observed. In the case of bis[(N-methylacetamido)methyl]dibromogermane the activation and thermodynamic parameters of enantiomerization (DeltaG(298)(#) 12.0+/-0.1 kcal mol(-1), DeltaH(#) 10.7+/-0.3 kcal mol(-1), DeltaS(#) -4.6+/-2.5 cal mol(-1) K-1) and diastereomeric exchange OcCtBrcreversible arrowOtCtBrt (DeltaG(298)(#), 15.0+/-0.1 kcal mol(-1); DeltaH(#) 0.1+/-0.8 kcal mol(-1); DeltaS(#) -50.0+/-5.8 cal mol(-1) K-1; DeltaG(298)degrees -0.2+/-0.1 kcal mol(-1); DeltaHdegrees -0.8+/-0.8 kcal mol(-1); DeltaSdegrees -2.6+/-1.0 cal mol(-1) K-1) were determined. (C) 2003 Published by Elsevier Science B.V.

Item Type: Journal Article
ISSN: 0022-328X
Keywords: germanium; hexacoordination; stereochemical non-rigidity; non-empirical quantum-chemical calculations
Academic Unit/Department: Other Departments > Vice-Chancellor's Office
Other Departments
Science > Life, Health and Chemical Sciences
Interdisciplinary Research Centre: Biomedical Research Network (BRN)
Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 6156
Depositing User: Astrid Peterkin
Date Deposited: 05 Jan 2007
Last Modified: 14 Jan 2016 16:21
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