Baruah, Bharat ; Das, Samir ; Chakravorty, Animesh (2003) Vanadate chelate esters of monoionized diols and carbohydrates Coordination Chemistry Reviews, 237 (1-2). pp. 135-146. ISSN 0010-8545
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Official URL: http://linkinghub.elsevier.com/retrieve/pii/S00108...
Related URL: http://dx.doi.org/10.1016/S0010-8545(02)00250-3
Abstract
The title diols are ethane-1,2-diol (H2ed), propane-1,3-diol (H2pd), catechols (H2Rcat) as well as glycerol (H3pt) which act essentially as a substituted diol. The carbohydrates are methylated β-D-galactopyranoside (β-D-H2gp), α-D-mannopyranoside (α-D-H2mp) and β-D -ribofuranoside (β-D -H2rf) and 4,6-benzylidine-α -D-mannopyranoside (α-D -H2bmp), each of which have two vicinal hydroxyl groups having cis disposition. To achieve mononuclearity blocking of three coordination positions by tridentate ONO coordinating salicylaldimines (H2Asal) of α-amino acids and hydrazones (H2Abh) of benzyolacetone and salicyldehyde have been employed. Esters of type [VO(Hed)(Asal)], [VO(Hpd)(Asal)], [VO(H2pt)(Asal)], [VO(β-D-Hgp)(Asal)], [VO(α-D-Hmp)(Asal)], [VO(β-D-Hrf)(Asal)], [VO(Hed)(Abh)], [VO(Hpd)(Abh)], [VO(α-D-Hbmp)(Abh)], [VO(HRcat)(Abh)] have been isolated and characterized. In general, the monoionized diols and carbohydrates are O,O chelated to the metal and the systems generally display hydrogen bonded association in the crystalline state. Species with chiral Asal2- ligands have exclusive endo configuration in the solid state, but in solution a sterically controlled endo-exo equilibrium prevails in the case of the aliphatic diol esters for which the 51V chemical shift is also an index of chelate ring size. The carbohydrate esters do not display endo-exo isomerism in solution. Unlike the aliphatic systems the aromatic diol esters undergo spontaneous catecholase reaction with oxygen in solution, quantitatively affording the corresponding quinone. A catalytic cycle has been constructed for the reaction.
Item Type: | Article |
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Source: | Copyright of this article belongs to Elsevier Science. |
Keywords: | Vanadate Chelate Esters; Vanadate Esters of Aliphatic Diols and Glycerol; Vanadate Esters of Modified Carbohydrates; Diastereoisomeric Equilibria in Vanadate Esters; Vanadate Esters of Catechols; Catecholase Reaction |
ID Code: | 6872 |
Deposited On: | 26 Oct 2010 05:18 |
Last Modified: | 31 Jan 2011 04:42 |
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