Electrochemistry and organic chemistry Cr(III)(EDTA)/Cr(II)(EDTA) and related couples

White, James Charles Peter (1990) Electrochemistry and organic chemistry Cr(III)(EDTA)/Cr(II)(EDTA) and related couples. University of Southampton, Doctoral Thesis.

Abstract

Cr(III) (EDTA), Cr(III)(CyDTA), Cr(III))(DTPA) and Cr(III)(TTHA) all undergo a reversible one-electron reduction at a mercury electrode, with formal potentials between -1.20 and -1.26 V vs. SCE. The Cr(II)L complexes are, therefore, all strong reducing agents. With appropriate choice of electrolysis conditions, high conversion of Cr(III)L to Cr(II)L may be achieved with good current efficiency. The Cr(II)L species may be used for a range of organic reductions. The chemistry of Cr(II)L appears generally similar to that of CrSO₄ or CrCl₂. It is characterized by rather slow reactions via organochromium intermediates, formed by the displacement of either an H₂O ligand from an unchelated site, or one of the carboxylate arms of the chelating ligand L. Hence, these reductions occur via an inner sphere mechanism. Some readily reduced substrates may, however, react with Cr(II)L in a simple outer sphere electron transfer. In both cases, the stronger reducing power of Cr(II)L compared with Cr²⁺ leads to some different products. Efficient extraction of Cr(III)(CyDTYA) and Cr(II) (CyDTA) into dichloromethane can be achieved with tetrabutylammonium ions, and should allow the use of Cr(II)(CyDTA) as a reducing agent in a two phase system with phase transfer catalysis.

This record has no associated files available for download.

Contributors

Download statistics