Intramolecular cation exchange in ion pairs. Part I. Alkali metal complexes of heterocyclic dicarbaldehydes

Abstract

The e.s.r. spectra of the radical anions of thiophen-2,5-dicarbaldehyde, thieno[3,2-b]thiophen-2,5-dicarbaldehyde, and dithieno[3,2-b:2′,3′-d]thiophen-2,6-dicarbaldehyde, produced by metal reduction in ethereal solvents, showed a marked linewidth alternation which has been attributed to the migration of the counterion between the two equivalent carbonyl groups. A kinetic study of this process in dimethoxyethane and tetrahydrofuran, using sodium or potassium as the reducing agent, allowed the roles played by the size of the anion, the nature of the counterion, and the solvent to be clarified.