The interaction of indium(III) iodide species with substituted ortho- and para-quinones

Abstract

The interactions of substituted ortho- and para-quinones with indium(III) halides and the InI₄^– anion have been studied in non-aqueous solution. para-Quinones and InI₃ give rise to stable 1∶1 adducts, which are diamagnetic in the solid state, but which decompose in solution to form (p-sq)InI₂ derivatives, where p-sq^˙– is the corresponding semiquinonate. With ortho-quinones, the reaction products are (o-sq)InI₂ which react with 4-methylpyridine (pic) to form (o-sq)InI₂pic₂. The electron spin resonance spectra of these products, and their solution chemistry, are discussed. The reactions involve intramolecular one-electron transfer, resulting in oxidation of the iodide ligand. In contrast, the reaction of 3,5-di-tert-butyl-1,2-benzoquinone with InI₄^– apparently involves intermolecular electron transfer; in this case, the products are I₃^– and the corresponding catecholate (dbc), isolated as the solid InI(dbc)pic₂. The mechanisms of these various processes are discussed.