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

The interactions of substituted ortho- and pam-quinones with indium(III) halides and the InI4- anion have been studied in nan-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)InI(2)pic(2). 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 I-3(-) and the corresponding catecholate (dbc), isolated as the solid InI(dbc)pic(2). The mechanisms of these various processes are discussed.