Electron-Transfer Processes in Indium(II) Iodide−o-Quinone Systems

Abstract

Indium(II) iodide reacts with various substituted o-quinones in nonaqueous solution by successive one-electron-transfer reactions to give (SQ)InI(2) products (SQ = semiquinonate radical anion). Electron spin resonance spectroscopy demonstrates the presence of both mono- and diradical species in the reaction mixture. Addition of 4-picoline to a mixture of In(2)I(4) and TBQ (=3,5-di-tert-butyl-o-quinone) in toluene causes the precipitation of the indium(III)-semiquinonate complex (TBSQ)InI(2)(pic)(2) whose structure has been established by X-ray crystallography: space group P&onemacr;, with a = 13.013(3) Å, b = 13.317(3) Å, c = 10.828(5) Å, alpha = 97.71(3) degrees, beta = 107.98(3) degrees, gamma = 103.92(3) degrees, V = 1684.8(1.2) Å(3), Z = 2. Refinement converged at R = 0.051 and R(w) = 0.064 for 5918 reflections at 23 degrees C. The InO(2)N(2)I(2) kernel is pseudooctahedral, and the structure confirms the presence of the semiquinonate ligand. A reaction scheme which incorporates these results is proposed.

Spectroscopic and crystallographic studies of adducts of aluminium trichloride with cyclic ketones, para-quinones and ortho-quinones

“…Crystallographic analysis of the derivative (dbbsq ؒ ) InI 2 (pic) 2 (dbbsq ؒ = 3,5-di-tert-butyl-o-benzosemiquinonate anion; pic = 4-methylpyridine) confirmed the presence of the semiquinonate ligand in this six-co-ordinate indium() complex. 2, 24 As in the case of the p-quinone adducts discussed above, weak ESR activity was detected from solid samples of the o-quinone derivatives, and this is again believed to be due to impurities. Solutions of these compounds show much more intense spectra.…”

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

“…In the case where sq Ϫ = 3,5di-tert-butyl-o-benzosemiquinonate (dbbsq) an X-ray crystallographic study showed that this compound was structurally identical with the material formed in the reaction between indium() iodide and the corresponding ortho-quinone. 5 (Unit cell dimensions, a = 13.0097 (5) 2) Å 3 ). We also attempted to prepare adducts with pyridine as the neutral donor, but in each case the analytical results were less than satisfactory, except in the case of phenanthrenequinone (Found: C, 39.…”

“…The molecularity of these compounds is not known, but treatment with excess picoline yields the bis-adduct, which in the case of (dbbsq)InI 2 pic 2 was shown to be crystallographically identical with the mononuclear six-coordinate compound obtained from the reaction the reaction of dbbq and In 2 I 4 . 5 The initial overall reaction is…”

“…ref. 5). In a dimeric molecule, indium has pentagonal bipyramidal stereochemistry, and the consequent lowering of strain therefore serves to move eqn.…”

The reactions of elemental germanium with 3,5-di-tert-butyl-1,2-benzoquinone

“…The mechanism of electron transfer in the redox reactions of Main Group elements and their compounds, has been the subject of a number of publications from this laboratory. [1][2][3][4] The most important general conclusion, based on both preparative and spectroscopic investigations, is that processes which were earlier believed to involve the concerted transfer of a pair of electrons in fact proceed via successive single-electron transfers. We have also demonstrated that intermolecular electron transfer can be a significant factor in such systems.…”