One-electron transfer processes in the reaction of elemental gallium, indium, and tin with tetrahalogeno-ortho-benzoquinones

Abstract

This paper is dedicated to Professor Ronald J . Gillespie on the occasion of his 65th birthday THEODORE A. ANNAN and DENNIS G. TUCK. Can. J. Chem. 67, 1807Chem. 67, (1989. Tin reacts with tetrahalogeno-o-benzoquinones X4C6O2 (X = C1, Br) in refluxing toluene to give the tin(1V) catecholato species Sn(02C6X4)2, and neutral and anionic derivatives have also been obtained. A mixture of Sn + X4C602-o + 12 + I, 10-phenanthroline (phen) yields SnIz(02C6X4)phen. With gallium or indium (= M), the corresponding experiments give derivatives of M" (e.g., [M(OzC6X4)phen]2), or M"' (e.g., MI(02C6X4)phen). Intermediate paramagnetic species were detected in the case of In/Cl4C602-0/;12, and a reaction mechanism involving one-electron transfer processes is proposed on the basis of these results. Solvated crystals of the compound InC1(02C6C14)(C6H7N)3 were obtained from CH2C12 solution, and the structure of this molecule has been determined by X-ray crystallographic methods.Key words: gallium, indium, tin, benzoquinones, oxidation. phCnanthroline-l,l0 (phen) fournit du Sn12(02C6X4)phen. Lorsqu'on rtalise la m&me experience avec du gallium ou de l'indium (= M), on obtient les derives correspondants du M" (e.g., le [M(02C6X4)phen]2) ou du M"' (e.g., MI(O2C6X4)phen). Dans le cas de la reaction du Inlo-CI4C6O2/iI2, on a detect6 la presence d'intermkdiaires paramagnttiques et, sur la base de ces resultats, on propose un mecanisme rtactionnel impliquant des processus de transfer-par un tlectron. En utilisant une solution de CH2C12, on a isole des cristaux solvatCs du InC1(02C6C14)(C6H7N)3 et, faisant appel a des mCthodes de diffraction des rayons-X, on a dttermint la structure de cette moltcule.

Mononuclear Indium and Gallium Tetrachlorocatecholate Complexes

“…The In--N bond length of the pyridine trans to oxygen [2.284 (6),~] is shorter than the In--N bonds of the trans pyridines [2.318(4)°], consistent with chlorine having a weaker trans influence than pyridine. The In--C1 bond length of 2.417 (2) A is similar to those in other In m species for which a range of 2.394-2.538 has been reported (Annan & Tuck, 1989). The displacement ellipsoids of the atoms of the pyridine ring (N2, C12-C16) have an elongated form which may be due to unresolved disorder about the mirror plane.…”

“…For [InCl(py)3(1,2-O2C6Cln)].2Et20 [(1).2Et20], indium powder (0.161 g, 1.42mmol) was added to a solution of tetrachloro-l,2-benzoquinone (0.35 g, 1.42 mmol) in toluene (25 ml) according to the procedure of Annan & Tuck (1989) and heated to reflux for 24 h, resulting in a colour change from red to dark blue-green. The solution was filtered yielding a dark green filtrate to which excess pyridine (0.15 ml, 2.0 mmol) was then added slowly, resulting in an immediate change from a dark green solution to an off-white suspension.…”

“…This was allowed to stir for 18 h affording a deep yellow mixture which was then allowed to settle forming a clear yellow solution and a pale solid; the solution was transfered via syringe to a separate flask and Et20 added as an overlayer. Colourless needle-like X-ray quality crystals of (1).2Et20 were obtained via solvent diffusion at 248 K. For [GaCl(py)(phen)(1,2-O2C6Cln)].3.5py [(2).3.5py], gallium foil (0.5 g, 0.67 mmol) was added to a solution of tetrachloro-1,2-benzoquinone (0.151 g, 0.61 mmol) in toluene (25 ml) and heated to reflux for 24 h, resulting in a colour change from red to a brown-black solution, according to the procedure of Annan & Tuck (1989). The resultant solution was transfered via cannula into a separate flask leaving excess Ga metal as a residue.…”

“…The compounds [InCI(py)3(1,2-O2C6CI4)].2Et20 and [GaCl(py)(phen)(1,2-O2C6Cln)].3.5py were obtained as minor crystalline products from reactions carried out in order to synthesize MII-MU dimer species [M2(O2C6Cln)2(phen)2] (M -Ga or In) by procedures related to those of Tuck and co-workers (Annan & Tuck, 1989). lengths [2.120 (5) and 2.126 (5) A,] and the O--C distances of the catecholate [1.327 (8) and 1.316 (8) ,~] are consistent with the catecholate form as opposed to quinone or semiquinone alternatives.…”

The Reaction of 3,6‐di‐tert‐butyl‐o‐benzoquinone with tin amalgam: Synthesis and structure of tin catecholato complexes

“…Lead reacts with o-quinones more rapidly to form lead(II) catecholate or bis(o-semiquinonate) derivatives [3,4]. The reaction between tin and o-chloranil in refluxing toluene produces bis(tetrachlorocatecholate)tin(IV) [5]. Different o-semiquinonate and catecholate tin species were postulated in reaction mixtures of tin and tert-butyl substituted o-quinones by use of various spectroscopic methods but no solid products were obtained [6,7].…”