Russian Chemical Bulletin, International Edition, Vol. 56, No. 2, pp. 261—266, February, 2007 261 Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 253—258, February, 2007. 1066-5285/07/5602-0261 © 2007 Springer Science+Business Media, Inc. Reactions of organotin chlorides R 2 SnCl 2 (R = Et, Bu t , or Ph) with lithium 4,6-di(tert-butyl)-N-(2,6-diisopropylphenyl)-o-amidophenolate. Synthesis and structures of tin(IV) o-iminoquinone complexes A. V. Piskunov,  I. A. Aivaz´yan, G. A. Abakumov, V. K. Cherkasov, O. V. Kuznetsova, G. K. Fukin, and E. V. Baranov G. A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, 49 ul. Tropinina, 603950 Nizhny Novgorod, Russian Federation. Fax: +7 (831 2) 62 7497. E-mail: pial@iomc.ras.ru The exchange reactions of tin diorganohalides R 2 SnCl 2 (R = Et, Bu t , or Ph) with lithium amidophenolate APLi 2 (AP is the 4,6-di(tert-butyl)-N-(2,6-diisopropylphenyl)-o-iminobenzo- quinone dianion) in tetrahydrofuran produced the new five-coordinate (Et 2 SnAP(THF) (3)) and four-coordinate (R 2 SnAP (R = Bu t , Ph)) tin(IV) complexes. The reaction of Ph 2 SnCl 2 with APLi 2 in a nonpolar solvent (hexane or toluene) is accompanied by the additional redox process giving rise to the paramagnetic complex Ph 2 Sn(ImSQ)Cl (6) (ImSQ is the 4,6-di(tert- butyl)-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone radical anion). The molecular struc- tures of complexes 3 and 6 were established by X-ray diffraction. Key words: o-iminobenzoquinone, tin, o-iminobenzosemiquinolate, amidophenolate, elec- tron paramagnetic resonance, X-ray diffraction study. o-Iminobenzoquinones are structural analogs of both o-quinones and o-diimines, being intermediate between these groups of compounds. Among these classes, the coordination chemistry of o-iminoquinones has been less well studied. Like o-quinones and o-diimines, o-imino- benzoquinones, being involved in complexes with metals, can undergo two-step one-electron reduction to form the o-iminosemiquinone radical anions and the amido- phenolate dianion (Scheme 1). Scheme 1 The introduction of various substituents at the nitro- gen atom of o-iminobenzoquinone enables the variation of steric shielding of the metal center in complexes in a wide range. For example, homoligand transition metal complexes with ligands based on o-iminobenzoquinone containing the phenyl substituent at the nitrogen atom can contain three o-iminosemiquinone ligands, which form a six-co- ordinate environment of metal. 1—3 The use of sterically more hindered o-iminoquinones, in particular, those con- taining the 2,6-diisopropylphenyl group at the nitrogen atom, allows the synthesis of iron, cobalt, and manganese complexes containing only two iminosemiquinone ligands, which corresponds to the lower-valence and low- coordination state of metal. 4—7 This is reflected in chemi- cal activity of the resulting compounds. Since these com- pounds are valent- and coordinatively unsaturated, they can fix small molecules. 5 The presence of the redox-ac- tive o-amidophenolate ligand imparts new properties to main-group metal complexes, as exemplified by the re- versible binding of molecular oxygen by antimony(V) com- plexes. 8 Recently, we have synthesized the homoligand tin(II) and tin(IV) o-amidophenolate complexes 9 based on steri- cally hindered 4,6-di(tert -butyl)-N-(2,6-diisopropyl- phenyl)-o-iminobenzoquinone (1). In the present study, we describe the synthesis and structures of a series of tin(IV) amidophenolate complexes containing alkyl and aryl substituents at the metal atom. Results and Discussion The exchange reactions of alkali metal derivatives with metal halides are widely used for the synthesis of various coordination compounds. Dilithium salt 2 can easily be prepared by reduction of o-iminoquinone 1 with excess lithium both in polar (THF or Et 2 O) and nonpolar (tolu- ene or hexane) organic solvents (Scheme 2).