FULL PAPER DOI: 10.1002/ejic.200701115 New Germanium Complexes Containing Ligands Based on 4,6-Di-tert-butyl- N-(2,6-diisopropylphenyl)-o-iminobenzoquinone in Different Redox States Alexandr V. Piskunov,* [a] Igor A. Aivaz’yan, [a] Andrey I. Poddel’sky, [a] Georgii K. Fukin, [a] Evgenii V. Baranov, [a] Vladimir K. Cherkasov, [a] and Gleb A. Abakumov [a] Keywords: Germanium / Metallacycles / N,O ligands / EPR spectroscopy / X-ray diffraction The exchange reaction of lithium o-amidophenolate, (AP)Li 2 , derived from the reaction of 4,6-di-tert-butyl-N-(2,6-diisopro- pylphenyl)-o-iminobenzoquinone (imQ) with GeCl 4 in hex- ane or thf leads to (AP) 2 Ge (1) (AP is a dianion of imQ). The latter was also obtained by the interaction of GeCl 2 ·dioxane and (ISQ)Li in toluene (ISQ is a radical anion of imQ). The reaction of (AP)Li 2 with GeCl 2 ·dioxane in thf results in the formation of germylene 2, [(AP)Ge (2)], which reduces neu- tral imQ to give compound 1. The exposure of 1 in thf to anhydrous HCl in a 1:1 molar ratio leads to its o-aminophen- Introduction Diamide ligands were shown to be very useful in ob- taining stable derivatives of group 14 elements, [1,2] particu- larly germanium, [1g–1k] in the divalent state. A significant part of these compounds is based on diazabutadiene-type ligands. One of their most important features is the ability to form not only dianion derivatives but radical anion com- plexes containing divalent germanium. [1h–1g] Redox-active ligands like diazabutadienes, which can be involved in redox reactions without losing their coordination ability, are of special interest. The introduction of such ligands into the metal coordination sphere will expand its reactivity. More- over, EPR spectroscopy gives essential information about the structure and behaviour of this type of compounds. However, diazabutadiene derivatives are quite rare in Ge IV chemistry. To date, only a few tetravalent germanium di- amides on the basis of substituted diazabutadienes have been described. [2a–2d] All of these compounds include non- chelating groups besides the diamide ligand. The existence of more than one diazabutadiene ligand in a germani- um(IV) environment was shown to be impossible. [1c] Never- theless, the use of benzannulated diamides yields the GeN 4 core. [2e–2f] In accordance with the preceding discussion, the chemistry of complexes based on the benzannulated 4,6-di- tert-butyl-N-(2,6-diisopropylphenyl)-o-iminoquinone ligand [a] G. A. Razuvaev Institute of Organometallic Chemistry of the Russian Academy of Sciences Tropinina Str. 49, 603950, Nizhny Novgorod, GSP-445, Russia Fax: +7-8314-627497 E-mail: pial@iomc.ras.ru Eur. J. Inorg. Chem. 2008, 1435–1444 © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1435 olato derivative, (AP)(APH)GeCl (3). Free imQ inserts into the Ge–H bond of (C 6 F 5 ) 3 GeH in thf to give (C 6 F 5 ) 3 Ge(APH) (4). It is another way of obtaining complexes with protonated ligands such as APH. Compound 3 can be easily oxidized by air to form the stable paramagnetic complex (AP)(ISQ)GeCl (5). Complexes 1 and 3–5 were structurally investigated by using single-crystal X-ray diffraction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) (imQ) (Scheme 1) is of interest. In comparison with diaza- butadienes, the substitution of one imino fragment by a car- bonyl function appreciably changes both the steric situation in the coordination sphere of the metal and the redox prop- erties of the active ligand. Scheme 1. Recently we have reported the synthesis of tin complexes with o-amidophenolato ligands on the basis of imQ con- taining one or two o-iminoquinone substituents and the metal in different valence states, [3] (Scheme 2) in contrast to the corresponding diamido complexes. [1b,1c,1e] Afterwards, the stable radical tin derivative based on this ligand has been obtained and structurally characterized. [4] It is noteworthy that the whole potential versatility of o- iminoquinone complexes, such as ability of the ligand to exist in the protonated state, was not manifested for tin de- rivatives. In the present paper we show the versatile behav- iour of imQ as the ligand that is able to exist in different redox and valent states by the example of germanium com- plexes.