Indium(III) Catecholates Based on Alkyl-Substituted o-Benzoquinones

Abstract

A series of dimeric indium(III) catecholates [(R-Cat)InI]₂ (R = 3,6-cHex (I), 3,5-tOc (II), 4-tOc (III), and 3,5-C(Me)₂Ph (IV)) is synthesized by the oxidative addition of indium(I) iodide to the following alkyl-substituted o-benzoquinones: 3,6-di-cyclo-hexyl-o-benzoquinone (3,6-cHex-Q), 3,5-di-tert-octyl-o-benzoquinone (3,5-tOc-Q), 4-tert-octyl-о-benzoquinone (4-tOc-Q), and 3,5-bis(2-phenylpropan-2-yl)-o-benzoquinone (3,5-C(Me)₂Ph-Q). Compounds I–IV are stable in the crystalline state and in solution, and their structures are confirmed by NMR and IR spectroscopy and elemental analysis. The crystallization of complex II from THF gives crystals of two types, cis-II·4THF and trans-II·4THF, corresponding to the cis and trans orientations of the alkyl substituents relatively to the catecholate fragment plane. The reactions of compounds I–IV with 2,2'-bipyridyl afford heteroleptic derivatives (R-Cat)InI(Bipy) (R = 3,6-cHex (V), 3,5-tOc (VI), 4-tOc (VII), and 3,5-C(Me)₂Ph (VIII)). Compounds V and VIII are isolated in the individual state and characterized by a set of physicochemical methods. Derivatives VI and VII are unstable and undergo further transformations to form a poorly separable mixture of products. The molecular structures of complexes cis-II·4THF and trans-II·4THF are determined by X-ray diffraction (XRD) (CIF files CCDC nos. 2404879 and 2404880, respectively).