Synthesis and crystal structure of a mixed bis(arene)gallium(I) complex: Dimeric (η⁶-1,2,4,5-tetramethylbenzene) (η⁶-toluene)gallium(I) tetrachlorogallate(III)

The title compound (η⁶-1,2,4,5-tetramethylbenzene)(η⁶-toluene)gallium(I) tetrachlorogallate(III) (1) crystallizes from dilute solutions of equimolar quantities of gallium(I) tetrachlorogallate(III) and 1,2,4,5-tetramethylbenzene (durene) in toluene on slow cooling to 0°C. More concentrated solutions yield the 1 : 1 complex (1,2,4,5-C₆H₂Me₄)Ga⁺Ga Cl₄^- (2). The crystals of compound 1 contain centrosymmetrical dimers, {[(η⁶-C₆H₂Me₄)(η⁶-C₆H₅Me)Ga]GaCl₄}₂, in which each gallium(I) centre is hexahapto-bonded to one durene and one toluene molecule. The two aromatic hydrocarbons of these bent-sandwich moieties form an interplane angle of 58°. With a metal-to-ring distance of 2.642 Å, the durene ring is much closer to the Ga⁺ atom than the toluene ring (3.039 Å). The Ga⁺ atoms are bridged via two slightly distorted GaCl₄^- tetrahedra through contacts with three of the four chlorine atoms. The structure resembles that of the [(C₆H₆)₂Ga]GaX₄ complexes with X = Cl, Br.