Isolation and Crystal Structure of [(C₆H₆)₂Ga°GaCI₄]₂•3C₆H₆, a Bis(η⁶-benzene)galllum(I) Complex

Under carefully controlled conditions a discrete phase of the composition (C₆H₆)₃₅Ga₂Cl₄ can be crystallized from solutions of Ga2Cl₄ in anhydrous benzene. The complex was characterized by X-ray crystallography. It crystallizes in the triclinic space group C–PI with lattice constants (at -50 ± 5 °C) of a = 9.294 (2) Å,b = 10.691 (3) Å, c = 12.791 (3) Å, α = 85.57 (2)°, β = 103.15 (2)°, and γ = 106.26 (2)°. The fundamental unit, corresponding to Z = 2, contains (C₆H₆)₂Ga.GaCL₄.1.₅C₆H₆. The crystal structure can be described as consisting of cyclic centrosymmetrical [(C₆H₆)₂GaIIGaIIICl₄]₂ units and isolated benzene molecules. In the bis(benzene)galliumd) moieties the two η⁶-benzene rings form an interplane angle of 124.4°. Two distorted tetrachlorogallate tetrahedra provide single- or double-bridging chlorine atoms to the Ga(I) centers. The remaining benzene molecules are interstitial solvate components. 1 is the first structurally characterized benzene complex of an univalent group 3A metal. The Ga-C distances range from 3.015 to 3.154 Å (ring B) and from 3.186 to 3.291 Å (ring A). The Ga(I) atom is located 2.758 and 2.926 A above the ring planes B and A, respectively. The material is closely related to the benzene complexes of Sn(II) and Pb(II) described previously.