Tris(2-mercapto-1-tert-butylimidazolyl)hydroborato gallium derivatives: synthesis of di- and trigallium compounds in a sulfur-rich coordination environment

Abstract

A series of tris(2-mercapto-1-tert-butylimidazolyl)hydroborato gallium compounds have been synthesized. While GaI₃ and GaCl₃ afford mononuclear {[Tm^But]Ga} compounds, namely {[Tm^But]GaI}I, {[Tm^But]GaCl}[GaCl₄], and [κ²-Tm^But]₂GaI, the reactions of “GaI”, Ga[GaCl₄] and (HGaCl₂)₂ yield compounds that feature Ga–Ga bonds, namely [Tm^But]GaGaI₃, [Tm^But]GaGaCl₃, {[Tm^But]GaGa[Tm^But]}I₂, {[Tm^But]GaGa[Tm^But]}[GaCl₄]₂, {[Tm^But]Ga(GaI₂)Ga[Tm^But]}I and {[Tm^But]GaGa[Tm^But]}{[μ-κ¹,κ²-Tm^But]GaI₂GaI₂GaI}₂. These Ga–Ga bonded compounds may be formally regarded as donor–acceptor adducts between monovalent [Tm^But]Ga and various trivalent moieties; for example, [Tm^But]GaGaI₃ may be described as an adduct of [Tm^But]Ga and GaI₃, while {[Tm^But]Ga(GaI₂)Ga[Tm^But]}⁺ is an adduct between two molecules of [Tm^But]Ga and [GaI₂]⁺. Comparison of the structure of [Tm^But]Ga→B(C₆F₅)₃ with that of [Tm^But]In→B(C₆F₅)₃ indicates that [Tm^But]Ga is a more effective Lewis base than is [Tm^But]In.