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

A series of tris(2-mercapto-1-tert-butylimidazolyl)hydroborato gallium compounds have been synthesized. While GaI₃ and GaCl₃ afford mononuclear {[TmBu^t]Ga} compounds, namely {[TmBu ^t]GaI}I, {[TmBu^t]GaCl}[GaCl₄], and [κ²-TmBu^t]₂GaI, the reactions of "GaI", Ga[GaCl₄] and (HGaCl₂)₂ yield compounds that feature Ga-Ga bonds, namely [TmBu^t]GaGaI₃, [TmBu^t]GaGaCl₃, {[TmBu^t]GaGa[TmBu ^t]}I₂, {[TmBu^t]GaGa[TmBu^t]} [GaCl₄]₂, {[TmBu^t]Ga(GaI₂) Ga[TmBu^t]}I and {[TmBu^t]GaGa[TmBu^t]}{[μ- κ¹,κ²-TmBu^t]GaI₂GaI ₂GaI}₂. These Ga-Ga bonded compounds may be formally regarded as donor-acceptor adducts between monovalent [TmBu^t]Ga and various trivalent moieties; for example, [TmBu^t]GaGaI₃ may be described as an adduct of [TmBu^t]Ga and GaI₃, while {[TmBu^t]Ga(GaI₂)Ga[TmBu^t]}⁺ is an adduct between two molecules of [TmBu^t]Ga and [GaI₂] ⁺. Comparison of the structure of [TmBu^t]Ga→B(C ₆F₅)₃ with that of [TmBu^t] In→B(C₆F₅)₃ indicates that [TmBu ^t]Ga is a more effective Lewis base than is [TmBu^t]In.