Diterphenylgallium Alkyls and Hydride:  Synthesis, Characterization, and Reactivity

The reactions of (2,6-Mes₂C₆H₃)₂GaCl (2) with LiMe, Li-t-Bu, and LiHBEt₃ afforded the bis(terphenyl)gallium compounds (2,6-Mes₂C₆H₃)₂GaMe (3), (2,6-Mes₂C₆H₃)₂Ga-t-Bu (4) and (2,6-Mes₂C₆H₃)₂GaH (5). Hydrolysis of 2 and 3 gave the dimeric, hydroxide-bridged species [2,6-Mes₂C₆H₃Ga(Cl)(μ-OH)]₂ (6) and [2,6-Mes₂C₆H₃Ga(Me)(μ-OH)]₂ (7) via loss of the terphenyl substituent as 1,3-Mes₂C₆H₄. Hydrolysis of 5 led to the loss of H₂ and the formation of the monomeric (2,6-Mes₂C₆H₃)₂GaOH (8). The compounds were characterized by FTIR and ¹H and ¹³C{¹H} NMR spectroscopy and X-ray crystallography. The structural studies of the diterphenyl compounds 2−5 and 8 showed the highly flexible nature of these compounds, as expressed in the wide range of the C_Terph−Ga−C_Terph angles from 113.23° in 4 to 153.5° in 2. Methyl and hydride abstraction from 3 and 5 with the Lewis acids [Ph₃C]⁺[B(C₆F₅)₄]^- and B(C₆F₅)₃ afforded the ionic species [(2,6-Mes₂C₆H₃)₂Ga]⁺[B(C₆F₅)₄]^-, [(2,6-Mes₂C₆H₃)₂Ga]⁺[MeB(C₆F₅)₃]^-, and [(2,6-Mes₂C₆H₃)₂Ga]⁺[HB(C₆F₅)₃]^-, all of which contain the linear two-coordinate cation [(2,6-Mes₂C₆H₃)₂Ga]⁺ (1⁺).