Syntheses, Structure, and Reactivity of 2,6-Dimesitylphenyl-Based Sterically Demanding Gallium Aryls

Abstract

Reaction of gallium chloride with (2,6-dimesitylphenyl)lithium, (Mes2C6H3)Li (Mes = 2,4,6-Me3C6H2), gives bis[(dimesitylphenyl)gallium dichloride], [(Mes2C6H3)GaCl2]2, I. Treatment of I with {2-[(dimethylamino)methyl]phenyl}lithium, [2-(Me2NCH2)C6H4]Li, affords (dimesitylphenyl)-2-((dimethylamino)methyl)phenylgallium chloride, (Mes2C6H3)[2-(Me2NCH2)C6H4]GaCl, II. Reaction of (Mes2C6H3)Li with gallium bromide affords bis(dimesitylphenyl)gallium bromide, (Mes2C6H3)2GaBr, III, while reaction of I with (Mes)Li yields (dimesitylphenyl)dimesitylgallium, (Mes2C6H3)(Mes)2Ga, IV. Gallium aryls I−IV have been characterized by elemental analyses, 1H and 13C NMR and IR spectroscopies, and single-crystal X-ray diffraction. I assumes a μ2-chloro-bridged dimeric structure, while the coordination of gallium in II is completed by one Mes2C6H3 ligand and one chloride ligand and is intramolecularly stabilized by the nitrogen atom of [2-(Me2NCH2)C6H4]. III assumes a rare T-shaped coordination about the gallium center (C−Ga−C 153.5(2)°), while IV represents, arguably, the most sterically crowded trigonal planar gallium aryl reported with the aromatic rings about the GaC3 plane approaching 90°.