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

Reaction of gallium chloride with (2,6-dimesitylphenyl)lithium, (Mes 2 C 6 H 3 )Li (Mes = 2,4,6-Me 3 C 6 H 2 ), gives bis[(dimesitylphenyl)gallium dichloride], [(Mes 2 C 6 H 3 )GaCl 2 ] 2, I . Treatment of I with {2-[(dimethylamino)methyl]phenyl}lithium, [2-(Me 2 NCH 2 )C 6 H 4 ]Li, affords (dimesitylphenyl)-2-((dimethylamino)methyl)phenylgallium chloride, (Mes 2 C 6 H 3 )[2-(Me 2 NCH 2 )C 6 H 4 ]GaCl, II . Reaction of (Mes 2 C 6 H 3 )Li with gallium bromide affords bis(dimesitylphenyl)gallium bromide, (Mes 2 C 6 H 3 ) 2 GaBr, III, while reaction of I with (Mes)Li yields (dimesitylphenyl)dimesitylgallium, (Mes 2 C 6 H 3 )(Mes) 2 Ga, IV . Gallium aryls I − IV have been characterized by elemental analyses, 1 H and 13 C NMR and IR spectroscopies, and single-crystal X-ray diffraction. I assumes a μ 2 -chloro-bridged dimeric structure, while the coordination of gallium in II is completed by one Mes 2 C 6 H 3 ligand and one chloride ligand and is intramolecularly stabilized by the nitrogen atom of [2-(Me 2 NCH 2 )C 6 H 4 ]. 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 GaC 3 plane approaching 90°.