m-Terphenylaluminum and -gallium compounds:: Synthesis and conversion into low-coordinate organogallium cations

The reaction of two or 3 equiv. of m-terphenyllithium with MCl3 or AlH3 center dot NMe3 (M = Al, Ga) affords the bis(terphenyl)-aluminum and -gallium chloride compounds [{2,6-(4-tBuC(6)H(4))(2)C6H3}2GaCl] (1), [{2,6-(3,5-Me2C6H3)(2)C6H3}(2)GaCl] (2), [{2,6-(4-tBuC(6)H(4)}(2)C6H3)(3)Ga] (3), [(2,6-Mes(2)C(6)H(3))(2)AlCl] (5), and [(2,6-Mes(2)C(6)H(3))(2)AlH] (7; Mes = 2,4,6-Me3C6H2). While the gallium compounds can be obtained at room temperature, heating is required for the aluminum derivatives. The dibutyl compounds [(2,6-Mes(2)C(6)H(3))GaBu2] (8) and [(2,6-Dipp(2)C(6)H(3))GaBu2] (9; Dipp = 2,6-iPr(2)C(6)H(3)) have also been synthesized by the reaction of m-terphenyllithium with ClGaBu2. A metathesis reaction of 2 with Li[Al{OCH(CF3)(2)}4] gives the ionic species [(2,6-Mes(2)C(6)H(3))(2)Ga](+)[Li{Al-[OCH(CF3)(2)](4)}(2)](-) (11). The cationic butyl(terphenyl)gallium compounds [(2,6-Mes(2)C(6)H(3))GaBu](+) ([13](+)) and [(2,6-Dipp(2)C(6)H(3))GaBu](+) ([14](+)) have been prepared by butanide abstraction with the trityl salts of the weakly coordinating anions [B(C6F5)(4)1(-), [CHB11Br6Me5](-), and [CHB11Cl11](-). These ionic species are stable at room temperature for days or weeks, although their combinations with the borate anion [B(C6F5)(4)](-) suffer from C6F5 migration, which is slow at room temperature and faster at elevated temperatures. The compound [14](+)[CHB11Cl11](-) is stable at 70 degrees C for at least 23 h. Addition of 1-octene to a solution of [14](+)[CHB11Cl11](-) in C6D6 results in olefin exchange and formation of the octyl species [(2,6-Dipp(2)C(6)H(3))Ga(octyl)](+) ([17](+)), and a slow alkylation of the solvent to afford various octylbenzenes. Hydrolysis of 8 and [13](+)[CHB11Br6Me5](-) gives the compounds [{(2,6-Mes(2)C(6)H(3))GaBu(mu-OH)}(2)] (10) and [(BuGa)(4)(mu-OH)(6)](2+)[CHB11Br6Me5](-)(2) (16). All compounds have been characterized by H-1 and C-13{H-1} NMR spectroscopy and mass spectrometry, and compounds 3, 5, 7, 10, and 16.4.5C(6)H(6) have also been characterized by single-crystal Xray crystallography. (C) Wiley-VCH Verlag GmbH & Co. KGaA.