Synthesis and Structure of Polynuclear Indoxanes and Thalloxanes Containing Bulky <i>m</i>-Terphenyl Substituents

Depending on the reaction conditions, the base hydrolysis of (2,6-Mes2C6H3In)2(μ-Cl)2Cl2 (1) in a two-layer system of aqueous NaOH/diethyl ether or toluene afforded 2,6-Mes2C6H3InCl2·H2O (2), (2,6-Mes2C6H3In)2(μ-OH)2Cl2 (3), (2,6-Mes2C6H3In)3(μ-OH)4Cl2 (4), and (2,6-Mes2C6H3In)4(μ-OH)8 (5), respectively, in high yields. The indoxane 5 can be regarded as a heavier and aggregated congener of arylboronic acids. An attempt at preparing (2,6-Mes2C6H3Tl)2(μ-Cl)2Cl2 (6) by the chlorination of 2,6-Mes2C6H3Tl (prepared in situ from 2,6-Mes2C6H3Li and TlCl) using SO2Cl2 provided the isomeric diarylthallium cation [(2,6-Mes2C6H3)2Tl]TlCl4 (7). The exposure of crude reaction mixture consisting of 2,6-Mes2C6H3Tl and LiCl to moist air surprisingly produced (2,6-Mes2C6H3Tl)2(μ-OH)2Cl2 (8), which reacted with hydrochloric acid to give 6. Base hydrolysis of 8 in a two-layer system of aqueous NaOH/CHCl3 proceeded with partial cleavage of the m-terphenyl substituents and yielded the thalloxane cluster (2,6-Mes2C6H3Tl)4Tl2(μ3-O)4(μ-OH)6 (9) in moderate yield. Compounds 1−9 were characterized by X-ray crystallography.