Disproportionation of Low Valent Indium Bromide: Synthesis and Molecular Structure of Bis (2, 6-Dimesityl-Phenyl) Indium Bromide, (2, 6-Mes2C6H3)2InBr (Mes = 2, 4, 6-Me3C6H2). When does Trigonal Planar Become T-Shaped?

Abstract

Bis(2, 6-dimesitylphenyl) indium bromide, (2, 6-Mes2C6H3)2 InBr (Mes = 2, 4, 6-Me3C6H2), I, has been prepared and characterized by 1H NMR, elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction. I may be approached by either of two synthetic routes. Whereas I may be readily prepared from reaction of indium (III) bromide with (2, 6-dimesitylphenyl) lithium in Et2O, it may also be approached by an interesting disproportionation of Br2In-InBr2 in the presence of (2, 6-Mes2C6H3) Li. The title compound crystallizes in the monoclinic space group P21/n (No. 14) with unit cell parameters a = 12.341 ((2)A, b = 20.799 (4) A, c = 16.512 (2) A, β = 101.18 (1)°, D calcd = 1.31 g cm −3, and V = 4158 (1)A3 for Z = 4. Refinement, based on 1661 observed reflections, converged at R = 0.072, Rw = 0.071. The In-Br bond distance is 2.505 (4) A. As the steric demands of the two bulky ligands are sufficient to result in a C-In-C bond angle of 157.3 (8)° — the widest angle reported for a three-coordinate indiu...