SYNTHESIS AND MOLECULAR-STRUCTURE OF [2,4,6-T-BU3C6H2]2INBR - AN EXAMPLE OF A VERY STERICALLY HINDERED MOLECULE

The Grignard reagent MesMgBr (Mes* = 2,4,6-t-Bu3C6H2) was reacted wit h InCl3. The crystalline product, Mes2InBr, was isolated in nearly qu antitative yield. This compound crystallizes in the monoclinic space g roup P2(1)/c with unit cell parameters a = 10.421(2) angstrom b = 22.8 94(8) angstrom, c = 16.082(2) angstrom, beta = 107.51 (1)-degrees, V = 3659(2) angstrom3, and D(calcd) = 1.244 g cm-3 for Z = 4. Least squar es refinement based on 4280 observed reflections (I greater-than-or-eq ual-to 3sigma(I)) converged at R =6.0% (R(w) = 6.5%). The geometry aro und the indium center is trigonal bipyramidal with three short equator ial bonds and two long interactions to methyl groups on the ortho tert - butyl groups of one of the Mes moieties. Evidence supports an inter action between the two axial methyl groups and the indium atom, but th e nature of this interaction, i.e. agostic versus steric, cannot be un equivocally established by the available IR and NMR data.