Reactivity studies of trimethylaluminum, trimethylgallium, and trimethylindium with a series of five silylamines: molecular structure of trans-[Me2InN(Me)SiMe3](2)

Equimolar mixtures of Me3M (M = Al, Ga, In) with five silylamines, N(SiMe3) (3), HN(SiMe3)(2), MeN(SiMe3)(2), Me2NSiMe3, and HN(Me)SiMe3, were prepared in benzene-d(6) and toluene-d(8) solutions and variable temperature H-1- a nd C-13-NMR spectroscopy was utilized to deduce the capacity of these syste ms to form stable complexes under varying degrees of amine silylation. Appr oximate values for the cone angles of the bound amines are extrapolated fro m NMR data and from literature trends. The 1,2-elimination reactions of MMe 3 with HN(Me)SiMe3 at 90 degrees C (120 degrees C for the Ga analogue) affo rd mixtures in solution of cis- and trans-[Me2MN(Me)SiMe3](2) which crystal lizes in the trans form. In solution, the dimers equilibrate to mixtures of cis and trans geometrical isomers. The trans isomer is the predominant iso mer for all three analogues. The equilibration process follows reversible f irst-order kinetics for each dimer. The thermodynamic and kinetic parameter s for the trans to cis equilibration have been determined and are discussed in terms of an intramolecular ring opening mechanism. The molecular struct ure of trans-[Me2InN(Me)SiMe3](2) has been determined by a single crystal X -ray diffraction study. The molecule is dimeric and lies on a crystallograp hic center of symmetry. (C) 1999 Elsevier Science S.A. All rights reserved.