Synthesis and Characterization of Monomeric Organogallium−Nitrogen Compounds, Et₂GaNMe[C₆H₂(2,4,6-t-Bu)₃], Me₂GaNMe[C₆H₂(2,4,6-t-Bu)₃], MeGa{NH[C₆H₂(2,4,6-t-Bu)₃]}₂, and Ga{NH[C₆H₂(2,4,6-t-Bu)₃]}₃

Abstract

Four gallium−nitrogen compounds, Et2GaNMe[C6H2(2,4,6-t-Bu)3], Me2GaNMe[C6H2(2,4,6-t-Bu)3], MeGa{NH[C6H2(2,4,6-t-Bu)3]}2, and Ga[N(H)C6H2(t-2,4,6-Bu)3]3, have been prepared by metathetical reactions. The monomeric derivatives Et2GaNMe[C6H2(2,4,6-t-Bu)3] and Me2GaNMe[C6H2(2,4,6-t-Bu)3] are of interest because their 1H NMR spectra at room temperature had resonances indicative of two magnetically nonequivalent organic groups bonded to gallium, a spectral feature consistent with restricted rotation about the gallium−nitrogen bond. Variable-temperature 1H NMR spectral studies of a toluene solution of Me2GaNMe[C6H2(2,4,6-t-Bu)3] identified the barrier to rotation about the gallium−nitrogen bond as approximately 71 kJ/mol. This result suggests that steric effects might be responsible. The monomeric compound MeGa{NH[C6H2(2,4,6-t-Bu)3]}2 was prepared from MeGaCl2 and LiNH[C6H2(t-Bu)3] but was also the gallium−nitrogen product when Me2GaCl was reacted with the same lithium amide in diethyl ether. Experimental data demonstrated that Me2GaNH[C6H2(2,4,6-t-Bu)3] underwent a ligand redistribution reaction at room temperature to form an equilibrium mixture with MeGa{NH[C6H2(2,4,6-t-Bu)3]}2 and GaMe3. In contrast, the tertiary amide Ga{NH[C6H2(t-Bu)3]}3 does not readily undergo ligand redistribution reactions with GaMe3.