Quasi-Isomeric Gallium Amides and Imides GaNR2 and RGaNR (R = Organic Group):  Reactions of the Digallene, Ar‘GaGaAr‘ (Ar‘ = C6H3-2,6-(C6H3-2,6-Pri2)2) with Unsaturated Nitrogen Compounds

Reactions of the “digallene” Ar‘GaGaAr‘(1) (Ar‘ = C6H3-2,6-(C6H3-2,6-Pri2)2), which dissociates to green :GaAr‘ monomers in solution, with unsaturated N−N-bonded molecules are described. Treatment of solutions of :GaAr‘ with the bulky azide N3Ar# (Ar# = C6H3-2,6-(C6H2-2,6-Me2-4-But)2), afforded the red imide Ar‘GaNAr# (2). Addition of the azobenzenes, ArylNNAryl (Aryl = C6H4-4-Me (p-tolyl), mesityl, and C6H3-2,6-Et2) yielded the 1,2-Ga2N2 ring compound (3) or the products (4) and (5). Reaction of GaAr‘ with N2CPh2 yielded the 1,3-Ga2N2 ring compound Ar‘Ga(μ:η1-N2CPh2)2GaAr‘ (6), which is quasi-isomeric to 3. Calculations on simple model isomers showed that the Ga(I) amide GaNR2 (R = Me) is much more stable than the isomeric Ga(III) imide RGaNR. This led to the synthesis of the first stable monomeric Ga(I) amide, GaN(SiMe3)Ar‘ ‘ (8) (Ar‘ ‘ = C6H3-2,6-(C6H2-2,4,6-Me3)2 from the reaction of LiN(SiMe3)Ar‘ ‘ (7) and “GaI”. Compound 8 is also the first one-coordinate gallium species to be characterized in the solid state. The reaction of 8 with N3Ar‘ ‘ afforded the amido−imide derivative Ar‘ ‘NGaN(SiMe3)Ar‘ ‘ (9), a gallium nitrogen analogue of an allyl anion. All compounds were spectroscopically and structurally characterized. In addition, DFT calculations were performed on model compounds of the amide, imide, and cyclic 1,2- and 1,3-species to better understand their bonding. The pairs of compounds 2 and 8 as well as 3 and 6 are rare examples of quasi-isomeric heavier main group element compounds.