Quasi-Isomeric Gallium Amides and Imides GaNR<sub>2</sub> and RGaNR (R = Organic Group):  Reactions of the Digallene, Ar‘GaGaAr‘ (Ar‘ = C<sub>6</sub>H<sub>3</sub>-2,6-(C<sub>6</sub>H<sub>3</sub>-2,6-Pr<sup>i</sup><sub>2</sub>)<sub>2</sub>) with Unsaturated Nitrogen Compounds

Reactions of the “digallene” Ar‘GaGaAr‘(<b>1</b>) (Ar‘ = C<sub>6</sub>H<sub>3</sub>-2,6-(C<sub>6</sub>H<sub>3</sub>-2,6-Pr<sup>i</sup><sub>2</sub>)<sub>2</sub>), which dissociates to green <b>:</b>GaAr‘ monomers in solution, with unsaturated N−N-bonded molecules are described. Treatment of solutions of <b>:</b>GaAr‘ with the bulky azide N<sub>3</sub>Ar<sup>#</sup> (Ar<sup>#</sup> = C<sub>6</sub>H<sub>3</sub>-2,6-(C<sub>6</sub>H<sub>2</sub>-2,6-Me<sub>2</sub>-4-Bu<sup>t</sup>)<sub>2</sub>), afforded the red imide Ar‘GaNAr<sup>#</sup> (<b>2</b>). Addition of the azobenzenes, ArylNNAryl (Aryl = C<sub>6</sub>H<sub>4</sub>-4-Me (<i>p</i>-tolyl), mesityl, and C<sub>6</sub>H<sub>3</sub>-2,6-Et<sub>2</sub>) yielded the 1,2-Ga<sub>2</sub>N<sub>2</sub> ring compound (<b>3</b>) or the products (<b>4</b>) and (<b>5</b>). Reaction of GaAr‘ with N<sub>2</sub>CPh<sub>2</sub> yielded the 1,3-Ga<sub>2</sub>N<sub>2</sub> ring compound Ar‘Ga(μ:η<sup>1</sup>-N<sub>2</sub>CPh<sub>2</sub>)<sub>2</sub>GaAr‘ (<b>6</b>), which is quasi-isomeric to <b>3</b>. Calculations on simple model isomers showed that the Ga(I) amide GaNR<sub>2</sub> (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(SiMe<sub>3</sub>)Ar‘ ‘ (<b>8</b>) (Ar‘ ‘ = C<sub>6</sub>H<sub>3</sub>-2,6-(C<sub>6</sub>H<sub>2</sub>-2,4,6-Me<sub>3</sub>)<sub>2</sub> from the reaction of LiN(SiMe<sub>3</sub>)Ar‘ ‘ (<b>7</b>) and “GaI”. Compound <b>8 </b>is also the first one-coordinate gallium species to be characterized in the solid state. The reaction of <b>8</b> with N<sub>3</sub>Ar‘ ‘ afforded the amido−imide derivative Ar‘ ‘NGaN(SiMe<sub>3</sub>)Ar‘ ‘ (<b>9</b>), 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 <b>2</b> and <b>8</b> as well as <b>3</b> and <b>6</b> are rare examples of quasi-isomeric heavier main group element compounds.