Reactions of Low-Valent Gallium Species with Organic Azides: Formation of Imido‑, Azoimido‑, and Tetrazene Complexes

The reactivity of two α-diimine-ligated digallanes,
[L2–Ga–GaL2–] (La =
[(2,6-iPr2C6H3)NC(CH3)]2, dpp-dad, 1; Lb = 1,2-[(2,6-iPr2C6H3)NC]2C10H6, dpp-bian, 2), and a gallylene, [(La)2–GaNa(THF)3] (3), toward
organic azides was studied. Reaction of digallane 1 or 2 with trimethylsilyl azide (Me3SiN3), 2-azido-benzonitrile (2-CNC6H4N3), or tosylazide (TosN3) results in imido-bridged complexes,
[(La)·–Ga(μ-NSiMe3)2Ga(La)·–] (4) [(Lb)·–Ga(μ-NSiMe3)2Ga(Lb)·–] (5), [(Lb)·–Ga(μ-2-CNC6H4N)2Ga(Lb)·–] (6), and [(Lb)·–Ga(μ-NTos)2Ga(Lb)·–] (7), with elimination of dinitrogen.
Treatment of 1 or 2 with 1-adamantyl azide
(1-AdN3), on the other hand, affords the unsymmetrical
dinuclear complexes [(La)·–Ga(NAd)(N3Ad)Ga(La)·–] (8) and [(Lb)·–Ga(NAd)(N3Ad)Ga(Lb)·–] (9), which contain both imido and triazene bridges.
Different from the Ga(II) complexes 1 and 2, the reactions of Ga(I) species 3 with benzylazide
or trimethylsilyl azide result in the tetrazene complex {Na(THF)}2[(La)2–Ga(benzyl-N4-benzyl)]2 (10) and amide complex {Na(THF)4}[(La)2–Ga(NHSiMe3)(benzyl)] (11). It is likely that these latter transformations
proceed via the transient formation of the corresponding GaN
imide complex, which undergoes either cycloaddition with a second
azide (to form 10) or activation of the C–H bond
of methyl in one solvent toluene molecule (to yield 11).