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

The reactivity of two alpha-diimine-ligated digallanes, [L2-Ga-GaL2-] (L-a = [(2,6-iPr(2)C(6)H(3))NC(CH3)](2), dpp-dad, 1; L-b = 1,2-[(2,6-iPr(2)C(6)H(3))NC](2)C10H6, dpp-bian, 2), and a gallylene, [(L-a)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 (TosN(3)) results in imido-bridged complexes, [(L-a)Ga center dot-(mu-NSiMe3)(2)Ga(L-a)(center dot-)] (4) [(L-b)Ga center dot-(mu-NSiMe3)(2)Ga(L-b)(center dot-)] (5), [(L-b)Ga center dot-(mu-2-CNC6H4N)(2)Ga-(L-b)(center dot-)] (6), and [(L-b)Ga center dot-(mu-NTos)(2)Ga(L-b)(center dot-)] (7), with elimination of dinitrogen. Treatment of 1 or 2 with 1-adamantyl azide (1-AdN(3)), on the other hand, affords the unsymmetrical dinuclear complexes [(L-a)Ga center dot-(NAd)(N(3)Ad)Ga(L-a)(center dot-)] (8) and [(L-b)Ga center dot-(NAd)(N(3)Ad)Ga(L-b)(center dot-)] (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)[(L-a)Ga2-(benzyl-N-4-benzyl)](2) (10) and amide complex {Na(THF)(4)}[(L-a)Ga2-(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).