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

The reactivity of two α-diimine-ligated digallanes, [L 2- Ga-GaL 2- ] (L a = [(2,6-iPr 2 C 6 H 3 )NC(CH 3 )] 2 , dpp-dad, 1 ; L b = 1,2-[(2,6-iPr 2 C 6 H 3 )NC] 2 C 10 H 6 , 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 (Me 3 SiN 3 ), 2-azido-benzonitrile (2-CNC 6 H 4 N 3 ), or tosylazide (TosN 3 ) results in imido-bridged complexes, [(L a ) · - Ga(μ-NSiMe 3 ) 2 Ga(L a ) · - ] ( 4 ) [(L b ) · - Ga(μ-NSiMe 3 ) 2 Ga(L b ) · - ] ( 5 ), [(L b ) · - Ga(μ-2-CNC 6 H 4 N) 2 Ga(L b ) · - ] ( 6 ), and [(L b ) · - Ga(μ-NTos) 2 Ga(L b ) · - ] ( 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(NAd)(N 3 Ad)Ga(L a ) · - ] ( 8 ) and [(L b ) · - Ga(NAd)(N 3 Ad)Ga(L b ) · - ] ( 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 ) 2- Ga(benzyl-N 4 -benzyl)] 2 ( 10 ) and amide complex {Na(THF) 4 }[(L a ) 2- Ga(NHSiMe 3 )(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 ).