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-iPr2 C6 H3 )NC(CH3 )]2 , dpp-dad, 1 ; Lb = 1,2-[(2,6-iPr2 C6 H3 )NC]2 C10 H6 , 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 (Me3 SiN3 ), 2-azido-benzonitrile (2-CNC6 H4 N3 ), or tosylazide (TosN3 ) results in imido-bridged complexes, [(La )· - Ga(μ-NSiMe3 )2 Ga(La )· - ] ( 4 ) [(Lb )· - Ga(μ-NSiMe3 )2 Ga(Lb )· - ] ( 5 ), [(Lb )· - Ga(μ-2-CNC6 H4 N)2 Ga(Lb )· - ] ( 6 ), and [(Lb )· - Ga(μ-NTos)2 Ga(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)(N3 Ad)Ga(La )· - ] ( 8 ) and [(Lb )· - Ga(NAd)(N3 Ad)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 ).