Reactions of an Anionic Gallylene with Azobenzene or Azide Compounds Through C(sp²)-H and C(sp³)-H Activation

The activation of inert C-H bonds remains a challenge in current chemistry. Here, we report the excellent reactivity of the anionic gallylene species [LGa:][Na(THF)₃] (L = [(2,6-iPr₂C₆H₃)NC(CH₃)]₂^2-, 1) that allows the selective activation one ortho sp² C-H bond of several azobenzene and azide derivatives at ambient temperature, with the transfer of the hydrogen atom to one of the nitrogen atoms. The process leads to the formation of the aryl amido products [LGa-κ²N,C-PhNN(H)(p-R-C₆H₃)][Na(solvent)₃] (2, R = H solvent = DME (1,2-Dimethoxyethane); 3, R = -OMe, solvent = DME; 4, R = -NMe₂ solvent = THF), [LGa-κ²N,C-(m-CH₃-C₆H₄)NN(H)(m-CH₃-C₆H₃)][Na(15-C-5)₂] (5) with new Ga-C and Ga-N bonds. Moreover, 1 is also effective for the C-H activation of two azides RN₃ (R = 2,4,6-Me₃C₆H₂ or 2,6-iPr₂C₆H₃), resulting in the formation of gallium amides [LGa(NH-2-(CH₂)-4,6-Me₂C₆H₂)][Na(15-C-5)₂] (6) and [LGa(NH-2,6-iPr₂C₆H₃)₂][Na(THF)₅] (7) through intra- or intermolecular sp³ C-H amination. Significantly, these reactions occur for the highly challenging activation of inert C(sp²)-H and C(sp³)-H bonds, thus demonstrating the excellent reactivity of the Ga(I) species 1. The products 2-7 were characterized by X-ray crystallography, ¹H and ¹³C NMR, UV-vis spectroscopy, and density functional theory (DFT) calculations.