Alkali metal compounds of a gallium(I) carbene analogue {:Ga[N(Ar)C(Me)]₂} (Ar = 2,6-ⁱPr₂C ₆H₃)

A gallium dichloro complex (L^-)Ga^IIICl₂ (1) with an α-diimine ligand [(2,6-ⁱPr₂C ₆H₃)NC(Me)]₂ (L⁰ represents the neutral ligand, L^- is the radical-anionic form of the ligand, and L represents its dianion L^2-) was used to synthesize a series of alkali metal complexes of an N-heterocyclic carbenes (NHCs)-like gallium(I) species. Reduction of the precursor 1 with three equivalents of Na, Li, K or KC ₈, respectively, in THF gave the complexes [LGa^INa(THF) ₃] (2), [LGa^ILi(THF)₃] (3), [LGa ^I{μ₂-K(THF)₄}Ga^IL][K(THF) ₆] (4) and [LGa^I(μ₂-K){μ₂- K(THF)₂}Ga^IL] (5). In these complexes, the original radical-anionic ligand was further reduced to the dianion, whereas the Ga ^III ion was reduced to Ga^I to yield the NHCs analogue [:GaN₂C₂]^-, which then coordinated to alkali metal ions to form the complexes 2-5. Single crystal X-ray diffraction analyses revealed that these complexes feature direct Ga-M bonds (M = Li, Na, and K), which have also been studied by DFT computations.