Alkali metal compounds of a gallium(I) carbene analogue {:Ga[N(Ar)C(Me)]2} (Ar = 2,6-iPr2C6H3)

A gallium dichloro complex (L−)GaIIICl2 (1) with an α-diimine ligand [(2,6-iPr2C6H3)NC(Me)]2 (L0 represents the neutral ligand, L− is the radical-anionic form of the ligand, and L represents its dianion L2−) 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 KC8, respectively, in THF gave the complexes [LGaINa(THF)3] (2), [LGaILi(THF)3] (3), [LGaI{μ2-K(THF)4}GaIL][K(THF)6] (4) and [LGaI(μ2-K){μ2-K(THF)2}GaIL] (5). In these complexes, the original radical-anionic ligand was further reduced to the dianion, whereas the GaIII ion was reduced to GaI 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.

Graphical abstractA series of alkali metal complexes of an NHCs-like gallium(I) species [:GaN2C2]− were synthesized by the reduction of (L−)GaIIICl2 (L = [(2,6-iPr2C6H3)NC(Me)]2) by Na, Li, K or KC8, respectively. The complexes feature Ga–M bonds (M = Li, Na, and K), which were also studied by DFT computations.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► An N-heterocyclic carbenes (NHCs)-like gallium(I) species is generated. ► The gallium(I) heterocycle coordinates to alkali metal ions. ► The complexes feature a Ga–M (M = Li, Na, K) bond. ► DFT computations confirm the dative Ga–M bond character.