A Homoleptic Ga4 Radical Anion: Isolation, Characterization, and Reactivity.

We report the synthesis and characterization of a homoleptic Ga4 radical anion ([Li+]•[1•-]), prepared via a salt-metathesis reaction between Cp*Ga (Cp* = pentamethylcyclopentadienyl) and [Li2(L)] (L = Me2Si(DipN)2). Combined structural and computational analyses reveal a nearly planar geometry at the central gallium atom, with only minimal distortion toward a trigonal pyramidal geometry, and the unpaired spin density localized in its 4p orbital. Density functional theory (DFT) calculations elucidate the reaction mechanism for the formation of [Li+]•[1•-], while N-heterocyclic carbene (NHC)-trapping experiments led to the isolation of NHC-stabilized digallyl digallenes (2a and 2b) as well as a digallyl-substituted gallium radical (3c). Compound [Li+]•[1•-] exhibits versatile gallium-centered radical reactivity, including one-electron oxidation with S8 and facile E─E bond activation (E = S, Se, and I) toward PhS-SPh, PhSe-SePh, and I2.