Activation of CO₂, CS₂, and COS by α-Diimine-Stabilized Gallylenes

Several gallylenes [L^PhGaM(THF)_n] stabilized by an α-diimine ligand (L^Ph=[(2,6-iPr₂C₆H₃)NC(Ph)]₂²⁻; M=Li, n=3, 3-Li; M=Na, n=4, 3-Na; M=K, n=1, 3-K) were prepared, which display diverse reactivities toward carbon dioxide and its sulfurized analogues. The reaction of 3 with CO₂ yielded a trimeric carbonate complex [{L^PhGa(CO₃)₂}₃{μ-K₉(THF)₆}] (4) and a dinuclear oxo-carbonate complex [K₂(THF)₆][L^PhGa(μ-CO₃)(μ-O)GaL^Ph] (5) in one pot through reductive disproportionation of CO₂. For CS₂, two ethenetetrathiolate gallium complexes, [M₂(Solv)₄][L^PhGa(μ-C₂S₄)GaL^Ph] (M=Na, Solv=THF, 6; M=K, Solv=DME, 7), were obtained via reductive coupling of CS₂. In the case of COS, disproportionation gave a disulfide-bridged complex [K₂(THF)₆] [L^PhGa(μ-S)₂GaL^Ph] (8) at room temperature, but a dithiocarbonate [Na₂(THF)₅][L^PhGa(S₂CO)]₂ (9) at low temperature, the latter being the first example of dithiocarbonates of p-block elements.