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

Abstract

Several gallylenes [LPhGaM(THF)n] stabilized by an α-diimine ligand (LPh = [(2,6-iPr2C6H3)NC(Ph)]2; 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 [{LPhGa(CO3)2}3{μ-K9(THF)6}] (4) and a dinuclear oxo-carbonate complex {K2(THF)6}[LPhGa(μ-CO3)(μ-O)GaLPh] (5) in one pot through reductive disproportionation of CO2. For CS2, two ethenetetrathiolate gallium complexes, [M2(Solv)4][LPhGa(μ-C2S4)GaLPh] (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)5] [LPhGa(μ-S)2GaLPh] (8) at room temperature, but a dithiocarbonate [Na2(THF)6][LPhGa(S2CO)]2 (9) at low temperature, the latter being the first example of dithiocarbonates of p-block elements.

Keywords: carbon dioxide analogues; gallylene; low-valent main-group metals; small molecule activation; α-diimine.