The tris[(1-isopropylbenzimidazol-2-yl)dimethylsilyl]methyl magnesium hydride compound, [TismPriBenz]MgH, undergoes insertion of CS2 into the Mg-H bond at room temperature to give [TismPriBenz]Mg(κ2-S2CH), the first structurally characterized magnesium dithioformate compound. The dithioformate complex [TismPriBenz]Mg(κ2-S2CH) reacts with (i) CO2 at 80 °C to give, inter alia, the formate counterpart, [TismPriBenz]Mg(κ2-O2CH), and (ii) Me3SiX (X = Cl, Br), Me3SnX (X = F, Cl, Br) and MeI to afford the halide derivatives, [TismPriBenz]MgX.