The Molecular Structures of Lithium Trichlate, Li[Cl3CSO3]⋅2H2O, and Lithium Tribrate, Li[Br3CSO3]⋅2H2O

Lithium trichlate, Li[Cl3CSO3] ⋅ 2H2O (triclinic, P1‾ ${P\bar 1}$ , Z=2, a=630.29(3) pm, b=630.65(3) pm, c=1246.10(6) pm, α=100.657(2)°, β=97.813(2)°, γ=107.994(2)°) was obtained from the reaction of (H5O2)[Cl3CSO3] and LiOH in aqueous solution. Similarly, colourless single crystals of the tribrate Li[Br3CSO3] ⋅ 2H2O (triclinic, P1‾ ${P\bar 1}$ , Z=4, a=634.65(4) pm, b=636.83(4) pm, c=2496.8(2) pm, α=83.518°, β=86.081(5)°, γ=72.061(5)°) form in the reaction of aqueous Br3CSO3H and LiOH. The acid (H5O2)[Cl3CSO3] was obtained from the chlorination of CS2, followed by oxidation of the intermediate Cl3CSCl with H2O2. The bromo derivative Br3CSO3H has been prepared by bromination of phenylsulfonate with KOBr and subsequent ion exchange of the obtained potassium salt. Both lithium compounds exhibit molecular dimers according to {Li2(X3CSO3)2/1(H2O)2/1(H2O)2/2} with the Li+ ions in tetrahedral coordination of oxygen atoms. The difference in the crystal structures result from the variation of the orientation of the dimers with respect to each other. The experimental findings for the dimers are in good agreement with DFT calculations. The bigger siblings of the triflate anion, namely the trichlate [Cl3CSO3]− and the tribrate [Br3CSO3]− are synthesized as their lithium salts. The compounds display molecular structures with the anions, the lithium cations and water molecules arranged into dimers [Li2(X3CSO3)2(H2O)4] (X=Cl, Br). The figure shows both dimers, partly in an ORTEP style and partly as a Lewis formula.