Triflate's bigger brother: The unprecedented tribrate anion, [Br3CSO3]

The synthesis of the unprecedented [Br3CSO3]− anion starts with the bromination of phenylmethanesulfonate, C6H5OSO2CH3, with KOBr leading to C6H5OSO2CBr3. The formation of the [CBr3] moiety has been proved, also by an X‐ray structure determination of the compound (triclinic, P‐1, a=685.9(2), b=698.1(2), c=1190.2(3) pm, α=93.99(1)°, β=97.42(1)°, γ=94.45(1)°). The ester C6H5OSO2CBr3 can be split under basic conditions. The resulting acid provides access to the yet unknown tribromomethanesulfates (“tribrates”). K[Br3CSO3] ⋅ H2O, the first tribrate known so far has been characterized comprehensively, including an X‐ray structure determination (monoclinic, C2/c, a=2267.1(2), b=1282.25(8), c=2618.2(2) pm, β=111.266(2)°), vibrational spectroscopy and theoretical calculations. Moreover, the thermal analysis shows that, after loss of the crystal water, the tribrate decomposes between 530 and 630 K. The tribromomethansulfonate anion (“tribrate”), [Br3CSO3]−, has been prepared for the first time. The anion is, up to now, the biggest brother of the well‐known triflate anion. Key step of the synthesis is the bromination of phenyl‐methanesulfonate by KOBr. The new anion could be investigated in the solid state for the example of K[Br3CSO3](H2O).