Triflate's bigger brother: The unprecedented tribrate anion, [Br3 CSO3 ]

Abstract

The synthesis of the unprecedented [Br₃ CSO₃ ]^- anion starts with the bromination of phenylmethanesulfonate, C₆ H₅ OSO₂ CH₃ , with KOBr leading to C₆ H₅ OSO₂ CBr₃ . 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 C₆ H₅ OSO₂ CBr₃ can be split under basic conditions. The resulting acid provides access to the yet unknown tribromomethanesulfates ("tribrates"). K[Br₃ CSO₃ ] ⋅ H₂ O, 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.

Keywords: DFT calculations; Raman spectra; Thermal analysis; Tribromomethane sulfonates; tribrates.