# Brominated Methanesulfonates: Characterization of K[Br3CSO3] ⋅ H2O, K2[Br2C(SO3)2] ⋅ H2O and K3[BrC(SO3)3] ⋅ H2O

## TL;DR

Scientists synthesized and characterized new brominated methanesulfonate compounds with varying numbers of SO3 groups and Br atoms.

## Contribution

The paper reports the synthesis and structural characterization of three novel brominated methanesulfonate potassium salts with unique crystal structures.

## Key findings

- The compounds K[Br3CSO3] ⋅ H2O, K2[Br2C(SO3)2] ⋅ H2O, and K3[BrC(SO3)3] ⋅ H2O were synthesized and structurally characterized.
- C—S bond lengths increase with more SO3 groups, and thermal stability increases by ≈50 °C per additional SO3 group.
- The synthesis of the dibromate and monobromate does not require phenyl ester starting materials, unlike the tribromate.

## Abstract

Bromination of phenyl methanesulfonate, C6H5OSO2CH3, with KOBr followed by hydrolytic cleavage of the phenyl ester leads to the tribromomethanesulfonate (“tribrate”) K[Br3CSO3] ⋅ H2O, which crystallizes in a hitherto unknown triclinic modification (P
1―, a = 662.87(4) pm, b = 1090.98(7) pm, c = 1273.98(8) pm, α = 106.079(2)°, β = 93.438(2)°, γ = 90.121(2)°). In contrast to the synthesis of the tribrate, in which an aromatic ring must be present at the SO3 group for a successful bromination, the synthesis of K2[Br2C(SO3)2] ⋅ H2O (monoclinic, P21/c, Z = 4, a = 717.17(3) pm, b = 710.78(3) pm, c = 2092.50(9) pm, β = 94.732(2)°) and K3[BrC(SO3)3] ⋅ H2O (tetragonal, P43, Z = 4, a = 713.6(1) pm, c = 2324.50(7) pm) using KOBr do not need the phenylesters as starting materials. Comparing the C—S bond lengths of the different anions with each other, a trend emerges in which the C—S bond length increases with increasing number of SO3 groups (decreasing number of Br atoms). Furthermore, an increase in thermal stability by ≈50 °C per additional SO3 group can be observed. The compounds are characterized by X‐ray diffraction, vibrational spectroscopy, and thermal analyses.

The sulfonates of methane can be easily brominated using hypobromite in aqueous solution. The structures of resulting anions [Br3CSO3]−, [Br2C(SO3)2]2−, and [BrC(SO3)3]3− can be analysed for the respective potassium salts.© 2026 WILEY‐VCH GmbH