Trimethylsulfonium


Trimethylsulfonium is an organic cation with the chemical formula 3S+. It is the simplest sulfonium cation.

Compounds

Several salts of trimethylsulfonium are known:
SaltMolecular formulaChemical formulaMolecular weight Properties
Trimethylsulfonium chloride3SClC3H9ClS112.5Colorless crystals, decompose at 100 °C, very soluble in ethanol, very hygroscopic.
Trimethylsulfonium bromide3SBrC3H9BrS157Colorless crystals from H2O. Decomposes at 172 °C, melts in a sealed tube at 201-201 °C, reacts in neutral aqueous solution.
Trimethylsulfonium iodide3SIC3H9IS204Colorless crystals from ethanol, decomposes at 203-207 °C. crystal structure monoclinic a=5.94 b=8.00 c=8.92 μm β=126°32′ 2 formulas per unit cell density=1.958
Trimethylsulfonium tetrafluoroborate3SBF4C3H9BF4S163.97mp 205-210°
Trimethylsulfonium methylsulfate3SSO4CH2C4H12O4S2188.27mp 92-94° Crystal structure orthorhombic a=12.6157 b=8.2419 μm c=7.540 cell volume 784.0 2 formulas per unit cell

Preparation

Sulfonium compounds can be synthesised by treating a suitable alkyl halide with a thioether. For example, the reaction of dimethyl sulfide with iodomethane yields trimethylsulfonium iodide:

Related

An extra oxygen atom can bond to the sulfur atom to yield the trimethylsulfoxonium ion.

Use

herbicide is often supplied as a trimethylsulfonium salt.
When mixed with aluminium bromide, or aluminium chloride or even hydrogen bromide, trimethylsulfonium bromide forms an ionic liquid, which melts at temperatures below standard conditions.