Trimethylsulfonium (systematically named trimethylsulfanium and trimethylsulfur(1+)) is an organic cation with the chemical formula (CH3)3S+ (also written as C3H9S+). It is the simplest sulfonium cation. Trimethylsulfonium (systematically named trimethylsulfanium and trimethylsulfur(1+)) is an organic cation with the chemical formula (CH3)3S+ (also written as C3H9S+). It is the simplest sulfonium cation. Several salts of trimethylsulfonium are known: 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: An extra oxygen atom can bond to the sulfur atom to yield the trimethylsulfoxonium ion. Glyphosate 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.