Trimethylsulfonium (systematically named trimethylsulfanium) is an organic cation with the chemical formula (also written as ).
Compounds
Several salts of trimethylsulfonium are known. X-ray crystallography reveals that the ion has trigonal pyramidal molecular geometry at sulfur atom, with C-S-C angles near 102° and C-S bond distance of 177 picometers. Unless the counteranion is colored, all trimethylsulfonium salts are white or colorless.
SaltFormulaMolecular weight (g/mol)PropertiesHeilbron's Dictionary of Organic Compounds, volume 4, revised edition published in 1953. Published in Great BritainTrimethylsulfonium chloride112.5Colorless crystals, decompose at 100 °C, very soluble in ethanol, very hygroscopic.Trimethylsulfonium bromide157Colorless crystals. Decomposes at 172 °C, melts in a sealed tube at 201-201 °C, reacts in neutral aqueous solution.Trimethylsulfonium iodide204Colorless crystals, decomposes at 203-207 °C. crystal structure monoclinic, with these parameters: a = 5.94 μm, b = 8.00 μm, c = 8.92 μm, β = 126°32′ 2 formulas per unit cell, density = 1.958 g/cm3 Trimethylsulfonium tetrafluoroborate 163.97 white crystalline solidhttps://cymitquimica.com/cas/676-88-0/, melting point = 205-210 °C Trimethylsulfonium methylsulfate 188.27 White solidhttps://www.sigmaaldrich.com/GB/en/sds/aldrich/303593?userType=anonymous, melting point = 92-94 °C Crystal structure orthorhombic with these parameters: a = 12.6157 μm, b = 8.2419 μm, c = 7.540 μm 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 , where the sulfur atom is tetravalent and tetracoordinated.
Use Glyphosate herbicide is often supplied as a trimethylsulfonium salt, referred to as trimesium.
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.
References
See also Onium compounds