Thiomersal

"Thiomersal (INN), and commonly known in the US as thimerosal, is  an organomercury compound. This compound is a well established antiseptic and antifungal agent."

"The pharmaceutical corporation Eli Lilly and Company gave thiomersal the trade name Merthiolate and it has been used as a preservative in vaccines,immunoglobulin preparations, skin test antigens, antivenins, ophthalmic and nasal products, and tattoo inks. Its use as a vaccine preservative iscontroversial, and it is being phased out from routine childhood vaccines in the United States, the European Union, and a few other countries."

"Thiomersal features mercury(II) with a coordination number 2, i.e. two ligands are attached to Hg, the thiolate and the ethyl group. The carboxylate group is not coordinated, but confers solubility in water. Like other two-coordinate Hg(II) compounds, the coordination geometry is linear, with a 180° S-Hg-C angle. Typically, organomercury thiolate compounds are prepared from organomercury chlorides."