The lithium polyfluorobenzenesulphinates, Li O2SR (R = C6F5, p-HC6F4, m-HC6F4, or o-HC6F4), and the dilithium tetrafluorobenzenedisulphinates, p- and o-(LiO2S)2C6F4, have been prepared by reaction of the appropriate polyfluoroaryllithium compounds with sulphur dioxide. All compounds were isolated as hydrates and gave the corresponding S-benzylthiouronium salts on treatment with S-benzylthiouronium chloride. From reactions of the lithium sulphinates with suitable mercuric salts in water, generally at room temperature, the derivatives RHgX (R = C6F5, X = Cl, Br, CH3CO2, or PhSO2; R = p-HC6F4, X = Cl, Br, or CH3CO2; R = m-HC6F4, X = Cl or Br; R = o-HC6F4, X = Cl), p-(XHg)2C6F4 (X = Cl, Br, or CH3CO2), and o-(XHg)2C6X4 (X = Cl or Br) have been prepared. Similarly, the bispolyfluorophenylmercurials R2Hg (R = C6F5, p-HC6F4, or m-HC6F4) have been prepared from the corresponding lithium sulphinates and either mercuric salts or polyfluorophenylmercuric halides in aqueous t-butanol. A possible mechanism for the sulphur dioxide elimination reactions is discussed.