Die Komplexchemie des Methylquecksilber‐Kations

The stability constants of the methylmercury complexes CH3HgL1−λ with a considerable number of ligands Lλ− have been determined (Table 1). Like H+, the cation CH3Hg+ reveals the coordination number 1 almost exclusively. Some ligands form also binuclear adducts (CH3Hg)2L2−λ and sulfide even forms (CH3Hg)3S+. The coordination behaviours of CH3Hg+ and H+ however are very different concerning the selection of ligands, the former being a soft and the latter a hard acid in the sense of PEARSON. The entropy ΔS of the reaction: H+ + L− HL is more positive by about 14 c.u. than ΔS of the reaction: CH3HG+ + L− CH3HgL. The hydrogen ion in aqueous solution has a far greater order producing action on the solvent than CH3Hg+. Two dyes also have investigated, which may serve as indicators for CH3HG+ and for the determination of pCH3Hg (= −log[CH3Hg+]).