Mercury, carboxylate ligands

The biochemical basis for the toxicity of mercury and mercury compounds results from its ability to form covalent bonds readily with sulfur. Prior to reaction with sulfur, however, the mercury must be metabolized to the divalent cation. When the sulfur is in the form of a sulfhydryl (— SH) group, divalent mercury replaces the hydrogen atom to form mercaptides, X—Hg— SR and Hg(SR)2, where X is an electronegative radical and R is protein (36). Sulfhydryl compounds are called mercaptans because of their ability to capture mercury. Even in low concentrations divalent mercury is capable of inactivating sulfhydryl enzymes and thus causes interference with cellular metaboHsm and function (31—34). Mercury also combines with other ligands of physiological importance such as phosphoryl, carboxyl, amide, and amine groups. It is unclear whether these latter interactions contribute to its toxicity (31,36). 

Zinc and cadmium complexes of the novel tripod ligand (145) have also been described.1087 The reaction of Hg(HL)2 (HL = 2-mercaptobenzoic acid, 146) with cadmium nitrate leads to the novel CdHgL species, in which the cadmium is bonded to the carboxylate oxygen atom, and the mercury to the thiolate sulfur.1088... 

Complexes with carboxylates and related ligands Complexes with inorganic oxo anions Basic salts of mercury (II)... 

These generalized approaches have been applied specifically to the NMR spectra of EDTA, DTPA, MIDA, and NTA and the metal chelates formed by these ligands. Included are the chelates of the ions of the alkali metals, the alkaline earths, zinc, mercury, lead, molybdenum, zirconium, and some of the platinum metals. For the four chelating agents studied the nitrogen atoms within the ligands are definitely protonated before the carboxylate... 

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