Phenylmercury chloride: Its single-crystal X-ray structure and some aspects of its biological chemistry

A single crystal of phenylmercury chloride (PhHgCl) was obtained by serendi pity from a solution of diphenylmercury (HgPh2) and dihydrolipoic acid in t etrahydrofuran / carbon tetrachloride. The crystal structure of PhHgCl is p seudotetragonal. It is best described in the orthorhombic space group Cmma with a = 6.856(1), b = 6.882(1), c = 14.309(2) Angstrom (at 193 K), and Z = 4. The Cl-Hg-C moiety of the PhHgCl molecule is exactly linear. The bond l engths at the Hg atom are Hg-Cl 2.345(2) and Hg-C 2.044(9) Angstrom. In the crystal, the molecules are arranged in double layers parallel to the a,b p lane. In a model medium for the gastric juice (0.1 M DCl in D2O / [D-8]dioxan, 37 degrees C), HgPh2 reacts to form PhHgCl. HgCl2, which would result from co mplete dearylation, cannot be isolated from the reaction mixture. However, it appears that a small equilibrium concentration of HgCl2 may be present, because on addition of 1,4,7-trithiacyclononane (ttcn) and diethyl ether, t he dichloride can be trapped as solid [Hg(ttcn)(2)][HgCl4]. We estimate tha t after oral uptake of HgPh2 20 - 90% are transformed into PhHgCl in the st omach after 30 min.