Formation and structures of mercury complexes of 18-membered unsaturated and saturated thiacrown ethers

The complexation of 18-membered unsaturated thiacrown ether, 18-UT-6, with 1 equiv of HgCl(2) in acetone afforded mercury complex Hg(II)(18-UT-6)Cl(2). The complexations of 18-membered saturated thiacrown ether, 18S6, with 1 equiv each of HgCl(2) and CdCl(2) in acetone afforded Hg(II)(18S6)Cl(2) and Cd(II)(18S6)Cl(2), respectively. The crystal structure of Hg(II)(18-UT-6)Cl(2) revealed that the mercury atom was inside the cavity of the macrocycle and the geometry around the mercury atom was an eight-coordinate hexagonal bipyramidal arrangement. ORTEP drawing of Hg(II)(18S6)Cl(2) revealed the existence of the mercury atom outside the cavity of the ring, as well as a polymeric chain structure. (1)H NMR study of Hg(II)(18-UT-6)Cl(2) in acetone-d(6) indicated that the interconversion between free 18-UT-6 and pure complex was slower than the NMR time scale. The titration experiment by (1)H NMR revealed that 18-UT-6 had inclusion selectivity for the number of mercury atoms. The electrochemical behavior of complexes Hg(II)(18-UT-6)Cl(2) and Hg(II)(18S6)Cl(2) was also examined.