Mercury(II) and Lead(II) Complexes of 1-Oxa-7-thia-4,10-diazacyclododecane ([12]aneN2OS)

Abstract

The mixed donor 12-membered macrocyclic ligand 1-oxa-7-thia-4,10-diazacyclododecane ([12]aneN₂OS) has been synthesized and the mercury(II) and lead(II) complexes, [Hg([12]aneN₂OS)(NO₃)₂] and [Pb([12]aneN₂OS)(NO₃)₂], have been isolated and characterized by X-ray crystallography. Crystals of the mercury complex are monoclinic, space group P 2₁/c, a 9·576(2), b 10·757(2), c 14·789(4) Å, β 93·58(2)°, whilst crystals of the lead complex are monoclinic, space group P 2₁/n, a 19·490(7), b 8·010(2), c 19·576(6) Å, β 109·90(2)°. The protonation constants and stability constants have been determined potentiometrically in aqueous solution. The protonation constants for [12]aneN₂OS (log K_HL 9·13; log K _H2L 6·85) appear typical for secondary amines in similar trans-substituted 12-membered macrocycles. The magnitudes of the stability constants (Hg^II, log K_HgL 10·5; Pb^II, log K_PbL 6·6) are consistent with trends observed previously for macrocyclic ligands as secondary amine donors are replaced with oxygen and thioether donors.