Mercury(II) and lead(II) complexes of 1-oxa-7-thia-4,10-diazacyclododecane ([12]aneN2OS)

The mixed donor 12-membered macrocyclic ligand 1-oxa-7-thia-4,10-diazacyclododecane ([12]aneN(2)OS) has been synthesized and the mercury(II) and lead(II) complexes, [Hg([12]aneN(2)OS) (NO3)(2)] and [Pb([12]aneN(2)OS) (NO3)(2)], have been isolated and characterized by X-ray crystallography. Crystals of the mercury complex are monoclinic, space group P 2(1)/c, a 9.576(2), b 10.757(2), c 14.789(4) Angstrom, beta 93.58(2)degrees, whilst crystals of the lead complex are monoclinic, space group P2(1)/n, a 19.490(7), b 8.010(2), c 19.576(6) Angstrom, beta 109.90(2)degrees. The protonation constants and stability constants have been determined potentiometrically in aqueous solution. The protonation constants for [12]aneN(2)OS (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.