Two Hg(II) complexes with a capped trigonal prismatic geometry derived from multidentate macrocyclic ligands containing N and S donors, with coordinated anions

Two Hg(II) complexes HgL′(ClO₄)₂] (1) and HgL(ClO₄)]ClO₄ (2) derived from the macrocyclic ligands, 4-(pyridin-2-ylmethyl)-1,7-dithia-4,10-diazacyclododecane (L′) and 7-(pyridin-2-ylmethyl)-1,4,10-trithia-7,13-diazacyclopentadecane (L), have been crystallographically characterised. Ligand L and its Hg(II) complex were isolated unexpectedly, and a possible formation pathway of the ligand is proposed. By including weakly bound O atoms from the perchlorate ions, the Hg atoms in both complexes are seven-coordinate and possess capped trigonal prismatic geometries. These uncommon structures for Hg(II) complexes were achieved mainly by the relatively large size of the metal ion and the steric effect from the macrocycles. In both complexes, strong hydrogen bonding between the amine hydrogen atom and a perchlorate ion was observed. For complex 1, the interaction is N(3)-H(15)···O(8) at 2.08(12) Å where O(8) is of the same anion as one of the coordinated O atoms; in complex 2, a similar hydrogen bond, N(7)-H(7)···O(32), with a distance of 2.25 Å, is formed to the coordinated anion, but the second anion remains discrete.