Homoleptic Group 12 metal complexes of macrocyclic thioethers: the crystal structures of bis(1,4,7-trithiacyclodecane)M(II) perchlorate: M(II)=zinc(II), cadmium(II), mercury(II)

We wish to report the crystal structures for a series of homoleptic complexes involving the three Group 12 family members with the crown thioether 1,4,7-trithiacyclodecane (10S3). The ligand coordinates in tridentate fashion and readily forms bis complexes with the d10 metal ions, Zn(II), Cd(II), and Hg(II). The three compounds have the general formula [M(10S3)2](ClO4)2 and are isostructural. The three crystal structures show the two 10S3 ligands arranged in a trans or anti fashion around the metal center in a distorted octahedral fashion to yield the meso stereoisomer. All three complexes show hexakis(thioether) octahedral coordination which is unusual for these Group 12 metal ions. The mean M–S bond distances increase as one moves down the family although there is only a modest increase between the Cd and Hg complexes (Zn: 2.4965(10) Å, Cd: 2.6523(6) Å, Hg: 2.6870(16) Å). In sharp contrast to crown thioether complexes of other metal ions, the majority of the M–S bond lengths in these 10S3 complexes are shorter than those found in their 9S3 analogs. A simple four line 13C{1H} NMR spectrum is obtained for the three complexes. Variable temperature 13C{1H} NMR experiments performed on the Hg(II) complex suggest a rapid intermolecular exchange of the 10S3 ligands is occurring. The Cd complex shows a singlet in its 113Cd{1H} NMR spectrum with a chemical shift at 612 ppm, in agreement with a hexakis(thioether) coordination environment.