Evidence for dissolved polymeric mercury(II)-sulfur complexes?

We have examined alkaline sulfidic (0.5–0.003 M Na2S), aqueous solutions of Hg(II)-S complexes (4–370 ppm Hg(II)) by Hg LIII edge EXAFS spectroscopy at 296, 348 and 423 K. Data were collected using the ID26 High Brilliance X-ray Spectroscopy beamline at the ESRF. Analysis of these EXAFS spectra shows Hg coordinated by two S atoms at 2.30 Å; multiple scattering analyses reveal a linear [–S–Hg–S–] arrangement in the solution complex. These results are in agreement with earlier results on more concentrated solutions of these complexes. There is also evidence in the data for polynuclear sulfide complexes at 296 K and 348 K for samples with the lowest sulfide concentrations although this is complicated by multiple scattering effects.