Mercury(II) penicillamine complex formation in alkaline aqueous solution.
The complex formation between mercury(II) and penicillamine (H(2)Pen = 3,3'-dimethyl cysteine) in alkaline aqueous solutions (pH approximately 2) has been investigated with extended X-ray absorption fine structure (EXAFS) and 199Hg NMR spectroscopy. By varying the penicillamine concentration (C(H(2)Pen) = 0.2-1.25 M) in approximately 0.1 M Hg(II) solutions, two coexisting major species [Hg(Pen)2](2-) and [Hg(Pen)3](4-) were characterized with mean Hg-S bond distances 2.34(2) and 2.44(2) A, respectively. The [Hg(Pen)2](2-) complex with two deprotonated penicillamine ligands forms an almost linear S-Hg-S entity with two weak chelating Hg-N interactions at the mean Hg-N distance 2.52(2) A. The same type of coordination is also found for the corresponding [Hg(Cys)2](2-) complex in alkaline aqueous solution with the mean bond distances Hg-S 2.34(2) A and Hg-N 2.56(2) A. The relative amounts of the [Hg(Pen)2](2-) and [Hg(Pen)3](4-) complexes were estimated by fitting linear combinations of the EXAFS oscillations to the experimental spectra. Also their (199)Hg NMR chemical shifts were used to evaluate the complex formation, showing that the [Hg(Pen)3](4-) complex dominates already at moderate excess of the free ligand ([Pen(2-)] > approximately 0.1 M).
Leung
Bonnie O
BO
Department of Chemistry, University of Calgary, Calgary, AB, CanadaT2N 1N4.
Jalilehvand
Farideh
F
Mah
Vicky
V
D000468:Alkalies / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008628:Mercury / Q000737:chemistry*; D008629:Mercury Isotopes; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010396:Penicillamine / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013057:Spectrum Analysis; D014867:Water / Q000737:chemistry; D014965:X-Rays
D000468:Alkalies; D008629:Mercury Isotopes; D009942:Organometallic Compounds; D012996:Solutions; D014867:Water; D008628:Mercury; D010396:Penicillamine