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Issue 41, 2007
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Mercury(ii) penicillamine complex formation in alkaline aqueous solution

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Abstract

The complex formation between mercury(II) and penicillamine (H2Pen = 3,3′-dimethyl cysteine) in alkaline aqueous solutions (pH ∼ 2) has been investigated with extended X-ray absorption fine structure (EXAFS) and 199Hg NMR spectroscopy. By varying the penicillamine concentration (CH2Pen = 0.2–1.25 M) in ∼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) Å, 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) Å. 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) Å and Hg–N 2.56(2) Å. 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 199Hg 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 ([Pen2−] > ∼ 0.1 M).

Graphical abstract: Mercury(ii) penicillamine complex formation in alkaline aqueous solution

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Submitted
30 Jul 2007
Accepted
11 Sep 2007
First published
21 Sep 2007

Dalton Trans., 2007, 4666-4674
Article type
Paper

Mercury(II) penicillamine complex formation in alkaline aqueous solution

B. O. Leung, F. Jalilehvand and V. Mah, Dalton Trans., 2007, 4666
DOI: 10.1039/B711436B

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