Redetermination of (d-penicillaminato)lead(II)

Adam C Schell; Masood Parvez; Farideh Jalilehvand

doi:10.1107/S1600536812011877

. 2012 Mar 28;68(Pt 4):m489–m490. doi: 10.1107/S1600536812011877

Redetermination of (d-penicillaminato)lead(II)

Adam C Schell ^a, Masood Parvez ^a, Farideh Jalilehvand ^a,^*

PMCID: PMC3343873 PMID: 22589847

Abstract

In the title coordination polymer, [Pb(C₅H₉NO₂S)]_n {systematic name: catena-poly[(μ-2-amino-3-methyl-3-sulfidobutanoato)lead(II)]}, the d-penicillaminate ligand coordinates to the metal ion in an N,S,O-tridentate mode. The S atom acts as a bridge to two neighbouring Pb^II ions, thereby forming a double thiolate chain. Moreover, the coordinating carboxylate O atom forms bridges to the Pb^II ions in the adjacent chain. The overall coordination sphere of the Pb^II ion can be described as a highly distorted pentagonal bipyramid with a void in the equatorial plane between the long Pb—S bonds probably occupied by the stereochemically active inert electron pair. The amino H atoms form N—H⋯S and N—H⋯O hydrogen bonds, resulting in a cluster of four complex units, giving rise to an R ₄ ⁴(16) ring lying in the ab plane. The crystal structure of the title compound has been reported previously [Freeman et al. (1974 ▶). Chem. Soc. Chem. Commun. pp. 366–367] but the atomic coordinates have not been deposited in the Cambridge Structural Database (refcode DPENPB). Additional details of the hydrogen bonding are presented here.

Related literature

For an earlier characterization of the title compound, see: Freeman et al. (1974 ▶). For neurotoxic effects of Pb, see: Needleman (2004 ▶); Bressler et al. (1999 ▶); Godwin (2001 ▶). For treatments of lead(II) poisoning, see: Sinicropi et al. (2010) ▶; Casas & Sordo (2006 ▶). For graph-set notation, see: Bernstein et al. (1994 ▶).

Experimental

Crystal data

[Pb(C₅H₉NO₂S)]
M _r = 354.38
Monoclinic,
a = 6.251 (4) Å
b = 6.179 (3) Å
c = 10.259 (6) Å
β = 107.72 (2)°
V = 377.5 (4) Å³
Z = 2
Mo Kα radiation
μ = 22.56 mm⁻¹
T = 123 K
0.06 × 0.05 × 0.02 mm

Data collection

Nonius KappaCCD diffractometer
Absorption correction: multi-scan (SORTAV; Blessing, 1997 ▶) T _min = 0.345, T _max = 0.661
6589 measured reflections
2157 independent reflections
2027 reflections with I > 2σ(I)
R _int = 0.059

Refinement

R[F ² > 2σ(F ²)] = 0.032
wR(F ²) = 0.085
S = 1.09
2157 reflections
93 parameters
1 restraint
H-atom parameters constrained
Δρ_max = 2.76 e Å⁻³
Δρ_min = −3.17 e Å⁻³
Absolute structure: Flack (1983 ▶), 966 Friedel pairs
Flack parameter: 0.03 (2)

Data collection: COLLECT (Hooft, 1998 ▶); cell refinement: DENZO (Otwinowski & Minor, 1997 ▶); data reduction: SCALEPACK (Otwinowski & Minor, 1997 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: SHELXL97.

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536812011877/hb6608sup1.cif

e-68-0m489-sup1.cif^{(19KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536812011877/hb6608Isup2.hkl

e-68-0m489-Isup2.hkl^{(103.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Pb1—N1	2.444 (9)
Pb1—O1	2.451 (7)
Pb1—S1	2.714 (2)
Pb1—O1ⁱ	2.719 (7)
Pb1—S1ⁱⁱ	3.091 (3)
Pb1—S1ⁱⁱⁱ	3.465 (3)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Table 2. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1B⋯S1ⁱⁱⁱ	0.92	2.59	3.453 (8)	156
N1—H1A⋯O2^iv	0.92	2.24	3.070 (10)	150

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Symmetry codes: (iii) Inline graphic ; (iv) .

Acknowledgments

This research was supported by the National Science and Engineering Research Council (NSERC) of Canada, the Canadian Foundation for Innovation (CFI) and the Province of Alberta (Department of Innovation and Science).

supplementary crystallographic information

Comment

Lead is a serious environmental contaminant. The extensive use of lead as metal and in lead compounds into modern times, e. g., in alkyl lead additives in leaded gasoline, battery manufacturing and in paints, has made lead a ubiquitous pollutant in the ecosystem. The soluble Pb^II ion with its 5 d¹⁰ 6 s² electronic configuration in the valence shell has a very flexible coordination behaviour. It is a neurotoxic heavy metal ion that perturbs multiple enzyme systems affecting areas of the brain that regulate behavior and nerve cell development and any site with sulfhydryl groups is vulnerable (Needleman, 2004). In particular Zn(II) can be replaced in enzymes, e. g., inhibiting the heme biosynthetic pathway, even though the effective ionic radius in four-coordination of the soft Pb^II ion (0.98 Å) is significantly larger than that of Zn^II (0.60 Å). Pb^II can also adapt to replace Ca(II) in bone (Bressler et al., 1999; Godwin, 2001).

Treatments of lead(II) poisoning are mainly based on using chelators that form strong bonds to heavy metal ions, such as the disodium salt of the calcium edta complex (CaNa₂edta) and dimercaprol (BAL), which are injected, and DMSA (meso-2, 3-dimercaptosuccinic acid) and D-penicillamine (H₂Pen), which are administered orally (Sinicropi et al., 2010; Casas & Sordo, 2006).

The binding of Pb^II to the tridentate chelator H₂Pen containing a sulfhydryl group is of interest for better understanding of the coordination behaviour in biological systems and for the design of specific detoxifying agents. The coordination geometry around the Pb^II ion in the crystalline title compound (PbPen), which precipitates in a wide pH range from penicillamine solutions containing lead(II) ions, was previously discussed by Freeman et al., (1974). However, the atomic coordinates of the crystal structure were not reported, nor deposited in the Cambridge Structural Database (refcode: DPENPB]. Here, we report the crystal structure of PbPen, and also discuss the Pb—Pb distances in this polymeric structure with double bridged thiolate chains.

Mixing Pb(NO₃)₂ and D-penicillamine in 1:2 molar ratio resulted in a 1:1 complex, PbPen, formed in an alkaline solution. The ligand is coordinated to the Pb^II ion in a tridentate mode: Pb—N 2.444 (9) Å, Pb—O 2.451 (7) Å and Pb—S 2.714 (2) Å (Fig. 1). The sulfur atom acts as a bridge with Pb—S distances of 3.091 (2) and 3.464 (2) Å to two other neighbouring Pb^II ions located at 4.363 Å relative to the original Pb^II ion, forming a double thiolate chain in a polymeric structure. Moreover, the coordinated carboxylate oxygen atom forms bridges to the lead ions (Pb—O 2.720 (7) Å) in the adjacent chain with two Pb^II ions at 4.663 Å relative to the central Pb^II ion (Fig. 2). The coordination sphere of lead can be described as a distorted pentagonal bipyramid if the Pb—O interactions to the carboxylate oxygen atoms are considered as axial interaction opposite the short Pb—S bond (2.714 (2) Å), and also including a possible stereochemically active inert electron pair in the void in the equatorial plane between the two long Pb—S interactions, 3.091 (2) Å and 3.464 (2) Å (Fig. 3) (Freeman et al., 1974).

The amino H-atoms of the title complex are hydrogen bonded to a S-atom (N1—H1B···S1) along the a-axis and an O-atom (N1—H1A···O2) along the b-axis resulting in a cluster of four complex units giving rise to a 16-membered ring in the ab-plane which can be best described as a R₄⁴(16) motif in the graph set notation (Bernstein et al., 1994) (Fig. 4).

Experimental

To a solution of 2 mmol penicillamine (H₂Pen) in boiled O₂-free water, 1 mmol Pb(NO₃)₂ was added, forming a white precipitate, which was dissolved by adding 2 and 6 M NaOH solution, increasing the pH to 11.2; [Pb²⁺] = 0.1 M. After several days in the refrigerator colorless plates formed.