catena-Poly[copper(II)-bis­(μ-2-ethyl-5-methyl­imidazole-4-sulfonato-κ3 N 3,O 4:O 4′)]

Andrew P Purdy; Ray J Butcher

doi:10.1107/S160053681103409X

. 2011 Aug 27;67(Pt 9):m1303–m1304. doi: 10.1107/S160053681103409X

catena-Poly[copper(II)-bis(μ-2-ethyl-5-methylimidazole-4-sulfonato-κ³ N ³,O ⁴:O ^4′)]

Andrew P Purdy ^a,^*, Ray J Butcher ^b

PMCID: PMC3200726 PMID: 22058889

Abstract

In the title compound, [Cu(C₆H₉N₂O₃S)₂]_n, the copper(II) ion sits on an inversion center and is chelated by the imidazole N and sulfonate O atoms of two ligands in equatorial positions. O atoms of adjacent molecules coordinate in the axial positions. Jahn–Teller tetragonal distortion is evident in the coordination geometry [Cu—N and Cu—O equatorial distances of 1.971 (3) and 2.045 (2) Å, respectively, with a Cu—O axial distance of 2.433 (3) Å]. The structure is propagated by an infinite chain of eight-membered (Cu—O—S—O)₂ ring systems along the a axis. Only N—H⋯O hydrogen bonding exists between the chains.

Related literature

For literature related to the 2-ethyl-4-methylimidazole-5-sulfonic acid ligand, see: Purdy et al. (2007 ▶). For sulfonate-bridged Cu complexes with Cu–sulfonate chains, see: van Albada et al. (2001 ▶); Cai et al. (2004 ▶); Doyle et al. (1983 ▶); Han et al. (2006 ▶); He et al. (2009 ▶); Hubig et al. (2000 ▶); Sreenivasulu et al. (2005 ▶); Timmermans et al. (1984 ▶). For geometric data, see: Jahn & Teller (1937 ▶).

Experimental

Crystal data

[Cu(C₆H₉N₂O₃S)₂]
M _r = 441.96
Monoclinic,
a = 5.0732 (4) Å
b = 11.8367 (10) Å
c = 13.6810 (11) Å
β = 94.473 (7)°
V = 819.04 (12) Å³
Z = 2
Cu Kα radiation
μ = 4.64 mm⁻¹
T = 295 K
0.44 × 0.32 × 0.24 mm

Data collection

Oxford Diffraction Xcalibur Ruby Gemini diffractometer
Absorption correction: analytical [CrysAlis PRO (Oxford Diffraction, 2007 ▶) based on expressions derived by Clark & Reid (1995 ▶)T _min = 0.270, T _max = 0.445
3114 measured reflections
1704 independent reflections
1605 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.064
wR(F ²) = 0.181
S = 1.08
1704 reflections
117 parameters
H-atom parameters constrained
Δρ_max = 1.15 e Å⁻³
Δρ_min = −0.84 e Å⁻³

Data collection: CrysAlis PRO (Oxford Diffraction, 2007 ▶); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S160053681103409X/om2453sup1.cif

e-67-m1303-sup1.cif^{(21KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681103409X/om2453Isup2.hkl

e-67-m1303-Isup2.hkl^{(84KB, hkl)}

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

Table 1. Selected geometric parameters (Å, °).

Cu1—N1	1.971 (3)
Cu1—O1	2.045 (2)
Cu1—O1ⁱ	2.045 (2)
Cu1—O3ⁱⁱ	2.433 (3)

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

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

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2C⋯O2ⁱⁱⁱ	0.86	1.95	2.784 (4)	164

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Symmetry code: (iii) Inline graphic .

Acknowledgments

RJB wishes to acknowledge the NSF-MRI program (grant No. CHE-0619278) for funds to purchase the diffractometer, and we thank the Office of Naval Research for financial support.

supplementary crystallographic information

Comment

In the title compound, the copper(II) ion sits on an inversion center and is chelated by the imidazole N1 and sulfonate O1 of two ligands. The two chelate rings on a Cu are 5-membered and co-planar. Two O3 O atoms of adjacent molecules coordinate the axial positions with the usual Jahn-Teller tetragonal distortion (Jahn & Teller, 1937) ((Cu—N and Cu—O equatorial distances of 1.971 (3) and 2.045 (2) Å, respectively, with a Cu—O axial distance of 2.433 (3) Å) and link the Cu atoms in an infinite chain of 8-membered (Cu—O—S—O)₂ rings along the a axis. A number of examples exist for catenated 8-membered rings of sulfonate bridged copper(I) ions - Doyle et al. (1983), Han et al. (2006), Timmermans et al. (1984), and Hubig et al. (2000). All previous examples have 4 or 5 coordinate copper(I) and edge-shared catenation between the rings. This infinite chain of (Cu—O—S—O)₂ rings is unique for copper(II), and its rings are corner shared and linear. The Cu coordination is nearly octahedral, with adjacent angles ranging from 84.92 (10) to 93.10 (10)°. Our silver(I) complex of the same ligand (Purdy, et al. (2007)) has edge shared 8-membered rings connected by a tetrahedral Ag atom. The CuO₄ moieties are planar, and are nearly perpendicular (85.00 (8)°) to a plane composed of the linear N—Cu—N units within a chain. Likewise the plane formed by the 5-membered Cu—N—C—S—O chelate rings forms a dihedral angle of 86.61 (8)° with the plane formed by the Cu and O3 atoms within a chain.

As noted above, although all Cu—O distances are within the ranges normally observed in sulfonate complexes, the Cu—O3 distance is 0.4 Å longer than Cu—O1 as is seen in bis(µ₂-(2-((2-oxybenzylidene)amino)ethyl)sulfonato)-diaqua-dicopper(II) dihydrate and other similar chelated copper(II) sulfonates (Sreenivasulu et al., 2005; Cai et al., 2004). Copper(II) sulfonates where the sulfonate is not part of a chelate ring tend to have Cu—O distance of 2.3 Å or greater as for example in bis(µ₂-hydroxo)-bis(µ₂-trifluoromethanesulfonato-O,O')-bis(4,4- dimethyl-2,2'-bipyridine)-di-copper(II) (van Albada, et al., 2001) and in a sulfonate bridged complex (He, et al., 2009).

The O2 atoms of the sulfonates are hydrogen bonded to the hydogen on N2 of the imidazole ring of an adjacent chain, at a N—O distance of 2.784 (4) Å. This interaction bonds the chains into a fully three-dimensional structure.

Experimental

Both 1:1 and 1:1.5 solutions of the potassium salts of the 2-ethyl-4-methyl-imidazole-5-sulfonic acid were prepared by combining 1 g (5.25 mmol) of the free acid with 1 and 1.5 equivalents of KOH solution respectively, and diluting the solutions to 1M based on K⁺. (All solutions were made with distilled water.) Two test reactions were done in vials with a 1M solution of CuCl₂.2H₂O, and a 0.2 ml metered pipet was used for the additions. In reaction #1, 0.2 ml of CuCl₂ solution was combined with 0.4 ml of the 1:1 solution. In reaction #2, 0.4 ml or the CuCl₂ solution was combined with 0.6 ml of the 1:1.5 solution. Both solutions were heated to a boil and allowed to cool. Both reactions produced a pale green precipitate, but green crystals of the title compound grow in #2 only, over several days.