catena-Poly[copper(II)-bis­(μ-2-ethyl-5-methyl­imidazole-4-sulfonato-κ3N3,O4:O4′)]

Purdy, A.P.; Butcher, R.J.

doi:10.1107/S160053681103409X

metal-organic compounds

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ISSN: 2056-9890

Volume 67| Part 9| September 2011| Pages m1303-m1304

doi:10.1107/S160053681103409X

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catena-Poly[copper(II)-bis(μ-2-ethyl-5-methylimidazole-4-sulfonato-κ³N³,O⁴:O^4′)]

Andrew P. Purdy ^a ^* and Ray J. Butcher ^b

^aChemistry Division, Code 6120 Naval Research Laboratory, 4555 Overlook Avenue SW, Washington, DC 20375, USA, and ^bDepartment of Chemistry, Howard University, 525 College Street NW, Washington, DC 20059, USA
^*Correspondence e-mail: andrew.purdy@nrl.navy.mil

(Received 19 July 2011; accepted 19 August 2011; online 27 August 2011)

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, P 2₁ /c
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 $[Oxford Diffraction (2007). CrysAlis PRO. Oxford Diffraction Ltd, Abingdon, England.]$ ) 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[F² > 2σ(F²)] = 0.064
wR(F²) = 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

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)
Symmetry codes: (i) -x+1, -y+1, -z+1; (ii) x-1, y, z.

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
Symmetry code: (iii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Data collection: CrysAlis PRO (Oxford Diffraction, 2007 $[Oxford Diffraction (2007). CrysAlis PRO. Oxford Diffraction Ltd, Abingdon, England.]$ ); 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.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053681103409X/om2453sup1.cif

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

checkCIF report

Comment top

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.

Related literature top

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 top

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.

Computing details top

Data collection: CrysAlis PRO (Oxford Diffraction, 2007); cell refinement: CrysAlis PRO (Oxford Diffraction, 2007); data reduction: CrysAlis PRO (Oxford Diffraction, 2007); 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 (Sheldrick, 2008).

Figures top

	Fig. 1. Diagram of C₁₂H₁₈CuN₄O₆S₂ illustrating the atom numbering scheme used. Thermal displacement parameters are at the 30% probability level. [symmetry codes for labelled atoms: O1A, N1A, 1 - x, 1 - y, 1 - z; O3B, x - 1, y, z; O3C, 2 - x, 1 - y, 1 - z]
	Fig. 2. The molecular packing for C₁₂H₁₈CuN₄O₆S₂ viewed down the c axis.

catena-Poly[copper(II)-bis(µ-2-ethyl-5-methylimidazole-4-sulfonato- κ³N³,O⁴:O^4')] top

Crystal data top

[Cu(C₆H₉N₂O₃S)₂]	F(000) = 454
M_r = 441.96	D_x = 1.792 Mg m⁻³
Monoclinic, P2₁/c	Cu Kα radiation, λ = 1.54178 Å
Hall symbol: -P 2ybc	Cell parameters from 2637 reflections
a = 5.0732 (4) Å	θ = 5.0–77.1°
b = 11.8367 (10) Å	µ = 4.64 mm⁻¹
c = 13.6810 (11) Å	T = 295 K
β = 94.473 (7)°	Chunk, pale green-blue
V = 819.04 (12) Å³	0.44 × 0.32 × 0.24 mm
Z = 2

Data collection top

Oxford Diffraction Xcalibur Ruby Gemini diffractometer	1704 independent reflections
Radiation source: Enhance (Cu) X-ray sealed tube	1605 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.033
Detector resolution: 10.51 pixels mm^-1	θ_max = 77.6°, θ_min = 5.0°
ω scans	h = −6→6
Absorption correction: analytical (CrysAlis PRO; Oxford Diffraction, 2007; Clark & Reid, 1995)'	k = −14→14
T_min = 0.270, T_max = 0.445	l = −17→10
3114 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F² > 2σ(F²)] = 0.064	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.181	H-atom parameters constrained
S = 1.08	w = 1/[σ²(F_o²) + (0.1339P)² + 0.7529P] where P = (F_o² + 2F_c²)/3
1704 reflections	(Δ/σ)_max < 0.001
117 parameters	Δρ_max = 1.15 e Å⁻³
0 restraints	Δρ_min = −0.84 e Å⁻³

Crystal data top

[Cu(C₆H₉N₂O₃S)₂]	V = 819.04 (12) Å³
M_r = 441.96	Z = 2
Monoclinic, P2₁/c	Cu Kα radiation
a = 5.0732 (4) Å	µ = 4.64 mm⁻¹
b = 11.8367 (10) Å	T = 295 K
c = 13.6810 (11) Å	0.44 × 0.32 × 0.24 mm
β = 94.473 (7)°

Data collection top

Oxford Diffraction Xcalibur Ruby Gemini diffractometer	1704 independent reflections
Absorption correction: analytical (CrysAlis PRO; Oxford Diffraction, 2007; Clark & Reid, 1995)'	1605 reflections with I > 2σ(I)
T_min = 0.270, T_max = 0.445	R_int = 0.033
3114 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.064	0 restraints
wR(F²) = 0.181	H-atom parameters constrained
S = 1.08	Δρ_max = 1.15 e Å⁻³
1704 reflections	Δρ_min = −0.84 e Å⁻³
117 parameters

Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Cu1	0.5000	0.5000	0.5000	0.0255 (3)
S1	0.94199 (14)	0.32615 (6)	0.53104 (5)	0.0252 (3)
O1	0.8041 (5)	0.4192 (2)	0.57814 (17)	0.0327 (6)
O2	0.8628 (6)	0.2154 (2)	0.56252 (19)	0.0402 (7)
O3	1.2247 (5)	0.3403 (2)	0.53856 (19)	0.0345 (6)
N1	0.6262 (5)	0.4204 (2)	0.38608 (19)	0.0251 (6)
N2	0.7482 (6)	0.3464 (2)	0.2509 (2)	0.0283 (6)
H2C	0.7537	0.3326	0.1894	0.034*
C1	0.5837 (6)	0.4210 (3)	0.2898 (2)	0.0257 (6)
C2	0.3917 (8)	0.4933 (3)	0.2308 (3)	0.0316 (8)
H2A	0.4281	0.5717	0.2474	0.038*
H2B	0.2151	0.4763	0.2492	0.038*
C3	0.3959 (10)	0.4793 (4)	0.1198 (3)	0.0466 (10)
H3A	0.2724	0.5309	0.0872	0.070*
H3B	0.3475	0.4032	0.1018	0.070*
H3C	0.5704	0.4949	0.1008	0.070*
C4	0.9057 (7)	0.2957 (3)	0.3252 (2)	0.0272 (6)
C5	0.8264 (7)	0.3429 (3)	0.4086 (2)	0.0263 (6)
C6	1.1174 (8)	0.2112 (3)	0.3088 (3)	0.0375 (8)
H6A	1.2247	0.1995	0.3689	0.056*
H6B	1.2257	0.2389	0.2595	0.056*
H6C	1.0376	0.1410	0.2875	0.056*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0248 (4)	0.0294 (5)	0.0230 (4)	0.0050 (2)	0.0057 (3)	−0.0033 (2)
S1	0.0256 (5)	0.0264 (5)	0.0241 (5)	0.0014 (3)	0.0055 (3)	0.0015 (2)
O1	0.0322 (12)	0.0400 (13)	0.0261 (11)	0.0090 (10)	0.0036 (9)	−0.0048 (9)
O2	0.0507 (16)	0.0371 (15)	0.0333 (13)	−0.0043 (12)	0.0073 (11)	0.0076 (10)
O3	0.0269 (12)	0.0368 (13)	0.0401 (14)	0.0023 (9)	0.0048 (10)	0.0012 (10)
N1	0.0245 (12)	0.0257 (13)	0.0258 (13)	0.0007 (10)	0.0066 (10)	−0.0016 (9)
N2	0.0323 (15)	0.0299 (13)	0.0235 (12)	0.0021 (11)	0.0079 (11)	−0.0032 (10)
C1	0.0267 (14)	0.0240 (14)	0.0273 (15)	−0.0009 (11)	0.0070 (11)	−0.0017 (11)
C2	0.0343 (18)	0.0326 (17)	0.0282 (17)	0.0050 (12)	0.0045 (14)	0.0017 (12)
C3	0.059 (3)	0.053 (2)	0.0269 (17)	0.012 (2)	0.0002 (17)	0.0004 (16)
C4	0.0287 (15)	0.0269 (14)	0.0269 (14)	0.0012 (12)	0.0071 (12)	−0.0021 (12)
C5	0.0293 (15)	0.0245 (14)	0.0256 (14)	0.0011 (12)	0.0050 (12)	0.0002 (11)
C6	0.0361 (18)	0.0340 (18)	0.0433 (19)	0.0102 (15)	0.0081 (15)	−0.0062 (15)

Geometric parameters (Å, º) top

Cu1—N1ⁱ	1.971 (3)	N2—C4	1.380 (4)
Cu1—N1	1.971 (3)	N2—H2C	0.8600
Cu1—O1	2.045 (2)	C1—C2	1.487 (5)
Cu1—O1ⁱ	2.045 (2)	C2—C3	1.529 (5)
Cu1—O3ⁱⁱ	2.433 (3)	C2—H2A	0.9700
Cu1—O3ⁱⁱⁱ	2.433 (3)	C2—H2B	0.9700
S1—O3	1.439 (3)	C3—H3A	0.9600
S1—O2	1.447 (3)	C3—H3B	0.9600
S1—O1	1.479 (2)	C3—H3C	0.9600
S1—C5	1.743 (3)	C4—C5	1.359 (4)
O3—Cu1^iv	2.433 (3)	C4—C6	1.497 (5)
N1—C1	1.318 (4)	C6—H6A	0.9600
N1—C5	1.385 (4)	C6—H6B	0.9600
N2—C1	1.352 (4)	C6—H6C	0.9600

N1ⁱ—Cu1—N1	180.00 (9)	C4—N2—H2C	125.2
N1ⁱ—Cu1—O1	95.08 (10)	N1—C1—N2	109.4 (3)
N1—Cu1—O1	84.92 (10)	N1—C1—C2	126.5 (3)
N1ⁱ—Cu1—O1ⁱ	84.92 (10)	N2—C1—C2	124.1 (3)
N1—Cu1—O1ⁱ	95.08 (10)	C1—C2—C3	114.7 (3)
O1—Cu1—O1ⁱ	180.000 (1)	C1—C2—H2A	108.6
N1ⁱ—Cu1—O3ⁱⁱ	88.44 (10)	C3—C2—H2A	108.6
N1—Cu1—O3ⁱⁱ	91.56 (10)	C1—C2—H2B	108.6
O1—Cu1—O3ⁱⁱ	86.90 (10)	C3—C2—H2B	108.6
O1ⁱ—Cu1—O3ⁱⁱ	93.10 (10)	H2A—C2—H2B	107.6
N1ⁱ—Cu1—O3ⁱⁱⁱ	91.56 (10)	C2—C3—H3A	109.5
N1—Cu1—O3ⁱⁱⁱ	88.44 (10)	C2—C3—H3B	109.5
O1—Cu1—O3ⁱⁱⁱ	93.10 (10)	H3A—C3—H3B	109.5
O1ⁱ—Cu1—O3ⁱⁱⁱ	86.90 (10)	C2—C3—H3C	109.5
O3ⁱⁱ—Cu1—O3ⁱⁱⁱ	180.0	H3A—C3—H3C	109.5
O3—S1—O2	112.46 (16)	H3B—C3—H3C	109.5
O3—S1—O1	112.61 (15)	C5—C4—N2	104.3 (3)
O2—S1—O1	113.19 (16)	C5—C4—C6	131.6 (3)
O3—S1—C5	108.32 (16)	N2—C4—C6	124.1 (3)
O2—S1—C5	108.00 (16)	C4—C5—N1	110.2 (3)
O1—S1—C5	101.46 (15)	C4—C5—S1	131.3 (3)
S1—O1—Cu1	118.92 (14)	N1—C5—S1	118.4 (2)
S1—O3—Cu1^iv	131.33 (15)	C4—C6—H6A	109.5
C1—N1—C5	106.6 (3)	C4—C6—H6B	109.5
C1—N1—Cu1	138.6 (2)	H6A—C6—H6B	109.5
C5—N1—Cu1	114.7 (2)	C4—C6—H6C	109.5
C1—N2—C4	109.5 (3)	H6A—C6—H6C	109.5
C1—N2—H2C	125.2	H6B—C6—H6C	109.5

O3—S1—O1—Cu1	128.60 (17)	Cu1—N1—C1—C2	−1.4 (5)
O2—S1—O1—Cu1	−102.44 (19)	C4—N2—C1—N1	−0.5 (4)
C5—S1—O1—Cu1	13.0 (2)	C4—N2—C1—C2	178.2 (3)
N1ⁱ—Cu1—O1—S1	167.66 (17)	N1—C1—C2—C3	177.2 (4)
N1—Cu1—O1—S1	−12.34 (17)	N2—C1—C2—C3	−1.2 (5)
O3ⁱⁱ—Cu1—O1—S1	79.50 (17)	C1—N2—C4—C5	0.3 (4)
O3ⁱⁱⁱ—Cu1—O1—S1	−100.50 (17)	C1—N2—C4—C6	−177.9 (3)
O2—S1—O3—Cu1^iv	180.00 (18)	N2—C4—C5—N1	0.0 (4)
O1—S1—O3—Cu1^iv	−50.7 (2)	C6—C4—C5—N1	178.0 (3)
C5—S1—O3—Cu1^iv	60.7 (2)	N2—C4—C5—S1	−176.9 (3)
O1—Cu1—N1—C1	−170.2 (3)	C6—C4—C5—S1	1.1 (6)
O1ⁱ—Cu1—N1—C1	9.8 (3)	C1—N1—C5—C4	−0.2 (4)
O3ⁱⁱ—Cu1—N1—C1	103.0 (3)	Cu1—N1—C5—C4	−177.8 (2)
O3ⁱⁱⁱ—Cu1—N1—C1	−77.0 (3)	C1—N1—C5—S1	177.1 (2)
O1—Cu1—N1—C5	6.3 (2)	Cu1—N1—C5—S1	−0.5 (3)
O1ⁱ—Cu1—N1—C5	−173.7 (2)	O3—S1—C5—C4	50.0 (4)
O3ⁱⁱ—Cu1—N1—C5	−80.5 (2)	O2—S1—C5—C4	−72.1 (4)
O3ⁱⁱⁱ—Cu1—N1—C5	99.5 (2)	O1—S1—C5—C4	168.7 (3)
C5—N1—C1—N2	0.4 (4)	O3—S1—C5—N1	−126.7 (3)
Cu1—N1—C1—N2	177.1 (2)	O2—S1—C5—N1	111.3 (3)
C5—N1—C1—C2	−178.2 (3)	O1—S1—C5—N1	−8.0 (3)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x−1, y, z; (iii) −x+2, −y+1, −z+1; (iv) x+1, y, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2C···O2^v	0.86	1.95	2.784 (4)	164

Symmetry code: (v) x, −y+1/2, z−1/2.

Experimental details

Crystal data
Chemical formula	[Cu(C₆H₉N₂O₃S)₂]
M_r	441.96
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	295
a, b, c (Å)	5.0732 (4), 11.8367 (10), 13.6810 (11)
β (°)	94.473 (7)
V (Å³)	819.04 (12)
Z	2
Radiation type	Cu Kα
µ (mm⁻¹)	4.64
Crystal size (mm)	0.44 × 0.32 × 0.24

Data collection
Diffractometer	Oxford Diffraction Xcalibur Ruby Gemini diffractometer
Absorption correction	Analytical (CrysAlis PRO; Oxford Diffraction, 2007; Clark & Reid, 1995)'
T_min, T_max	0.270, 0.445
No. of measured, independent and observed [I > 2σ(I)] reflections	3114, 1704, 1605
R_int	0.033
(sin θ/λ)_max (Å⁻¹)	0.633

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.064, 0.181, 1.08
No. of reflections	1704
No. of parameters	117
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.15, −0.84

Computer programs: CrysAlis PRO (Oxford Diffraction, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected geometric parameters (Å, º) top

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

N1—Cu1—O1	84.92 (10)	O1—Cu1—O3ⁱⁱ	86.90 (10)
N1—Cu1—O3ⁱⁱ	91.56 (10)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x−1, y, z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2C···O2ⁱⁱⁱ	0.86	1.95	2.784 (4)	163.9

Symmetry code: (iii) x, −y+1/2, z−1/2.

Acknowledgements

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.

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