Di-μ-nitrito-κ⁴ O:O-bis­[bis­(1-ethyl-1H-imidazole-κN ³)(nitrito-κO)copper(II)]

Abstract

In the structure of the title compound, [Cu₂(NO₂)₄(C₅H₈N₂)₄], the asymmetric unit consists of two moieties containing one Cu ion, two nitrite ions and two 1-ethyl-1H-imidazole mol­ecules associated via weak Cu—O inter­actions. Each Cu^II atom displays an elongted square-pyramidal CuN₂O₃ coordination geometry with a slight tetra­hedral distortion in the basal plane. The dimeric units are linked into a three-dimensional network by C—H⋯O hydrogen bonds.

Related literature

For general background on ferroelectric metal–organic compounds with framework structures, see: Fu et al. (2009 ▶); Ye et al. (2006 ▶); Zhang et al. (2008 ▶, 2010 ▶). For a related structure, see: Costes et al. (1995 ▶).

Experimental

Crystal data

• [Cu₂(NO₂)₄(C₅H₈N₂)₄]

• M _r = 695.64

• Tetragonal,

• a = 28.136 (7) Å

• c = 7.669 (2) Å

• V = 6071 (3) ų

• Z = 8

• Mo Kα radiation

• μ = 1.46 mm⁻¹

• T = 293 K

• 0.30 × 0.25 × 0.20 mm

Data collection

• Rigaku SCXmini CCD diffractometer

• Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ▶) T _min = 0.651, T _max = 0.746

• 31845 measured reflections

• 3462 independent reflections

• 3188 reflections with I > 2σ(I)

• R _int = 0.049

Refinement

• R[F ² > 2σ(F ²)] = 0.049

• wR(F ²) = 0.127

• S = 1.15

• 3462 reflections

• 191 parameters

• H-atom parameters constrained

• Δρ_max = 0.82 e Å⁻³

• Δρ_min = −0.59 e Å⁻³

Data collection: CrystalClear (Rigaku, 2005 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; 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: SHELXL97.

Supplementary Material

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

supplementary crystallographic information

Comment

As part of our ongoing study of potential ferroelectric phase change materials we have determined the structures of several copper complexes and examined the changes in their dielectric constants with temperature. This is the usual method for detecting such behavior. (Fu et al., 2009; Ye et al., 2006; Zhang et al., 2008; Zhang et al., 2010). Unfortunately, the dielectric constant for (I) does not show any behavior indicating the onset of a ferroelectric phase change over the range 80 K to 298 K (m.p.219–229).

As shown in Fig. 1, the Cu ion adopts an elongated square pyramidal geometry with a slight tetrahedral distortion in the basal plane which is primarily associated with the coordination of the nitrite ions (O1—Cu1—O3 = 164.12 (11)°). This displaces O3 from the ideal coordination plane towards the centrosymmetrically-related copper atom (Cu1') resulting in an O3—Cu1' distance of 2.637 (2) Å. While this distance is considerably longer than the in-plane Cu1—O1 and Cu—O3 bond lengths of 2.025 (3) Å and 2.058 (5) Å, respectively, the direction of displacement of O3 and the orientations of the two nitrite ligands which place both O1 and O4 on the opposite side of the coordination plane from Cu1', suggests that there is a weak association of one Cu(NO₂)₂(C₅H₈N₂)₂unit with its centrosymmetrically-related counterpart. A similar weak association has been postulated to occur between two similar centrosymmetrically related Cu(NO₂)(OC(CH₃)CHC(CH₃)N(CH₂)₂NH₂) units (Cu—O = 2.014 (4) Å, Cu'—O = 2.634 (3) Å) (Costes, et al. 1995).

Experimental

An aqueous solution of 1-ethyl imidazole (2.4 g, 25 mmol) and H₂SO₄(12.5 mmol) was treated with CuSO₄ (250 g, 12.5 mmol). After the mixture was stirred for a few minutes, Ba(NO₂)₂ (6.18 g, 25 mmol) was added to give a blue solution. Slow evaporation of the solution following removal of the precipitated BaSO₄ yielded blue crystals after a few days.

Refinement

All H atoms were placed in geometrically idealized positions and constrained to ride on their parent atoms with C—H = 0.93–0.96 Å, and with U_iso(H) = 1.2 U_iso(C) or 1.5 U_iso(C) for ethy H atoms.

Figures

Fig. 1.

A view of the title compound with the displacement ellipsoids drawn at the 30% probability level.

Fig. 2.

Packing diagram of the title compound. The weak Cu—O interactions and the hydrogen bonds are shown as dashed lines.

Crystal data

[Cu2(NO2)4(C5H8N2)4]	Dx = 1.522 Mg m−3
Mr = 695.64	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I41/a	Cell parameters from 7423 reflections
Hall symbol: -I 4ad	θ = 2.3–27.5°
a = 28.136 (7) Å	µ = 1.46 mm−1
c = 7.669 (2) Å	T = 293 K
V = 6071 (3) Å3	Prism, blue
Z = 8	0.30 × 0.25 × 0.20 mm
F(000) = 2864

Data collection

Rigaku SCXmini CCD diffractometer	3462 independent reflections
Radiation source: fine-focus sealed tube	3188 reflections with I > 2σ(I)
graphite	Rint = 0.049
ω scans	θmax = 27.5°, θmin = 2.8°
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	h = −36→35
Tmin = 0.651, Tmax = 0.746	k = −36→36
31845 measured reflections	l = −9→9

Refinement

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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.127	H-atom parameters constrained
S = 1.15	w = 1/[σ2(Fo2) + (0.0575P)2 + 9.3008P] where P = (Fo2 + 2Fc2)/3
3462 reflections	(Δ/σ)max = 0.001
191 parameters	Δρmax = 0.82 e Å−3
0 restraints	Δρmin = −0.59 e Å−3

Special details

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

	x	y	z	Uiso*/Ueq
Cu1	0.296007 (12)	0.280780 (13)	0.10562 (4)	0.03905 (14)
O1	0.31265 (8)	0.25812 (8)	−0.1376 (3)	0.0515 (5)
O2	0.36079 (10)	0.31480 (11)	−0.1169 (4)	0.0703 (7)
O3	0.26607 (9)	0.28842 (10)	0.3494 (4)	0.0622 (6)
O4	0.31466 (11)	0.34387 (11)	0.3593 (4)	0.0786 (9)
N1	0.20821 (9)	0.36827 (10)	−0.1798 (4)	0.0506 (6)
N2	0.25052 (8)	0.32796 (9)	0.0093 (3)	0.0429 (5)
N3	0.34610 (10)	0.28278 (12)	−0.2076 (4)	0.0567 (7)
N4	0.28338 (14)	0.32269 (14)	0.4337 (4)	0.0726 (10)
N5	0.34476 (8)	0.23769 (8)	0.2053 (3)	0.0385 (5)
N6	0.38648 (9)	0.19735 (9)	0.3968 (3)	0.0423 (5)
C1	0.23921 (11)	0.33283 (11)	−0.1568 (4)	0.0463 (7)
H1	0.2512	0.3140	−0.2462	0.056*
C2	0.19876 (13)	0.38696 (13)	−0.0200 (5)	0.0615 (9)
H2	0.1782	0.4120	0.0043	0.074*
C3	0.22491 (13)	0.36229 (13)	0.0964 (5)	0.0597 (9)
H3	0.2255	0.3676	0.2161	0.072*
C4	0.2044 (3)	0.4277 (2)	−0.4124 (8)	0.122 (2)
H4A	0.1894	0.4348	−0.5217	0.182*
H4B	0.2382	0.4260	−0.4286	0.182*
H4C	0.1971	0.4522	−0.3295	0.182*
C5	0.18697 (14)	0.38208 (15)	−0.3476 (5)	0.0690 (11)
H5A	0.1901	0.3558	−0.4286	0.083*
H5B	0.1533	0.3878	−0.3305	0.083*
C6	0.35428 (10)	0.23166 (10)	0.3735 (4)	0.0405 (6)
H6	0.3404	0.2490	0.4632	0.049*
C7	0.37254 (11)	0.20505 (11)	0.1186 (4)	0.0461 (7)
H7	0.3735	0.2009	−0.0016	0.055*
C8	0.40610 (12)	0.18264 (12)	0.5666 (4)	0.0511 (7)
H8A	0.4144	0.1492	0.5617	0.061*
H8B	0.3820	0.1866	0.6558	0.061*
C9	0.44914 (14)	0.21084 (15)	0.6157 (6)	0.0697 (11)
H9A	0.4734	0.2065	0.5291	0.105*
H9B	0.4607	0.2002	0.7268	0.105*
H9C	0.4409	0.2439	0.6228	0.105*
C10	0.39807 (11)	0.18017 (11)	0.2355 (4)	0.0492 (7)
H10	0.4195	0.1559	0.2113	0.059*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Cu1	0.0390 (2)	0.0460 (2)	0.0321 (2)	0.00571 (13)	0.00052 (13)	0.00114 (13)
O1	0.0565 (13)	0.0524 (12)	0.0458 (12)	0.0022 (10)	−0.0071 (10)	−0.0053 (10)
O2	0.0689 (17)	0.0750 (18)	0.0670 (17)	−0.0149 (14)	−0.0035 (13)	0.0023 (14)
O3	0.0548 (14)	0.0698 (16)	0.0622 (16)	0.0070 (12)	−0.0010 (12)	0.0094 (13)
O4	0.0654 (17)	0.0681 (17)	0.102 (2)	−0.0119 (14)	−0.0124 (16)	0.0019 (16)
N1	0.0453 (14)	0.0531 (15)	0.0533 (16)	0.0069 (11)	−0.0072 (12)	0.0064 (12)
N2	0.0424 (13)	0.0464 (13)	0.0400 (13)	0.0058 (10)	0.0016 (10)	0.0036 (10)
N3	0.0550 (16)	0.077 (2)	0.0380 (14)	0.0110 (14)	0.0067 (12)	0.0059 (14)
N4	0.078 (2)	0.086 (2)	0.0532 (18)	0.031 (2)	−0.0105 (17)	−0.0114 (17)
N5	0.0373 (11)	0.0406 (12)	0.0377 (12)	0.0023 (9)	0.0004 (9)	0.0001 (10)
N6	0.0419 (13)	0.0409 (12)	0.0441 (13)	0.0018 (10)	−0.0018 (10)	0.0061 (10)
C1	0.0435 (15)	0.0509 (17)	0.0446 (16)	0.0051 (13)	−0.0030 (12)	0.0010 (13)
C2	0.058 (2)	0.058 (2)	0.068 (2)	0.0182 (16)	0.0029 (17)	0.0028 (17)
C3	0.065 (2)	0.067 (2)	0.0463 (18)	0.0236 (17)	0.0062 (15)	−0.0030 (16)
C4	0.178 (6)	0.091 (4)	0.096 (4)	−0.014 (4)	−0.050 (4)	0.042 (3)
C5	0.062 (2)	0.079 (3)	0.067 (2)	0.0125 (19)	−0.0202 (18)	0.014 (2)
C6	0.0411 (14)	0.0434 (15)	0.0370 (14)	0.0035 (11)	−0.0009 (11)	0.0003 (11)
C7	0.0506 (17)	0.0440 (15)	0.0437 (16)	0.0043 (13)	0.0045 (13)	−0.0041 (12)
C8	0.0530 (17)	0.0497 (17)	0.0505 (18)	0.0039 (13)	−0.0085 (14)	0.0125 (14)
C9	0.060 (2)	0.067 (2)	0.082 (3)	−0.0045 (17)	−0.028 (2)	0.011 (2)
C10	0.0492 (16)	0.0441 (16)	0.0543 (18)	0.0097 (12)	0.0024 (14)	−0.0011 (14)

Geometric parameters (Å, °)

Cu1—N5	1.984 (2)	C2—C3	1.350 (5)
Cu1—N2	1.987 (2)	C2—H2	0.9300
Cu1—O1	2.026 (2)	C3—H3	0.9300
Cu1—O3	2.062 (3)	C4—C5	1.460 (7)
O1—N3	1.287 (4)	C4—H4A	0.9600
O2—N3	1.211 (4)	C4—H4B	0.9600
O3—N4	1.259 (4)	C4—H4C	0.9600
O4—N4	1.206 (5)	C5—H5A	0.9705
N1—C1	1.337 (4)	C5—H5B	0.9686
N1—C2	1.360 (5)	C6—H6	0.9300
N1—C5	1.471 (4)	C7—C10	1.345 (4)
N2—C1	1.319 (4)	C7—H7	0.9300
N2—C3	1.378 (4)	C8—C9	1.496 (5)
N5—C6	1.329 (4)	C8—H8A	0.9700
N5—C7	1.377 (4)	C8—H8B	0.9700
N6—C6	1.336 (4)	C9—H9A	0.9600
N6—C10	1.368 (4)	C9—H9B	0.9600
N6—C8	1.474 (4)	C9—H9C	0.9600
C1—H1	0.9300	C10—H10	0.9300
N5—Cu1—N2	175.68 (10)	C5—C4—H4B	109.5
N5—Cu1—O1	90.14 (10)	H4A—C4—H4B	109.5
N2—Cu1—O1	90.96 (10)	C5—C4—H4C	109.5
N5—Cu1—O3	89.82 (10)	H4A—C4—H4C	109.5
N2—Cu1—O3	90.25 (10)	H4B—C4—H4C	109.5
O1—Cu1—O3	164.17 (11)	C4—C5—N1	113.2 (4)
N3—O1—Cu1	112.57 (19)	C4—C5—H5A	114.9
N4—O3—Cu1	112.8 (2)	N1—C5—H5A	108.7
C1—N1—C2	107.3 (3)	C4—C5—H5B	103.2
C1—N1—C5	125.3 (3)	N1—C5—H5B	108.8
C2—N1—C5	127.4 (3)	H5A—C5—H5B	107.6
C1—N2—C3	105.6 (3)	N5—C6—N6	111.0 (3)
C1—N2—Cu1	125.7 (2)	N5—C6—H6	124.5
C3—N2—Cu1	128.7 (2)	N6—C6—H6	124.5
O2—N3—O1	114.3 (3)	C10—C7—N5	109.2 (3)
O4—N4—O3	114.7 (3)	C10—C7—H7	125.4
C6—N5—C7	105.6 (2)	N5—C7—H7	125.4
C6—N5—Cu1	126.3 (2)	N6—C8—C9	112.1 (3)
C7—N5—Cu1	127.9 (2)	N6—C8—H8A	109.2
C6—N6—C10	107.2 (2)	C9—C8—H8A	109.2
C6—N6—C8	125.1 (3)	N6—C8—H8B	109.2
C10—N6—C8	127.6 (3)	C9—C8—H8B	109.2
N2—C1—N1	111.3 (3)	H8A—C8—H8B	107.9
N2—C1—H1	124.4	C8—C9—H9A	109.5
N1—C1—H1	124.4	C8—C9—H9B	109.5
C3—C2—N1	106.9 (3)	H9A—C9—H9B	109.5
C3—C2—H2	126.5	C8—C9—H9C	109.5
N1—C2—H2	126.5	H9A—C9—H9C	109.5
C2—C3—N2	108.9 (3)	H9B—C9—H9C	109.5
C2—C3—H3	125.5	C7—C10—N6	107.0 (3)
N2—C3—H3	125.5	C7—C10—H10	126.5
C5—C4—H4A	109.5	N6—C10—H10	126.5
N5—Cu1—O1—N3	−89.0 (2)	Cu1—N2—C1—N1	−179.0 (2)
N2—Cu1—O1—N3	86.8 (2)	C2—N1—C1—N2	−0.5 (4)
O3—Cu1—O1—N3	−178.8 (3)	C5—N1—C1—N2	−177.7 (3)
N5—Cu1—O3—N4	90.2 (2)	C1—N1—C2—C3	0.5 (4)
N2—Cu1—O3—N4	−85.4 (2)	C5—N1—C2—C3	177.6 (4)
O1—Cu1—O3—N4	−179.9 (3)	N1—C2—C3—N2	−0.3 (4)
N5—Cu1—N2—C1	109.0 (13)	C1—N2—C3—C2	0.0 (4)
O1—Cu1—N2—C1	4.2 (3)	Cu1—N2—C3—C2	179.3 (2)
O3—Cu1—N2—C1	−160.0 (3)	C1—N1—C5—C4	−109.8 (5)
N5—Cu1—N2—C3	−70.1 (14)	C2—N1—C5—C4	73.6 (6)
O1—Cu1—N2—C3	−174.9 (3)	C7—N5—C6—N6	0.3 (3)
O3—Cu1—N2—C3	20.9 (3)	Cu1—N5—C6—N6	175.07 (18)
Cu1—O1—N3—O2	−0.8 (3)	C10—N6—C6—N5	−0.4 (3)
Cu1—O3—N4—O4	−1.6 (4)	C8—N6—C6—N5	178.0 (3)
N2—Cu1—N5—C6	77.2 (14)	C6—N5—C7—C10	0.0 (3)
O1—Cu1—N5—C6	−178.0 (2)	Cu1—N5—C7—C10	−174.7 (2)
O3—Cu1—N5—C6	−13.8 (3)	C6—N6—C8—C9	−88.7 (4)
N2—Cu1—N5—C7	−109.1 (13)	C10—N6—C8—C9	89.4 (4)
O1—Cu1—N5—C7	−4.3 (2)	N5—C7—C10—N6	−0.3 (4)
O3—Cu1—N5—C7	159.9 (3)	C6—N6—C10—C7	0.4 (3)
C3—N2—C1—N1	0.3 (4)	C8—N6—C10—C7	−178.0 (3)