Crystal structure of the monoclinic phase (phase IV) of bis­(tetra­methyl­ammonium) tetra­chlorido­cuprate(II)

The crystal structure of the low-temperature monoclinic phase of (Me₄N)₂[CuCl₄] was determined at 120 K. The asymmetric unit consists of a discrete tetra­hedral [CuCl₄]²⁻ anion and two crystallographically independent tetra­methyl­ammonium cations.

Abstract

The crystal structure of the low-temperature monoclinic phase of the title compound, [(CH₃)₄N]₂[CuCl₄], was determined at 120 K. The structure of the room-temperature phase has been determined in the ortho­rhom­bic space group Pmcm [Morosin & Lingafelter (1961 ▸). J. Phys. Chem. 50–51; Clay et al. (1975 ▸). Acta Cryst. B31 289–290]. The asymmetric unit consists of one discrete tetra­chlorido­cuprate anion with a distorted tetra­hedral geometry and two tetra­methyl­ammonium cations. In the crystal, the cations and the anions are linked via weak C—H⋯Cl hydrogen bonds.

Chemical context  

The title compound undergoes successive phase transitions at 297, 291 and 263 K (Sugiyama et al., 1980 ▸). The room temperature phase (phase I) crystallizes in the ortho­rhom­bic space group Pmcm with Z = 4 (Morosin & Lingafelter, 1961 ▸; Clay et al., 1975 ▸). Three low-temperature phases, named phases II, III and IV in the order of decreasing temperature, show incommensurate, ferroelastic commensurate monoclinic and monoclinic structures, respectively (Sugiyama et al., 1980 ▸; Gesi & Iizumi, 1980 ▸). We allowed [(CH₃)₄N]Cl, CuCl₂ and thio­acetamide to react in ethanol. The expected mixed ligand complex was not crystallized but instead the title compound was obtained accidentally. The crystal structure of phase IV of the title compound was determined at 120 K and is reported herein.

Structural commentary  

The asymmetric unit of the title compound consists of a discrete [CuCl₄]²⁻ anion and two crystallographically tetra­methyl­ammonium cations (Fig. 1 ▸). In the anion, the four Cl atoms are inequivalent with Cu—Cl distances ranging from 2.2313 (15) to 2.2538 (16) Å. The Cl—Cu—Cl angles vary from 98.44 (7) to 133.69 (7)°, indicating a distorted tetra­hedral geometry around the Cu^II atom. Using Houser’s τ₄ metric [τ₄ = 360 − (α + β)/141], where α and β are the largest angles about the metal atom (Yang et al., 2007 ▸), we obtain a value of 0.658 for phase IV and 0.792 for the ortho­rhom­bic phase I. This indicates a greater deviation from an ideal tetra­hedron in phase IV compared with phase I, tending towards a ‘see-saw’ geometry.

Figure 1.

The asymmetric unit of the title compound showing the atom-labeling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are depicted as spheres of an arbitrary radius.

Supra­molecular features  

In the crystal, the cations and the anions are linked via weak C—H⋯Cl hydrogen bonds (Table 1 ▸ and Fig. 2 ▸), forming a three-dimensional network.

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C1—H1C⋯Cl2i	0.98	2.69	3.585 (7)	153
C2—H2A⋯Cl1ii	0.98	2.79	3.675 (7)	151
C2—H2A⋯Cl3ii	0.98	2.80	3.555 (7)	134
C2—H2B⋯Cl1i	0.98	2.79	3.674 (7)	150
C3—H3B⋯Cl4	0.98	2.74	3.670 (7)	159
C4—H4A⋯Cl3iii	0.98	2.59	3.555 (7)	166
C5—H5A⋯Cl2iv	0.98	2.68	3.635 (7)	165
C5—H5B⋯Cl3v	0.98	2.81	3.587 (6)	137
C5—H5C⋯Cl4i	0.98	2.63	3.610 (6)	173
C8—H8B⋯Cl1iii	0.98	2.76	3.650 (6)	151
C8—H8C⋯Cl2v	0.98	2.82	3.763 (7)	162

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .

Figure 2.

A packing diagram of the title compound, viewed along the a axis, showing the C—H⋯Cl hydrogen bonds (blue dashed lines).

Database survey  

A substructure search for compounds that incorporate a tetra­methyl­ammonium ion and a copper tetra­chloride species reveals thirteen structures (CSD November 2016; Groom et al., 2016 ▸). Of these, three are structures of (Me₄N)₂[CuCl₄] with a discrete [CuCl₄]²⁻ anion (Morosin & Lingafelter, 1961 ▸; Clay et al., 1975 ▸; Hlel et al., 2008 ▸).

Synthesis and crystallization  

On mixing [(CH₃)₄N]Cl (0.465 g, 4.2 mmol) in ethanol (10 ml) with CuCl₂·2H₂O (0.365 g, 2.1 mmol) in ethanol (10 ml) and thio­acetamide (0.160 g, 2.1 mmol) in ethanol (10 ml), a clear solution is obtained. Slow evaporation at room temperature (301 K) yielded pale-green crystals of [(CH₃)₄N]₂[CuCl₄] suitable for X-ray determination.

Refinement  

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. H atoms were included in idealized geometries and allowed to rotate to minimize their electron-density contribution with C—H = 0.98 Å and U _iso(H) = 1.5U _eq(C). The crystal used was found to be twinned through a 180° rotation about the reciprocal a axis with a twin component ratio of 0.76:0.24 (matrix: [1.000 −0.003 0.004 0.001 −1.000 −0.003 −0.093 0.005 −1.000]) . The diffraction data were integrated routinely applying this matrix and were scaled for absorption effects using TWINABS (Krause et al., 2015 ▸). In the final model, incorporation of the twinned data did not significantly alter the model, thus the final model was refined using the majority component data.

Table 2. Experimental details.

Crystal data
Chemical formula	(C4H12N)2[CuCl4]
M r	353.63
Crystal system, space group	Monoclinic, P21/n
Temperature (K)	120
a, b, c (Å)	8.9901 (5), 12.0059 (7), 14.9570 (9)
β (°)	91.719 (3)
V (Å3)	1613.65 (16)
Z	4
Radiation type	Mo Kα
μ (mm−1)	1.99
Crystal size (mm)	0.15 × 0.12 × 0.11
Data collection
Diffractometer	Bruker APEXII
Absorption correction	Multi-scan (TWINABS; Krause et al., 2015 ▸)
T min, T max	0.659, 0.746
No. of measured, independent and observed [I > 2σ(I)] reflections	7842, 4019, 2862
R int	0.057
(sin θ/λ)max (Å−1)	0.669
Refinement
R[F 2 > 2σ(F 2)], wR(F 2), S	0.066, 0.141, 1.12
No. of reflections	4019
No. of parameters	144
H-atom treatment	H-atom parameters constrained
Δρmax, Δρmin (e Å−3)	1.16, −1.03

Computer programs: APEX3 and SAINT (Bruker, 2015 ▸), SHELXT (Sheldrick, 2015a ▸), SHELXL2014 (Sheldrick, 2015b ▸), XP in SHELXTL (Sheldrick, 2008 ▸) and publCIF (Westrip, 2010 ▸).

Supplementary Material

CCDC reference: 1531866

Additional supporting information: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Crystal data

(C4H12N)2[CuCl4]	F(000) = 732
Mr = 353.63	Dx = 1.456 Mg m−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 8.9901 (5) Å	Cell parameters from 6598 reflections
b = 12.0059 (7) Å	θ = 2.6–24.7°
c = 14.9570 (9) Å	µ = 1.99 mm−1
β = 91.719 (3)°	T = 120 K
V = 1613.65 (16) Å3	Block, pale green
Z = 4	0.15 × 0.12 × 0.11 mm

Data collection

Bruker APEXII diffractometer	4019 independent reflections
Radiation source: fine-focus sealed tube	2862 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.057
Detector resolution: 8.33 pixels mm-1	θmax = 28.4°, θmin = 2.2°
combination of ω and φ–scans	h = −12→12
Absorption correction: multi-scan (TWINABS; Krause et al., 2015)	k = −16→16
Tmin = 0.659, Tmax = 0.746	l = 0→19
7842 measured reflections

Refinement

Refinement on F2	Primary atom site location: real-space vector search
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.066	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.141	H-atom parameters constrained
S = 1.12	w = 1/[σ2(Fo2) + 15.8242P] where P = (Fo2 + 2Fc2)/3
4019 reflections	(Δ/σ)max < 0.001
144 parameters	Δρmax = 1.16 e Å−3
0 restraints	Δρmin = −1.03 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Cu1	0.77037 (7)	0.71890 (6)	0.60734 (5)	0.01762 (17)
Cl1	0.78370 (15)	0.53786 (11)	0.64164 (10)	0.0211 (3)
Cl2	0.79189 (17)	0.81507 (13)	0.47896 (10)	0.0275 (3)
Cl3	0.97801 (15)	0.77628 (13)	0.67958 (10)	0.0267 (3)
Cl4	0.52836 (16)	0.74708 (14)	0.62755 (13)	0.0363 (4)
N1	0.2548 (5)	0.4839 (4)	0.6659 (3)	0.0183 (10)
C1	0.1601 (7)	0.3893 (5)	0.6925 (5)	0.0322 (15)
H1A	0.0671	0.4177	0.7162	0.048*
H1B	0.2128	0.3452	0.7386	0.048*
H1C	0.1378	0.3422	0.6403	0.048*
C2	0.1815 (7)	0.5491 (6)	0.5923 (4)	0.0328 (15)
H2A	0.0840	0.5750	0.6113	0.049*
H2B	0.1685	0.5017	0.5392	0.049*
H2C	0.2436	0.6133	0.5779	0.049*
C3	0.2801 (7)	0.5574 (6)	0.7446 (5)	0.0344 (16)
H3A	0.1846	0.5868	0.7639	0.052*
H3B	0.3451	0.6192	0.7284	0.052*
H3C	0.3273	0.5146	0.7935	0.052*
C4	0.4008 (6)	0.4411 (6)	0.6347 (5)	0.0296 (14)
H4A	0.4516	0.4002	0.6834	0.044*
H4B	0.4629	0.5038	0.6167	0.044*
H4C	0.3836	0.3912	0.5836	0.044*
N2	0.7505 (5)	0.1309 (4)	0.5840 (3)	0.0198 (10)
C5	0.7809 (7)	0.1175 (6)	0.4871 (4)	0.0279 (14)
H5A	0.7882	0.0381	0.4727	0.042*
H5B	0.8748	0.1545	0.4738	0.042*
H5C	0.6998	0.1511	0.4512	0.042*
C6	0.6058 (7)	0.0788 (6)	0.6059 (5)	0.0334 (16)
H6A	0.6112	−0.0018	0.5957	0.050*
H6B	0.5264	0.1106	0.5675	0.050*
H6C	0.5846	0.0931	0.6687	0.050*
C7	0.7444 (8)	0.2520 (5)	0.6048 (5)	0.0347 (16)
H7A	0.7225	0.2622	0.6681	0.052*
H7B	0.6661	0.2872	0.5676	0.052*
H7C	0.8405	0.2863	0.5925	0.052*
C8	0.8722 (7)	0.0776 (6)	0.6381 (4)	0.0304 (15)
H8A	0.8733	−0.0026	0.6260	0.046*
H8B	0.8558	0.0901	0.7018	0.046*
H8C	0.9678	0.1102	0.6222	0.046*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
Cu1	0.0169 (3)	0.0172 (3)	0.0188 (3)	0.0000 (3)	0.0018 (2)	0.0003 (3)
Cl1	0.0216 (7)	0.0157 (6)	0.0261 (7)	0.0009 (5)	0.0031 (5)	0.0006 (5)
Cl2	0.0355 (8)	0.0277 (8)	0.0195 (7)	−0.0040 (6)	0.0024 (6)	0.0043 (6)
Cl3	0.0227 (7)	0.0268 (8)	0.0304 (8)	−0.0034 (6)	−0.0019 (6)	−0.0028 (6)
Cl4	0.0169 (7)	0.0303 (8)	0.0621 (12)	0.0049 (6)	0.0097 (7)	0.0129 (8)
N1	0.014 (2)	0.018 (2)	0.022 (3)	0.0001 (18)	−0.0003 (18)	0.0018 (19)
C1	0.028 (3)	0.022 (3)	0.047 (4)	−0.010 (3)	0.012 (3)	−0.005 (3)
C2	0.030 (3)	0.048 (4)	0.020 (3)	0.013 (3)	−0.004 (3)	0.007 (3)
C3	0.038 (4)	0.037 (4)	0.028 (4)	−0.016 (3)	−0.001 (3)	−0.001 (3)
C4	0.020 (3)	0.030 (4)	0.038 (4)	0.006 (3)	0.008 (3)	0.007 (3)
N2	0.020 (2)	0.020 (2)	0.019 (3)	0.0022 (19)	0.0043 (19)	0.0018 (19)
C5	0.036 (4)	0.031 (3)	0.016 (3)	0.009 (3)	0.002 (3)	0.001 (3)
C6	0.021 (3)	0.031 (4)	0.048 (4)	−0.006 (3)	0.007 (3)	0.005 (3)
C7	0.051 (4)	0.022 (3)	0.032 (4)	0.001 (3)	0.009 (3)	−0.002 (3)
C8	0.025 (3)	0.043 (4)	0.023 (3)	0.009 (3)	0.001 (2)	0.010 (3)

Geometric parameters (Å, º)

Cu1—Cl4	2.2313 (15)	C4—H4B	0.9800
Cu1—Cl1	2.2357 (15)	C4—H4C	0.9800
Cu1—Cl3	2.2374 (15)	N2—C8	1.486 (7)
Cu1—Cl2	2.2538 (16)	N2—C7	1.488 (8)
N1—C1	1.481 (7)	N2—C6	1.488 (7)
N1—C3	1.483 (8)	N2—C5	1.491 (7)
N1—C2	1.488 (7)	C5—H5A	0.9800
N1—C4	1.498 (7)	C5—H5B	0.9800
C1—H1A	0.9800	C5—H5C	0.9800
C1—H1B	0.9800	C6—H6A	0.9800
C1—H1C	0.9800	C6—H6B	0.9800
C2—H2A	0.9800	C6—H6C	0.9800
C2—H2B	0.9800	C7—H7A	0.9800
C2—H2C	0.9800	C7—H7B	0.9800
C3—H3A	0.9800	C7—H7C	0.9800
C3—H3B	0.9800	C8—H8A	0.9800
C3—H3C	0.9800	C8—H8B	0.9800
C4—H4A	0.9800	C8—H8C	0.9800
Cl4—Cu1—Cl1	99.33 (6)	N1—C4—H4C	109.5
Cl4—Cu1—Cl3	133.69 (7)	H4A—C4—H4C	109.5
Cl1—Cu1—Cl3	98.64 (6)	H4B—C4—H4C	109.5
Cl4—Cu1—Cl2	98.44 (7)	C8—N2—C7	109.7 (5)
Cl1—Cu1—Cl2	133.48 (6)	C8—N2—C6	109.5 (5)
Cl3—Cu1—Cl2	99.32 (6)	C7—N2—C6	109.1 (5)
C1—N1—C3	108.6 (5)	C8—N2—C5	109.2 (4)
C1—N1—C2	110.9 (5)	C7—N2—C5	108.5 (5)
C3—N1—C2	109.2 (5)	C6—N2—C5	110.8 (5)
C1—N1—C4	109.7 (5)	N2—C5—H5A	109.5
C3—N1—C4	109.6 (5)	N2—C5—H5B	109.5
C2—N1—C4	108.9 (5)	H5A—C5—H5B	109.5
N1—C1—H1A	109.5	N2—C5—H5C	109.5
N1—C1—H1B	109.5	H5A—C5—H5C	109.5
H1A—C1—H1B	109.5	H5B—C5—H5C	109.5
N1—C1—H1C	109.5	N2—C6—H6A	109.5
H1A—C1—H1C	109.5	N2—C6—H6B	109.5
H1B—C1—H1C	109.5	H6A—C6—H6B	109.5
N1—C2—H2A	109.5	N2—C6—H6C	109.5
N1—C2—H2B	109.5	H6A—C6—H6C	109.5
H2A—C2—H2B	109.5	H6B—C6—H6C	109.5
N1—C2—H2C	109.5	N2—C7—H7A	109.5
H2A—C2—H2C	109.5	N2—C7—H7B	109.5
H2B—C2—H2C	109.5	H7A—C7—H7B	109.5
N1—C3—H3A	109.5	N2—C7—H7C	109.5
N1—C3—H3B	109.5	H7A—C7—H7C	109.5
H3A—C3—H3B	109.5	H7B—C7—H7C	109.5
N1—C3—H3C	109.5	N2—C8—H8A	109.5
H3A—C3—H3C	109.5	N2—C8—H8B	109.5
H3B—C3—H3C	109.5	H8A—C8—H8B	109.5
N1—C4—H4A	109.5	N2—C8—H8C	109.5
N1—C4—H4B	109.5	H8A—C8—H8C	109.5
H4A—C4—H4B	109.5	H8B—C8—H8C	109.5

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C1—H1C···Cl2i	0.98	2.69	3.585 (7)	153
C2—H2A···Cl1ii	0.98	2.79	3.675 (7)	151
C2—H2A···Cl3ii	0.98	2.80	3.555 (7)	134
C2—H2B···Cl1i	0.98	2.79	3.674 (7)	150
C3—H3B···Cl4	0.98	2.74	3.670 (7)	159
C4—H4A···Cl3iii	0.98	2.59	3.555 (7)	166
C5—H5A···Cl2iv	0.98	2.68	3.635 (7)	165
C5—H5B···Cl3v	0.98	2.81	3.587 (6)	137
C5—H5C···Cl4i	0.98	2.63	3.610 (6)	173
C8—H8B···Cl1iii	0.98	2.76	3.650 (6)	151
C8—H8C···Cl2v	0.98	2.82	3.763 (7)	162

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x−1, y, z; (iii) −x+3/2, y−1/2, −z+3/2; (iv) x, y−1, z; (v) −x+2, −y+1, −z+1.