Crystal structure of bis­(N,N,N′,N′-tetra­methyl­guanidinium) tetra­chlorido­cuprate(II)

Ndiaye, M.; Samb, A.; Diop, L.; Maris, T.

doi:10.1107/S2056989016010161

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Volume 72| Part 7| July 2016| Pages 1047-1049

https://doi.org/10.1107/S2056989016010161

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Crystal structure of bis(N,N,N′,N′-tetramethylguanidinium) tetrachloridocuprate(II)

Mamadou Ndiaye,^a Abdoulaye Samb,^a Libasse Diop ^b ^* and Thierry Maris ^c

^aLaboratoire des Produits Naturels, Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Senegal, ^bLaboratoire de Chimie Minérale et Analytique, Département de Chimie, Faculté des Sciences et Techniques, Université Cheikh Anta Diop, Dakar, Senegal, and ^cDépartement de Chimie, Université de Montréal, 2900 Boulevard Édouard-Montpetit, Montréal, Québec, H3C 3J7, Canada
^*Correspondence e-mail: dlibasse@gmail.com

Edited by M. Weil, Vienna University of Technology, Austria (Received 13 June 2016; accepted 21 June 2016; online 24 June 2016)

In the structure of the title salt, (C₅H₁₄N₃)₂[CuCl₄], the Cu^II atom in the anion lies on a twofold rotation axis. The tetrachloridocuprate(II) anion adopts a flattened tetrahedral coordination environment and interacts electrostatically with the tetramethylguanidinium cation. The crystal packing is additionally consolidated through N—H⋯Cl and C—H⋯Cl hydrogen bonds, resulting in a three-dimensional network structure.

Keywords: crystal structure; organic–inorganic hybrid salt; tetramethylguanidinium; tetrachloridocuprate(II); τ₄ index.

CCDC reference: 1486986

1. Chemical context

The title compound belongs to the series of hybrid organic–inorganic materials of general formula A₂[MX₄] where A is an organic cation, M a divalent transition metal and X a halide. The copper representatives of these families have been extensively studied for their magnetic, dielectric and fluorescent properties in relation to their solid-state structures (Halvorson et al., 1990 ). Recent studies include examination of polymorphism in relation to electrostatic properties (Awwadi & Haddad, 2012 ) or thermochroism (Aldrich et al., 2016 ), sometimes in relation to phase transitions (Kelley et al., 2015 ).

Following our report on the crystal structure of bis-tetramethylguanidinium trichloridocadmate (Ndiaye et al., 2016 ), we have investigated the interactions between tetramethylguanidine and CuCl₂·2H₂O which has yielded the title salt, (C₅H₁₄N₃)₂[CuCl₄], (I).

2. Structural commentary

The asymmetric unit of (I) contains a complete N,N,N′,N′-tetramethylguanidinium cation and half of a [CuCl₄]²⁻ anion held together by an N—H⋯Cl hydrogen bond (Fig. 1). In the anion, the Cu—Cl distances range from 2.2396 (4) Å to 2.2557 (4) Å. They are shorter than those usually found in tetrachloridocuprate(II) anions with a square-planar configuration (Guo et al., 2015 ). The distortion of the flattened tetrachloridocuprate(II) anion in (I) from the ideal tetrahedral configuration can be asserted by the values of the two trans Cl—Cu—Cl angles, 135.62 (3)° and 133.31 (3)°. These two angles can also be used to calculate the τ₄ geometry index developed by Yang et al. (2007 ) for complexes with coordination number four to quantify such a distortion. The τ₄ parameter is defined as [360 - (α+β)] / 141 where α and β are the two largest Cl—Cu—Cl angles. A τ₄ index value of 1 corresponds to an ideal tetrahedral configuration while a value of 0 is for a perfect square-planar configuration. Here the value obtained (0.65) indicates a `see-saw' (bisphenoidal) configuration with point group symmetry 2.

Figure 1
The structures of the molecular entities in (I)

, drawn with displacement parameters at the 50% probability level. The N—H⋯Cl hydrogen bond is indicated by a dashed line. [Symmetry code: (i) −x + 1, y, −z + $[{3\over 2}]$ .]

In the organic cation, the C—N distances in the central CN₃ unit [1.332 (2), 1.335 (2) and 1.342 (2) Å] are consistent with a partial double-bond character and a positive charge delocalization, as usually found in structures involving tetramethylguanidinium cations. The central core of the cation has an almost planar–trigonal geometry, as reflected by the values for the three N—C—N angles close to 120° and the r.m.s deviation from the least-squares plane calculated for atoms C1, N1, N2 and N3 that is only 0.0006 Å. The dimethylammonium groups are twisted by 29.38 (16)° (C2, C3) and 25.08 (16)° (C4, C5) with respect to this plane.

3. Supramolecular features

Anions and cations are connected through electrostatic interactions and via classical N—H⋯Cl hydrogen bonds involving atom Cl1 whereby only one of the H atoms of the amine group is involved; the remaining H atom has no acceptor atom (Fig. 1, Table 1). In addition, each Cl atom of the anion is engaged in three C—H⋯Cl hydrogen bonds, leading to the formation of a three-dimensional network structure (Fig. 2, Table 1).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C4—H4B⋯Cl2ⁱ	0.95 (2)	2.77 (2)	3.5902 (19)	145.3 (18)
C2—H2C⋯Cl1ⁱⁱ	0.98 (3)	2.90 (3)	3.745 (2)	144.5 (18)
C2—H2D⋯Cl1ⁱⁱⁱ	0.91 (2)	2.91 (2)	3.818 (2)	173.3 (19)
C3—H3B⋯Cl2^iv	0.99 (3)	2.82 (3)	3.793 (2)	168 (2)
C5—H5C⋯Cl2^v	0.93 (3)	2.80 (3)	3.5992 (18)	144.9 (19)
C2—H2E⋯Cl2^vi	0.96 (3)	2.85 (3)	3.6491 (18)	140.5 (19)
N2—H2B⋯Cl1	0.86 (3)	2.53 (3)	3.3417 (16)	157 (2)
Symmetry codes: (i) $[-x+1, y, -z+{\script{3\over 2}}]$ ; (ii) $[-x+{\script{1\over 2}}, -y+{\script{1\over 2}}, -z+1]$ ; (iii) $[x, -y+1, z-{\script{1\over 2}}]$ ; (iv) $[-x+{\script{1\over 2}}, -y+{\script{3\over 2}}, -z+1]$ ; (v) $[-x+1, y-1, -z+{\script{3\over 2}}]$ ; (vi) $[x-{\script{1\over 2}}, y-{\script{1\over 2}}, z-1]$ .

Figure 2
Packing diagram of (I)

viewed along [001].

4. Database survey

A search in the Cambridge Structural Database (Version 5.37 with two updates; Groom et al., 2016 ) for isolated tetrachloridocuprate(II) anions without disorder returned 342 hits for a total of 389 fragments. The configurations of these fragments were analysed using the τ₄ index as described above. Around 60 of these (15%) have a τ₄ index value less than 0.1, including 29 that have a τ₄ index of 0 (ideal square-planar configuration). Only four were found to have a configuration close to the ideal tetrahedral one with a τ₄ index value larger than 0.9. A large number of fragments (72%) has a geometry index τ₄ value in the 0.6–0.8 range and feature a bisphenoidal configuration as found for (I). An analysis with the modified version of the τ₄ index [τ₄′, as defined by Okuniewski et al. (2015 )] gives a similar distribution with only minor variation.

The title compound is isostructural with bis(N,N,N′,N′-tetramethylguanidinium) tetrabromidonickelate(II) (Jones & Thonnessen, 2006 ) and shows similarities in terms of the space-group and cell parameters with tetramethylguanidinium bisulfite (Heldebrant et al., 2009 ).

5. Synthesis and crystallization

Yellowish-green crystals were obtained by mixing in stoichiometric amounts tetramethylguanidine with CuCl₂·2H₂O in ethanol.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. All hydrogen atoms were located from a Fourier difference map and were refined freely.

Table 2
Experimental details

Crystal data
Chemical formula	(C₅H₁₄N₃)₂[CuCl₄]
M_r	437.72
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	100
a, b, c (Å)	18.9274 (5), 8.2441 (2), 14.8654 (4)
β (°)	124.165 (1)
V (Å³)	1919.28 (9)
Z	4
Radiation type	Ga Kα, λ = 1.34139 Å
μ (mm⁻¹)	9.51
Crystal size (mm)	0.16 × 0.10 × 0.06

Data collection
Diffractometer	Bruker Venture Metaljet
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 )
T_min, T_max	0.449, 0.752
No. of measured, independent and observed [I > 2σ(I)] reflections	14222, 2208, 2178
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.650

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.028, 0.071, 1.11
No. of reflections	2208
No. of parameters	152
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.84, −0.35
Computer programs: APEX2 and SAINT (Bruker, 2014 ), SHELXT (Sheldrick, 2015a ), SHELXL2014 (Sheldrick, 2015b ), OLEX2 (Dolomanov et al., 2009 ), Mercury (Macrae et al., 2008 ) and publCIF (Westrip, 2010 ).

Supporting information

CCDC reference: 1486986

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989016010161/wm5303sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989016010161/wm5303Isup2.hkl

checkCIF report

Computing details top

Data collection: APEX2 (Bruker, 2014); cell refinement: SAINT (Bruker, 2014); data reduction: SAINT (Bruker, 2014); program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2014 (Sheldrick, 2015b); molecular graphics: OLEX2 (Dolomanov et al., 2009) and Mercury (Macrae et al., 2008); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009) and publCIF (Westrip, 2010).

Bis(N,N,N',N'-tetramethylguanidinium) tetrachloridocuprate(II) top

Crystal data top

(C₅H₁₄N₃)₂[CuCl₄]	F(000) = 908
M_r = 437.72	D_x = 1.515 Mg m⁻³
Monoclinic, C2/c	Ga Kα radiation, λ = 1.34139 Å
a = 18.9274 (5) Å	Cell parameters from 9968 reflections
b = 8.2441 (2) Å	θ = 4.9–60.7°
c = 14.8654 (4) Å	µ = 9.51 mm⁻¹
β = 124.165 (1)°	T = 100 K
V = 1919.28 (9) Å³	Block, clear yellowish green
Z = 4	0.16 × 0.10 × 0.06 mm

Data collection top

Bruker Venture Metaljet diffractometer	2208 independent reflections
Radiation source: Metal Jet, Gallium Liquid Metal Jet Source	2178 reflections with I > 2σ(I)
Helios MX Mirror Optics monochromator	R_int = 0.036
Detector resolution: 10.24 pixels mm^-1	θ_max = 60.7°, θ_min = 4.9°
ω and φ scans	h = −24→24
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	k = −10→10
T_min = 0.449, T_max = 0.752	l = −16→19
14222 measured reflections

Refinement top

Refinement on F²	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Hydrogen site location: difference Fourier map
R[F² > 2σ(F²)] = 0.028	All H-atom parameters refined
wR(F²) = 0.071	w = 1/[σ²(F_o²) + (0.0315P)² + 2.7253P] where P = (F_o² + 2F_c²)/3
S = 1.11	(Δ/σ)_max = 0.001
2208 reflections	Δρ_max = 0.84 e Å⁻³
152 parameters	Δρ_min = −0.35 e Å⁻³
0 restraints

Special details top

Experimental. X-ray crystallographic data for I were collected from a single crystal sample, which was mounted on a loop fiber. Data were collected using a Bruker Venture diffractometer equipped with a Photon 100 CMOS Detector, a Helios MX optics and a Kappa goniometer. The crystal-to-detector distance was 4.0 cm, and the data collection was carried out in 1024 x 1024 pixel mode.

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 (Å²) top

	x	y	z	U_iso*/U_eq
N1	0.18244 (9)	0.33219 (19)	0.30111 (11)	0.0202 (3)
N2	0.24981 (11)	0.5129 (2)	0.44495 (13)	0.0277 (4)
N3	0.32977 (9)	0.32615 (17)	0.42260 (11)	0.0164 (3)
C1	0.25428 (10)	0.3903 (2)	0.38962 (13)	0.0173 (3)
C2	0.17917 (12)	0.2676 (2)	0.20725 (14)	0.0215 (3)
C3	0.09950 (12)	0.3500 (3)	0.28512 (17)	0.0314 (4)
C4	0.40978 (11)	0.4132 (2)	0.49381 (15)	0.0235 (4)
C5	0.33922 (12)	0.1564 (2)	0.40153 (15)	0.0208 (3)
Cu1	0.5000	0.71829 (4)	0.7500	0.01698 (11)
Cl1	0.37443 (3)	0.61496 (7)	0.70754 (4)	0.03106 (13)
Cl2	0.54835 (3)	0.82595 (5)	0.91317 (3)	0.02989 (13)
H4A	0.4363 (15)	0.380 (3)	0.569 (2)	0.030 (6)*
H5A	0.2894 (16)	0.099 (3)	0.3780 (19)	0.029 (6)*
H4B	0.4000 (14)	0.526 (3)	0.4851 (18)	0.024 (5)*
H2C	0.1702 (16)	0.150 (3)	0.2047 (19)	0.030 (6)*
H2D	0.2285 (15)	0.291 (3)	0.2132 (18)	0.022 (5)*
H3A	0.0693 (18)	0.248 (4)	0.260 (2)	0.040 (7)*
H2A	0.2102 (18)	0.568 (4)	0.418 (2)	0.037 (7)*
H3B	0.0655 (19)	0.432 (4)	0.228 (2)	0.050 (8)*
H5B	0.3539 (15)	0.147 (3)	0.349 (2)	0.028 (6)*
H5C	0.3857 (16)	0.111 (3)	0.465 (2)	0.028 (6)*
H2E	0.1316 (16)	0.319 (3)	0.143 (2)	0.028 (6)*
H4C	0.4454 (16)	0.389 (3)	0.468 (2)	0.033 (6)*
H2B	0.2934 (17)	0.536 (3)	0.509 (2)	0.035 (6)*
H3C	0.1050 (17)	0.373 (3)	0.352 (2)	0.040 (7)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0176 (6)	0.0242 (7)	0.0155 (6)	0.0023 (6)	0.0072 (5)	−0.0054 (6)
N2	0.0225 (7)	0.0289 (8)	0.0186 (7)	0.0092 (7)	0.0036 (6)	−0.0097 (6)
N3	0.0174 (6)	0.0135 (6)	0.0163 (6)	−0.0003 (5)	0.0083 (5)	−0.0008 (5)
C1	0.0196 (7)	0.0167 (7)	0.0130 (7)	0.0028 (6)	0.0075 (6)	−0.0001 (6)
C2	0.0273 (9)	0.0215 (9)	0.0134 (8)	−0.0026 (7)	0.0102 (7)	−0.0044 (6)
C3	0.0182 (8)	0.0432 (12)	0.0264 (9)	0.0061 (8)	0.0086 (7)	−0.0100 (9)
C4	0.0194 (8)	0.0228 (9)	0.0223 (8)	−0.0040 (7)	0.0079 (7)	−0.0029 (7)
C5	0.0234 (8)	0.0132 (7)	0.0253 (9)	0.0028 (7)	0.0135 (7)	0.0000 (7)
Cu1	0.01872 (18)	0.01483 (18)	0.01209 (17)	0.000	0.00542 (14)	0.000
Cl1	0.0201 (2)	0.0510 (3)	0.0243 (2)	−0.00970 (18)	0.01383 (17)	−0.01532 (19)
Cl2	0.0501 (3)	0.0180 (2)	0.01273 (19)	−0.00519 (18)	0.01222 (18)	−0.00224 (14)

Geometric parameters (Å, º) top

N1—C1	1.342 (2)	C3—H3B	0.99 (3)
N1—C2	1.462 (2)	C3—H3C	0.96 (3)
N1—C3	1.457 (2)	C4—H4A	0.97 (3)
N2—C1	1.335 (2)	C4—H4B	0.95 (2)
N2—H2A	0.77 (3)	C4—H4C	0.97 (3)
N2—H2B	0.86 (3)	C5—H5A	0.93 (3)
N3—C1	1.332 (2)	C5—H5B	0.96 (2)
N3—C4	1.459 (2)	C5—H5C	0.93 (3)
N3—C5	1.467 (2)	Cu1—Cl1ⁱ	2.2557 (4)
C2—H2C	0.98 (3)	Cu1—Cl1	2.2557 (4)
C2—H2D	0.91 (2)	Cu1—Cl2ⁱ	2.2396 (4)
C2—H2E	0.96 (3)	Cu1—Cl2	2.2396 (4)
C3—H3A	0.96 (3)

C1—N1—C2	122.85 (14)	H3A—C3—H3B	108 (2)
C1—N1—C3	121.97 (14)	H3A—C3—H3C	105 (2)
C3—N1—C2	114.63 (14)	H3B—C3—H3C	113 (2)
C1—N2—H2A	120 (2)	N3—C4—H4A	110.4 (14)
C1—N2—H2B	119.9 (17)	N3—C4—H4B	110.0 (14)
H2A—N2—H2B	120 (3)	N3—C4—H4C	106.3 (15)
C1—N3—C4	122.24 (14)	H4A—C4—H4B	112 (2)
C1—N3—C5	122.31 (14)	H4A—C4—H4C	112 (2)
C4—N3—C5	115.01 (14)	H4B—C4—H4C	106 (2)
N2—C1—N1	119.64 (15)	N3—C5—H5A	110.2 (15)
N3—C1—N1	120.38 (15)	N3—C5—H5B	111.8 (15)
N3—C1—N2	119.98 (15)	N3—C5—H5C	109.2 (15)
N1—C2—H2C	108.1 (14)	H5A—C5—H5B	110 (2)
N1—C2—H2D	109.8 (14)	H5A—C5—H5C	111 (2)
N1—C2—H2E	107.2 (15)	H5B—C5—H5C	104 (2)
H2C—C2—H2D	111 (2)	Cl1—Cu1—Cl1ⁱ	135.62 (3)
H2C—C2—H2E	110 (2)	Cl2—Cu1—Cl1	100.265 (17)
H2D—C2—H2E	110 (2)	Cl2ⁱ—Cu1—Cl1	96.958 (19)
N1—C3—H3A	109.1 (16)	Cl2—Cu1—Cl1ⁱ	96.959 (19)
N1—C3—H3B	109.1 (17)	Cl2ⁱ—Cu1—Cl1ⁱ	100.264 (17)
N1—C3—H3C	111.8 (16)	Cl2—Cu1—Cl2ⁱ	133.31 (3)

C2—N1—C1—N2	146.94 (18)	C4—N3—C1—N1	159.80 (16)
C2—N1—C1—N3	−33.3 (3)	C4—N3—C1—N2	−20.4 (2)
C3—N1—C1—N2	−24.1 (3)	C5—N3—C1—N1	−28.2 (2)
C3—N1—C1—N3	155.67 (18)	C5—N3—C1—N2	151.61 (17)

Symmetry code: (i) −x+1, y, −z+3/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C4—H4B···Cl2ⁱ	0.95 (2)	2.77 (2)	3.5902 (19)	145.3 (18)
C2—H2C···Cl1ⁱⁱ	0.98 (3)	2.90 (3)	3.745 (2)	144.5 (18)
C2—H2D···Cl1ⁱⁱⁱ	0.91 (2)	2.91 (2)	3.818 (2)	173.3 (19)
C3—H3B···Cl2^iv	0.99 (3)	2.82 (3)	3.793 (2)	168 (2)
C5—H5C···Cl2^v	0.93 (3)	2.80 (3)	3.5992 (18)	144.9 (19)
C2—H2E···Cl2^vi	0.96 (3)	2.85 (3)	3.6491 (18)	140.5 (19)
N2—H2B···Cl1	0.86 (3)	2.53 (3)	3.3417 (16)	157 (2)

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

Acknowledgements

The authors acknowledge the Cheikh Anta Diop University of Dakar (Sénégal), the Canada Foundation for Innovation and the Université de Montréal for financial support.

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