Bis(2-methyl­pyridinium) tetra­chlorido­cuprate(II): synthesis, structure and Hirshfeld surface analysis

Mehmood, T.; Bhosale, R.S.; Reddy, J.P.

doi:10.1107/S2056989021006277

research communications

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Volume 77| Part 7| July 2021| Pages 726-729

https://doi.org/10.1107/S2056989021006277

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Bis(2-methylpyridinium) tetrachloridocuprate(II): synthesis, structure and Hirshfeld surface analysis

Tahir Mehmood,^a Rajesh S. Bhosale ^a ^* and J. Prakasha Reddy ^a ^*

^aDepartment of Chemistry, School of Sciences, Indrashil University, Rajpur, Gujarat, 382740, India
^*Correspondence e-mail: rajeshbhosale24@gmail.com, j.prakashareddy@gmail.com

Edited by G. Diaz de Delgado, Universidad de Los Andes, Venezuela (Received 21 December 2020; accepted 17 June 2021; online 25 June 2021)

The title compound, (C₆H₈N)₂[CuCl₄], crystallizes in the monoclinic space group I2/c. The coordination around the copper atom is a distorted tetrahedron. The 2-methylpyridinium ion (C₆H₈N⁺) interacts with the tetrachlorocuprate anion through N—H⋯Cl and C—H(phenyl)⋯Cl contacts, forming a hydrogen-bonded layer-like structure. The supramolecular structure is further stabilized by C—H(methyl)⋯Cl interactions between the layers.

Keywords: 2-picoline complex; inorganic supramolecular chemistry; crystal structure; hydrogen bonding.

CCDC reference: 2090586

1. Chemical context

Supramolecular organic and inorganic chemistry have been studied both from the fundamental as well as the application point of view, which is evident from the literature (Ziach et al., 2018 ; Thorat et al., 2013 ; Burslem et al., 2016 ). With the surge in the number of compounds reported, potential applications of supramolecular inorganic materials in energy storage, separation, catalysis, sensors, molecular magnets, optoelectronic materials, etc., have attracted greater attention in recent years (Mueller et al., 2006 ; Wan et al., 2006 ; Férey et al., 2003 ; James, 2003 ; Eddaoudi et al., 2002 ; Ruben et al., 2005 , Kitagawa et al., 2004 , Stavila et al., 2014 ). Because of the divergent combination of ligands and metal salts, an enormous number of structural architectures with different sizes and shapes could be constructed (Moulton & Zaworotko, 2001 ). The special characteristics and features such as ease of synthesis of the material, geometrically well-defined structures, exceptional tunability, post-synthetic modification, along with robustness of the material resulting from strong directional bonding, produce new opportunities and offer a unique platform amenable to the synthesis of more and more functional solids. For example, Adams et al. (2005 ) reported the synthesis of coordination compounds using a new synthetic route involving a thermal dehydrochlorination reaction in crystals of a pyridinium chlorometallate bicomponent system, i.e., anionic metal complexes and organic cations.

As part of ongoing studies in our group (PrakashaReddy & Pedireddi, 2007 ; Reddy et al., 2014 ), the synthesis of coordination complexes using pyridine ligands has been reported. Hence, we further extended our studies to utilize the pyridinium ligand and to study in situ the single-crystal-to-single-crystal transition (SCSCT) to investigate the reaction mechanism. In our endeavours to synthesize new functional solids, using a transition-metal anion and a pyridinium cation, we have chosen the CuCl₂ and 2-methylpyridinium salt complex. Herein, we report the synthesis and crystal structure of a bis(2-methylpyridinium) tetrachlorocuprate coordination complex.

2. Structural commentary

The title complex crystallizes in the monoclinic space group I2/c. Since the Cu²⁺ cation occupies a special position, the asymmetric unit consists of a 2-methylpyridinium cation, [2-Me(Py)H]⁺, and half of a tetrachlorocuprate(II) anion, [CuCl₄]^2–. The molecular structure of the complex along with the atom-labelling scheme is shown in Fig. 1. Each copper center is four-coordinated by chlorine anions and adopts a distorted tetrahedral geometry. Structural analysis shows that the Cl—Cu—Cl angles vary from 98.55 (2) to 137.4 (3)° with four angles smaller and two larger than the standard tetrahedral angle. A plausible reason for a larger deviation from the standard 109.5° might be due to the N—H⋯Cl and C—H⋯Cl interactions. A similar marked deviation from the standard tetrahedral angle has been previously observed by other research groups (Wyrzykowski et al., 2011 ; Jasrotia et al., 2018 ). The Cu—Cl bond lengths [Cu1—Cl1 = 2.250 (1) Å, Cu1—Cl2 = 2.249 (1) Å] agree well with those reported for other structures (Marsh et al., 1982 ; Dodds et al., 2018 ; Molano et al., 2020 ; Reddy, 2020 ). The intramolecular C_ar—C_ar bond lengths in the [2-Me(Py)H]⁺ fall in the range 1.370 (3)–1.395 (3) Å. The N1—C2 and N1—C6 bond lengths are 1.350 (2) and 1.346 (2) Å, respectively.

Figure 1
The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 50% probability level. Hydrogen atoms are shown as small spheres of arbitrary size. [Symmetry code: (i) 1 − x, y, $[{1\over 2}]$ − z.]

3. Supramolecular features and Hirshfeld surface analysis

In the crystal, complex molecules related by the twofold rotation axis are connected by pairs of N—H⋯Cl and C_ar—H⋯Cl interactions through a protonated N and an aromatic hydrogen attached to the carbon atom with the chloride ligand bonded to copper, forming a monomeric unit. These units interact with adjacent ones through C_ar—H⋯Cl hydrogen bonding (Table 1, Fig. 2). The N—H⋯Cl and C—H⋯Cl distances and associated bond angles lie within the ranges observed for other similar interactions reported in the literature (Adams et al., 2005; Vittaya et al., 2015 ; Wyrzykowski et al., 2011; Jasrotia et al., 2018). The supramolecular structure is further stabilized by C_methyl—H⋯Cl interactions involving hydrogens of the methyl group and chlorides bonded to copper, generating layers along the crystallographic b axis (Fig. 3).

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1⋯Cl1ⁱ	0.88	2.93	3.4297 (16)	118
N1—H1⋯Cl2ⁱ	0.88	2.41	3.2050 (16)	150
C6—H6⋯Cl1ⁱⁱ	0.95	2.62	3.453 (2)	147
C7—H7A⋯Cl2	0.98	2.92	3.850 (2)	159
C7—H7B⋯Cl2ⁱⁱⁱ	0.98	2.98	3.872 (2)	151
Symmetry codes: (i) ; (ii) $[x+{\script{1\over 2}}, y-{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (iii) .

Figure 2
The N—H⋯Cl and C—H⋯Cl interactions between cations and anions in the crystal structure of the title compound.

Figure 3
The crystal packing of the title compound viewed along the b axis with intermolecular contacts shown as dashed lines.

To further investigate the intermolecular interactions present in the title compound, a Hirshfeld surface analysis was performed and the two-dimensional fingerprint plots were generated with Crystal Explorer17 (Turner et al., 2017 ). The Hirshfeld surface mapped over d_norm and corresponding colours representing various interactions are shown in Fig. 4. The red points on the surface correspond to the N—H⋯Cl and C—H⋯Cl interactions. The two-dimensional fingerprint plots (McKinnon et al., 2007 ) are shown in Fig. 5. On the Hirshfeld surface, the largest contribution (53.1%) comes from the weak van der Waals H⋯H contacts. The interaction of d_norm on the two-dimensional fingerprint plot shows two spikes; each one corresponds to H⋯H (39%) and H⋯Cl/Cl⋯H (32.5%) respectively. The H⋯Cl interaction highlights the hydrogen bond between adjacent moieties in the crystal structure. The C⋯H/H⋯C (16.5%) interactions appear as two shoulders. These interactions play a crucial role in the overall stabilization of the crystal packing.

Figure 4
Hirshfeld surface mapped over d_norm highlighting the regions of N—H⋯Cl and C—H⋯Cl intermolecular contacts.

Figure 5
The full two-dimensional fingerprint plot for the organic cation in the title compound and those delineated into H⋯H (39%), Cl⋯H/H⋯Cl (32.5%) and C⋯H/H⋯C (16.5%) contacts.

4. Database survey

A search of the Cambridge Structural Database (CSD, Version 5.41, update of August 2020; Groom et al., 2016 ) revealed two related complexes containing 2-methylpyridinium: [2-methylpyridinium tetrachloroferrate(III)] (CCDC refcode WAYJEN; Wyrzykowski et al., 2011) and [bis(2-methyl-pyridinium) tetrachloro-zinc(II)] (CCDC refcode WIPCUW; Jasrotia et al., 2018). The molecular structures of both WAYJEN and WIPCUW display three-dimensional supramolecular networks arising from N—H⋯Cl and C—H⋯Cl interactions. In addition, the search also revealed a 2-methylpyridine and copper chloride complex: [dichloro-bis(2-methylpyridine)Cu(II)] (CCDC refcode CMPYCU01; Marsh et al., 1982) and [aqua-dichloro-bis(2-methylpyridine)Cu(II)] (CCDC refcode BIJWUM; Marsh et al., 1982) and a very recently published dichloridomethanolbis(2-methylpyridine)Cu(II) complex (Reddy, 2020). All of these structures display three-dimensional supramolecular networks stabilized by C—H⋯Cl and O—H⋯Cl interactions.

5. Synthesis and crystallization

Both 2-methylpyridine and anhydrous copper(II) chloride obtained from Aldrich were used for the reaction. Anhydrous copper(II) chloride (0.495 g, 0.005 mol) was dissolved in 10 ml of distilled water. To this solution, 2-methylpyridine (0.93 g, 0.01 mol) was added followed by addition of few drops of HCl (36%) and the resulting mixture was stirred for ∼30 min. at room temperature. The solution was then allowed to stand at room temperature for a few hours before being filtered and left at room temperature for crystallization. Block-shaped, pale-yellow-coloured crystals were obtained after 36 h.

6. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. H atoms were placed in calculated positions with C—H = 0.93–0.96 Å and N—H = 0.88 Å and refined as riding with fixed isotropic displacement parameters [U_iso(H) = 1.2–1.5U_eq(C, N)].

Table 2
Experimental details

Crystal data
Chemical formula	(C₆H₈N)₂[CuCl₄]
M_r	393.62
Crystal system, space group	Monoclinic, I2/c
Temperature (K)	120
a, b, c (Å)	15.2354 (8), 8.3683 (3), 12.8372 (6)
β (°)	99.205 (5)
V (Å³)	1615.60 (13)
Z	4
Radiation type	Mo Kα
μ (mm⁻¹)	2.00
Crystal size (mm)	0.32 × 0.27 × 0.25

Data collection
Diffractometer	Agilent Xcalibur, Sapphire3
Absorption correction	Analytical (CrysAlis PRO; Agilent, 2014 )
T_min, T_max	0.848, 0.965
No. of measured, independent and observed [I > 2σ(I)] reflections	24556, 2821, 2324
R_int	0.071
(sin θ/λ)_max (Å⁻¹)	0.758

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.081, 1.08
No. of reflections	2821
No. of parameters	88
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.58, −0.58
Computer programs: CrysAlis PRO (Agilent, 2014), SUPERFLIP (Palatinus & Chapuis, 2007 ; Palatinus & van der Lee, 2008 ; Palatinus et al., 2012 ), SHELXL (Sheldrick, 2015 ) and OLEX2 (Dolomanov et al., 2009 ).

Supporting information

CCDC reference: 2090586

Crystal structure: contains datablock I. DOI: https://doi.org/10.1107/S2056989021006277/dj2020sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S2056989021006277/dj2020Isup2.hkl

checkCIF report

Computing details top

Data collection: CrysAlis PRO (Agilent, 2014); cell refinement: CrysAlis PRO (Agilent, 2014); data reduction: CrysAlis PRO (Agilent, 2014); program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007; Palatinus & van der Lee, 2008; Palatinus et al., 2012); program(s) used to refine structure: SHELXL (Sheldrick, 2015); molecular graphics: OLEX2 (Dolomanov et al., 2009); software used to prepare material for publication: OLEX2 (Dolomanov et al., 2009).

Bis(2-methylpyridinium) tetrachloridocuprate(II) top

Crystal data top

(C₆H₈N)₂[CuCl₄]	F(000) = 796
M_r = 393.62	D_x = 1.618 Mg m⁻³
Monoclinic, I2/c	Mo Kα radiation, λ = 0.71073 Å
a = 15.2354 (8) Å	Cell parameters from 5462 reflections
b = 8.3683 (3) Å	θ = 2.9–32.5°
c = 12.8372 (6) Å	µ = 2.00 mm⁻¹
β = 99.205 (5)°	T = 120 K
V = 1615.60 (13) Å³	Blocks, pale yellow
Z = 4	0.32 × 0.27 × 0.25 mm

Data collection top

Agilent Xcalibur, Sapphire3 diffractometer	2324 reflections with I > 2σ(I)
Detector resolution: 16.1511 pixels mm^-1	R_int = 0.071
ω scans	θ_max = 32.6°, θ_min = 2.9°
Absorption correction: analytical (CrysAlisPro; Agilent, 2014)	h = −22→22
T_min = 0.848, T_max = 0.965	k = −11→12
24556 measured reflections	l = −19→19
2821 independent reflections

Refinement top

Refinement on F²	Primary atom site location: iterative
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.036	H-atom parameters constrained
wR(F²) = 0.081	w = 1/[σ²(F_o²) + (0.0308P)² + 1.4147P] where P = (F_o² + 2F_c²)/3
S = 1.08	(Δ/σ)_max < 0.001
2821 reflections	Δρ_max = 0.58 e Å⁻³
88 parameters	Δρ_min = −0.58 e Å⁻³
0 restraints

Special details top

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
Cu1	0.500000	0.22261 (4)	0.250000	0.01825 (9)
Cl1	0.38953 (3)	0.10590 (5)	0.13863 (3)	0.02196 (11)
Cl2	0.41898 (3)	0.32033 (5)	0.36739 (4)	0.02260 (11)
N1	0.68501 (11)	0.01294 (19)	0.63521 (12)	0.0218 (3)
H1	0.642734	−0.054296	0.645210	0.026*
C2	0.66434 (12)	0.1697 (2)	0.62543 (13)	0.0197 (3)
C3	0.73176 (13)	0.2747 (2)	0.61076 (14)	0.0222 (4)
H3	0.720458	0.386273	0.605979	0.027*
C4	0.83354 (14)	0.0533 (2)	0.61276 (16)	0.0261 (4)
H4	0.890816	0.012622	0.607122	0.031*
C5	0.81548 (14)	0.2165 (2)	0.60311 (15)	0.0247 (4)
H5	0.861102	0.288380	0.591178	0.030*
C6	0.76632 (14)	−0.0468 (2)	0.63060 (15)	0.0254 (4)
H6	0.777088	−0.158092	0.639704	0.031*
C7	0.57039 (13)	0.2174 (2)	0.62851 (16)	0.0259 (4)
H7A	0.536395	0.214343	0.556960	0.039*
H7B	0.569141	0.325976	0.656845	0.039*
H7C	0.543936	0.143189	0.673767	0.039*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.02142 (16)	0.01465 (15)	0.01929 (16)	0.000	0.00510 (12)	0.000
Cl1	0.0253 (2)	0.0174 (2)	0.0226 (2)	−0.00165 (16)	0.00223 (17)	−0.00185 (15)
Cl2	0.0276 (2)	0.0172 (2)	0.0246 (2)	0.00035 (16)	0.00935 (17)	−0.00340 (16)
N1	0.0268 (8)	0.0154 (7)	0.0235 (7)	−0.0023 (6)	0.0054 (6)	0.0011 (6)
C2	0.0264 (9)	0.0172 (8)	0.0155 (8)	−0.0004 (7)	0.0033 (7)	0.0000 (6)
C3	0.0311 (10)	0.0150 (8)	0.0203 (8)	−0.0030 (7)	0.0040 (7)	0.0004 (6)
C4	0.0251 (10)	0.0266 (10)	0.0267 (9)	0.0016 (8)	0.0040 (8)	−0.0010 (8)
C5	0.0281 (10)	0.0221 (9)	0.0244 (9)	−0.0069 (7)	0.0056 (8)	−0.0008 (7)
C6	0.0326 (10)	0.0172 (9)	0.0265 (10)	0.0031 (7)	0.0048 (8)	0.0016 (7)
C7	0.0263 (10)	0.0243 (10)	0.0276 (10)	0.0018 (7)	0.0061 (8)	0.0004 (8)

Geometric parameters (Å, º) top

Cu1—Cl1ⁱ	2.2496 (5)	C3—C5	1.383 (3)
Cu1—Cl1	2.2496 (5)	C4—H4	0.9500
Cu1—Cl2	2.2492 (4)	C4—C5	1.395 (3)
Cu1—Cl2ⁱ	2.2492 (4)	C4—C6	1.370 (3)
N1—H1	0.8800	C5—H5	0.9500
N1—C2	1.350 (2)	C6—H6	0.9500
N1—C6	1.346 (2)	C7—H7A	0.9800
C2—C3	1.387 (3)	C7—H7B	0.9800
C2—C7	1.493 (3)	C7—H7C	0.9800
C3—H3	0.9500

Cl1—Cu1—Cl1ⁱ	128.54 (3)	C5—C4—H4	121.0
Cl2ⁱ—Cu1—Cl1	99.614 (17)	C6—C4—H4	121.0
Cl2ⁱ—Cu1—Cl1ⁱ	98.550 (17)	C6—C4—C5	118.10 (19)
Cl2—Cu1—Cl1	98.549 (17)	C3—C5—C4	120.61 (18)
Cl2—Cu1—Cl1ⁱ	99.616 (17)	C3—C5—H5	119.7
Cl2ⁱ—Cu1—Cl2	137.36 (3)	C4—C5—H5	119.7
C2—N1—H1	118.0	N1—C6—C4	119.91 (18)
C6—N1—H1	118.0	N1—C6—H6	120.0
C6—N1—C2	124.00 (17)	C4—C6—H6	120.0
N1—C2—C3	117.46 (17)	C2—C7—H7A	109.5
N1—C2—C7	117.88 (17)	C2—C7—H7B	109.5
C3—C2—C7	124.64 (17)	C2—C7—H7C	109.5
C2—C3—H3	120.1	H7A—C7—H7B	109.5
C5—C3—C2	119.88 (17)	H7A—C7—H7C	109.5
C5—C3—H3	120.1	H7B—C7—H7C	109.5

N1—C2—C3—C5	2.2 (3)	C6—N1—C2—C3	−0.6 (3)
C2—N1—C6—C4	−1.5 (3)	C6—N1—C2—C7	177.92 (17)
C2—C3—C5—C4	−1.7 (3)	C6—C4—C5—C3	−0.4 (3)
C5—C4—C6—N1	2.0 (3)	C7—C2—C3—C5	−176.27 (18)

Symmetry code: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···Cl1ⁱⁱ	0.88	2.93	3.4297 (16)	118
N1—H1···Cl2ⁱⁱ	0.88	2.41	3.2050 (16)	150
C6—H6···Cl1ⁱⁱⁱ	0.95	2.62	3.453 (2)	147
C7—H7A···Cl2	0.98	2.92	3.850 (2)	159
C7—H7B···Cl2^iv	0.98	2.98	3.872 (2)	151

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

Acknowledgements

We thank Dr J. S. Yadav, Provost and Director (R&D) for his support and encouragement.

Funding information

Funding for this research was provided by: Indrashil University.

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