metal-organic compounds
Bis(1-methylpiperidinium) tetrachloridocuprate(II)
aDepartment of Chemistry, Southeast Missouri State University, Cape Girardeau, MO 63701, USA
*Correspondence e-mail: bond@mbond2.st.semo.edu
The structure of the title compound, (C6H14N)2[CuCl4], consists of two inequivalent 1-methylpiperidinium cations and a flattened tetrahedral [CuCl4]2− anion. Each organic cation exhibits a chair conformation with the methyl group in the equatorial position. They are segregated into alternating layers parallel to (100) and stacked along [100]. The first cation is arranged in parallel stacks in a herringbone pattern with rows of [CuCl4]2− anions fitting between the stacks and with a Cl− ion directed into the interior of the layer. The second organic cation forms distorted hcp layers that separate the other organic cation/[CuCl4]2− slabs. N—H⋯Cl hydrogen bonding between the cations and the anions consolidates the crystal packing.
Related literature
For background to compounds with [CuCl4]2− anions, see: Awwadi et al. (2007); Bloomquist et al. (1988); Ihara (2007); Nelson et al. (1979); Schneider et al. (2007); Willett (1991); Willett & Twamley (2007). For related structures, see: Fernandez et al. (1987); Parent et al. (2007); Nalla & Bond (2011). For comparison bond lengths and angles, see: Ladd & Palmer (1994).
Experimental
Crystal data
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Refinement
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Data collection: COLLECT (Hooft, 1998); cell SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO (Otwinowski & Minor, 1997) and SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: WinGX (Farrugia, 1999).
Supporting information
10.1107/S1600536811016382/wm2484sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811016382/wm2484Isup2.hkl
5 ml of 1-methylpiperidine were neutralized with concentrated HCl. This solution was mixed in a 2:1 molar ratio with copper(II) chloride dissolved in 6M HCl. Slow evaporation yielded yellow crystals of the title compound.
All non-hydrogen atoms were refined with anisotropic displacement parameters. All hydrogen atoms were visible on electron density difference maps and freely refined to give N—H = 0.833–0.895 Å, methylene C—H = 0.913–1.03 Å. and methyl C—H = 0.945–0.97 Å.
Data collection: COLLECT (Hooft, 1998); cell
SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO and SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997) and ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: WinGX (Farrugia, 1999).(C6H14N)2[CuCl4] | F(000) = 844 |
Mr = 405.7 | Dx = 1.466 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
a = 12.2264 (2) Å | Cell parameters from 8818 reflections |
b = 11.3442 (2) Å | θ = 1.0–35.6° |
c = 13.3455 (2) Å | µ = 1.76 mm−1 |
β = 96.865 (1)° | T = 100 K |
V = 1837.73 (5) Å3 | Block, yellow |
Z = 4 | 0.32 × 0.23 × 0.17 mm |
Nonius KappaCCD diffractometer | 8453 independent reflections |
Graphite monochromator | 6647 reflections with I > 2σ(I) |
Detector resolution: 9 pixels mm-1 | Rint = 0.026 |
ω and ϕ scans | θmax = 35.6°, θmin = 4.0° |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | h = −19→20 |
Tmin = 0.628, Tmax = 0.694 | k = −18→18 |
16568 measured reflections | l = −21→21 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.030 | All H-atom parameters refined |
wR(F2) = 0.067 | w = 1/[σ2(Fo2) + (0.0249P)2 + 0.6467P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max = 0.006 |
8453 reflections | Δρmax = 0.57 e Å−3 |
285 parameters | Δρmin = −0.58 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0017 (3) |
(C6H14N)2[CuCl4] | V = 1837.73 (5) Å3 |
Mr = 405.7 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 12.2264 (2) Å | µ = 1.76 mm−1 |
b = 11.3442 (2) Å | T = 100 K |
c = 13.3455 (2) Å | 0.32 × 0.23 × 0.17 mm |
β = 96.865 (1)° |
Nonius KappaCCD diffractometer | 8453 independent reflections |
Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) | 6647 reflections with I > 2σ(I) |
Tmin = 0.628, Tmax = 0.694 | Rint = 0.026 |
16568 measured reflections |
R[F2 > 2σ(F2)] = 0.030 | 0 restraints |
wR(F2) = 0.067 | All H-atom parameters refined |
S = 1.05 | Δρmax = 0.57 e Å−3 |
8453 reflections | Δρmin = −0.58 e Å−3 |
285 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Cu1 | 0.251677 (12) | 0.415201 (12) | 0.299141 (10) | 0.01376 (4) | |
Cl1 | 0.06546 (2) | 0.42579 (2) | 0.25734 (2) | 0.01674 (5) | |
Cl2 | 0.27180 (2) | 0.52180 (2) | 0.44100 (2) | 0.01610 (5) | |
Cl3 | 0.30403 (3) | 0.43621 (3) | 0.14382 (2) | 0.02020 (6) | |
Cl4 | 0.35629 (3) | 0.25748 (3) | 0.34713 (2) | 0.01954 (6) | |
N11 | 0.07370 (8) | 0.22960 (9) | 0.08737 (7) | 0.01501 (17) | |
H11 | 0.0798 (13) | 0.2956 (15) | 0.1244 (12) | 0.020 (4)* | |
C11 | 0.14106 (11) | 0.13720 (12) | 0.14522 (10) | 0.0219 (2) | |
H11A | 0.1456 (15) | 0.0723 (16) | 0.1014 (13) | 0.028 (5)* | |
H11B | 0.2116 (14) | 0.1704 (15) | 0.1677 (12) | 0.024 (4)* | |
H11C | 0.1045 (16) | 0.1151 (17) | 0.2025 (15) | 0.037 (5)* | |
C12 | −0.04575 (10) | 0.19611 (12) | 0.07114 (10) | 0.0206 (2) | |
H12A | −0.0483 (14) | 0.1249 (16) | 0.0391 (12) | 0.023 (4)* | |
H12B | −0.0671 (14) | 0.1811 (15) | 0.1347 (13) | 0.024 (4)* | |
C13 | −0.11317 (11) | 0.29197 (12) | 0.01392 (10) | 0.0211 (2) | |
H13A | −0.1880 (15) | 0.2688 (15) | 0.0042 (13) | 0.026 (4)* | |
H13B | −0.1108 (14) | 0.3600 (16) | 0.0564 (13) | 0.026 (4)* | |
C14 | −0.07016 (12) | 0.32027 (14) | −0.08588 (10) | 0.0264 (3) | |
H14A | −0.0764 (15) | 0.2522 (17) | −0.1302 (14) | 0.033 (5)* | |
H14B | −0.1129 (15) | 0.3849 (17) | −0.1173 (14) | 0.033 (5)* | |
C15 | 0.05150 (12) | 0.35232 (14) | −0.06641 (11) | 0.0275 (3) | |
H15A | 0.0813 (15) | 0.3663 (17) | −0.1260 (14) | 0.031 (5)* | |
H15B | 0.0616 (17) | 0.4262 (18) | −0.0268 (15) | 0.040 (5)* | |
C16 | 0.11738 (11) | 0.25462 (11) | −0.01073 (9) | 0.0190 (2) | |
H16A | 0.1110 (13) | 0.1833 (14) | −0.0472 (11) | 0.017 (4)* | |
H16B | 0.1918 (14) | 0.2742 (14) | 0.0066 (12) | 0.019 (4)* | |
N21 | 0.51192 (8) | 0.25190 (9) | 0.15565 (8) | 0.01564 (18) | |
H21 | 0.4620 (13) | 0.2945 (14) | 0.1731 (12) | 0.017 (4)* | |
C21 | 0.45664 (12) | 0.14160 (12) | 0.11569 (11) | 0.0232 (2) | |
H21A | 0.5108 (15) | 0.0891 (16) | 0.0926 (14) | 0.030 (5)* | |
H21B | 0.4240 (16) | 0.1038 (17) | 0.1704 (15) | 0.036 (5)* | |
H21C | 0.4060 (14) | 0.1605 (16) | 0.0588 (13) | 0.028 (4)* | |
C22 | 0.55885 (11) | 0.31840 (12) | 0.07359 (9) | 0.0203 (2) | |
H22A | 0.6091 (13) | 0.2664 (14) | 0.0498 (12) | 0.020 (4)* | |
H22B | 0.4995 (15) | 0.3324 (16) | 0.0233 (13) | 0.027 (4)* | |
C23 | 0.61029 (13) | 0.43323 (12) | 0.11370 (11) | 0.0259 (3) | |
H23A | 0.6408 (16) | 0.4715 (17) | 0.0596 (14) | 0.034 (5)* | |
H23B | 0.5515 (15) | 0.4840 (16) | 0.1296 (13) | 0.030 (5)* | |
C24 | 0.69579 (12) | 0.41383 (14) | 0.20480 (11) | 0.0276 (3) | |
H24A | 0.7614 (16) | 0.3662 (18) | 0.1844 (14) | 0.039 (5)* | |
H24B | 0.7199 (17) | 0.491 (2) | 0.2345 (15) | 0.045 (6)* | |
C25 | 0.64709 (12) | 0.34239 (14) | 0.28531 (10) | 0.0256 (3) | |
H25A | 0.7000 (15) | 0.3232 (16) | 0.3397 (13) | 0.030 (5)* | |
H25B | 0.5928 (15) | 0.3843 (16) | 0.3125 (13) | 0.025 (4)* | |
C26 | 0.59873 (11) | 0.22741 (12) | 0.24265 (9) | 0.0206 (2) | |
H26A | 0.6515 (13) | 0.1796 (14) | 0.2156 (11) | 0.019 (4)* | |
H26B | 0.5624 (13) | 0.1821 (14) | 0.2901 (12) | 0.018 (4)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.01396 (7) | 0.01435 (7) | 0.01306 (6) | 0.00173 (5) | 0.00206 (4) | −0.00012 (5) |
Cl1 | 0.01474 (12) | 0.01853 (12) | 0.01674 (11) | 0.00235 (9) | 0.00100 (9) | −0.00114 (9) |
Cl2 | 0.01717 (12) | 0.01518 (12) | 0.01603 (11) | −0.00021 (9) | 0.00233 (9) | −0.00179 (9) |
Cl3 | 0.02281 (14) | 0.02322 (14) | 0.01554 (12) | 0.00504 (11) | 0.00628 (10) | 0.00299 (10) |
Cl4 | 0.02184 (14) | 0.01968 (13) | 0.01715 (12) | 0.00794 (10) | 0.00254 (10) | 0.00137 (9) |
N11 | 0.0150 (4) | 0.0163 (4) | 0.0139 (4) | −0.0004 (3) | 0.0024 (3) | −0.0013 (3) |
C11 | 0.0210 (6) | 0.0241 (6) | 0.0199 (5) | 0.0035 (5) | −0.0001 (4) | 0.0035 (5) |
C12 | 0.0159 (5) | 0.0209 (6) | 0.0249 (6) | −0.0028 (4) | 0.0024 (4) | 0.0056 (5) |
C13 | 0.0153 (5) | 0.0222 (6) | 0.0259 (6) | 0.0016 (4) | 0.0030 (4) | 0.0026 (5) |
C14 | 0.0264 (7) | 0.0306 (7) | 0.0219 (6) | 0.0090 (6) | 0.0013 (5) | 0.0068 (5) |
C15 | 0.0279 (7) | 0.0290 (7) | 0.0278 (6) | 0.0073 (6) | 0.0127 (5) | 0.0135 (5) |
C16 | 0.0194 (6) | 0.0216 (6) | 0.0171 (5) | 0.0023 (4) | 0.0067 (4) | 0.0005 (4) |
N21 | 0.0142 (4) | 0.0144 (4) | 0.0184 (4) | 0.0005 (3) | 0.0022 (3) | −0.0018 (3) |
C21 | 0.0212 (6) | 0.0185 (6) | 0.0307 (7) | −0.0037 (5) | 0.0059 (5) | −0.0071 (5) |
C22 | 0.0211 (6) | 0.0225 (6) | 0.0174 (5) | −0.0028 (5) | 0.0024 (4) | 0.0005 (4) |
C23 | 0.0281 (7) | 0.0207 (6) | 0.0295 (7) | −0.0066 (5) | 0.0062 (5) | 0.0004 (5) |
C24 | 0.0211 (6) | 0.0306 (7) | 0.0312 (7) | −0.0085 (5) | 0.0031 (5) | −0.0106 (6) |
C25 | 0.0223 (6) | 0.0334 (7) | 0.0200 (6) | 0.0009 (5) | −0.0009 (5) | −0.0086 (5) |
C26 | 0.0202 (6) | 0.0228 (6) | 0.0185 (5) | 0.0056 (5) | 0.0014 (4) | 0.0001 (4) |
Cu1—Cl1 | 2.2816 (3) | C16—H16A | 0.943 (16) |
Cu1—Cl2 | 2.2351 (3) | C16—H16B | 0.938 (16) |
Cu1—Cl3 | 2.2539 (3) | N21—C21 | 1.4903 (16) |
Cu1—Cl4 | 2.2475 (3) | N21—C22 | 1.4992 (16) |
N11—C11 | 1.4904 (16) | N21—C26 | 1.5024 (16) |
N11—C16 | 1.4990 (15) | N21—H21 | 0.833 (16) |
N11—C12 | 1.4995 (16) | C21—H21A | 0.968 (19) |
N11—H11 | 0.895 (17) | C21—H21B | 0.97 (2) |
C11—H11A | 0.946 (18) | C21—H21C | 0.945 (18) |
C11—H11B | 0.957 (17) | C22—C23 | 1.5160 (19) |
C11—H11C | 0.96 (2) | C22—H22A | 0.934 (17) |
C12—C13 | 1.5148 (18) | C22—H22B | 0.941 (18) |
C12—H12A | 0.913 (18) | C23—C24 | 1.522 (2) |
C12—H12B | 0.932 (17) | C23—H23A | 0.955 (19) |
C13—C14 | 1.5233 (19) | C23—H23B | 0.964 (19) |
C13—H13A | 0.946 (18) | C24—C25 | 1.523 (2) |
C13—H13B | 0.956 (18) | C24—H24A | 1.03 (2) |
C14—C15 | 1.523 (2) | C24—H24B | 0.99 (2) |
C14—H14A | 0.970 (19) | C25—C26 | 1.515 (2) |
C14—H14B | 0.966 (19) | C25—H25A | 0.938 (18) |
C15—C16 | 1.5121 (19) | C25—H25B | 0.925 (18) |
C15—H15A | 0.927 (18) | C26—H26A | 0.948 (16) |
C15—H15B | 0.99 (2) | C26—H26B | 0.964 (16) |
Cl1—Cu1—Cl2 | 100.615 (11) | N11—C16—H16B | 105.4 (10) |
Cl1—Cu1—Cl3 | 98.880 (12) | C15—C16—H16B | 113.0 (10) |
Cl1—Cu1—Cl4 | 128.967 (13) | H16A—C16—H16B | 110.4 (13) |
Cl2—Cu1—Cl3 | 135.003 (13) | C21—N21—C22 | 110.98 (10) |
Cl2—Cu1—Cl4 | 100.840 (12) | C21—N21—C26 | 111.69 (10) |
Cl3—Cu1—Cl4 | 97.568 (12) | C22—N21—C26 | 111.15 (10) |
C11—N11—C16 | 110.68 (10) | C21—N21—H21 | 105.7 (11) |
C11—N11—C12 | 111.41 (10) | C22—N21—H21 | 105.7 (11) |
C16—N11—C12 | 111.37 (10) | C26—N21—H21 | 111.4 (11) |
C11—N11—H11 | 107.3 (10) | N21—C21—H21A | 109.4 (11) |
C16—N11—H11 | 108.0 (10) | N21—C21—H21B | 108.1 (11) |
C12—N11—H11 | 107.9 (10) | H21A—C21—H21B | 109.0 (15) |
N11—C11—H11A | 107.3 (11) | N21—C21—H21C | 108.8 (11) |
N11—C11—H11B | 107.9 (10) | H21A—C21—H21C | 106.9 (15) |
H11A—C11—H11B | 112.6 (15) | H21B—C21—H21C | 114.5 (16) |
N11—C11—H11C | 108.3 (12) | N21—C22—C23 | 110.69 (10) |
H11A—C11—H11C | 110.8 (16) | N21—C22—H22A | 104.8 (10) |
H11B—C11—H11C | 109.9 (15) | C23—C22—H22A | 113.6 (10) |
N11—C12—C13 | 110.66 (10) | N21—C22—H22B | 106.0 (11) |
N11—C12—H12A | 105.7 (11) | C23—C22—H22B | 111.0 (11) |
C13—C12—H12A | 114.4 (11) | H22A—C22—H22B | 110.3 (14) |
N11—C12—H12B | 106.7 (10) | C22—C23—C24 | 111.97 (12) |
C13—C12—H12B | 113.3 (10) | C22—C23—H23A | 107.8 (11) |
H12A—C12—H12B | 105.4 (15) | C24—C23—H23A | 112.2 (11) |
C12—C13—C14 | 111.60 (11) | C22—C23—H23B | 107.6 (11) |
C12—C13—H13A | 109.2 (10) | C24—C23—H23B | 111.7 (10) |
C14—C13—H13A | 111.6 (10) | H23A—C23—H23B | 105.3 (15) |
C12—C13—H13B | 107.7 (10) | C23—C24—C25 | 110.59 (12) |
C14—C13—H13B | 111.1 (10) | C23—C24—H24A | 110.3 (11) |
H13A—C13—H13B | 105.4 (14) | C25—C24—H24A | 106.9 (11) |
C15—C14—C13 | 109.47 (11) | C23—C24—H24B | 109.7 (12) |
C15—C14—H14A | 107.4 (11) | C25—C24—H24B | 108.0 (12) |
C13—C14—H14A | 110.8 (11) | H24A—C24—H24B | 111.3 (16) |
C15—C14—H14B | 111.1 (11) | C26—C25—C24 | 111.17 (11) |
C13—C14—H14B | 108.3 (11) | C26—C25—H25A | 107.1 (11) |
H14A—C14—H14B | 109.9 (15) | C24—C25—H25A | 112.2 (11) |
C16—C15—C14 | 111.15 (12) | C26—C25—H25B | 108.9 (11) |
C16—C15—H15A | 107.8 (12) | C24—C25—H25B | 111.3 (11) |
C14—C15—H15A | 111.8 (11) | H25A—C25—H25B | 106.1 (15) |
C16—C15—H15B | 109.5 (12) | N21—C26—C25 | 109.82 (11) |
C14—C15—H15B | 110.5 (12) | N21—C26—H26A | 105.2 (9) |
H15A—C15—H15B | 106.0 (16) | C25—C26—H26A | 112.5 (10) |
N11—C16—C15 | 110.09 (10) | N21—C26—H26B | 105.5 (9) |
N11—C16—H16A | 105.8 (9) | C25—C26—H26B | 113.7 (9) |
C15—C16—H16A | 111.7 (9) | H26A—C26—H26B | 109.5 (13) |
D—H···A | D—H | H···A | D···A | D—H···A |
N11—H11···Cl1 | 0.895 (16) | 2.331 (16) | 3.188 (1) | 160 (1) |
N21—H21···Cl3 | 0.833 (17) | 2.508 (16) | 3.280 (1) | 155 (1) |
N21—H21···Cl4 | 0.833 (17) | 2.821 (17) | 3.364 (1) | 125 (1) |
Experimental details
Crystal data | |
Chemical formula | (C6H14N)2[CuCl4] |
Mr | 405.7 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 100 |
a, b, c (Å) | 12.2264 (2), 11.3442 (2), 13.3455 (2) |
β (°) | 96.865 (1) |
V (Å3) | 1837.73 (5) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.76 |
Crystal size (mm) | 0.32 × 0.23 × 0.17 |
Data collection | |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.628, 0.694 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 16568, 8453, 6647 |
Rint | 0.026 |
(sin θ/λ)max (Å−1) | 0.820 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.030, 0.067, 1.05 |
No. of reflections | 8453 |
No. of parameters | 285 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.57, −0.58 |
Computer programs: COLLECT (Hooft, 1998), DENZO and SCALEPACK (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1993), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997) and ORTEPIII (Burnett & Johnson, 1996), WinGX (Farrugia, 1999).
Cu1—Cl1 | 2.2816 (3) | Cu1—Cl3 | 2.2539 (3) |
Cu1—Cl2 | 2.2351 (3) | Cu1—Cl4 | 2.2475 (3) |
Cl1—Cu1—Cl2 | 100.615 (11) | Cl2—Cu1—Cl3 | 135.003 (13) |
Cl1—Cu1—Cl3 | 98.880 (12) | Cl2—Cu1—Cl4 | 100.840 (12) |
Cl1—Cu1—Cl4 | 128.967 (13) | Cl3—Cu1—Cl4 | 97.568 (12) |
D—H···A | D—H | H···A | D···A | D—H···A |
N11—H11···Cl1 | 0.895 (16) | 2.331 (16) | 3.188 (1) | 160 (1) |
N21—H21···Cl3 | 0.833 (17) | 2.508 (16) | 3.280 (1) | 155 (1) |
N21—H21···Cl4 | 0.833 (17) | 2.821 (17) | 3.364 (1) | 125 (1) |
Acknowledgements
The authors wish to thank the National Science Foundation DUE CCLI-A&I program (grant No. 9951348) and Southeast Missouri State University for funding the X-ray diffraction facility.
References
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
[CuCl4]2- anions exhibit geometries ranging from tetrahedral to square planar. The exact geometry adopted results from factors such as packing forces (Schneider et al., 2007; Nelson et al., 1979), hydrogen bonding (Bloomquist et al., 1988; Willett and Twamley, 2007), and halide···halide interactions (Awwadi et al., 2007), although the most commonly observed geometry is flattened tetrahedral with a trans Cl—Cu—Cl angle of ≈ 130–135° (Willett, 1991). A small number of thermochromic A2[CuCl4] compounds are known in which the low temperature (green-coloured) phase contains square-planar [CuCl4]2- while the high-temperature (yellow) phase contains flattened tetrahedral [CuCl4]2- anions (Ihara, 2007).
The crystal structure of the title compound, (1-methylpiperidinium)2CuCl4, is comprised of a [CuCl4]2- anion and two symmetrically inequivalent 1-methylpiperidinium cations. The [CuCl4]2- anion displays the typical flattened tetrahedral geometry with an average trans Cl—Cu—Cl angle of 131.99° at 100 K, so no thermochromic phase transition is observed upon cooling to at least this temperature. Each 1-methylpiperidinium ion exhibits a chair conformation with the methyl group equatorial. Bond lengths and angles for the inorganic complex and organic cation conform to expected values (Ladd & Palmer, 1994). An ORTEP diagram of the asymmetric unit is presented in Figure 1.
The two inequivalent organic cations are segregated into alternating layers parallel to (100) and stacked along [100]. The cation #1 layer (containing N11) arranges cations in parallel stacks along [010] and in a herringbone pattern with the cation plane approximately perpendicular to the layer plane (mean plane normal forming an angle of 91.63 (3)° with respect to a). Neighboring cations in the stacks are related by inversion and neighboring stacks are related by the c-glide plane. The [CuCl4]2- anions form rows of translationally equivalent complexes parallel to [010] that fit in between the stacks and on both sides of the cation #1 layer. Atom Cl1 is directed almost into the middle of the cation layer with the rows of complexes on either side of the layer offset from one another to provide spacing between the Cl1 atoms inside the layer. The closest intermolecular Cl···Cl contact distance is, thus, Cl1···Cl1i= 5.891 (4) Å (i=-x, 1/2+y, 1/2-z) between Cl1 atoms from opposite rows of complexes. Cation #2 forms a layer at x = 0.5 to separate the cation #1/[CuCl4]2- slabs at x = 0.0 and 1.0. In this layer the mean plane of the cation is closer to the layer plane with the normal forming an angle of 41.34° with respect to a. The cations in this layer are arranged in a distorted hcp pattern with neighboring cations related by inversion, 21 rotation, or c-glide plane operations. A short, direct N11—H11···Cl1 hydrogen bond locks the Cl1 atoms into the interior of the cation #1 layer while a longer, less direct, and bifurcated N21—H21···Cl3 and ···Cl4 hydrogen bond links the cation #1/[CuCl4]2- slabs to the cation #2 layer. A packing diagram for the structure viewed along [010] is presented in Figure 2.
In contrast to the layer structure of (1-methylpiperidinium)2[CuCl4], in the related piperdinium salt (Fernandez et al., 1987; CSD refcode: PNCLCU01) translationally equivalent rows of [CuCl4]2- anions are surrounded by stacks of translationally equivalent organic cations. N—H···Cl hydrogen bonding from one inequivalent organic cation links neighboring complexes in the same row while hydrogen bonding from the other inequivalent organic cation links complexes in different rows. So there are four direct hydrogen bonds in the piperidinium salt, versus one direct and one bifurcated in the title structure. Yet in spite of the greater degree of hydrogen bonding the average trans Cl—Cu—Cl angle of 133.49° (at room temperature) is only slightly larger. (1-Methylmorpholinium)2[CuCl4] (Parent et al., 2007; CSD refcode: VICMIE) also has rows or chains of [CuCl4]2- anions with short Cl···Cl contacts surrounded by parallel stacks of organic cations. The two inequivalent organic cations each form a bifurcated hydrogen bond to all four Cl ligands of the complex, which has an average trans Cl—Cu—Cl angle of 134.32° (158 K). The N,N-dimethylpiperidinium system has been studied, although no examples of a [CuCl4]2- salt have yet been found. Crystals of a light green [CuCl3(H2O)]- salt do, however, form readily (Nalla and Bond, 2011).