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The asymmetric unit of the title compound, C16H22N22+·2PF6, contains one half-mol­ecule and a hexa­fluoro­phosphate anion. In the crystal structure, inter­molecular C—H...F hydrogen bonds link the mol­ecules. The F atoms in the hexa­fluoro­phosphate anion are disordered over two positions and were refined with occupancies of 0.43 (2) and 0.57 (2).

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536808039639/hk2581sup1.cif
Contains datablocks I, global, x1

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536808039639/hk2581Isup2.hkl
Contains datablock I

CCDC reference: 713290

Key indicators

  • Single-crystal X-ray study
  • T = 298 K
  • Mean [sigma](C-C) = 0.007 Å
  • Disorder in solvent or counterion
  • R factor = 0.065
  • wR factor = 0.166
  • Data-to-parameter ratio = 10.1

checkCIF/PLATON results

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Alert level C PLAT340_ALERT_3_C Low Bond Precision on C-C Bonds (x 1000) Ang ... 7 PLAT066_ALERT_1_C Predicted and Reported Transmissions Identical . ? PLAT154_ALERT_1_C The su's on the Cell Angles are Equal (x 10000) 3000 Deg. PLAT234_ALERT_4_C Large Hirshfeld Difference C1 -- C2 .. 0.12 Ang. PLAT244_ALERT_4_C Low 'Solvent' Ueq as Compared to Neighbors for P
Alert level G PLAT180_ALERT_4_G Check Cell Rounding: # of Values Ending with 0 = 3 PLAT302_ALERT_4_G Anion/Solvent Disorder ......................... 46.00 Perc.
0 ALERT level A = In general: serious problem 0 ALERT level B = Potentially serious problem 5 ALERT level C = Check and explain 2 ALERT level G = General alerts; check 2 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 0 ALERT type 2 Indicator that the structure model may be wrong or deficient 1 ALERT type 3 Indicator that the structure quality may be low 4 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check

Comment top

The title compound is a dicationic ionic liquid, which has high thermal stability. Applications of the dicationic ionic liquid are found in biochemistry as well as many areas of chemistry (Jared et al., 2005). We report herein the crystal structure of the title compound.

The asymmetric unit of the title compound (Fig. 1) contains one-half molecule and a hexafluorophosphate molecule, where the bond lengths (Allen et al., 1987) and angles are within normal ranges.

In the crystal structure, intermolecular C-H···F hydrogen bonds (Table 1) link the molecules (Fig. 2), in which they may be effective in the stabilization of the structure.

Related literature top

For general background, see: Jared et al. (2005). For bond-length data, see: Allen et al. (1987).

Experimental top

For the preparation of the title compound, 1,6-dibromide hexane (12.2 g, 0.05 mol) was added to acetonitrile solution (50 ml) of dehydrate pyridine (7.91 g, 0.10 mol) at 353 K. After stirring for 24 h, the mixture was cooled to room temperature and filtered. The solid was washed with ethyl acetate and dried. Then, the solid (2.01 g, 5 mmol) was dissolved in distilled water (50 ml) and potassium hexafluorophosphate (1.84 g, 10 mmol) was added. After stirring at room temperature for 3 h, the colorless solid formed was collected by filtration, washed with distilled water (50 ml) and dried. The product was purified by repeated crystallization. Crystals suitable for X-ray analysis were obtained by slow evaporation of acetone (yield; 3.08 g, 80%, m.p. 513 K).

Refinement top

The F1, F2, F3, F4, F5 and F6 atoms in hexafluorophosphate were disordered over two positions. During the refinement process the disordered atoms were refined with occupancies of 0.43 (2) for F1, F2, F3, F4, F5 , F6 and 0.57 (2) for F1', F2', F3', F4', F5', F6', respectively. H atoms were positioned geometrically, with C-H = 0.93 and 0.97 Å for aromatic and methylene H, respectively, and constrained to ride on their parent atoms with Uiso(H) = 1.2Ueq(C).

Computing details top

Data collection: CAD-4 Software (Enraf–Nonius, 1989); cell refinement: CAD-4 Software (Enraf–Nonius, 1989); data reduction: XCAD4 (Harms & Wocadlo, 1995); 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: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The asymmetric unit of the title compound, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
[Figure 2] Fig. 2. A partial packing diagram of the title compound. Hydrogen bonds are shown as dashed lines.
1,1'-(Hexane-1,6-diyl)dipyridinium bis(hexafluorophosphate) top
Crystal data top
C16H22N22+·2PF6Z = 1
Mr = 532.30 (3)F(000) = 270
Triclinic, P1Dx = 1.545 Mg m3
Hall symbol: -P 1Melting point: 513 K
a = 7.9140 (16) ÅMo Kα radiation, λ = 0.71073 Å
b = 9.2930 (18) ÅCell parameters from 25 reflections
c = 9.4870 (19) Åθ = 10–12°
α = 65.13 (3)°µ = 0.29 mm1
β = 65.46 (3)°T = 298 K
γ = 74.37 (3)°Block, colorless
V = 572.0 (3) Å30.30 × 0.30 × 0.20 mm
Data collection top
Enraf–Nonius CAD-4
diffractometer
1499 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.047
Graphite monochromatorθmax = 25.1°, θmin = 2.4°
ω/2θ scansh = 89
Absorption correction: ψ scan
(North et al., 1968)
k = 910
Tmin = 0.917, Tmax = 0.944l = 011
2172 measured reflections3 standard reflections every 120 min
2014 independent reflections intensity decay: none
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.065H-atom parameters constrained
wR(F2) = 0.166 w = 1/[σ2(Fo2) + (0.06P)2 + 0.95P]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
2014 reflectionsΔρmax = 0.30 e Å3
200 parametersΔρmin = 0.38 e Å3
Primary atom site location: structure-invariant direct methods
Crystal data top
C16H22N22+·2PF6γ = 74.37 (3)°
Mr = 532.30 (3)V = 572.0 (3) Å3
Triclinic, P1Z = 1
a = 7.9140 (16) ÅMo Kα radiation
b = 9.2930 (18) ŵ = 0.29 mm1
c = 9.4870 (19) ÅT = 298 K
α = 65.13 (3)°0.30 × 0.30 × 0.20 mm
β = 65.46 (3)°
Data collection top
Enraf–Nonius CAD-4
diffractometer
1499 reflections with I > 2σ(I)
Absorption correction: ψ scan
(North et al., 1968)
Rint = 0.047
Tmin = 0.917, Tmax = 0.9443 standard reflections every 120 min
2172 measured reflections intensity decay: none
2014 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.065200 parameters
wR(F2) = 0.166H-atom parameters constrained
S = 1.01Δρmax = 0.30 e Å3
2014 reflectionsΔρmin = 0.38 e Å3
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
P0.16995 (14)0.79005 (13)0.78487 (13)0.0539 (4)
N0.6355 (4)0.7536 (4)0.2462 (4)0.0472 (8)
F10.006 (3)0.696 (3)0.842 (2)0.156 (6)0.43 (2)
F20.369 (2)0.8457 (19)0.721 (2)0.104 (5)0.43 (2)
F30.034 (2)0.8894 (16)0.8982 (15)0.091 (4)0.43 (2)
F40.215 (2)0.645 (2)0.939 (2)0.076 (4)0.43 (2)
F50.126 (2)0.936 (2)0.635 (2)0.078 (4)0.43 (2)
F60.223 (3)0.677 (3)0.684 (2)0.076 (4)0.43 (2)
F1'0.0338 (9)0.7809 (16)0.8155 (14)0.118 (4)0.57 (2)
F2'0.375 (2)0.785 (2)0.775 (2)0.144 (5)0.57 (2)
F3'0.127 (2)0.9036 (12)0.8910 (13)0.098 (3)0.57 (2)
F4'0.150 (2)0.6338 (18)0.9501 (17)0.090 (4)0.57 (2)
F5'0.195 (2)0.9495 (17)0.6211 (17)0.094 (4)0.57 (2)
F6'0.2820 (19)0.6854 (19)0.6687 (18)0.082 (4)0.57 (2)
C10.6255 (6)0.6893 (5)0.1468 (5)0.0607 (11)
H1A0.72270.61590.11130.073*
C20.4732 (7)0.7312 (6)0.0972 (6)0.0735 (13)
H2A0.46610.68660.02880.088*
C30.3292 (6)0.8420 (6)0.1517 (6)0.0751 (14)
H3A0.22600.87360.11790.090*
C40.3402 (6)0.9030 (6)0.2537 (6)0.0721 (13)
H4A0.24280.97510.29130.087*
C50.4934 (5)0.8603 (5)0.3029 (5)0.0543 (10)
H5A0.50030.90290.37300.065*
C60.7977 (5)0.7070 (5)0.3014 (5)0.0580 (10)
H6A0.83870.80220.28960.070*
H6B0.89980.65580.23070.070*
C70.7536 (5)0.5942 (5)0.4801 (5)0.0563 (10)
H7A0.71840.49690.49080.068*
H7B0.64750.64340.55020.068*
C80.9189 (5)0.5519 (5)0.5406 (5)0.0602 (11)
H8A0.96280.64980.51830.072*
H8B0.87610.49630.65950.072*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
P0.0470 (6)0.0550 (6)0.0538 (6)0.0051 (4)0.0114 (5)0.0263 (5)
N0.0332 (15)0.0466 (17)0.0475 (17)0.0002 (13)0.0093 (13)0.0107 (14)
F10.136 (9)0.160 (11)0.165 (9)0.050 (8)0.033 (7)0.049 (8)
F20.082 (6)0.104 (7)0.133 (9)0.045 (5)0.035 (6)0.030 (6)
F30.101 (8)0.077 (5)0.074 (5)0.016 (5)0.007 (5)0.048 (4)
F40.085 (8)0.067 (5)0.077 (7)0.003 (6)0.043 (6)0.016 (4)
F50.070 (6)0.080 (7)0.059 (5)0.015 (5)0.024 (5)0.015 (4)
F60.097 (9)0.078 (5)0.083 (8)0.014 (6)0.038 (7)0.046 (5)
F1'0.041 (3)0.113 (7)0.173 (7)0.002 (3)0.039 (3)0.027 (5)
F2'0.118 (6)0.180 (10)0.147 (8)0.033 (7)0.069 (6)0.036 (7)
F3'0.126 (7)0.088 (4)0.086 (4)0.000 (5)0.021 (5)0.058 (3)
F4'0.090 (7)0.068 (4)0.074 (4)0.010 (5)0.009 (5)0.022 (3)
F5'0.124 (8)0.077 (4)0.069 (4)0.014 (6)0.023 (6)0.023 (3)
F6'0.074 (6)0.078 (5)0.075 (4)0.002 (4)0.003 (4)0.043 (3)
C10.064 (3)0.052 (2)0.057 (2)0.0000 (19)0.015 (2)0.022 (2)
C20.084 (3)0.086 (3)0.066 (3)0.017 (3)0.040 (3)0.023 (3)
C30.051 (3)0.095 (4)0.066 (3)0.015 (2)0.031 (2)0.002 (3)
C40.042 (2)0.083 (3)0.066 (3)0.014 (2)0.014 (2)0.021 (2)
C50.050 (2)0.056 (2)0.053 (2)0.0118 (18)0.0171 (18)0.0268 (19)
C60.0340 (19)0.066 (3)0.066 (3)0.0019 (17)0.0187 (18)0.017 (2)
C70.0339 (19)0.074 (3)0.057 (2)0.0055 (18)0.0156 (17)0.027 (2)
C80.044 (2)0.082 (3)0.060 (2)0.009 (2)0.0230 (19)0.035 (2)
Geometric parameters (Å, º) top
P—F1'1.535 (7)C3—C41.350 (7)
P—F61.567 (19)C3—H3A0.9300
P—F2'1.575 (15)C4—C51.379 (6)
P—F31.582 (11)C4—H4A0.9300
P—F21.583 (14)C5—N1.372 (5)
P—F51.588 (16)C5—H5A0.9300
P—F6'1.604 (14)N—C61.476 (5)
P—F4'1.611 (14)C6—C71.518 (6)
P—F41.612 (18)C6—H6A0.9700
P—F5'1.617 (14)C6—H6B0.9700
P—F11.619 (15)C7—C81.534 (5)
P—F3'1.631 (9)C7—H7A0.9700
C1—N1.347 (5)C7—H7B0.9700
C1—C21.375 (6)C8—C8i1.518 (7)
C1—H1A0.9300C8—H8A0.9700
C2—C31.397 (7)C8—H8B0.9700
C2—H2A0.9300
F1'—P—F685.7 (10)F4—P—F183.6 (8)
F1'—P—F2'173.4 (6)F5'—P—F1116.5 (8)
F6—P—F2'95.7 (10)F1'—P—F3'97.5 (6)
F1'—P—F370.4 (7)F6—P—F3'176.5 (11)
F6—P—F3156.1 (13)F2'—P—F3'80.9 (7)
F2'—P—F3107.8 (9)F2—P—F3'78.8 (9)
F1'—P—F2164.7 (6)F5—P—F3'92.5 (8)
F6—P—F298.4 (9)F6'—P—F3'160.7 (10)
F3—P—F2105.1 (10)F4'—P—F3'90.4 (7)
F1'—P—F576.2 (6)F4—P—F3'86.1 (8)
F6—P—F589.5 (10)F5'—P—F3'88.0 (6)
F2'—P—F5110.2 (6)F1—P—F3'112.6 (7)
F3—P—F586.5 (8)N—C1—C2120.6 (4)
F2—P—F589.1 (7)N—C1—H1A119.7
F1'—P—F6'101.7 (9)C2—C1—H1A119.7
F2'—P—F6'80.1 (9)C1—C2—C3118.7 (4)
F3—P—F6'172.1 (12)C1—C2—H2A120.7
F2—P—F6'82.4 (8)C3—C2—H2A120.7
F5—P—F6'91.2 (9)C4—C3—C2119.8 (4)
F1'—P—F4'86.0 (5)C4—C3—H3A120.1
F6—P—F4'88.5 (9)C2—C3—H3A120.1
F2'—P—F4'87.5 (6)C3—C4—C5121.1 (4)
F3—P—F4'88.2 (7)C3—C4—H4A119.4
F2—P—F4'108.7 (6)C5—C4—H4A119.4
F5—P—F4'162.2 (6)N—C5—C4118.6 (4)
F6'—P—F4'91.8 (7)N—C5—H5A120.7
F1'—P—F4104.3 (6)C4—C5—H5A120.7
F6—P—F491.8 (10)C1—N—C5121.2 (3)
F2'—P—F469.2 (7)C1—N—C6120.7 (3)
F3—P—F492.5 (9)C5—N—C6118.1 (3)
F2—P—F490.3 (7)N—C6—C7112.5 (3)
F5—P—F4178.6 (11)N—C6—H6A109.1
F6'—P—F490.0 (9)C7—C6—H6A109.1
F1'—P—F5'95.7 (6)N—C6—H6B109.1
F6—P—F5'93.0 (9)C7—C6—H6B109.1
F2'—P—F5'90.7 (6)H6A—C6—H6B107.8
F3—P—F5'91.0 (7)C6—C7—C8112.7 (3)
F2—P—F5'69.5 (6)C6—C7—H7A109.0
F6'—P—F5'89.2 (8)C8—C7—H7A109.0
F4'—P—F5'177.8 (7)C6—C7—H7B109.0
F4—P—F5'159.8 (6)C8—C7—H7B109.0
F6—P—F169.9 (12)H7A—C7—H7B107.8
F2'—P—F1149.1 (8)C8i—C8—C7113.4 (4)
F3—P—F187.2 (7)C8i—C8—H8A108.9
F2—P—F1166.6 (10)C7—C8—H8A108.9
F5—P—F197.2 (9)C8i—C8—H8B108.9
F6'—P—F185.7 (11)C7—C8—H8B108.9
F4'—P—F165.6 (7)H8A—C8—H8B107.7
Symmetry code: (i) x+2, y+1, z+1.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1A···F4ii0.932.483.333 (17)153
C2—H2A···F2iii0.932.533.267 (18)137
C3—H3A···F3iii0.932.473.257 (15)142
C4—H4A···F1iv0.932.523.287 (14)140
Symmetry codes: (ii) x+1, y+1, z+1; (iii) x, y, z1; (iv) x, y+2, z+1.

Experimental details

Crystal data
Chemical formulaC16H22N22+·2PF6
Mr532.30 (3)
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)7.9140 (16), 9.2930 (18), 9.4870 (19)
α, β, γ (°)65.13 (3), 65.46 (3), 74.37 (3)
V3)572.0 (3)
Z1
Radiation typeMo Kα
µ (mm1)0.29
Crystal size (mm)0.30 × 0.30 × 0.20
Data collection
DiffractometerEnraf–Nonius CAD-4
diffractometer
Absorption correctionψ scan
(North et al., 1968)
Tmin, Tmax0.917, 0.944
No. of measured, independent and
observed [I > 2σ(I)] reflections
2172, 2014, 1499
Rint0.047
(sin θ/λ)max1)0.598
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.065, 0.166, 1.01
No. of reflections2014
No. of parameters200
No. of restraints?
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.30, 0.38

Computer programs: CAD-4 Software (Enraf–Nonius, 1989), XCAD4 (Harms & Wocadlo, 1995), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C1—H1A···F4'i0.932.483.333 (17)153.00
C2—H2A···F2'ii0.932.533.267 (18)137.00
C3—H3A···F3'ii0.932.473.257 (15)142.00
C4—H4A···F1'iii0.932.523.287 (14)140.00
Symmetry codes: (i) x+1, y+1, z+1; (ii) x, y, z1; (iii) x, y+2, z+1.
 

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