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The title compound, C
6H
18P
3+·CF
3SO
3−, crystallizes in two polymorphic forms in the space groups
P2
1/
c and
Pnma. In the orthorhombic form, the two crystallographically independent molecular units lie across a crystallographic mirror plane. The compound lacks traditional hydrogen-bond donors and, hence, is held together by weak C—H
O and C—H
F interactions, forming layers. The second polymorph was obtained as a by-product from the reaction of 1,3-bis(2,6-dimethylphenyl)-2,4-ditriflato-1,3,2,4-diazadiphosphetidine with tetramethyldiphosphine.
Supporting information
CCDC reference: 641816
All manipulations were performed under an inert atmosphere of dinitrogen. A
solution of tetramethyldiphosphine (126 mg, 1 mmol) in CH2Cl2 (2 ml) was
added to a solution of
1,3-bis(2,6-dimethylphenyl)-2,4-ditriflato-1,3,2,4-diazadiphosphetidine (300 mg, 0.5 mmol) in CH2Cl2 (3 ml) leading to the formation of a bright-yellow
solution. Addition of Et2O resulted in the formation of a bright-yellow
precipitate. Compound (I) was obtained as colorless needles from vapor
diffusion of Et2O into a CH2Cl2/CH3CN solution of the yellow
precipitate amidst copious amounts of a yellow oily material of unknown
constitution. The analytical data are in agreement with that previously
reported (Burford et al., 2005).
H atoms were located in a difference Fourier map and their coordinates were
refined in the riding mode [Uiso(H) = 1.2Ueq(C)]. The data
set for (I) was truncated at 2Θ = 60° as only statistically
insignificant data were present above the limit.
Data collection: PROCESS (Rigaku, 1996); cell refinement: PROCESS; data reduction: CrystalStructure (Rigaku/MSC, 2004); program(s) used to solve structure: SHELXS86 (Sheldrick, 1985); program(s) used to refine structure: CRYSTALS (Watkin et al., 1996); molecular graphics: DIAMOND (Brandenburg, 2000); software used to prepare material for publication: CrystalStructure.
bis(dimethylphosphino)dimethylphosphonium trifluoromethanesulfonate
top
Crystal data top
C6H18P3+·CF3O3S− | F(000) = 1376.00 |
Mr = 332.19 | Dx = 1.450 Mg m−3 |
Orthorhombic, Pnma | Mo Kα radiation, λ = 0.7107 Å |
Hall symbol: -P 2ac 2n | Cell parameters from 12587 reflections |
a = 23.5972 (7) Å | θ = 5.0–35.7° |
b = 10.7419 (4) Å | µ = 0.55 mm−1 |
c = 12.0086 (4) Å | T = 123 K |
V = 3043.9 (2) Å3 | Needle, colourless |
Z = 8 | 0.40 × 0.17 × 0.12 mm |
Data collection top
Rigaku R-AXIS diffractometer | Rint = 0.080 |
Detector resolution: 10.00 pixels mm-1 | θmax = 35.7° |
ω scans | h = −37→35 |
25123 measured reflections | k = −15→17 |
6230 independent reflections | l = −19→13 |
2682 reflections with F2 > 2σ(F2) | |
Refinement top
Refinement on F | H-atom parameters constrained |
R[F2 > 2σ(F2)] = 0.052 | Chebychev polynomial with three parameters (Carruthers & Watkin, 1979):
22.3826, -11.8310 and 17.0026 |
wR(F2) = 0.063 | (Δ/σ)max < 0.001 |
S = 1.06 | Δρmax = 1.08 e Å−3 |
2682 reflections | Δρmin = −0.62 e Å−3 |
193 parameters | |
Crystal data top
C6H18P3+·CF3O3S− | V = 3043.9 (2) Å3 |
Mr = 332.19 | Z = 8 |
Orthorhombic, Pnma | Mo Kα radiation |
a = 23.5972 (7) Å | µ = 0.55 mm−1 |
b = 10.7419 (4) Å | T = 123 K |
c = 12.0086 (4) Å | 0.40 × 0.17 × 0.12 mm |
Data collection top
Rigaku R-AXIS diffractometer | 2682 reflections with F2 > 2σ(F2) |
25123 measured reflections | Rint = 0.080 |
6230 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.052 | 193 parameters |
wR(F2) = 0.063 | H-atom parameters constrained |
S = 1.06 | Δρmax = 1.08 e Å−3 |
2682 reflections | Δρmin = −0.62 e Å−3 |
Special details top
Geometry. ENTER SPECIAL DETAILS OF THE MOLECULAR GEOMETRY |
Refinement. Refinement using reflections with F2 > 3.0 σ(F2). The
weighted R-factor(wR), goodness of fit (S) and
R-factor (gt) are based on F, with F set to zero for
negative F. The threshold expression of F2 > 2.0
σ(F2) is used only for calculating R-factor (gt). |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
S1 | −0.02148 (4) | 0.2500 | 0.29420 (9) | 0.0309 (3) | |
S2 | 0.26489 (4) | 0.2500 | 0.59125 (9) | 0.0279 (2) | |
P1 | 0.30491 (5) | 0.2500 | 0.00516 (10) | 0.0373 (3) | |
P2 | 0.27412 (4) | 0.2500 | 0.17720 (8) | 0.0234 (2) | |
P3 | 0.18032 (4) | 0.2500 | 0.17526 (9) | 0.0277 (3) | |
P4 | −0.01508 (5) | 0.2500 | 0.69750 (10) | 0.0362 (3) | |
P5 | 0.07646 (5) | 0.2500 | 0.65808 (10) | 0.0314 (3) | |
P6 | 0.12354 (5) | 0.2500 | 0.81492 (12) | 0.0488 (4) | |
F1 | −0.0377 (2) | 0.2500 | 0.0796 (4) | 0.143 (3) | |
F2 | 0.0360 (2) | 0.1538 (7) | 0.1336 (3) | 0.182 (2) | |
F3 | 0.3624 (2) | 0.1508 (4) | 0.5432 (4) | 0.1076 (13) | |
F4 | 0.3591 (2) | 0.2500 | 0.6997 (6) | 0.123 (2) | |
O1 | −0.0544 (1) | 0.3615 (3) | 0.3004 (3) | 0.0622 (9) | |
O2 | 0.0296 (2) | 0.2500 | 0.3590 (3) | 0.0447 (10) | |
O3 | 0.2501 (2) | 0.2500 | 0.4765 (3) | 0.067 (2) | |
O4 | 0.25075 (13) | 0.1376 (3) | 0.6490 (3) | 0.0550 (8) | |
C1 | 0.2627 (2) | 0.3816 (4) | −0.0477 (3) | 0.0431 (9) | |
C2 | 0.30363 (13) | 0.1159 (3) | 0.2446 (3) | 0.0320 (7) | |
C3 | 0.1660 (1) | 0.1190 (3) | 0.2687 (3) | 0.0420 (9) | |
C4 | −0.0386 (2) | 0.1174 (4) | 0.6123 (4) | 0.0445 (9) | |
C5 | 0.0985 (1) | 0.1158 (4) | 0.5799 (3) | 0.0395 (8) | |
C6 | 0.0880 (2) | 0.3820 (4) | 0.8810 (3) | 0.0516 (11) | |
C7 | 0.0040 (3) | 0.2500 | 0.1521 (6) | 0.107 (3) | |
C9 | 0.3412 (2) | 0.2500 | 0.5920 (7) | 0.063 (2) | |
H1 | 0.2763 | 0.4569 | −0.0158 | 0.052* | |
H2 | 0.2662 | 0.3857 | −0.1265 | 0.052* | |
H3 | 0.2241 | 0.3701 | −0.0282 | 0.052* | |
H4 | 0.2955 | 0.1193 | 0.3220 | 0.039* | |
H5 | 0.2875 | 0.0426 | 0.2136 | 0.038* | |
H6 | 0.3435 | 0.1148 | 0.2339 | 0.038* | |
H7 | 0.1814 | 0.1361 | 0.3402 | 0.050* | |
H8 | 0.1263 | 0.1071 | 0.2748 | 0.051* | |
H9 | 0.1830 | 0.0458 | 0.2394 | 0.051* | |
H10 | −0.0269 | 0.1298 | 0.5374 | 0.053* | |
H11 | −0.0222 | 0.0429 | 0.6402 | 0.053* | |
H12 | −0.0787 | 0.1113 | 0.6153 | 0.053* | |
H13 | 0.0885 | 0.0424 | 0.6194 | 0.047* | |
H14 | 0.0802 | 0.1160 | 0.5094 | 0.047* | |
H15 | 0.1384 | 0.1181 | 0.5696 | 0.048* | |
H16 | 0.1032 | 0.3947 | 0.9533 | 0.062* | |
H17 | 0.0936 | 0.4547 | 0.8373 | 0.062* | |
H18 | 0.0485 | 0.3651 | 0.8865 | 0.062* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
S1 | 0.0247 (5) | 0.0394 (6) | 0.0285 (5) | 0.0000 | 0.0005 (4) | 0.0000 |
S2 | 0.0291 (5) | 0.0286 (5) | 0.0260 (5) | 0.0000 | 0.0014 (4) | 0.0000 |
P1 | 0.0313 (6) | 0.0552 (8) | 0.0256 (5) | 0.0000 | 0.0052 (4) | 0.0000 |
P2 | 0.0225 (4) | 0.0256 (5) | 0.0221 (4) | 0.0000 | −0.0006 (4) | 0.0000 |
P3 | 0.0223 (5) | 0.0340 (6) | 0.0267 (5) | 0.0000 | −0.0010 (4) | 0.0000 |
P4 | 0.0243 (5) | 0.0497 (7) | 0.0345 (6) | 0.0000 | 0.0010 (5) | 0.0000 |
P5 | 0.0239 (5) | 0.0413 (7) | 0.0290 (5) | 0.0000 | −0.0005 (4) | 0.0000 |
P6 | 0.0299 (6) | 0.0857 (11) | 0.0309 (6) | 0.0000 | −0.0038 (5) | 0.0000 |
F1 | 0.056 (3) | 0.331 (10) | 0.041 (2) | 0.0000 | −0.021 (2) | 0.0000 |
F2 | 0.071 (2) | 0.400 (9) | 0.077 (2) | 0.076 (3) | −0.002 (2) | −0.108 (4) |
F3 | 0.060 (2) | 0.098 (3) | 0.165 (4) | 0.030 (2) | 0.040 (2) | −0.012 (3) |
F4 | 0.065 (3) | 0.174 (6) | 0.129 (5) | 0.0000 | −0.062 (3) | 0.0000 |
O1 | 0.054 (2) | 0.046 (2) | 0.086 (2) | 0.015 (1) | −0.012 (2) | −0.005 (2) |
O2 | 0.031 (2) | 0.067 (3) | 0.036 (2) | 0.0000 | −0.007 (1) | 0.0000 |
O3 | 0.077 (3) | 0.092 (4) | 0.032 (2) | 0.0000 | −0.016 (2) | 0.0000 |
O4 | 0.061 (2) | 0.041 (2) | 0.063 (2) | −0.005 (1) | 0.014 (1) | 0.014 (1) |
C1 | 0.061 (2) | 0.039 (2) | 0.029 (2) | −0.005 (2) | −0.003 (2) | 0.005 (1) |
C2 | 0.032 (1) | 0.030 (2) | 0.034 (1) | 0.0038 (12) | −0.0018 (12) | 0.0026 (12) |
C3 | 0.034 (2) | 0.033 (2) | 0.059 (2) | −0.0021 (13) | 0.008 (2) | 0.008 (2) |
C4 | 0.032 (2) | 0.043 (2) | 0.059 (2) | −0.001 (1) | −0.007 (2) | 0.000 (2) |
C5 | 0.033 (2) | 0.045 (2) | 0.040 (2) | 0.004 (1) | 0.0031 (13) | −0.001 (2) |
C6 | 0.067 (3) | 0.053 (2) | 0.035 (2) | −0.019 (2) | −0.003 (2) | −0.002 (2) |
C7 | 0.035 (3) | 0.26 (1) | 0.029 (3) | 0.0000 | −0.005 (2) | 0.0000 |
C9 | 0.030 (3) | 0.073 (5) | 0.086 (5) | 0.0000 | 0.005 (3) | 0.0000 |
Geometric parameters (Å, º) top
S1—O1 | 1.429 (3) | F4—C9 | 1.36 (1) |
S1—O2 | 1.435 (4) | C1—H1 | 0.9500 |
S1—C7 | 1.809 (7) | C1—H2 | 0.9500 |
S2—O3 | 1.422 (4) | C1—H3 | 0.9501 |
S2—O4 | 1.431 (3) | C2—H4 | 0.9500 |
S2—C9 | 1.801 (6) | C2—H5 | 0.9500 |
P1—P2 | 2.190 (2) | C2—H6 | 0.9499 |
P2—P3 | 2.214 (1) | C3—H7 | 0.9501 |
P1—C1 | 1.842 (4) | C3—H8 | 0.9500 |
P2—C2 | 1.793 (3) | C3—H9 | 0.9500 |
P3—C3 | 1.830 (4) | C4—H10 | 0.9500 |
P5—P6 | 2.187 (2) | C4—H11 | 0.9500 |
P4—P5 | 2.211 (2) | C4—H12 | 0.9499 |
P6—C6 | 1.828 (4) | C5—H13 | 0.9501 |
P5—C5 | 1.797 (4) | C5—H14 | 0.9500 |
P4—C4 | 1.839 (4) | C5—H15 | 0.9500 |
F1—C7 | 1.313 (8) | C6—H16 | 0.9500 |
F2—C7 | 1.299 (7) | C6—H17 | 0.9501 |
F3—C9 | 1.314 (6) | C6—H18 | 0.9501 |
| | | |
O1i—S1—O1 | 113.8 (2) | P1—C1—H3 | 109.4866 |
O2—S1—O1 | 115.4 (2) | P2—C2—H4 | 109.4204 |
C7—S1—O1 | 103.3 (2) | P2—C2—H5 | 109.5124 |
C7—S1—O2 | 103.4 (3) | P2—C2—H6 | 109.4839 |
S1—C7—F1 | 112.1 (5) | P3—C3—H7 | 109.5619 |
S1—C7—F2 | 110.7 (4) | P3—C3—H9 | 109.3910 |
O4—S2—O3 | 114.3 (2) | P3—C3—H8 | 109.4549 |
C9—S2—O3 | 104.5 (3) | P4—C4—H10 | 109.3786 |
O4i—S2—O4 | 115.0 (2) | P4—C4—H11 | 109.5485 |
C9—S2—O4 | 103.3 (2) | P4—C4—H12 | 109.4839 |
S2—C9—F3 | 112.2 (3) | P5—C5—H15 | 109.5405 |
S2—C9—F4 | 108.3 (5) | P5—C5—H13 | 109.4586 |
P1—P2—P3 | 108.77 (6) | P5—C5—H14 | 109.4083 |
P1—P2—C2 | 107.3 (1) | P6—C6—H18 | 109.3889 |
P2—P3—C3 | 100.2 (1) | P6—C6—H17 | 109.4726 |
C1—P1—P2 | 98.4 (1) | P6—C6—H16 | 109.5483 |
C2—P2—P3 | 113.2 (1) | H2—C1—H1 | 109.4710 |
C1i—P1—C1 | 100.3 (2) | H3—C1—H1 | 109.4783 |
C2i—P2—C2 | 106.9 (2) | H3—C1—H2 | 109.4663 |
C3i—P3—C3 | 100.4 (2) | H5—C2—H4 | 109.4699 |
P4—P5—P6 | 108.17 (7) | H6—C2—H4 | 109.4677 |
C5—P5—P6 | 107.6 (1) | H6—C2—H5 | 109.4729 |
C4—P4—P5 | 100.1 (1) | H9—C3—H7 | 109.4754 |
P5—P6—C6 | 98.1 (1) | H8—C3—H7 | 109.4750 |
P4—P5—C5 | 113.2 (1) | H9—C3—H8 | 109.4691 |
C6i—P6—C6 | 101.6 (2) | H11—C4—H10 | 109.4738 |
C5i—P5—C5 | 106.7 (2) | H12—C4—H10 | 109.4735 |
C4i—P4—C4 | 101.5 (2) | H12—C4—H11 | 109.4690 |
F1—C7—F2 | 108.8 (4) | H15—C5—H13 | 109.4784 |
F2—C7—F2i | 105.4 (6) | H14—C5—H13 | 109.4729 |
F3—C9—F3i | 108.3 (6) | H15—C5—H14 | 109.4686 |
F3—C9—F4 | 107.8 (4) | H18—C6—H16 | 109.4776 |
P1—C1—H1 | 109.4466 | H17—C6—H16 | 109.4685 |
P1—C1—H2 | 109.4784 | H18—C6—H17 | 109.4713 |
| | | |
O1—S1—C7—F1 | −59.4 (4) | C1—P1—P2—P3 | 50.9 (3) |
O1—S1—C7—F2 | 178.9 (4) | C1—P1—P2—C2 | 173.6 (2) |
O2—S1—C7—F1 | 180.0 | P1—P2—P3—C3 | 128.7 (2) |
O2—S1—C7—F2 | 58.3 (5) | C2—P2—P3—C3 | 9.6 (2) |
O3—S2—C9—F3 | −61.1 (6) | C4—P4—P5—P6 | −128.1 (2) |
O3—S2—C9—F4 | 180.0 | C4—P4—P5—C5 | −8.9 (2) |
O4—S2—C9—F3 | 58.8 (6) | P4—P5—P6—C6 | −51.5 (3) |
O4—S2—C9—F4 | −60.1 (4) | C5—P5—P6—C6 | −174.2 (2) |
Symmetry code: (i) x, −y+1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H4···O3 | 0.95 | 2.56 | 3.380 (5) | 145 |
C2—H5···O4ii | 0.95 | 2.27 | 3.222 (5) | 177 |
C2—H6···O1iii | 0.95 | 2.46 | 3.402 (4) | 173 |
C5—H13···O1iv | 0.95 | 2.31 | 3.258 (5) | 173 |
C5—H14···O2 | 0.95 | 2.60 | 3.429 (5) | 146 |
C3—H8···F2 | 0.95 | 2.77 | 3.491 (5) | 134 |
C6—H16···F2v | 0.95 | 2.73 | 3.295 (5) | 119 |
Symmetry codes: (ii) −x+1/2, −y, z−1/2; (iii) x+1/2, −y+1/2, −z+1/2; (iv) −x, y−1/2, −z+1; (v) x, −y+1/2, z+1. |
Experimental details
Crystal data |
Chemical formula | C6H18P3+·CF3O3S− |
Mr | 332.19 |
Crystal system, space group | Orthorhombic, Pnma |
Temperature (K) | 123 |
a, b, c (Å) | 23.5972 (7), 10.7419 (4), 12.0086 (4) |
V (Å3) | 3043.9 (2) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.55 |
Crystal size (mm) | 0.40 × 0.17 × 0.12 |
|
Data collection |
Diffractometer | Rigaku R-AXIS diffractometer |
Absorption correction | – |
No. of measured, independent and observed [F2 > 2σ(F2)] reflections | 25123, 6230, 2682 |
Rint | 0.080 |
(sin θ/λ)max (Å−1) | 0.820 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.052, 0.063, 1.06 |
No. of reflections | 2682 |
No. of parameters | 193 |
No. of restraints | ? |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 1.08, −0.62 |
Selected geometric parameters (Å, º) topP1—P2 | 2.190 (2) | P4—P5 | 2.211 (2) |
P2—P3 | 2.214 (1) | P6—C6 | 1.828 (4) |
P1—C1 | 1.842 (4) | P5—C5 | 1.797 (4) |
P2—C2 | 1.793 (3) | P4—C4 | 1.839 (4) |
P3—C3 | 1.830 (4) | F1—C7 | 1.313 (8) |
P5—P6 | 2.187 (2) | F2—C7 | 1.299 (7) |
| | | |
P1—P2—P3 | 108.77 (6) | P4—P5—P6 | 108.17 (7) |
P1—P2—C2 | 107.3 (1) | C5—P5—P6 | 107.6 (1) |
P2—P3—C3 | 100.2 (1) | C4—P4—P5 | 100.1 (1) |
C1—P1—P2 | 98.4 (1) | P5—P6—C6 | 98.1 (1) |
C2—P2—P3 | 113.2 (1) | P4—P5—C5 | 113.2 (1) |
C1i—P1—C1 | 100.3 (2) | C6i—P6—C6 | 101.6 (2) |
C2i—P2—C2 | 106.9 (2) | C5i—P5—C5 | 106.7 (2) |
C3i—P3—C3 | 100.4 (2) | C4i—P4—C4 | 101.5 (2) |
Symmetry code: (i) x, −y+1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
C2—H4···O3 | 0.95 | 2.56 | 3.380 (5) | 145 |
C2—H5···O4ii | 0.95 | 2.27 | 3.222 (5) | 177 |
C2—H6···O1iii | 0.95 | 2.46 | 3.402 (4) | 173 |
C5—H13···O1iv | 0.95 | 2.31 | 3.258 (5) | 173 |
C5—H14···O2 | 0.95 | 2.60 | 3.429 (5) | 146 |
C3—H8···F2 | 0.95 | 2.77 | 3.491 (5) | 134 |
C6—H16···F2v | 0.95 | 2.73 | 3.295 (5) | 119 |
Symmetry codes: (ii) −x+1/2, −y, z−1/2; (iii) x+1/2, −y+1/2, −z+1/2; (iv) −x, y−1/2, −z+1; (v) x, −y+1/2, z+1. |
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P-donor ligands on PIII systems have recently become pivotal in the development of molecular main-group coordination chemistry. These donor–acceptor interactions are recognized as `homoatomic' coordination complexes in inter- and intramolecular phosphine–phosphonium complexes and are essentially unique to phosphorus (Burford et al., 2003). Facile synthetic methods for the diversification of catena-polyphosphorus cations yielded a series of new organo-substituted diphosphinophosphonium and cyclo-tetraphosphinodiphosphonium cations (Weigand et al., 2006). Recently, we reported the crystal structure of catena-hexamethyldiphosphinophosphonium trifluoromethanesulfonate, which crystallizes in the monoclinic crystal system P21/c (Burford et al., 2005). During our further investigation we obtained a second polymorph of the title compound, (I) [OTf- is trifluoromethanesulfonate (trifluoromethanesulfonate)], by chance, from the reaction of 1,3-bis(2,6-dimethylphenyl)-2,4-ditriflato-1,3,2,4-diazadiphosphetidine with tetramethyldiphosphine as a reaction by-product.
The orthorhombic polymorph crystallizes with two half-formula units in the asymmetric unit. A view of the molecular structures along with the numbering scheme is depicted in Fig. 1. X-ray investigation has shown that the bond lengths in (I) do not significantly differ from that found in the monoclinic polymorph. The same unusual eclipsed/staggered conformation (local molecular symmetry Cs) of the cation is observed. The geometries of the trifluoromethanesulfonate anions in (I) are in accordance with that previously determined (You & Zhu, 2004). The interatomic distances and bond angles in the two independent molecules are almost identical, and selected molecular parameters of the cations are presented in Table 1. The cations and anions lie across a crystallographic mirror plane passing through atoms P1–P6, S1, S2, C7 and C9.
Compound (I) lacks traditional hydrogen-bond donor groups; hence, the structure is stabilized by weak C—H···O and C—H···F interactions (Table 2). These C—H···O hydrogen bonds (C2—H4···O3, C2—H6···O1iii and C5—H14···O2; symmetry codes and geometry are given in Table 2) account for the observation of subunits consisting of two cations and two anions, and, together with the weak C—H···F interactions (C3—H8···F2 and C6—H16···F2v; Table 2), form two-dimensional sheets (Fig. 2). The two hydrogen bonds found between these sheets (C2—H5···O4ii and C5—H13···O1iv; Table 2) are the main contributors that lead to a lateral packing of the layers. The resulting layers are arranged in an antiparallel manner (ABA layer sequence), which is compatible with space group Pnma (Fig. 3). In the case of the monoclinic polymorph, a lateral packing of layers is found, similar to that of the orthorhombic polymorph. However, the layers are composed of alternating strands of cations and anions running along the c axis, stabilized by weak C—H···O and C—H···F interactions.