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Dibromomethane, CH2Br2, and diiodomethane, CH2I2, have been in situ pressure-crystallized in a diamond–anvil cell and their structures determined by single-crystal X-ray diffraction at 0.61 and 0.16 GPa, respectively. The pressure-frozen CH2Br2 crystal is isostructural with its C2/c phase obtained by cooling. CH2I2 is known to form several phases at low temperature, one of which is isostructural with CH2Br2. However, pressure freezing leads to the polar Fmm2 phase. The formation of the polar CH2I2 structure at 0.16 GPa has been rationalized by the electrostatic and anisotropic van der Waals interactions of the I atoms. No ferroelectric behaviour of the Fmm2 polar phase II of CH2I2 has been determined. The diffraction, calorimetric and dielectric constant studies reveal considerable temperature hysteresis of transformations between the CH2I2 phases, as well as metastable regions strongly dependent on the sample shape and history.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768106034963/bk5037sup1.cif
Contains datablocks 1dbm, 1djm, 1djm_nis

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768106034963/bk50371dbm7sup2.hkl
Contains datablock 1dbm

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768106034963/bk50371djmsup3.hkl
Contains datablock 1djm

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768106034963/bk50371djm_nissup4.hkl
Contains datablock 1djm_nis

CCDC references: 629806; 629807; 629808

Computing details top

For all compounds, data collection: CrysAlis (Oxford Diffraction, 2004); cell refinement: CrysAlis (Oxford Diffraction, 2004); data reduction: CrysAlis (Oxford Diffraction, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: XP (Siemens, 1990); software used to prepare material for publication: SHELXL97 (Sheldrick, 1997).

Figures top
[Figure 1]
[Figure 2]
[Figure 3]
[Figure 4]
[Figure 5]
[Figure 6]
[Figure 7]
[Figure 8]
[Figure 9]
(1dbm) Dibromomethane top
Crystal data top
CH2Br2Dx = 3.173 Mg m3
Mr = 173.85Melting point: 221 K
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
a = 12.031 (2) ÅCell parameters from 1495 reflections
b = 4.3385 (9) Åθ = 5.1–30.1°
c = 14.795 (3) ŵ = 22.00 mm1
β = 109.51 (3)°T = 293 K
V = 727.9 (3) Å3Cylinder, colourless
Z = 80.47 × 0.47 × 0.10 mm
F(000) = 624
Data collection top
Kuma KM4CCD κ geometry
diffractometer
330 independent reflections
Radiation source: fine-focus sealed tube170 reflections with > 4σ(I)
Graphite monochromatorRint = 0.178
ω scansθmax = 30.1°, θmin = 5.1°
Absorption correction: analytical
Katrusiak, A. (2003). REDSHADE - Program for correcting reflections intensities for DAC absorption, gasket shadowing and sample crystal absorption. Adam Mickiewicz University, Poznań. Katrusiak, A. (2004). Z. Kristallogr. 219, 461-467
h = 1516
Tmin = 0.03, Tmax = 0.09k = 65
2222 measured reflectionsl = 1413
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)] = 0.068H-atom parameters constrained
wR(F2) = 0.149 w = 1/[σ2(Fo2) + (0.065P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.89(Δ/σ)max < 0.001
330 reflectionsΔρmax = 0.58 e Å3
25 parametersΔρmin = 0.57 e Å3
0 restraintsExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0017 (9)
Crystal data top
CH2Br2V = 727.9 (3) Å3
Mr = 173.85Z = 8
Monoclinic, C2/cMo Kα radiation
a = 12.031 (2) ŵ = 22.00 mm1
b = 4.3385 (9) ÅT = 293 K
c = 14.795 (3) Å0.47 × 0.47 × 0.10 mm
β = 109.51 (3)°
Data collection top
Kuma KM4CCD κ geometry
diffractometer
330 independent reflections
Absorption correction: analytical
Katrusiak, A. (2003). REDSHADE - Program for correcting reflections intensities for DAC absorption, gasket shadowing and sample crystal absorption. Adam Mickiewicz University, Poznań. Katrusiak, A. (2004). Z. Kristallogr. 219, 461-467
170 reflections with > 4σ(I)
Tmin = 0.03, Tmax = 0.09Rint = 0.178
2222 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0680 restraints
wR(F2) = 0.149H-atom parameters constrained
S = 0.89Δρmax = 0.58 e Å3
330 reflectionsΔρmin = 0.57 e Å3
25 parameters
Special details top

Experimental. High-pressure measurement at 0.61 GPa.

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*/Ueq
Br10.0797 (3)0.6831 (5)0.1273 (4)0.062 (4)
Br20.3469 (3)0.6580 (5)0.1305 (4)0.067 (4)
C10.206 (2)0.425 (3)0.127 (3)0.019 (4)*
H10.18120.29700.07010.023*
H20.22550.28940.18250.023*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Br10.048 (4)0.0584 (15)0.085 (11)0.0030 (14)0.030 (6)0.003 (2)
Br20.052 (4)0.0551 (15)0.105 (12)0.0050 (14)0.038 (7)0.005 (2)
Geometric parameters (Å, º) top
Br1—C11.888 (15)C1—H10.9700
Br2—C11.961 (16)C1—H20.9700
Br1—C1—Br2112.5 (7)Br1—C1—H2109.1
Br1—C1—H1109.1Br2—C1—H2109.1
Br2—C1—H1109.1H1—C1—H2107.8
(1djm) Diiodomethane top
Crystal data top
CH2I2Dx = 3.920 Mg m3
Mr = 267.83Melting point: 279 K
Orthorhombic, Fmm2Mo Kα radiation, λ = 0.71073 Å
a = 7.3128 (15) ÅCell parameters from 1073 reflections
b = 13.074 (3) Åθ = 3.1–29.2°
c = 4.7465 (9) ŵ = 13.64 mm1
V = 453.82 (16) Å3T = 293 K
Z = 4Cylinder, colourless
F(000) = 4560.43 × 0.43 × 0.09 mm
Data collection top
Kuma KM4CCD κ geometry
diffractometer
170 independent reflections
Radiation source: fine-focus sealed tube162 reflections with > 4σ(I)
Graphite monochromatorRint = 0.075
ω scansθmax = 29.2°, θmin = 3.1°
Absorption correction: analytical
Katrusiak, A. (2003). REDSHADE - Program for correcting reflections intensities for DAC absorption, gasket shadowing and sample crystal absorption. Adam Mickiewicz University, Poznań. Katrusiak, A. (2004). Z. Kristallogr. 219, 461-467
h = 33
Tmin = 0.11, Tmax = 0.26k = 1717
1030 measured reflectionsl = 66
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.026 w = 1/[σ2(Fo2) + (0.P)2 + 16.8177P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.076(Δ/σ)max = 0.015
S = 1.33Δρmax = 0.44 e Å3
170 reflectionsΔρmin = 0.54 e Å3
14 parametersExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
3 restraintsExtinction coefficient: 0.0123 (14)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.2 (7)
Crystal data top
CH2I2V = 453.82 (16) Å3
Mr = 267.83Z = 4
Orthorhombic, Fmm2Mo Kα radiation
a = 7.3128 (15) ŵ = 13.64 mm1
b = 13.074 (3) ÅT = 293 K
c = 4.7465 (9) Å0.43 × 0.43 × 0.09 mm
Data collection top
Kuma KM4CCD κ geometry
diffractometer
170 independent reflections
Absorption correction: analytical
Katrusiak, A. (2003). REDSHADE - Program for correcting reflections intensities for DAC absorption, gasket shadowing and sample crystal absorption. Adam Mickiewicz University, Poznań. Katrusiak, A. (2004). Z. Kristallogr. 219, 461-467
162 reflections with > 4σ(I)
Tmin = 0.11, Tmax = 0.26Rint = 0.075
1030 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.026H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.076 w = 1/[σ2(Fo2) + (0.P)2 + 16.8177P]
where P = (Fo2 + 2Fc2)/3
S = 1.33Δρmax = 0.44 e Å3
170 reflectionsΔρmin = 0.54 e Å3
14 parametersAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
3 restraintsAbsolute structure parameter: 0.2 (7)
Special details top

Experimental. High-pressure measurement at 0.16 GPa.

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*/Ueq
I10.00000.13600 (4)0.24295 (9)0.0475 (11)
C10.00000.00000.00375 (10)0.04 (3)
H10.11283 (15)0.00000.1265 (2)0.056*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.054 (3)0.0376 (7)0.0504 (8)0.0000.0000.0018 (18)
C10.06 (9)0.034 (11)0.029 (10)0.0000.0000.000
Geometric parameters (Å, º) top
I1—C12.1290 (7)C1—H11.0100 (2)
I1—C1—I1i113.27 (4)I1—C1—H1108.49 (4)
I1—C1—I1i113.27 (4)I1i—C1—H1108.49 (4)
I1i—C1—I1i0.000 (14)I1i—C1—H1108.49 (4)
Symmetry code: (i) x, y, z.
(1djm_nis) Diiodomethane top
Crystal data top
CH2I2Dx = 3.812 Mg m3
Mr = 267.83Melting point: 279 K
Orthorhombic, Fmm2Mo Kα radiation, λ = 0.71073 Å
a = 7.411 (3) ÅCell parameters from 596 reflections
b = 13.137 (4) Åθ = 3.1–29.1°
c = 4.7942 (15) ŵ = 13.26 mm1
V = 466.8 (3) Å3T = 2702 K
Z = 4Cylinder, colourless
F(000) = 4560.12 × 0.12 × 0.12 mm
Data collection top
Kuma KM-4-CCD
diffractometer
265 reflections with > 4σ(I)
Radiation source: fine-focus sealed tubeRint = 0.148
Graphite monochromatorθmax = 29.1°, θmin = 3.1°
ω scansh = 109
530 measured reflectionsk = 1017
298 independent reflectionsl = 66
Refinement top
Refinement on F2Hydrogen site location: inferred from neighbouring sites
Least-squares matrix: fullH atoms treated by a mixture of independent and constrained refinement
R[F2 > 2σ(F2)] = 0.063 w = 1/[σ2(Fo2) + (0.1205P)2 + 2.0615P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.177(Δ/σ)max = 0.006
S = 1.14Δρmax = 1.72 e Å3
298 reflectionsΔρmin = 2.10 e Å3
14 parametersExtinction correction: SHELXL, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
3 restraintsExtinction coefficient: 0.015 (3)
Primary atom site location: structure-invariant direct methodsAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
Secondary atom site location: difference Fourier mapAbsolute structure parameter: 0.6 (10)
Crystal data top
CH2I2V = 466.8 (3) Å3
Mr = 267.83Z = 4
Orthorhombic, Fmm2Mo Kα radiation
a = 7.411 (3) ŵ = 13.26 mm1
b = 13.137 (4) ÅT = 2702 K
c = 4.7942 (15) Å0.12 × 0.12 × 0.12 mm
Data collection top
Kuma KM-4-CCD
diffractometer
265 reflections with > 4σ(I)
530 measured reflectionsRint = 0.148
298 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.063H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.177Δρmax = 1.72 e Å3
S = 1.14Δρmin = 2.10 e Å3
298 reflectionsAbsolute structure: Flack H D (1983), Acta Cryst. A39, 876-881
14 parametersAbsolute structure parameter: 0.6 (10)
3 restraints
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*/Ueq
I10.00000.13523 (4)0.24218 (8)0.0509 (8)
C10.00000.00000.00326 (10)0.054 (8)
H10.11192 (14)0.00000.1235 (2)0.070*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
I10.0736 (11)0.0307 (9)0.0483 (10)0.0000.0000.0009 (15)
C10.11 (2)0.031 (14)0.025 (10)0.0000.0000.000
Geometric parameters (Å, º) top
I1—C12.1308 (8)C1—H11.0100 (3)
I1—C1—I1i112.96 (5)I1—C1—H1108.37 (4)
I1—C1—I1i112.96 (5)I1i—C1—H1108.37 (4)
I1i—C1—I1i0.000 (14)I1i—C1—H1108.37 (4)
Symmetry code: (i) x, y, z.

Experimental details

(1dbm)(1djm)(1djm_nis)
Crystal data
Chemical formulaCH2Br2CH2I2CH2I2
Mr173.85267.83267.83
Crystal system, space groupMonoclinic, C2/cOrthorhombic, Fmm2Orthorhombic, Fmm2
Temperature (K)2932932702
a, b, c (Å)12.031 (2), 4.3385 (9), 14.795 (3)7.3128 (15), 13.074 (3), 4.7465 (9)7.411 (3), 13.137 (4), 4.7942 (15)
α, β, γ (°)90, 109.51 (3), 9090, 90, 9090, 90, 90
V3)727.9 (3)453.82 (16)466.8 (3)
Z844
Radiation typeMo KαMo KαMo Kα
µ (mm1)22.0013.6413.26
Crystal size (mm)0.47 × 0.47 × 0.100.43 × 0.43 × 0.090.12 × 0.12 × 0.12
Data collection
DiffractometerKuma KM4CCD κ geometry
diffractometer
Kuma KM4CCD κ geometry
diffractometer
Kuma KM-4-CCD
diffractometer
Absorption correctionAnalytical
Katrusiak, A. (2003). REDSHADE - Program for correcting reflections intensities for DAC absorption, gasket shadowing and sample crystal absorption. Adam Mickiewicz University, Poznań. Katrusiak, A. (2004). Z. Kristallogr. 219, 461-467
Analytical
Katrusiak, A. (2003). REDSHADE - Program for correcting reflections intensities for DAC absorption, gasket shadowing and sample crystal absorption. Adam Mickiewicz University, Poznań. Katrusiak, A. (2004). Z. Kristallogr. 219, 461-467
Tmin, Tmax0.03, 0.090.11, 0.26
No. of measured, independent and
observed [ > 4σ(I)] reflections
2222, 330, 170 1030, 170, 162 530, 298, 265
Rint0.1780.0750.148
(sin θ/λ)max1)0.7060.6860.684
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.068, 0.149, 0.89 0.026, 0.076, 1.33 0.063, 0.177, 1.14
No. of reflections330170298
No. of parameters251414
No. of restraints033
H-atom treatmentH-atom parameters constrainedH atoms treated by a mixture of independent and constrained refinementH atoms treated by a mixture of independent and constrained refinement
w = 1/[σ2(Fo2) + (0.065P)2]
where P = (Fo2 + 2Fc2)/3
w = 1/[σ2(Fo2) + (0.P)2 + 16.8177P]
where P = (Fo2 + 2Fc2)/3
w = 1/[σ2(Fo2) + (0.1205P)2 + 2.0615P]
where P = (Fo2 + 2Fc2)/3
Δρmax, Δρmin (e Å3)0.58, 0.570.44, 0.541.72, 2.10
Absolute structure?Flack H D (1983), Acta Cryst. A39, 876-881Flack H D (1983), Acta Cryst. A39, 876-881
Absolute structure parameter?0.2 (7)0.6 (10)

Computer programs: CrysAlis (Oxford Diffraction, 2004), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), XP (Siemens, 1990).

 

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