Bis­(tri­methyl­ammonium) tetra­chloro­mercurate(II) at 343 K

In order to investigate a possible phase transition at 324 K in the title compound, (NHMe₃)₂[HgCl₄], the crystal structures at 295 and 343 K have been determined, using restrictions of the non-crystallographic site symmetry of the tri­methyl­ammonium (TrMA) ions. The hydrogen-bond network, namely N—H...Cl, undergoes a considerable change, by a 38° rotation of one of the TrMA cations about the N—H bond axis. This transition is shown to be a non-symmetry-breaking structural transition, which corresponds to a gradual loss of the orientational order of the TrMA cations.

Key indicators

• Single-crystal synchrotron study
• T = 343 K
• Mean [sigma](N-C) = 0.028 Å
• H-atom completeness 11%
• R factor = 0.051
• wR factor = 0.079
• Data-to-parameter ratio = 15.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



THETM_01  Alert B The value of sine(theta_max)/wavelength is less than 0.575
          Calculated sin(theta_max)/wavelength =    0.5600

Author response: A rapid loss of the scattered intensities at intermediate and high scattering angles upon raising the temperature from 295 towards 350 K is observed. Only about 55% from the unique reflection are observed, however that a very low threshold is used.

 Alert Level C:



ABSTM_02  Alert C The ratio of expected to reported Tmax/Tmin(RR') is < 0.90
          Tmin and Tmax reported:      0.474     0.695
          Tmin' and Tmax expected:      0.396     0.508
          RR' =      0.874
          Please check that your absorption correction is appropriate.

GOODF_01  Alert C The least squares goodness of fit parameter lies
          outside the range 0.80 <> 2.00
          Goodness of fit given =      2.300

PLAT_321  Alert C Check Hybridisation of  C(1A)  in solvent/ion           ?

PLAT_321  Alert C Check Hybridisation of  C(11A) in solvent/ion           ?

PLAT_321  Alert C Check Hybridisation of  C(12A) in solvent/ion           ?

PLAT_321  Alert C Check Hybridisation of  C(4A)  in solvent/ion           ?

PLAT_321  Alert C Check Hybridisation of  C(41A) in solvent/ion           ?

PLAT_321  Alert C Check Hybridisation of  C(42A) in solvent/ion           ?

PLAT_745  Alert C D-H     Calc   0.966(16), Rep     0.97000 ....    Missing s.u.
                     N1A  -H1A     1.555   1.555

PLAT_745  Alert C D-H     Calc   0.966(16), Rep     0.97000 ....    Missing s.u.
                     N1A  -H1A     1.555   1.555

PLAT_745  Alert C D-H     Calc   0.966(16), Rep     0.97000 ....    Missing s.u.
                     N1A  -H1A     1.555   1.555

PLAT_745  Alert C D-H     Calc     0.99(3), Rep     1.00000 ....    Missing s.u.
                     N2A  -H2A     1.555   1.555

PLAT_745  Alert C D-H     Calc     0.99(3), Rep     1.00000 ....    Missing s.u.
                     N2A  -H2A     1.555   1.555

PLAT_746  Alert C H...A   Calc   2.482(12), Rep     2.48000 ....    Missing s.u.
                     H1A  -CL1     1.555   3.666

PLAT_746  Alert C H...A   Calc   3.087(19), Rep     3.09000 ....    Missing s.u.
                     H1A  -CL2     1.555   3.656

PLAT_746  Alert C H...A   Calc   3.119(19), Rep     3.12000 ....    Missing s.u.
                     H1A  -CL3     1.555   3.656

PLAT_746  Alert C H...A   Calc     2.26(2), Rep     2.26000 ....    Missing s.u.
                     H2A  -CL1     1.555   4.656

PLAT_746  Alert C H...A   Calc   3.369(19), Rep     3.37000 ....    Missing s.u.
                     H2A  -CL4     1.555   4.666

General Notes



FORMU_01  There is a discrepancy between the atom counts in the
          _chemical_formula_sum and the formula from the _atom_site* data.
          Atom count from _chemical_formula_sum:C6 H20 Cl4 Hg1 N2
          Atom count from the _atom_site data:  C6 H2 Cl4 Hg1 N2

ABSMU_01  Radiation type not identified. Calculation of
          _exptl_absorpt_correction_mu not performed.

ABSTM_02  When printed, the submitted absorption T values will be replaced
          by the scaled T values. Since the ratio of scaled T's is
          identical to the ratio of reported T values, the scaling does
          not imply a change to the absorption corrections used in the
          study.
          Ratio of Tmax expected/reported      0.730
          Tmax scaled      0.508 Tmin scaled      0.346

CELLZ_01
         From the CIF: _cell_formula_units_Z    4
         From the CIF: _chemical_formula_sum  C6 H20 Cl4 Hg N2
         TEST: Compare cell contents of formula and atom_site data

         atom    Z*formula  cif sites diff
         C         24.00     24.00    0.00
         H         80.00      8.00   72.00
         Cl        16.00     16.00    0.00
         Hg         4.00      4.00    0.00
         N          8.00      8.00    0.00
          Difference between formula and atom_site contents detected.
          WARNING: H atoms missing from atom site list. Is this intentional?

CHEMW_03
         From the CIF: _cell_formula_units_Z                    4
         From the CIF: _chemical_formula_weight           462.63
         TEST: Calculate formula weight from _atom_site_*
         atom     mass    num     sum
         C        12.01    6.00   72.07
         H         1.01    2.00    2.02
         CL       35.45    4.00  141.81
         Hg      200.59    1.00  200.59
         N        14.01    2.00   28.01
         Calculated formula weight              444.50
          The ratio of given/expected molecular weight as calculated
          from the _atom_site* data lies outside
          the range 0.99 <> 1.01


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 18 Alert Level C = Please check

---

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: MACH3 in CAD-4 UNIX Software (Enraf-Nonius, 1998); data reduction: SAINT (Siemens, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: JANA2000 (Petricek & Dusek, 2000); molecular graphics: DIAMOND (Brandenburg, 1999) and ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: JANA2000.

trimethylammonium tetrachloromercurates(II)

Crystal data

(C3H10N)2[HgCl4]	F(000) = 872
Mr = 462.63	Dx = 1.991 Mg m^−3
Monoclinic, P1121/n	Synchrotron radiation, λ = 0.50000 Å
a = 18.741 (2) Å	Cell parameters from 25 reflections
b = 6.302 (2) Å	θ = 27.3–8.8°
c = 13.069 (3) Å	µ = 5.79 mm^−1
β = 90°	T = 343 K
V = 1542.8 (6) Å^3	Polyhedron, colorless
Z = 4	0.16 × 0.14 × 0.12 mm

Data collection

Huber four-circle Kappa diffractometer with Siemens SMART CCD area detector	2174 independent reflections
Si (111) monochromator	1191 reflections with I > 2σ(I)
Detector resolution: number of pixels: 1024 x 1024 (512 x 512 in binning mode), pixel size: 60 µm x 60 µm pixels mm^-1	Rint = 0.044
Rotation image scans	θmax = 16.3°, θmin = 1.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −19→20
Tmin = 0.474, Tmax = 0.695	k = −7→7
6993 measured reflections	l = −14→14

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F > 3σ(F)] = 0.051	H-atom parameters constrained
wR(F) = 0.079	w = 1/[σ^2(Fo^2) + (0.0876P)^2 + 1.1621P] where P = (Fo^2 + 2Fc^2)/3
S = 2.30	(Δ/σ)max < 0.001
1191 reflections	Δρmax = 1.90 e Å^−3
77 parameters	Δρmin = −0.96 e Å^−3
0 restraints	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.24 (5)

Special details

Experimental. During the crystal test on the F1 beamline (HASYLAB) we noticed that there is no single spot in the area corresponding to a theta higher than 20 degree, for different setting of diffractometer angles. The scans were made at theta equal 20 degree. This behavior is characteristic of this family of compounds.

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. 700–900 data frames were collected by 0.01° steps in ω-scans with a crystal-to-detector distance of 30 mm. Preliminary orientation matrices were obtained from the first 100 frames using SMART (Siemens, 1995). The collected frames were integrated using the respective preliminary orientation matrix, which was updated every 100 frames. The data were empirically corrected for absorption and other effects (absorption by air, glue material and glass capillary) using SADABS (Sheldrick, 1996). The cell constants were obtained from setting angles of 25 reflections with 8.89 < θ <27.70°(graphite-monochromator Mo—Kα radiation). The systematic extinctions were in accordance with the space group P21/n for the room temperature and 343 K data. Structure refinement were performed by full-matrix least squares on F² data using SHELXL97(Sheldrick, 1997). The non H-atoms were refined anisotropically, whereas H atoms were treated isotropically using appropriate rinding models.

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 (Ų)

	x	y	z	Uiso*/Ueq
Hg	0.34318 (2)	0.27039 (8)	0.24946 (14)	0.0722 (3)
CL1	0.3436 (2)	0.6832 (6)	0.2588 (7)	0.0709 (14)
CL2	0.4084 (5)	0.1961 (13)	0.0923 (7)	0.111 (3)
CL3	0.4135 (4)	0.1849 (10)	0.3993 (6)	0.087 (2)
CL4	0.2175 (2)	0.1760 (8)	0.2535 (11)	0.105 (2)
N1a	0.4869 (6)	0.1856 (18)	0.7570 (17)	0.086 (4)
H1a	0.5362 (6)	0.1457 (18)	0.7609 (17)	0.0513*
C1a	0.4778 (11)	0.280 (2)	0.652 (2)	0.123 (8)
C1/1a	0.4770 (11)	0.343 (3)	0.8415 (19)	0.123 (8)
C1/2a	0.4435 (11)	−0.016 (3)	0.7721 (19)	0.123 (8)
N2a	0.7727 (9)	0.272 (2)	0.0289 (15)	0.100 (5)
H2a	0.7924 (9)	0.307 (2)	0.0977 (15)	0.038*
C4a	0.7387 (12)	0.458 (4)	0.001 (3)	0.228 (16)
C4/1a	0.7269 (13)	0.098 (3)	0.048 (3)	0.228 (16)
C4/2a	0.8333 (13)	0.228 (3)	−0.028 (3)	0.228 (15)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Hg	0.0576 (5)	0.0872 (5)	0.0721 (5)	0.0009 (8)	0.0033 (8)	0.0074 (3)
CL1	0.072 (2)	0.0708 (19)	0.070 (3)	−0.008 (3)	0.012 (3)	0.0033 (14)
CL2	0.113 (6)	0.133 (6)	0.087 (5)	−0.017 (5)	0.020 (5)	0.035 (5)
CL3	0.092 (5)	0.098 (4)	0.070 (4)	0.003 (3)	−0.025 (4)	−0.001 (3)
CL4	0.053 (2)	0.117 (3)	0.145 (5)	0.035 (6)	0.007 (6)	0.000 (2)
N1a	0.037 (5)	0.1080 (18)	0.113 (10)	0.001 (4)	−0.0042 (17)	0.0243 (15)
C1a	0.108 (10)	0.140 (18)	0.122 (12)	0.020 (11)	0.005 (7)	0.034 (10)
C1/1a	0.092 (10)	0.147 (14)	0.130 (18)	−0.026 (11)	0.006 (9)	0.011 (8)
C1/2a	0.092 (10)	0.116 (13)	0.160 (18)	0.008 (11)	−0.018 (9)	0.000 (8)
N2a	0.105 (3)	0.107 (12)	0.088 (10)	−0.005 (3)	−0.008 (4)	0.001 (5)
C4a	0.11 (2)	0.43 (4)	0.152 (19)	−0.15 (2)	0.022 (15)	0.02 (2)
C4/1a	0.11 (2)	0.43 (4)	0.152 (19)	−0.15 (2)	0.022 (15)	0.02 (2)
C4/2a	0.11 (2)	0.43 (4)	0.152 (19)	−0.15 (2)	0.022 (15)	0.02 (2)

Geometric parameters (Å, º)

Hg—CL1	2.604 (4)	Cl1—H2a^ii	2.26 (2)
Hg—CL2	2.442 (10)	N1a—H1a	0.967 (16)
Hg—CL3	2.430 (7)	N1a—C1a	1.50 (3)
Hg—CL4	2.414 (4)	N2a—H2a	0.99 (3)
Cl1—H1a^i	2.482 (12)	N2a—C4a	1.40 (3)
CL1—Hg—CL2	104.1 (3)	C1a—N1a—C1/2a	112.9 (16)
CL1—Hg—CL3	101.4 (2)	C1/1a—N1a—C1/2a	112.9 (17)
CL1—Hg—CL4	102.68 (15)	H2a—N2a—C4a	103 (2)
CL2—Hg—CL3	110.9 (3)	H2a—N2a—C4/1a	103 (2)
CL2—Hg—CL4	117.5 (4)	H2a—N2a—C4/2a	103 (2)
CL3—Hg—CL4	117.3 (4)	C4a—N2a—C4/1a	114.9 (18)
H1a—N1a—C1a	106 (2)	C4a—N2a—C4/2a	115 (2)
H1a—N1a—C1/1a	106 (2)	C4/1a—N2a—C4/2a	114.9 (18)
H1a—N1a—C1/2a	105.7 (14)	CL1^iii—H2a—N2a	146.7 (15)
C1a—N1a—C1/1a	112.9 (13)

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

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1a—H1a···CL1^i	0.97	2.48	3.272 (12)	138
N1a—H1a···CL2^iv	0.97	3.09	3.699 (18)	124
N1a—H1a···CL3^iv	0.97	3.12	3.656 (17)	117
N2a—H2a···CL1^iii	1.00	2.26	3.13 (2)	147
N2a—H2a···CL4^v	1.00	3.37	3.97 (2)	121

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