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The structure of (Et4N)2[Hg3Br8] contains isolated dinuclear [Hg2Br6]2- anions and neutral HgBr2 mol­ecules. Charge balance is achieved by ordered [Et4N]+ cations. The formula may therefore be written as (Et4N)2[Hg2Br6][HgBr2]. The N atoms of the (Et4N)+ ions lie on a \overline 4 axis along [001] and, whereas one of the mercury(II) ions is placed on a mirror plane perpendicular to the c axis, the second one is located on a special position of site symmetry 2/m.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536802015301/bt6185sup1.cif
Contains datablocks I, global

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536802015301/bt6185Isup2.hkl
Contains datablock I

CCDC reference: 198297

Key indicators

  • Single-crystal X-ray study
  • T = 293 K
  • Mean [sigma](C-C) = 0.015 Å
  • R factor = 0.034
  • wR factor = 0.088
  • Data-to-parameter ratio = 22.7

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Red Alert Alert Level A:
DIFF_020 Alert A _diffrn_standards_interval_count and _diffrn_standards_interval_time are missing. Number of measurements between standards or time (min) between standards.
Yellow Alert Alert Level C:
RINTA_01 Alert C The value of Rint is greater than 0.10 Rint given 0.116
1 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
1 Alert Level C = Please check

Comment top

The crystal structures of several halogenomercurates(II) have been reported and show a wide variety of stereochemical arrangements, as listed in a recent overview (Serezhkin et al., 2001). With simple cations, such as NH4+ or alkali metals, the `characteristic' coordination of mercury (Grdenić, 1965) is usually digonal, with Br—Hg—Br quasi-molecules. The coordination of mercury is then often completed to an `effective' [2 + 4] distorted octahedron, with two covalent bonds and four additional Br atoms which are significantly further away, but still within the sum of the van der Waals radii. A typical example is (NH4)4HgBr6 with isolated [2 + 4] octahedra of Br surrounding Hg2+ (Nockemann & Meyer, 2001).

The crystal structure of (Et4N)2[Hg2Br6] contains isolated bitetrahedral [Hg2Br6]2− units consisting of two tetrahedra sharing one common edge (Nockemann & Meyer, 2002). Another compound in the (Et4N)Br/HgBr2 system is (Et4N)2[HgBr4], which consists of isolated [HgBr4]2− tetrahedra (Dean, Vittal & Wu, 1993).

The structure of (Et4N)2[Hg3Br8] or `(Et4N)2[Hg2Br6][HgBr2]', (I), consists of isolated bitetrahedral [Hg2Br6]2− units consisting of two tetrahedra sharing one common edge and further contains molecular digonal Br—Hg—Br units. The bitetrahedral [Hg2Br6]2− units exhibit two short bonds of 2.5171 (16) and 2.5334 (17) Å, and two long bonds to the bridging Br ions of 2.7553 (9) Å. The coordination sphere of the diagonal Br—Hg—Br unit [Hg—Br 2.3885 (14) Å] is completed to a distorted octahedron with an `effective' [2 + 2+2] coordination by two long Hg···Br contacts of approximately 3.458 Å, and two very long Hg···Br contacts of approximately 3.836 Å, as shown in Fig. 2. In (Et4N)2[Hg3Br8] charge balance is achieved by ordered [Et4N]+ cations, which are located between the [Hg2Br6][HgBr2] layers. The distance between these layers amounts to half of the c axis.

Experimental top

1 mmol (0.1717 g) of tetraethylammonium bromide, (Et4)NBr, and 3 mmol (0.8145 g) of mercuric bromide, HgBr2, were dissolved by stirring in 50 ml me thanol at 323 K until a clear solution was obtained. Single crystals were obtained when the solution was allowed to sit at room temperature for 2 d.

Computing details top

Data collection: X-AREA (Stoe & Cie, 2001); cell refinement: X-STEP (Stoe & Cie, 2000); data reduction: X-RED (Stoe & Cie, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. Packing diagram of (Et4N)2[Hg3Br8], viewed down the a axis.
[Figure 2] Fig. 2. Bitetrahedral [Hg2Br6]2− units sharing one common edge and their distances to the HgBr2 units.
[Figure 3] Fig. 3. One view of the [Et4N]+ cation.
[Figure 4] Fig. 4. A second view of the [Et4N]+ cation.
(I) top
Crystal data top
(C8H20N)2[Hg2Br6][HgBr2]Dx = 3.044 Mg m3
Mr = 1501.55Mo Kα radiation, λ = 0.71073 Å
Tetragonal, P42/mCell parameters from 23650 reflections
Hall symbol: -P4cθ = 2.0–26.0°
a = 10.0888 (11) ŵ = 23.79 mm1
c = 16.094 (2) ÅT = 293 K
V = 1638.1 (3) Å3Prism, colourless
Z = 20.2 × 0.15 × 0.1 mm
F(000) = 1340
Data collection top
Stoe Imaging Plate Diffraction System (IPDS-I)
diffractometer
1681 independent reflections
Radiation source: fine-focus sealed tube1114 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.116
ϕ scansθmax = 26.0°, θmin = 2.0°
Absorption correction: numerical
(X-SHAPE; Stoe & Cie, 1998)
h = 1212
Tmin = 0.023, Tmax = 0.093k = 1211
23650 measured reflectionsl = 1919
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)] = 0.035H-atom parameters constrained
wR(F2) = 0.088 w = 1/[σ2(Fo2) + (0.0507P)2]
where P = (Fo2 + 2Fc2)/3
S = 0.91(Δ/σ)max < 0.001
1681 reflectionsΔρmax = 1.33 e Å3
74 parametersΔρmin = 0.84 e Å3
0 restraintsExtinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.0087 (4)
Crystal data top
(C8H20N)2[Hg2Br6][HgBr2]Z = 2
Mr = 1501.55Mo Kα radiation
Tetragonal, P42/mµ = 23.79 mm1
a = 10.0888 (11) ÅT = 293 K
c = 16.094 (2) Å0.2 × 0.15 × 0.1 mm
V = 1638.1 (3) Å3
Data collection top
Stoe Imaging Plate Diffraction System (IPDS-I)
diffractometer
1681 independent reflections
Absorption correction: numerical
(X-SHAPE; Stoe & Cie, 1998)
1114 reflections with I > 2σ(I)
Tmin = 0.023, Tmax = 0.093Rint = 0.116
23650 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0350 restraints
wR(F2) = 0.088H-atom parameters constrained
S = 0.91Δρmax = 1.33 e Å3
1681 reflectionsΔρmin = 0.84 e Å3
74 parameters
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
Hg10.46173 (6)0.18433 (6)0.00000.0584 (2)
Hg20.00000.50000.00000.0787 (3)
Br10.50000.00000.12403 (7)0.0530 (3)
Br20.65308 (14)0.34444 (14)0.00000.0533 (3)
Br30.21548 (16)0.23352 (17)0.00000.0667 (4)
Br40.00000.50000.14841 (8)0.0641 (4)
N10.00000.00000.25000.040 (3)
N20.50000.50000.25000.036 (3)
C10.1172 (11)0.1207 (10)0.3688 (6)0.059 (3)
H1C0.11690.20310.39870.071*
H1B0.20230.10790.34330.071*
H1A0.09980.04910.40660.071*
C20.0112 (13)0.1238 (11)0.3025 (8)0.070 (3)
H2B0.02860.19840.26600.084*
H2A0.07360.13960.32920.084*
C30.3207 (10)0.3232 (10)0.2369 (6)0.058 (2)
H3C0.27000.27520.19640.069*
H3B0.26190.37260.27210.069*
H3A0.37100.26200.27000.069*
C40.4135 (10)0.4167 (10)0.1935 (5)0.050 (2)
H4B0.36150.47570.15880.060*
H4A0.47050.36550.15710.060*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Hg10.0550 (4)0.0659 (4)0.0541 (3)0.0028 (3)0.0000.000
Hg20.1267 (9)0.0680 (6)0.0413 (4)0.0128 (6)0.0000.000
Br10.0653 (8)0.0571 (8)0.0367 (6)0.0011 (6)0.0000.000
Br20.0550 (8)0.0563 (8)0.0487 (6)0.0023 (6)0.0000.000
Br30.0546 (8)0.0776 (10)0.0678 (8)0.0149 (8)0.0000.000
Br40.0817 (10)0.0676 (9)0.0430 (6)0.0007 (8)0.0000.000
N10.033 (4)0.033 (4)0.055 (8)0.0000.0000.000
N20.036 (4)0.036 (4)0.034 (6)0.0000.0000.000
C10.060 (6)0.057 (6)0.061 (5)0.013 (5)0.001 (5)0.008 (5)
C20.080 (8)0.050 (6)0.081 (7)0.001 (6)0.003 (6)0.013 (5)
C30.051 (5)0.055 (6)0.066 (6)0.014 (5)0.003 (5)0.003 (5)
C40.057 (5)0.049 (5)0.043 (4)0.012 (4)0.004 (4)0.006 (4)
Geometric parameters (Å, º) top
Hg1—Br22.5171 (16)N1—C2iv1.513 (10)
Hg1—Br32.5334 (17)N1—C2v1.513 (10)
Hg1—Br1i2.7553 (9)N2—C41.515 (8)
Hg1—Br12.7553 (9)N2—C4vi1.515 (8)
Hg2—Br4ii2.3885 (14)N2—C4vii1.515 (8)
Hg2—Br42.3885 (14)N2—C4viii1.515 (8)
Br1—Hg1i2.7553 (9)C1—C21.511 (16)
N1—C21.513 (10)C3—C41.502 (13)
N1—C2iii1.513 (10)
Br2—Hg1—Br3128.79 (6)C2—N1—C2v108.2 (5)
Br2—Hg1—Br1i109.00 (3)C2iii—N1—C2v112.1 (10)
Br3—Hg1—Br1i105.64 (3)C2iv—N1—C2v108.2 (5)
Br2—Hg1—Br1109.00 (3)C4—N2—C4vi106.2 (7)
Br3—Hg1—Br1105.64 (3)C4—N2—C4vii111.1 (4)
Br1i—Hg1—Br192.84 (4)C4vi—N2—C4vii111.1 (4)
Br4ii—Hg2—Br4180.0C4—N2—C4viii111.1 (4)
Hg1i—Br1—Hg187.16 (4)C4vi—N2—C4viii111.1 (4)
C2—N1—C2iii108.2 (5)C4vii—N2—C4viii106.2 (7)
C2—N1—C2iv112.1 (10)C1—C2—N1115.5 (9)
C2iii—N1—C2iv108.2 (5)C3—C4—N2115.3 (7)
Symmetry codes: (i) x+1, y, z; (ii) x, y+1, z; (iii) y, x, z+1/2; (iv) x, y, z; (v) y, x, z+1/2; (vi) x+1, y+1, z; (vii) y+1, x, z+1/2; (viii) y, x+1, z+1/2.

Experimental details

Crystal data
Chemical formula(C8H20N)2[Hg2Br6][HgBr2]
Mr1501.55
Crystal system, space groupTetragonal, P42/m
Temperature (K)293
a, c (Å)10.0888 (11), 16.094 (2)
V3)1638.1 (3)
Z2
Radiation typeMo Kα
µ (mm1)23.79
Crystal size (mm)0.2 × 0.15 × 0.1
Data collection
DiffractometerStoe Imaging Plate Diffraction System (IPDS-I)
diffractometer
Absorption correctionNumerical
(X-SHAPE; Stoe & Cie, 1998)
Tmin, Tmax0.023, 0.093
No. of measured, independent and
observed [I > 2σ(I)] reflections
23650, 1681, 1114
Rint0.116
(sin θ/λ)max1)0.617
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.035, 0.088, 0.91
No. of reflections1681
No. of parameters74
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)1.33, 0.84

Computer programs: X-AREA (Stoe & Cie, 2001), X-STEP (Stoe & Cie, 2000), X-RED (Stoe & Cie, 2001), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), DIAMOND (Brandenburg, 1999), SHELXL97.

Selected geometric parameters (Å, º) top
Hg1—Br22.5171 (16)N1—C21.513 (10)
Hg1—Br32.5334 (17)N2—C41.515 (8)
Hg1—Br12.7553 (9)C1—C21.511 (16)
Hg2—Br42.3885 (14)C3—C41.502 (13)
Br2—Hg1—Br3128.79 (6)C2—N1—C2iii112.1 (10)
Br2—Hg1—Br1109.00 (3)C2iii—N1—C2iv108.2 (5)
Br3—Hg1—Br1105.64 (3)C4—N2—C4v106.2 (7)
Br1i—Hg1—Br192.84 (4)C4v—N2—C4vi111.1 (4)
Br4ii—Hg2—Br4180.0C1—C2—N1115.5 (9)
Hg1i—Br1—Hg187.16 (4)C3—C4—N2115.3 (7)
Symmetry codes: (i) x+1, y, z; (ii) x, y+1, z; (iii) x, y, z; (iv) y, x, z+1/2; (v) x+1, y+1, z; (vi) y+1, x, z+1/2.
 

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