Redetermination of Hg2I2

Kars, M.; Roisnel, T.; Dorcet, V.; Rebbah, A.; Carlos, O.-D.L.

doi:10.1107/S1600536811056339

inorganic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 68| Part 2| February 2012| Page i11

doi:10.1107/S1600536811056339

Open

access

Redetermination of Hg₂I₂

Mohammed Kars,^a ^* Thierry Roisnel,^b Vincent Dorcet,^b Allaoua Rebbah ^a and Otero-Diáz L. Carlos ^c

^aUniversité Houari-Boumedienne, Faculté de Chimie, Laboratoire Sciences des Matériaux, Bp 32 El-Alia Bab-Ezzouar, Algeria, ^bCentre de Diffractométrie X, Sciences Chimiques de Rennes, UMR 6226 CNRS Université de Rennes 1, Campus de Beaulieu, Avenue du Général Leclerc, France, and ^cDepartomento Inorgánica, Facultad C.C. Químicas, Universidad Complutense, 28040 Madrid, Spain
^*Correspondence e-mail: mkarsdz@yahoo.fr

(Received 21 November 2011; accepted 31 December 2011; online 7 January 2012)

The crystal structure of mercurous iodide, Hg₂I₂, has been determined previously from X-ray powder diffraction data [Havighurst (1926 ). J. Am. Chem. Soc. 48, 2113–2125]. The results of the current redetermination based on single-crystal X-ray diffraction data provide more precise geometrical data and also anisotropic displacement parameters for the Hg and I atoms, which are both situated on positions with site-symmetry 4mm. The structure consists of linear dimers I—Hg—Hg—I extending along the c axis with an Hg—Hg distance of 2.5903 (13) Å. The overall coordination sphere of the Hg⁺ atom is a considerably distorted octahedron. The crystal specimen under investigation was twinned by non-merohedry with a refined twin domain fraction of 0.853 (14):0.147 (14).

Related literature

The structures of the mercurous halides Hg₂X₂ (X = Cl, Br, I) were originally determined from X-ray powder data by Havighurst (1926). Studies based on single crystals for X = F, Cl, Br were reported by Dorm (1970 ) and for X = F also by Grdenić & Djordjević (1956 ) and Schrötter & Müller (1992 ). For the physical properties of mercurous halides, see: Zadokhin & Solodovnik (2004 ); Markov et al. (2007 , 2010 ); Taylor et al. (2011 ). For theoretical studies of the structures of mercurous halides, see: Liao & Zhang (1995 ); Liao & Schwarz (1997 ).

Experimental

Crystal data

Hg₂I₂
M_r = 654.98
Tetragonal, I 4/m m m
a = 4.8974 (9) Å
c = 11.649 (2) Å
V = 279.40 (9) Å³
Z = 2
Mo Kα radiation
μ = 65.76 mm⁻¹
T = 150 K
0.10 × 0.06 × 0.04 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (TWINABS; Bruker, 2006 ) T_min = 0.024, T_max = 0.072
448 measured reflections
253 independent reflections
164 reflections with I > 3σ(I)
R_int = 0.056

Refinement

R[F² > 3σ(F²)] = 0.039
wR(F²) = 0.044
S = 1.47
253 reflections
9 parameters
Δρ_max = 4.99 e Å⁻³
Δρ_min = −4.73 e Å⁻³

Table 1
Selected bond lengths (Å)

Hg1—I1	2.7266 (17)
Hg1—I1ⁱ	3.5000 (9)
Symmetry code: (i) $[-x-{\script{1\over 2}}, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ .

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT and CELL_NOW (Bruker, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999 ); program(s) used to refine structure: JANA2006 (Petříček et al., 2006 ); molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ); software used to prepare material for publication: JANA2006.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811056339/wm2566sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811056339/wm2566Isup2.hkl

checkCIF report

Comment top

Les cristaux d'halogénures de mercure(I) de formulation Hg₂X₂ (X = F, Cl, Br et I) sont connus pour leurs propriétés physiques anisotropes (acousto-optiques, biréfringences etc). Ces dernières années, ces composés ont fait l'objet de nombreux travaux, essentiellement pour leurs propriétés dynamiques (Zadokhin & Solodovnik, 2004), ferroélastiques (Markov et al. 2007, 2010) et résonnances magnétiques nucléaires (NMR) (Taylor et al., 2011). La présence de liaisons Hg—Hg, qui est l'une des caractéristiques de ce type de composé a suscité plusieurs études quant à la nature et aux propriétés de ces liaisons (Liao & Zhang, 1995; Liao & Schwarz, 1997). La structure de ces halogènures a été déterminée au préalable par diffraction des rayons X sur poudre (Havighurst, 1926), puis sur monocristal pour Hg₂X₂ (X: F, Cl et Br) par Dorm (1970) et pour Hg₂F₂ par Schrötter & Müller (1992). La structure de Hg₂I₂ est analogue à celle des autres halogènures, elle est caractérisée par des chaînes linéaires I—Hg—Hg—I le long de l'axe c (Fig. 1). A la différence des autres halogènures formés par les ions Hg₂⁺² et X^-, l'iodure de mercure(I) Hg₂I₂ quant à lui est caractérisé par des dimères 'HgI' (Grdenić & Djordjević, 1956).

La présente redétermination par diffraction des rayons X sur monocristal, fournit plus de précisions sur les distances interatomiques, ainsi que sur les paramètres d'agitation thermiques (ADP's). Les liaisons Hg—Hg [2.5903 (13) Å] et Hg—I [2.7266 (17) Å] sont différentes de celles observées par Havighurst (1926) [respectivement 2.694 et 2.682 Å]. Quatres longues distances Hg—I de 3.5000 (9) Å sont aussi observées, donnant aux atomes de Hg un environnement octadérique distordu (Fig. 2). Les résultats obtenus sur monocristal montrent une tendance des différentes liaisons à varier selon l'électronégativité de l'halogène (Havighurst, 1926). En effet, la liaison Hg—halogéne augmente du fluor à l'iode d'environ 0.58 et 0.78 Å respectivement pour la courte et la longue distance: Hg—F [2.14 (2) et 2.715 (5) Å]; Hg—Cl [2.43 (4) et 3.209 (6) Å]; Hg—Br [2.71 (2) et 3.32 (1) Å] et Hg—I [2.7266 (17) et 3.5000 (9) Å]; quant à liaison Hg—Hg, elle augmente seulement de 0.08 Å: F [2.507 (1) Å]; Cl [2.526 (6) Å]; Br [2.49 (1) Å] et I [2.5903 (13) Å]. Ceci contredit en partie les conclusions de Liao & Zhang, (1995) and Liao & Schwarz (1997), selon lesquelles la liaison Hg—Hg est indépendante de l'électronégativité de l'halogéne. Toutefois une redétermination structurale de Hg₂Br₂ semble nécessaire pour confirmer cette tendance. Enfin, il faut remarquer que comme pour les autres halogénures de mercures(I), l'agitation thermique (ADP's) autour du mercure U₁₁(Hg) est supérieure à U₃₃(Hg), alors qu'autour de l'iode elle est comparable à celles des autres halogènes.

Related literature top

The structures of the mercurous halides Hg₂X₂ (X = Cl, Br, I) were originally determined from X-ray powder data by Havighurst (1926). Studies based on single crystals for X = F, Cl, Br were reported by Dorm (1970) and for X = F also by Grdenić & Djordjević (1956) and Schrötter & Müller (1992). For the physical properties of mercurous halides, see: Zadokhin & Solodovnik (2004); Markov et al. (2007, 2010); Taylor et al. (2011). For theoretical studies of the structures of mercurous halides, see: Liao & Zhang (1995); Liao & Schwarz (1997).

Experimental top

Les monocristaux de Hg₂I₂ ont été obtenus lors des essais de synthèse du clathrate I₈Hg₁₀Ge₃₆, à partir d'un mélange d'éléments purs et en présence de HgO et WO₃ comme agents précurseurs. Le mélange broyé puis scellé dans un tube en quartz, est porté à une température de 1073 K pendant environ 10 jours. Des cristaux de la phase α-Ge ont été aussi identifiés.

Computing details top

Data collection: APEX2 (Bruker, 2006); cell refinement: SAINT (Bruker, 2006); data reduction: SAINT (Bruker, 2006) and CELL_NOW (Bruker, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: JANA2006 (Petříček et al., 2006); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: JANA2006 (Petříček et al., 2006).

Figures top

	Fig. 1. Structure de Hg₂I₂ montrant les chaînes linéaire I—Hg—Hg—I le long de l'axe c, avec un déplacement des ellipsoīdes à 80% de probabilité.
	Fig. 2. Environnement octaédrique distordu des atomes de Hg, avec un déplacement des ellipsoīdes à 80% de probabilité.

mercury(I) iodide top

Crystal data top

Hg₂I₂	D_x = 7.783 Mg m⁻³
M_r = 654.98	Mo Kα radiation, λ = 0.71073 Å
Tetragonal, I4/mmm	Cell parameters from 274 reflections
Hall symbol: -I 4 2	θ = 4.5–32.9°
a = 4.8974 (9) Å	µ = 65.76 mm⁻¹
c = 11.649 (2) Å	T = 150 K
V = 279.40 (9) Å³	Prism, black
Z = 2	0.10 × 0.06 × 0.04 mm
F(000) = 532

Data collection top

Bruker APEXII CCD diffractometer	253 independent reflections
Radiation source: X-ray tube	164 reflections with I > 3σ(I)
Graphite monochromator	R_int = 0.056
ω and ϕm scans	θ_max = 39.6°, θ_min = 3.5°
Absorption correction: multi-scan (TWINABS; Bruker, 2006)	h = −5→6
T_min = 0.024, T_max = 0.072	k = 0→8
448 measured reflections	l = 0→20

Refinement top

Refinement on F	0 constraints
R[F² > 2σ(F²)] = 0.039	Weighting scheme based on measured s.u.'s w = 1/(σ²(F) + 0.0001F²)
wR(F²) = 0.044	(Δ/σ)_max = 0.0003
S = 1.47	Δρ_max = 4.99 e Å⁻³
253 reflections	Δρ_min = −4.73 e Å⁻³
9 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
0 restraints	Extinction coefficient: 27 (7)

Crystal data top

Hg₂I₂	Z = 2
M_r = 654.98	Mo Kα radiation
Tetragonal, I4/mmm	µ = 65.76 mm⁻¹
a = 4.8974 (9) Å	T = 150 K
c = 11.649 (2) Å	0.10 × 0.06 × 0.04 mm
V = 279.40 (9) Å³

Data collection top

Bruker APEXII CCD diffractometer	253 independent reflections
Absorption correction: multi-scan (TWINABS; Bruker, 2006)	164 reflections with I > 3σ(I)
T_min = 0.024, T_max = 0.072	R_int = 0.056
448 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.039	9 parameters
wR(F²) = 0.044	0 restraints
S = 1.47	Δρ_max = 4.99 e Å⁻³
253 reflections	Δρ_min = −4.73 e Å⁻³

Special details top

Refinement. The refinement was carried out against all reflections. The conventional R-factor is always based on F. The goodness of fit as well as the weighted R-factor are based on F and F² for refinement carried out on F and F², respectively. The threshold expression is used only for calculating R-factors etc. and it is not relevant to the choice of reflections for refinement. The crystal studied was twinned by non-merohedry with a refined twin domain fraction of 0.853 (14): 0.147 (14). The program used for refinement, Jana2006, uses the weighting scheme based on the experimental expectations, see _refine_ls_weighting_details, that does not force S to be one. Therefore the values of S are usually larger than the ones from the SHELX program.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å²) top

	x	y	z	U_iso*/U_eq
Hg1	0	0	0.11118 (6)	0.0263 (2)
I1	0	0	0.34524 (10)	0.0207 (3)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Hg1	0.0356 (4)	0.0356 (4)	0.0078 (3)	0	0	0
I1	0.0271 (6)	0.0271 (6)	0.0079 (5)	0	0	0

Geometric parameters (Å, º) top

Hg1—Hg1ⁱ	2.5903 (13)	Hg1—I1ⁱⁱⁱ	3.5000 (9)
Hg1—I1	2.7266 (17)	Hg1—I1^iv	3.5000 (9)
Hg1—I1ⁱⁱ	3.5000 (9)	Hg1—I1^v	3.5000 (9)

Hg1ⁱ—Hg1—I1	180.0 (5)	I1^iv—Hg1—I1^v	88.795 (15)
Hg1ⁱ—Hg1—I1ⁱⁱ	98.34 (2)	Hg1—I1—Hg1ⁱⁱ	98.34 (2)
Hg1ⁱ—Hg1—I1ⁱⁱⁱ	98.34 (2)	Hg1—I1—Hg1ⁱⁱⁱ	98.34 (2)
Hg1ⁱ—Hg1—I1^iv	98.34 (2)	Hg1—I1—Hg1^iv	98.34 (2)
Hg1ⁱ—Hg1—I1^v	98.34 (2)	Hg1—I1—Hg1^v	98.34 (2)
I1—Hg1—I1ⁱⁱ	81.66 (2)	Hg1—I1—I1^vi	180.0 (5)
I1—Hg1—I1ⁱⁱⁱ	81.66 (2)	Hg1ⁱⁱ—I1—Hg1ⁱⁱⁱ	88.795 (16)
I1—Hg1—I1^iv	81.66 (2)	Hg1ⁱⁱ—I1—Hg1^iv	88.795 (16)
I1—Hg1—I1^v	81.66 (2)	Hg1ⁱⁱ—I1—Hg1^v	163.32 (4)
I1ⁱⁱ—Hg1—I1ⁱⁱⁱ	88.795 (15)	Hg1ⁱⁱ—I1—I1^vi	81.66 (2)
I1ⁱⁱ—Hg1—I1^iv	88.795 (15)	Hg1ⁱⁱⁱ—I1—Hg1^iv	163.32 (4)
I1ⁱⁱ—Hg1—I1^v	163.32 (4)	Hg1ⁱⁱⁱ—I1—Hg1^v	88.795 (16)
I1ⁱⁱⁱ—Hg1—I1^iv	163.32 (4)	Hg1ⁱⁱⁱ—I1—I1^vi	81.66 (2)
I1ⁱⁱⁱ—Hg1—I1^v	88.795 (15)	Hg1^iv—I1—Hg1^v	88.795 (16)

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

Experimental details

Crystal data
Chemical formula	Hg₂I₂
M_r	654.98
Crystal system, space group	Tetragonal, I4/mmm
Temperature (K)	150
a, c (Å)	4.8974 (9), 11.649 (2)
V (Å³)	279.40 (9)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	65.76
Crystal size (mm)	0.10 × 0.06 × 0.04

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Multi-scan (TWINABS; Bruker, 2006)
T_min, T_max	0.024, 0.072
No. of measured, independent and observed [I > 3σ(I)] reflections	448, 253, 164
R_int	0.056
(sin θ/λ)_max (Å⁻¹)	0.897

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.039, 0.044, 1.47
No. of reflections	253
No. of parameters	9
Δρ_max, Δρ_min (e Å⁻³)	4.99, −4.73

Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2006) and CELL_NOW (Bruker, 2006), SIR97 (Altomare et al., 1999), JANA2006 (Petříček et al., 2006), DIAMOND (Brandenburg & Putz, 2005).

Selected bond lengths (Å) top

Hg1—I1

2.7266 (17)

Hg1—I1ⁱ

3.5000 (9)

Symmetry code: (i) −x−1/2, y−1/2, −z+1/2.

References

Altomare, A., Burla, M. C., Camalli, M., Cascarano, G. L., Giacovazzo, C., Guagliardi, A., Moliterni, A. G. G., Polidori, G. & Spagna, R. (1999). J. Appl. Cryst. 32, 115–119. Web of Science CrossRef CAS IUCr Journals Google Scholar
Brandenburg, K. & Putz, H. (2005). DIAMOND. Crystal Impact GbR, Bonn, Germany. Google Scholar
Bruker (2006). APEX2, SAINT, CELL_NOW and TWINABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Dorm, E. (1970). J. Chem. Soc. D, pp. 466–467. Google Scholar
Grdenić, D. & Djordjević, C. (1956). J. Chem. Soc. pp. 1316–1319. Google Scholar
Havighurst, R. J. (1926). J. Am. Chem. Soc. 48, 2113–2125. CrossRef CAS Google Scholar
Liao, M. S. & Schwarz, W. H. E. (1997). J. Alloys Compd, 246, 124–130. CrossRef CAS Web of Science Google Scholar
Liao, M. S. & Zhang, Q. (1995). J. Mol. Struct. (THEOCHIM), 358, 195–203. CrossRef CAS Google Scholar
Markov, Yu. F., Knorr, K. & Roginski, E. M. (2007). Ferroelectrics, 359, 82–93. Web of Science CrossRef CAS Google Scholar
Markov, Yu. F., Roginski, E. M. & Wallacher, D. (2010). Bull. Russ. Acad. Sci. Phys. 74, 1198–1202. CrossRef Google Scholar
Petříček, V., Dušék, M. & Palatinus, L. (2006). JANA2006. Institute of Physics, Praha, Czech Republic. Google Scholar
Schrötter, F. & Müller, B. G. (1992). Z. Anorg. Allg. Chem. 618, 53–58. Google Scholar
Taylor, R. E., Bai, S. & Dybowski, C. (2011). J. Mol. Struct. 987, 193–198. Web of Science CrossRef CAS Google Scholar
Zadokhin, B. S. & Solodovnik, E. V. (2004). Phys. Solid State, 46, 2110–2114. Web of Science CrossRef CAS Google Scholar