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The title compound, calcium oxide-dialuminium trioxide-calcium dibromide-calcium dichloride hydrate (3/1/0.5/0.5/10), also formulated as Ca2Al(OH)6Br0.478Cl0.522·2H2O (dicalcium aluminium hydro­xide hemibromide hemichloride dihydrate), is a double-layered hydro­xide which belongs to the solid solution Ca2Al(OH)6BrxCl1-x·2H2O, where x can vary from 0 to 1. Chloride and bromide anions of the negatively charged interlayer [Br0.5Cl0.5·2H2O]- share statistically the same crystallographic site. Al3+ and Ca2+ cations are coordinated by six and seven O atoms, respectively. All water mol­ecules are bonded to Ca2+ cations and assume the seventh coordination position. Anions in the interlayer are surrounded by ten H atoms. Br- and Cl- are therefore connected to the main layer by ten hydrogen bonds, six of 2.74 (2) Å and four of 2.52 (5) Å, where the donors are hydroxyl groups and water mol­ecules, respectively. Like the chloride equivalent, the title compound is a 6R polytype with trigonal space group R\overline 3c and lattice parameters a = 5.7537 (4) Å and c = 48.108 (4) Å.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270100014025/iz1005sup1.cif
Contains datablocks I, 2c4a19

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270100014025/iz1005Isup2.hkl
Contains datablock I

Comment top

The title compound was studied in the course of our investigations on the phases called AFm, which are hydrated compounds formed in cimentitious pastes. Their structures are layered and constituted by positively charged main layers [Ca2Al(OH)6]+ and negatively charged interlayers [X–, nH2O]-, where X is one monovalent or half of a divalent anion and where n depends on the humidity. The chlorinated compound or Friedel's salt is of monoclinic symmetry (space group C2/c) at room temperature. It undergoes a structural transition at 308 K and becomes rhombohedral with space group R -3c and lattice parameters a = 5.724 Å and c = 46.689 Å (Renaudin et al., 1999). The c parameter corresponds to six inter-layers which are spaced at 7.78 Å (6R polytype). This transition is presumably related to the size of the inserted halide [r = 1.81 Å, 1.96 Å, 2.20 Å for Cl-, Br- and I-, respectively (Shannon, 1976)]. Indeed, the AFm-Br transforms at 223 K while AFm-I does not present structural change above 77 K. The structures of AFm-Br (Rapin, Mohamed Noor et al., 1999) and AFm-I (Rapin, Walcarius et al., 1999) have been determined by single-crystal diffraction experiments at room temperature. They are isostructural with space group R -3 and their c parameters correspond to three interlayers spacing (3R polytypes). In order to check the size effect of halide on the transition, the solid solution [Ca2Al(OH)6][BrxCl1 - x,2H2O] was studied. The transition temperature decreases linearly from 308 to 223 K when x increases from 0 to 1. In particular, the phase corresponding to x = 0.5 changes at 263 K. The single crystals of this phase are not twinned at room temperature, contrary to those of the pure chlorinated phase. The structure of the rhombohedral phase thus could be determined on single-crystal at room temperature. Anions Cl- and Br- share in a statistical disorder the same crystallographic site. The increase of the inter layer spacing from 7.78 (1) Å to 8.02 (1) Å going from x = 0 to x = 1/2, corresponds to the increase of the anionic radii tabulated by Shannon (1976) when Cl- is replaced by the larger halide Br-. The structure is represented in figure 1. The main layers of composition [Ca2Al(OH)6]- are brucite-like layers with an octahedral environment for Al3+ and a coordination up to seven for the Ca2+ cations. The seventh coordination is occupied by water molecules. In the inter layers spacing of composition (Br0.5, Cl0.5. 2H2O), the chloride and bromide anions are surrounded by ten hydrogen atoms, of which six belong to hydroxyl group and four to water molecules (see Fig. 2). Br- and Cl- anions are therefore connected to the main layer by ten hydrogen bonds, six of 2.74 (2) Å and four of 2.52 (5) Å, where the donors are hydroxyl groups and water molecules, respectively.

Related literature top

For related literature, see: Rapin, Mohamed Noor & François (1999); Rapin, Walcarius, Lefévre & François (1999); Renaudin et al. (1999); Shannon (1976).

Experimental top

Single crystals of the title compound were prepared by hydrothermal synthesis. The starting powders Ca(OH)2, Al(OH)3, CaCl2·6H2O and CaBr2·2H2O (molar proportion 2/1/0.5/0.5) are mixed with water (ratio solid/water = 1/2) and loaded in a silver capsule (length: 100 mm, diameter: 5 mm, thickness: 0.1 mm) sealed under Argon atmosphere. The experiment was performed during sixty days at 393 K and 2 kbar (1 bar = 10 5Pa).

Refinement top

Chlorine and bromine atoms were located on the same site. The sum of their occupancy factor is fixed at the unity. H atoms of hydroxyl group and water molecules were located from a difference Fourier map. The O—H distance is restrained to 0.95 Å, with a fixed individual isotropic displacement parameter Uiso = 1.2Ueq(O). The O atom (Ow) of the water molecule was located on a special site 12(c), whereas its H atom occupy then general site 36(f), with an occupancy factor of 2/3.

Computing details top

Data collection: COLLECT (Nonius, 1998); cell refinement: HKL SCALEPACK (Otwinowski & Minor 1997); data reduction: HKL DENZO and SCALEPACK; program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1995); software used to prepare material for publication: WINWORD (Version 5.0).

Figures top
[Figure 1] Fig. 1. The projection of the layered structure of the title compound along [110]. The polyhedral (AlO6) (shaded) and (CaO7) (unshaded) representation is produced using ATOMS (Dowty, 1995).
[Figure 2] Fig. 2. View of the halide hydrogen environment. HW atoms from water molecules are represented in an ordered way. Displacement ellipsoids of (Cl, Br) and H atoms are drawn at 70% probability level (ATOMS; Dowty, 1995). Symmetry codes as in Table 1.
(I) top
Crystal data top
AlBr0.478Ca2Cl0.522H10O8Dx = 2.182 Mg m3
Mr = 302.01Mo Kα radiation, λ = 0.71073 Å
Trigonal, R3cCell parameters from 25 reflections
Hall symbol: -R 3 2"cθ = 25–50°
a = 5.7537 (4) ŵ = 3.58 mm1
c = 48.108 (4) ÅT = 293 K
V = 1379.21 (18) Å3Plate, colorless
Z = 60.20 × 0.15 × 0.04 mm
F(000) = 916
Data collection top
Nonius B.V. Diffractometer516 independent reflections
Radiation source: fine-focus sealed tube390 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.035
CCD scansθmax = 31.4°, θmin = 2.5°
Absorption correction: empirical (using intensity measurements)
fitted by spherical harmonic functions (SORTAV; Blessing, 1995)
h = 88
Tmin = 0.48, Tmax = 0.86k = 88
8579 measured reflectionsl = 070
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.038Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.090H-atom parameters constrained
S = 1.05Weighting scheme based on measured s.u.'s w = 1/[σ2(Fo2) + (0.0151P)2 + 6.119P]
where P = (Fo2 + 2Fc2)/3
516 reflections(Δ/σ)max < 0.001
29 parametersΔρmax = 0.55 e Å3
3 restraintsΔρmin = 0.76 e Å3
Crystal data top
AlBr0.478Ca2Cl0.522H10O8Z = 6
Mr = 302.01Mo Kα radiation
Trigonal, R3cµ = 3.58 mm1
a = 5.7537 (4) ÅT = 293 K
c = 48.108 (4) Å0.20 × 0.15 × 0.04 mm
V = 1379.21 (18) Å3
Data collection top
Nonius B.V. Diffractometer516 independent reflections
Absorption correction: empirical (using intensity measurements)
fitted by spherical harmonic functions (SORTAV; Blessing, 1995)
390 reflections with I > 2σ(I)
Tmin = 0.48, Tmax = 0.86Rint = 0.035
8579 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0383 restraints
wR(F2) = 0.090H-atom parameters constrained
S = 1.05Δρmax = 0.55 e Å3
516 reflectionsΔρmin = 0.76 e Å3
29 parameters
Special details top

Experimental. The cristal to detector distance was of 40.0 (1) mm. 320 frames were recorded by oscillation method with an exposure time of 60 secondes per frame.

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*/UeqOcc. (<1)
Al0.00000.00000.00000.0136 (3)
Ca0.33330.66670.012218 (19)0.0161 (2)
Br0.66670.33330.08330.048 (3)0.478 (8)
Cl0.66670.33330.08330.061 (8)0.522 (8)
O0.3067 (3)0.2507 (3)0.02080 (4)0.0165 (4)
H0.329 (6)0.206 (6)0.0386 (4)0.021*
OW0.33330.66670.0640 (11)0.0539 (12)
HW0.438 (12)0.597 (7)0.0713 (13)0.066*0.6667
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Al0.0075 (4)0.0075 (4)0.0257 (9)0.0038 (2)0.0000.000
Ca0.0095 (2)0.0095 (2)0.0294 (5)0.00477 (12)0.0000.000
Br0.054 (3)0.054 (3)0.035 (4)0.0271 (13)0.0000.000
Cl0.085 (10)0.085 (10)0.011 (5)0.043 (5)0.0000.000
O0.0116 (7)0.0126 (8)0.0245 (9)0.0054 (6)0.0020 (6)0.001
OW0.0605 (19)0.0605 (19)0.041 (2)0.0303 (9)0.0000.000
Geometric parameters (Å, º) top
Al—O1.9105 (16)Ca—Oxi2.3568 (18)
Al—Oi1.9105 (16)Ca—O2.3568 (18)
Al—Oii1.9105 (16)Ca—Oxii2.4608 (18)
Al—Oiii1.9105 (16)Ca—Oiv2.4608 (18)
Al—Oiv1.9105 (16)Ca—Oviii2.4608 (18)
Al—Ov1.9105 (16)Ca—OW2.492 (5)
Al—Cavi3.3735 (3)Ca—Alxiii3.3735 (3)
Al—Cavii3.3735 (3)Ca—Alxiv3.3735 (3)
Al—Caiii3.3735 (3)Ca—Cavi3.5238 (6)
Al—Ca3.3735 (3)Ca—Caxv3.5238 (6)
Al—Caviii3.3735 (3)O—Caviii2.4607 (18)
Al—Caix3.3735 (3)O—H0.923 (18)
Ca—Ox2.3568 (18)OW—HW0.94 (2)
O—Al—Oi95.08 (7)Oxi—Ca—Oxii86.01 (6)
O—Al—Oii95.08 (7)O—Ca—Oxii146.73 (5)
Oi—Al—Oii95.08 (7)Ox—Ca—Oiv86.01 (6)
O—Al—Oiii180.0Oxi—Ca—Oiv146.73 (5)
Oi—Al—Oiii84.92 (7)O—Ca—Oiv64.71 (8)
Oii—Al—Oiii84.92 (7)Oxii—Ca—Oiv82.82 (7)
O—Al—Oiv84.92 (7)Ox—Ca—Oviii146.73 (5)
Oi—Al—Oiv84.92 (7)Oxi—Ca—Oviii64.71 (8)
Oii—Al—Oiv180.0O—Ca—Oviii86.01 (6)
Oiii—Al—Oiv95.08 (7)Oxii—Ca—Oviii82.82 (7)
O—Al—Ov84.92 (7)Oiv—Ca—Oviii82.82 (7)
Oi—Al—Ov180.0Ox—Ca—OW79.91 (5)
Oii—Al—Ov84.92 (7)Oxi—Ca—OW79.91 (5)
Oiii—Al—Ov95.08 (7)O—Ca—OW79.91 (5)
Oiv—Al—Ov95.08 (7)Oxii—Ca—OW130.20 (4)
O—Al—Cavi103.59 (5)Oiv—Ca—OW130.20 (4)
Oi—Al—Cavi45.87 (5)Oviii—Ca—OW130.20 (4)
Oii—Al—Cavi137.32 (5)Ox—Ca—Alxiii33.34 (4)
Oiii—Al—Cavi76.41 (5)Oxi—Ca—Alxiii94.94 (4)
Oiv—Al—Cavi42.68 (5)O—Ca—Alxiii147.24 (4)
Ov—Al—Cavi134.13 (5)Oxii—Ca—Alxiii33.87 (4)
O—Al—Cavii76.41 (5)Oiv—Ca—Alxiii93.00 (4)
Oi—Al—Cavii134.13 (5)Oviii—Ca—Alxiii116.14 (5)
Oii—Al—Cavii42.68 (5)OW—Ca—Alxiii100.034 (15)
Oiii—Al—Cavii103.59 (5)Ox—Ca—Al94.94 (4)
Oiv—Al—Cavii137.32 (5)Oxi—Ca—Al147.24 (4)
Ov—Al—Cavii45.87 (5)O—Ca—Al33.34 (4)
Cavi—Al—Cavii180.0Oxii—Ca—Al116.14 (5)
O—Al—Caiii137.32 (5)Oiv—Ca—Al33.87 (4)
Oi—Al—Caiii103.59 (5)Oviii—Ca—Al93.00 (4)
Oii—Al—Caiii45.87 (5)OW—Ca—Al100.034 (15)
Oiii—Al—Caiii42.68 (5)Alxiii—Ca—Al117.030 (9)
Oiv—Al—Caiii134.13 (5)Ox—Ca—Alxiv147.24 (4)
Ov—Al—Caiii76.41 (5)Oxi—Ca—Alxiv33.34 (4)
Cavi—Al—Caiii117.030 (9)O—Ca—Alxiv94.94 (4)
Cavii—Al—Caiii62.970 (9)Oxii—Ca—Alxiv93.00 (4)
O—Al—Ca42.68 (5)Oiv—Ca—Alxiv116.14 (5)
Oi—Al—Ca76.41 (5)Oviii—Ca—Alxiv33.87 (4)
Oii—Al—Ca134.13 (5)OW—Ca—Alxiv100.034 (15)
Oiii—Al—Ca137.32 (5)Alxiii—Ca—Alxiv117.030 (9)
Oiv—Al—Ca45.87 (5)Al—Ca—Alxiv117.030 (9)
Ov—Al—Ca103.59 (5)Ox—Ca—Cavi44.16 (4)
Cavi—Al—Ca62.970 (9)Oxi—Ca—Cavi152.56 (4)
Cavii—Al—Ca117.030 (9)O—Ca—Cavi90.30 (4)
Caiii—Al—Ca180.0Oxii—Ca—Cavi68.09 (4)
O—Al—Caviii45.87 (5)Oiv—Ca—Cavi41.85 (4)
Oi—Al—Caviii137.32 (5)Oviii—Ca—Cavi118.16 (6)
Oii—Al—Caviii103.59 (5)OW—Ca—Cavi109.49 (3)
Oiii—Al—Caviii134.13 (5)Alxiii—Ca—Cavi58.515 (4)
Oiv—Al—Caviii76.41 (5)Al—Ca—Cavi58.515 (4)
Ov—Al—Caviii42.68 (5)Alxiv—Ca—Cavi150.48 (4)
Cavi—Al—Caviii117.030 (9)Ox—Ca—Caxv90.30 (4)
Cavii—Al—Caviii62.970 (9)Oxi—Ca—Caxv44.16 (4)
Caiii—Al—Caviii117.030 (9)O—Ca—Caxv152.56 (4)
Ca—Al—Caviii62.970 (9)Oxii—Ca—Caxv41.85 (4)
O—Al—Caix134.13 (5)Oiv—Ca—Caxv118.16 (6)
Oi—Al—Caix42.68 (5)Oviii—Ca—Caxv68.09 (4)
Oii—Al—Caix76.41 (5)OW—Ca—Caxv109.49 (3)
Oiii—Al—Caix45.87 (5)Alxiii—Ca—Caxv58.515 (4)
Oiv—Al—Caix103.59 (5)Al—Ca—Caxv150.48 (4)
Ov—Al—Caix137.32 (5)Alxiv—Ca—Caxv58.515 (4)
Cavi—Al—Caix62.970 (9)Cavi—Ca—Caxv109.45 (3)
Cavii—Al—Caix117.030 (9)Al—O—Ca103.98 (8)
Caiii—Al—Caix62.970 (9)Al—O—Caviii100.26 (8)
Ca—Al—Caix117.030 (9)Ca—O—Caviii93.99 (6)
Caviii—Al—Caix180.0Al—O—H118.7 (19)
Ox—Ca—Oxi117.00 (3)Ca—O—H120.0 (19)
Ox—Ca—O117.00 (3)Caviii—O—H115.6 (19)
Oxi—Ca—O117.00 (3)Ca—OW—HW112 (4)
Ox—Ca—Oxii64.71 (8)
Symmetry codes: (i) y, xy, z; (ii) x+y, x, z; (iii) x, y, z; (iv) xy, x, z; (v) y, x+y, z; (vi) x, y+1, z; (vii) x, y1, z; (viii) x+1, y+1, z; (ix) x1, y1, z; (x) x+y, x+1, z; (xi) y+1, xy+1, z; (xii) y, x+y+1, z; (xiii) x, y+1, z; (xiv) x+1, y+1, z; (xv) x+1, y+2, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O—H···Br0.92 (2)2.74 (2)3.547 (3)146 (5)
OW—HW···Br0.94 (2)2.52 (5)3.449 (3)167 (9)

Experimental details

Crystal data
Chemical formulaAlBr0.478Ca2Cl0.522H10O8
Mr302.01
Crystal system, space groupTrigonal, R3c
Temperature (K)293
a, c (Å)5.7537 (4), 48.108 (4)
V3)1379.21 (18)
Z6
Radiation typeMo Kα
µ (mm1)3.58
Crystal size (mm)0.20 × 0.15 × 0.04
Data collection
DiffractometerNonius B.V. Diffractometer
Absorption correctionEmpirical (using intensity measurements)
fitted by spherical harmonic functions (SORTAV; Blessing, 1995)
Tmin, Tmax0.48, 0.86
No. of measured, independent and
observed [I > 2σ(I)] reflections
8579, 516, 390
Rint0.035
(sin θ/λ)max1)0.733
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.038, 0.090, 1.05
No. of reflections516
No. of parameters29
No. of restraints3
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.55, 0.76

Computer programs: COLLECT (Nonius, 1998), HKL SCALEPACK (Otwinowski & Minor 1997), HKL DENZO and SCALEPACK, SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 1995), WINWORD (Version 5.0).

Selected bond lengths (Å) top
Al—O1.9105 (16)Ca—O2.3568 (18)
Al—Oi1.9105 (16)Ca—Oviii2.4608 (18)
Al—Oii1.9105 (16)Ca—Oiv2.4608 (18)
Al—Oiii1.9105 (16)Ca—Oix2.4608 (18)
Al—Oiv1.9105 (16)Ca—OW2.492 (5)
Al—Ov1.9105 (16)O—H0.923 (18)
Ca—Ovi2.3568 (18)OW—HW0.94 (2)
Ca—Ovii2.3568 (18)
Symmetry codes: (i) y, xy, z; (ii) x+y, x, z; (iii) x, y, z; (iv) xy, x, z; (v) y, x+y, z; (vi) x+y, x+1, z; (vii) y+1, xy+1, z; (viii) y, x+y+1, z; (ix) x+1, y+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O—H···Br0.92 (2)2.74 (2)3.547 (3)146 (5)
OW—HW···Br0.94 (2)2.52 (5)3.449 (3)167 (9)
 

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