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X-ray powder diffraction (XRD) data were used to solve the crystal structures of phases in the magnesium perchlorate hydrate system, Mg(ClO4)2·nH2O (n = 4, 2). A heating stage and humidity generator interfaced to an environmental cell enabled in-situ XRD analyses of dehydration reactions under controlled temperatures and partial pressures of H2O (P_{{\rm H}_2{\rm O}}). The crystal structures were determined using an ab initio charge-flipping method and were refined using fundamental-parameter Rietveld methods. Dehydration of magnesium perchlorate hexahydrate to tetrahydrate (348 K) results in a decrease in symmetry (space group = C2), where isolated Mg2+ cations are equatorially coordinated by four H2O molecules with two [ClO4] tetrahedra at the apices. Further dehydration to the dihydrate (423 K) leads to bridging of the isolated packets to form double corner-sharing chains of octahedra and polyhedra (space group = C2/m).

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768110039686/kd5043sup1.cif
Contains datablocks global, profile1, profile2

txt

Text file https://doi.org/10.1107/S0108768110039686/kd5043sup2.txt
Supplementary material

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108768110039686/kd5043tetrahydrateprofilesup3.rtv
Contains datablock tetrahydrateprofile

Computing details top

(profile1) top
Crystal data top
Cl2H8MgO12V = 504.56 (4) Å3
Mr = 295.27Z = 2
Monoclinic, C2Cu Kα radiation, λ = 1.5418 Å
a = 11.4806 (4) ÅT = 348 K
b = 8.0025 (3) Åwhite
c = 5.9370 (3) Åflat sheet, 10 × 14 mm
β = 112.328 (3)°
Data collection top
Bruker D8
diffractometer
Scan method: step
Specimen mounting: Ni-Cr plated copper front loaded sample mount2θmin = 10°, 2θmax = 110°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 0.074Profile function: PVII
Rwp = 0.10452 parameters
Rexp = 0.006H-atom parameters not refined
RBragg = 0.058Background function: third-order Chebyshev polynomial
8383 data pointsPreferred orientation correction: sixth-order spherical harmonics
Excluded region(s): 89.5 to 90.5 2θ
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzBiso*/Beq
Cl0.7033310.109070.4
Mg110.50.8
O10.3333330.50.1666671.2
O20.1666670.660830.153011.2
O30.8333330.375930.763251.2
O40.50.238490.51.2
O510.270360.51.2
O60.651430.970790.853511.2
O70.893631.013130.727241.2
H10.547330.87350.564761
H20.937830.654290.438751
H30.57960.501180.097091
H40.300590.503820.719891
(profile2) top
Crystal data top
Cl2H4MgO10V = 387.89 (3) Å3
Mr = 259.24Z = 2
Monoclinic, C2/mCu Kα radiation, λ = 1.5418 Å
a = 14.3878 (6) ÅT = 423 K
b = 5.21861 (19) Åwhite
c = 5.4380 (3) Åflat sheet, 10 × 14 mm
β = 108.199 (2)°
Data collection top
Bruker D8
diffractometer
Scan method: step
Specimen mounting: Ni-Cr plated copper front loaded sample mount2θmin = 10°, 2θmax = 110°, 2θstep = 0.017°
Data collection mode: reflection
Refinement top
Rp = 0.053Profile function: PVII
Rwp = 0.07825 parameters
Rexp = 0.012H-atom parameters not refined
RBragg = 0.036Background function: third-order Chebyshev polynomial
8383 data pointsPreferred orientation correction: sixth-order spherical harmonics
Excluded region(s): 89.5 to 90.5 2θ
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzBiso*/Beq
Mg000.50.8
Cl0.6257810.830430.4
O10.381670.50.648371.2
O20.3204310.891.2
O30.057620.250.793171.2
O40.3126510.345251.2
H0.671870.626170.437661
 

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