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β-Ca2P2O7·4H2O is monoclinic, P21/c, a = 12.287 (6), b = 7.511 (3), c = 10.775 (5) Å, and β = 112.54 (1)°. Five of the terminal O atoms from a pyrophosphate group bind to Ca atoms, together with O atoms from three of the water molecules. The fourth H2O forms only hydrogen bonds. Both Ca atoms have coordination number 7 and show characteristics between those of a capped octahedron and a pentagonal bipyramid. The analysis of coordination distortions suggests that regularity and volume efficiency of a Ca coordination polyhedron increases with the number of bound water O atoms. The structure is layered after {100}, reflected also in the morphology of crystals which are formed as extremely thin plates. The central parts of the layers are formed by chains of Ca coordination polyhedra which run along the b axis and are interconnected by pyrophosphate groups. Water molecules form the surfaces of the layers. A peculiar auto-inhibition of growth from supersaturated solutions is supposed to be caused by a direct attachment of CaP2O72− and P2O74− to the water molecules on the surfaces of layers. Ca2P2O7·4H2O is known in two polymorphs. The unit-cell volume of the β form compared with that of α suggests that the former is a low-temperature modification.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108768100009447/os0054sup1.cif
Contains datablocks global, cppt

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108768100009447/os0054sup2.hkl
Contains datablock cppt

Computing details top

Program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).

(cppt) top
Crystal data top
Ca2O7P2·4(H2O)Z = 4
Mr = 326.16F(000) = 664
Monoclinic, P21/cDx = 2.359 Mg m3
Hall symbol: -P 2ybcMo Kα radiation, λ = 0.71073 Å
a = 12.287 (6) ÅCell parameters from 173 reflections
b = 7.511 (3) ŵ = 1.64 mm1
c = 10.775 (5) ÅT = 298 K
β = 112.542 (14)°{100},{001},{011}, colourless
V = 918.4 (7) Å30.24 × 0.06 × 0.01 mm
Data collection top
Radiation source: fine-focus sealed tube432 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.257
Absorption correction: gaussian face-indexed
?
θmax = 20.8°, θmin = 1.8°
Tmin = 0.891, Tmax = 0.987h = 1112
2928 measured reflectionsk = 57
959 independent reflectionsl = 109
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)] = 0.070Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.165H atoms treated by a mixture of independent and constrained refinement
S = 0.87 w = 1/[σ2(Fo2) + (0.0459P)2]
where P = (Fo2 + 2Fc2)/3
959 reflections(Δ/σ)max = 0.012
81 parametersΔρmax = 0.70 e Å3
0 restraintsΔρmin = 0.68 e Å3
Crystal data top
Ca2O7P2·4(H2O)V = 918.4 (7) Å3
Mr = 326.16Z = 4
Monoclinic, P21/cMo Kα radiation
a = 12.287 (6) ŵ = 1.64 mm1
b = 7.511 (3) ÅT = 298 K
c = 10.775 (5) Å0.24 × 0.06 × 0.01 mm
β = 112.542 (14)°
Data collection top
Absorption correction: gaussian face-indexed
?
432 reflections with I > 2σ(I)
Tmin = 0.891, Tmax = 0.987Rint = 0.257
2928 measured reflectionsθmax = 20.8°
959 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0700 restraints
wR(F2) = 0.165H atoms treated by a mixture of independent and constrained refinement
S = 0.87Δρmax = 0.70 e Å3
959 reflectionsΔρmin = 0.68 e Å3
81 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
Ca10.4691 (3)0.0022 (5)0.7271 (4)0.0174 (11)
Ca20.2613 (4)0.1473 (5)0.3157 (4)0.0202 (12)
P10.7424 (5)0.0268 (6)0.9849 (5)0.0179 (14)
P20.5607 (5)0.2385 (7)0.5199 (5)0.0207 (15)
O10.5129 (10)0.2410 (14)0.1263 (10)0.013 (3)*
O20.4707 (10)0.2434 (14)0.8748 (10)0.010 (3)*
O30.6795 (10)0.0141 (15)0.8352 (10)0.018 (3)*
O40.2187 (11)0.1544 (16)0.9504 (11)0.027 (4)*
O50.6512 (10)0.0938 (13)0.0491 (11)0.014 (3)*
O60.6311 (10)0.0693 (14)0.5232 (11)0.019 (3)*
O70.8390 (11)0.1595 (17)0.0257 (12)0.033 (4)*
OW10.2649 (11)0.0895 (14)0.6711 (12)0.026 (4)*
OW20.8827 (12)0.0078 (18)0.6201 (13)0.045 (4)*
OW30.0776 (11)0.1621 (17)0.1167 (11)0.035 (4)*
OW40.8928 (12)0.1621 (17)0.3290 (12)0.038 (4)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Ca10.026 (3)0.0016 (18)0.022 (2)0.000 (2)0.007 (2)0.001 (2)
Ca20.019 (3)0.012 (2)0.026 (3)0.000 (2)0.006 (2)0.002 (2)
P10.018 (4)0.012 (3)0.025 (3)0.007 (3)0.011 (3)0.002 (3)
P20.028 (4)0.006 (3)0.030 (4)0.002 (3)0.013 (3)0.004 (3)
Geometric parameters (Å, º) top
Ca1—O1i2.374 (11)P1—O5v1.608 (12)
Ca1—O1ii2.369 (12)P1—Ca2ii3.477 (6)
Ca1—O32.395 (12)P2—O1i1.483 (11)
Ca1—O22.406 (11)P2—O61.530 (12)
Ca1—OW12.436 (13)P2—O2iv1.536 (11)
Ca1—O2iii2.481 (11)P2—O5i1.629 (12)
Ca1—O6ii2.556 (11)P2—Ca1ii3.121 (6)
Ca1—P2ii3.121 (6)P2—Ca1iv3.506 (6)
Ca1—P23.365 (6)P2—Ca1vii3.500 (6)
Ca1—P13.445 (7)O1—P2iv1.483 (11)
Ca1—P2i3.506 (6)O1—Ca1iv2.374 (11)
Ca1—P2iii3.500 (6)O1—Ca1ii2.369 (12)
Ca2—O4iv2.276 (12)O2—P2i1.536 (11)
Ca2—O3ii2.355 (11)O2—Ca1vii2.481 (11)
Ca2—O6ii2.377 (11)O2—Ca2i2.539 (12)
Ca2—OW2ii2.430 (14)O3—Ca2ii2.355 (11)
Ca2—OW32.448 (12)O4—P1vi1.520 (12)
Ca2—OW1iv2.527 (12)O4—Ca2i2.276 (12)
Ca2—O2iv2.539 (12)O5—P1viii1.608 (12)
Ca2—P1ii3.477 (6)O5—P2iv1.629 (12)
Ca2—P23.555 (7)O6—Ca2ii2.377 (11)
Ca2—Ca1ii3.690 (6)O6—Ca1ii2.556 (11)
Ca2—Ca1iv4.029 (6)O7—P1viii1.482 (13)
P1—O7v1.482 (13)OW1—Ca2i2.527 (12)
P1—O31.501 (11)OW2—Ca2ii2.430 (14)
P1—O4vi1.520 (12)
O1i—Ca1—O1ii162.1 (2)P1ii—Ca2—P2106.86 (16)
O1i—Ca1—O378.5 (4)O4iv—Ca2—Ca1ii135.7 (4)
O1ii—Ca1—O384.1 (4)O3ii—Ca2—Ca1ii39.4 (3)
O1i—Ca1—O275.2 (4)O6ii—Ca2—Ca1ii66.9 (3)
O1ii—Ca1—O299.5 (4)OW2ii—Ca2—Ca1ii132.5 (4)
O3—Ca1—O285.2 (4)OW3—Ca2—Ca1ii118.3 (3)
O1i—Ca1—OW193.4 (4)OW1iv—Ca2—Ca1ii86.1 (3)
O1ii—Ca1—OW1101.4 (4)O2iv—Ca2—Ca1ii42.1 (3)
O3—Ca1—OW1158.1 (4)P1ii—Ca2—Ca1ii57.38 (12)
O2—Ca1—OW173.0 (4)P2—Ca2—Ca1ii50.99 (11)
O1i—Ca1—O2iii106.0 (4)O4iv—Ca2—Ca1iv92.6 (3)
O1ii—Ca1—O2iii73.9 (4)O3ii—Ca2—Ca1iv77.4 (3)
O3—Ca1—O2iii78.2 (4)O6ii—Ca2—Ca1iv113.2 (3)
O2—Ca1—O2iii162.65 (19)OW2ii—Ca2—Ca1iv167.8 (4)
OW1—Ca1—O2iii123.7 (4)OW3—Ca2—Ca1iv102.6 (3)
O1i—Ca1—O6ii77.9 (4)OW1iv—Ca2—Ca1iv35.0 (3)
O1ii—Ca1—O6ii115.2 (4)O2iv—Ca2—Ca1iv34.4 (2)
O3—Ca1—O6ii120.9 (4)P1ii—Ca2—Ca1iv78.94 (12)
O2—Ca1—O6ii137.3 (4)P2—Ca2—Ca1iv54.64 (12)
OW1—Ca1—O6ii76.2 (4)Ca1ii—Ca2—Ca1iv59.22 (7)
O2iii—Ca1—O6ii58.2 (3)O4iv—Ca2—Ca172.6 (3)
O1i—Ca1—P2ii93.1 (3)O3ii—Ca2—Ca1111.1 (3)
O1ii—Ca1—P2ii94.2 (3)O6ii—Ca2—Ca130.0 (3)
O3—Ca1—P2ii100.8 (3)OW2ii—Ca2—Ca178.2 (3)
O2—Ca1—P2ii165.6 (3)OW3—Ca2—Ca1153.3 (3)
OW1—Ca1—P2ii99.9 (3)OW1iv—Ca2—Ca1133.3 (3)
O2iii—Ca1—P2ii29.1 (3)O2iv—Ca2—Ca171.4 (2)
O6ii—Ca1—P2ii29.2 (3)P1ii—Ca2—Ca1130.70 (15)
O1i—Ca1—P222.5 (3)P2—Ca2—Ca149.41 (11)
O1ii—Ca1—P2151.6 (3)Ca1ii—Ca2—Ca181.13 (12)
O3—Ca1—P274.3 (3)Ca1iv—Ca2—Ca1103.22 (13)
O2—Ca1—P297.0 (3)O7v—P1—O3112.6 (7)
OW1—Ca1—P2105.6 (3)O7v—P1—O4vi113.0 (7)
O2iii—Ca1—P283.5 (3)O3—P1—O4vi112.2 (7)
O6ii—Ca1—P263.8 (3)O7v—P1—O5v105.8 (7)
P2ii—Ca1—P272.50 (17)O3—P1—O5v109.0 (7)
O1i—Ca1—P190.2 (3)O4vi—P1—O5v103.4 (6)
O1ii—Ca1—P172.0 (3)O7v—P1—Ca1134.2 (5)
O3—Ca1—P121.5 (3)O3—P1—Ca135.8 (5)
O2—Ca1—P170.6 (3)O4vi—P1—Ca1111.1 (5)
OW1—Ca1—P1141.1 (3)O5v—P1—Ca174.9 (4)
O2iii—Ca1—P192.0 (3)O7v—P1—Ca2ii104.6 (5)
O6ii—Ca1—P1142.0 (3)O3—P1—Ca2ii32.6 (5)
P2ii—Ca1—P1118.55 (18)O4vi—P1—Ca2ii88.9 (5)
P2—Ca1—P192.08 (16)O5v—P1—Ca2ii139.2 (5)
O1i—Ca1—P2i84.8 (3)Ca1—P1—Ca2ii64.43 (13)
O1ii—Ca1—P2i85.0 (3)O1i—P2—O6117.1 (7)
O3—Ca1—P2i68.1 (3)O1i—P2—O2iv115.7 (7)
O2—Ca1—P2i21.3 (3)O6—P2—O2iv106.1 (7)
OW1—Ca1—P2i91.0 (3)O1i—P2—O5i102.3 (6)
O2iii—Ca1—P2i141.9 (3)O6—P2—O5i107.4 (6)
O6ii—Ca1—P2i157.7 (3)O2iv—P2—O5i107.4 (6)
P2ii—Ca1—P2i168.99 (14)O1i—P2—Ca1ii140.2 (5)
P2—Ca1—P2i103.33 (12)O6—P2—Ca1ii54.5 (5)
P1—Ca1—P2i50.78 (13)O2iv—P2—Ca1ii51.7 (4)
O1i—Ca1—P2iii157.8 (3)O5i—P2—Ca1ii117.4 (5)
O1ii—Ca1—P2iii19.2 (3)O1i—P2—Ca137.8 (4)
O3—Ca1—P2iii93.3 (3)O6—P2—Ca182.9 (5)
O2—Ca1—P2iii83.6 (3)O2iv—P2—Ca1115.4 (5)
OW1—Ca1—P2iii86.6 (3)O5i—P2—Ca1131.0 (5)
O2iii—Ca1—P2iii92.2 (3)Ca1ii—P2—Ca1107.50 (17)
O6ii—Ca1—P2iii123.4 (3)O1i—P2—Ca1iv123.5 (5)
P2ii—Ca1—P2iii108.87 (11)O6—P2—Ca1iv117.8 (5)
P2—Ca1—P2iii167.53 (13)O2iv—P2—Ca1iv34.6 (4)
P1—Ca1—P2iii76.30 (15)O5i—P2—Ca1iv72.8 (4)
P2i—Ca1—P2iii72.95 (16)Ca1ii—P2—Ca1iv70.24 (11)
O4iv—Ca2—O3ii169.8 (5)Ca1—P2—Ca1iv144.7 (2)
O4iv—Ca2—O6ii100.5 (4)O1i—P2—Ca1vii31.6 (4)
O3ii—Ca2—O6ii85.4 (4)O6—P2—Ca1vii132.8 (5)
O4iv—Ca2—OW2ii76.2 (4)O2iv—P2—Ca1vii119.5 (5)
O3ii—Ca2—OW2ii113.6 (4)O5i—P2—Ca1vii71.3 (5)
O6ii—Ca2—OW2ii74.1 (4)Ca1ii—P2—Ca1vii168.2 (2)
O4iv—Ca2—OW399.7 (4)Ca1—P2—Ca1vii67.69 (10)
O3ii—Ca2—OW381.0 (4)Ca1iv—P2—Ca1vii107.05 (16)
O6ii—Ca2—OW3137.6 (5)O1i—P2—Ca282.9 (5)
OW2ii—Ca2—OW375.2 (4)O6—P2—Ca2107.2 (5)
O4iv—Ca2—OW1iv86.8 (4)O2iv—P2—Ca238.5 (4)
O3ii—Ca2—OW1iv83.9 (4)O5i—P2—Ca2137.4 (5)
O6ii—Ca2—OW1iv148.1 (4)Ca1ii—P2—Ca266.75 (14)
OW2ii—Ca2—OW1iv137.5 (5)Ca1—P2—Ca277.26 (14)
OW3—Ca2—OW1iv69.7 (4)Ca1iv—P2—Ca269.58 (14)
O4iv—Ca2—O2iv95.0 (4)Ca1vii—P2—Ca2101.46 (16)
O3ii—Ca2—O2iv77.8 (4)P2iv—O1—Ca1iv119.7 (6)
O6ii—Ca2—O2iv79.1 (4)P2iv—O1—Ca1ii129.2 (6)
OW2ii—Ca2—O2iv149.6 (4)Ca1iv—O1—Ca1ii107.5 (4)
OW3—Ca2—O2iv135.3 (4)P2i—O2—Ca1124.1 (6)
OW1iv—Ca2—O2iv69.3 (4)P2i—O2—Ca1vii99.3 (6)
O4iv—Ca2—P1ii156.4 (3)Ca1—O2—Ca1vii103.0 (4)
O3ii—Ca2—P1ii20.1 (3)P2i—O2—Ca2i119.4 (6)
O6ii—Ca2—P1ii103.2 (3)Ca1—O2—Ca2i109.1 (4)
OW2ii—Ca2—P1ii109.5 (3)Ca1vii—O2—Ca2i94.6 (4)
OW3—Ca2—P1ii61.5 (3)P1—O3—Ca2ii127.3 (7)
OW1iv—Ca2—P1ii73.6 (3)P1—O3—Ca1122.7 (7)
O2iv—Ca2—P1ii90.3 (3)Ca2ii—O3—Ca1101.9 (4)
O4iv—Ca2—P285.1 (3)P1vi—O4—Ca2i140.3 (7)
O3ii—Ca2—P290.4 (3)P1viii—O5—P2iv134.1 (7)
O6ii—Ca2—P261.7 (3)P2—O6—Ca2ii137.5 (7)
OW2ii—Ca2—P2127.6 (3)P2—O6—Ca1ii96.4 (6)
OW3—Ca2—P2157.1 (3)Ca2ii—O6—Ca1ii122.3 (4)
OW1iv—Ca2—P288.4 (3)Ca1—OW1—Ca2i108.5 (5)
O2iv—Ca2—P222.1 (2)
Symmetry codes: (i) x, y+1/2, z+1/2; (ii) x+1, y, z+1; (iii) x+1, y1/2, z+3/2; (iv) x, y+1/2, z1/2; (v) x, y, z+1; (vi) x+1, y, z+2; (vii) x+1, y+1/2, z+3/2; (viii) x, y, z1.

Experimental details

Crystal data
Chemical formulaCa2O7P2·4(H2O)
Mr326.16
Crystal system, space groupMonoclinic, P21/c
Temperature (K)298
a, b, c (Å)12.287 (6), 7.511 (3), 10.775 (5)
β (°) 112.542 (14)
V3)918.4 (7)
Z4
Radiation typeMo Kα
µ (mm1)1.64
Crystal size (mm)0.24 × 0.06 × 0.01
Data collection
Diffractometer?
Absorption correctionGaussian face-indexed
Tmin, Tmax0.891, 0.987
No. of measured, independent and
observed [I > 2σ(I)] reflections
2928, 959, 432
Rint0.257
θmax (°)20.8
(sin θ/λ)max1)0.500
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.070, 0.165, 0.87
No. of reflections959
No. of parameters81
H-atom treatmentH atoms treated by a mixture of independent and constrained refinement
Δρmax, Δρmin (e Å3)0.70, 0.68

Computer programs: SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997).

 

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