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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
Program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997).
Crystal data top
Ca2O7P2·4(H2O) | Z = 4 |
Mr = 326.16 | F(000) = 664 |
Monoclinic, P21/c | Dx = 2.359 Mg m−3 |
Hall symbol: -P 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 12.287 (6) Å | Cell parameters from 173 reflections |
b = 7.511 (3) Å | µ = 1.64 mm−1 |
c = 10.775 (5) Å | T = 298 K |
β = 112.542 (14)° | {100},{001},{011}, colourless |
V = 918.4 (7) Å3 | 0.24 × 0.06 × 0.01 mm |
Data collection top
Radiation source: fine-focus sealed tube | 432 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.257 |
Absorption correction: gaussian face-indexed ? | θmax = 20.8°, θmin = 1.8° |
Tmin = 0.891, Tmax = 0.987 | h = −11→12 |
2928 measured reflections | k = −5→7 |
959 independent reflections | l = −10→9 |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.070 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.165 | H 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 parameters | Δρmax = 0.70 e Å−3 |
0 restraints | Δρmin = −0.68 e Å−3 |
Crystal data top
Ca2O7P2·4(H2O) | V = 918.4 (7) Å3 |
Mr = 326.16 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 12.287 (6) Å | µ = 1.64 mm−1 |
b = 7.511 (3) Å | T = 298 K |
c = 10.775 (5) Å | 0.24 × 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 = 0.987 | Rint = 0.257 |
2928 measured reflections | θmax = 20.8° |
959 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.070 | 0 restraints |
wR(F2) = 0.165 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.87 | Δρmax = 0.70 e Å−3 |
959 reflections | Δρmin = −0.68 e Å−3 |
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 | x | y | z | Uiso*/Ueq | |
Ca1 | 0.4691 (3) | 0.0022 (5) | 0.7271 (4) | 0.0174 (11) | |
Ca2 | 0.2613 (4) | 0.1473 (5) | 0.3157 (4) | 0.0202 (12) | |
P1 | 0.7424 (5) | 0.0268 (6) | 0.9849 (5) | 0.0179 (14) | |
P2 | 0.5607 (5) | 0.2385 (7) | 0.5199 (5) | 0.0207 (15) | |
O1 | 0.5129 (10) | 0.2410 (14) | 0.1263 (10) | 0.013 (3)* | |
O2 | 0.4707 (10) | 0.2434 (14) | 0.8748 (10) | 0.010 (3)* | |
O3 | 0.6795 (10) | 0.0141 (15) | 0.8352 (10) | 0.018 (3)* | |
O4 | 0.2187 (11) | 0.1544 (16) | 0.9504 (11) | 0.027 (4)* | |
O5 | 0.6512 (10) | 0.0938 (13) | 0.0491 (11) | 0.014 (3)* | |
O6 | 0.6311 (10) | 0.0693 (14) | 0.5232 (11) | 0.019 (3)* | |
O7 | 0.8390 (11) | 0.1595 (17) | 0.0257 (12) | 0.033 (4)* | |
OW1 | 0.2649 (11) | 0.0895 (14) | 0.6711 (12) | 0.026 (4)* | |
OW2 | 0.8827 (12) | 0.0078 (18) | 0.6201 (13) | 0.045 (4)* | |
OW3 | 0.0776 (11) | 0.1621 (17) | 0.1167 (11) | 0.035 (4)* | |
OW4 | 0.8928 (12) | 0.1621 (17) | 0.3290 (12) | 0.038 (4)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Ca1 | 0.026 (3) | 0.0016 (18) | 0.022 (2) | 0.000 (2) | 0.007 (2) | 0.001 (2) |
Ca2 | 0.019 (3) | 0.012 (2) | 0.026 (3) | 0.000 (2) | 0.006 (2) | 0.002 (2) |
P1 | 0.018 (4) | 0.012 (3) | 0.025 (3) | −0.007 (3) | 0.011 (3) | −0.002 (3) |
P2 | 0.028 (4) | 0.006 (3) | 0.030 (4) | −0.002 (3) | 0.013 (3) | −0.004 (3) |
Geometric parameters (Å, º) top
Ca1—O1i | 2.374 (11) | P1—O5v | 1.608 (12) |
Ca1—O1ii | 2.369 (12) | P1—Ca2ii | 3.477 (6) |
Ca1—O3 | 2.395 (12) | P2—O1i | 1.483 (11) |
Ca1—O2 | 2.406 (11) | P2—O6 | 1.530 (12) |
Ca1—OW1 | 2.436 (13) | P2—O2iv | 1.536 (11) |
Ca1—O2iii | 2.481 (11) | P2—O5i | 1.629 (12) |
Ca1—O6ii | 2.556 (11) | P2—Ca1ii | 3.121 (6) |
Ca1—P2ii | 3.121 (6) | P2—Ca1iv | 3.506 (6) |
Ca1—P2 | 3.365 (6) | P2—Ca1vii | 3.500 (6) |
Ca1—P1 | 3.445 (7) | O1—P2iv | 1.483 (11) |
Ca1—P2i | 3.506 (6) | O1—Ca1iv | 2.374 (11) |
Ca1—P2iii | 3.500 (6) | O1—Ca1ii | 2.369 (12) |
Ca2—O4iv | 2.276 (12) | O2—P2i | 1.536 (11) |
Ca2—O3ii | 2.355 (11) | O2—Ca1vii | 2.481 (11) |
Ca2—O6ii | 2.377 (11) | O2—Ca2i | 2.539 (12) |
Ca2—OW2ii | 2.430 (14) | O3—Ca2ii | 2.355 (11) |
Ca2—OW3 | 2.448 (12) | O4—P1vi | 1.520 (12) |
Ca2—OW1iv | 2.527 (12) | O4—Ca2i | 2.276 (12) |
Ca2—O2iv | 2.539 (12) | O5—P1viii | 1.608 (12) |
Ca2—P1ii | 3.477 (6) | O5—P2iv | 1.629 (12) |
Ca2—P2 | 3.555 (7) | O6—Ca2ii | 2.377 (11) |
Ca2—Ca1ii | 3.690 (6) | O6—Ca1ii | 2.556 (11) |
Ca2—Ca1iv | 4.029 (6) | O7—P1viii | 1.482 (13) |
P1—O7v | 1.482 (13) | OW1—Ca2i | 2.527 (12) |
P1—O3 | 1.501 (11) | OW2—Ca2ii | 2.430 (14) |
P1—O4vi | 1.520 (12) | | |
| | | |
O1i—Ca1—O1ii | 162.1 (2) | P1ii—Ca2—P2 | 106.86 (16) |
O1i—Ca1—O3 | 78.5 (4) | O4iv—Ca2—Ca1ii | 135.7 (4) |
O1ii—Ca1—O3 | 84.1 (4) | O3ii—Ca2—Ca1ii | 39.4 (3) |
O1i—Ca1—O2 | 75.2 (4) | O6ii—Ca2—Ca1ii | 66.9 (3) |
O1ii—Ca1—O2 | 99.5 (4) | OW2ii—Ca2—Ca1ii | 132.5 (4) |
O3—Ca1—O2 | 85.2 (4) | OW3—Ca2—Ca1ii | 118.3 (3) |
O1i—Ca1—OW1 | 93.4 (4) | OW1iv—Ca2—Ca1ii | 86.1 (3) |
O1ii—Ca1—OW1 | 101.4 (4) | O2iv—Ca2—Ca1ii | 42.1 (3) |
O3—Ca1—OW1 | 158.1 (4) | P1ii—Ca2—Ca1ii | 57.38 (12) |
O2—Ca1—OW1 | 73.0 (4) | P2—Ca2—Ca1ii | 50.99 (11) |
O1i—Ca1—O2iii | 106.0 (4) | O4iv—Ca2—Ca1iv | 92.6 (3) |
O1ii—Ca1—O2iii | 73.9 (4) | O3ii—Ca2—Ca1iv | 77.4 (3) |
O3—Ca1—O2iii | 78.2 (4) | O6ii—Ca2—Ca1iv | 113.2 (3) |
O2—Ca1—O2iii | 162.65 (19) | OW2ii—Ca2—Ca1iv | 167.8 (4) |
OW1—Ca1—O2iii | 123.7 (4) | OW3—Ca2—Ca1iv | 102.6 (3) |
O1i—Ca1—O6ii | 77.9 (4) | OW1iv—Ca2—Ca1iv | 35.0 (3) |
O1ii—Ca1—O6ii | 115.2 (4) | O2iv—Ca2—Ca1iv | 34.4 (2) |
O3—Ca1—O6ii | 120.9 (4) | P1ii—Ca2—Ca1iv | 78.94 (12) |
O2—Ca1—O6ii | 137.3 (4) | P2—Ca2—Ca1iv | 54.64 (12) |
OW1—Ca1—O6ii | 76.2 (4) | Ca1ii—Ca2—Ca1iv | 59.22 (7) |
O2iii—Ca1—O6ii | 58.2 (3) | O4iv—Ca2—Ca1 | 72.6 (3) |
O1i—Ca1—P2ii | 93.1 (3) | O3ii—Ca2—Ca1 | 111.1 (3) |
O1ii—Ca1—P2ii | 94.2 (3) | O6ii—Ca2—Ca1 | 30.0 (3) |
O3—Ca1—P2ii | 100.8 (3) | OW2ii—Ca2—Ca1 | 78.2 (3) |
O2—Ca1—P2ii | 165.6 (3) | OW3—Ca2—Ca1 | 153.3 (3) |
OW1—Ca1—P2ii | 99.9 (3) | OW1iv—Ca2—Ca1 | 133.3 (3) |
O2iii—Ca1—P2ii | 29.1 (3) | O2iv—Ca2—Ca1 | 71.4 (2) |
O6ii—Ca1—P2ii | 29.2 (3) | P1ii—Ca2—Ca1 | 130.70 (15) |
O1i—Ca1—P2 | 22.5 (3) | P2—Ca2—Ca1 | 49.41 (11) |
O1ii—Ca1—P2 | 151.6 (3) | Ca1ii—Ca2—Ca1 | 81.13 (12) |
O3—Ca1—P2 | 74.3 (3) | Ca1iv—Ca2—Ca1 | 103.22 (13) |
O2—Ca1—P2 | 97.0 (3) | O7v—P1—O3 | 112.6 (7) |
OW1—Ca1—P2 | 105.6 (3) | O7v—P1—O4vi | 113.0 (7) |
O2iii—Ca1—P2 | 83.5 (3) | O3—P1—O4vi | 112.2 (7) |
O6ii—Ca1—P2 | 63.8 (3) | O7v—P1—O5v | 105.8 (7) |
P2ii—Ca1—P2 | 72.50 (17) | O3—P1—O5v | 109.0 (7) |
O1i—Ca1—P1 | 90.2 (3) | O4vi—P1—O5v | 103.4 (6) |
O1ii—Ca1—P1 | 72.0 (3) | O7v—P1—Ca1 | 134.2 (5) |
O3—Ca1—P1 | 21.5 (3) | O3—P1—Ca1 | 35.8 (5) |
O2—Ca1—P1 | 70.6 (3) | O4vi—P1—Ca1 | 111.1 (5) |
OW1—Ca1—P1 | 141.1 (3) | O5v—P1—Ca1 | 74.9 (4) |
O2iii—Ca1—P1 | 92.0 (3) | O7v—P1—Ca2ii | 104.6 (5) |
O6ii—Ca1—P1 | 142.0 (3) | O3—P1—Ca2ii | 32.6 (5) |
P2ii—Ca1—P1 | 118.55 (18) | O4vi—P1—Ca2ii | 88.9 (5) |
P2—Ca1—P1 | 92.08 (16) | O5v—P1—Ca2ii | 139.2 (5) |
O1i—Ca1—P2i | 84.8 (3) | Ca1—P1—Ca2ii | 64.43 (13) |
O1ii—Ca1—P2i | 85.0 (3) | O1i—P2—O6 | 117.1 (7) |
O3—Ca1—P2i | 68.1 (3) | O1i—P2—O2iv | 115.7 (7) |
O2—Ca1—P2i | 21.3 (3) | O6—P2—O2iv | 106.1 (7) |
OW1—Ca1—P2i | 91.0 (3) | O1i—P2—O5i | 102.3 (6) |
O2iii—Ca1—P2i | 141.9 (3) | O6—P2—O5i | 107.4 (6) |
O6ii—Ca1—P2i | 157.7 (3) | O2iv—P2—O5i | 107.4 (6) |
P2ii—Ca1—P2i | 168.99 (14) | O1i—P2—Ca1ii | 140.2 (5) |
P2—Ca1—P2i | 103.33 (12) | O6—P2—Ca1ii | 54.5 (5) |
P1—Ca1—P2i | 50.78 (13) | O2iv—P2—Ca1ii | 51.7 (4) |
O1i—Ca1—P2iii | 157.8 (3) | O5i—P2—Ca1ii | 117.4 (5) |
O1ii—Ca1—P2iii | 19.2 (3) | O1i—P2—Ca1 | 37.8 (4) |
O3—Ca1—P2iii | 93.3 (3) | O6—P2—Ca1 | 82.9 (5) |
O2—Ca1—P2iii | 83.6 (3) | O2iv—P2—Ca1 | 115.4 (5) |
OW1—Ca1—P2iii | 86.6 (3) | O5i—P2—Ca1 | 131.0 (5) |
O2iii—Ca1—P2iii | 92.2 (3) | Ca1ii—P2—Ca1 | 107.50 (17) |
O6ii—Ca1—P2iii | 123.4 (3) | O1i—P2—Ca1iv | 123.5 (5) |
P2ii—Ca1—P2iii | 108.87 (11) | O6—P2—Ca1iv | 117.8 (5) |
P2—Ca1—P2iii | 167.53 (13) | O2iv—P2—Ca1iv | 34.6 (4) |
P1—Ca1—P2iii | 76.30 (15) | O5i—P2—Ca1iv | 72.8 (4) |
P2i—Ca1—P2iii | 72.95 (16) | Ca1ii—P2—Ca1iv | 70.24 (11) |
O4iv—Ca2—O3ii | 169.8 (5) | Ca1—P2—Ca1iv | 144.7 (2) |
O4iv—Ca2—O6ii | 100.5 (4) | O1i—P2—Ca1vii | 31.6 (4) |
O3ii—Ca2—O6ii | 85.4 (4) | O6—P2—Ca1vii | 132.8 (5) |
O4iv—Ca2—OW2ii | 76.2 (4) | O2iv—P2—Ca1vii | 119.5 (5) |
O3ii—Ca2—OW2ii | 113.6 (4) | O5i—P2—Ca1vii | 71.3 (5) |
O6ii—Ca2—OW2ii | 74.1 (4) | Ca1ii—P2—Ca1vii | 168.2 (2) |
O4iv—Ca2—OW3 | 99.7 (4) | Ca1—P2—Ca1vii | 67.69 (10) |
O3ii—Ca2—OW3 | 81.0 (4) | Ca1iv—P2—Ca1vii | 107.05 (16) |
O6ii—Ca2—OW3 | 137.6 (5) | O1i—P2—Ca2 | 82.9 (5) |
OW2ii—Ca2—OW3 | 75.2 (4) | O6—P2—Ca2 | 107.2 (5) |
O4iv—Ca2—OW1iv | 86.8 (4) | O2iv—P2—Ca2 | 38.5 (4) |
O3ii—Ca2—OW1iv | 83.9 (4) | O5i—P2—Ca2 | 137.4 (5) |
O6ii—Ca2—OW1iv | 148.1 (4) | Ca1ii—P2—Ca2 | 66.75 (14) |
OW2ii—Ca2—OW1iv | 137.5 (5) | Ca1—P2—Ca2 | 77.26 (14) |
OW3—Ca2—OW1iv | 69.7 (4) | Ca1iv—P2—Ca2 | 69.58 (14) |
O4iv—Ca2—O2iv | 95.0 (4) | Ca1vii—P2—Ca2 | 101.46 (16) |
O3ii—Ca2—O2iv | 77.8 (4) | P2iv—O1—Ca1iv | 119.7 (6) |
O6ii—Ca2—O2iv | 79.1 (4) | P2iv—O1—Ca1ii | 129.2 (6) |
OW2ii—Ca2—O2iv | 149.6 (4) | Ca1iv—O1—Ca1ii | 107.5 (4) |
OW3—Ca2—O2iv | 135.3 (4) | P2i—O2—Ca1 | 124.1 (6) |
OW1iv—Ca2—O2iv | 69.3 (4) | P2i—O2—Ca1vii | 99.3 (6) |
O4iv—Ca2—P1ii | 156.4 (3) | Ca1—O2—Ca1vii | 103.0 (4) |
O3ii—Ca2—P1ii | 20.1 (3) | P2i—O2—Ca2i | 119.4 (6) |
O6ii—Ca2—P1ii | 103.2 (3) | Ca1—O2—Ca2i | 109.1 (4) |
OW2ii—Ca2—P1ii | 109.5 (3) | Ca1vii—O2—Ca2i | 94.6 (4) |
OW3—Ca2—P1ii | 61.5 (3) | P1—O3—Ca2ii | 127.3 (7) |
OW1iv—Ca2—P1ii | 73.6 (3) | P1—O3—Ca1 | 122.7 (7) |
O2iv—Ca2—P1ii | 90.3 (3) | Ca2ii—O3—Ca1 | 101.9 (4) |
O4iv—Ca2—P2 | 85.1 (3) | P1vi—O4—Ca2i | 140.3 (7) |
O3ii—Ca2—P2 | 90.4 (3) | P1viii—O5—P2iv | 134.1 (7) |
O6ii—Ca2—P2 | 61.7 (3) | P2—O6—Ca2ii | 137.5 (7) |
OW2ii—Ca2—P2 | 127.6 (3) | P2—O6—Ca1ii | 96.4 (6) |
OW3—Ca2—P2 | 157.1 (3) | Ca2ii—O6—Ca1ii | 122.3 (4) |
OW1iv—Ca2—P2 | 88.4 (3) | Ca1—OW1—Ca2i | 108.5 (5) |
O2iv—Ca2—P2 | 22.1 (2) | | |
Symmetry codes: (i) x, −y+1/2, z+1/2; (ii) −x+1, −y, −z+1; (iii) −x+1, y−1/2, −z+3/2; (iv) x, −y+1/2, z−1/2; (v) x, y, z+1; (vi) −x+1, −y, −z+2; (vii) −x+1, y+1/2, −z+3/2; (viii) x, y, z−1. |
Experimental details
Crystal data |
Chemical formula | Ca2O7P2·4(H2O) |
Mr | 326.16 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 298 |
a, b, c (Å) | 12.287 (6), 7.511 (3), 10.775 (5) |
β (°) | 112.542 (14) |
V (Å3) | 918.4 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 1.64 |
Crystal size (mm) | 0.24 × 0.06 × 0.01 |
|
Data collection |
Diffractometer | ? |
Absorption correction | Gaussian face-indexed |
Tmin, Tmax | 0.891, 0.987 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2928, 959, 432 |
Rint | 0.257 |
θmax (°) | 20.8 |
(sin θ/λ)max (Å−1) | 0.500 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.070, 0.165, 0.87 |
No. of reflections | 959 |
No. of parameters | 81 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.70, −0.68 |
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