The compound diiron diphosphate dihydrate, Fe2P2O7(H2O)2, was synthesized hydrothermally and crystallizes in the monoclinic space group P21/n. The compound has a somewhat open framework made up of edge-sharing iron(II) octahedra that form chains connected by five bridging diphosphates. The remaining octahedral site of each iron is occupied by coordinated water. The H atoms of the water molecules all point into a common channel.
Supporting information
Colorless single crystals of Fe2PO7(H2O)2 were obtained from a reaction
mixture of iron metal (42 mg, 752 mmol), TiO (48 mg, 752 mmol) and 25%
H3PO4(aq) (0.7 ml) which was placed into a quartz tube. The tube was then
put into an autoclave with a counter pressure of 18.62 MPa of argon gas. The
reaction was heated for 3 d at 648 K and cooled in air to room temperature.
Upon visual inspection of the quartz tube, the only crystalline material
present were colorless truncated diamond-shaped crystals of the title compound
and black polyhedral shaped crystals precipitated from a clear solution. The
yield for the colorless crystals was approximately 5–7%. The black polyhedral
crystals are currently being characterized.
All atoms except the H atoms were refined with anisotropic displacement
parameters.
Data collection: P3 Software (Siemens, 1989); cell refinement: P3 Software; data reduction: SHELXTL-Plus (Sheldrick, 1990); program(s) used to solve structure: SHELXTL-Plus); program(s) used to refine structure: SHELXTL-Plus; software used to prepare material for publication: SHELXTL-Plus.
Iron(II) Diphosphate Dihydrate
top
Crystal data top
Fe2P2O7(H2O)2 | F(000) = 632.00 |
Mr = 321.7 | Dx = 3.188 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
a = 6.400 (2) Å | Cell parameters from 50 reflections |
b = 14.181 (3) Å | θ = 25.1–27.5° |
c = 7.416 (1) Å | µ = 4.83 mm−1 |
β = 95.43 (2)° | T = 297 K |
V = 670.1 (2) Å3 | Truncated diamonds, colorless |
Z = 4 | 0.48 × 0.24 × 0.17 mm |
Data collection top
Nicolet R 3m/V diffractometer | 1454 reflections with (F) > 4σ(F) |
Radiation source: Sealed tube | Rint = 0.016 |
Graphite monochromator | θmax = 27.5°, θmin = 1.8° |
ω/2–θ scans | h = 0→8 |
Absorption correction: ψ scan (North et al., 1968) | k = 0→18 |
Tmin = 0.185, Tmax = 0.416 | l = −9→9 |
1754 measured reflections | 3 standard reflections every 97 reflections |
1547 independent reflections | intensity decay: 1.0% |
Refinement top
Refinement on F | Primary atom site location: Direct Methods |
Least-squares matrix: full | Hydrogen site location: Difference Fourier |
R[F2 > 2σ(F2)] = 0.019 | Isotropic |
wR(F2) = 0.030 | 1/(σ2(F) + 0.0005F2) |
S = 1.18 | (Δ/σ)max = 0.042 |
1454 reflections | Δρmax = 0.55 e Å−3 |
135 parameters | Δρmin = −0.58 e Å−3 |
0 restraints | Extinction correction: (Larson, 1970) |
0 constraints | Extinction coefficient: 0.0000004861 (3) |
Crystal data top
Fe2P2O7(H2O)2 | V = 670.1 (2) Å3 |
Mr = 321.7 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 6.400 (2) Å | µ = 4.83 mm−1 |
b = 14.181 (3) Å | T = 297 K |
c = 7.416 (1) Å | 0.48 × 0.24 × 0.17 mm |
β = 95.43 (2)° | |
Data collection top
Nicolet R 3m/V diffractometer | 1454 reflections with (F) > 4σ(F) |
Absorption correction: ψ scan (North et al., 1968) | Rint = 0.016 |
Tmin = 0.185, Tmax = 0.416 | 3 standard reflections every 97 reflections |
1754 measured reflections | intensity decay: 1.0% |
1547 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.019 | 0 restraints |
wR(F2) = 0.030 | Isotropic |
S = 1.18 | Δρmax = 0.55 e Å−3 |
1454 reflections | Δρmin = −0.58 e Å−3 |
135 parameters | |
Special details top
Refinement. The structure was solved using direct methods and refined by full matrix, least
squares techniques. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
Fe(1) | 0.7374 (1) | 0.6099 (1) | −0.0801 (1) | 0.008 (1) | |
Fe(2) | 0.0490 (1) | 0.2474 (1) | 0.3470 (1) | 0.008 (1) | |
P(1) | 0.7572 (1) | 0.4148 (1) | 0.1499 (1) | 0.006 (1) | |
P(2) | 0.5658 (1) | 0.3124 (1) | 0.4248 (1) | 0.006 (1) | |
O(1) | 0.7956 (2) | 0.5187 (1) | 0.1281 (2) | 0.011 (1) | |
O(2) | 0.9588 (2) | 0.3580 (1) | 0.1585 (2) | 0.010 (1) | |
O(3) | 0.5863 (2) | 0.3726 (1) | 0.0171 (2) | 0.010 (1) | |
O(4) | 0.6691 (2) | 0.4053 (1) | 0.3460 (2) | 0.008 (1) | |
O(5) | 0.7231 (2) | 0.2325 (1) | 0.4057 (2) | 0.010 (1) | |
O(6) | 0.3627 (2) | 0.2950 (1) | 0.3057 (2) | 0.010 (1) | |
O(7) | 0.5343 (2) | 0.3382 (1) | 0.6181 (2) | 0.011 (1) | |
O(8) | 0.7500 (3) | 0.5021 (1) | −0.2811 (2) | 0.018 (1) | |
O(9) | 0.0693 (2) | 0.3502 (1) | 0.5611 (2) | 017 (1) | |
H(1) | 0.662 (6) | 0.458 (3) | −0.303 (5) | 0.062 (12) | |
H(2) | 0.878 (9) | 0.475 (4) | −0.290 (7) | 0.12 (2) | |
H(3) | 0.163 (8) | 0.389 (3) | 0.536 (6) | 0.088 (17) | |
H(4) | 0.085 (7) | 0.330 (3) | 0.684 (6) | 0.083 (15) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Fe(1) | 0.008 (1) | 0.006 (1) | 0.008 (1) | 0.000 (1) | 0.001 (1) | 0.001 (1) |
Fe(2) | 0.009 (1) | 0.007 (1) | 0.008 (1) | 0.000 (1) | 0.001 (1) | 0.001 (1) |
P(1) | 0.007 (1) | 0.005 (1) | 0.007 (1) | 0.000 (1) | 0.001 (1) | 0.001 (1) |
P(2) | 0.007 (1) | 0.006 (1) | 0.006 (1) | 0.000 (1) | 0.001 (1) | 0.000 (1) |
O(1) | 0.014 (1) | 0.006 (1) | 0.012 (1) | −0.002 (1) | 0.000 (1) | 0.002 (1) |
O(2) | 0.008 (1) | 0.008 (1) | 0.014 (1) | 0.002 (1) | 0.002 (1) | 0.003 (1) |
O(3) | 0.009 (1) | 0.010 (1) | 0.010 (1) | −0.001 (1) | 0.001 (1) | −0.002 (1) |
O(4) | 0.010 (1) | 0.006 (1) | 0.007 (1) | −0.002 (1) | 0.002 (1) | 0.000 (1) |
O(5) | 0.009 (1) | 0.007 (1) | 0.013 (1) | 0.002 (1) | 0.003 (1) | 0.002 (1) |
O(6) | 0.009 (1) | 0.011 (1) | 0.009 (1) | −0.002 (1) | 0.000 (1) | 0.002 (1) |
O(7) | 0.015 (1) | 0.010 (1) | 0.007 (1) | −0.001 (1) | 0.002 (1) | 0.000 (1) |
O(8) | 0.020 (1) | 0.012 (1) | 0.022 (1) | −0.003 (1) | 0.002 (1) | −0.007 (1) |
O(9) | 0.017 (1) | 0.022 (1) | 0.014 (1) | −0.001 (1) | 0.001 (1) | −0.003 (1) |
Geometric parameters (Å, º) top
Fe(1)—O(1) | 2.022 (2) | P(1)—O(1) | 1.505 (2) |
Fe(1)—O(8) | 2.142 (2) | P(1)—O(2) | 1.517 (1) |
Fe(1)—O(2)i | 2.130 (2) | P(1)—O(3) | 1.524 (1) |
Fe(1)—O(3)ii | 2.181 (2) | P(1)—O(4) | 1.614 (1) |
Fe(1)—O(5)iii | 2.166 (2) | P(2)—O(4) | 1.608 (1) |
Fe(1)—O(6)ii | 2.197 (1) | P(2)—O(5) | 1.532 (2) |
Fe(2)—O(6) | 2.167 (2) | P(2)—O(6) | 1.521 (1) |
Fe(2)—O(9) | 2.151 (2) | P(2)—O(7) | 1.511 (1) |
Fe(2)—O(2)iv | 2.144 (2) | O(8)—H(1) | 0.85 (4) |
Fe(2)—O(3)v | 2.118 (2) | O(8)—H(2) | 0.92 (6) |
Fe(2)—O(5)iv | 2.181 (2) | O(9)—H(3) | 0.85 (5) |
Fe(2)—O(7)vi | 2.081 (2) | O(9)—H(4) | 0.95 (4) |
| | | |
O(1)—Fe(1)—O(8) | 93.3 (1) | O(2)—P(1)—O(3) | 112.0 (1) |
O(1)—Fe(1)—O(2)i | 103.8 (1) | O(1)—P(1)—O(4) | 104.6 (1) |
O(8)—Fe(1)—O(2)i | 82.4 (1) | O(2)—P(1)—O(4) | 106.7 (1) |
O(1)—Fe(1)—O(3)ii | 91.1 (1) | O(3)—P(1)—O(4) | 105.0 (1) |
O(8)—Fe(1)—O(3)ii | 109.2 (1) | O(4)—P(2)—O(5) | 106.0 (1) |
O(2)i—Fe(1)—O(3)ii | 160.8 (1) | O(4)—P(2)—O(6) | 106.3 (1) |
O(1)—Fe(1)—O(5)iii | 93.1 (1) | O(5)—P(2)—O(6) | 111.1 (1) |
O(8)—Fe(1)—O(5)iii | 167.9 (1) | O(4)—P(2)—O(7) | 104.0 (1) |
O(2)i—Fe(1)—O(5)iii | 86.2 (1) | O(5)—P(2)—O(7) | 114.5 (1) |
O(3)ii—Fe(1)—O(5)iii | 80.8 (1) | O(6)—P(2)—O(7) | 114.0 (1) |
O(1)—Fe(1)—O(6)ii | 173.6 (1) | Fe(1)—O(1)—P(1) | 133.5 (1) |
O(8)—Fe(1)—O(6)ii | 86.3 (1) | P(1)—O(2)—Fe(1)i | 132.1 (1) |
O(2)i—Fe(1)—O(6)ii | 82.5 (1) | P(1)—O(2)—Fe(2)vii | 126.2 (1) |
O(3)ii—Fe(1)—O(6)ii | 83.0 (1) | Fe(1)i—O(2)—Fe(2)vii | 97.9 (1) |
O(5)iii—Fe(1)—O(6)ii | 88.3 (1) | P(1)—O(3)—Fe(1)ii | 117.1 (1) |
O(6)—Fe(2)—O(9) | 84.3 (1) | P(1)—O(3)—Fe(2)viii | 137.2 (1) |
O(6)—Fe(2)—O(2)iv | 82.9 (1) | Fe(1)ii—O(3)—Fe(2)viii | 99.4 (1) |
O(9)—Fe(2)—O(2)iv | 88.8 (1) | P(1)—O(4)—P(2) | 125.9 (1) |
O(6)—Fe(2)—O(3)v | 106.3 (1) | P(2)—O(5)—Fe(1)ix | 125.4 (1) |
O(9)—Fe(2)—O(3)v | 96.3 (1) | P(2)—O(5)—Fe(2)vii | 126.6 (1) |
O(2)iv—Fe(2)—O(3)v | 169.9 (1) | Fe(1)ix—O(5)—Fe(2)vii | 97.9 (1) |
O(6)—Fe(2)—O(5)iv | 167.1 (1) | Fe(2)—O(6)—P(2) | 136.1 (1) |
O(9)—Fe(2)—O(5)iv | 84.8 (1) | Fe(2)—O(6)—Fe(1)ii | 95.3 (1) |
O(2)iv—Fe(2)—O(5)iv | 89.9 (1) | P(2)—O(6)—Fe(1)ii | 120.9 (1) |
O(3)v—Fe(2)—O(5)iv | 81.9 (1) | P(2)—O(7)—Fe(2)x | 129.3 (1) |
O(6)—Fe(2)—O(7)vi | 92.1 (1) | Fe(1)—O(8)—H(1) | 126 (3) |
O(9)—Fe(2)—O(7)vi | 172.9 (1) | Fe(1)—O(8)—H(2) | 116 (3) |
O(2)iv—Fe(2)—O(7)vi | 84.6 (1) | H(1)—O(8)—H(2) | 105 (5) |
O(3)v—Fe(2)—O(7)vi | 90.7 (1) | Fe(2)—O(9)—H(3) | 106 (3) |
O(5)iv—Fe(2)—O(7)vi | 97.8 (1) | Fe(2)—O(9)—H(4) | 120 (3) |
O(1)—P(1)—O(2) | 112.2 (1) | H(3)—O(9)—H(4) | 113 (4) |
O(1)—P(1)—O(3) | 115.4 (1) | | |
Symmetry codes: (i) −x+2, −y+1, −z; (ii) −x+1, −y+1, −z; (iii) −x+3/2, y+1/2, −z+1/2; (iv) x−1, y, z; (v) x−1/2, −y+1/2, z+1/2; (vi) x−1/2, −y+1/2, z−1/2; (vii) x+1, y, z; (viii) x+1/2, −y+1/2, z−1/2; (ix) −x+3/2, y−1/2, −z+1/2; (x) x+1/2, −y+1/2, z+1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O(8)—H(1)···O(7) | 0.85 (4) | 1.95 (4) | 2.770 (4) | 162 (4) |
O(8)—H(2) | 0.92 (6) | | | |
O(9)—H(3) | 0.85 (2) | | | |
O(9)—H(4)···O(5) | 0.95 (4) | 2.00 (4) | 2.898 (4) | 157 (4) |
Experimental details
Crystal data |
Chemical formula | Fe2P2O7(H2O)2 |
Mr | 321.7 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 297 |
a, b, c (Å) | 6.400 (2), 14.181 (3), 7.416 (1) |
β (°) | 95.43 (2) |
V (Å3) | 670.1 (2) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 4.83 |
Crystal size (mm) | 0.48 × 0.24 × 0.17 |
|
Data collection |
Diffractometer | Nicolet R 3m/V diffractometer |
Absorption correction | ψ scan (North et al., 1968) |
Tmin, Tmax | 0.185, 0.416 |
No. of measured, independent and observed [(F) > 4σ(F)] reflections | 1754, 1547, 1454 |
Rint | 0.016 |
(sin θ/λ)max (Å−1) | 0.650 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.019, 0.030, 1.18 |
No. of reflections | 1454 |
No. of parameters | 135 |
H-atom treatment | Isotropic |
Δρmax, Δρmin (e Å−3) | 0.55, −0.58 |
Selected geometric parameters (Å, º) topFe(1)—O(1) | 2.022 (2) | P(1)—O(1) | 1.505 (2) |
Fe(1)—O(8) | 2.142 (2) | P(1)—O(2) | 1.517 (1) |
Fe(1)—O(2)i | 2.130 (2) | P(1)—O(3) | 1.524 (1) |
Fe(1)—O(3)ii | 2.181 (2) | P(1)—O(4) | 1.614 (1) |
Fe(1)—O(5)iii | 2.166 (2) | P(2)—O(4) | 1.608 (1) |
Fe(1)—O(6)ii | 2.197 (1) | P(2)—O(5) | 1.532 (2) |
Fe(2)—O(6) | 2.167 (2) | P(2)—O(6) | 1.521 (1) |
Fe(2)—O(9) | 2.151 (2) | P(2)—O(7) | 1.511 (1) |
Fe(2)—O(2)iv | 2.144 (2) | O(8)—H(1) | 0.85 (4) |
Fe(2)—O(3)v | 2.118 (2) | O(8)—H(2) | 0.92 (6) |
Fe(2)—O(5)iv | 2.181 (2) | O(9)—H(3) | 0.85 (5) |
Fe(2)—O(7)vi | 2.081 (2) | O(9)—H(4) | 0.95 (4) |
| | | |
P(1)—O(4)—P(2) | 125.9 (1) | | |
Symmetry codes: (i) −x+2, −y+1, −z; (ii) −x+1, −y+1, −z; (iii) −x+3/2, y+1/2, −z+1/2; (iv) x−1, y, z; (v) x−1/2, −y+1/2, z+1/2; (vi) x−1/2, −y+1/2, z−1/2. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O(8)—H(1)···O(7) | 0.85 (4) | 1.95 (4) | 2.770 (4) | 162 (4) |
O(9)—H(4)···O(5) | 0.95 (4) | 2.00 (4) | 2.898 (4) | 157 (4) |
We have been interested in making low-density iron phosphates for the last few years (Korzenski et al., 1998). They exhibit interesting magnetic and structural properties, and can possibly form large microporous frameworks under appropriate conditions. Herein we report a new FeII diphosphate synthesized hydrothermally. The title compound crystallizes in the monoclinic space group P21/n. There are two crystallographically unique iron sites. Both have octahedral coordination with five diphosphate O atoms and one water oxygen. Two oxygen atoms are bridging, forming edge sharing iron octahedra. The Fe—O distances for both Fe(1) and Fe(2) range from 2.022 (2) to 2.197 (2) Å [average 2.14 (5) Å], in good agreement with those reported in a series of iron(II) phosphate hydrates (Moore & Araki, 1975; Warner et al., 1992), and iron diphosphates (Le Meins & Courbion, 1999). There are also two unique phosphorus sites. Both are tetrahedrally bound to four O atoms atoms and share a common vertex at O4 to form the diphosphate group. The average P—O distance for the terminal oxygen atoms is 1.518 Å (standard deviation 0.007 Å), those to the bridging oxygen atom are longer [1.608 (1) and 1.614 (1) Å], and the average O—P—O angle is 109° (standard deviation 4°), comparable to other iron phosphates (Warner et al., 1992; Stefanidis & Nord, 1982).
All of the atoms in the unit cell sit on general positions. The asymmetric unit (Fig. 1) shows the connectivity of the atoms and how they bond to symmetry-related units. The compound comprises edge-sharing iron octahedra that are linked by bridging diphosphates. This connectivity forms a cavity that houses the hydrogen atoms of the two water molecules (Fig. 2). Like most hydrated iron(II) phosphates the water molecules are coordinated to the iron (Mori & Ito, 1950; Eversheim & Kleber, 1953; Moore & Araki, 1976). One of the hydrogen atoms on each water is hydrogen-bonded to an oxygen of another iron. The remaining hydrogen atoms have no obvious interactions. The synthesis of this compound requires titanium oxide (TiO) to be present although it does not become incorporated into the compound, as confirmed by EDAX. Attempts to synthesize this compound in the absence of titanium oxide have not been successful.