Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102015251/br1386sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102015251/br1386Isup2.hkl |
Crystals of K3Fe5(PO4)6 were prepared by the flux method from K2CO3, (NH4)2HPO4, MoO3 and Fe(NO3)3·9H2O. The starting materials (equimolar ratio) were placed in a platinum crucible (in air) and heated at 1073 K for 1 h. The mixture was cooled to 773 K at a rate of 10 K h-1. Finally, parallelepipedic brown crystals of K3Fe5(PO4)6 were obtained after washing with boiling water.
Data collection: CAD-4 EXPRESS (Enraf Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1994); software used to prepare material for publication: SHELXL97.
K3Fe5(PO4)6 | F(000) = 1876 |
Mr = 966.37 | Dx = 3.006 Mg m−3 Dm = 3.05 (5) Mg m−3 Dm measured by pycnometry |
Monoclinic, C2/c | Ag Kα radiation, λ = 0.56087 Å |
Hall symbol: -C 2yc | Cell parameters from 25 reflections |
a = 6.460 (4) Å | θ = 7–12° |
b = 30.997 (7) Å | µ = 2.30 mm−1 |
c = 10.665 (2) Å | T = 293 K |
β = 90.22 (4)° | Parallelepiped, brown |
V = 2135.6 (15) Å3 | 0.30 × 0.20 × 0.16 mm |
Z = 4 |
Enraf-Nonius CAD-4 diffractometer | 3354 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.030 |
Graphite monochromator | θmax = 25.0°, θmin = 2.5° |
ω/2θ scans | h = −9→9 |
Absorption correction: analytical (Katayama, 1986) | k = −46→9 |
Tmin = 0.630, Tmax = 0.710 | l = −16→16 |
7763 measured reflections | 2 standard reflections every 120 min |
3823 independent reflections | intensity decay: 2% |
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)] = 0.019 | w = 1/[σ2(Fo2) + (0.0214P)2 + 4.5065P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.051 | (Δ/σ)max = 0.001 |
S = 1.08 | Δρmax = 0.76 e Å−3 |
3823 reflections | Δρmin = −0.79 e Å−3 |
177 parameters | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
0 restraints | Extinction coefficient: 0.00198 (13) |
K3Fe5(PO4)6 | V = 2135.6 (15) Å3 |
Mr = 966.37 | Z = 4 |
Monoclinic, C2/c | Ag Kα radiation, λ = 0.56087 Å |
a = 6.460 (4) Å | µ = 2.30 mm−1 |
b = 30.997 (7) Å | T = 293 K |
c = 10.665 (2) Å | 0.30 × 0.20 × 0.16 mm |
β = 90.22 (4)° |
Enraf-Nonius CAD-4 diffractometer | 3354 reflections with I > 2σ(I) |
Absorption correction: analytical (Katayama, 1986) | Rint = 0.030 |
Tmin = 0.630, Tmax = 0.710 | 2 standard reflections every 120 min |
7763 measured reflections | intensity decay: 2% |
3823 independent reflections |
R[F2 > 2σ(F2)] = 0.019 | 177 parameters |
wR(F2) = 0.051 | 0 restraints |
S = 1.08 | Δρmax = 0.76 e Å−3 |
3823 reflections | Δρmin = −0.79 e Å−3 |
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. |
x | y | z | Uiso*/Ueq | ||
Fe1 | 0.2500 | 0.2500 | 0.5000 | 0.00582 (6) | |
Fe2 | 0.0000 | 0.189384 (10) | 0.2500 | 0.00677 (6) | |
Fe3 | 0.0000 | 0.193115 (10) | 0.7500 | 0.00679 (6) | |
Fe4 | 0.24698 (3) | 0.049909 (7) | 0.57712 (2) | 0.00737 (5) | |
P1 | 0.0000 | 0.278396 (17) | 0.2500 | 0.00575 (9) | |
O11 | 0.18853 (17) | 0.30583 (4) | 0.22474 (11) | 0.00946 (19) | |
O12 | 0.03724 (17) | 0.24513 (3) | 0.35948 (10) | 0.00758 (18) | |
P2 | 0.0000 | 0.281775 (17) | 0.7500 | 0.00594 (9) | |
O21 | 0.03802 (17) | 0.24838 (4) | 0.64090 (10) | 0.00749 (18) | |
O22 | 0.18915 (17) | 0.30916 (4) | 0.77764 (11) | 0.00936 (19) | |
P3 | 0.14632 (6) | 0.148952 (12) | 0.50261 (3) | 0.00607 (7) | |
O31 | 0.01426 (18) | 0.14707 (4) | 0.38235 (11) | 0.0108 (2) | |
O32 | 0.00308 (18) | 0.15329 (4) | 0.61488 (11) | 0.0116 (2) | |
O33 | 0.27196 (18) | 0.10763 (4) | 0.51169 (12) | 0.0123 (2) | |
O34 | 0.29346 (17) | 0.18761 (3) | 0.49822 (10) | 0.00887 (19) | |
P4 | 0.24699 (6) | 0.030414 (12) | 0.87738 (4) | 0.00673 (7) | |
O41 | 0.22854 (19) | 0.02291 (4) | 0.73522 (11) | 0.0145 (2) | |
O42 | 0.44496 (18) | 0.05457 (4) | 0.91038 (13) | 0.0164 (2) | |
O43 | 0.06373 (19) | 0.05619 (4) | 0.92864 (13) | 0.0161 (2) | |
O44 | 0.2465 (2) | −0.01530 (4) | 0.93308 (12) | 0.0180 (2) | |
K1 | 0.64766 (6) | 0.138114 (15) | 0.51135 (4) | 0.02211 (9) | |
K2 | 0.0000 | 0.93923 (3) | 0.7500 | 0.0477 (2) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Fe1 | 0.00612 (12) | 0.00613 (12) | 0.00521 (11) | −0.00042 (9) | −0.00027 (9) | 0.00017 (9) |
Fe2 | 0.00683 (12) | 0.00698 (12) | 0.00649 (12) | 0.000 | −0.00057 (9) | 0.000 |
Fe3 | 0.00667 (12) | 0.00730 (13) | 0.00640 (12) | 0.000 | 0.00049 (9) | 0.000 |
Fe4 | 0.00765 (9) | 0.00694 (9) | 0.00752 (9) | −0.00004 (7) | −0.00081 (7) | 0.00029 (7) |
P1 | 0.00450 (19) | 0.0065 (2) | 0.0062 (2) | 0.000 | −0.00064 (15) | 0.000 |
O11 | 0.0062 (4) | 0.0103 (5) | 0.0118 (5) | −0.0018 (4) | −0.0004 (3) | 0.0020 (4) |
O12 | 0.0081 (4) | 0.0083 (4) | 0.0063 (4) | −0.0002 (3) | −0.0018 (3) | 0.0008 (3) |
P2 | 0.0047 (2) | 0.0066 (2) | 0.0065 (2) | 0.000 | 0.00025 (16) | 0.000 |
O21 | 0.0079 (4) | 0.0080 (4) | 0.0066 (4) | −0.0005 (3) | 0.0014 (3) | −0.0005 (3) |
O22 | 0.0066 (4) | 0.0108 (5) | 0.0107 (5) | −0.0020 (4) | 0.0002 (3) | −0.0017 (4) |
P3 | 0.00581 (14) | 0.00597 (14) | 0.00643 (14) | 0.00054 (11) | −0.00024 (11) | 0.00031 (11) |
O31 | 0.0124 (5) | 0.0117 (5) | 0.0083 (4) | −0.0026 (4) | −0.0032 (4) | 0.0021 (4) |
O32 | 0.0103 (5) | 0.0150 (5) | 0.0096 (5) | −0.0029 (4) | 0.0034 (4) | −0.0044 (4) |
O33 | 0.0077 (4) | 0.0069 (5) | 0.0223 (6) | 0.0009 (4) | 0.0013 (4) | 0.0033 (4) |
O34 | 0.0095 (4) | 0.0068 (4) | 0.0103 (5) | −0.0013 (3) | −0.0005 (4) | 0.0004 (4) |
P4 | 0.00469 (14) | 0.00813 (15) | 0.00736 (15) | −0.00038 (12) | −0.00054 (11) | 0.00131 (12) |
O41 | 0.0144 (5) | 0.0210 (6) | 0.0081 (5) | −0.0007 (4) | −0.0011 (4) | 0.0035 (4) |
O42 | 0.0067 (5) | 0.0192 (6) | 0.0233 (6) | −0.0026 (4) | −0.0015 (4) | −0.0058 (5) |
O43 | 0.0073 (5) | 0.0184 (6) | 0.0226 (6) | 0.0016 (4) | 0.0001 (4) | −0.0061 (5) |
O44 | 0.0285 (7) | 0.0120 (5) | 0.0137 (5) | 0.0005 (5) | 0.0002 (5) | 0.0050 (4) |
K1 | 0.00890 (15) | 0.0259 (2) | 0.0315 (2) | −0.00305 (13) | −0.00095 (14) | 0.00066 (16) |
K2 | 0.0578 (5) | 0.0224 (3) | 0.0628 (6) | 0.000 | −0.0302 (5) | 0.000 |
Fe1—O34i | 1.9544 (12) | P3—O33 | 1.5193 (12) |
Fe1—O34 | 1.9544 (12) | P3—O32 | 1.5220 (13) |
Fe1—O12i | 2.0351 (14) | P3—O34 | 1.5302 (12) |
Fe1—O12 | 2.0351 (14) | P3—O31 | 1.5387 (13) |
Fe1—O21 | 2.0376 (14) | P3—K1iv | 3.241 (2) |
Fe1—O21i | 2.0376 (14) | P3—K1 | 3.257 (2) |
Fe2—O31 | 1.9289 (12) | O31—K1iv | 2.757 (2) |
Fe2—O31ii | 1.9289 (12) | O31—K2vi | 3.0257 (15) |
Fe2—O22iii | 2.0312 (16) | O32—K1iv | 2.5870 (19) |
Fe2—O22i | 2.0312 (16) | O33—K1 | 2.6045 (18) |
Fe2—O12ii | 2.0987 (12) | O34—K1 | 2.7579 (17) |
Fe2—O12 | 2.0988 (12) | P4—O42 | 1.5220 (14) |
Fe2—P1 | 2.7591 (9) | P4—O43 | 1.5310 (14) |
Fe2—K1iv | 3.9400 (15) | P4—O44 | 1.5366 (13) |
Fe2—K1v | 3.9400 (15) | P4—O41 | 1.5380 (13) |
Fe2—K2vi | 3.9865 (12) | P4—K2xi | 3.5163 (11) |
Fe3—O32 | 1.8977 (12) | P4—K1ix | 3.6070 (9) |
Fe3—O32vii | 1.8977 (12) | O41—K2xi | 2.9890 (16) |
Fe3—O11viii | 2.0293 (16) | O42—Fe4ix | 1.9992 (17) |
Fe3—O11i | 2.0293 (17) | O42—K1ix | 2.7867 (15) |
Fe3—O21vii | 2.0859 (12) | O43—Fe4vii | 2.0173 (17) |
Fe3—O21 | 2.0859 (12) | O43—K1ix | 3.2132 (16) |
Fe3—P2 | 2.7482 (9) | O44—Fe4xii | 1.8736 (13) |
Fe3—K1iv | 3.8107 (15) | O44—K2xi | 2.8830 (18) |
Fe3—K1ix | 3.8107 (15) | K1—O32xiii | 2.5870 (19) |
Fe4—O44x | 1.8736 (13) | K1—O33 | 2.6045 (18) |
Fe4—O41 | 1.8867 (12) | K1—O31xiii | 2.757 (2) |
Fe4—O33 | 1.9273 (12) | K1—O34 | 2.7579 (17) |
Fe4—O42ix | 1.9992 (17) | K1—O42ix | 2.7867 (15) |
Fe4—O43vii | 2.0173 (17) | K1—O11xiv | 2.8746 (13) |
Fe4—K1 | 3.8316 (13) | K1—O22xv | 2.9934 (13) |
Fe4—K2vi | 3.8454 (13) | K1—O43ix | 3.2132 (16) |
P1—O11 | 1.5105 (13) | K1—P3xiii | 3.241 (2) |
P1—O11ii | 1.5105 (13) | K1—P4ix | 3.6070 (9) |
P1—O12 | 1.5756 (11) | K1—P1i | 3.7556 (9) |
P1—O12ii | 1.5756 (11) | K2—O44xvi | 2.8830 (18) |
P1—K1i | 3.7556 (9) | K2—O44xvii | 2.8830 (18) |
P1—K1iii | 3.7556 (9) | K2—O41xvi | 2.9890 (16) |
O11—Fe3i | 2.0293 (16) | K2—O41xvii | 2.9890 (16) |
O11—K1iii | 2.8746 (13) | K2—O31vi | 3.0257 (15) |
P2—O22vii | 1.5158 (13) | K2—O31xviii | 3.0257 (15) |
P2—O22 | 1.5158 (13) | K2—P4xvi | 3.5163 (11) |
P2—O21 | 1.5772 (11) | K2—P4xvii | 3.5163 (11) |
P2—O21vii | 1.5772 (12) | K2—Fe4xviii | 3.8454 (13) |
P2—K1viii | 3.8503 (9) | K2—Fe4vi | 3.8454 (13) |
P2—K1i | 3.8503 (9) | K2—Fe2vi | 3.9865 (13) |
O22—Fe2i | 2.0312 (16) | K2—K1xix | 4.3296 (15) |
O22—K1viii | 2.9934 (13) | ||
O34i—Fe1—O34 | 180.0 | O22vii—P2—O22 | 111.89 (10) |
O34i—Fe1—O12i | 90.92 (5) | O22vii—P2—O21 | 110.59 (6) |
O34—Fe1—O12i | 89.08 (5) | O22—P2—O21 | 112.54 (7) |
O34i—Fe1—O12 | 89.08 (5) | O22vii—P2—O21vii | 112.54 (7) |
O34—Fe1—O12 | 90.92 (5) | O22—P2—O21vii | 110.59 (6) |
O12i—Fe1—O12 | 180.0 | O21—P2—O21vii | 97.97 (9) |
O34i—Fe1—O21 | 85.42 (5) | O33—P3—O32 | 110.52 (7) |
O34—Fe1—O21 | 94.58 (5) | O33—P3—O34 | 109.29 (7) |
O12i—Fe1—O21 | 84.99 (6) | O32—P3—O34 | 109.54 (7) |
O12—Fe1—O21 | 95.01 (6) | O33—P3—O31 | 108.39 (7) |
O34i—Fe1—O21i | 94.58 (5) | O32—P3—O31 | 108.80 (8) |
O34—Fe1—O21i | 85.42 (5) | O34—P3—O31 | 110.28 (7) |
O12i—Fe1—O21i | 95.01 (6) | O42—P4—O43 | 108.11 (8) |
O12—Fe1—O21i | 84.99 (6) | O42—P4—O44 | 111.53 (8) |
O21—Fe1—O21i | 180.0 | O43—P4—O44 | 109.92 (8) |
O31—Fe2—O31ii | 94.31 (7) | O42—P4—O41 | 111.36 (8) |
O31—Fe2—O22iii | 87.33 (6) | O43—P4—O41 | 111.95 (8) |
O31ii—Fe2—O22iii | 94.41 (6) | O44—P4—O41 | 103.96 (7) |
O31—Fe2—O22i | 94.41 (6) | O32xiii—K1—O33 | 152.98 (5) |
O31ii—Fe2—O22i | 87.33 (6) | O32xiii—K1—O31xiii | 55.39 (5) |
O22iii—Fe2—O22i | 177.45 (6) | O33—K1—O31xiii | 147.07 (5) |
O31—Fe2—O12ii | 166.43 (5) | O32xiii—K1—O34 | 130.94 (5) |
O31ii—Fe2—O12ii | 98.49 (5) | O33—K1—O34 | 55.18 (5) |
O22iii—Fe2—O12ii | 87.20 (5) | O31xiii—K1—O34 | 129.25 (5) |
O22i—Fe2—O12ii | 90.70 (5) | O32xiii—K1—O42ix | 103.44 (4) |
O31—Fe2—O12 | 98.49 (5) | O33—K1—O42ix | 57.40 (4) |
O31ii—Fe2—O12 | 166.43 (5) | O31xiii—K1—O42ix | 115.39 (4) |
O22iii—Fe2—O12 | 90.70 (5) | O34—K1—O42ix | 110.68 (5) |
O22i—Fe2—O12 | 87.20 (5) | O32xiii—K1—O11xiv | 58.23 (4) |
O12ii—Fe2—O12 | 69.17 (6) | O33—K1—O11xiv | 107.51 (5) |
O32—Fe3—O32vii | 98.84 (8) | O31xiii—K1—O11xiv | 104.93 (4) |
O32—Fe3—O11viii | 85.58 (6) | O34—K1—O11xiv | 77.15 (5) |
O32vii—Fe3—O11viii | 95.63 (6) | O42ix—K1—O11xiv | 110.10 (4) |
O32—Fe3—O11i | 95.63 (6) | O32xiii—K1—O22xv | 100.02 (5) |
O32vii—Fe3—O11i | 85.58 (6) | O33—K1—O22xv | 106.60 (5) |
O11viii—Fe3—O11i | 178.15 (7) | O31xiii—K1—O22xv | 56.62 (4) |
O32—Fe3—O21vii | 163.62 (5) | O34—K1—O22xv | 74.39 (5) |
O32vii—Fe3—O21vii | 96.26 (5) | O42ix—K1—O22xv | 140.97 (4) |
O11viii—Fe3—O21vii | 86.68 (5) | O11xiv—K1—O22xv | 108.72 (4) |
O11i—Fe3—O21vii | 91.81 (5) | O32xiii—K1—O43ix | 62.96 (4) |
O32—Fe3—O21 | 96.26 (5) | O33—K1—O43ix | 104.65 (5) |
O32vii—Fe3—O21 | 163.62 (5) | O31xiii—K1—O43ix | 71.34 (4) |
O11viii—Fe3—O21 | 91.81 (5) | O34—K1—O43ix | 158.49 (4) |
O11i—Fe3—O21 | 86.68 (5) | O42ix—K1—O43ix | 48.01 (4) |
O21vii—Fe3—O21 | 69.57 (6) | O11xiv—K1—O43ix | 105.57 (4) |
O44x—Fe4—O41 | 118.61 (6) | O22xv—K1—O43ix | 122.93 (4) |
O44x—Fe4—O33 | 103.56 (6) | O44xvi—K2—O44xvii | 121.47 (6) |
O41—Fe4—O33 | 137.82 (6) | O44xvi—K2—O41xvi | 48.68 (4) |
O44x—Fe4—O42ix | 95.42 (7) | O44xvii—K2—O41xvi | 79.15 (5) |
O41—Fe4—O42ix | 92.22 (6) | O44xvi—K2—O41xvii | 79.15 (5) |
O33—Fe4—O42ix | 82.67 (5) | O44xvii—K2—O41xvii | 48.68 (4) |
O44x—Fe4—O43vii | 91.83 (7) | O41xvi—K2—O41xvii | 59.59 (6) |
O41—Fe4—O43vii | 90.22 (7) | O44xvi—K2—O31vi | 139.81 (4) |
O33—Fe4—O43vii | 89.08 (5) | O44xvii—K2—O31vi | 95.77 (4) |
O42ix—Fe4—O43vii | 170.10 (6) | O41xvi—K2—O31vi | 139.18 (4) |
O11—P1—O11ii | 111.48 (10) | O41xvii—K2—O31vi | 141.04 (4) |
O11—P1—O12 | 112.32 (7) | O44xvi—K2—O31xviii | 95.77 (4) |
O11ii—P1—O12 | 110.93 (7) | O44xvii—K2—O31xviii | 139.81 (4) |
O11—P1—O12ii | 110.93 (7) | O41xvi—K2—O31xviii | 141.04 (4) |
O11ii—P1—O12ii | 112.32 (7) | O41xvii—K2—O31xviii | 139.18 (4) |
O12—P1—O12ii | 98.24 (9) | O31vi—K2—O31xviii | 55.73 (5) |
Symmetry codes: (i) −x+1/2, −y+1/2, −z+1; (ii) −x, y, −z+1/2; (iii) x−1/2, −y+1/2, z−1/2; (iv) x−1, y, z; (v) −x+1, y, −z+1/2; (vi) −x, −y+1, −z+1; (vii) −x, y, −z+3/2; (viii) x−1/2, −y+1/2, z+1/2; (ix) −x+1, y, −z+3/2; (x) x, −y, z−1/2; (xi) x, y−1, z; (xii) x, −y, z+1/2; (xiii) x+1, y, z; (xiv) x+1/2, −y+1/2, z+1/2; (xv) x+1/2, −y+1/2, z−1/2; (xvi) x, y+1, z; (xvii) −x, y+1, −z+3/2; (xviii) x, −y+1, z+1/2; (xix) x−1, −y+1, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | K3Fe5(PO4)6 |
Mr | 966.37 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 293 |
a, b, c (Å) | 6.460 (4), 30.997 (7), 10.665 (2) |
β (°) | 90.22 (4) |
V (Å3) | 2135.6 (15) |
Z | 4 |
Radiation type | Ag Kα, λ = 0.56087 Å |
µ (mm−1) | 2.30 |
Crystal size (mm) | 0.30 × 0.20 × 0.16 |
Data collection | |
Diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | Analytical (Katayama, 1986) |
Tmin, Tmax | 0.630, 0.710 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 7763, 3823, 3354 |
Rint | 0.030 |
(sin θ/λ)max (Å−1) | 0.753 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.019, 0.051, 1.08 |
No. of reflections | 3823 |
No. of parameters | 177 |
Δρmax, Δρmin (e Å−3) | 0.76, −0.79 |
Computer programs: CAD-4 EXPRESS (Enraf Nonius, 1994), CAD-4 EXPRESS, XCAD4 (Harms & Wocadlo, 1995), SIR92 (Altomare et al., 1993), SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 1994), SHELXL97.
Fe1—O34i | 1.9544 (12) | P3—O32 | 1.5220 (13) |
Fe1—O12i | 2.0351 (14) | P3—O34 | 1.5302 (12) |
Fe1—O21 | 2.0376 (14) | P3—O31 | 1.5387 (13) |
Fe2—O31 | 1.9289 (12) | P4—O42 | 1.5220 (14) |
Fe2—O22ii | 2.0312 (16) | P4—O43 | 1.5310 (14) |
Fe2—O12iii | 2.0987 (12) | P4—O44 | 1.5366 (13) |
Fe3—O32 | 1.8977 (12) | P4—O41 | 1.5380 (13) |
Fe3—O11iv | 2.0293 (16) | K1—O32viii | 2.5870 (19) |
Fe3—O21v | 2.0859 (12) | K1—O33 | 2.6045 (18) |
Fe4—O44vi | 1.8736 (13) | K1—O31viii | 2.757 (2) |
Fe4—O41 | 1.8867 (12) | K1—O34 | 2.7579 (17) |
Fe4—O33 | 1.9273 (12) | K1—O42vii | 2.7867 (15) |
Fe4—O42vii | 1.9992 (17) | K1—O11ix | 2.8746 (13) |
Fe4—O43v | 2.0173 (17) | K1—O22x | 2.9934 (13) |
P1—O11 | 1.5105 (13) | K1—O43vii | 3.2132 (16) |
P1—O12 | 1.5756 (11) | K2—O44xi | 2.8830 (18) |
P2—O22v | 1.5158 (13) | K2—O41xi | 2.9890 (16) |
P2—O21 | 1.5772 (11) | K2—O31xii | 3.0257 (15) |
P3—O33 | 1.5193 (12) | ||
O34i—Fe1—O12i | 90.92 (5) | O44vi—Fe4—O42vii | 95.42 (7) |
O34—Fe1—O12i | 89.08 (5) | O41—Fe4—O42vii | 92.22 (6) |
O34i—Fe1—O21 | 85.42 (5) | O33—Fe4—O42vii | 82.67 (5) |
O34—Fe1—O21 | 94.58 (5) | O44vi—Fe4—O43v | 91.83 (7) |
O12i—Fe1—O21 | 84.99 (6) | O41—Fe4—O43v | 90.22 (7) |
O12—Fe1—O21 | 95.01 (6) | O33—Fe4—O43v | 89.08 (5) |
O31—Fe2—O31iii | 94.31 (7) | O42vii—Fe4—O43v | 170.10 (6) |
O31—Fe2—O22ii | 87.33 (6) | O11—P1—O11iii | 111.48 (10) |
O31iii—Fe2—O22ii | 94.41 (6) | O11—P1—O12 | 112.32 (7) |
O22ii—Fe2—O22i | 177.45 (6) | O11iii—P1—O12 | 110.93 (7) |
O31—Fe2—O12iii | 166.43 (5) | O12—P1—O12iii | 98.24 (9) |
O31iii—Fe2—O12iii | 98.49 (5) | O22v—P2—O22 | 111.89 (10) |
O22ii—Fe2—O12iii | 87.20 (5) | O22v—P2—O21 | 110.59 (6) |
O22i—Fe2—O12iii | 90.70 (5) | O22—P2—O21 | 112.54 (7) |
O12iii—Fe2—O12 | 69.17 (6) | O21—P2—O21v | 97.97 (9) |
O32—Fe3—O32v | 98.84 (8) | O33—P3—O32 | 110.52 (7) |
O32—Fe3—O11iv | 85.58 (6) | O33—P3—O34 | 109.29 (7) |
O32v—Fe3—O11iv | 95.63 (6) | O32—P3—O34 | 109.54 (7) |
O11iv—Fe3—O11i | 178.15 (7) | O33—P3—O31 | 108.39 (7) |
O32—Fe3—O21v | 163.62 (5) | O32—P3—O31 | 108.80 (8) |
O32v—Fe3—O21v | 96.26 (5) | O34—P3—O31 | 110.28 (7) |
O11iv—Fe3—O21v | 86.68 (5) | O42—P4—O43 | 108.11 (8) |
O11i—Fe3—O21v | 91.81 (5) | O42—P4—O44 | 111.53 (8) |
O21v—Fe3—O21 | 69.57 (6) | O43—P4—O44 | 109.92 (8) |
O44vi—Fe4—O41 | 118.61 (6) | O42—P4—O41 | 111.36 (8) |
O44vi—Fe4—O33 | 103.56 (6) | O43—P4—O41 | 111.95 (8) |
O41—Fe4—O33 | 137.82 (6) | O44—P4—O41 | 103.96 (7) |
Symmetry codes: (i) −x+1/2, −y+1/2, −z+1; (ii) x−1/2, −y+1/2, z−1/2; (iii) −x, y, −z+1/2; (iv) x−1/2, −y+1/2, z+1/2; (v) −x, y, −z+3/2; (vi) x, −y, z−1/2; (vii) −x+1, y, −z+3/2; (viii) x+1, y, z; (ix) x+1/2, −y+1/2, z+1/2; (x) x+1/2, −y+1/2, z−1/2; (xi) x, y+1, z; (xii) −x, −y+1, −z+1. |
Subscribe to Acta Crystallographica Section C: Structural Chemistry
The full text of this article is available to subscribers to the journal.
- Information on subscribing
- Sample issue
- Purchase subscription
- Reduced-price subscriptions
- If you have already subscribed, you may need to register
Iron phosphates generate considerable interest not only for their magnetic properties, due to the great number of possible different cation arrangements, but also for their potential practical applications, including corrosion inhibition (Meisel et al., 1983), passivation of metal surfaces (Attali et al.,1980) and heterogeneous catalysis (Moffat, 1978). These materials offer a considerable number of complex and versatile network structures due to the ability of iron to be in both the +2 and +3 oxidation states, and to adopt various coordination environments. In the monophosphates, iron(III) coordinates, in most cases, to six O atoms and rarely with five O atoms (Belkhiria et al., 1998; Pintard-Screpel et al., 1978; Andrew-Allen et al., 1988). It is four-coordinated in a few cases, such as in FePO4 (Ng & Calvo, 1975). Moreover, it can exhibit two different coordination modes in the same structure, such as in K3Fe2(PO4)3 (Pintard-Screpel et al., 1983) and Cs7Fe7(PO4)8O2 (Andrew-Allen et al., 1988), in which iron(III) adopts five- and six-coordination. The potassium iron phosphate K3Fe5(PO4)6 reported in this paper, falls into the latter category of compounds.
Fig. 1 illustrates the complete crystal structure of K3Fe5(PO4)6 projected along the [100] direction. There are four crystallographically distinct Fe atoms in this structure. Fe1 is located on a center of symmetry, Fe2 and Fe3 lie on twofold axes and Fe4 is located in a general position. The Fe atoms are both five- and six-coordinated. Atoms P1, P2 and K2 lie on twofold axes, while atoms P3, P4 and K1 are in general positions. The K3Fe5(PO4)6 structure consists of a three-dimensional complex framework constructed of iron polyhedra connected to each other by corner-linkage or by phosphate tetrahedra via corner- and edge-sharing. The structure can be easily described as the association of two building blocks. The first gathers Fe1, Fe2 and Fe3 octahedra, P1, P2 and P3 tetrahedra and K atoms. It consists of iron–phosphate layers, in the ac plane, with the interlayer space filled with K+ cations, as illustrated in the perspective view parallel to the [100] direction shown in Fig. 1. There are two iron–phosphate layers within the repeat distance b; each layer lies on a medium plane perpendicular to the b axis at y = 1/4 and y = 3/4. The layers are formed by corner-sharing FeO6 octahedra, which are further connected by phosphate tetrahedra through corner- and edge-sharing. The mode of association involved by the iron octahedra and the phosphorus tetrahedra in layers is pointed in Fig. 2. Each Fe1O6 octahedron shares a first corner with, at once, one Fe2O6 octahedron and one P1O4 tetrahedron, a second corner with, at once, one Fe3O6 octahedron and one P2O4 tetrahedron, and finally, a third corner with a P3O4 tetrahedron. The P1O4 and P2O4 tetrahedra share one edge, respectively, with Fe2O6 and Fe3O6 octahedra, and corners of the common edge with two different Fe1O6 octahedra. The remaining corners are coordinated to two Fe3O6 octahedra for P1O4, and two Fe2O6 octahedra for P2O4. P3O4 coordinates to Fe atoms (Fe1, Fe2 and Fe3) through three O atoms. The distortion observed in the Fe2O6 and Fe3O6 octahedra, and in the P1O4 and P2O4 tetrahedra is a result of the edge-sharing between these polyhedra, since the existence of the common edge induces a strong repulsion between the positive charges carried by the Fe and P atoms, and consequently atoms Fe2, Fe3, P1 and P2 are forced to shift to off-centred positions of their respective polyhedra and the lengths of the common edges are shorter than the other O···O distances in order to screen efficiently this repulsion effect. It is of interest to remark that atoms O31, O32 and O34 all bond to P and only one Fe, whereas atoms O11, O12, O21 and O22 bond to P and two Fe atoms. Thus, the Fe—O bonds are weaker when the O atom bonds to two Fe atoms, as one would expect. The sharing of edges also affects the geometry, but it may only be possible because the Fe—O bonds are already longer. Fig. 3 shows the atomic displacement ellipsoids in layers.
The structural arrangement adopted by the first building block is similar to that observed in the K3Fe3(PO4)4·H2O structure (Lii, 1995), which is made up of layers involving corner-linkage between FeO6 octahedra, and corner- and edge-sharing between FeO6 octahedra and PO4 tetrahedra. The layers are linked by seven- or six-oxygen coordinated K+ cations and hydrogen bonding.
The second building block formed by Fe4 and P4O4 tetrahedra is found in the interlayer space between the first building blocks, which has a result of destroying the layered arrangement. Atom Fe4 is pentacoordinated and shares its corners with one P3O4 and four different P4O4 tetrahedra. Fe4O5 polyhedra are connected to each other and to the other iron octahedra by phosphate tetrahedra via corner-sharing. The average Fe4—O distances is 1.941 Å, a value close to that observed in K3Fe2(PO4)3 for pentacoordinated iron (1.935 Å; Pintard-Screpel et al., 1983). Each P4O4 tetrahedron shares its four corners with four different Fe4O5 polyhedra.
The three-dimensional structural arrangement formed by the P, Fe and O atoms contains interstitial spaces forming intersecting channels in which the K atoms are located. K1 has an environment formed by eight O atoms, with K—O distances ranging from 2.587 (2) to 3.213 (2) Å, while K2 is six-coordinated, with K—O distances between 2.883 (2) and 3.025 (2) Å. The coordination number of each K+ cation was determined on the basis of the maximum cation–anion distance; Lmax = 3.35 Å for K—O according to Donnay & Allman (1970).