Crystals of the title compound, (NH
4)
4[H
6NiMo
6O
24]·4H
2O containing the well known
B-type Anderson-Evans heteropolyoxometalate, were obtained by recrystallization of powder (NH
4)
4[H
6NiMo
6O
24]·
nH
2O. The anion has the Ni atom at an inversion center and has close to
m symmetry, with Ni-O bond lengths in the range 2.046 (5)-2.052 (6), Mo-O bond lengths in the ranges 1.701 (6)-1.720 (6), 1.932 (6)-1.954 (7) and 2.216 (6)-2.258 (5) Å.
Supporting information
Key indicators
- Single-crystal X-ray study
- T = 298 K
- Mean (Ni-O) = 0.006 Å
- H-atom completeness 1%
- R factor = 0.053
- wR factor = 0.137
- Data-to-parameter ratio = 18.5
checkCIF results
No syntax errors found
ADDSYM reports no extra symmetry
General Notes
FORMU_01 There is a discrepancy between the atom counts in the
_chemical_formula_sum and the formula from the _atom_site* data.
Atom count from _chemical_formula_sum:H30 Mo6 N4 Ni1 O28
Atom count from the _atom_site data: Mo6 N4 Ni1 O28
CELLZ_01
From the CIF: _cell_formula_units_Z 2
From the CIF: _chemical_formula_sum H30 Mo6 N4 Ni O28
TEST: Compare cell contents of formula and atom_site data
atom Z*formula cif sites diff
H 60.00 0.00 60.00
Mo 12.00 12.00 0.00
N 8.00 8.00 0.00
Ni 2.00 2.00 0.00
O 56.00 56.00 0.00
Difference between formula and atom_site contents detected.
WARNING: H atoms missing from atom site list. Is this intentional?
CHEMW_03
From the CIF: _cell_formula_units_Z 2
From the CIF: _chemical_formula_weight 1168.63
TEST: Calculate formula weight from _atom_site_*
atom mass num sum
Ni 58.69 1.00 58.69
Mo 95.94 6.00 575.64
O 16.00 28.00 447.97
H 1.01 0.00 0.00
N 14.01 4.00 56.03
Calculated formula weight 1138.33
The ratio of given/expected molecular weight as calculated
from the _atom_site* data lies outside
the range 0.99 <> 1.01
The title compound was obtained by recrystallization of the powder
(NH4)4[H6CoMo6O24].nH2O at pH 5.35. The powder was obtained by the
reaction of (NH4)4[H6CoMo6O24]·4H2O with Ni(NO3). Elemental
analysis, calculated: N 4.79 H 2.57%; found: N 4.78 H 2.59%.
Data collection: STADI4 (Stoe & Cie, 1996); cell refinement: STADI4; data reduction: X-RED (Stoe & Cie, 1996); program(s) used to solve structure: SHELXS97-2 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97-2 (Sheldrick, 1997); molecular graphics: ORTEP-3 (Farrugia, 1997).
Crystal data top
(NH4)4[H6NiMo6O24]·4H2O | F(000) = 1124 |
Mr = 1168.63 | Dx = 2.706 Mg m−3 |
Monoclinic, P21/a | Mo Kα radiation, λ = 0.71069 Å |
a = 11.994 (3) Å | Cell parameters from 27 reflections |
b = 11.131 (2) Å | θ = 9.5–10.5° |
c = 11.384 (9) Å | µ = 3.29 mm−1 |
β = 109.31 (8)° | T = 298 K |
V = 1434.3 (12) Å3 | Octagonal plate, pale blue |
Z = 2 | 0.25 × 0.19 × 0.10 mm |
Data collection top
Stoe STADI4 diffractometer | 2448 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.000 |
Graphite monochromator | θmax = 27.6°, θmin = 1.9° |
ω/2–θ scans | h = −15→14 |
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1996) | k = 0→14 |
Tmin = 0.542, Tmax = 0.849 | l = 0→14 |
3290 measured reflections | 3 standard reflections every 60 min |
3290 independent reflections | intensity decay: 4.9% |
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)] = 0.053 | H-atom parameters not refined |
wR(F2) = 0.137 | w = 1/[σ2(Fo2) + (0.0508P)2 + 13.3268P] where P = (Fo2 + 2Fc2)/3 |
S = 1.13 | (Δ/σ)max < 0.001 |
3290 reflections | Δρmax = 1.11 e Å−3 |
178 parameters | Δρmin = −1.33 e Å−3 |
0 restraints | |
Crystal data top
(NH4)4[H6NiMo6O24]·4H2O | V = 1434.3 (12) Å3 |
Mr = 1168.63 | Z = 2 |
Monoclinic, P21/a | Mo Kα radiation |
a = 11.994 (3) Å | µ = 3.29 mm−1 |
b = 11.131 (2) Å | T = 298 K |
c = 11.384 (9) Å | 0.25 × 0.19 × 0.10 mm |
β = 109.31 (8)° | |
Data collection top
Stoe STADI4 diffractometer | 2448 reflections with I > 2σ(I) |
Absorption correction: numerical (X-SHAPE; Stoe & Cie, 1996) | Rint = 0.000 |
Tmin = 0.542, Tmax = 0.849 | 3 standard reflections every 60 min |
3290 measured reflections | intensity decay: 4.9% |
3290 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.053 | 0 restraints |
wR(F2) = 0.137 | H-atom parameters not refined |
S = 1.13 | w = 1/[σ2(Fo2) + (0.0508P)2 + 13.3268P] where P = (Fo2 + 2Fc2)/3 |
3290 reflections | Δρmax = 1.11 e Å−3 |
178 parameters | Δρmin = −1.33 e Å−3 |
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 | |
Ni | 0.0000 | 0.5000 | 0.5000 | 0.0179 (3) | |
Mo1 | −0.14146 (6) | 0.73868 (7) | 0.34545 (7) | 0.02361 (19) | |
Mo2 | −0.04799 (6) | 0.73730 (6) | 0.65370 (7) | 0.02200 (19) | |
Mo3 | 0.08826 (6) | 0.49667 (7) | 0.80890 (7) | 0.02484 (19) | |
Oc1 | 0.0094 (4) | 0.6117 (5) | 0.3602 (5) | 0.0195 (11) | |
Oc2 | −0.1353 (5) | 0.6123 (5) | 0.4992 (5) | 0.0186 (11) | |
Oc3 | 0.0932 (5) | 0.6076 (5) | 0.6451 (5) | 0.0198 (11) | |
Ob4 | −0.0367 (5) | 0.8065 (5) | 0.5011 (6) | 0.0260 (13) | |
Ob5 | −0.0484 (5) | 0.6007 (5) | 0.7610 (6) | 0.0261 (13) | |
Ob6 | 0.2014 (5) | 0.3958 (6) | 0.7650 (6) | 0.0280 (13) | |
Ot7 | −0.0983 (6) | 0.8352 (6) | 0.2516 (7) | 0.0396 (17) | |
Ot8 | −0.2758 (6) | 0.7938 (6) | 0.3442 (7) | 0.0372 (16) | |
Ot9 | −0.1786 (5) | 0.7961 (6) | 0.6546 (6) | 0.0314 (14) | |
Ot10 | 0.0573 (6) | 0.8287 (6) | 0.7522 (6) | 0.0334 (15) | |
Ot11 | 0.1940 (6) | 0.5839 (7) | 0.9124 (6) | 0.0401 (17) | |
Ot12 | 0.0416 (7) | 0.4040 (6) | 0.9029 (7) | 0.0396 (16) | |
Ow2 | 0.0669 (10) | 0.1747 (9) | 1.0224 (9) | 0.076 (3) | |
Ow1 | 0.3563 (6) | 0.4568 (7) | 0.5110 (10) | 0.062 (3) | |
N2 | −0.2312 (7) | 0.5287 (8) | 0.8337 (8) | 0.0376 (19) | |
N1 | 0.4254 (8) | 0.4702 (9) | 0.8146 (10) | 0.047 (2) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Ni | 0.0194 (6) | 0.0129 (6) | 0.0244 (7) | 0.0014 (5) | 0.0113 (5) | 0.0006 (6) |
Mo1 | 0.0245 (4) | 0.0174 (3) | 0.0312 (4) | 0.0046 (3) | 0.0122 (3) | 0.0039 (3) |
Mo2 | 0.0225 (3) | 0.0161 (3) | 0.0305 (4) | 0.0013 (3) | 0.0129 (3) | −0.0024 (3) |
Mo3 | 0.0275 (4) | 0.0235 (4) | 0.0247 (4) | 0.0022 (3) | 0.0102 (3) | 0.0006 (3) |
Oc1 | 0.018 (3) | 0.017 (3) | 0.026 (3) | 0.001 (2) | 0.010 (2) | 0.002 (2) |
Oc2 | 0.020 (3) | 0.013 (3) | 0.025 (3) | 0.001 (2) | 0.010 (2) | −0.001 (2) |
Oc3 | 0.020 (3) | 0.018 (3) | 0.024 (3) | 0.002 (2) | 0.010 (2) | −0.004 (2) |
Ob4 | 0.031 (3) | 0.016 (3) | 0.034 (3) | 0.001 (2) | 0.015 (3) | 0.001 (3) |
Ob5 | 0.028 (3) | 0.024 (3) | 0.034 (3) | 0.005 (2) | 0.020 (3) | 0.000 (3) |
Ob6 | 0.026 (3) | 0.027 (3) | 0.032 (3) | 0.006 (2) | 0.010 (3) | 0.002 (3) |
Ot7 | 0.054 (4) | 0.031 (4) | 0.039 (4) | 0.007 (3) | 0.023 (3) | 0.011 (3) |
Ot8 | 0.033 (3) | 0.038 (4) | 0.045 (4) | 0.011 (3) | 0.019 (3) | 0.003 (3) |
Ot9 | 0.029 (3) | 0.033 (3) | 0.036 (4) | 0.008 (3) | 0.015 (3) | −0.001 (3) |
Ot10 | 0.034 (3) | 0.028 (3) | 0.039 (4) | −0.003 (3) | 0.013 (3) | −0.008 (3) |
Ot11 | 0.040 (4) | 0.041 (4) | 0.035 (4) | −0.001 (3) | 0.006 (3) | −0.006 (3) |
Ot12 | 0.056 (4) | 0.033 (4) | 0.036 (4) | 0.007 (3) | 0.024 (3) | 0.009 (3) |
Ow2 | 0.123 (9) | 0.051 (5) | 0.060 (6) | −0.012 (6) | 0.036 (6) | 0.002 (5) |
Ow1 | 0.038 (4) | 0.024 (4) | 0.142 (9) | 0.001 (3) | 0.053 (5) | −0.005 (5) |
N2 | 0.034 (4) | 0.041 (5) | 0.041 (5) | −0.005 (4) | 0.016 (4) | 0.003 (4) |
N1 | 0.044 (5) | 0.039 (5) | 0.064 (6) | −0.002 (4) | 0.023 (5) | −0.007 (5) |
Geometric parameters (Å, º) top
Ni—Oc2i | 2.046 (5) | Mo2—Ot10 | 1.717 (7) |
Ni—Oc2 | 2.046 (5) | Mo2—Ob4 | 1.946 (6) |
Ni—Oc3i | 2.047 (6) | Mo2—Ob5 | 1.952 (6) |
Ni—Oc3 | 2.047 (6) | Mo2—Oc2 | 2.216 (6) |
Ni—Oc1 | 2.052 (6) | Mo2—Oc3 | 2.252 (5) |
Ni—Oc1i | 2.052 (6) | Mo3—Ot12 | 1.708 (7) |
Mo1—Ot7 | 1.712 (7) | Mo3—Ot11 | 1.718 (7) |
Mo1—Ot8 | 1.720 (6) | Mo3—Ob5 | 1.932 (6) |
Mo1—Ob6i | 1.935 (6) | Mo3—Ob6 | 1.949 (6) |
Mo1—Ob4 | 1.954 (7) | Mo3—Oc1i | 2.245 (6) |
Mo1—Oc2 | 2.228 (6) | Mo3—Oc3 | 2.254 (6) |
Mo1—Oc1 | 2.258 (5) | Ow1—N1 | 3.281 (15) |
Mo2—Ot9 | 1.701 (6) | | |
| | | |
Oc2i—Ni—Oc2 | 180.000 (1) | Ob5—Mo2—Oc2 | 84.8 (2) |
Oc2—Ni—Oc3i | 97.6 (2) | Ot9—Mo2—Oc3 | 162.6 (3) |
Oc2—Ni—Oc3 | 82.4 (2) | Ot10—Mo2—Oc3 | 90.4 (3) |
Oc3i—Ni—Oc3 | 180.000 (1) | Ob4—Mo2—Oc3 | 86.5 (2) |
Oc2i—Ni—Oc1 | 97.3 (2) | Ob5—Mo2—Oc3 | 71.7 (2) |
Oc2—Ni—Oc1 | 82.7 (2) | Oc2—Mo2—Oc3 | 74.2 (2) |
Oc3i—Ni—Oc1 | 83.4 (2) | Ot12—Mo3—Ot11 | 103.4 (4) |
Oc3—Ni—Oc1 | 96.6 (2) | Ot12—Mo3—Ob5 | 96.6 (3) |
Oc1—Ni—Oc1i | 180.000 (1) | Ot11—Mo3—Ob5 | 102.7 (3) |
Ot7—Mo1—Ot8 | 104.3 (3) | Ot12—Mo3—Ob6 | 102.3 (3) |
Ot7—Mo1—Ob6i | 101.8 (3) | Ot11—Mo3—Ob6 | 94.7 (3) |
Ot8—Mo1—Ob6i | 97.2 (3) | Ob5—Mo3—Ob6 | 150.5 (3) |
Ot7—Mo1—Ob4 | 95.0 (3) | Ot12—Mo3—Oc1i | 91.5 (3) |
Ot8—Mo1—Ob4 | 100.9 (3) | Ot11—Mo3—Oc1i | 161.6 (3) |
Ob6i—Mo1—Ob4 | 151.4 (2) | Ob5—Mo3—Oc1i | 85.8 (2) |
Ot7—Mo1—Oc2 | 161.5 (3) | Ob6—Mo3—Oc1i | 71.4 (2) |
Ot8—Mo1—Oc2 | 91.1 (3) | Ot12—Mo3—Oc3 | 162.3 (3) |
Ob6i—Mo1—Oc2 | 86.0 (2) | Ot11—Mo3—Oc3 | 92.4 (3) |
Ob4—Mo1—Oc2 | 71.8 (2) | Ob5—Mo3—Oc3 | 72.0 (2) |
Ot7—Mo1—Oc1 | 92.2 (3) | Ob6—Mo3—Oc3 | 83.8 (2) |
Ot8—Mo1—Oc1 | 161.7 (3) | Oc1i—Mo3—Oc3 | 74.6 (2) |
Ob6i—Mo1—Oc1 | 71.4 (2) | Ni—Oc1—Mo3i | 101.1 (2) |
Ob4—Mo1—Oc1 | 85.1 (2) | Ni—Oc1—Mo1 | 100.9 (2) |
Oc2—Mo1—Oc1 | 74.3 (2) | Mo3i—Oc1—Mo1 | 95.4 (2) |
Ot9—Mo2—Ot10 | 104.4 (3) | Ni—Oc2—Mo2 | 102.4 (2) |
Ot9—Mo2—Ob4 | 100.9 (3) | Ni—Oc2—Mo1 | 102.1 (2) |
Ot10—Mo2—Ob4 | 95.5 (3) | Mo2—Oc2—Mo1 | 96.4 (2) |
Ot9—Mo2—Ob5 | 95.9 (3) | Ni—Oc3—Mo2 | 101.1 (2) |
Ot10—Mo2—Ob5 | 101.9 (3) | Ni—Oc3—Mo3 | 100.9 (2) |
Ob4—Mo2—Ob5 | 152.0 (2) | Mo2—Oc3—Mo3 | 95.1 (2) |
Ot9—Mo2—Oc2 | 93.0 (3) | Mo2—Ob4—Mo1 | 116.3 (3) |
Ot10—Mo2—Oc2 | 160.5 (3) | Mo3—Ob5—Mo2 | 117.8 (3) |
Ob4—Mo2—Oc2 | 72.2 (2) | Mo1i—Ob6—Mo3 | 118.1 (3) |
Symmetry code: (i) −x, −y+1, −z+1. |
Hydrogen-bond geometry (Å) top
D—H···A | D···A |
Oc1···Ot8ii | 2.844 (8) |
Oc3···Ot9ii | 2.908 (8) |
Ow1···Oc2i | 2.726 (8) |
Ow1···Ob4iii | 2.774 (9) |
Ow2···Ot12 | 2.86 (1) |
Ow2···Ot11iv | 2.90 (1) |
Ow2···N1v | 2.90 (2) |
Ow2···N1iv | 2.92 (1) |
N1···Ob6 | 2.69 (1) |
N1···Ot7iii | 2.86 (1) |
N1···Ow2vi | 2.90 (2) |
N1···Ow2vii | 2.92 (2) |
N2···Ob5 | 2.71 (1) |
N2···Ot10viii | 2.87 (1) |
N2···Ot7ix | 2.91 (1) |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) x+1/2, −y+3/2, z; (iii) −x+1/2, y−1/2, −z+1; (iv) −x+1/2, y−1/2, −z+2; (v) x−1/2, −y+1/2, z; (vi) x+1/2, −y+1/2, z; (vii) −x+1/2, y+1/2, −z+2; (viii) x−1/2, −y+3/2, z; (ix) −x−1/2, y−1/2, −z+1. |
Experimental details
Crystal data |
Chemical formula | (NH4)4[H6NiMo6O24]·4H2O |
Mr | 1168.63 |
Crystal system, space group | Monoclinic, P21/a |
Temperature (K) | 298 |
a, b, c (Å) | 11.994 (3), 11.131 (2), 11.384 (9) |
β (°) | 109.31 (8) |
V (Å3) | 1434.3 (12) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 3.29 |
Crystal size (mm) | 0.25 × 0.19 × 0.10 |
|
Data collection |
Diffractometer | Stoe STADI4 diffractometer |
Absorption correction | Numerical (X-SHAPE; Stoe & Cie, 1996) |
Tmin, Tmax | 0.542, 0.849 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3290, 3290, 2448 |
Rint | 0.000 |
(sin θ/λ)max (Å−1) | 0.651 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.053, 0.137, 1.13 |
No. of reflections | 3290 |
No. of parameters | 178 |
H-atom treatment | H-atom parameters not refined |
| w = 1/[σ2(Fo2) + (0.0508P)2 + 13.3268P] where P = (Fo2 + 2Fc2)/3 |
Δρmax, Δρmin (e Å−3) | 1.11, −1.33 |
Selected bond lengths (Å) topNi—Oc2 | 2.046 (5) | Mo2—Ob4 | 1.946 (6) |
Ni—Oc3 | 2.047 (6) | Mo2—Ob5 | 1.952 (6) |
Ni—Oc1 | 2.052 (6) | Mo2—Oc2 | 2.216 (6) |
Mo1—Ot7 | 1.712 (7) | Mo2—Oc3 | 2.252 (5) |
Mo1—Ot8 | 1.720 (6) | Mo3—Ot12 | 1.708 (7) |
Mo1—Ob6i | 1.935 (6) | Mo3—Ot11 | 1.718 (7) |
Mo1—Ob4 | 1.954 (7) | Mo3—Ob5 | 1.932 (6) |
Mo1—Oc2 | 2.228 (6) | Mo3—Ob6 | 1.949 (6) |
Mo1—Oc1 | 2.258 (5) | Mo3—Oc1i | 2.245 (6) |
Mo2—Ot9 | 1.701 (6) | Mo3—Oc3 | 2.254 (6) |
Mo2—Ot10 | 1.717 (7) | | |
Symmetry code: (i) −x, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D···A |
Oc1···Ot8ii | 2.844 (8) |
Oc3···Ot9ii | 2.908 (8) |
Ow1···Oc2i | 2.726 (8) |
Ow1···Ob4iii | 2.774 (9) |
Ow2···Ot12 | 2.86 (1) |
Ow2···Ot11iv | 2.90 (1) |
Ow2···N1v | 2.90 (2) |
Ow2···N1iv | 2.92 (1) |
N1···Ob6 | 2.69 (1) |
N1···Ot7iii | 2.86 (1) |
N1···Ow2vi | 2.90 (2) |
N1···Ow2vii | 2.92 (2) |
N2···Ob5 | 2.71 (1) |
N2···Ot10viii | 2.87 (1) |
N2···Ot7ix | 2.91 (1) |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) x+1/2, −y+3/2, z; (iii) −x+1/2, y−1/2, −z+1; (iv) −x+1/2, y−1/2, −z+2; (v) x−1/2, −y+1/2, z; (vi) x+1/2, −y+1/2, z; (vii) −x+1/2, y+1/2, −z+2; (viii) x−1/2, −y+3/2, z; (ix) −x−1/2, y−1/2, −z+1. |
The B-type Anderson-Evans structure heteropolyoxoanions, [H6Xn-Mo6O24](6-n)- (X: Co2+, Co3+, Ni2+, Fe3+) (Anderson, 1937; Tsigdinos, 1978) do not usually form crystals suitable for structure determination. The reason is that the effective packing is disturbed by six undissociated H atoms bound to O atoms in XO6. As a result, they form a plate-like powder. But, the simple crystals suitable for the structure determination, such as K3[H6CoMo6O24].14H2O, were obtained by careful recrystallization. The title crystals were also obtained by recrystallization, as reported in the early part of last century (Hall, 1907) However, an X-ray study has not been reported. Fig. 1 shows the structure of the [H6Ni6Mo6O24]4- polyanion. The anion has an inversion center and is close to having D3 d (3 m) symmetry. All atoms, except for the central NiII atom, are located on the general position of the space group. The Ni atom lies on the inversion center of the polyanion. The labelling of the O atoms in the polyanion is the same as in the previous report (Lee & Joo, 2000). Six non-acidic H atoms in the [H6NiMo6O24]4- polyanion are bound to six central Oc atoms surrounding the NiII atom, as they are in the Anderson–Evans structure heteropolyoxoanions containing Cu2+ (Ito et al., 1989), Al3+ (Lee et al., 1991), Co3+ (Nolan et al., 1998; Lee et al., 2001), Cr3+ (Perloff, 1970) and Rh3+ (Ozawa et al., 1991). The average X—O distances (and ionic radii: Shannon, 1976) in the [H6Xn+Mo6O24](8-n)- polyanion are 1.90 (Al3+, 67.5 pm), 1.906 (Co3+, 68.5 pm), 1.975 (Cr3+, 75.5 pm), 2.021 (Rh3+, 80.5 pm), 2.06 (Cu2+, 87 pm) and 2.049 (Ni2+, 83 pm)Å. These values showed that the distances increased according to ionic radii, respectively. The Mo—Ob and the Mo—Ot distances were not affected by the characters of heteroatoms.
Water molecules and ammonium ions were distinguished from the hydrogen bonding and interatomic distances. Two ammonium ions cannot be nearer to each other than 3.7 Å (Siemons & Templeton 1954). In the first instance, the Ow1 and N1 atoms are decided by these results.
The packing diagram of a unit cell is shown in Fig. 2. A list of all hydrogen-bond distances within 2.95 Å is given in Table 2. The H atom of Oc2 does not contribute to the inter-anion hydrogen bonding, but it forms a strong hydrogen bond with Ow1. All water molecules and ammonium ions contribute to hydrogen bonding with each other or with the O atoms in the polyanion. Except for the two direct inter-anion hydrogen bonds, Oc1—Ot8 and Oc3—Ot9, the other hydrogen bonds between the anions occur indirectly through H2O or NH4. The title crystals were stabilized by the this hydrogen bonding.