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The structure of the title compound, which has been synthesized by evaporation at 294 K, consists of centrosymmetric uranyl hexagonal bipyramids that share opposite equatorial edges with two nitrate triangles, resulting in two distinct finite clusters of composition [(UO2)(H2O)2(NO3)2]. There are two unique symmetrically independent UVI positions and two unique nitrate groups.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102021108/ta1396sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270102021108/ta1396Isup2.hkl
Contains datablock I

Comment top

UO2(NO3)2(H2O)3 was first obtained as a by-product in a synthesis experiment intended to produce uranyl carbonates by room-temperature evaporation of a solution containing uranyl nitrate with various carbonates and nitrates. Subsequently, large single crystals of UO2(NO3)2(H2O)3 were obtained from a solution of UO2(NO3)(H2O)6, K2CO3 and Cu(NO3)2(H2O)3 at room temperature and pressure. The structures are known or estimated for the chemically related compounds (UO2)(NO3)2(H2O)2 (Taylor & Mueller, 1965), (UO2)(NO3)2(H2O)6 (Dalley et al., 1971) and (UO2)(NO3)2(H2O)3 (Vdovenko et al., 1963). Each contains the [(UO2)(H2O)2(NO3)2] finite cluster. These compounds crystallize in space groups Cmc21, P21/c and P1, respectively. Whereas (UO2)(NO3)2(H2O)2 and (UO2)(NO3)2(H2O)6 differ from UO2(NO3)2(H2O)3 in their hydration state and space group, the structure published by Vdovenko et al. (1963) corresponds to that for UO2(NO3)2(H2O)3. That published structure is incomplete, as only the U and O atoms were located. The refined structure, including N-atom positions, is given herein.

There are two symmetrically distinct UVI atoms, positioned on centers of symmetry, both of which are part of linear (UO2)2+ uranyl ions and which are coordinated by six equatorial atoms of O, forming hexagonal bipyramids (Fig. 1). Two opposite equatorial edges of each hexagonal bipyramid share edges with NO3 groups, giving the [(UO2)(H2O)2(NO3)2] cluster. Two H2O groups correspond to equatorial ligands of the uranyl polyhedra. One H2O group is located between the [(UO2)(H2O)2(NO3)2] clusters (Fig. 2).

Bond-valence sums were calculated for each ion using the method of Brese & O'Keeffe (1991). The U bond-valence sums (Burns at al., 1997) are 6.18 and 6.12 for the two unique U positions. The N bond-valence sums are 5.29 and 5.07. For O-atom positions O1, O3, O4, O5, O7, O8, O9 and O10, the bond-valence sums are within the normal range (1.80–2.07). For atoms O2, O6 and O11, values consistant with H2O were obtained (0.44, 0.46 and 0.00, respectively).

Experimental top

Transparent yellow crystals of UO2(NO3)2(H2O)3 up to 1 mm in maximum dimension were synthesized from a solution containing Cu(NO3)2(H2O)3, UO2(NO3)2(H2O)6 and K2CO3, in a molar ratio of 2:5:1, in solution in water (50 ml). Following evaporation in an open vessel for 14 d at 294 K and ambient pressure, crystals were recovered from the vessel walls.

Refinement top

The locations of the highest peak, 2.07 e Å−3, and deepest hole, −1.31 e Å−3, in the difference Fourier map are 0.79 Å from U2 and 0.86 Å from U1, respectively. H-atom positions were not included in the refinement.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SHELXTL-NT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1993); software used to prepare material for publication: Microsoft Word.

Figures top
[Figure 1] Fig. 1. Views of the two UO2(NO3)2 clusters in UO2(NO3)2(H2O)3, shown with 50% probability displacement ellipsoids.
[Figure 2] Fig. 2. The crystal structure of UO2(NO3)2(H2O)3 projected along [100]. Uranyl hexagonal bipyramids are shown in light grey, nitrate triangles in black and free H2O in dark grey.
Uranyl dinitrate trihydrate top
Crystal data top
UO2(NO3)2(H2O)3Z = 2
Mr = 448.08F(000) = 400
Triclinic, P1Dx = 3.31 Mg m3
a = 7.0359 (15) ÅMo Kα radiation, λ = 0.71073 Å
b = 7.1730 (15) ÅCell parameters from 3612 reflections
c = 10.084 (2) Åθ = 3–34.5°
α = 81.697 (4)°µ = 18.10 mm1
β = 82.041 (4)°T = 298 K
γ = 63.642 (4)°Block-like, yellow
V = 449.64 (16) Å30.12 × 0.11 × 0.10 mm
Data collection top
Make Model CCD area-detector
diffractometer
3614 independent reflections
Radiation source: fine-focus sealed tube2138 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.090
ω scansθmax = 34.5°, θmin = 2.1°
Absorption correction: empirical (using intensity measurements)
(SHELXL97; Sheldrick, 1997a)
h = 1011
Tmin = 0.098, Tmax = 0.164k = 1111
9093 measured reflectionsl = 1515
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)] = 0.043H-atom parameters not refined
wR(F2) = 0.109 w = 1/[σ2(Fo2) + (0.022P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
3614 reflectionsΔρmax = 2.08 e Å3
130 parametersΔρmin = 1.34 e Å3
0 restraints
Crystal data top
UO2(NO3)2(H2O)3γ = 63.642 (4)°
Mr = 448.08V = 449.64 (16) Å3
Triclinic, P1Z = 2
a = 7.0359 (15) ÅMo Kα radiation
b = 7.1730 (15) ŵ = 18.10 mm1
c = 10.084 (2) ÅT = 298 K
α = 81.697 (4)°0.12 × 0.11 × 0.10 mm
β = 82.041 (4)°
Data collection top
Make Model CCD area-detector
diffractometer
3614 independent reflections
Absorption correction: empirical (using intensity measurements)
(SHELXL97; Sheldrick, 1997a)
2138 reflections with I > 2σ(I)
Tmin = 0.098, Tmax = 0.164Rint = 0.090
9093 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0430 restraints
wR(F2) = 0.109H-atom parameters not refined
S = 1.01Δρmax = 2.08 e Å3
3614 reflectionsΔρmin = 1.34 e Å3
130 parameters
Special details top

Experimental. psi-scan absorption correction in XPREP

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
U10.50.50.50.02672 (13)
U20.50.00.00.02345 (13)
N10.7299 (13)0.7396 (12)0.5443 (8)0.0317 (17)
N20.1821 (12)0.3840 (11)0.1100 (7)0.0290 (16)
O10.6923 (11)0.2816 (10)0.5820 (7)0.0379 (16)
O20.2872 (11)0.5974 (10)0.7145 (6)0.0381 (16)
O30.7583 (12)0.6536 (11)0.4372 (7)0.0425 (18)
O40.5901 (12)0.7177 (12)0.6281 (7)0.0461 (19)
O50.3921 (10)0.0888 (9)0.1553 (6)0.0323 (15)
O60.2587 (11)0.1640 (11)0.0681 (7)0.0427 (18)
O70.1515 (10)0.2201 (10)0.1133 (7)0.0355 (15)
O80.3585 (10)0.3756 (9)0.0545 (6)0.0346 (15)
O90.8370 (13)0.8224 (12)0.5642 (8)0.053 (2)
O100.0494 (12)0.5377 (10)0.1591 (8)0.0455 (19)
O110.0687 (10)0.0235 (10)0.2683 (7)0.0347 (15)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
U10.0220 (3)0.0269 (3)0.0279 (3)0.0078 (2)0.0013 (2)0.0049 (2)
U20.0212 (3)0.0219 (2)0.0275 (3)0.0092 (2)0.0034 (2)0.0075 (2)
N10.023 (4)0.023 (4)0.020 (4)0.011 (3)0.002 (3)0.005 (3)
N20.021 (4)0.016 (3)0.021 (4)0.007 (3)0.007 (3)0.006 (3)
O10.027 (4)0.030 (3)0.048 (4)0.006 (3)0.008 (3)0.001 (3)
O20.039 (4)0.037 (4)0.034 (4)0.014 (3)0.011 (3)0.007 (3)
O30.039 (4)0.045 (4)0.045 (4)0.019 (4)0.005 (4)0.008 (4)
O40.041 (5)0.057 (5)0.046 (5)0.026 (4)0.014 (4)0.016 (4)
O50.037 (4)0.028 (3)0.027 (3)0.010 (3)0.006 (3)0.006 (3)
O60.041 (4)0.043 (4)0.052 (5)0.027 (4)0.015 (4)0.020 (4)
O70.029 (4)0.037 (4)0.043 (4)0.018 (3)0.008 (3)0.012 (3)
O80.031 (4)0.029 (3)0.047 (4)0.015 (3)0.007 (3)0.012 (3)
O90.056 (6)0.051 (5)0.066 (6)0.031 (5)0.001 (4)0.015 (4)
O100.042 (4)0.032 (4)0.054 (5)0.015 (3)0.019 (4)0.021 (3)
O110.030 (4)0.037 (4)0.035 (4)0.013 (3)0.002 (3)0.009 (3)
Geometric parameters (Å, º) top
U1—O11.738 (6)U2—O82.539 (6)
U1—O22.453 (6)N1—O91.198 (10)
U1—O32.485 (7)N1—O41.255 (10)
U1—O42.490 (7)N1—O31.269 (10)
U2—O51.745 (6)N2—O101.203 (9)
U2—O62.440 (7)N2—O81.269 (9)
U2—O72.473 (7)N2—O71.281 (9)
O1i—U1—O1180.0O5—U2—O789.8 (3)
O1—U1—O290.6 (3)O6—U2—O764.0 (2)
O2i—U1—O2180.0O7—U2—O7ii180.0
O1—U1—O390.4 (3)O5—U2—O889.7 (2)
O2—U1—O3114.6 (2)O6—U2—O8115.5 (2)
O3—U1—O3i180.0O7—U2—O851.4 (2)
O1—U1—O487.6 (3)O8—U2—O8ii180.0
O2—U1—O464.4 (2)O9—N1—O4124.4 (9)
O3—U1—O450.2 (2)O9—N1—O3121.9 (9)
O4—U1—O4i180.0O4—N1—O3113.6 (8)
O5—U2—O5ii180.0O10—N2—O8121.8 (8)
O5—U2—O689.9 (3)O10—N2—O7121.1 (8)
O6ii—U2—O6180.0O8—N2—O7117.1 (7)
Symmetry codes: (i) x+1, y+1, z+1; (ii) x+1, y, z.

Experimental details

Crystal data
Chemical formulaUO2(NO3)2(H2O)3
Mr448.08
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)7.0359 (15), 7.1730 (15), 10.084 (2)
α, β, γ (°)81.697 (4), 82.041 (4), 63.642 (4)
V3)449.64 (16)
Z2
Radiation typeMo Kα
µ (mm1)18.10
Crystal size (mm)0.12 × 0.11 × 0.10
Data collection
DiffractometerMake Model CCD area-detector
diffractometer
Absorption correctionEmpirical (using intensity measurements)
(SHELXL97; Sheldrick, 1997a)
Tmin, Tmax0.098, 0.164
No. of measured, independent and
observed [I > 2σ(I)] reflections
9093, 3614, 2138
Rint0.090
(sin θ/λ)max1)0.797
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.043, 0.109, 1.01
No. of reflections3614
No. of parameters130
H-atom treatmentH-atom parameters not refined
Δρmax, Δρmin (e Å3)2.08, 1.34

Computer programs: SMART (Bruker, 1998), SMART, SHELXTL-NT (Bruker, 1998), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), ATOMS (Dowty, 1993), Microsoft Word.

Selected bond lengths (Å) top
U1—O11.738 (6)U2—O51.745 (6)
U1—O22.453 (6)U2—O62.440 (7)
U1—O32.485 (7)U2—O72.473 (7)
U1—O42.490 (7)U2—O82.539 (6)
 

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