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Acta Crystallogr Sect E Struct Rep Online. 2010 May 1; 66(Pt 5): m539–m540.
Published online 2010 April 21. doi:  10.1107/S1600536810013449
PMCID: PMC2979215

μ-η22-Peroxido-bis­[nitratodioxido­bis(pyrrolidin-2-one)uranium(VI)]

Abstract

In the crystal structure of the title compound, [U2(NO3)2O4(O2)(C4H7NO)4], two UO2 2+ ions are connected by a μ-η22-O2 unit. The O2 unit shows ‘side-on’ coordination to both U atoms. An inversion center is located at the midpoint of the O—O bond in the O2 unit, affording a centrosymmetrically expanded dimeric structure. The U—O(axial) bond lengths are 1.777 (4) Å and 1.784 (4) Å, indicating that the oxidation state of U is exclusively 6+, i.e., UO2 2+. Furthermore, the O—O distance is 1.492 (8) Å, which is typical of peroxide, O2 2–. The U atom is eight-coordinated in a hexa­gonal-bipyramidal geometry. The coordinating atoms of the nitrate and pyrrolidine-2-one ligands and the μ-η22-O2 2– unit are located in the equatorial plane and form an irregular hexa­gon. An inter­molecular hydrogen bond is found between N—H of the pyrrolidine-2-one ligand and the coordinating O of the same ligand in a neighboring complex. A second inter­molecular hydrogen bond is found between the N—H of the other pyrrolidine-2-one ligand and one of the uranyl oxido atoms.

Related literature

For the structural chemistry of uran­yl(VI)–peroxido complexes, see: Haegele & Boeyens (1977 [triangle]); Charpin et al. (1985 [triangle]); Doyle et al. (1993 [triangle]); Rose et al. (1994 [triangle]); Thuéry et al. (1999 [triangle]); de Aquino et al. (2001 [triangle]); John et al. (2004 [triangle]); Masci & Thuéry (2005 [triangle]); Zehnder et al. (2005 [triangle]); Kubatko et al. (2007 [triangle]); Ikeda et al. (2007 [triangle]); Takao et al. (2009 [triangle]); Vaska (1976 [triangle]).

An external file that holds a picture, illustration, etc.
Object name is e-66-0m539-scheme1.jpg

Experimental

Crystal data

  • [U2(NO3)2O4(O2)(C4H7NO)4]
  • M r = 1036.50
  • Triclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-0m539-efi1.jpg
  • a = 8.783 (2) Å
  • b = 8.899 (3) Å
  • c = 9.587 (3) Å
  • α = 68.24 (3)°
  • β = 81.30 (2)°
  • γ = 68.96 (2)°
  • V = 649.4 (3) Å3
  • Z = 1
  • Mo Kα radiation
  • μ = 12.54 mm−1
  • T = 173 K
  • 0.30 × 0.20 × 0.20 mm

Data collection

  • Rigaku R-AXIS RAPID diffractometer
  • Absorption correction: numerical (NUMABS; Higashi, 1999 [triangle]) T min = 0.117, T max = 0.188
  • 5524 measured reflections
  • 2934 independent reflections
  • 2727 reflections with I > 2σ(I)
  • R int = 0.037

Refinement

  • R[F 2 > 2σ(F 2)] = 0.026
  • wR(F 2) = 0.064
  • S = 1.00
  • 2934 reflections
  • 181 parameters
  • H-atom parameters constrained
  • Δρmax = 2.04 e Å−3
  • Δρmin = −0.97 e Å−3

Data collection: PROCESS-AUTO (Rigaku/MSC, 2006 [triangle]); cell refinement: PROCESS-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2006 [triangle]); program(s) used to solve structure: DIRDIF99 (Beurskens et al., 1999 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: ORTEP-3 (Farrugia, 1997 [triangle]); software used to prepare material for publication: CrystalStructure.

Table 1
Selected geometric parameters (Å, °)
Table 2
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810013449/om2328sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810013449/om2328Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

KT thanks Professor Dr Bernhard (FZD) for the opportunity to work there and to prepare this paper.

supplementary crystallographic information

Comment

The molecular structure of the title compound is shown in Fig. 1. The uranium atom is surrounded by eight O atoms; two are at the axial position, as part of the uranyl cation, and the remaining six O from pyrrolidine-2-ones, nitrates, and peroxo which form a distorted-hexagonal equatorial plane. The peroxide unit shows "side-on" coordination and connects two U, i.e., µ-η22-O2. The bond lengths between U and the axial O are 1.78 Å (mean), indicating that oxidation state of U is exclusively 6+, i.e., UO22+ (see related literature; cf. 1.84-1.91 Å for UVO2+, Ikeda et al., 2007, Takao et al., 2009). Furthermore, the O—O distance is 1.492 (8) Å, which is typical of peroxide, O22– (Vaska, 1976). One intermolecular hydrogen bonds is found between N—H of pyrrolidine-2-one and the coordinating O of the same ligand in the neighboring complex. A second intermolecular hydrogen bond is found between the N—H of the other pyrrolidine-2-one and one of the uranyl oxo atoms, see Fig. 2.

Photochemically excited *UO22+ is a potent and long-lived oxidant for organic and inorganic substrates including the solvent. After the oxidation, UO2+ is generated as a short-lived intermediate. This species is very unstable and immediately oxidized by dioxygen molecule. As a result, the initial UO22+ is regenerated, and the photo-induced catalytic cycle is repeated until termination of photo irradiation or complete conversion of the substrate. This reaction affords peroxide as a by-product. As described in Experimental, compound 1 was unexpectedly obtained from an ethanolic solution dissolving UO2(NO3)26H2O and pyrrolidine-2-one under sunlight. The peroxo ligand most likely arose from oxidative addition of atmospheric dioxygen molecule to the UO2+ intermediate through the above-mentioned catalytic oxidation of ethanol by the photo-excited *UO22+. A similar reaction was speculated in some of the former studies which also described incidental deposition of the uranyl-peroxo complexes [Charpin et al. (1985); Doyle et al. (1993); John et al. (2004)].

Experimental

Pyrrolidine-2-one (2-pyrr, 0.11 g) was added dropwise into a hot ethanol solution (5 ml) dissolving uranyl(VI) nitrate hexahydrate (0.32 g) with vigorous stirring. After stirring for several minutes, the mixture was cooled to room temperature. Yellow crystals of UO2(NO3)2(2-pyrr)2 were removed by filtration. The supernatant was stored under the sunlight. After several days, orange platelet crystals of {[UO2NO3(C4H7NO)2]2O2} subsequently deposited, which were suitable for the X-ray diffraction experiment.

Refinement

All hydrogen atoms were geometrically positioned (C—H 0.99 Å, N—H 0.88 Å) and refined as riding on their parent atoms, with Uiso(H) = 1.2 Ueq(C,N).

Figures

Fig. 1.
A drawing of µ-η2:η2-peroxo-bis[nitratobis(pyrrolidine-2-one)dioxouranium(VI)] (1) showing 50% probability displacement ellipsoids. Symmetry code: (i) -x, -y+1, -z.
Fig. 2.
Intermolecular hydrogen bonds. Symmetry codes: (i) -x, -y+1, -z; (ii) -x+1, -y+1, -z; (iii) x+1, y, z; (iv) -x+1, -y+1, -z+1; (v) x+1, y, z+1.

Crystal data

[U2(NO3)2O4(O2)(C4H7NO)4]Z = 1
Mr = 1036.50F(000) = 478
Triclinic, P1Dx = 2.650 Mg m3
a = 8.783 (2) ÅMo Kα radiation, λ = 0.71073 Å
b = 8.899 (3) ÅCell parameters from 6275 reflections
c = 9.587 (3) Åθ = 3.1–27.5°
α = 68.24 (3)°µ = 12.54 mm1
β = 81.30 (2)°T = 173 K
γ = 68.96 (2)°Platelet, orange
V = 649.4 (3) Å30.30 × 0.20 × 0.20 mm

Data collection

Rigaku R-AXIS RAPID diffractometer2934 independent reflections
Radiation source: fine-focus sealed tube2727 reflections with I > 2σ(I)
graphiteRint = 0.037
Detector resolution: 10.00 pixels mm-1θmax = 27.5°, θmin = 3.1°
ω scansh = −11→11
Absorption correction: numerical (NUMABS; Higashi, 1999)k = −11→11
Tmin = 0.117, Tmax = 0.188l = −12→12
5524 measured reflections

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.026Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.064H-atom parameters constrained
S = 1.00w = 1/[σ2(Fo2) + (0.0387P)2 + 2.5299P] where P = (Fo2 + 2Fc2)/3
2934 reflections(Δ/σ)max < 0.001
181 parametersΔρmax = 2.04 e Å3
0 restraintsΔρmin = −0.97 e Å3

Special details

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2)

xyzUiso*/Ueq
U10.21945 (2)0.38333 (2)0.134424 (19)0.01484 (7)
O10.1573 (5)0.2025 (6)0.2384 (5)0.0283 (9)
O20.2956 (6)0.5569 (5)0.0387 (5)0.0290 (9)
O3−0.0454 (5)0.5419 (7)0.0555 (5)0.0427 (13)
O40.0681 (4)0.5317 (5)0.3068 (4)0.0184 (7)
O50.3773 (5)0.2945 (5)0.3554 (4)0.0233 (8)
O60.5044 (5)0.1836 (5)0.1196 (4)0.0253 (8)
O70.3597 (5)0.2765 (6)−0.0771 (5)0.0274 (9)
O80.6150 (5)0.1159 (6)−0.0778 (5)0.0320 (10)
N1−0.1016 (6)0.7323 (6)0.4011 (5)0.0219 (9)
H1−0.11090.65870.49080.026*
N20.6174 (6)0.3525 (6)0.3046 (6)0.0252 (10)
H20.60930.39510.20620.030*
N30.4985 (6)0.1888 (6)−0.0142 (5)0.0220 (9)
C1−0.0129 (6)0.6859 (6)0.2925 (6)0.0162 (9)
C2−0.0222 (7)0.8410 (7)0.1547 (6)0.0232 (11)
H2A−0.08990.84780.07740.028*
H2B0.08790.83900.11140.028*
C3−0.1017 (7)0.9916 (7)0.2126 (6)0.0220 (11)
H3A−0.01841.03450.22840.026*
H3B−0.18251.08690.14080.026*
C4−0.1845 (8)0.9175 (7)0.3610 (7)0.0289 (13)
H4A−0.16880.95930.43840.035*
H4B−0.30280.94770.34840.035*
C50.5058 (6)0.2954 (7)0.3950 (6)0.0183 (10)
C60.5538 (7)0.2302 (9)0.5552 (7)0.0285 (12)
H6A0.57540.10510.60040.034*
H6B0.46710.28820.61500.034*
C70.7558 (8)0.3392 (9)0.3818 (8)0.0336 (14)
H7A0.77000.45240.35360.040*
H7B0.85800.25790.35740.040*
C80.7105 (8)0.2736 (9)0.5478 (7)0.0314 (13)
H8A0.69060.36260.59330.038*
H8B0.79930.17030.60250.038*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
U10.01539 (10)0.01631 (10)0.01212 (10)−0.00364 (7)−0.00246 (6)−0.00480 (7)
O10.026 (2)0.029 (2)0.036 (2)−0.0151 (17)0.0063 (17)−0.0150 (19)
O20.039 (2)0.024 (2)0.023 (2)−0.0135 (18)0.0088 (17)−0.0083 (17)
O30.030 (2)0.058 (3)0.033 (2)0.019 (2)−0.0158 (19)−0.035 (3)
O40.0237 (18)0.0151 (17)0.0135 (16)−0.0020 (14)−0.0020 (14)−0.0053 (14)
O50.0199 (18)0.034 (2)0.0158 (18)−0.0079 (16)−0.0062 (14)−0.0077 (16)
O60.0233 (19)0.030 (2)0.0205 (19)−0.0036 (16)−0.0038 (15)−0.0099 (17)
O70.026 (2)0.030 (2)0.0210 (19)0.0021 (16)−0.0052 (16)−0.0117 (17)
O80.024 (2)0.034 (2)0.034 (2)−0.0005 (17)0.0046 (17)−0.019 (2)
N10.031 (2)0.012 (2)0.018 (2)−0.0049 (17)0.0034 (18)−0.0043 (17)
N20.028 (2)0.027 (2)0.020 (2)−0.011 (2)−0.0015 (19)−0.006 (2)
N30.024 (2)0.022 (2)0.021 (2)−0.0057 (18)−0.0002 (18)−0.0099 (19)
C10.019 (2)0.016 (2)0.015 (2)−0.0066 (18)−0.0017 (18)−0.0056 (19)
C20.035 (3)0.017 (2)0.015 (2)−0.009 (2)0.001 (2)−0.002 (2)
C30.022 (2)0.019 (3)0.021 (3)−0.006 (2)−0.001 (2)−0.002 (2)
C40.036 (3)0.017 (3)0.025 (3)−0.002 (2)0.007 (2)−0.006 (2)
C50.021 (2)0.015 (2)0.015 (2)−0.0003 (18)−0.0060 (19)−0.0050 (19)
C60.027 (3)0.043 (4)0.020 (3)−0.015 (3)−0.005 (2)−0.011 (3)
C70.027 (3)0.039 (4)0.042 (4)−0.016 (3)0.001 (3)−0.018 (3)
C80.029 (3)0.041 (4)0.030 (3)−0.013 (3)−0.007 (2)−0.015 (3)

Geometric parameters (Å, °)

U1—O11.777 (4)N2—C71.464 (8)
U1—O21.784 (4)N2—H20.8800
U1—O3i2.303 (4)C1—C21.503 (7)
U1—O32.315 (4)C2—C31.534 (8)
U1—O52.428 (4)C2—H2A0.9900
U1—O42.436 (4)C2—H2B0.9900
U1—O62.515 (4)C3—C41.524 (8)
U1—O72.523 (4)C3—H3A0.9900
U1—N32.960 (5)C3—H3B0.9900
O3—O3i1.492 (8)C4—H4A0.9900
O3—U1i2.303 (4)C4—H4B0.9900
O4—C11.264 (6)C5—C61.494 (7)
O5—C51.247 (6)C6—C81.543 (8)
O6—N31.275 (6)C6—H6A0.9900
O7—N31.284 (6)C6—H6B0.9900
O8—N31.211 (6)C7—C81.523 (9)
N1—C11.305 (7)C7—H7A0.9900
N1—C41.465 (7)C7—H7B0.9900
N1—H10.8800C8—H8A0.9900
N2—C51.321 (7)C8—H8B0.9900
O1—U1—O2175.6 (2)O8—N3—O6122.6 (5)
O1—U1—O3i90.6 (2)O8—N3—O7122.2 (5)
O2—U1—O3i93.5 (2)O6—N3—O7115.2 (4)
O1—U1—O390.0 (2)O8—N3—U1176.9 (4)
O2—U1—O394.2 (2)O6—N3—U157.5 (2)
O3i—U1—O337.70 (19)O7—N3—U157.9 (2)
O1—U1—O583.92 (18)O4—C1—N1123.2 (5)
O2—U1—O592.05 (18)O4—C1—C2126.9 (5)
O3i—U1—O5173.10 (16)N1—C1—C2109.9 (4)
O3—U1—O5137.69 (14)C1—C2—C3103.7 (4)
O1—U1—O491.03 (16)C1—C2—H2A111.0
O2—U1—O489.17 (16)C3—C2—H2A111.0
O3i—U1—O4106.98 (13)C1—C2—H2B111.0
O3—U1—O469.31 (13)C3—C2—H2B111.0
O5—U1—O468.98 (13)H2A—C2—H2B109.0
O1—U1—O689.08 (17)C4—C3—C2104.6 (4)
O2—U1—O687.70 (18)C4—C3—H3A110.8
O3i—U1—O6117.42 (13)C2—C3—H3A110.8
O3—U1—O6155.09 (14)C4—C3—H3B110.8
O5—U1—O666.88 (13)C2—C3—H3B110.8
O4—U1—O6135.59 (13)H3A—C3—H3B108.9
O1—U1—O796.11 (18)N1—C4—C3103.3 (4)
O2—U1—O784.17 (17)N1—C4—H4A111.1
O3i—U1—O767.09 (14)C3—C4—H4A111.1
O3—U1—O7104.63 (14)N1—C4—H4B111.1
O5—U1—O7117.64 (13)C3—C4—H4B111.1
O4—U1—O7170.69 (12)H4A—C4—H4B109.1
O6—U1—O750.79 (13)O5—C5—N2125.9 (5)
O1—U1—N393.83 (17)O5—C5—C6123.6 (5)
O2—U1—N384.52 (17)N2—C5—C6110.5 (5)
O3i—U1—N392.51 (14)C5—C6—C8104.3 (5)
O3—U1—N3130.14 (14)C5—C6—H6A110.9
O5—U1—N392.10 (13)C8—C6—H6A110.9
O4—U1—N3159.86 (13)C5—C6—H6B110.9
O6—U1—N325.29 (13)C8—C6—H6B110.9
O7—U1—N325.54 (13)H6A—C6—H6B108.9
O3i—O3—U1i71.6 (3)N2—C7—C8104.1 (5)
O3i—O3—U170.7 (3)N2—C7—H7A110.9
U1i—O3—U1142.30 (19)C8—C7—H7A110.9
C1—O4—U1134.6 (3)N2—C7—H7B110.9
C5—O5—U1141.9 (4)C8—C7—H7B110.9
N3—O6—U197.2 (3)H7A—C7—H7B109.0
N3—O7—U196.6 (3)C7—C8—C6106.1 (5)
C1—N1—C4114.3 (5)C7—C8—H8A110.5
C1—N1—H1122.9C6—C8—H8A110.5
C4—N1—H1122.9C7—C8—H8B110.5
C5—N2—C7114.4 (5)C6—C8—H8B110.5
C5—N2—H2122.8H8A—C8—H8B108.7
C7—N2—H2122.8
O1—U1—O3—O3i−91.0 (5)U1—O6—N3—O8176.3 (5)
O2—U1—O3—O3i90.3 (5)U1—O6—N3—O7−3.9 (5)
O5—U1—O3—O3i−172.0 (3)U1—O7—N3—O8−176.3 (5)
O4—U1—O3—O3i177.9 (5)U1—O7—N3—O63.9 (5)
O6—U1—O3—O3i−3.2 (8)O1—U1—N3—O8−173 (7)
O7—U1—O3—O3i5.3 (5)O2—U1—N3—O83(7)
N3—U1—O3—O3i4.0 (6)O3i—U1—N3—O896 (7)
O1—U1—O3—U1i−91.0 (5)O3—U1—N3—O894 (7)
O2—U1—O3—U1i90.3 (5)O5—U1—N3—O8−89 (7)
O3i—U1—O3—U1i0.000 (2)O4—U1—N3—O8−69 (7)
O5—U1—O3—U1i−172.0 (3)O6—U1—N3—O8−93 (7)
O4—U1—O3—U1i177.9 (5)O7—U1—N3—O891 (7)
O6—U1—O3—U1i−3.2 (8)O1—U1—N3—O6−79.7 (3)
O7—U1—O3—U1i5.3 (5)O2—U1—N3—O696.2 (3)
N3—U1—O3—U1i4.0 (6)O3i—U1—N3—O6−170.5 (3)
O1—U1—O4—C1−144.0 (5)O3—U1—N3—O6−172.9 (3)
O2—U1—O4—C140.4 (5)O5—U1—N3—O64.4 (3)
O3i—U1—O4—C1−53.0 (5)O4—U1—N3—O623.9 (6)
O3—U1—O4—C1−54.3 (5)O7—U1—N3—O6−175.8 (5)
O5—U1—O4—C1132.9 (5)O1—U1—N3—O796.2 (3)
O6—U1—O4—C1126.3 (4)O2—U1—N3—O7−87.9 (3)
O7—U1—O4—C1−3.8 (11)O3i—U1—N3—O75.3 (4)
N3—U1—O4—C1111.9 (5)O3—U1—N3—O72.9 (4)
O1—U1—O5—C5149.6 (6)O5—U1—N3—O7−179.8 (3)
O2—U1—O5—C5−28.6 (6)O4—U1—N3—O7−160.2 (3)
O3i—U1—O5—C5−172.1 (11)O6—U1—N3—O7175.8 (5)
O3—U1—O5—C5−127.0 (6)U1—O4—C1—N1171.1 (4)
O4—U1—O5—C5−116.9 (6)U1—O4—C1—C2−9.6 (8)
O6—U1—O5—C558.0 (6)C4—N1—C1—O4179.5 (5)
O7—U1—O5—C555.9 (6)C4—N1—C1—C20.2 (7)
N3—U1—O5—C556.0 (6)O4—C1—C2—C3−166.8 (5)
O1—U1—O6—N3101.0 (3)N1—C1—C2—C312.5 (6)
O2—U1—O6—N3−82.0 (3)C1—C2—C3—C4−19.4 (6)
O3i—U1—O6—N310.7 (4)C1—N1—C4—C3−12.8 (7)
O3—U1—O6—N312.9 (6)C2—C3—C4—N119.4 (6)
O5—U1—O6—N3−175.2 (3)U1—O5—C5—N2−3.6 (9)
O4—U1—O6—N3−168.5 (3)U1—O5—C5—C6176.3 (4)
O7—U1—O6—N32.3 (3)C7—N2—C5—O5179.5 (5)
O1—U1—O7—N3−86.1 (3)C7—N2—C5—C6−0.4 (7)
O2—U1—O7—N389.5 (3)O5—C5—C6—C8−174.8 (5)
O3i—U1—O7—N3−174.2 (4)N2—C5—C6—C85.1 (7)
O3—U1—O7—N3−177.7 (3)C5—N2—C7—C8−4.6 (7)
O5—U1—O7—N30.2 (4)N2—C7—C8—C67.3 (7)
O4—U1—O7—N3134.0 (7)C5—C6—C8—C7−7.6 (7)
O6—U1—O7—N3−2.3 (3)

Symmetry codes: (i) −x, −y+1, −z.

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
N1—H1···O4ii0.882.032.885 (6)165
N2—H2···O2iii0.882.313.127 (7)156

Symmetry codes: (ii) −x, −y+1, −z+1; (iii) −x+1, −y+1, −z.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: OM2328).

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