metal-organic compounds
Aquadioxidobis(pentane-2,4-dionato)uranium(VI) pyrazine solvate
aDepartment of Chemistry, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan, and bResearch Center for Materials with Integrated Properties, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan
*Correspondence e-mail: kitazawa@chem.sci.toho-u.ac.jp
The 5H7O2)2O2(H2O)]·C4H4N2, contains one [UO2(acac)2(H2O)] (where acac is acetylacetonate) and two half-molecules of pyrazine. It exhibits a UO7 pentagonal-bipyramidal coordination geometry about the UVI atom, involving two bidentate acetylacetonate ions and one water molecule. The N atoms of the pyrazine molecules are not coordinated to the UVI atom, and are connected with the aqua O atom by hydrogen bonds. This results in a zigzag chain arrangement along the [10] direction.
of the title compound, [U(CRelated literature
For related structures, see: Alcock et al. (1984, 1987); Alcock & Flanders (1987); Borkowski & Cahill (2004); Huuskonen et al. (2007); Kannan et al. (2001); Takao & Ikeda (2008).
Experimental
Crystal data
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Refinement
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Data collection: SMART (Bruker, 2001); cell SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and CrystalMaker (CrystalMaker, 2007); software used to prepare material for publication: SHELXTL.
Supporting information
10.1107/S1600536808009021/hk2447sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536808009021/hk2447Isup2.hkl
To the acetonitrile solution (10 ml) containing UO2(NO3)2.6H2O (0.5 mmol) was added acetylacetone (3.0 mmol) and pyrazine (3.0 mmol) in acetonitrile (5 ml). After the solvent evaporated slowly at room temperature for a few days, orange crystals of (I) were obtained.
H atoms (for H2O) were located in difference syntheses and refined isotropically by applying restrains on O-H bonds [O-H = 0.852 (10) and 0.849 (10) Å; Uiso(H) = 0.062 (16) and 0.069 (18) Å2]. The remaining H atoms were positioned geometrically, with C-H = 0.93 Å (for CH) and 0.96 Å (for CH3) and constrained to ride on their parent atoms with Uiso(H) = xUeq(C), where x = 1.5 for CH3 H and x = 1.2 for CH H atoms.
Data collection: SMART (Bruker, 2001); cell
SAINT (Bruker, 2001); data reduction: SAINT (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008) and CrystalMaker (CrystalMaker, 2007); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).[U(C5H7O2)2O2(H2O)]·C4H4N2 | Z = 2 |
Mr = 566.35 | F(000) = 532 |
Triclinic, P1 | Dx = 2.027 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 8.186 (3) Å | Cell parameters from 2961 reflections |
b = 8.398 (3) Å | θ = 2.4–28.2° |
c = 13.663 (4) Å | µ = 8.78 mm−1 |
α = 88.162 (7)° | T = 299 K |
β = 82.111 (6)° | Plate, orange |
γ = 86.130 (6)° | 0.22 × 0.14 × 0.06 mm |
V = 928.0 (5) Å3 |
Bruker CCD area-detector diffractometer | 4526 independent reflections |
Radiation source: fine-focus sealed tube | 3841 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.024 |
Detector resolution: 8.366 pixels mm-1 | θmax = 28.3°, θmin = 1.5° |
ϕ and ω scans | h = −10→10 |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | k = −11→9 |
Tmin = 0.236, Tmax = 0.590 | l = −18→11 |
6928 measured reflections |
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)] = 0.031 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.078 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | w = 1/[σ2(Fo2) + (0.0402P)2 + 0.5065P] where P = (Fo2 + 2Fc2)/3 |
4526 reflections | (Δ/σ)max = 0.001 |
229 parameters | Δρmax = 1.63 e Å−3 |
2 restraints | Δρmin = −1.27 e Å−3 |
[U(C5H7O2)2O2(H2O)]·C4H4N2 | γ = 86.130 (6)° |
Mr = 566.35 | V = 928.0 (5) Å3 |
Triclinic, P1 | Z = 2 |
a = 8.186 (3) Å | Mo Kα radiation |
b = 8.398 (3) Å | µ = 8.78 mm−1 |
c = 13.663 (4) Å | T = 299 K |
α = 88.162 (7)° | 0.22 × 0.14 × 0.06 mm |
β = 82.111 (6)° |
Bruker CCD area-detector diffractometer | 4526 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 3841 reflections with I > 2σ(I) |
Tmin = 0.236, Tmax = 0.590 | Rint = 0.024 |
6928 measured reflections |
R[F2 > 2σ(F2)] = 0.031 | 2 restraints |
wR(F2) = 0.078 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 1.63 e Å−3 |
4526 reflections | Δρmin = −1.27 e Å−3 |
229 parameters |
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 > 2sigma(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 | ||
U1 | 0.259453 (17) | 0.495967 (19) | 0.247346 (9) | 0.03890 (8) | |
O1 | 0.3817 (5) | 0.4969 (5) | 0.1293 (3) | 0.0596 (10) | |
O2 | 0.1377 (5) | 0.4988 (5) | 0.3652 (3) | 0.0546 (9) | |
O3 | 0.0299 (5) | 0.5981 (5) | 0.1735 (3) | 0.0700 (11) | |
O4 | 0.1164 (4) | 0.2826 (4) | 0.2022 (3) | 0.0573 (9) | |
O5 | 0.4908 (5) | 0.5598 (5) | 0.3208 (3) | 0.0688 (11) | |
O6 | 0.4016 (4) | 0.2596 (4) | 0.2952 (2) | 0.0549 (8) | |
O7 | 0.2572 (4) | 0.7828 (4) | 0.2495 (2) | 0.0501 (8) | |
N1 | 0.4115 (6) | 0.9337 (6) | 0.0839 (3) | 0.0577 (12) | |
N2 | 0.0840 (6) | 0.9322 (6) | 0.4142 (3) | 0.0557 (11) | |
C1 | −0.2101 (7) | 0.6668 (8) | 0.0993 (5) | 0.0789 (19) | |
H1A | −0.2914 | 0.7004 | 0.1534 | 0.118* | |
H1B | −0.2637 | 0.6207 | 0.0497 | 0.118* | |
H1C | −0.1531 | 0.7573 | 0.0713 | 0.118* | |
C2 | −0.0877 (7) | 0.5442 (8) | 0.1361 (4) | 0.0565 (14) | |
C3 | −0.1090 (8) | 0.3840 (8) | 0.1297 (5) | 0.0764 (19) | |
H3 | −0.1992 | 0.3558 | 0.1010 | 0.092* | |
C4 | −0.0086 (6) | 0.2633 (7) | 0.1619 (4) | 0.0547 (12) | |
C5 | −0.0468 (9) | 0.0931 (8) | 0.1488 (6) | 0.088 (2) | |
H5A | 0.0435 | 0.0399 | 0.1075 | 0.133* | |
H5B | −0.1456 | 0.0915 | 0.1184 | 0.133* | |
H5C | −0.0625 | 0.0393 | 0.2121 | 0.133* | |
C6 | 0.7166 (7) | 0.5944 (8) | 0.4048 (4) | 0.0721 (17) | |
H6A | 0.8071 | 0.6143 | 0.3543 | 0.108* | |
H6B | 0.7580 | 0.5415 | 0.4605 | 0.108* | |
H6C | 0.6591 | 0.6939 | 0.4249 | 0.108* | |
C7 | 0.5996 (6) | 0.4899 (8) | 0.3648 (4) | 0.0541 (14) | |
C8 | 0.6166 (8) | 0.3245 (9) | 0.3785 (5) | 0.0744 (18) | |
H8 | 0.6979 | 0.2833 | 0.4152 | 0.089* | |
C9 | 0.5220 (6) | 0.2191 (7) | 0.3416 (4) | 0.0547 (12) | |
C10 | 0.5580 (9) | 0.0434 (8) | 0.3557 (5) | 0.086 (2) | |
H10A | 0.4673 | −0.0008 | 0.3974 | 0.128* | |
H10B | 0.6569 | 0.0252 | 0.3860 | 0.128* | |
H10C | 0.5730 | −0.0068 | 0.2927 | 0.128* | |
C11 | 0.4593 (7) | 0.8497 (7) | 0.0033 (4) | 0.0535 (13) | |
H11 | 0.4348 | 0.7432 | 0.0030 | 0.064* | |
C12 | 0.4551 (8) | 1.0829 (8) | 0.0803 (4) | 0.0614 (15) | |
H12 | 0.4272 | 1.1446 | 0.1362 | 0.074* | |
C13 | 0.0714 (7) | 1.0896 (7) | 0.4270 (4) | 0.0569 (14) | |
H13 | 0.1206 | 1.1556 | 0.3771 | 0.068* | |
C14 | 0.0118 (7) | 0.8421 (7) | 0.4888 (4) | 0.0527 (12) | |
H14 | 0.0181 | 0.7317 | 0.4833 | 0.063* | |
H22 | 0.202 (6) | 0.846 (5) | 0.291 (3) | 0.069 (18)* | |
H21 | 0.284 (6) | 0.845 (5) | 0.200 (3) | 0.062 (16)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
U1 | 0.04099 (10) | 0.04129 (13) | 0.03434 (9) | −0.00227 (7) | −0.00502 (6) | −0.00051 (7) |
O1 | 0.069 (2) | 0.061 (3) | 0.0440 (18) | −0.0096 (19) | 0.0121 (16) | −0.0057 (17) |
O2 | 0.058 (2) | 0.056 (2) | 0.0461 (17) | −0.0055 (18) | 0.0052 (15) | 0.0023 (17) |
O3 | 0.077 (3) | 0.050 (3) | 0.091 (3) | −0.004 (2) | −0.043 (2) | 0.007 (2) |
O4 | 0.060 (2) | 0.052 (2) | 0.064 (2) | −0.0073 (17) | −0.0236 (16) | 0.0040 (18) |
O5 | 0.058 (2) | 0.059 (3) | 0.097 (3) | −0.0040 (19) | −0.036 (2) | 0.000 (2) |
O6 | 0.0554 (19) | 0.053 (2) | 0.0590 (19) | 0.0022 (17) | −0.0185 (15) | −0.0024 (17) |
O7 | 0.058 (2) | 0.046 (2) | 0.0426 (17) | 0.0002 (17) | 0.0050 (15) | −0.0020 (16) |
N1 | 0.065 (3) | 0.054 (3) | 0.048 (2) | 0.004 (2) | 0.0087 (19) | 0.007 (2) |
N2 | 0.064 (3) | 0.050 (3) | 0.047 (2) | −0.004 (2) | 0.0117 (19) | −0.004 (2) |
C1 | 0.067 (4) | 0.082 (5) | 0.091 (4) | 0.008 (3) | −0.031 (3) | 0.015 (4) |
C2 | 0.050 (3) | 0.071 (4) | 0.049 (3) | 0.002 (3) | −0.016 (2) | 0.007 (3) |
C3 | 0.067 (4) | 0.067 (5) | 0.104 (5) | −0.012 (3) | −0.043 (3) | 0.009 (4) |
C4 | 0.055 (3) | 0.056 (3) | 0.056 (3) | −0.014 (2) | −0.013 (2) | 0.002 (2) |
C5 | 0.087 (4) | 0.060 (4) | 0.129 (6) | −0.018 (4) | −0.047 (4) | −0.003 (4) |
C6 | 0.052 (3) | 0.097 (5) | 0.072 (3) | −0.011 (3) | −0.020 (3) | −0.013 (3) |
C7 | 0.040 (2) | 0.080 (4) | 0.043 (2) | −0.002 (3) | −0.0084 (18) | −0.007 (3) |
C8 | 0.065 (3) | 0.073 (5) | 0.091 (4) | 0.008 (3) | −0.036 (3) | 0.004 (4) |
C9 | 0.044 (2) | 0.062 (4) | 0.056 (3) | 0.011 (2) | −0.006 (2) | 0.000 (2) |
C10 | 0.090 (5) | 0.065 (4) | 0.105 (5) | 0.016 (4) | −0.036 (4) | 0.001 (4) |
C11 | 0.067 (3) | 0.043 (3) | 0.048 (3) | 0.000 (2) | −0.002 (2) | −0.001 (2) |
C12 | 0.087 (4) | 0.055 (4) | 0.037 (2) | 0.005 (3) | 0.006 (2) | −0.007 (2) |
C13 | 0.064 (3) | 0.055 (4) | 0.048 (3) | −0.013 (3) | 0.008 (2) | 0.007 (2) |
C14 | 0.062 (3) | 0.039 (3) | 0.055 (3) | −0.004 (2) | 0.001 (2) | −0.001 (2) |
U1—O1 | 1.777 (3) | C4—C5 | 1.505 (8) |
U1—O2 | 1.774 (3) | C5—H5A | 0.9600 |
U1—O3 | 2.352 (4) | C5—H5B | 0.9600 |
U1—O4 | 2.348 (4) | C5—H5C | 0.9600 |
U1—O5 | 2.361 (4) | C6—C7 | 1.507 (8) |
U1—O6 | 2.353 (3) | C6—H6A | 0.9600 |
U1—O7 | 2.409 (4) | C6—H6B | 0.9600 |
O3—C2 | 1.265 (6) | C6—H6C | 0.9600 |
O4—C4 | 1.249 (6) | C7—C8 | 1.396 (9) |
O5—C7 | 1.246 (6) | C8—C9 | 1.366 (8) |
O6—C9 | 1.266 (6) | C8—H8 | 0.9300 |
O7—H21 | 0.86 (4) | C9—C10 | 1.496 (8) |
O7—H22 | 0.85 (4) | C10—H10A | 0.9600 |
N1—C11 | 1.326 (7) | C10—H10B | 0.9600 |
N1—C12 | 1.323 (8) | C10—H10C | 0.9600 |
N2—C13 | 1.334 (8) | C11—C12i | 1.381 (7) |
N2—C14 | 1.344 (6) | C11—H11 | 0.9300 |
C1—C2 | 1.511 (8) | C12—C11i | 1.381 (7) |
C1—H1A | 0.9600 | C12—H12 | 0.9300 |
C1—H1B | 0.9600 | C13—C14ii | 1.375 (8) |
C1—H1C | 0.9600 | C13—H13 | 0.9300 |
C2—C3 | 1.376 (9) | C14—C13ii | 1.375 (8) |
C3—C4 | 1.361 (8) | C14—H14 | 0.9300 |
C3—H3 | 0.9300 | ||
O1—U1—O2 | 178.98 (14) | O4—C4—C3 | 124.6 (5) |
O1—U1—O3 | 89.43 (18) | O4—C4—C5 | 116.1 (5) |
O1—U1—O4 | 90.62 (17) | C3—C4—C5 | 119.3 (5) |
O1—U1—O5 | 89.85 (18) | C4—C5—H5A | 109.5 |
O1—U1—O6 | 91.40 (17) | C4—C5—H5B | 109.5 |
O1—U1—O7 | 90.01 (16) | H5A—C5—H5B | 109.5 |
O2—U1—O3 | 90.37 (17) | C4—C5—H5C | 109.5 |
O2—U1—O4 | 90.26 (16) | H5A—C5—H5C | 109.5 |
O2—U1—O5 | 89.75 (17) | H5B—C5—H5C | 109.5 |
O2—U1—O6 | 89.35 (16) | C7—C6—H6A | 109.5 |
O2—U1—O7 | 88.97 (15) | C7—C6—H6B | 109.5 |
O3—U1—O4 | 70.89 (13) | H6A—C6—H6B | 109.5 |
O3—U1—O5 | 145.58 (15) | C7—C6—H6C | 109.5 |
O3—U1—O6 | 143.98 (14) | H6A—C6—H6C | 109.5 |
O3—U1—O7 | 72.72 (13) | H6B—C6—H6C | 109.5 |
O4—U1—O5 | 143.53 (13) | O5—C7—C8 | 123.7 (5) |
O4—U1—O6 | 73.10 (12) | O5—C7—C6 | 116.4 (6) |
O4—U1—O7 | 143.59 (13) | C8—C7—C6 | 119.9 (5) |
O5—U1—O6 | 70.43 (13) | C9—C8—C7 | 124.5 (5) |
O5—U1—O7 | 72.87 (13) | C9—C8—H8 | 117.7 |
O6—U1—O7 | 143.27 (13) | C7—C8—H8 | 117.7 |
C2—O3—U1 | 137.8 (4) | O6—C9—C8 | 124.2 (5) |
C4—O4—U1 | 137.9 (4) | O6—C9—C10 | 116.0 (5) |
C7—O5—U1 | 138.5 (4) | C8—C9—C10 | 119.9 (5) |
C9—O6—U1 | 138.2 (4) | C9—C10—H10A | 109.5 |
U1—O7—H22 | 129 (4) | C9—C10—H10B | 109.5 |
U1—O7—H21 | 127 (4) | H10A—C10—H10B | 109.5 |
H22—O7—H21 | 102 (5) | C9—C10—H10C | 109.5 |
C12—N1—C11 | 116.2 (4) | H10A—C10—H10C | 109.5 |
C13—N2—C14 | 116.4 (5) | H10B—C10—H10C | 109.5 |
C2—C1—H1A | 109.5 | N1—C11—C12i | 121.4 (5) |
C2—C1—H1B | 109.5 | N1—C11—H11 | 119.3 |
H1A—C1—H1B | 109.5 | C12i—C11—H11 | 119.3 |
C2—C1—H1C | 109.5 | N1—C12—C11i | 122.4 (5) |
H1A—C1—H1C | 109.5 | N1—C12—H12 | 118.8 |
H1B—C1—H1C | 109.5 | C11i—C12—H12 | 118.8 |
O3—C2—C3 | 123.5 (5) | N2—C13—C14ii | 122.5 (5) |
O3—C2—C1 | 116.3 (6) | N2—C13—H13 | 118.8 |
C3—C2—C1 | 120.2 (5) | C14ii—C13—H13 | 118.8 |
C4—C3—C2 | 125.3 (5) | N2—C14—C13ii | 121.1 (5) |
C4—C3—H3 | 117.3 | N2—C14—H14 | 119.5 |
C2—C3—H3 | 117.3 | C13ii—C14—H14 | 119.5 |
Symmetry codes: (i) −x+1, −y+2, −z; (ii) −x, −y+2, −z+1. |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H21···N1 | 0.86 (4) | 1.94 (2) | 2.752 (5) | 160 (5) |
O7—H22···N2 | 0.85 (4) | 1.96 (2) | 2.778 (6) | 161 (5) |
Experimental details
Crystal data | |
Chemical formula | [U(C5H7O2)2O2(H2O)]·C4H4N2 |
Mr | 566.35 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 299 |
a, b, c (Å) | 8.186 (3), 8.398 (3), 13.663 (4) |
α, β, γ (°) | 88.162 (7), 82.111 (6), 86.130 (6) |
V (Å3) | 928.0 (5) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 8.78 |
Crystal size (mm) | 0.22 × 0.14 × 0.06 |
Data collection | |
Diffractometer | Bruker CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.236, 0.590 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6928, 4526, 3841 |
Rint | 0.024 |
(sin θ/λ)max (Å−1) | 0.667 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.031, 0.078, 1.04 |
No. of reflections | 4526 |
No. of parameters | 229 |
No. of restraints | 2 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 1.63, −1.27 |
Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2001), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008) and CrystalMaker (CrystalMaker, 2007), SHELXTL (Sheldrick, 2008).
U1—O1 | 1.777 (3) | U1—O5 | 2.361 (4) |
U1—O2 | 1.774 (3) | U1—O6 | 2.353 (3) |
U1—O3 | 2.352 (4) | U1—O7 | 2.409 (4) |
U1—O4 | 2.348 (4) | ||
O1—U1—O2 | 178.98 (14) | O3—U1—O4 | 70.89 (13) |
O1—U1—O3 | 89.43 (18) | O3—U1—O5 | 145.58 (15) |
O1—U1—O4 | 90.62 (17) | O3—U1—O6 | 143.98 (14) |
O1—U1—O5 | 89.85 (18) | O3—U1—O7 | 72.72 (13) |
O1—U1—O6 | 91.40 (17) | O4—U1—O5 | 143.53 (13) |
O1—U1—O7 | 90.01 (16) | O4—U1—O6 | 73.10 (12) |
O2—U1—O3 | 90.37 (17) | O4—U1—O7 | 143.59 (13) |
O2—U1—O4 | 90.26 (16) | O5—U1—O6 | 70.43 (13) |
O2—U1—O5 | 89.75 (17) | O5—U1—O7 | 72.87 (13) |
O2—U1—O6 | 89.35 (16) | O6—U1—O7 | 143.27 (13) |
O2—U1—O7 | 88.97 (15) |
D—H···A | D—H | H···A | D···A | D—H···A |
O7—H21···N1 | 0.86 (4) | 1.94 (2) | 2.752 (5) | 160 (5) |
O7—H22···N2 | 0.85 (4) | 1.96 (2) | 2.778 (6) | 161 (5) |
References
Alcock, N. W. & Flanders, D. J. (1987). Acta Cryst. C43, 1480–1483. CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
Alcock, N. W., Flanders, D. J. & Brown, D. (1984). J. Chem. Soc. Dalton Trans. pp. 679–681. CSD CrossRef Web of Science Google Scholar
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Actinide chemistry has strong relationship with the reprocessing of nuclear fuels and treatment of actinide wastes in the backend chemistry for the nuclear power plants which operate everyday. The fundamental investigation of the bonding and structure of uranium complexes provides important information on the field of backend chemistry. Various uranyl(VI) complexes with β-diketonate have been reported; examples are [UO2(acac)2(H2O)] (Alcock, & Flanders, 1987), [UO2(acac)2(py)] (Alcock et al., 1984; Alcock et al., 1987), [UO2(tta)2(H2O)](H2O)2(dibenzo-18, crown-6) (Kannan et al., 2001), [UO2(acac)2(dmf)] (Huuskonen et al., 2007), and [UO2(dbm)2(EtOH)] (Takao & Ikeda, 2008). We report herein the synthesis and crystal structure of a new uranyl(VI) acetyl- acetonate complex of formula [UO2(acac)2(H2O)](pz) (I) (where acac is acetylacetonate and pz is pyrazine).
The asymmetric unit of the title compound, (I), (Fig. 1), contains one [UO2(acac)2(H2O)] and two-halves of pyrazine molecules. The coordination geometry of the U1 atom has a UO7 pentagonal-bipyramidal coordination; two uranyl oxygen atoms (O1 and O2) at the axial positions, and the remaining five O atoms from the two chelating acac ligands (O3, O4, O5 and O6) and one H2O molecule (O7) in the equatorial plane (Table 1). The O1—U1—O2 angle is 178.98 (14) °. The deviations of the O atoms of the acac and of the H2O from the equatorial plane (O3, O4, O5, O6 and O7) are within 0.02 Å. The U1—Oacac bond lengths are longer than the U1—Ouranyl distances and are shorter than the U1—Oaqua distance. The U1—O7 [2.409 (4) Å] bond is shorter than the UVI—Oaqua [2.489 (8) Å] bond of [UO2(acac)2(H2O)] (Alcock, & Flanders, 1987), but similar to the UVI—Oaqua [2.396 (5) Å] bond of {[UO2(C9H4O6)- (H2O)].H2O} (Borkowski & Cahill, 2004) and the UVI—Oaqua [2.419 (5) Å] bond of [UO2(tta)2(H2O)](H2O)2(dibenzo-18,crown-6) (Kannan et al., 2001).
The nitrogen atoms of the pyrazine molecules are not coordinated to the U1, and are connected with O7 atom of the H2O in the [UO2(acac)2(H2O)] molecule by the hydrogen bonds (Table 2). This results in a zigzag chain arrangement of along the [1 0 - 1] direction (Fig. 2). The dihedral angle between the two pyrazine rings is 13.9 (3)°.