Dicaesium tetra­chlorido­dioxido­plutonate(VI)

Wilkerson, M.P.; Scott, B.L.

doi:10.1107/S1600536807066354

inorganic compounds

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Volume 64| Part 1| January 2008| Page i5

https://doi.org/10.1107/S1600536807066354

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Dicaesium tetrachloridodioxidoplutonate(VI)

Marianne P. Wilkerson ^a ^* and Brian L. Scott ^b

^aC-ADI, MS J565, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 USA, and ^bMPA-MC, MS J514, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 USA
^*Correspondence e-mail: mpw@lanl.gov

(Received 4 October 2007; accepted 10 December 2007; online 18 December 2007)

The anion of the title complex, Cs₂[PuCl₄O₂], adopts a pseudo-octahedral geometry (2/m crystallographic site symmetry) with two plutonyl oxide ligands in axial sites and four chloride ligands occupying the equatorial plane. Charge balance is maintained by two caesium cations per tetrachloridodioxidoplutonate(VI) anion. Principal bond lengths include Pu—O = 1.752 (3) Å and Pu—Cl = 2.6648 (8) Å.

Related literature

For related literature, see: Hall et al. (1966 ); Watkin et al. (1991 ); Wilkerson et al. (2004 ); Wilkerson et al. (2007 ); Bean et al. (2004 , 2005 ); Grenthe et al. (2006 ); Grigoriev et al. (2004 ); Runde et al. (2003 ); Sessler et al. (2002 ).

Experimental

Crystal data

Cs₂[PuCl₄O₂]
M_r = 678.67
Monoclinic, C 2/m
a = 11.9489 (7) Å
b = 7.7286 (5) Å
c = 5.7855 (4) Å
β = 96.439 (1)°
V = 530.91 (6) Å³
Z = 2
Mo Kα radiation
μ = 13.92 mm⁻¹
T = 141 (2) K
0.22 × 0.18 × 0.12 mm

Data collection

Bruker APEXII CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2001 ) T_min = 0.150, T_max = 0.286 (expected range = 0.099–0.188)
3212 measured reflections
711 independent reflections
659 reflections with I > 2σ(I)
R_int = 0.025

Refinement

R[F² > 2σ(F²)] = 0.015
wR(F²) = 0.037
S = 1.26
711 reflections
27 parameters
Δρ_max = 0.78 e Å⁻³
Δρ_min = −0.64 e Å⁻³

Data collection: APEX2 (Bruker, 2003 ); cell refinement: SAINT-Plus (Bruker, 2001 ); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000 ); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536807066354/fi2048sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536807066354/fi2048Isup2.hkl

checkCIF report

Comment top

The title compound, (1), is isostructural with the uranium analogue Cs2U(VI)O2Cl4 and the neptunium analogue Cs2Np(VI)O2Cl4, which crystallize in the space group C2/m (Hall et al., 1966; Watkin et al., 1991; Wilkerson et al., 2007). The Pu atom sits on a site of 2/m crystallographic symmetry; the twofold rotation axis bisects the Cl—U—Cl angle, and the plutonyl axis lies in the mirror plane. The plutonium metal is coordinated in a pseudo-octahedral fashion by two oxo groups and four chloride ligands. The oxo groups of the plutonyl ion lie trans to one another with a bond angle of 180.0 (3). This angle is equivalent within 3 σ to those reported for the limited number of plutonyl structures published (range 178.0 (4)–179.4 (2)) (Bean et al., 2004; Bean et al., 2005; Grigoriev et al., 2004; Runde et al., 2003). This value is within the range reported for the majority of actinyl compounds (Grenthe et al., 2006). The Pu—O(oxo) distances are 1.752 (3) Å. Although there are no reported six coordinate plutonyl structures with which to compare, this value is within range of Pu—O(oxo) bond lengths reported for seven coordinate plutonyl structures (1.727 (4)–1.771 (11) Å) (Bean et al., 2004; Bean et al., 2005; Grigoriev et al., 2004; Runde et al., 2003). The chloride ligands lie in the equatorial plane of the plutonyl ion, and the Pu—Cl bond distances are 2.6648 (8) Å. Although there are no plutonyl chloride structures reported, these values are longer than Np—Cl bond lengths reported for six-coordinate Cs₂NpO₂Cl₄ (2.653 (3) Å) (Wilkerson et al., 2004).

Related literature top

For related literature, see: Hall et al. (1966); Watkin et al. (1991); Wilkerson et al. (2004); Wilkerson et al. (2007); Bean et al. (2004, 2005); Grenthe et al. (2006); Grigoriev et al. (2004); Runde et al. (2003); Sessler et al. (2002).

Experimental top

Caesium chloride (0.021 g, 0.12 mmol; Aldrich, 99.999%) was dissolved in 2M HCl (0.5 ml; Aldrich, ACS reagent, 37%), and this solution was added to a stock solution of 0.063 M Pu(VI)O₂²⁺ in 2M HCl (1 ml, 0.063 mmol; Fisher, Certified ACS Plus) (Sessler et al., 2002). The vial containing the solution was covered loosely with parafilm and allowed to stand for 2 weeks at room temperature. Following evaporation of the solvent, dark golden-brown blocks formed. A dark golden-brown block of 0.22 x 0.18 x 0.12 mm was cut from a larger crystal, and then thinly coated with epoxy and placed in a capillary. The capillary was coated with a thin film of acrylic dissolved in ethyl acetate. (Note: this triple containment was necessitated by the health hazards of transuranic materials.)

Structure description top

For related literature, see: Hall et al. (1966); Watkin et al. (1991); Wilkerson et al. (2004); Wilkerson et al. (2007); Bean et al. (2004, 2005); Grenthe et al. (2006); Grigoriev et al. (2004); Runde et al. (2003); Sessler et al. (2002).

Computing details top

Data collection: APEX2 (Bruker, 2003); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2000); software used to prepare material for publication: SHELXTL (Bruker, 2000).

Figures top

Fig. 1. Molecular structure (70% probability displacement ellipsoids) of Cs₂PuO₂Cl₄ and the atom-numbering scheme used in Table 1. Symmetry codes as in Table 1.

Dicaesium tetrachloridodioxidoplutonium(VI) top

Crystal data top

Cs₂[PuCl₄O₂]	Z = 2
M_r = 678.67	F(000) = 576
Monoclinic, C2/m	D_x = 4.245 Mg m⁻³
Hall symbol: -C 2y	Mo Kα radiation, λ = 0.71073 Å
a = 11.9489 (7) Å	θ = 3.2–28.7°
b = 7.7286 (5) Å	µ = 13.92 mm⁻¹
c = 5.7855 (4) Å	T = 141 K
β = 96.439 (1)°	Irregular, golden brown
V = 530.91 (6) Å³	0.22 × 0.18 × 0.12 mm

Data collection top

Bruker D8 with APEXII CCD diffractometer	711 independent reflections
Radiation source: fine-focus sealed tube	659 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.025
ω scans	θ_max = 28.7°, θ_min = 3.2°
Absorption correction: multi-scan (SADABS; Sheldrick, 2001)	h = −15→15
T_min = 0.150, T_max = 0.286	k = −10→10
3212 measured reflections	l = −7→7

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)] = 0.015	w = 1/[σ²(F_o²) + (0.0151P)²] where P = (F_o² + 2F_c²)/3
wR(F²) = 0.037	(Δ/σ)_max = 0.001
S = 1.26	Δρ_max = 0.78 e Å⁻³
711 reflections	Δρ_min = −0.64 e Å⁻³
27 parameters	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
0 restraints	Extinction coefficient: 0.0050 (2)

Crystal data top

Cs₂[PuCl₄O₂]	V = 530.91 (6) Å³
M_r = 678.67	Z = 2
Monoclinic, C2/m	Mo Kα radiation
a = 11.9489 (7) Å	µ = 13.92 mm⁻¹
b = 7.7286 (5) Å	T = 141 K
c = 5.7855 (4) Å	0.22 × 0.18 × 0.12 mm
β = 96.439 (1)°

Data collection top

Bruker D8 with APEXII CCD diffractometer	711 independent reflections
Absorption correction: multi-scan (SADABS; Sheldrick, 2001)	659 reflections with I > 2σ(I)
T_min = 0.150, T_max = 0.286	R_int = 0.025
3212 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.015	27 parameters
wR(F²) = 0.037	0 restraints
S = 1.26	Δρ_max = 0.78 e Å⁻³
711 reflections	Δρ_min = −0.64 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	U_iso*/U_eq
Pu1	0.0000	0.0000	0.0000	0.02605 (11)
Cs1	0.34147 (2)	0.0000	0.69601 (6)	0.03801 (11)
Cl1	−0.10351 (7)	−0.24889 (10)	0.21367 (16)	0.0390 (2)
O1	0.1124 (3)	0.0000	0.2222 (6)	0.0395 (8)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Pu1	0.02849 (15)	0.02078 (14)	0.02946 (15)	0.000	0.00583 (9)	0.000
Cs1	0.03790 (19)	0.03608 (19)	0.0419 (2)	0.000	0.01250 (15)	0.000
Cl1	0.0436 (4)	0.0305 (4)	0.0454 (5)	−0.0015 (3)	0.0162 (4)	0.0058 (3)
O1	0.0381 (19)	0.0424 (19)	0.0371 (19)	0.000	0.0002 (16)	0.000

Geometric parameters (Å, º) top

Pu1—O1ⁱ	1.752 (3)	Cs1—Cl1^xii	3.5201 (8)
Pu1—O1	1.752 (3)	Cs1—Cl1^viii	3.5201 (8)
Pu1—Cl1ⁱⁱ	2.6648 (8)	Cs1—Cl1^xiii	3.5674 (10)
Pu1—Cl1	2.6648 (8)	Cs1—Cl1^xiv	3.5674 (10)
Pu1—Cl1ⁱⁱⁱ	2.6648 (8)	Cs1—O1	3.650 (4)
Pu1—Cl1ⁱ	2.6648 (8)	Cs1—Cl1^xv	3.6710 (9)
Pu1—Cs1^iv	4.5680 (3)	Cs1—Cl1^vi	3.6710 (9)
Pu1—Cs1^v	4.5680 (3)	Cs1—Pu1^xiii	4.5680 (3)
Pu1—Cs1^vi	4.5680 (3)	Cs1—Pu1^xvi	4.5680 (3)
Pu1—Cs1^vii	4.5680 (3)	Cs1—Pu1^xvii	4.6207 (3)
Pu1—Cs1^viii	4.6207 (3)	Cl1—Cs1^xviii	3.5209 (9)
Pu1—Cs1^ix	4.6207 (3)	Cl1—Cs1^viii	3.5201 (8)
Cs1—Cl1^x	3.5209 (9)	Cl1—Cs1^iv	3.5674 (10)
Cs1—Cl1^xi	3.5209 (9)	Cl1—Cs1^vi	3.6710 (9)

O1ⁱ—Pu1—O1	180.0 (3)	Cl1^x—Cs1—Cl1^xiii	158.75 (3)
O1ⁱ—Pu1—Cl1ⁱⁱ	90.98 (8)	Cl1^xi—Cs1—Cl1^xiii	109.41 (2)
O1—Pu1—Cl1ⁱⁱ	89.02 (8)	Cl1^xii—Cs1—Cl1^xiii	104.390 (15)
O1ⁱ—Pu1—Cl1	89.02 (8)	Cl1^viii—Cs1—Cl1^xiii	69.76 (2)
O1—Pu1—Cl1	90.98 (8)	Cl1^x—Cs1—Cl1^xiv	109.41 (2)
Cl1ⁱⁱ—Pu1—Cl1	87.58 (3)	Cl1^xi—Cs1—Cl1^xiv	158.75 (3)
O1ⁱ—Pu1—Cl1ⁱⁱⁱ	89.02 (8)	Cl1^xii—Cs1—Cl1^xiv	69.76 (2)
O1—Pu1—Cl1ⁱⁱⁱ	90.98 (8)	Cl1^viii—Cs1—Cl1^xiv	104.390 (15)
Cl1ⁱⁱ—Pu1—Cl1ⁱⁱⁱ	180.00 (5)	Cl1^xiii—Cs1—Cl1^xiv	65.91 (3)
Cl1—Pu1—Cl1ⁱⁱⁱ	92.42 (3)	Cl1^x—Cs1—O1	66.15 (5)
O1ⁱ—Pu1—Cl1ⁱ	90.98 (8)	Cl1^xi—Cs1—O1	66.15 (5)
O1—Pu1—Cl1ⁱ	89.02 (8)	Cl1^xii—Cs1—O1	63.98 (5)
Cl1ⁱⁱ—Pu1—Cl1ⁱ	92.42 (3)	Cl1^viii—Cs1—O1	63.98 (5)
Cl1—Pu1—Cl1ⁱ	180.00 (4)	Cl1^xiii—Cs1—O1	133.04 (4)
Cl1ⁱⁱⁱ—Pu1—Cl1ⁱ	87.58 (3)	Cl1^xiv—Cs1—O1	133.04 (4)
O1ⁱ—Pu1—Cs1^iv	57.778 (4)	Cl1^x—Cs1—Cl1^xv	99.912 (18)
O1—Pu1—Cs1^iv	122.222 (4)	Cl1^xi—Cs1—Cl1^xv	65.75 (3)
Cl1ⁱⁱ—Pu1—Cs1^iv	53.469 (18)	Cl1^xii—Cs1—Cl1^xv	163.34 (3)
Cl1—Pu1—Cs1^iv	51.24 (2)	Cl1^viii—Cs1—Cl1^xv	112.348 (8)
Cl1ⁱⁱⁱ—Pu1—Cs1^iv	126.531 (18)	Cl1^xiii—Cs1—Cl1^xv	61.25 (2)
Cl1ⁱ—Pu1—Cs1^iv	128.76 (2)	Cl1^xiv—Cs1—Cl1^xv	95.403 (19)
O1ⁱ—Pu1—Cs1^v	122.222 (4)	O1—Cs1—Cl1^xv	131.50 (4)
O1—Pu1—Cs1^v	57.778 (4)	Cl1^x—Cs1—Cl1^vi	65.75 (3)
Cl1ⁱⁱ—Pu1—Cs1^v	126.531 (18)	Cl1^xi—Cs1—Cl1^vi	99.912 (18)
Cl1—Pu1—Cs1^v	128.76 (2)	Cl1^xii—Cs1—Cl1^vi	112.348 (8)
Cl1ⁱⁱⁱ—Pu1—Cs1^v	53.469 (18)	Cl1^viii—Cs1—Cl1^vi	163.34 (3)
Cl1ⁱ—Pu1—Cs1^v	51.24 (2)	Cl1^xiii—Cs1—Cl1^vi	95.403 (19)
Cs1^iv—Pu1—Cs1^v	180.000 (8)	Cl1^xiv—Cs1—Cl1^vi	61.25 (2)
O1ⁱ—Pu1—Cs1^vi	122.222 (4)	O1—Cs1—Cl1^vi	131.50 (4)
O1—Pu1—Cs1^vi	57.778 (4)	Cl1^xv—Cs1—Cl1^vi	63.83 (3)
Cl1ⁱⁱ—Pu1—Cs1^vi	51.24 (2)	Cl1^x—Cs1—Pu1^xiii	131.698 (14)
Cl1—Pu1—Cs1^vi	53.469 (18)	Cl1^xi—Cs1—Pu1^xiii	74.494 (15)
Cl1ⁱⁱⁱ—Pu1—Cs1^vi	128.76 (2)	Cl1^xii—Cs1—Pu1^xiii	135.406 (14)
Cl1ⁱ—Pu1—Cs1^vi	126.531 (18)	Cl1^viii—Cs1—Pu1^xiii	77.734 (14)
Cs1^iv—Pu1—Cs1^vi	64.454 (8)	Cl1^xiii—Cs1—Pu1^xiii	35.626 (12)
Cs1^v—Pu1—Cs1^vi	115.546 (8)	Cl1^xiv—Cs1—Pu1^xiii	96.174 (16)
O1ⁱ—Pu1—Cs1^vii	57.778 (4)	O1—Cs1—Pu1^xiii	122.194 (5)
O1—Pu1—Cs1^vii	122.222 (4)	Cl1^xv—Cs1—Pu1^xiii	35.683 (12)
Cl1ⁱⁱ—Pu1—Cs1^vii	128.76 (2)	Cl1^vi—Cs1—Pu1^xiii	94.713 (15)
Cl1—Pu1—Cs1^vii	126.531 (18)	Cl1^x—Cs1—Pu1^xvi	74.494 (15)
Cl1ⁱⁱⁱ—Pu1—Cs1^vii	51.24 (2)	Cl1^xi—Cs1—Pu1^xvi	131.698 (14)
Cl1ⁱ—Pu1—Cs1^vii	53.469 (18)	Cl1^xii—Cs1—Pu1^xvi	77.734 (14)
Cs1^iv—Pu1—Cs1^vii	115.546 (8)	Cl1^viii—Cs1—Pu1^xvi	135.406 (14)
Cs1^v—Pu1—Cs1^vii	64.454 (8)	Cl1^xiii—Cs1—Pu1^xvi	96.174 (16)
Cs1^vi—Pu1—Cs1^vii	180.000 (7)	Cl1^xiv—Cs1—Pu1^xvi	35.626 (12)
O1ⁱ—Pu1—Cs1^viii	69.04 (11)	O1—Cs1—Pu1^xvi	122.194 (5)
O1—Pu1—Cs1^viii	110.96 (11)	Cl1^xv—Cs1—Pu1^xvi	94.713 (15)
Cl1ⁱⁱ—Pu1—Cs1^viii	130.706 (17)	Cl1^vi—Cs1—Pu1^xvi	35.683 (12)
Cl1—Pu1—Cs1^viii	49.294 (17)	Pu1^xiii—Cs1—Pu1^xvi	115.546 (8)
Cl1ⁱⁱⁱ—Pu1—Cs1^viii	49.294 (17)	Cl1^x—Cs1—Pu1^xvii	123.572 (15)
Cl1ⁱ—Pu1—Cs1^viii	130.706 (17)	Cl1^xi—Cs1—Pu1^xvii	123.572 (15)
Cs1^iv—Pu1—Cs1^viii	78.510 (5)	Cl1^xii—Cs1—Pu1^xvii	35.021 (13)
Cs1^v—Pu1—Cs1^viii	101.490 (5)	Cl1^viii—Cs1—Pu1^xvii	35.021 (13)
Cs1^vi—Pu1—Cs1^viii	101.490 (5)	Cl1^xiii—Cs1—Pu1^xvii	76.579 (13)
Cs1^vii—Pu1—Cs1^viii	78.510 (5)	Cl1^xiv—Cs1—Pu1^xvii	76.579 (13)
O1ⁱ—Pu1—Cs1^ix	110.96 (11)	O1—Cs1—Pu1^xvii	70.49 (5)
O1—Pu1—Cs1^ix	69.04 (11)	Cl1^xv—Cs1—Pu1^xvii	136.161 (13)
Cl1ⁱⁱ—Pu1—Cs1^ix	49.294 (17)	Cl1^vi—Cs1—Pu1^xvii	136.161 (13)
Cl1—Pu1—Cs1^ix	130.706 (17)	Pu1^xiii—Cs1—Pu1^xvii	101.490 (5)
Cl1ⁱⁱⁱ—Pu1—Cs1^ix	130.706 (17)	Pu1^xvi—Cs1—Pu1^xvii	101.490 (5)
Cl1ⁱ—Pu1—Cs1^ix	49.294 (17)	Pu1—Cl1—Cs1^xviii	154.58 (3)
Cs1^iv—Pu1—Cs1^ix	101.490 (5)	Pu1—Cl1—Cs1^viii	95.68 (2)
Cs1^v—Pu1—Cs1^ix	78.510 (5)	Cs1^xviii—Cl1—Cs1^viii	87.583 (18)
Cs1^vi—Pu1—Cs1^ix	78.510 (5)	Pu1—Cl1—Cs1^iv	93.13 (2)
Cs1^vii—Pu1—Cs1^ix	101.490 (5)	Cs1^xviii—Cl1—Cs1^iv	109.41 (2)
Cs1^viii—Pu1—Cs1^ix	180.000 (3)	Cs1^viii—Cl1—Cs1^iv	110.24 (2)
Cl1^x—Cs1—Cl1^xi	66.90 (3)	Pu1—Cl1—Cs1^vi	90.85 (2)
Cl1^x—Cs1—Cl1^xii	92.417 (18)	Cs1^xviii—Cl1—Cs1^vi	80.088 (18)
Cl1^xi—Cs1—Cl1^xii	130.133 (13)	Cs1^viii—Cl1—Cs1^vi	163.34 (3)
Cl1^x—Cs1—Cl1^viii	130.133 (13)	Cs1^iv—Cl1—Cs1^vi	84.597 (19)
Cl1^xi—Cs1—Cl1^viii	92.417 (18)	Pu1—O1—Cs1	178.55 (16)
Cl1^xii—Cs1—Cl1^viii	66.25 (3)

Symmetry codes: (i) −x, −y, −z; (ii) −x, y, −z; (iii) x, −y, z; (iv) x−1/2, y−1/2, z−1; (v) −x+1/2, −y+1/2, −z+1; (vi) −x+1/2, −y−1/2, −z+1; (vii) x−1/2, y+1/2, z−1; (viii) −x, −y, −z+1; (ix) x, y, z−1; (x) x+1/2, −y−1/2, z; (xi) x+1/2, y+1/2, z; (xii) −x, y, −z+1; (xiii) x+1/2, y+1/2, z+1; (xiv) x+1/2, −y−1/2, z+1; (xv) −x+1/2, y+1/2, −z+1; (xvi) x+1/2, y−1/2, z+1; (xvii) x, y, z+1; (xviii) x−1/2, y−1/2, z.

Experimental details

Crystal data
Chemical formula	Cs₂[PuCl₄O₂]
M_r	678.67
Crystal system, space group	Monoclinic, C2/m
Temperature (K)	141
a, b, c (Å)	11.9489 (7), 7.7286 (5), 5.7855 (4)
β (°)	96.439 (1)
V (Å³)	530.91 (6)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	13.92
Crystal size (mm)	0.22 × 0.18 × 0.12

Data collection
Diffractometer	Bruker D8 with APEXII CCD
Absorption correction	Multi-scan (SADABS; Sheldrick, 2001)
T_min, T_max	0.150, 0.286
No. of measured, independent and observed [I > 2σ(I)] reflections	3212, 711, 659
R_int	0.025
(sin θ/λ)_max (Å⁻¹)	0.676

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.015, 0.037, 1.26
No. of reflections	711
No. of parameters	27
Δρ_max, Δρ_min (e Å⁻³)	0.78, −0.64

Computer programs: APEX2 (Bruker, 2003), SAINT-Plus (Bruker, 2001), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), SHELXTL (Bruker, 2000).

Acknowledgements

We thank Mr Phillip Palmer and Mr Sean D. Reilly for technical assistance. This research at Los Alamos National Laboratory was supported by NA-22, Office of Nonproliferation Research and Engineering, US Department of Energy, National Nuclear Security Administration (NNSA), and Office of Basic Energy Sciences, US Department of Energy. Los Alamos National Laboratory is operated by Los Alamos National Security, LLC for the US Department of Energy, NNSA under contract number DE-AC52-06NA25396.

References

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