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Acta Crystallogr Sect E Struct Rep Online. 2009 March 1; 65(Pt 3): i14.
Published online 2009 February 11. doi:  10.1107/S160053680900395X
PMCID: PMC2968520

Neptunium(III) copper(I) diselenide

Abstract

The title compound, NpCuSe2, is the first ternary neptunium transition-metal chalcogenide. It was synthesized from the elements at 873 K in an evacuated fused-silica tube. Single crystals were grown by vapor transport with I2. NpCuSe2 crystallizes in the LaCuS2 structure type and can be viewed as a stacking of layers of CuSe4 tetra­hedra and of double layers of NpSe7 monocapped trigonal prisms along [100]. Because there are no Se—Se bonds in the structure, the formal oxidation states of Np/Cu/Se may be assigned as +III/+I/−II, respectively.

Related literature

For discussion of the LaCuS2 structure type, see: Julien-Pouzol et al. (1981 [triangle]); Ijjaali et al. (2004 [triangle]). For other compounds with Cu—Se bonds, see: Daoudi et al. (1996 [triangle]); Strobel & Schleid (2004 [triangle]); Ijjaali et al. (2004 [triangle]). For other neptunium selenides, see: Wastin et al. (1995 [triangle]); Wojakowski (1985 [triangle]). For computational details, see Gelato & Parthé (1987 [triangle]).

Experimental

Crystal data

  • NpCuSe2
  • M r = 458.46
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-65-00i14-efi1.jpg
  • a = 6.6796 (5) Å
  • b = 7.4384 (6) Å
  • c = 7.1066 (5) Å
  • β = 97.156 (1)°
  • V = 350.34 (5) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 56.06 mm−1
  • T = 100 (2) K
  • 0.08 × 0.05 × 0.04 mm

Data collection

  • Bruker APEXII CCD diffractometer
  • Absorption correction: numerical (face indexed; SADABS; Sheldrick, 2006 [triangle]) T min = 0.045, T max = 0.212
  • 6189 measured reflections
  • 1376 independent reflections
  • 1309 reflections with I > 2σ(I)
  • R int = 0.036

Refinement

  • R[F 2 > 2σ(F 2)] = 0.028
  • wR(F 2) = 0.068
  • S = 1.35
  • 1376 reflections
  • 37 parameters
  • Δρmax = 2.43 e Å−3
  • Δρmin = −4.48 e Å−3

Data collection: APEX2 (Bruker, 2006 [triangle]); cell refinement: SAINT (Bruker, 2006 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: CrystalMaker (Palmer, 2008 [triangle]); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 [triangle]).

Table 1
Selected geometric parameters (Å, °)

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S160053680900395X/wm2219sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S160053680900395X/wm2219Isup2.hkl

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

Acknowledgments

The research was supported at Northwestern University by the US Department of Energy, Basic Energy Sciences grant ER-15522, and at Argonne National Laboratory by the US Department of Energy, OBES, Chemical Sciences Division, under contract DEAC02–06CH11357. We are indebted to Dr Richard G. Haire of Oak Ridge National Laboratory for the gift of Np metal.

supplementary crystallographic information

Comment

In keeping with earlier descriptions of the LaCuS2 structure type (Julien-Pouzol et al., 1981; Ijjaali et al., 2004) the structure of NpCuSe2 can be viewed as a stacking of layers of CuSe4 tetrahedra and double layers of NpSe7 monocapped trigonal prisms along [100]. Figure 1 provides a view nearly down [010] of the unit cell. It displays the stacking of layers along [100] where atom Se1 is contained within the Cu layer and atom Se2 is contained within the Np double layer. The Cu—Se bond distances are reasonable for a Cu(I) compound; they range from 2.4409 (9) to 2.5899 (9) Å compared to 2.458 (2) to 2.490 (4) Å in SrCuCeSe3 (Strobel & Schleid, 2004) and 2.450 (1) to 2.607 (1) Å in the Ce analogue CeCuSe2 (Ijjaali et al., 2004). The Np—Se bond distances range from 2.9330 (6) to 3.1419 (6) Å. Comparisons are limited but can be made with the Np—Se distance of 2.903 (1) Å in NpSe (Wastin et al., 1995) and those of 2.932 and 3.086 Å in NpAsSe (Wojakowski, 1985). There are no Se—Se bonds in NpCuSe2, so formal oxidation states may be assigned for Np/Cu/Se of +III/+I/-II.

The chemistry of Np is transitional between that of U and Pu. All three elements exhibit multiple oxidation states in their compounds. NpCuSe2 is the first example of a neptunium chalcogenide compound analogous to a lanthanide(III) structure rather than to a transition-metal or uranium(IV) structure. The Pu analogue is unknown, although arguments based on the stability of various Pu oxidation states suggest it should be stable.

Experimental

NpCuSe2was formed in an attempted synthesis of the Np analogue of U3Cu2Se7 (Daoudi et al., 1996). Caution! 237Np is an α-emitting radioisotope and as such is considered a health risk. Its use requires appropriate infrastructure and personnel trained in the handling of radioactive materials. The following reagents were used as obtained from the manufacturer: Cu (Aldrich, 99.5%) and Se (Aldrich, 99%). Resublimed I2 was utilized as a transport reagent. 237Np chunks were crushed and used as provided from Oak Ridge National Laboratory. A reaction mixture of 20.2 mg Np (0.085 mmol), 3.58 mg Cu (0.056 mmol), and 15.55 mg Se (0.197 mmol) was loaded into a fused-silica ampoule in an Ar-filled dry box that was then evacuated to 10 -4 Torr and sealed. The sample was placed in a computer controlled furnace, heated to 873 K in 8 h, kept at 873 K for 72 h, cooled at 5 K/h to 373 K, and finally air cooled in the oven to 298 K. The resultant black powder was reloaded into a fused-silica ampoule with 4 mg I2. The ampoule was evacuated to 10 -4 Torr and sealed. The sample was placed in a computer controlled furnace, heated to 873 K in 8 h, kept at 873 K for 336 h, cooled at 6.94 K/h to 373 K, before finally being air cooled to 298 K. Black rectangular plates and blocks of NpCuSe2 were obtained in low yield. The crystals used in characterization were manually extracted from the product mixture.

Refinement

The program STRUCTURE TIDY (Gelato & Parthé, 1987) was employed to standardize the atomic coordinates of the structure. The highest peak is 1.71 Å and the deepest hole is 0.08 Å from atom Np1.

Figures

Fig. 1.
A view nearly down [010] of the unit cell of NpCuSe2, with displacement ellipsoids at the 99% probability level.

Crystal data

NpCuSe2F(000) = 760
Mr = 458.46Dx = 8.692 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 4110 reflections
a = 6.6796 (5) Åθ = 4.0–33.7°
b = 7.4384 (6) ŵ = 56.06 mm1
c = 7.1066 (5) ÅT = 100 K
β = 97.156 (1)°Block, black
V = 350.34 (5) Å30.08 × 0.05 × 0.04 mm
Z = 4

Data collection

Bruker APEXII CCD diffractometer1376 independent reflections
Radiation source: fine-focus sealed tube1309 reflections with I > 2σ(I)
graphiteRint = 0.036
[var phi] and ω scansθmax = 33.9°, θmin = 3.1°
Absorption correction: numerical (face indexed; SADABS; Sheldrick, 2006)h = −10→10
Tmin = 0.045, Tmax = 0.212k = −11→11
6189 measured reflectionsl = −11→11

Refinement

Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.028Secondary atom site location: difference Fourier map
wR(F2) = 0.068w = [1/[σ2(Fo2) + (0.0312)Fo2]2
S = 1.35(Δ/σ)max < 0.001
1376 reflectionsΔρmax = 2.43 e Å3
37 parametersΔρmin = −4.48 e Å3

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

xyzUiso*/Ueq
Cu10.07000 (11)0.66155 (10)0.04945 (11)0.00850 (14)
Np10.30684 (3)0.04823 (3)0.19759 (3)0.00478 (8)
Se10.09977 (8)0.39107 (7)0.28075 (8)0.00539 (11)
Se20.58173 (9)0.27585 (7)0.00026 (8)0.00520 (11)

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
Cu10.0082 (3)0.0081 (3)0.0091 (3)−0.0008 (2)0.0009 (2)−0.0017 (2)
Np10.00560 (11)0.00354 (11)0.00509 (11)−0.00032 (6)0.00021 (8)−0.00020 (6)
Se10.0063 (2)0.0041 (2)0.0056 (2)0.00028 (16)−0.00019 (18)−0.00004 (17)
Se20.0058 (2)0.0044 (2)0.0051 (2)0.00028 (17)−0.00027 (18)0.00013 (17)

Geometric parameters (Å, °)

Cu1—Se2i2.4409 (9)Np1—Se12.9950 (6)
Cu1—Se1ii2.4490 (9)Np1—Se1v3.1419 (6)
Cu1—Se1iii2.5066 (9)Np1—Cu1viii3.3772 (8)
Cu1—Se12.5899 (9)Np1—Cu1x3.3866 (8)
Cu1—Cu1iii2.6421 (15)Np1—Cu1vii3.4894 (8)
Cu1—Np1ii3.3772 (8)Se1—Cu1viii2.4490 (9)
Cu1—Np1iv3.3866 (8)Se1—Cu1iii2.5066 (9)
Cu1—Np1v3.4894 (8)Se1—Np1ii2.9784 (6)
Np1—Se2vi2.9330 (6)Se1—Np1vii3.1419 (6)
Np1—Se2vii2.9540 (6)Se2—Cu1i2.4409 (9)
Np1—Se22.9743 (6)Se2—Np1vi2.9330 (6)
Np1—Se1viii2.9784 (6)Se2—Np1v2.9540 (6)
Np1—Se2ix2.9785 (6)Se2—Np1xi2.9785 (6)
Se2i—Cu1—Se1ii116.52 (4)Se2vi—Np1—Cu1viii135.297 (18)
Se2i—Cu1—Se1iii102.85 (3)Se2vii—Np1—Cu1viii86.489 (18)
Se1ii—Cu1—Se1iii112.76 (4)Se2—Np1—Cu1viii130.824 (18)
Se2i—Cu1—Se1103.94 (3)Se1viii—Np1—Cu1viii47.587 (17)
Se1ii—Cu1—Se1103.44 (3)Se2ix—Np1—Cu1viii85.522 (17)
Se1iii—Cu1—Se1117.57 (3)Se1—Np1—Cu1viii44.705 (16)
Se2i—Cu1—Cu1iii116.56 (4)Se1v—Np1—Cu1viii101.316 (18)
Se1ii—Cu1—Cu1iii126.51 (5)Se2vi—Np1—Cu1x44.728 (17)
Se1iii—Cu1—Cu1iii60.33 (3)Se2vii—Np1—Cu1x145.739 (18)
Se1—Cu1—Cu1iii57.24 (3)Se2—Np1—Cu1x128.963 (18)
Se2i—Cu1—Np1ii155.73 (3)Se1viii—Np1—Cu1x44.687 (17)
Se1ii—Cu1—Np1ii59.35 (2)Se2ix—Np1—Cu1x73.231 (18)
Se1iii—Cu1—Np1ii100.32 (3)Se1—Np1—Cu1x125.113 (18)
Se1—Cu1—Np1ii58.107 (19)Se1v—Np1—Cu1x72.255 (17)
Cu1iii—Cu1—Np1ii69.64 (3)Cu1viii—Np1—Cu1x91.556 (15)
Se2i—Cu1—Np1iv57.74 (2)Se2vi—Np1—Cu1vii98.092 (18)
Se1ii—Cu1—Np1iv58.79 (2)Se2vii—Np1—Cu1vii88.423 (18)
Se1iii—Cu1—Np1iv124.26 (3)Se2—Np1—Cu1vii162.568 (18)
Se1—Cu1—Np1iv117.81 (3)Se1viii—Np1—Cu1vii44.741 (17)
Cu1iii—Cu1—Np1iv172.48 (5)Se2ix—Np1—Cu1vii43.454 (17)
Np1ii—Cu1—Np1iv113.38 (2)Se1—Np1—Cu1vii88.717 (17)
Se2i—Cu1—Np1v57.06 (2)Se1v—Np1—Cu1vii123.660 (17)
Se1ii—Cu1—Np1v160.72 (3)Cu1viii—Np1—Cu1vii45.22 (2)
Se1iii—Cu1—Np1v56.76 (2)Cu1x—Np1—Cu1vii66.861 (13)
Se1—Cu1—Np1v95.83 (3)Cu1viii—Se1—Cu1iii99.74 (3)
Cu1iii—Cu1—Np1v65.14 (3)Cu1viii—Se1—Cu1148.28 (3)
Np1ii—Cu1—Np1v134.78 (2)Cu1iii—Se1—Cu162.43 (3)
Np1iv—Cu1—Np1v111.51 (2)Cu1viii—Se1—Np1ii76.53 (2)
Se2vi—Np1—Se2vii122.772 (13)Cu1iii—Se1—Np1ii78.50 (2)
Se2vi—Np1—Se291.915 (16)Cu1—Se1—Np1ii74.31 (2)
Se2vii—Np1—Se274.152 (12)Cu1viii—Se1—Np175.95 (2)
Se2vi—Np1—Se1viii89.408 (17)Cu1iii—Se1—Np181.29 (2)
Se2vii—Np1—Se1viii128.634 (17)Cu1—Se1—Np1122.48 (3)
Se2—Np1—Se1viii150.258 (17)Np1ii—Se1—Np1142.27 (2)
Se2vi—Np1—Se2ix74.394 (9)Cu1viii—Se1—Np1vii79.17 (2)
Se2vii—Np1—Se2ix72.516 (18)Cu1iii—Se1—Np1vii178.90 (3)
Se2—Np1—Se2ix127.853 (11)Cu1—Se1—Np1vii118.47 (3)
Se1viii—Np1—Se2ix80.988 (16)Np1ii—Se1—Np1vii101.074 (17)
Se2vi—Np1—Se1160.988 (17)Np1—Se1—Np1vii98.541 (17)
Se2vii—Np1—Se174.905 (16)Cu1i—Se2—Np1vi77.53 (2)
Se2—Np1—Se186.315 (17)Cu1i—Se2—Np1v109.10 (3)
Se1viii—Np1—Se182.962 (10)Np1vi—Se2—Np1v100.770 (17)
Se2ix—Np1—Se1121.133 (17)Cu1i—Se2—Np1146.34 (3)
Se2vi—Np1—Se1v76.958 (16)Np1vi—Se2—Np188.085 (16)
Se2vii—Np1—Se1v141.588 (16)Np1v—Se2—Np1103.371 (19)
Se2—Np1—Se1v72.469 (16)Cu1i—Se2—Np1xi79.48 (2)
Se1viii—Np1—Se1v78.926 (17)Np1vi—Se2—Np1xi148.12 (2)
Se2ix—Np1—Se1v144.944 (16)Np1v—Se2—Np1xi107.484 (18)
Se1—Np1—Se1v84.479 (14)Np1—Se2—Np1xi99.254 (17)

Symmetry codes: (i) −x+1, −y+1, −z; (ii) −x, y+1/2, −z+1/2; (iii) −x, −y+1, −z; (iv) x, y+1, z; (v) x, −y+1/2, z−1/2; (vi) −x+1, −y, −z; (vii) x, −y+1/2, z+1/2; (viii) −x, y−1/2, −z+1/2; (ix) −x+1, y−1/2, −z+1/2; (x) x, y−1, z; (xi) −x+1, y+1/2, −z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: WM2219).

References

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