Neptunium(III) copper(I) diselenide

Wells, D.M.; Skanthakumar, S.; Soderholm, L.; Ibers, J.A.

doi:10.1107/S160053680900395X

inorganic compounds

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Volume 65| Part 3| March 2009| Page i14

doi:10.1107/S160053680900395X

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Neptunium(III) copper(I) diselenide

Daniel M. Wells,^a S. Skanthakumar,^b L. Soderholm ^b and James A. Ibers ^a ^*

^aChemistry Department, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208, USA, and ^bChemistry Division, Argonne National Laboratory, Argonne, IL 60439, USA
^*Correspondence e-mail: ibers@chem.northwestern.edu

(Received 23 January 2009; accepted 2 February 2009; online 11 February 2009)

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 ); Ijjaali et al. (2004 ). For other compounds with Cu—Se bonds, see: Daoudi et al. (1996 ); Strobel & Schleid (2004 ); Ijjaali et al. (2004). For other neptunium selenides, see: Wastin et al. (1995 ); Wojakowski (1985 ). For computational details, see Gelato & Parthé (1987 ).

Experimental

Crystal data

NpCuSe₂
M_r = 458.46
Monoclinic, P 2₁ /c
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 ) 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[F² > 2σ(F²)] = 0.028
wR(F²) = 0.068
S = 1.35
1376 reflections
37 parameters
Δρ_max = 2.43 e Å⁻³
Δρ_min = −4.48 e Å⁻³

Table 1
Selected geometric parameters (Å, °)

Cu1—Se2ⁱ	2.4409 (9)
Cu1—Se1ⁱⁱ	2.4490 (9)
Cu1—Se1ⁱⁱⁱ	2.5066 (9)
Cu1—Se1	2.5899 (9)
Np1—Se2^iv	2.9330 (6)
Np1—Se2^v	2.9540 (6)
Np1—Se2	2.9743 (6)
Np1—Se1^vi	2.9784 (6)
Np1—Se2^vii	2.9785 (6)
Np1—Se1	2.9950 (6)
Np1—Se1^viii	3.1419 (6)

Se2ⁱ—Cu1—Se1ⁱⁱ	116.52 (4)
Se2ⁱ—Cu1—Se1ⁱⁱⁱ	102.85 (3)
Se1ⁱⁱ—Cu1—Se1ⁱⁱⁱ	112.76 (4)
Se2ⁱ—Cu1—Se1	103.94 (3)
Se1ⁱⁱ—Cu1—Se1	103.44 (3)
Symmetry codes: (i) -x+1, -y+1, -z; (ii) $[-x, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) -x, -y+1, -z; (iv) -x+1, -y, -z; (v) $[x, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (vi) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (vii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (viii) $[x, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

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

Supporting information

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

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

checkCIF report

Comment top

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.

Related literature top

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

Experimental top

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.

Computing details top

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

Figures top

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

Neptunium(III) copper(I) diselenide top

Crystal data top

NpCuSe₂	F(000) = 760
M_r = 458.46	D_x = 8.692 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4110 reflections
a = 6.6796 (5) Å	θ = 4.0–33.7°
b = 7.4384 (6) Å	µ = 56.06 mm⁻¹
c = 7.1066 (5) Å	T = 100 K
β = 97.156 (1)°	Block, black
V = 350.34 (5) Å³	0.08 × 0.05 × 0.04 mm
Z = 4

Data collection top

Bruker APEXII CCD diffractometer	1376 independent reflections
Radiation source: fine-focus sealed tube	1309 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.036
ϕ and ω scans	θ_max = 33.9°, θ_min = 3.1°
Absorption correction: numerical (face indexed; SADABS; Sheldrick, 2006)	h = −10→10
T_min = 0.045, T_max = 0.212	k = −11→11
6189 measured reflections	l = −11→11

Refinement top

Refinement on F²	0 restraints
Least-squares matrix: full	Primary atom site location: structure-invariant direct methods
R[F² > 2σ(F²)] = 0.028	Secondary atom site location: difference Fourier map
wR(F²) = 0.068	w = [1/[σ²(F_o²) + (0.0312)F_o²]²
S = 1.35	(Δ/σ)_max < 0.001
1376 reflections	Δρ_max = 2.43 e Å⁻³
37 parameters	Δρ_min = −4.48 e Å⁻³

Crystal data top

NpCuSe₂	V = 350.34 (5) Å³
M_r = 458.46	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 6.6796 (5) Å	µ = 56.06 mm⁻¹
b = 7.4384 (6) Å	T = 100 K
c = 7.1066 (5) Å	0.08 × 0.05 × 0.04 mm
β = 97.156 (1)°

Data collection top

Bruker APEXII CCD diffractometer	1376 independent reflections
Absorption correction: numerical (face indexed; SADABS; Sheldrick, 2006)	1309 reflections with I > 2σ(I)
T_min = 0.045, T_max = 0.212	R_int = 0.036
6189 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.028	37 parameters
wR(F²) = 0.068	0 restraints
S = 1.35	Δρ_max = 2.43 e Å⁻³
1376 reflections	Δρ_min = −4.48 e Å⁻³

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

	x	y	z	U_iso*/U_eq
Cu1	0.07000 (11)	0.66155 (10)	0.04945 (11)	0.00850 (14)
Np1	0.30684 (3)	0.04823 (3)	0.19759 (3)	0.00478 (8)
Se1	0.09977 (8)	0.39107 (7)	0.28075 (8)	0.00539 (11)
Se2	0.58173 (9)	0.27585 (7)	0.00026 (8)	0.00520 (11)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0082 (3)	0.0081 (3)	0.0091 (3)	−0.0008 (2)	0.0009 (2)	−0.0017 (2)
Np1	0.00560 (11)	0.00354 (11)	0.00509 (11)	−0.00032 (6)	0.00021 (8)	−0.00020 (6)
Se1	0.0063 (2)	0.0041 (2)	0.0056 (2)	0.00028 (16)	−0.00019 (18)	−0.00004 (17)
Se2	0.0058 (2)	0.0044 (2)	0.0051 (2)	0.00028 (17)	−0.00027 (18)	0.00013 (17)

Geometric parameters (Å, º) top

Cu1—Se2ⁱ	2.4409 (9)	Np1—Se1	2.9950 (6)
Cu1—Se1ⁱⁱ	2.4490 (9)	Np1—Se1^v	3.1419 (6)
Cu1—Se1ⁱⁱⁱ	2.5066 (9)	Np1—Cu1^viii	3.3772 (8)
Cu1—Se1	2.5899 (9)	Np1—Cu1^x	3.3866 (8)
Cu1—Cu1ⁱⁱⁱ	2.6421 (15)	Np1—Cu1^vii	3.4894 (8)
Cu1—Np1ⁱⁱ	3.3772 (8)	Se1—Cu1^viii	2.4490 (9)
Cu1—Np1^iv	3.3866 (8)	Se1—Cu1ⁱⁱⁱ	2.5066 (9)
Cu1—Np1^v	3.4894 (8)	Se1—Np1ⁱⁱ	2.9784 (6)
Np1—Se2^vi	2.9330 (6)	Se1—Np1^vii	3.1419 (6)
Np1—Se2^vii	2.9540 (6)	Se2—Cu1ⁱ	2.4409 (9)
Np1—Se2	2.9743 (6)	Se2—Np1^vi	2.9330 (6)
Np1—Se1^viii	2.9784 (6)	Se2—Np1^v	2.9540 (6)
Np1—Se2^ix	2.9785 (6)	Se2—Np1^xi	2.9785 (6)

Se2ⁱ—Cu1—Se1ⁱⁱ	116.52 (4)	Se2^vi—Np1—Cu1^viii	135.297 (18)
Se2ⁱ—Cu1—Se1ⁱⁱⁱ	102.85 (3)	Se2^vii—Np1—Cu1^viii	86.489 (18)
Se1ⁱⁱ—Cu1—Se1ⁱⁱⁱ	112.76 (4)	Se2—Np1—Cu1^viii	130.824 (18)
Se2ⁱ—Cu1—Se1	103.94 (3)	Se1^viii—Np1—Cu1^viii	47.587 (17)
Se1ⁱⁱ—Cu1—Se1	103.44 (3)	Se2^ix—Np1—Cu1^viii	85.522 (17)
Se1ⁱⁱⁱ—Cu1—Se1	117.57 (3)	Se1—Np1—Cu1^viii	44.705 (16)
Se2ⁱ—Cu1—Cu1ⁱⁱⁱ	116.56 (4)	Se1^v—Np1—Cu1^viii	101.316 (18)
Se1ⁱⁱ—Cu1—Cu1ⁱⁱⁱ	126.51 (5)	Se2^vi—Np1—Cu1^x	44.728 (17)
Se1ⁱⁱⁱ—Cu1—Cu1ⁱⁱⁱ	60.33 (3)	Se2^vii—Np1—Cu1^x	145.739 (18)
Se1—Cu1—Cu1ⁱⁱⁱ	57.24 (3)	Se2—Np1—Cu1^x	128.963 (18)
Se2ⁱ—Cu1—Np1ⁱⁱ	155.73 (3)	Se1^viii—Np1—Cu1^x	44.687 (17)
Se1ⁱⁱ—Cu1—Np1ⁱⁱ	59.35 (2)	Se2^ix—Np1—Cu1^x	73.231 (18)
Se1ⁱⁱⁱ—Cu1—Np1ⁱⁱ	100.32 (3)	Se1—Np1—Cu1^x	125.113 (18)
Se1—Cu1—Np1ⁱⁱ	58.107 (19)	Se1^v—Np1—Cu1^x	72.255 (17)
Cu1ⁱⁱⁱ—Cu1—Np1ⁱⁱ	69.64 (3)	Cu1^viii—Np1—Cu1^x	91.556 (15)
Se2ⁱ—Cu1—Np1^iv	57.74 (2)	Se2^vi—Np1—Cu1^vii	98.092 (18)
Se1ⁱⁱ—Cu1—Np1^iv	58.79 (2)	Se2^vii—Np1—Cu1^vii	88.423 (18)
Se1ⁱⁱⁱ—Cu1—Np1^iv	124.26 (3)	Se2—Np1—Cu1^vii	162.568 (18)
Se1—Cu1—Np1^iv	117.81 (3)	Se1^viii—Np1—Cu1^vii	44.741 (17)
Cu1ⁱⁱⁱ—Cu1—Np1^iv	172.48 (5)	Se2^ix—Np1—Cu1^vii	43.454 (17)
Np1ⁱⁱ—Cu1—Np1^iv	113.38 (2)	Se1—Np1—Cu1^vii	88.717 (17)
Se2ⁱ—Cu1—Np1^v	57.06 (2)	Se1^v—Np1—Cu1^vii	123.660 (17)
Se1ⁱⁱ—Cu1—Np1^v	160.72 (3)	Cu1^viii—Np1—Cu1^vii	45.22 (2)
Se1ⁱⁱⁱ—Cu1—Np1^v	56.76 (2)	Cu1^x—Np1—Cu1^vii	66.861 (13)
Se1—Cu1—Np1^v	95.83 (3)	Cu1^viii—Se1—Cu1ⁱⁱⁱ	99.74 (3)
Cu1ⁱⁱⁱ—Cu1—Np1^v	65.14 (3)	Cu1^viii—Se1—Cu1	148.28 (3)
Np1ⁱⁱ—Cu1—Np1^v	134.78 (2)	Cu1ⁱⁱⁱ—Se1—Cu1	62.43 (3)
Np1^iv—Cu1—Np1^v	111.51 (2)	Cu1^viii—Se1—Np1ⁱⁱ	76.53 (2)
Se2^vi—Np1—Se2^vii	122.772 (13)	Cu1ⁱⁱⁱ—Se1—Np1ⁱⁱ	78.50 (2)
Se2^vi—Np1—Se2	91.915 (16)	Cu1—Se1—Np1ⁱⁱ	74.31 (2)
Se2^vii—Np1—Se2	74.152 (12)	Cu1^viii—Se1—Np1	75.95 (2)
Se2^vi—Np1—Se1^viii	89.408 (17)	Cu1ⁱⁱⁱ—Se1—Np1	81.29 (2)
Se2^vii—Np1—Se1^viii	128.634 (17)	Cu1—Se1—Np1	122.48 (3)
Se2—Np1—Se1^viii	150.258 (17)	Np1ⁱⁱ—Se1—Np1	142.27 (2)
Se2^vi—Np1—Se2^ix	74.394 (9)	Cu1^viii—Se1—Np1^vii	79.17 (2)
Se2^vii—Np1—Se2^ix	72.516 (18)	Cu1ⁱⁱⁱ—Se1—Np1^vii	178.90 (3)
Se2—Np1—Se2^ix	127.853 (11)	Cu1—Se1—Np1^vii	118.47 (3)
Se1^viii—Np1—Se2^ix	80.988 (16)	Np1ⁱⁱ—Se1—Np1^vii	101.074 (17)
Se2^vi—Np1—Se1	160.988 (17)	Np1—Se1—Np1^vii	98.541 (17)
Se2^vii—Np1—Se1	74.905 (16)	Cu1ⁱ—Se2—Np1^vi	77.53 (2)
Se2—Np1—Se1	86.315 (17)	Cu1ⁱ—Se2—Np1^v	109.10 (3)
Se1^viii—Np1—Se1	82.962 (10)	Np1^vi—Se2—Np1^v	100.770 (17)
Se2^ix—Np1—Se1	121.133 (17)	Cu1ⁱ—Se2—Np1	146.34 (3)
Se2^vi—Np1—Se1^v	76.958 (16)	Np1^vi—Se2—Np1	88.085 (16)
Se2^vii—Np1—Se1^v	141.588 (16)	Np1^v—Se2—Np1	103.371 (19)
Se2—Np1—Se1^v	72.469 (16)	Cu1ⁱ—Se2—Np1^xi	79.48 (2)
Se1^viii—Np1—Se1^v	78.926 (17)	Np1^vi—Se2—Np1^xi	148.12 (2)
Se2^ix—Np1—Se1^v	144.944 (16)	Np1^v—Se2—Np1^xi	107.484 (18)
Se1—Np1—Se1^v	84.479 (14)	Np1—Se2—Np1^xi	99.254 (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.

Experimental details

Crystal data
Chemical formula	NpCuSe₂
M_r	458.46
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	6.6796 (5), 7.4384 (6), 7.1066 (5)
β (°)	97.156 (1)
V (Å³)	350.34 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	56.06
Crystal size (mm)	0.08 × 0.05 × 0.04

Data collection
Diffractometer	Bruker APEXII CCD diffractometer
Absorption correction	Numerical (face indexed; SADABS; Sheldrick, 2006)
T_min, T_max	0.045, 0.212
No. of measured, independent and observed [I > 2σ(I)] reflections	6189, 1376, 1309
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.785

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.028, 0.068, 1.35
No. of reflections	1376
No. of parameters	37
Δρ_max, Δρ_min (e Å⁻³)	2.43, −4.48

Computer programs: APEX2 (Bruker, 2006), SAINT (Bruker, 2006), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), CrystalMaker (Palmer, 2008), SHELXTL (Sheldrick, 2008).

Selected geometric parameters (Å, º) top

Cu1—Se2ⁱ	2.4409 (9)	Np1—Se2	2.9743 (6)
Cu1—Se1ⁱⁱ	2.4490 (9)	Np1—Se1^vi	2.9784 (6)
Cu1—Se1ⁱⁱⁱ	2.5066 (9)	Np1—Se2^vii	2.9785 (6)
Cu1—Se1	2.5899 (9)	Np1—Se1	2.9950 (6)
Np1—Se2^iv	2.9330 (6)	Np1—Se1^viii	3.1419 (6)
Np1—Se2^v	2.9540 (6)

Se2ⁱ—Cu1—Se1ⁱⁱ	116.52 (4)	Se2ⁱ—Cu1—Se1	103.94 (3)
Se2ⁱ—Cu1—Se1ⁱⁱⁱ	102.85 (3)	Se1ⁱⁱ—Cu1—Se1	103.44 (3)
Se1ⁱⁱ—Cu1—Se1ⁱⁱⁱ	112.76 (4)

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

Acknowledgements

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.

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