supplementary materials
Neptunium(III) copper(I) diselenide
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.
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.
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.
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).
Neptunium(III) copper(I) diselenide
top
Crystal data top
| NpCuSe2 | F000 = 760 |
| Mr = 458.46 | Dx = 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 = 4.0–33.7º |
| b = 7.4384 (6) Å | µ = 56.06 mm−1 |
| c = 7.1066 (5) Å | T = 100 K |
| β = 97.156 (1)º | 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) |
| Monochromator: graphite | Rint = 0.036 |
| T = 100 K | θmax = 33.9º |
| φ and ω scans | θmin = 3.1º |
Absorption correction: numerical
(face indexed; SADABS; Sheldrick, 2006) | h = −10→10 |
| Tmin = 0.045, Tmax = 0.212 | k = −11→11 |
| 6189 measured reflections | l = −11→11 |
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)] = 0.028 | w = [1/[σ2(Fo2) + (0.0312)Fo2]2 |
| wR(F2) = 0.068 | (Δ/σ)max < 0.001 |
| S = 1.35 | Δρmax = 2.43 e Å−3 |
| 1376 reflections | Δρmin = −4.48 e Å−3 |
| 37 parameters | Extinction correction: none |
Crystal data top
| NpCuSe2 | V = 350.34 (5) Å3 |
| Mr = 458.46 | Z = 4 |
| Monoclinic, P21/c | Mo Kα |
| 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)º | |
Data collection top
Bruker APEXII CCD
diffractometer | 1376 independent reflections |
Absorption correction: numerical
(face indexed; SADABS; Sheldrick, 2006) | 1309 reflections with I > 2σ(I) |
| Tmin = 0.045, Tmax = 0.212 | Rint = 0.036 |
| 6189 measured reflections | |
Refinement top
| R[F2 > 2σ(F2)] = 0.028 | 37 parameters |
| wR(F2) = 0.068 | Δρmax = 2.43 e Å−3 |
| S = 1.35 | Δρmin = −4.48 e Å−3 |
| 1376 reflections | |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top| | x | y | z | Uiso*/Ueq | |
| 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, °) top
| Cu1—Se2i | 2.4409 (9) | Np1—Se1 | 2.9950 (6) |
| Cu1—Se1ii | 2.4490 (9) | Np1—Se1v | 3.1419 (6) |
| Cu1—Se1iii | 2.5066 (9) | Np1—Cu1viii | 3.3772 (8) |
| Cu1—Se1 | 2.5899 (9) | Np1—Cu1x | 3.3866 (8) |
| Cu1—Cu1iii | 2.6421 (15) | Np1—Cu1vii | 3.4894 (8) |
| Cu1—Np1ii | 3.3772 (8) | Se1—Cu1viii | 2.4490 (9) |
| Cu1—Np1iv | 3.3866 (8) | Se1—Cu1iii | 2.5066 (9) |
| Cu1—Np1v | 3.4894 (8) | Se1—Np1ii | 2.9784 (6) |
| Np1—Se2vi | 2.9330 (6) | Se1—Np1vii | 3.1419 (6) |
| Np1—Se2vii | 2.9540 (6) | Se2—Cu1i | 2.4409 (9) |
| Np1—Se2 | 2.9743 (6) | Se2—Np1vi | 2.9330 (6) |
| Np1—Se1viii | 2.9784 (6) | Se2—Np1v | 2.9540 (6) |
| Np1—Se2ix | 2.9785 (6) | Se2—Np1xi | 2.9785 (6) |
| | | |
| Se2i—Cu1—Se1ii | 116.52 (4) | Se2vi—Np1—Cu1viii | 135.297 (18) |
| Se2i—Cu1—Se1iii | 102.85 (3) | Se2vii—Np1—Cu1viii | 86.489 (18) |
| Se1ii—Cu1—Se1iii | 112.76 (4) | Se2—Np1—Cu1viii | 130.824 (18) |
| Se2i—Cu1—Se1 | 103.94 (3) | Se1viii—Np1—Cu1viii | 47.587 (17) |
| Se1ii—Cu1—Se1 | 103.44 (3) | Se2ix—Np1—Cu1viii | 85.522 (17) |
| Se1iii—Cu1—Se1 | 117.57 (3) | Se1—Np1—Cu1viii | 44.705 (16) |
| Se2i—Cu1—Cu1iii | 116.56 (4) | Se1v—Np1—Cu1viii | 101.316 (18) |
| Se1ii—Cu1—Cu1iii | 126.51 (5) | Se2vi—Np1—Cu1x | 44.728 (17) |
| Se1iii—Cu1—Cu1iii | 60.33 (3) | Se2vii—Np1—Cu1x | 145.739 (18) |
| Se1—Cu1—Cu1iii | 57.24 (3) | Se2—Np1—Cu1x | 128.963 (18) |
| Se2i—Cu1—Np1ii | 155.73 (3) | Se1viii—Np1—Cu1x | 44.687 (17) |
| Se1ii—Cu1—Np1ii | 59.35 (2) | Se2ix—Np1—Cu1x | 73.231 (18) |
| Se1iii—Cu1—Np1ii | 100.32 (3) | Se1—Np1—Cu1x | 125.113 (18) |
| Se1—Cu1—Np1ii | 58.107 (19) | Se1v—Np1—Cu1x | 72.255 (17) |
| Cu1iii—Cu1—Np1ii | 69.64 (3) | Cu1viii—Np1—Cu1x | 91.556 (15) |
| Se2i—Cu1—Np1iv | 57.74 (2) | Se2vi—Np1—Cu1vii | 98.092 (18) |
| Se1ii—Cu1—Np1iv | 58.79 (2) | Se2vii—Np1—Cu1vii | 88.423 (18) |
| Se1iii—Cu1—Np1iv | 124.26 (3) | Se2—Np1—Cu1vii | 162.568 (18) |
| Se1—Cu1—Np1iv | 117.81 (3) | Se1viii—Np1—Cu1vii | 44.741 (17) |
| Cu1iii—Cu1—Np1iv | 172.48 (5) | Se2ix—Np1—Cu1vii | 43.454 (17) |
| Np1ii—Cu1—Np1iv | 113.38 (2) | Se1—Np1—Cu1vii | 88.717 (17) |
| Se2i—Cu1—Np1v | 57.06 (2) | Se1v—Np1—Cu1vii | 123.660 (17) |
| Se1ii—Cu1—Np1v | 160.72 (3) | Cu1viii—Np1—Cu1vii | 45.22 (2) |
| Se1iii—Cu1—Np1v | 56.76 (2) | Cu1x—Np1—Cu1vii | 66.861 (13) |
| Se1—Cu1—Np1v | 95.83 (3) | Cu1viii—Se1—Cu1iii | 99.74 (3) |
| Cu1iii—Cu1—Np1v | 65.14 (3) | Cu1viii—Se1—Cu1 | 148.28 (3) |
| Np1ii—Cu1—Np1v | 134.78 (2) | Cu1iii—Se1—Cu1 | 62.43 (3) |
| Np1iv—Cu1—Np1v | 111.51 (2) | Cu1viii—Se1—Np1ii | 76.53 (2) |
| Se2vi—Np1—Se2vii | 122.772 (13) | Cu1iii—Se1—Np1ii | 78.50 (2) |
| Se2vi—Np1—Se2 | 91.915 (16) | Cu1—Se1—Np1ii | 74.31 (2) |
| Se2vii—Np1—Se2 | 74.152 (12) | Cu1viii—Se1—Np1 | 75.95 (2) |
| Se2vi—Np1—Se1viii | 89.408 (17) | Cu1iii—Se1—Np1 | 81.29 (2) |
| Se2vii—Np1—Se1viii | 128.634 (17) | Cu1—Se1—Np1 | 122.48 (3) |
| Se2—Np1—Se1viii | 150.258 (17) | Np1ii—Se1—Np1 | 142.27 (2) |
| Se2vi—Np1—Se2ix | 74.394 (9) | Cu1viii—Se1—Np1vii | 79.17 (2) |
| Se2vii—Np1—Se2ix | 72.516 (18) | Cu1iii—Se1—Np1vii | 178.90 (3) |
| Se2—Np1—Se2ix | 127.853 (11) | Cu1—Se1—Np1vii | 118.47 (3) |
| Se1viii—Np1—Se2ix | 80.988 (16) | Np1ii—Se1—Np1vii | 101.074 (17) |
| Se2vi—Np1—Se1 | 160.988 (17) | Np1—Se1—Np1vii | 98.541 (17) |
| Se2vii—Np1—Se1 | 74.905 (16) | Cu1i—Se2—Np1vi | 77.53 (2) |
| Se2—Np1—Se1 | 86.315 (17) | Cu1i—Se2—Np1v | 109.10 (3) |
| Se1viii—Np1—Se1 | 82.962 (10) | Np1vi—Se2—Np1v | 100.770 (17) |
| Se2ix—Np1—Se1 | 121.133 (17) | Cu1i—Se2—Np1 | 146.34 (3) |
| Se2vi—Np1—Se1v | 76.958 (16) | Np1vi—Se2—Np1 | 88.085 (16) |
| Se2vii—Np1—Se1v | 141.588 (16) | Np1v—Se2—Np1 | 103.371 (19) |
| Se2—Np1—Se1v | 72.469 (16) | Cu1i—Se2—Np1xi | 79.48 (2) |
| Se1viii—Np1—Se1v | 78.926 (17) | Np1vi—Se2—Np1xi | 148.12 (2) |
| Se2ix—Np1—Se1v | 144.944 (16) | Np1v—Se2—Np1xi | 107.484 (18) |
| Se1—Np1—Se1v | 84.479 (14) | Np1—Se2—Np1xi | 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. |
Table 1
Selected geometric parameters (Å, °) top| Cu1—Se2i | 2.4409 (9) | Np1—Se2 | 2.9743 (6) |
| Cu1—Se1ii | 2.4490 (9) | Np1—Se1vi | 2.9784 (6) |
| Cu1—Se1iii | 2.5066 (9) | Np1—Se2vii | 2.9785 (6) |
| Cu1—Se1 | 2.5899 (9) | Np1—Se1 | 2.9950 (6) |
| Np1—Se2iv | 2.9330 (6) | Np1—Se1viii | 3.1419 (6) |
| Np1—Se2v | 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. |
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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![[Figure 1]](./wm2219fig1thm.gif)
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.