Cu4.35Cd1.65As16: the first polyarsenic compound in the Cu–Cd–As system

Osters, O.; Nilges, T.

doi:10.1107/S1600536811042127

inorganic compounds

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Volume 67| Part 11| November 2011| Page i62

doi:10.1107/S1600536811042127

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Cu_4.35Cd_1.65As₁₆: the first polyarsenic compound in the Cu–Cd–As system

Oliver Osters ^a and Tom Nilges ^a ^*

^aTechnische Universität München, Department Chemie, Lichtenbergstrasse 4, 85747 Garching bei München, Germany
^*Correspondence e-mail: tom.nilges@lrz.tum.de

(Received 30 September 2011; accepted 12 October 2011; online 22 October 2011)

The first polyarsenic compound in the Cu–Cd–As system was obtained by solid-state reaction of the elements and has a refined composition of Cu_4.35 (2)Cd_1.65 (2)As₁₆ (tetracopper dicadmium hexadecaarsenide). It adopts the Cu₅InP₁₆ structure type. The asymmetric unit consists of one Cu site, a split Cu/Cd site and four As sites. The polyanionic structure can be described as being composed of As₆ rings in chair conformations which are connected in the 1-, 2-, 4- and 5-positions. The resulting layers evolve along the c axis perpendicular to the ab plane. One Cu atom exhibits site symmetry 2 and is tetrahedrally coordinated by four As atoms. The other Cu atom, representing the split site, and the corresponding Cd atom have different coordination spheres. While the Cu atom is tetrahedrally coordinated by four As atoms, the Cd atom has a [3 + 1] coordination with a considerably longer Cd—As distance.

Related literature

For Cu₅InP₁₆, see: Lange et al. (2008 ). For related polyphosphides, see: Pöttgen et al. (2006 ). For polyarsenides, see: Bauhofer et al. (1981 ); Jeitschko et al. (2000 ); Emmerling & Röhr (2002 ); Emmerling et al. (2004 ); Hönle et al. (2002 ). For binary Cu–Cd phases, see: Brandon et al. (1974 ); Kreiner & Schaepers (1997 ); von Heidenstamm et al. (1968 ). For related structures, see: Mansmann (1965 ); Clark & Range (1976 ). For crystallographic background, see: Becker & Coppens (1974 ).

Experimental

Crystal data

Cu_4.35Cd_1.65As₁₆
M_r = 1660.8
Monoclinic, C 2/c
a = 11.8324 (6) Å
b = 10.4423 (4) Å
c = 8.0903 (4) Å
β = 110.480 (4)°
V = 936.44 (8) Å³
Z = 2
Mo Kα radiation
μ = 34.73 mm⁻¹
T = 293 K
0.030 × 0.020 × 0.004 mm

Data collection

Stoe IPDS 2T diffractometer
Absorption correction: numerical (X-AREA; Stoe & Cie, 2011 ) T_min = 0.205, T_max = 0.785
12811 measured reflections
1268 independent reflections
1113 reflections with I > 3σ(I)
R_int = 0.053

Refinement

R[F² > 2σ(F²)] = 0.036
wR(F²) = 0.072
S = 1.83
1268 reflections
56 parameters
Δρ_max = 1.50 e Å⁻³
Δρ_min = −1.67 e Å⁻³

Table 1
Selected bond lengths (Å)

Cu1—As1	2.4254 (9)
Cu1—As3	2.3931 (9)
Cu2—As2	2.516 (5)
Cu2—As3	2.501 (5)
Cu2—As4ⁱ	2.589 (6)
Cu2—As4ⁱⁱ	2.524 (7)
Cd2—As2	2.856 (5)
Cd2—As3	2.516 (5)
Cd2—As4ⁱ	2.475 (5)
Cd2—As4ⁱⁱ	2.569 (6)
Symmetry codes: (i) $[-x-{\script{1\over 2}}, y-{\script{1\over 2}}, -z-{\script{1\over 2}}]$ ; (ii) $[-x-{\script{1\over 2}}, -y+{\script{1\over 2}}, -z]$ .

Data collection: X-AREA (Stoe & Cie, 2011); cell refinement: X-AREA; data reduction: X-AREA; program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007 ) embedded in JANA2006 (Petřiček et al., 2006 ); program(s) used to refine structure: JANA2006; molecular graphics: DIAMOND (Brandenburg & Putz, 2005 ); software used to prepare material for publication: publCIF (Westrip, 2010 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811042127/wm2539sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811042127/wm2539Isup2.hkl

checkCIF report

Comment top

Besides the plethora of known polyphosphides (Pöttgen et al., 2006) only few polyarsenides are known up to date (Bauhofer et al., 1981; Jeitschko et al., 2000; Emmerling & Röhr, 2002; Emmerling et al., 2004; Hönle et al., 2002).

The title compound Cu_4.35 (2)Cd_1.65 (2)As₁₆ is the first representative of a polyarsenide adopting the Cu₅InP₁₆ structure type (Lange et al., 2008). In accordance to the situation in Cu₅InP₁₆ where Cu and In are occupying the same site, a similar behavior is observed for the title compound, but here with a Cu/Cd split position. Mixing of Cu and Cd on one site is a common feature in intermetallic compounds and has been observed for instance for Cd₃Cu₄ (Kreiner & Schaepers, 1997) and Cd₈Cu₅ (von Heidenstamm et al., 1968; Brandon et al., 1974).

Cu—As distances in Cu_4.35 (2)Cd_1.65 (2)As₁₆ range from 2.3931 (9) Å to 2.589 (6) Å and are comparable with the distances of 2.404 (1) Å to 2.590 (1) Å in Cu₃As (Mansmann, 1965). The As—As distances in Cu_4.35 (2)Cd_1.65 (2)As₁₆ are between 2.4242 (8) Å and 2.4644 (10) Å, in good accordance with the As—As distances in NdFe₄As₁₂ (2.428 Å - 2.499 Å) (Jeitschko et al., 2000). Cd—As distances are present between 2.475 (5) Å and 2.856 (5) Å which is consistent with values found for CdAs (2.473 (2) Å - 2.868 (2) Å) (Clark & Range, 1976).

Related literature top

For Cu₅InP₁₆, see: Lange et al. (2008). For related polyphosphides, see: Pöttgen et al. (2006). For polyarsenides, see: Bauhofer et al. (1981); Jeitschko et al. (2000); Emmerling & Röhr (2002); Emmerling et al. (2004); Hönle et al. (2002). For binary Cu–Cd phases, see: Brandon et al. (1974); Kreiner & Schaepers (1997); von Heidenstamm et al. (1968). For related structures, see: Mansmann (1965); Clark & Range (1976). For crystallographic background, see: Becker & Coppens (1974).

Experimental top

Cu_4.35 (2)Cd_1.65 (2)As₁₆ was prepared by a solid state reaction from the elements Cu (ChemPur, shot, 99.999%), Cd (ChemPur, granules, 99.9999%) and As (ChemPur, pieces, 99.9999%). Arsenic was purified by sublimation in evacuated silica ampoules using a temperature gradient of 573 K to room temperature to separate As₂O₃ from the bulk-As and at 873 K to 573 K to sublimate As directly. The purified As was stored under protection gas atmosphere prior to use. The starting materials were reacted in stoichiometric amounts according the reported composition at 753 K for 7 days followed by a homogenization step by grinding. The procedure was repeated two times to finalize the formation of the title compound. Single crystals of suitable size could be separated from the bulk phase.

Computing details top

Data collection: X-AREA (Stoe & Cie, 2011); cell refinement: X-AREA (Stoe & Cie, 2011); data reduction: X-AREA (Stoe & Cie, 2011); program(s) used to solve structure: Superflip (Palatinus & Chapuis, 2007) embedded in JANA2006 (Petřiček et al., 2006); program(s) used to refine structure: JANA2006 (Petřiček et al., 2006); molecular graphics: DIAMOND (Brandenburg & Putz, 2005); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top

Fig. 1. Crystal structure of Cu_4.35 (2)Cd_1.65 (2)As₁₆, viewed along the c axis. Displacement ellipsoids are shown at the 90% probability level.

tetracopper dicadmium hexadecaarsenide top

Crystal data top

Cu_4.35Cd_1.65As₁₆	F(000) = 1467
M_r = 1660.8	D_x = 5.888 Mg m⁻³
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 12419 reflections
a = 11.8324 (6) Å	θ = 3.7–29.7°
b = 10.4423 (4) Å	µ = 34.73 mm⁻¹
c = 8.0903 (4) Å	T = 293 K
β = 110.480 (4)°	Plate, black
V = 936.44 (8) Å³	0.03 × 0.02 × 0.004 mm
Z = 2

Data collection top

Stoe IPDS 2T diffractometer	1268 independent reflections
Radiation source: X-ray tube	1113 reflections with I > 3σ(I)
Plane graphite monochromator	R_int = 0.053
Detector resolution: 6.67 pixels mm^-1	θ_max = 29.3°, θ_min = 3.7°
ω scans	h = −16→16
Absorption correction: numerical (X-AREA; Stoe & Cie, 2011)	k = −14→14
T_min = 0.205, T_max = 0.785	l = −11→11
12811 measured reflections

Refinement top

Refinement on F²	6 constraints
R[F² > 2σ(F²)] = 0.036	Weighting scheme based on measured s.u.'s w = 1/[σ²(I) + 0.0004I²]
wR(F²) = 0.072	(Δ/σ)_max = 0.007
S = 1.83	Δρ_max = 1.50 e Å⁻³
1268 reflections	Δρ_min = −1.67 e Å⁻³
56 parameters	Extinction correction: B-C type 1 Gaussian isotropic (Becker & Coppens, 1974)
0 restraints	Extinction coefficient: 0.021 (2)

Crystal data top

Cu_4.35Cd_1.65As₁₆	V = 936.44 (8) Å³
M_r = 1660.8	Z = 2
Monoclinic, C2/c	Mo Kα radiation
a = 11.8324 (6) Å	µ = 34.73 mm⁻¹
b = 10.4423 (4) Å	T = 293 K
c = 8.0903 (4) Å	0.03 × 0.02 × 0.004 mm
β = 110.480 (4)°

Data collection top

Stoe IPDS 2T diffractometer	1268 independent reflections
Absorption correction: numerical (X-AREA; Stoe & Cie, 2011)	1113 reflections with I > 3σ(I)
T_min = 0.205, T_max = 0.785	R_int = 0.053
12811 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.036	56 parameters
wR(F²) = 0.072	0 restraints
S = 1.83	Δρ_max = 1.50 e Å⁻³
1268 reflections	Δρ_min = −1.67 e Å⁻³

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

	x	y	z	U_iso*/U_eq	Occ. (<1)
Cu1	0	0.41450 (10)	0.25	0.0156 (3)
Cu2	−0.0942 (5)	0.1309 (5)	−0.0886 (9)	0.0198 (9)	0.587 (6)
Cd2	−0.0713 (4)	0.1064 (5)	−0.0867 (7)	0.0198 (9)	0.413 (6)
As1	−0.15337 (5)	0.56586 (5)	0.08461 (8)	0.01309 (19)
As2	−0.23875 (5)	0.30964 (6)	−0.22826 (8)	0.01406 (19)
As3	0.07426 (6)	0.27955 (6)	0.07165 (9)	0.0171 (2)
As4	−0.33882 (6)	0.48506 (7)	−0.13511 (9)	0.0232 (2)

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cu1	0.0132 (5)	0.0182 (5)	0.0157 (5)	0	0.0055 (4)	0
Cu2	0.0171 (16)	0.0237 (16)	0.0194 (4)	−0.0067 (9)	0.0076 (10)	−0.0062 (10)
Cd2	0.0171 (16)	0.0237 (16)	0.0194 (4)	−0.0067 (9)	0.0076 (10)	−0.0062 (10)
As1	0.0115 (3)	0.0139 (3)	0.0130 (3)	−0.0003 (2)	0.0033 (2)	0.0001 (2)
As2	0.0126 (3)	0.0143 (3)	0.0143 (3)	0.0015 (2)	0.0034 (2)	0.0016 (2)
As3	0.0153 (3)	0.0172 (3)	0.0198 (3)	0.0025 (2)	0.0074 (2)	0.0046 (2)
As4	0.0128 (3)	0.0296 (3)	0.0265 (4)	−0.0031 (3)	0.0061 (3)	−0.0155 (3)

Geometric parameters (Å, º) top

Cu1—As1	2.4254 (9)	Cd2—As2	2.856 (5)
Cu1—As1ⁱ	2.4254 (9)	Cd2—As3	2.516 (5)
Cu1—As3	2.3931 (9)	Cd2—As4ⁱⁱ	2.475 (5)
Cu1—As3ⁱ	2.3931 (9)	Cd2—As4ⁱⁱⁱ	2.569 (6)
Cu2—Cd2	0.370 (8)	As1—As2^v	2.4644 (10)
Cu2—As2	2.516 (5)	As1—As3^vi	2.4307 (10)
Cu2—As3	2.501 (5)	As1—As4	2.4408 (8)
Cu2—As4ⁱⁱ	2.589 (6)	As2—As3^vii	2.4242 (8)
Cu2—As4ⁱⁱⁱ	2.524 (7)	As2—As4	2.4392 (10)
Cd2—Cd2^iv	2.845 (7)

As1—Cu1—As1ⁱ	98.67 (4)	As3^vi—As1—As4	105.22 (3)
As1—Cu1—As3	114.38 (2)	Cu2—As2—Cd2	3.1 (2)
As1—Cu1—As3ⁱ	110.77 (2)	Cu2—As2—As1^viii	107.87 (17)
As1ⁱ—Cu1—As3	110.77 (2)	Cu2—As2—As3^vii	109.44 (12)
As1ⁱ—Cu1—As3ⁱ	114.38 (2)	Cu2—As2—As4	138.19 (17)
As3—Cu1—As3ⁱ	107.85 (4)	Cd2—As2—As1^viii	105.21 (13)
Cd2—Cu2—As2	155.1 (16)	Cd2—As2—As3^vii	108.99 (10)
Cd2—Cu2—As3	88.1 (11)	Cd2—As2—As4	141.07 (12)
Cd2—Cu2—As4ⁱⁱ	68.2 (12)	As1^viii—As2—As3^vii	105.49 (3)
Cd2—Cu2—As4ⁱⁱⁱ	92.7 (15)	As1^viii—As2—As4	98.12 (3)
As2—Cu2—As3	93.76 (19)	As3^vii—As2—As4	93.81 (3)
As2—Cu2—As4ⁱⁱ	95.40 (19)	Cu1—As3—Cu2	106.49 (17)
As2—Cu2—As4ⁱⁱⁱ	110.1 (3)	Cu1—As3—Cd2	113.57 (14)
As3—Cu2—As4ⁱⁱ	139.5 (3)	Cu1—As3—As1^vi	102.24 (3)
As3—Cu2—As4ⁱⁱⁱ	108.6 (2)	Cu1—As3—As2^ix	105.39 (3)
As4ⁱⁱ—Cu2—As4ⁱⁱⁱ	105.0 (2)	Cu2—As3—Cd2	8.44 (18)
Cu2—Cd2—Cd2^iv	149.6 (16)	Cu2—As3—As1^vi	121.65 (17)
Cu2—Cd2—As2	21.8 (14)	Cu2—As3—As2^ix	118.91 (13)
Cu2—Cd2—As3	83.5 (11)	Cd2—As3—As1^vi	122.14 (14)
Cu2—Cd2—As4ⁱⁱ	103.9 (12)	Cd2—As3—As2^ix	111.47 (11)
Cu2—Cd2—As4ⁱⁱⁱ	79.0 (15)	As1^vi—As3—As2^ix	100.07 (3)
Cd2^iv—Cd2—As2	170.7 (3)	Cu2^x—As4—Cu2ⁱⁱⁱ	145.40 (19)
Cd2^iv—Cd2—As3	97.37 (17)	Cu2^x—As4—Cd2^x	7.97 (17)
Cd2^iv—Cd2—As4ⁱⁱ	92.32 (19)	Cu2^x—As4—Cd2ⁱⁱⁱ	138.18 (18)
Cd2^iv—Cd2—As4ⁱⁱⁱ	71.60 (19)	Cu2^x—As4—As1	110.54 (12)
As2—Cd2—As3	85.72 (15)	Cu2^x—As4—As2	102.12 (16)
As2—Cd2—As4ⁱⁱ	89.91 (14)	Cu2ⁱⁱⁱ—As4—Cd2^x	138.99 (18)
As2—Cd2—As4ⁱⁱⁱ	99.07 (19)	Cu2ⁱⁱⁱ—As4—Cd2ⁱⁱⁱ	8.26 (17)
As3—Cd2—As4ⁱⁱ	146.1 (3)	Cu2ⁱⁱⁱ—As4—As1	94.09 (12)
As3—Cd2—As4ⁱⁱⁱ	106.8 (2)	Cu2ⁱⁱⁱ—As4—As2	99.75 (14)
As4ⁱⁱ—Cd2—As4ⁱⁱⁱ	107.07 (19)	Cd2^x—As4—Cd2ⁱⁱⁱ	132.39 (17)
Cu1—As1—As2^v	113.16 (3)	Cd2^x—As4—As1	118.43 (12)
Cu1—As1—As3^vi	111.70 (3)	Cd2^x—As4—As2	101.77 (14)
Cu1—As1—As4	119.01 (3)	Cd2ⁱⁱⁱ—As4—As1	96.10 (10)
As2^v—As1—As3^vi	106.52 (3)	Cd2ⁱⁱⁱ—As4—As2	107.52 (12)
As2^v—As1—As4	99.93 (3)	As1—As4—As2	94.29 (3)

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

Experimental details

Crystal data
Chemical formula	Cu_4.35Cd_1.65As₁₆
M_r	1660.8
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	293
a, b, c (Å)	11.8324 (6), 10.4423 (4), 8.0903 (4)
β (°)	110.480 (4)
V (Å³)	936.44 (8)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	34.73
Crystal size (mm)	0.03 × 0.02 × 0.004

Data collection
Diffractometer	Stoe IPDS 2T diffractometer
Absorption correction	Numerical (X-AREA; Stoe & Cie, 2011)
T_min, T_max	0.205, 0.785
No. of measured, independent and observed [I > 3σ(I)] reflections	12811, 1268, 1113
R_int	0.053
(sin θ/λ)_max (Å⁻¹)	0.687

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.072, 1.83
No. of reflections	1268
No. of parameters	56
Δρ_max, Δρ_min (e Å⁻³)	1.50, −1.67

Computer programs: X-AREA (Stoe & Cie, 2011), Superflip (Palatinus & Chapuis, 2007) embedded in JANA2006 (Petřiček et al., 2006), JANA2006 (Petřiček et al., 2006), DIAMOND (Brandenburg & Putz, 2005), publCIF (Westrip, 2010).

Selected bond lengths (Å) top

Cu1—As1	2.4254 (9)	Cu2—As4ⁱⁱ	2.524 (7)
Cu1—As3	2.3931 (9)	Cd2—As2	2.856 (5)
Cu2—As2	2.516 (5)	Cd2—As3	2.516 (5)
Cu2—As3	2.501 (5)	Cd2—As4ⁱ	2.475 (5)
Cu2—As4ⁱ	2.589 (6)	Cd2—As4ⁱⁱ	2.569 (6)

Symmetry codes: (i) −x−1/2, y−1/2, −z−1/2; (ii) −x−1/2, −y+1/2, −z.

Acknowledgements

The authors thank the German Science Foundation (DFG) for the kind support of this project within the SPP 1415.

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