inorganic compounds
Dicaesium pentacyanotricuprate(I), Cs2Cu3(CN)5
aSchool of Chemistry, University of Reading, Reading, Berkshire RG6 6AD, England
*Correspondence e-mail: a.m.chippindale@rdg.ac.uk
Cs2Cu3(CN)5 has a layered structure consisting of [Cu3(CN)5]2− sheets stacked in an ABAB fashion along the c axis, with Cs+ cations lying between the sheets. The sheets are generated by linking –(CuCN)– chains, in which the C≡N groups are ordered, via [Cu(CN)3]2− units. The two bridging cyanide groups of each [Cu(CN)3]2− unit show partial `head-to-tail' disorder of C and N, whilst the third C≡N group is terminal and ordered with C bonded to Cu.
Comment
Copper(I) cyanide frameworks, like those of other transition-metal M(CN)x structural building blocks. For copper(I), a range of potential building blocks are known, including simple species, such as linear [Cu(CN)2]−, trigonal [Cu(CN)3]2− and tetrahedral [Cu(CN)4]3− units, and larger fragments, such as –(CuCN)– chains. These units have well defined geometries and can be assembled to form new solids by combining with themselves, in association with charge-balancing species where necessary, or with other complex metal ions or organic species, e.g. Lewis bases such as to generate one-, two- and three-dimensional frameworks.
can be viewed as constructed fromThe present work is a continuation of our investigations of copper(I) cyanide materials prepared in the presence of alkali-metal cations (Chippindale et al., 2004; Pohl et al., 2006). Cs2Cu3(CN)5 reported here has the same layer structure as K2Cu3(CN)5, prepared previously in acetonitrile under solvothermal conditions (Pohl et al., 2006).
The layer structure of Cs2Cu3(CN)5 can be described in terms of –(Cu2CN)– chains running along the b axis and linked through bridging [Cu1(CN)3]2− units to generate a network of (CuCN)8 rings within the layers. The layers stack in an ABAB fashion along the c axis (Fig. 1). Cs+ cations lie between the layers bonded to 12 cyanide groups, with Cs—C/N distances in the range 3.11 (2)–3.58 (3) Å.
There are two crystallographically distinct Cu atoms, both of which have approximately trigonal-planar coordination (Fig. 2). Atom Cu1, on a special position of 2, is bonded to two equivalent bridging cyanide groups, Z3≡Z4, through the Z4 ends of the groups. The Z3≡Z4 unit shows partial `head-to-tail' disorder, as determined by with Z3 having occupancy 0.78 (4) for C3 and 0.22 (4) for N3 and Z4 having occupancy 0.22 (4) for C4 and 0.78 (4) for N4. The coordination around Cu1 is completed by a third cyanide group, C1≡N1, bonded as a terminal group to Cu1 through C1. Atom Cu2, sited on a general position, bonds directly to C2, N2 and Z3 and is also approximately trigonal planar, although the geometry around Cu2 is less regular than that found for Cu1. The of site occupancies for the cyanide group C2≡N2 indicates that the C and N atoms are fully ordered. The greater deviation from linearity of the Cu2—N2≡C2 angle compared with the Cu2—C2≡N2 angle in Cu2—C2≡N2—Cu2iii (symmetry code as in Table 1) confirms this assignment: strong π–π interactions between a metal and the C end of a cyanide usually result in a smaller deviation from linearity of the M—C—N angle than the M′—N—C angle (Vahrenkamp et al., 1997).
Experimental
Crystals of Cs2Cu3(CN)5 were prepared at 293 K. KCN (1.30 g, 20.0 mmol), CuCN (0.46 g, 5.1 mmol) and CsNO3 (1.94 g, 10.0 mmol) were dissolved in deionized water (15 ml) to form a colourless solution. On addition of 1 M H2SO4 (7.4 ml), a white precipitate formed immediately. This was subsequently identified as Cs2Cu3(CN)5 using powder X-ray diffraction. The precipitate was allowed to stand in the solution at room temperature, and after three weeks colourless rectangular blocks of Cs2Cu3(CN)5 had grown. The crystals were filtered off, washed with water and allowed to dry in the air. A powder X-ray diffraction pattern of the ground crystals confirmed that the product was monophasic. IR data (Nujol mull): ν(C≡N) 2140 (m), 2104 (s), 2098 (s) cm−1.
Crystal data
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The orientations of the three distinct C≡N groups were investigated as follows. Each C≡N was modelled as Zx≡Zy with starting values for the occupancies of both Zx and Zy set to (0.5 C + 0.5 N). The site occupancies were then refined subject to the constraints that the total occupancy for each site was 1.00 and the displacement parameters of C and N on the same site were equal. Cyanide groups C1≡N1 and C2≡N2 were found to be fully ordered and the occupancies of these groups were fixed in subsequent refinements. The occupancies in the remaining bridging Z3≡Z4 group have refined values for Z3 of 0.78 (4) for C3 and 0.22 (4) for N3, and for Z4 of 0.22 (4) for C4 and 0.78 (4) for N4.
Data collection: CrysAlisPro, (Oxford Diffraction, 2006); cell CrysAlisPro; data reduction: CrysAlisPro; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.
Supporting information
https://doi.org/10.1107/S1600536806020484/br2008sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536806020484/br2008Isup2.hkl
Data collection: CrysAlis PRO, (Oxford Diffraction, 2006); cell
CrysAlis PRO; data reduction: CrysAlis PRO; program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: CAMERON (Watkin et al., 1996); software used to prepare material for publication: CRYSTALS.Cs2Cu3(CN)5 | F(000) = 1048 |
Mr = 586.54 | Dx = 3.221 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 1341 reflections |
a = 17.8156 (9) Å | θ = 3–28° |
b = 8.0962 (15) Å | µ = 11.13 mm−1 |
c = 8.3890 (8) Å | T = 150 K |
β = 91.771 (8)° | Block, colourless |
V = 1209.4 (3) Å3 | 0.24 × 0.12 × 0.08 mm |
Z = 4 |
Oxford Diffraction Gemini S Ultra diffractometer | 1123 reflections with I > 3σ(I) |
Graphite monochromator | Rint = 0.021 |
ω/2θ scans | θmax = 28.5°, θmin = 2.8° |
Absorption correction: multi-scan (ABSPACK; Oxford Diffraction, 2006) | h = −23→23 |
Tmin = 0.21, Tmax = 0.41 | k = −10→10 |
9301 measured reflections | l = −11→10 |
1343 independent reflections |
Refinement on F | 0 restraints |
Least-squares matrix: full | Primary atom site location: structure-invariant direct methods |
R[F2 > 2σ(F2)] = 0.017 | Modified Chebychev polynomial (Watkin, 1994; Prince, 1982) with coefficients: 16.0 -11.9 11.5 1.63 |
wR(F2) = 0.020 | (Δ/σ)max = 0.003 |
S = 1.08 | Δρmax = 0.88 e Å−3 |
1123 reflections | Δρmin = −0.70 e Å−3 |
71 parameters |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
Cu1 | 0.5 | 0.07756 (6) | 0.25 | 0.0271 | |
Cu2 | 0.69499 (2) | −0.16705 (4) | 0.61633 (5) | 0.0241 | |
Cs1 | 0.61328 (1) | 0.31446 (2) | 0.58176 (2) | 0.0224 | |
N1 | 0.5000 | 0.4562 (5) | 0.25 | 0.0292 | |
N2 | 0.74397 (14) | −0.4701 (3) | 0.8103 (3) | 0.0261 | |
N3 | 0.61620 (16) | −0.1048 (3) | 0.4678 (3) | 0.0237 | 0.22 (4) |
N4 | 0.57032 (15) | −0.0526 (3) | 0.3812 (3) | 0.0263 | 0.78 (4) |
C1 | 0.5000 | 0.3140 (5) | 0.25 | 0.0216 | |
C2 | 0.72384 (16) | −0.3592 (4) | 0.7357 (4) | 0.0235 | |
C3 | 0.61620 (16) | −0.1048 (3) | 0.4678 (3) | 0.0237 | 0.78 (4) |
C4 | 0.57032 (15) | −0.0526 (3) | 0.3812 (3) | 0.0263 | 0.22 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cu1 | 0.0299 (3) | 0.0204 (2) | 0.0305 (3) | 0.0000 | −0.0086 (2) | 0.0000 |
Cu2 | 0.02514 (18) | 0.01995 (18) | 0.0268 (2) | 0.00171 (14) | −0.00494 (14) | 0.00083 (13) |
Cs1 | 0.02314 (11) | 0.02181 (11) | 0.02193 (11) | 0.00201 (6) | −0.00309 (6) | −0.00117 (6) |
N1 | 0.0277 (18) | 0.0277 (19) | 0.0324 (19) | 0.0000 | 0.0043 (15) | 0.0000 |
N2 | 0.0244 (12) | 0.0211 (12) | 0.0325 (13) | −0.0019 (10) | −0.0032 (10) | −0.0004 (10) |
N3 | 0.0247 (14) | 0.0215 (13) | 0.0250 (15) | 0.0015 (11) | 0.0019 (11) | −0.0025 (10) |
N4 | 0.0273 (13) | 0.0240 (12) | 0.0275 (13) | 0.0039 (11) | −0.0021 (11) | −0.0009 (11) |
C1 | 0.0188 (17) | 0.024 (2) | 0.0221 (19) | 0.0000 | −0.0046 (14) | 0.0000 |
C2 | 0.0206 (13) | 0.0196 (12) | 0.0300 (15) | −0.0009 (11) | −0.0048 (10) | −0.0015 (11) |
C3 | 0.0247 (14) | 0.0215 (13) | 0.0250 (15) | 0.0015 (11) | 0.0019 (11) | −0.0025 (10) |
C4 | 0.0273 (13) | 0.0240 (12) | 0.0275 (13) | 0.0039 (11) | −0.0021 (11) | −0.0009 (11) |
Cu1—C1 | 1.915 (4) | Cu2—Z3 | 1.916 (3) |
Cu1—Z4 | 1.951 (3) | N1—C1 | 1.151 (6) |
Cu1—Z4i | 1.951 (3) | N2—C2 | 1.145 (4) |
Cu2—C2 | 1.912 (3) | Z3—Z4 | 1.156 (4) |
Cu2—N2ii | 2.016 (3) | ||
Z4i—Cu1—Z4 | 114.60 (16) | Cu2iii—N2—C2 | 160.7 (3) |
Z4i—Cu1—C1 | 122.70 (8) | Cu2—Z3—Z4 | 173.8 (3) |
Z4—Cu1—C1 | 122.70 (8) | Cu1—Z4—Z3 | 168.7 (3) |
N2ii—Cu2—Z3 | 111.60 (11) | N1—C1—Cu1 | 180 |
N2ii—Cu2—C2 | 110.50 (12) | N2—C2—Cu2 | 176.7 (3) |
C2—Cu2—Z3 | 137.26 (12) |
Symmetry codes: (i) −x+1, y, −z+1/2; (ii) −x+3/2, y+1/2, −z+3/2; (iii) −x+3/2, y−1/2, −z+3/2. |
Acknowledgements
The authors thank the EPSRC for grants in support of a single-crystal CCD diffractometer and a Studentship for AHP. AMC thanks the Leverhulme Trust for a Research Fellowship.
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