inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890
Volume 64| Part 2| February 2008| Pages i13-i14

The dehydrated copper silicate Na2[Cu2Si4O11]: a three-dimensional microporous framework with a linear Si—O—Si linkage

aDepartment of Chemistry, University of Aveiro, CICECO, 3810-193 Aveiro, Portugal
*Correspondence e-mail: filipe.paz@ua.pt

(Received 28 November 2007; accepted 15 January 2008; online 23 January 2008)

The structure of the title dehydrated copper silicate, disodium dicopper undeca­oxide tetra­silicate, Na2(Cu2O11Si4), was determined by single-crystal X-ray diffraction from a non-merohedral twin. It exhibits an effective three-dimensional microporous framework with the major channels, in which the Na+ cations are placed, running along the a-axis direction and smaller channels observed along the b-axis direction. The structure is unusual in that it contains a symmetry-constrained Si—O—Si angle of 180°. The Cu centre is coordinated to five O atoms, exhibiting a slightly distorted square-pyramidal coordination geometry. The Na cation is interacting with five neighbouring O atoms, exhibiting an uncharacteristic coordination environment.

Related literature

For related literature, see: Brandão et al. (2005[Brandão, P., Almeida Paz, F. A. & Rocha, J. (2005). Chem. Commun. pp. 171-173.]); Haile & Wuensch (2000[Haile, S. M. & Wuensch, B. J. (2000). Acta Cryst. B56, 773-779.]); Liebau (1985[Liebau, F. (1985). Structural Chemistry of Silicates: Structure, Bonding, and Classification, pp. 14-29. Berlin: Springer-Verlag.]); Rocha & Anderson (2000[Rocha, J. & Anderson, M. W. (2000). Eur. J. Inorg. Chem. pp. 801-818.]); Rocha & Lin (2005[Rocha, J. & Lin, Z. (2005). Reviews in Mineralogy and Geochemistry, Vol. 57, edited by G. Ferraris & S. Merlino, ch. 6, pp. 173-201. Washington, DC: Mineralogical Society of America, Geochemical Society.]); dos Santos et al. (2005[Santos, A. M. dos, Amaral, V. S., Brandão, P., Almeida Paz, F. A., Rocha, J., Ferreira, L. P., Godinho, M., Volkova, O. & Vasiliev, A. (2005). Phys. Rev. B, 72, Art. No. 092403.]); Ananias et al. (2001[Ananias, D., Ferreira, A., Rocha, J., Ferreira, P., Rainho, J. P., Morais, C. & Carlos, L. D. (2001). J. Am. Chem. Soc. 123, 5735-5742.], 2006[Ananias, D., Almeida Paz, F. A., Carlos, L. D., Geraldes, C. F. G. C. & Rocha, J. (2006). Angew. Chem. Int. Ed. 45, 7938-7942.]); Anderson et al. (1994[Anderson, M. W., Terasaki, O., Ohsuna, T., Philippou, A., Mackay, S. P., Ferreira, A., Rocha, J. & Lidin, S. (1994). Nature (London), 367, 347-351.]); Ferreira et al. (2003[Ferreira, A., Ananias, D., Carlos, L. D., Morais, C. & Rocha, J. (2003). J. Am. Chem. Soc. 125, 14573-14579.]).

[Scheme 1]

Experimental

Crystal data
  • Na2(Cu2O11Si4)

  • Mr = 461.44

  • Triclinic, [P \overline 1]

  • a = 5.190 (2) Å

  • b = 6.299 (3) Å

  • c = 8.196 (4) Å

  • α = 96.390 (7)°

  • β = 97.281 (7)°

  • γ = 100.461 (7)°

  • V = 258.9 (2) Å3

  • Z = 1

  • Mo Kα radiation

  • μ = 4.71 mm−1

  • T = 298 (2) K

  • 0.28 × 0.08 × 0.04 mm

Data collection
  • Bruker SMART CCD 1000 diffractometer

  • Absorption correction: multi-scan (TWINABS; Sheldrick, 2002[Sheldrick, G. M. (2002). TWINABS. Version 1.05. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.627, Tmax = 0.834

  • 1587 measured reflections

  • 1043 independent reflections

  • 782 reflections with I > 2σ(I)

  • Rint = 0.042

Refinement
  • R[F2 > 2σ(F2)] = 0.042

  • wR(F2) = 0.119

  • S = 1.01

  • 1043 reflections

  • 88 parameters

  • Δρmax = 1.40 e Å−3

  • Δρmin = −1.58 e Å−3

Table 1
Selected bond lengths (Å)

Cu1—O5i 1.909 (3)
Cu1—O2 1.950 (4)
Cu1—O6ii 1.970 (4)
Cu1—O6 1.974 (3)
Cu1—O2iii 2.316 (4)
Symmetry codes: (i) x, y-1, z; (ii) -x+1, -y, -z+2; (iii) -x+2, -y, -z+2.

Data collection: SMART (Bruker, 1998[Bruker (1998). SMART. Version 5.054. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SMART; data reduction: SAINT-Plus (Bruker, 2003[Bruker (2003). SAINT-Plus. Version 6.45A. Bruker AXS Inc., Madison, Wisconsin, USA.]); program(s) used to solve structure: SIR92 (Altomare et al., 1993[Altomare, A., Cascarano, G., Giacovazzo, C. & Guagliardi, A. (1993). J. Appl. Cryst. 26, 343-350.]); program(s) used to refine structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 2007[Brandenburg, K. (2007). DIAMOND. Version 3.1e. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

Molecular sieves containing metal cations with a range of coordination geometries have been extensively studied due to their novel topologies, interesting chemical properties and potential aplications in optoelectronics, batteries, magnetic materials and sensors (besides the traditional applications of zeolites) (Rocha & Anderson, 2000; Rocha & Lin, 2005). In the last decade, we have been interested in the synthesis and structural characterization of novel open-frameworks containing Si and metal cations (such as Ti, V, Cr, Nb, Zr and Sn) in tetrahedral and (more commonly) octahedral coordination environments, and lanthanide silicates exhibiting interesting photoluminescence properties (Anderson et al., 1994; Ananias et al., 2001; Ferreira et al., 2003; Ananias et al., 2006). As part of this research line, we prepared and characterized the hydrated copper silicate Na2(Cu2Si4O11).2H2O (Brandão et al., 2005). This compound was dehydrated and the magnetic properties of both hydrated and dehydrated forms were investigated (Santos et al., 2005), however the crystalline structure of the dehydrated compound was not reported. Here we describe the structure of the dehydrated microporous copper silicate, Na2(Cu2Si4O11) (I).

The asymmetric unit of the copper silicate (I) comprises one Cu(II) cation, two corner-shared SiO4 groups and one Na+ counter-cation (Figure 1). The crystallographic unique Cu(II) metal centre is coordinated to five O-atoms from five distinct SiO4 tetrahedral moieties (four basal SiO4 and one apical SiO4), in a geometry resembling a distorted square pyramid for which the apical Cu—O bond is longer than the basal ones (Figure 2a and Table 1).

Adjacent SiO4 tetrahedral moieties are linked along the a direction by corner-shared oxygen atoms (O3 and O4 are shared alternately) leading to the formation of zigzag metallic anionic chains, [(Cu2Si4O11)]2-, in which the Cu···Cu distances alternate between 2.9921 (8) Å (via bridging basal SiO4, green bonds in Fig. 2 b) and 3.1031 (10) Å (via the apical SiO4 tetrahedron, yellow bonds in Fig. 2 b). [(Cu2Si4O11)]2- chains are interconnected via corner-sharing SiO4 tetrahedra through linear interactions Si1–O1–Siiv [angle is 180.0°; symmetry code: (iv) 2 - x, -y, 1 - z] to form infinite layers (Fig. 2c). This linear Si–O–Si interaction is very rare and represents a remarkable structural feature of the copper silicate (I) framework. We note that such occurrence was also recently reported in the lanthanide silicate K3(NdSi7O17) (Haile & Wuensch, 2000). From the evaluation of the structures of several hundred silicates it was concluded that the average of an unstrained Si—O—Si bond angle is ca 139° and that truly linear bonds are energetically unfavorable (Liebau, 1985). In fact, the crystallographically determined values of 180° are more likely to represent a time average rather than the actual value of the bond angle. The bond, at any instant in time, should have an O-atom displaced from its average position such that the instantaneous value of Si—O—Si is less than 180° (Haile & Wuensch, 2000). This structural feature is ultimately reflected in the anisotropic displacement parameters associated with this bridging O-atom. Indeed, the thermal parameters associated with this atom are unusually large, with the greatest displacement occurring in the plane perpendicular to the Si1···Si1iv vector (Figure 2c).

As observed for the chains, adjacent layers are also interconnected via corner-sharing SiO4 tetrahedra generating a three-dimensional microporous framework with the major channels running along the a direction, formed by eight-membered rings and having a cross-section of ca 7.5 × 4.3 Å (Figure 3a). Interestingly, the Na+ cations are located within the channels but are remarkably close to the previously described layers, creating an effective porous copper framework (Figure 3a). In addition, remarkably large channels are also observed along the b direction, which are formed by six-membered rings and display a cros-section of ca 5.2 × 4.6 Å (Figure 3 b).

Related literature top

For related literature, see: Brandão et al. (2005); Haile & Wuensch (2000); Liebau (1985); Rocha & Anderson (2000); Rocha & Lin (2005); dos Santos et al. (2005); Ananias et al. (2001, 2006); Anderson et al. (1994); Ferreira et al. (2003).

Experimental top

Chemicals were purchased from commercial sources and used without further purification. An alkaline solution was prepared by mixing 13.86 g of a sodium silicate solution (Na2O 8 wt%, SiO2 27 wt%), 16.13 g H2O and 4.11 g NaOH, and a second solution was prepared by mixing 17.87 g H2O with 7.60 g of Cu(SO4).15H2O. These two solutions were combined, stirred thoroughly during 2 h and the resulting gel, with a molar composition of CuO: 3.1SiO2: 1.4Na2O: 94.5H2O, was autoclaved for 10 days at 503 K. A crystalline material was obtained [Na2(Cu2Si4O11).2H2O], filtered and treated thermally at 573 K for six hours leads to the removal of the crystallization water molecules.

Refinement top

Even though crystals of the title compound could be indexed with the unit-cell parameters summarized in Table 1, a visual inspection of the centered reflections using RLATT showed the presence of a rotational twin (non-merohedral). A full sphere of reflections was collected and a partial data set was then deconvoluted using CELL_NOW (Sheldrick 2004) into a two-component twin. Data integration was performed by assuming that the second twin domain was identical to the first. The final structural model exhibits a large average U(i,j) tensor, most likely due to the applied twinning correction which ultimately seems to lead to large U3/U1 ratios.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART (Bruker, 1998); data reduction: SAINT-Plus (Bruker, 2003); program(s) used to solve structure: SIR92 (Altomare et al., 1993); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2007); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. Fragment of the crystal structure of the title compound with the atoms represented as thermal displacement ellipsoids drawn at the 50% probability level [Symmetry codes: (i) 2 - x, -y, 2 - z; (ii) x, -1 + y, z; (iii) 1 - x, -y, 2 - z; (iv) 2 - x, 1 - y, 2 - z; (v) x, y, 1 + z; (vi) 1 + x, y, z].
[Figure 2] Fig. 2. (a) Mixed ball-and-stick and polyhedral representation of the coordination environment of the Cu(II) cations and (b) the metallic chain [(Cu2Si4O11)n]2- running along the a direction of the unit cell. (c) Schematic representation of the linear Si—O—Si bond connecting adjacent Si1 centres via the O1 atom. [Symmetry codes: (i) 2 - x, -y, 2 - z; (ii) x, -1 + y, z; (iii) 1 - x, -y, 2 - z; (iv) 2 - x, -y, 1 - z].
[Figure 3] Fig. 3. Perspective views of the crystal packing arrangement along the (a) [100] and (b) [010] directions of unit cell.
disodium dicopper undecaoxide tetrasilicate top
Crystal data top
Na2(Cu2O11Si4)Z = 1
Mr = 461.44F(000) = 224
Triclinic, P1Dx = 2.960 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 5.190 (2) ÅCell parameters from 758 reflections
b = 6.299 (3) Åθ = 8.1–58.1°
c = 8.196 (4) ŵ = 4.71 mm1
α = 96.390 (7)°T = 298 K
β = 97.281 (7)°Plate, black
γ = 100.461 (7)°0.28 × 0.08 × 0.04 mm
V = 258.9 (2) Å3
Data collection top
Bruker SMART CCD 1000
diffractometer
1043 independent reflections
Radiation source: fine-focus sealed tube782 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.042
ω scansθmax = 26.4°, θmin = 3.9°
Absorption correction: multi-scan
(TWINABS; Sheldrick, 2002)
h = 66
Tmin = 0.627, Tmax = 0.834k = 77
1587 measured reflectionsl = 010
Refinement top
Refinement on F20 restraints
Least-squares matrix: fullPrimary atom site location: structure-invariant direct methods
R[F2 > 2σ(F2)] = 0.042Secondary atom site location: difference Fourier map
wR(F2) = 0.119 w = 1/[σ2(Fo2) + (0.0809P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.01(Δ/σ)max < 0.001
1043 reflectionsΔρmax = 1.40 e Å3
88 parametersΔρmin = 1.58 e Å3
Crystal data top
Na2(Cu2O11Si4)γ = 100.461 (7)°
Mr = 461.44V = 258.9 (2) Å3
Triclinic, P1Z = 1
a = 5.190 (2) ÅMo Kα radiation
b = 6.299 (3) ŵ = 4.71 mm1
c = 8.196 (4) ÅT = 298 K
α = 96.390 (7)°0.28 × 0.08 × 0.04 mm
β = 97.281 (7)°
Data collection top
Bruker SMART CCD 1000
diffractometer
1043 independent reflections
Absorption correction: multi-scan
(TWINABS; Sheldrick, 2002)
782 reflections with I > 2σ(I)
Tmin = 0.627, Tmax = 0.834Rint = 0.042
1587 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.04288 parameters
wR(F2) = 0.1190 restraints
S = 1.01Δρmax = 1.40 e Å3
1043 reflectionsΔρmin = 1.58 e Å3
Special details top

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cu10.70666 (10)0.10891 (9)0.93472 (8)0.0096 (3)
Na10.8700 (4)0.3540 (3)1.1990 (3)0.0235 (6)
Si11.0175 (2)0.1358 (2)0.67930 (18)0.0087 (4)
Si20.5954 (3)0.3456 (2)0.80969 (18)0.0089 (4)
O11.00000.00000.50000.0217 (13)
O21.0064 (7)0.0190 (6)0.8196 (5)0.0127 (8)
O30.7804 (6)0.2736 (6)0.6719 (5)0.0126 (8)
O40.2923 (6)0.3209 (5)0.7137 (5)0.0144 (8)
O50.7200 (7)0.5899 (6)0.8873 (5)0.0170 (9)
O60.5974 (6)0.1760 (5)0.9452 (5)0.0107 (8)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0054 (4)0.0083 (4)0.0159 (4)0.0011 (2)0.0051 (2)0.0018 (2)
Na10.0137 (11)0.0161 (12)0.0396 (16)0.0021 (9)0.0072 (10)0.0030 (10)
Si10.0048 (7)0.0096 (7)0.0124 (8)0.0018 (5)0.0034 (5)0.0009 (5)
Si20.0040 (6)0.0078 (7)0.0155 (8)0.0013 (5)0.0042 (5)0.0018 (5)
O10.020 (3)0.024 (3)0.021 (3)0.006 (2)0.007 (2)0.006 (2)
O20.0078 (17)0.0137 (18)0.018 (2)0.0033 (13)0.0040 (14)0.0045 (14)
O30.0057 (16)0.0169 (19)0.018 (2)0.0068 (14)0.0049 (14)0.0018 (14)
O40.0063 (16)0.0140 (18)0.023 (2)0.0017 (14)0.0014 (14)0.0061 (15)
O50.0145 (18)0.0100 (18)0.028 (2)0.0000 (14)0.0129 (16)0.0016 (15)
O60.0082 (16)0.0111 (17)0.016 (2)0.0039 (13)0.0061 (14)0.0050 (14)
Geometric parameters (Å, º) top
Cu1—O5i1.909 (3)Si1—O4iv1.642 (4)
Cu1—O21.950 (4)Si2—O51.583 (4)
Cu1—O6ii1.970 (4)Si2—O61.625 (4)
Cu1—O61.974 (3)Si2—O41.639 (3)
Cu1—O2iii2.316 (4)Si2—O31.650 (4)
Cu1—Cu1ii2.9921 (13)Si2—Cu1ii3.1221 (19)
Cu1—Cu1iii3.1031 (15)O1—Si1v1.5991 (14)
Cu1—Si2ii3.1221 (19)O2—Cu1iii2.316 (4)
Cu1—Si13.1673 (19)O4—Si1vi1.642 (4)
Si1—O21.588 (4)O5—Cu1vii1.909 (3)
Si1—O11.5991 (14)O6—Cu1ii1.970 (4)
Si1—O31.629 (3)
O5i—Cu1—O292.49 (15)O2iii—Cu1—Si1100.98 (10)
O5i—Cu1—O6ii91.91 (15)Cu1ii—Cu1—Si1115.23 (4)
O2—Cu1—O6ii175.60 (13)Cu1iii—Cu1—Si164.33 (4)
O5i—Cu1—O6164.27 (15)Si2ii—Cu1—Si1179.25 (4)
O2—Cu1—O694.42 (14)O2—Si1—O1111.33 (15)
O6ii—Cu1—O681.32 (16)O2—Si1—O3112.6 (2)
O5i—Cu1—O2iii105.60 (16)O1—Si1—O3108.16 (15)
O2—Cu1—O2iii87.05 (15)O2—Si1—O4iv111.48 (19)
O6ii—Cu1—O2iii91.76 (14)O1—Si1—O4iv108.08 (16)
O6—Cu1—O2iii88.87 (14)O3—Si1—O4iv104.92 (18)
O5i—Cu1—Cu1ii131.06 (12)O1—Si1—Cu1115.96 (7)
O2—Cu1—Cu1ii135.03 (10)O3—Si1—Cu184.08 (15)
O6ii—Cu1—Cu1ii40.70 (10)O4iv—Si1—Cu1129.55 (15)
O6—Cu1—Cu1ii40.62 (10)O5—Si2—O6113.2 (2)
O2iii—Cu1—Cu1ii90.41 (9)O5—Si2—O4111.75 (19)
O5i—Cu1—Cu1iii103.18 (12)O6—Si2—O4109.3 (2)
O2—Cu1—Cu1iii48.19 (11)O5—Si2—O3107.1 (2)
O6ii—Cu1—Cu1iii130.50 (11)O6—Si2—O3107.00 (19)
O6—Cu1—Cu1iii91.93 (10)O4—Si2—O3108.15 (19)
O2iii—Cu1—Cu1iii38.86 (9)O5—Si2—Cu1ii109.62 (16)
Cu1ii—Cu1—Cu1iii116.74 (4)O4—Si2—Cu1ii81.61 (15)
O5i—Cu1—Si2ii73.75 (12)O3—Si2—Cu1ii134.72 (14)
O2—Cu1—Si2ii156.11 (11)Si1v—O1—Si1180.0
O6ii—Cu1—Si2ii26.72 (10)Si1—O2—Cu1126.8 (2)
O6—Cu1—Si2ii103.96 (11)Si1—O2—Cu1iii116.29 (18)
O2iii—Cu1—Si2ii78.31 (10)Cu1—O2—Cu1iii92.95 (15)
Cu1ii—Cu1—Si2ii64.59 (4)Si1—O3—Si2132.7 (3)
Cu1iii—Cu1—Si2ii115.04 (5)Si2—O4—Si1vi137.0 (2)
O5i—Cu1—Si1106.73 (13)Si2—O5—Cu1vii152.9 (2)
O2—Cu1—Si123.68 (11)Si2—O6—Cu1ii120.24 (18)
O6ii—Cu1—Si1153.39 (10)Si2—O6—Cu1130.3 (2)
O6—Cu1—Si175.74 (11)Cu1ii—O6—Cu198.68 (16)
Symmetry codes: (i) x, y1, z; (ii) x+1, y, z+2; (iii) x+2, y, z+2; (iv) x+1, y, z; (v) x+2, y, z+1; (vi) x1, y, z; (vii) x, y+1, z.

Experimental details

Crystal data
Chemical formulaNa2(Cu2O11Si4)
Mr461.44
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)5.190 (2), 6.299 (3), 8.196 (4)
α, β, γ (°)96.390 (7), 97.281 (7), 100.461 (7)
V3)258.9 (2)
Z1
Radiation typeMo Kα
µ (mm1)4.71
Crystal size (mm)0.28 × 0.08 × 0.04
Data collection
DiffractometerBruker SMART CCD 1000
diffractometer
Absorption correctionMulti-scan
(TWINABS; Sheldrick, 2002)
Tmin, Tmax0.627, 0.834
No. of measured, independent and
observed [I > 2σ(I)] reflections
1587, 1043, 782
Rint0.042
(sin θ/λ)max1)0.625
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.042, 0.119, 1.01
No. of reflections1043
No. of parameters88
Δρmax, Δρmin (e Å3)1.40, 1.58

Computer programs: SMART (Bruker, 1998), SAINT-Plus (Bruker, 2003), SIR92 (Altomare et al., 1993), SHELXTL (Sheldrick, 2008), DIAMOND (Brandenburg, 2007).

Selected bond lengths (Å) top
Cu1—O5i1.909 (3)Cu1—O61.974 (3)
Cu1—O21.950 (4)Cu1—O2iii2.316 (4)
Cu1—O6ii1.970 (4)
Symmetry codes: (i) x, y1, z; (ii) x+1, y, z+2; (iii) x+2, y, z+2.
 

Acknowledgements

We are grateful to the Fundação para a Ciência e a Tecnologia (FCT, Portugal) for their general financial support under the POCI programme (supported by FEDER) and for a Postdoctoral Fellowship (SFRH/BPD/14410/2003) to LCS.

References

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Volume 64| Part 2| February 2008| Pages i13-i14
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