Acta Cryst. (2007). E63, i177 [ doi:10.1107/S1600536807039797 ]
Single crystals of Sr2NI have been grown for the first time. Redetermination from single-crystal X-ray diffraction data confirms the anti-![[alpha]](http://journals.iucr.org/logos/entities/alpha_rmgif.gif)
-NaFeO2 structure, previously found from powder diffraction data [Bowman, Smith & Gregory (2006). J. Solid State Chem. 179, 130-139]. Iodide ions occupy octahedral voids between layers of edge-sharing NSr6 octahedra.
The title Sr2NI crystals were prepared by reaction of SrI2 (Aldrich, 99.99+%) with distrontium subnitride, Sr2N. Sr2N powder was prepared by the reaction of cleaned Sr metal (Alfa, 99%) with dried nitrogen at 793 K. Due to the air sensitivity of the reactants and products involved, all manipulations were carried out in glove boxes (either recirculating nitrogen-filled or evacuable argon-filled). Stoichiometric ratios of the reactants were thoroughly mixed and ground together, then pressed to form a pellet (ca 1 g). The pellet was placed in a molybdenum foil liner and transferred to a stainless steel crucible, which was subsequently welded shut under an argon atmosphere. The sealed crucibles were heated in a tube furnace (1023 K, 5 d) under flowing argon to prevent oxidation of the steel crucibles. The furnace was cooled slowly (20 K h−1). The crucibles were opened in an N2-filled glove-box. Orange irregular crystals were observed on the pellet surface. Crystals were selected in a recirculating N2-filled glove-box under an optical microscope and placed under RS3000 perfluoropolyether (Riedel de Haën) on a microscope slide prior to mounting on the diffractometer. The moisture-free viscous perfluoropolyether protects the crystals from atmospheric oxygen and moisture without interfering with the diffraction experiment.
Due to twinning present in the crystal the data were integrated using 2 orientation matrices, related by the twin law (−1 0 0, 1 1 0, 0 0 − 1), giving 682 reflections, 388 have contributions from only one component − 197 only belong to the first component, 186 only to second and 303 have contributions from both components. The fraction of the twin component was refined to 0.183 (6).
Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002) and SHELXTL (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ATOMS (Dowty, 1998); software used to prepare material for publication: enCIFer (Allen et al., 2004) and PLATON (Spek, 2003).
![[Figure 1]](./mg2033fig1thm.gif)
| Fig. 1. Polyhedral representation of the structure of Sr2NI, showing [Sr2N]+ layers of edge-sharing NSr6 octahedra alternating with layers of I−. |
![[Figure 2]](./mg2033fig2thm.gif)
| Fig. 2. ORTEPtype plot of the local coordination of Sr to N and I. Both anions are coordinated in a distorted octahedral geometry. (Ellipsoids are drawn at the 90% probability level). |
| INSr2 | Z = 3 |
| Mr = 316.15 | F000 = 408 |
| Trigonal, R3m | Dx = 4.918 Mg m−3 |
| Hall symbol: -R 3 2" | Mo Kα radiation λ = 0.71073 Å |
| a = 4.0049 (6) Å | Cell parameters from 340 reflections |
| b = 4.0049 (6) Å | θ = 5.3–27.2º |
| c = 23.055 (7) Å | µ = 31.99 mm−1 |
| α = 90º | T = 150 (2) K |
| β = 90º | Needle, orange |
| γ = 120º | 0.14 × 0.04 × 0.04 mm |
| V = 320.24 (12) Å3 |
| Bruker SMART1000 CCD area-detector diffractometer | 165 independent reflections |
| Radiation source: sealed tube | 163 reflections with I > 2σ(I) |
| Monochromator: graphite | Rint = 0.032 |
| T = 150(2) K | θmax = 24.9º |
| ω scans | θmin = 5.3º |
| Absorption correction: multi-scan (TWINABS; Bruker, 2007) | h = −4→4 |
| Tmin = 0.175, Tmax = 0.278 | k = −4→4 |
| 682 measured reflections | l = −26→26 |
| 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)] = 0.061 | w = 1/[σ2(Fo2) + (0.1578P)2] where P = (Fo2 + 2Fc2)/3 |
| wR(F2) = 0.192 | (Δ/σ)max < 0.001 |
| S = 1.21 | Δρmax = 1.77 e Å−3 |
| 165 reflections | Δρmin = −1.76 e Å−3 |
| 9 parameters | Extinction correction: none |
| INSr2 | γ = 120º |
| Mr = 316.15 | V = 320.24 (12) Å3 |
| Trigonal, R3m | Z = 3 |
| a = 4.0049 (6) Å | Mo Kα |
| b = 4.0049 (6) Å | µ = 31.99 mm−1 |
| c = 23.055 (7) Å | T = 150 (2) K |
| α = 90º | 0.14 × 0.04 × 0.04 mm |
| β = 90º |
| Bruker SMART1000 CCD area-detector diffractometer | 165 independent reflections |
| Absorption correction: multi-scan (TWINABS; Bruker, 2007) | 163 reflections with I > 2σ(I) |
| Tmin = 0.175, Tmax = 0.278 | Rint = 0.032 |
| 682 measured reflections |
| R[F2 > 2σ(F2)] = 0.061 | 9 parameters |
| wR(F2) = 0.192 | Δρmax = 1.77 e Å−3 |
| S = 1.21 | Δρmin = −1.76 e Å−3 |
| 165 reflections |
Experimental. Data were integrated using 2 orientation matrices, related by the twin law (−1 0 0, 1 1 0, 0 0 − 1). This gave a total of 682 reflections; 379 of these have contributions from only one component, 197 only belong to component 1, 186 only to 2 and 294 have contributions from both components. |
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. |
| x | y | z | Uiso*/Ueq | ||
| I1 | 0.0000 | 0.0000 | 0.0000 | 0.0134 (11) | |
| Sr1 | 0.0000 | 0.0000 | 0.22397 (11) | 0.0095 (10) | |
| N1 | 0.0000 | 0.0000 | 0.5000 | 0.019 (6) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| I1 | 0.0117 (11) | 0.0117 (11) | 0.017 (2) | 0.0059 (5) | 0.000 | 0.000 |
| Sr1 | 0.0085 (11) | 0.0085 (11) | 0.0117 (17) | 0.0042 (5) | 0.000 | 0.000 |
| N1 | 0.019 (7) | 0.019 (7) | 0.019 (18) | 0.009 (4) | 0.000 | 0.000 |
| I1—Sr1i | 3.421 (2) | Sr1—Sr1iii | 3.511 (4) |
| I1—Sr1ii | 3.421 (2) | Sr1—Sr1i | 3.511 (4) |
| I1—Sr1iii | 3.421 (2) | Sr1—Sr1vi | 3.511 (4) |
| I1—Sr1iv | 3.421 (2) | Sr1—Sr1x | 4.0049 (6) |
| I1—Sr1v | 3.421 (2) | Sr1—Sr1xi | 4.0049 (6) |
| I1—Sr1vi | 3.421 (2) | Sr1—Sr1xii | 4.0049 (6) |
| Sr1—N1ii | 2.6631 (13) | N1—Sr1xiii | 2.6631 (13) |
| Sr1—N1iv | 2.6631 (13) | N1—Sr1vii | 2.6631 (13) |
| Sr1—N1v | 2.6631 (13) | N1—Sr1xiv | 2.6631 (13) |
| Sr1—I1vii | 3.421 (2) | N1—Sr1viii | 2.6631 (13) |
| Sr1—I1viii | 3.421 (2) | N1—Sr1ix | 2.6631 (13) |
| Sr1—I1ix | 3.421 (2) | N1—Sr1xv | 2.6631 (13) |
| Sr1i—I1—Sr1ii | 180.00 (6) | I1ix—Sr1—Sr1vi | 96.29 (3) |
| Sr1i—I1—Sr1iii | 71.65 (5) | Sr1iii—Sr1—Sr1vi | 69.54 (9) |
| Sr1ii—I1—Sr1iii | 108.35 (5) | Sr1i—Sr1—Sr1vi | 69.54 (9) |
| Sr1i—I1—Sr1iv | 108.35 (5) | N1ii—Sr1—Sr1x | 41.24 (3) |
| Sr1ii—I1—Sr1iv | 71.65 (5) | N1iv—Sr1—Sr1x | 138.76 (3) |
| Sr1iii—I1—Sr1iv | 180.00 (6) | N1v—Sr1—Sr1x | 90.0 |
| Sr1i—I1—Sr1v | 108.35 (5) | I1vii—Sr1—Sr1x | 125.83 (2) |
| Sr1ii—I1—Sr1v | 71.65 (5) | I1viii—Sr1—Sr1x | 54.17 (2) |
| Sr1iii—I1—Sr1v | 108.35 (5) | I1ix—Sr1—Sr1x | 90.0 |
| Sr1iv—I1—Sr1v | 71.65 (5) | Sr1iii—Sr1—Sr1x | 55.23 (4) |
| Sr1i—I1—Sr1vi | 71.65 (5) | Sr1i—Sr1—Sr1x | 124.77 (4) |
| Sr1ii—I1—Sr1vi | 108.35 (5) | Sr1vi—Sr1—Sr1x | 90.0 |
| Sr1iii—I1—Sr1vi | 71.65 (5) | N1ii—Sr1—Sr1xi | 138.76 (3) |
| Sr1iv—I1—Sr1vi | 108.35 (5) | N1iv—Sr1—Sr1xi | 41.24 (3) |
| Sr1v—I1—Sr1vi | 180.00 (6) | N1v—Sr1—Sr1xi | 90.0 |
| N1ii—Sr1—N1iv | 97.52 (6) | I1vii—Sr1—Sr1xi | 54.17 (2) |
| N1ii—Sr1—N1v | 97.52 (6) | I1viii—Sr1—Sr1xi | 125.83 (2) |
| N1iv—Sr1—N1v | 97.52 (6) | I1ix—Sr1—Sr1xi | 90.0 |
| N1ii—Sr1—I1vii | 162.27 (8) | Sr1iii—Sr1—Sr1xi | 124.77 (4) |
| N1iv—Sr1—I1vii | 94.14 (2) | Sr1i—Sr1—Sr1xi | 55.23 (4) |
| N1v—Sr1—I1vii | 94.14 (2) | Sr1vi—Sr1—Sr1xi | 90.0 |
| N1ii—Sr1—I1viii | 94.14 (2) | Sr1x—Sr1—Sr1xi | 180.00 (15) |
| N1iv—Sr1—I1viii | 162.27 (8) | N1ii—Sr1—Sr1xii | 41.24 (3) |
| N1v—Sr1—I1viii | 94.14 (2) | N1iv—Sr1—Sr1xii | 90.0 |
| I1vii—Sr1—I1viii | 71.65 (5) | N1v—Sr1—Sr1xii | 138.76 (3) |
| N1ii—Sr1—I1ix | 94.14 (2) | I1vii—Sr1—Sr1xii | 125.83 (2) |
| N1iv—Sr1—I1ix | 94.14 (2) | I1viii—Sr1—Sr1xii | 90.0 |
| N1v—Sr1—I1ix | 162.27 (8) | I1ix—Sr1—Sr1xii | 54.17 (2) |
| I1vii—Sr1—I1ix | 71.65 (5) | Sr1iii—Sr1—Sr1xii | 90.0 |
| I1viii—Sr1—I1ix | 71.65 (5) | Sr1i—Sr1—Sr1xii | 124.77 (4) |
| N1ii—Sr1—Sr1iii | 48.76 (3) | Sr1vi—Sr1—Sr1xii | 55.23 (4) |
| N1iv—Sr1—Sr1iii | 101.45 (10) | Sr1x—Sr1—Sr1xii | 60.0 |
| N1v—Sr1—Sr1iii | 48.76 (3) | Sr1xi—Sr1—Sr1xii | 120.0 |
| I1vii—Sr1—Sr1iii | 141.004 (11) | Sr1xiii—N1—Sr1vii | 180.0 |
| I1viii—Sr1—Sr1iii | 96.29 (3) | Sr1xiii—N1—Sr1xiv | 97.52 (6) |
| I1ix—Sr1—Sr1iii | 141.003 (11) | Sr1vii—N1—Sr1xiv | 82.48 (6) |
| N1ii—Sr1—Sr1i | 101.45 (10) | Sr1xiii—N1—Sr1viii | 82.48 (6) |
| N1iv—Sr1—Sr1i | 48.76 (3) | Sr1vii—N1—Sr1viii | 97.52 (6) |
| N1v—Sr1—Sr1i | 48.76 (3) | Sr1xiv—N1—Sr1viii | 180.0 |
| I1vii—Sr1—Sr1i | 96.29 (3) | Sr1xiii—N1—Sr1ix | 82.48 (6) |
| I1viii—Sr1—Sr1i | 141.004 (11) | Sr1vii—N1—Sr1ix | 97.52 (6) |
| I1ix—Sr1—Sr1i | 141.003 (11) | Sr1xiv—N1—Sr1ix | 82.48 (6) |
| Sr1iii—Sr1—Sr1i | 69.54 (9) | Sr1viii—N1—Sr1ix | 97.52 (6) |
| N1ii—Sr1—Sr1vi | 48.76 (3) | Sr1xiii—N1—Sr1xv | 97.52 (6) |
| N1iv—Sr1—Sr1vi | 48.76 (3) | Sr1vii—N1—Sr1xv | 82.48 (6) |
| N1v—Sr1—Sr1vi | 101.45 (10) | Sr1xiv—N1—Sr1xv | 97.52 (6) |
| I1vii—Sr1—Sr1vi | 141.003 (11) | Sr1viii—N1—Sr1xv | 82.48 (6) |
| I1viii—Sr1—Sr1vi | 141.003 (11) | Sr1ix—N1—Sr1xv | 180.00 (10) |
| Symmetry codes: (i) −x+2/3, −y+1/3, −z+1/3; (ii) x−2/3, y−1/3, z−1/3; (iii) −x−1/3, −y−2/3, −z+1/3; (iv) x+1/3, y+2/3, z−1/3; (v) x+1/3, y−1/3, z−1/3; (vi) −x−1/3, −y+1/3, −z+1/3; (vii) x+2/3, y+1/3, z+1/3; (viii) x−1/3, y−2/3, z+1/3; (ix) x−1/3, y+1/3, z+1/3; (x) x−1, y−1, z; (xi) x+1, y+1, z; (xii) x−1, y, z; (xiii) −x−2/3, −y−1/3, −z+2/3; (xiv) −x+1/3, −y+2/3, −z+2/3; (xv) −x+1/3, −y−1/3, −z+2/3. |
Allen, F. H., Johnson, O., Shields, G. P., Smith, B. R. & Towler, M. (2004). J. Appl. Cryst. 37, 335–338.
Andersson, S. (1970). J. Solid State Chem. 1, 306–309.
Bowman, A., Mason, P. V. & Gregory, D. H. (2001). Chem. Commun. pp. 1650–1651.
Bowman, A., Smith, R. I. & Gregory, D. H. (2005). J. Solid State Chem. 178, 1807–1817.
Bowman, A., Smith, R. I. & Gregory, D. H. (2006). J. Solid State Chem. 179, 130–139.
Brese, N. E. & O'Keeffe, M. (1990). J. Solid State Chem. 87, 134–140.
Bruker (2001). SMART (Version 5.624) and SHELXTL. Bruker AXS Inc., Madison, Wisconsin, USA.
Bruker (2002). SAINT. Version 6.36a. Bruker AXS Inc., Madison, Wisconsin, USA.
Bruker (2007). TWINABS. Version 2007/3. Bruker AXS Inc., Madison, Wisconsin, USA.
Dowty, E. (1998). ATOMS. Version 4.1. Shape Software, 521 Hidden Valley Road, Kingsport, TN 37663, USA.
Ehrlich, P. & Deissmann, W. (1958). Angew. Chem. 70, 656–?.
Ehrlich, P., Deissmann, W., Koch, E. & Ullrich, V. (1964). Z. Anorg. Allg. Chem. 328, 243–251.
Ehrlich, P., Linz, W. & Seifert, H. J. (1971). Naturwissenschaften, 58, 219–220.
Emons, H.-H., Anders, D., Roewer, R. & Vogt, F. (1964). Z. Anorg. Allg. Chem. 333, 99–107.
Emons, H.-H., Grothe, W.-H. & Seyfarth, H. (1968). Z. Anorg. Allg. Chem. 363, 191–198.
Hadenfeldt, C. & Herdejürgen, H. (1987). Z. Anorg. Allg. Chem. 545, 177–183.
Hadenfeldt, C. & Herdejürgen, H. (1988). Z. Anorg. Allg. Chem. 558, 35–40.
Jack, D. R., Zeller, M. & Wagner, T. R. (2005). Acta Cryst. C61, i6–i8.
Nicklow, R. A., Wagner, T. R. & Raymond, C. C. (2001). J. Solid State Chem. 160, 134–138.
Reckeweg, O. & DiSalvo, F. J. (2002). Solid State Sci. 4, 575–584.
Rietschel, E. T. & Baernighausen, H. (1969). Z. Anorg. Allg. Chem. 368, 62–72.
Sebel, H. & Wagner, T. R. (2004). J. Solid State Chem. 177, 2772–2776.
Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of Göttingen, Germany.
Spek, A. L. (2003). J. Appl. Cryst. 36, 7–13.
Wagner, T. R. (2002). J. Solid State Chem. 169, 13–18.
Sr2NI belongs to the A2NX (A = Ca—Ba, X = F—I) family of compounds which were originally synthesized several decades ago (Ehrlich & Deissmann, 1958; Ehrlich et al., 1964; Emons et al., 1964; Emons et al., 1968; Andersson, 1970; Ehrlich et al., 1971). It has only been recently that the structures and properties of these compounds have been revealed (Hadenfeldt & Herdejürgen, 1987; Hadenfeldt & Herdejürgen, 1988; Bowman et al., 2001; Nicklow et al., 2001; Reckeweg & DiSalvo, 2002; Wagner, 2002; Sebel & Wagner, 2004; Bowman et al., 2005; Jack et al., 2005; Bowman et al., 2006). With the exception of Ca2NX (X = Cl, Br, I) (Hadenfeldt & Herdejürgen, 1987; Hadenfeldt & Herdejürgen, 1988), single-crystal determinations have been restricted to the lighter halide (X = F) members. These single-crystal determinations have often shown the structures to exhibit important differences to those refined from powder data. We recently investigated the structure of Sr2NI using powder X-ray diffraction (Bowman et al., 2006). Now the successful and unprecedented growth of single crystals of a strontium nitride halide (Sr2NX) phase has allowed the single-crystal structure of Sr2NI to be determined precisely for the first time. Importantly, this study has allowed an accurate determination of the Sr position within the rhombohedral cell and describes well defined thermal parameters which are elongated only slightly along the c direction for Sr and I and very close to isotropic for N.
The data (obtained at 150 K) show that Sr2NI crystallizes in space group R-3 m (No. 166). The structure consists of [NSr2]+ slabs in which N is coordinated octahedrally to six Sr atoms. The layers of the edge-sharing NSr6 octahedra lie parallel to the ab plane stacked along the c-direction. The iodide ion occupies the octahedral voids between these positively charged N—Sr layers. This creates alternating edge-sharing layers of NSr6 and ISr6 octahedra in a cubic close packed (CCP) arrangement (Fig. 1, Fig. 2).
The Sr—N distance is in excellent agreement with that found in the binary subnitride Sr2N (2.6118 (3) Å) (Brese & O'Keeffe, 1990). Further, the Sr—I bond length is also in close agreement with data for SrI2 (3.3382–3.4142 Å) (Rietschel & Baernighausen, 1969).