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

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ISSN: 2056-9890

The trigonal polymorph of strontium tetra­borate, β-SrB4O7

aInstitute of Physics SB RAS, Krasnoyarsk 660036, Russian Federation and Siberian Federal University, Svobodnyi st. 79, Krasnoyarsk 660041, Russian Federation
*Correspondence e-mail: adva@iph.krasn.ru

(Received 6 May 2010; accepted 21 May 2010; online 29 May 2010)

The asymmetric unit of the title compound, β-SrB4O7, contains five Sr atoms (three located on a threefold rotation axis), twelve B and 21 O atoms. The structure is made up from BO3 triangles and BO4 tetra­hedra in a 1:1 ratio. Pairs of BO3 triangles are linked to BO4 tetra­hedra via common corners, forming chains. These chains are further linked to adjacent chains through corner-sharing, leading to a three-dimensional framework with channels running parallel to [001]. The Sr2+ ions reside in the channels and exhibit strongly distorted polyhedra The density of the β-polymorph is considerably lower than that of α-SrB4O7, which is constructed solely from BO4 tetra­hedra.

Related literature

For the ortho­rhom­bic α-polymorph, see: Block et al. (1964[Block, S., Perloff, A. & Weir, C. E. (1964). Acta Cryst. 17, 314-315.]). For the physical properties of this phase, see: Oseledchik et al. (1995[Oseledchik, Y. S., Prosvirnin, A. I., Starshenko, V. V., Osadchuk, V., Pisarevsky, A. I., Belokrys, S. P., Korol, A. S., Svitanko, N. V., Krikunov, S. A. & Selevich, A. F. (1995). Opt. Mater. 4, 669-674.]); Petrov et al. (2004[Petrov, V., Noack, F., Shen, D., Pan, F., Shen, G., Wang, X., Komatsu, R. & Volker, A. (2004). Opt. Lett. 29, 373-375.]); Zaitsev et al. (2006[Zaitsev, A. I., Aleksandrovsky, A. S., Zamkov, A. V. & Sysoev, A. M. (2006). Inorg. Mater. 42, 1360-1362.]); Verwey et al. (1992[Verwey, J. W. M., Dirksen, G. J. & Blasse, G. (1992). J. Phys. Chem. Solids, 53, 367-375.]); Machida et al. (1979[Machida, K., Adachi, G. & Shiokawa, J. (1979). J. Lumin. 21, 101-110.]); Pei et al. (2000[Pei, Z., Zeng, Q. & Su, Q. (2000). J. Phys. Chem. Solids, 61, 9-12.]). For other crystalline phases in the system SrO—B2O3 listed in the ICSD (2009[ICSD (2009). Inorganic Crystal Structure Database. FIZ-Karlsruhe, Germany, and the National Institute of Standards and Technology (NIST), USA. http://www.fiz-karlsruhe.de/icsd.html]), see: Ross & Angel (1991[Ross, N. L. & Angel, R. J. (1991). J. Solid State Chem. 90, 27-30.]); Lin et al. (1999[Lin, Q.-S., Cheng, W.-D., Chen, J.-T. & Huang, J.-S. (1999). J. Solid State Chem. 144, 30-34.]); Wei et al. (2001[Wei, Z. F., Chen, X. L., Wang, F. M., Li, W. C., He, M. & Zhang, Y. (2001). J. Alloys Compd. 327, 10-13.]); Tang et al. (2008[Tang, Z., Chen, X. & Li, M. (2008). Solid State Sci. 10, 894-900.]); Lapshin et al. (2007[Lapshin, A. E., Litovchik, E. O., Polyakova, I. G. & Shepelev, Yu. F. (2007). Zh. Neorg. Khim. 52, 907-911.]); Kim et al. (1996[Kim, J.-B., Lee, K.-S., Suh, I.-H., Lee, J.-H., Park, J.-R. & Shin, Y.-H. (1996). Acta Cryst. C52, 498-500.]). For glass-phases in this system, see: Imaoka (1959[Imaoka, M. (1959). J. Ceram. Assoc. Jpn, 67, 364-366.]); Polyakova & Litovchik (2008[Polyakova, I. G. & Litovchik, E. O. (2008). Fiz. Khim. Stekla, 34, 488-502.]). For a review of B—O bond lengths in BO3 and BO4 units, see: Zobetz (1982[Zobetz, E. (1982). Z. Kristallogr. 160, 81-92.], 1990[Zobetz, E. (1990). Z. Kristallogr. 191, 45-57.]).

Experimental

Crystal data
  • SrB4O7

  • Mr = 242.86

  • Trigonal, P 3

  • a = 17.145 (1) Å

  • c = 4.2527 (5) Å

  • V = 1082.61 (16) Å3

  • Z = 9

  • Mo Kα radiation

  • μ = 11.19 mm−1

  • T = 296 K

  • 0.40 × 0.25 × 0.18 mm

Data collection
  • Bruker SMART CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 2004[Sheldrick, G. M. (2004). SADABS. University of Göttingen, Germany.]) Tmin = 0.095, Tmax = 0.242

  • 10350 measured reflections

  • 3709 independent reflections

  • 3202 reflections with I > 2σ(I)

  • Rint = 0.054

Refinement
  • R[F2 > 2σ(F2)] = 0.030

  • wR(F2) = 0.064

  • S = 0.85

  • 3709 reflections

  • 265 parameters

  • Δρmax = 1.02 e Å−3

  • Δρmin = −0.49 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), 1836 Friedel pairs

  • Flack parameter: −0.030 (7)

Data collection: SMART (Bruker, 2001[Bruker (2001). SMART and SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT-Plus (Bruker, 2001[Bruker (2001). SMART and SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.

Supporting information


Comment top

The orthorhombic phase of strontium tetraborate, α-SrB4O7 (I), is known for a long time (Block et al., 1964). This compound has attracted attention owing to its interesting physical properties, namely an unprecedented fundamental optical-absorption edge among oxide compounds (~130 nm), high non-linear optical coefficients (Oseledchik et al., 1995; Petrov et al., 2004; Zaitsev et al., 2006), good luminescent characteristics and an ability to stabilize rare-earth elements in divalent state (Verwey et al., 1992; Pei et al., 2000; Machida et al., 1979).

SrB4O7 falls in a glass-forming range within the SrO—B2O3 system and can simply be obtained as a glass (Imaoka, 1959). The process of glass re-crystallization occurs through complex mechanisms with probabilistic formation of other crystalline phases, specifically of metastable phases. Such a phase was in fact observed and designated as β-SrB4O7 (Polyakova & Litovchik, 2008). However, X-ray powder diffraction data of this phase and of two other new compounds described by these authors were not analysed because of impure samples.

The FIZ/NIST Inorganic Crystal Structure Database (release 2009; ICSD, 2009) reveals six phases in the SrO—B2O3 system besides (I): strontium diborate, (IIa), SrB2O4 (Kim et al., 1996), its high-pressure form (Ross & Angel, 1991), (IIb), distrontium diborate, Sr2B2O5, (III), (Lin et al., 1999), tristrontium tetraborate, Sr3B2O6, (IV), (Wei et al., 2001), distrontium hexadecaborate, Sr2B16O26, (V), (Tang et al., 2008) and tetrastrontium tetradecaborate, Sr4B14O25, (VI), (Lapshin et al., 2007). Only two of these phases crystallize in non-centrosymmetric space groups, viz. (I, Pmn21 and VI, Cmc21). The main feature of all these structures are BOx units (x = 3,4). Isolated (IV) or flat pairs (III) of BO3 triangles, a framework of BO4 tetrahedra with shared vertices (I, II) and a framework of triangles and tetrahedra with shared vertices (V, VI) are found in these structures.

In the process of glass re-crystallization of a strontium tetraborate composition at 973–983 K during one day, we obtained β-SrB4O7 crystals with dimensions of ~200–400 µm. The crystals were located on the glass surface and were optically homogeneous (i.e. crystals showed homogeneous extinction when observed under a polarizing microscope). The crystals possess strong anisotropy when abrased, and crystals with an elongated ellipsoidal shape were obtained in such a way. As it turned out, the crystals are most firm along the c-direction.

The crystal structure of (I) is built up from a three-dimensional framework of connected boron-oxygen tetrahedra. The asymmetric unit of the title structure contains five Sr (three on special positions), twelve B and 21 O atoms. Alternatively, the structural formula of the title compound can thus be written as Sr3B12O21. It consists of BO3 triangles and BO4 tetrahedra in an 1:1 ratio (3:1 for structure V and 3:4 for structure VI). They form a three-dimensional framework constructed via common vertices. The BO3 triangles are linked to one another so that two of their vertices and the bridging O atom are located on a straight line (see O1, O3, O5; O6, O7, O10 and O11, O13, O15 in Fig.1). The plane of one triangle in such a pair is tilted relatively to the other one about the line with an angle of ~20°. The remaining two vertices are common with the same tetrahedron (e.g. see O2 and O4 in Fig.1). The BO4 tetrahedra are connected to one another via common vertices and form chains along the c-direction (Fig. 2). These chains are connected with pairs of BO3 triangles, leading to the formation of channels in the structure. The channels are filled with strontium ions (Fig. 3). The coordination polyhedra around the strontium ions are non-regular and defined by six O atoms in the range 2.479 (3)–2.786 (3) Å when a distance < 2.8 Å is considered as relevant.

All vertices in the anionic framework are shared so that every oxygen atom is connected to two boron atoms. The B—O distances fall into the interval 1.323 (6)–1.420 (6)Å (average is 1.367 (6) Å) for BO3 triangles and into the interval 1.425 (6)–1.538 (6) Å (average is 1.474 (6) Å) for BO4 tetrahedra. These values compare well with the mean bond lengths calculated for various borate structures (Zobetz, 1982, 1990).

In comparison with α-SrB4O7 which is constructued solely from BO4 tetrahedra, the density of the β-polymorph is considerably lower.

Related literature top

For the orthorhombic α-polymorph, see: Block et al. (1964). For the physical properties of this phase, see: Oseledchik et al. (1995); Petrov et al. (2004); Zaitsev et al. (2006); Verwey et al. (1992); Machida et al. (1979); Pei et al. (2000). For other crystalline phases in the system SrO—B2O3 listed in the ICSD (2009), see: Ross & Angel (1991); Lin et al. (1999); Wei et al. (2001); Tang et al. (2008); Lapshin et al. (2007); Kim et al. (1996). For glass-phases in this system, see: Imaoka (1959); Polyakova & Litovchik (2008). For a review of B—O bond lengths in BO3 and BO4 units, see: Zobetz (1982, 1990).

Experimental top

Crystals were extracted out of glass by careful dissolving of the latter in a 2% HNO3 solution. The initial glass has been made from a mixture of SrCO3 (99.8%) and H3BO3 (99.98%) in a 1:4 ratio. The mixture was heated up to 353—363 K with addition of a small amount of water and careful mixing until CO2 gas evolution had stopped. Then the temperature was increased slowly up to 573 K to yield a anhydrous phase. The derived mixture was then placed into a glass-carbon crucible and kept in a molten state at 1323 K during 6 h in a nitrogen atmosphere. The flux was cooled in air down to 773 K and the glass was finally annealed at 723 K during a day to remove strain.

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. View of the basic structural motif in the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Symmetry codes: (i) x, y, z-1; (ii) 1-y, 1+x-y, 1+z; (iii) -y, x-y, 1+z; (iv) 1-y, x-y, 1+z.
[Figure 2] Fig. 2. Columns of BO4 tetrahedra with shared vertices and attached BO3 triangles extending along the c-direction.
[Figure 3] Fig. 3. View down [001] of the framework structure of the title compound showing the formation of channels that are filled with Sr2+ ions.
strontium tetraborate top
Crystal data top
SrB4O7Dx = 3.353 (1) Mg m3
Mr = 242.86Mo Kα radiation, λ = 0.71073 Å
Trigonal, P3Cell parameters from 2820 reflections
Hall symbol: P 3θ = 2.4–29.3°
a = 17.145 (1) ŵ = 11.19 mm1
c = 4.2527 (5) ÅT = 296 K
V = 1082.61 (16) Å3Ellipsoidal, colorless
Z = 90.40 × 0.25 × 0.18 mm
F(000) = 1026
Data collection top
Bruker SMART CCD area-detector
diffractometer
3709 independent reflections
Radiation source: fine-focus sealed tube3202 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.054
ϕ and ω scansθmax = 28.7°, θmin = 2.4°
Absorption correction: multi-scan
(SADABS; Sheldrick, 2004)
h = 2223
Tmin = 0.095, Tmax = 0.242k = 2323
10350 measured reflectionsl = 55
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: full w = 1/[σ2(Fo2) + (0.P)2]
where P = (Fo2 + 2Fc2)/3
R[F2 > 2σ(F2)] = 0.030(Δ/σ)max < 0.001
wR(F2) = 0.064Δρmax = 1.02 e Å3
S = 0.85Δρmin = 0.49 e Å3
3709 reflectionsExtinction correction: SHELXTL (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
265 parametersExtinction coefficient: 0.0794 (13)
0 restraintsAbsolute structure: Flack (1983), 1836 Friedel pairs
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.030 (7)
Crystal data top
SrB4O7Z = 9
Mr = 242.86Mo Kα radiation
Trigonal, P3µ = 11.19 mm1
a = 17.145 (1) ÅT = 296 K
c = 4.2527 (5) Å0.40 × 0.25 × 0.18 mm
V = 1082.61 (16) Å3
Data collection top
Bruker SMART CCD area-detector
diffractometer
3709 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 2004)
3202 reflections with I > 2σ(I)
Tmin = 0.095, Tmax = 0.242Rint = 0.054
10350 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0300 restraints
wR(F2) = 0.064Δρmax = 1.02 e Å3
S = 0.85Δρmin = 0.49 e Å3
3709 reflectionsAbsolute structure: Flack (1983), 1836 Friedel pairs
265 parametersAbsolute structure parameter: 0.030 (7)
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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
Sr10.00000.00000.50000.0106 (2)
Sr20.66670.33330.7047 (2)0.0097 (2)
Sr30.33330.66670.6084 (5)0.01172 (15)
Sr40.32408 (4)0.33158 (4)0.7001 (4)0.00732 (14)
Sr50.00569 (3)0.33541 (4)0.5183 (4)0.00743 (15)
O10.3441 (2)0.5031 (2)0.5634 (9)0.0115 (7)
O20.2472 (2)0.3798 (2)0.2476 (8)0.0094 (7)
O30.2591 (2)0.5240 (2)0.1833 (8)0.0108 (7)
O40.1239 (2)0.3939 (2)0.0012 (9)0.0109 (7)
O50.1760 (2)0.5441 (2)0.1939 (8)0.0090 (7)
O60.1571 (2)0.1803 (2)0.4810 (9)0.0119 (8)
O70.2841 (2)0.2150 (2)0.1685 (8)0.0075 (6)
O80.1428 (2)0.0790 (2)0.0952 (8)0.0109 (7)
O90.2767 (2)0.0826 (2)0.0917 (8)0.0083 (7)
O100.1278 (2)0.0221 (2)0.2863 (8)0.0095 (7)
O110.5201 (2)0.3007 (2)0.4426 (8)0.0082 (7)
O120.4709 (2)0.4061 (2)0.3108 (8)0.0077 (7)
O130.6000 (2)0.4102 (2)0.0726 (8)0.0105 (7)
O140.5899 (2)0.5436 (2)0.0455 (8)0.0065 (6)
O150.6814 (2)0.5195 (2)0.3106 (8)0.0082 (7)
O160.0899 (2)0.2724 (2)0.3487 (8)0.0084 (7)
O170.1632 (2)0.2814 (2)0.8498 (8)0.0085 (7)
O180.3864 (2)0.1604 (2)0.2995 (8)0.0082 (7)
O190.3945 (2)0.2362 (2)0.7992 (8)0.0062 (6)
O200.5007 (2)0.5578 (2)0.4336 (8)0.0073 (7)
O210.4320 (2)0.4828 (2)0.9349 (8)0.0067 (7)
B10.2862 (4)0.4681 (4)0.3246 (14)0.0079 (10)*
B20.1811 (3)0.4849 (3)0.0018 (13)0.0059 (10)*
B30.1948 (3)0.1620 (3)0.2422 (13)0.0075 (10)*
B40.1853 (4)0.0444 (3)0.0934 (13)0.0071 (10)*
B50.5250 (3)0.3704 (3)0.2794 (12)0.0052 (9)*
B60.6277 (3)0.4939 (3)0.0547 (13)0.0063 (10)*
B70.1537 (4)0.3283 (3)0.1104 (13)0.0048 (10)*
B80.1082 (3)0.2266 (3)0.5981 (12)0.0052 (10)*
B90.3394 (4)0.1748 (4)0.0454 (12)0.0064 (11)*
B100.4409 (3)0.2160 (3)0.5607 (12)0.0063 (10)*
B110.4960 (4)0.4991 (4)0.1768 (13)0.0076 (12)*
B120.4379 (3)0.5431 (3)0.6829 (12)0.0061 (10)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Sr10.0098 (3)0.0098 (3)0.0121 (5)0.00490 (15)0.0000.000
Sr20.0093 (3)0.0093 (3)0.0106 (5)0.00466 (16)0.0000.000
Sr30.0100 (2)0.0100 (2)0.0151 (4)0.00502 (10)0.0000.000
Sr40.0072 (3)0.0066 (3)0.0083 (3)0.0036 (2)0.0001 (3)0.0014 (2)
Sr50.0072 (3)0.0076 (3)0.0082 (3)0.0043 (2)0.0007 (2)0.0015 (2)
O10.0055 (16)0.0191 (19)0.0082 (17)0.0048 (15)0.0004 (14)0.0017 (14)
O20.0069 (16)0.0074 (16)0.0109 (17)0.0014 (13)0.0039 (13)0.0001 (13)
O30.0099 (16)0.0065 (16)0.0141 (18)0.0027 (14)0.0075 (14)0.0033 (14)
O40.0090 (16)0.0103 (17)0.0153 (19)0.0062 (14)0.0051 (14)0.0006 (14)
O50.0074 (16)0.0100 (17)0.0091 (18)0.0039 (14)0.0009 (13)0.0018 (13)
O60.0139 (19)0.0164 (18)0.0101 (18)0.0110 (16)0.0039 (14)0.0042 (15)
O70.0080 (16)0.0090 (16)0.0058 (16)0.0046 (14)0.0001 (13)0.0004 (13)
O80.0065 (16)0.0099 (16)0.0148 (19)0.0029 (14)0.0034 (14)0.0030 (14)
O90.0076 (16)0.0109 (16)0.0081 (16)0.0059 (14)0.0012 (13)0.0006 (13)
O100.0087 (17)0.0060 (16)0.0148 (19)0.0044 (14)0.0046 (14)0.0022 (14)
O110.0061 (16)0.0095 (16)0.0093 (17)0.0042 (14)0.0016 (13)0.0018 (13)
O120.0090 (16)0.0090 (16)0.0069 (16)0.0057 (14)0.0031 (13)0.0025 (13)
O130.0104 (17)0.0078 (16)0.0125 (18)0.0039 (14)0.0087 (13)0.0050 (13)
O140.0077 (15)0.0062 (15)0.0060 (16)0.0039 (13)0.0001 (13)0.0009 (12)
O150.0086 (18)0.0114 (18)0.0048 (17)0.0053 (15)0.0040 (14)0.0046 (14)
O160.0069 (16)0.0130 (17)0.0075 (16)0.0066 (14)0.0036 (13)0.0026 (13)
O170.0082 (16)0.0092 (16)0.0077 (17)0.0041 (14)0.0004 (13)0.0023 (13)
O180.0081 (16)0.0112 (16)0.0079 (17)0.0068 (14)0.0016 (13)0.0003 (13)
O190.0089 (15)0.0083 (16)0.0043 (16)0.0065 (13)0.0021 (12)0.0017 (12)
O200.0099 (16)0.0099 (16)0.0038 (15)0.0061 (14)0.0024 (13)0.0000 (12)
O210.0057 (15)0.0066 (15)0.0076 (17)0.0029 (13)0.0009 (12)0.0029 (13)
Geometric parameters (Å, º) top
Sr1—O10i2.569 (3)Sr5—B11xii3.171 (6)
Sr1—O10ii2.569 (3)O1—B11.335 (6)
Sr1—O10iii2.569 (3)O1—B121.486 (6)
Sr1—O8iv2.734 (3)O2—B11.354 (6)
Sr1—O8v2.734 (3)O2—B71.509 (6)
Sr1—O82.734 (3)O2—Sr4xiv2.988 (3)
Sr1—O62.913 (4)O3—B11.392 (6)
Sr1—O6v2.913 (4)O3—B21.401 (6)
Sr1—O6iv2.913 (4)O3—Sr3xiv3.236 (3)
Sr1—B33.285 (5)O4—B21.366 (6)
Sr1—B3iv3.285 (5)O4—B71.521 (6)
Sr1—B3v3.285 (5)O4—Sr5xiv2.816 (3)
Sr2—O11vi2.542 (3)O5—B21.340 (6)
Sr2—O11vii2.542 (3)O5—B12xv1.489 (6)
Sr2—O112.542 (3)O5—Sr3xiv2.594 (3)
Sr2—O13viii2.644 (3)O6—B31.323 (6)
Sr2—O13ix2.644 (3)O6—B81.499 (6)
Sr2—O13ii2.644 (3)O7—B31.370 (6)
Sr2—O15viii3.074 (3)O7—B91.517 (6)
Sr2—O15ix3.074 (3)O7—Sr4xiv2.657 (3)
Sr2—O15ii3.074 (3)O8—B31.394 (6)
Sr2—B6viii3.303 (5)O8—B41.399 (6)
Sr2—B6ix3.303 (5)O8—Sr1xiv3.304 (3)
Sr2—B6ii3.303 (5)O9—B41.364 (6)
Sr3—O5x2.594 (3)O9—B91.516 (6)
Sr3—O5ii2.594 (3)O9—Sr5xvi2.676 (3)
Sr3—O5xi2.594 (3)O10—B41.349 (6)
Sr3—O3xii2.786 (3)O10—B8xvi1.487 (5)
Sr3—O32.786 (3)O10—Sr1xiv2.569 (3)
Sr3—O3xiii2.786 (3)O11—B51.348 (6)
Sr3—O1xii2.908 (3)O11—B101.494 (6)
Sr3—O1xiii2.908 (3)O12—B51.350 (6)
Sr3—O12.908 (3)O12—B111.537 (6)
Sr3—O3x3.236 (3)O13—B61.377 (6)
Sr3—O3xi3.236 (4)O13—B51.419 (6)
Sr3—O3ii3.236 (4)O13—Sr2xiv2.644 (3)
Sr4—O192.507 (3)O14—B61.371 (6)
Sr4—O212.519 (3)O14—B111.503 (6)
Sr4—O172.526 (3)O14—Sr5xiii2.657 (3)
Sr4—O7ii2.657 (3)O14—Sr5xvii2.836 (3)
Sr4—O22.685 (3)O15—B61.349 (6)
Sr4—O122.737 (3)O15—B10xviii1.501 (6)
Sr4—O12.845 (4)O15—Sr5xvii2.649 (3)
Sr4—O72.864 (3)O15—Sr2xiv3.074 (3)
Sr4—O62.893 (4)O16—B81.445 (6)
Sr4—O2ii2.988 (3)O16—B71.447 (6)
Sr4—B123.145 (5)O17—B81.425 (6)
Sr4—B13.158 (5)O17—B7ii1.426 (6)
Sr5—O162.479 (3)O18—B91.441 (6)
Sr5—O20xii2.482 (3)O18—B101.458 (6)
Sr5—O18v2.539 (3)O18—Sr5iv2.539 (3)
Sr5—O15x2.649 (3)O19—B101.434 (6)
Sr5—O14xii2.657 (3)O19—B9ii1.450 (5)
Sr5—O9i2.676 (3)O20—B121.440 (6)
Sr5—O4ii2.816 (3)O20—B111.460 (6)
Sr5—O14x2.836 (3)O20—Sr5xiii2.482 (3)
Sr5—O42.924 (4)O21—B11ii1.425 (6)
Sr5—B10v3.129 (5)O21—B121.458 (6)
Sr5—B6x3.149 (5)
O10i—Sr1—O10ii108.20 (8)O7—Sr4—O2ii145.41 (8)
O10i—Sr1—O10iii108.20 (8)O6—Sr4—O2ii97.10 (9)
O10ii—Sr1—O10iii108.20 (8)O16—Sr5—O20xii116.34 (10)
O10i—Sr1—O8iv155.68 (11)O16—Sr5—O18v104.21 (10)
O10ii—Sr1—O8iv94.57 (10)O20xii—Sr5—O18v119.04 (10)
O10iii—Sr1—O8iv71.17 (10)O16—Sr5—O15x152.34 (10)
O10i—Sr1—O8v71.17 (10)O20xii—Sr5—O15x90.34 (10)
O10ii—Sr1—O8v155.68 (11)O18v—Sr5—O15x52.72 (10)
O10iii—Sr1—O8v94.57 (10)O16—Sr5—O14xii112.32 (11)
O8iv—Sr1—O8v84.57 (11)O20xii—Sr5—O14xii54.17 (10)
O10i—Sr1—O894.57 (10)O18v—Sr5—O14xii69.52 (10)
O10ii—Sr1—O871.17 (10)O15x—Sr5—O14xii76.45 (10)
O10iii—Sr1—O8155.68 (11)O16—Sr5—O9i85.40 (10)
O8iv—Sr1—O884.57 (11)O20xii—Sr5—O9i148.56 (12)
O8v—Sr1—O884.57 (11)O18v—Sr5—O9i72.45 (10)
O10i—Sr1—O649.69 (9)O15x—Sr5—O9i73.60 (10)
O10ii—Sr1—O676.23 (9)O14xii—Sr5—O9i140.89 (9)
O10iii—Sr1—O6156.14 (11)O16—Sr5—O4ii77.96 (10)
O8iv—Sr1—O6132.54 (10)O20xii—Sr5—O4ii83.34 (10)
O8v—Sr1—O686.46 (9)O18v—Sr5—O4ii151.29 (11)
O8—Sr1—O648.18 (9)O15x—Sr5—O4ii114.40 (11)
O10i—Sr1—O6v76.23 (9)O14xii—Sr5—O4ii136.93 (9)
O10ii—Sr1—O6v156.14 (11)O9i—Sr5—O4ii79.29 (10)
O10iii—Sr1—O6v49.69 (9)O16—Sr5—O14x142.36 (10)
O8iv—Sr1—O6v86.46 (9)O20xii—Sr5—O14x70.68 (10)
O8v—Sr1—O6v48.18 (9)O18v—Sr5—O14x102.82 (9)
O8—Sr1—O6v132.54 (10)O15x—Sr5—O14x50.85 (9)
O6—Sr1—O6v119.923 (7)O14xii—Sr5—O14x101.42 (10)
O10i—Sr1—O6iv156.14 (11)O9i—Sr5—O14x78.32 (9)
O10ii—Sr1—O6iv49.69 (9)O4ii—Sr5—O14x65.84 (10)
O10iii—Sr1—O6iv76.23 (9)O16—Sr5—O451.39 (10)
O8iv—Sr1—O6iv48.18 (9)O20xii—Sr5—O471.17 (10)
O8v—Sr1—O6iv132.54 (10)O18v—Sr5—O4108.16 (10)
O8—Sr1—O6iv86.46 (9)O15x—Sr5—O4142.90 (10)
O6—Sr1—O6iv119.923 (8)O14xii—Sr5—O466.60 (9)
O6v—Sr1—O6iv119.923 (8)O9i—Sr5—O4136.26 (9)
O11vi—Sr2—O11vii102.21 (9)O4ii—Sr5—O495.60 (10)
O11vi—Sr2—O11102.21 (9)O14x—Sr5—O4139.09 (9)
O11vii—Sr2—O11102.21 (9)B1—O1—B12149.0 (4)
O11vi—Sr2—O13viii94.41 (10)B1—O1—Sr490.7 (3)
O11vii—Sr2—O13viii75.13 (10)B12—O1—Sr487.2 (2)
O11—Sr2—O13viii163.33 (10)B1—O1—Sr395.2 (3)
O11vi—Sr2—O13ix75.13 (10)B12—O1—Sr396.2 (3)
O11vii—Sr2—O13ix163.33 (10)Sr4—O1—Sr3161.90 (14)
O11—Sr2—O13ix94.41 (10)B1—O2—B7122.2 (4)
O13viii—Sr2—O13ix88.58 (11)B1—O2—Sr497.3 (3)
O11vi—Sr2—O13ii163.33 (10)B7—O2—Sr4129.7 (3)
O11vii—Sr2—O13ii94.41 (10)B1—O2—Sr4xiv117.3 (3)
O11—Sr2—O13ii75.13 (10)B7—O2—Sr4xiv91.4 (3)
O13viii—Sr2—O13ii88.58 (11)Sr4—O2—Sr4xiv96.96 (10)
O13ix—Sr2—O13ii88.58 (11)B1—O3—B2118.8 (4)
O11vi—Sr2—O15viii48.77 (9)B1—O3—Sr399.3 (3)
O11vii—Sr2—O15viii77.18 (10)B2—O3—Sr3133.8 (3)
O11—Sr2—O15viii148.54 (9)B1—O3—Sr3xiv134.9 (3)
O13viii—Sr2—O15viii47.70 (9)B2—O3—Sr3xiv81.8 (3)
O13ix—Sr2—O15viii89.33 (9)Sr3—O3—Sr3xiv89.54 (8)
O13ii—Sr2—O15viii136.27 (10)B2—O4—B7122.2 (4)
O11vi—Sr2—O15ix77.18 (10)B2—O4—Sr5xiv112.8 (3)
O11vii—Sr2—O15ix148.54 (9)B7—O4—Sr5xiv117.1 (3)
O11—Sr2—O15ix48.77 (9)B2—O4—Sr5112.8 (3)
O13viii—Sr2—O15ix136.27 (10)B7—O4—Sr589.7 (2)
O13ix—Sr2—O15ix47.70 (9)Sr5xiv—O4—Sr595.60 (10)
O13ii—Sr2—O15ix89.33 (9)B2—O5—B12xv137.7 (4)
O15viii—Sr2—O15ix119.955 (5)B2—O5—Sr3xiv112.1 (3)
O11vi—Sr2—O15ii148.54 (9)B12xv—O5—Sr3xiv110.1 (2)
O11vii—Sr2—O15ii48.77 (9)B3—O6—B8148.2 (4)
O11—Sr2—O15ii77.18 (10)B3—O6—Sr494.5 (3)
O13viii—Sr2—O15ii89.33 (9)B8—O6—Sr489.0 (2)
O13ix—Sr2—O15ii136.27 (10)B3—O6—Sr194.1 (3)
O13ii—Sr2—O15ii47.70 (9)B8—O6—Sr195.1 (2)
O15viii—Sr2—O15ii119.955 (6)Sr4—O6—Sr1156.60 (14)
O15ix—Sr2—O15ii119.955 (5)B3—O7—B9121.5 (4)
O5x—Sr3—O5ii110.02 (8)B3—O7—Sr4xiv116.9 (3)
O5x—Sr3—O5xi110.02 (8)B9—O7—Sr4xiv95.6 (2)
O5ii—Sr3—O5xi110.02 (8)B3—O7—Sr494.6 (3)
O5x—Sr3—O3xii70.47 (10)B9—O7—Sr4127.1 (3)
O5ii—Sr3—O3xii94.31 (9)Sr4xiv—O7—Sr4100.68 (10)
O5xi—Sr3—O3xii152.90 (11)B3—O8—B4119.2 (4)
O5x—Sr3—O3152.90 (11)B3—O8—Sr1100.4 (3)
O5ii—Sr3—O370.47 (10)B4—O8—Sr1132.7 (3)
O5xi—Sr3—O394.31 (9)B3—O8—Sr1xiv136.6 (3)
O3xii—Sr3—O382.43 (11)B4—O8—Sr1xiv79.8 (3)
O5x—Sr3—O3xiii94.31 (9)Sr1—O8—Sr1xiv89.02 (8)
O5ii—Sr3—O3xiii152.90 (11)B4—O9—B9123.2 (4)
O5xi—Sr3—O3xiii70.47 (10)B4—O9—Sr5xvi114.8 (3)
O3xii—Sr3—O3xiii82.43 (11)B9—O9—Sr5xvi120.0 (2)
O3—Sr3—O3xiii82.43 (11)B4—O10—B8xvi135.4 (4)
O5x—Sr3—O1xii77.41 (9)B4—O10—Sr1xiv114.0 (3)
O5ii—Sr3—O1xii49.47 (9)B8xvi—O10—Sr1xiv110.6 (3)
O5xi—Sr3—O1xii158.70 (11)B5—O11—B10131.2 (4)
O3xii—Sr3—O1xii48.06 (9)B5—O11—Sr2114.5 (3)
O3—Sr3—O1xii84.14 (10)B10—O11—Sr2112.6 (3)
O3xiii—Sr3—O1xii129.98 (11)B5—O12—B11122.3 (4)
O5x—Sr3—O1xiii49.47 (9)B5—O12—Sr4121.9 (3)
O5ii—Sr3—O1xiii158.70 (10)B11—O12—Sr4115.1 (3)
O5xi—Sr3—O1xiii77.41 (9)B6—O13—B5120.1 (4)
O3xii—Sr3—O1xiii84.14 (10)B6—O13—Sr2xiv106.1 (3)
O3—Sr3—O1xiii129.98 (11)B5—O13—Sr2xiv129.8 (3)
O3xiii—Sr3—O1xiii48.06 (9)B6—O14—B11121.3 (4)
O1xii—Sr3—O1xiii119.572 (18)B6—O14—Sr5xiii119.7 (3)
O5x—Sr3—O1158.70 (11)B11—O14—Sr5xiii95.3 (3)
O5ii—Sr3—O177.41 (9)B6—O14—Sr5xvii89.9 (3)
O5xi—Sr3—O149.47 (9)B11—O14—Sr5xvii130.0 (3)
O3xii—Sr3—O1129.98 (11)Sr5xiii—O14—Sr5xvii101.42 (10)
O3—Sr3—O148.06 (9)B6—O15—B10xviii147.5 (4)
O3xiii—Sr3—O184.14 (9)B6—O15—Sr5xvii98.7 (3)
O1xii—Sr3—O1119.572 (19)B10xviii—O15—Sr5xvii93.8 (2)
O1xiii—Sr3—O1119.572 (19)B6—O15—Sr2xiv87.5 (3)
O5x—Sr3—O3x44.45 (9)B10xviii—O15—Sr2xiv89.5 (2)
O5ii—Sr3—O3x68.82 (9)Sr5xvii—O15—Sr2xiv162.45 (13)
O5xi—Sr3—O3x109.89 (10)B8—O16—B7125.3 (4)
O3xii—Sr3—O3x89.54 (8)B8—O16—Sr5113.2 (3)
O3—Sr3—O3x137.69 (4)B7—O16—Sr5111.1 (3)
O3xiii—Sr3—O3x137.69 (4)B8—O17—B7ii137.0 (4)
O1xii—Sr3—O3x60.73 (9)B8—O17—Sr4106.5 (3)
O1xiii—Sr3—O3x89.91 (9)B7ii—O17—Sr4114.7 (3)
O1—Sr3—O3x129.76 (10)B9—O18—B10133.6 (4)
O5x—Sr3—O3xi68.82 (9)B9—O18—Sr5iv123.3 (3)
O5ii—Sr3—O3xi109.89 (10)B10—O18—Sr5iv99.5 (3)
O5xi—Sr3—O3xi44.45 (9)B10—O19—B9ii125.1 (4)
O3xii—Sr3—O3xi137.69 (4)B10—O19—Sr4123.0 (3)
O3—Sr3—O3xi137.69 (4)B9ii—O19—Sr4104.1 (3)
O3xiii—Sr3—O3xi89.54 (8)B12—O20—B11130.6 (4)
O1xii—Sr3—O3xi129.76 (10)B12—O20—Sr5xiii120.1 (3)
O1xiii—Sr3—O3xi60.73 (9)B11—O20—Sr5xiii104.0 (3)
O1—Sr3—O3xi89.91 (9)B11ii—O21—B12128.2 (4)
O3x—Sr3—O3xi69.12 (9)O1—B1—O2121.8 (5)
O5x—Sr3—O3ii109.89 (10)O1—B1—O3116.7 (4)
O5ii—Sr3—O3ii44.45 (9)O2—B1—O3121.1 (4)
O5xi—Sr3—O3ii68.82 (9)O5—B2—O4126.2 (4)
O3xii—Sr3—O3ii137.69 (4)O5—B2—O3112.9 (4)
O3—Sr3—O3ii89.54 (8)O4—B2—O3120.6 (4)
O3xiii—Sr3—O3ii137.69 (4)O6—B3—O7122.4 (4)
O1xii—Sr3—O3ii89.91 (9)O6—B3—O8116.6 (4)
O1xiii—Sr3—O3ii129.76 (10)O7—B3—O8120.5 (4)
O1—Sr3—O3ii60.73 (9)O10—B4—O9125.9 (4)
O3x—Sr3—O3ii69.12 (9)O10—B4—O8113.1 (4)
O3xi—Sr3—O3ii69.12 (9)O9—B4—O8120.7 (4)
O19—Sr4—O21105.01 (10)O11—B5—O12126.8 (4)
O19—Sr4—O17122.38 (10)O11—B5—O13112.6 (4)
O21—Sr4—O17111.46 (10)O12—B5—O13120.4 (4)
O19—Sr4—O7ii53.90 (9)O15—B6—O14120.4 (4)
O21—Sr4—O7ii104.90 (10)O15—B6—O13118.6 (4)
O17—Sr4—O7ii74.20 (10)O14—B6—O13120.1 (4)
O19—Sr4—O2142.35 (11)O17xiv—B7—O16115.6 (4)
O21—Sr4—O2100.85 (10)O17xiv—B7—O2104.0 (4)
O17—Sr4—O270.44 (10)O16—B7—O2110.3 (4)
O7ii—Sr4—O2141.90 (9)O17xiv—B7—O4110.8 (4)
O19—Sr4—O1277.05 (9)O16—B7—O4106.4 (4)
O21—Sr4—O1274.24 (10)O2—B7—O4109.7 (4)
O17—Sr4—O12154.69 (11)O17—B8—O16116.4 (4)
O7ii—Sr4—O12129.48 (9)O17—B8—O10i111.8 (4)
O2—Sr4—O1284.31 (10)O16—B8—O10i109.5 (4)
O19—Sr4—O1149.31 (10)O17—B8—O6103.8 (4)
O21—Sr4—O150.97 (9)O16—B8—O6112.0 (4)
O17—Sr4—O187.17 (10)O10i—B8—O6102.2 (3)
O7ii—Sr4—O1141.53 (10)O18—B9—O19xiv116.7 (4)
O2—Sr4—O150.18 (10)O18—B9—O9105.9 (4)
O12—Sr4—O177.65 (9)O19xiv—B9—O9110.2 (4)
O19—Sr4—O772.72 (9)O18—B9—O7110.4 (4)
O21—Sr4—O7145.82 (10)O19xiv—B9—O7104.4 (3)
O17—Sr4—O796.98 (10)O9—B9—O7109.2 (4)
O7ii—Sr4—O7100.68 (10)O19—B10—O18116.4 (4)
O2—Sr4—O770.49 (10)O19—B10—O11110.3 (4)
O12—Sr4—O772.05 (9)O18—B10—O11110.7 (4)
O1—Sr4—O7115.02 (10)O19—B10—O15ix111.6 (4)
O19—Sr4—O693.03 (10)O18—B10—O15ix102.4 (3)
O21—Sr4—O6159.89 (10)O11—B10—O15ix104.5 (3)
O17—Sr4—O649.69 (10)O21xiv—B11—O20116.5 (4)
O7ii—Sr4—O678.44 (10)O21xiv—B11—O14110.8 (4)
O2—Sr4—O668.12 (10)O20—B11—O14104.6 (4)
O12—Sr4—O6119.38 (10)O21xiv—B11—O12106.0 (4)
O1—Sr4—O6114.52 (9)O20—B11—O12109.2 (4)
O7—Sr4—O648.38 (9)O14—B11—O12109.7 (4)
O19—Sr4—O2ii118.18 (10)O20—B12—O21116.5 (4)
O21—Sr4—O2ii66.73 (10)O20—B12—O1111.7 (4)
O17—Sr4—O2ii48.74 (9)O21—B12—O1104.4 (4)
O7ii—Sr4—O2ii68.92 (9)O20—B12—O5xi109.0 (4)
O2—Sr4—O2ii96.96 (10)O21—B12—O5xi111.8 (4)
O12—Sr4—O2ii140.51 (9)O1—B12—O5xi102.5 (3)
O1—Sr4—O2ii73.46 (9)
Symmetry codes: (i) y, xy, z+1; (ii) x, y, z+1; (iii) x+y, x, z+1; (iv) x+y, x, z; (v) y, xy, z; (vi) y+1, xy, z; (vii) x+y+1, x+1, z; (viii) x+y+1, x+1, z+1; (ix) y+1, xy, z+1; (x) x+y, x+1, z+1; (xi) y+1, xy+1, z+1; (xii) x+y, x+1, z; (xiii) y+1, xy+1, z; (xiv) x, y, z1; (xv) x+y, x+1, z1; (xvi) x+y, x, z1; (xvii) y+1, xy+1, z1; (xviii) x+y+1, x+1, z1.

Experimental details

Crystal data
Chemical formulaSrB4O7
Mr242.86
Crystal system, space groupTrigonal, P3
Temperature (K)296
a, c (Å)17.145 (1), 4.2527 (5)
V3)1082.61 (16)
Z9
Radiation typeMo Kα
µ (mm1)11.19
Crystal size (mm)0.40 × 0.25 × 0.18
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 2004)
Tmin, Tmax0.095, 0.242
No. of measured, independent and
observed [I > 2σ(I)] reflections
10350, 3709, 3202
Rint0.054
(sin θ/λ)max1)0.676
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.030, 0.064, 0.85
No. of reflections3709
No. of parameters265
Δρmax, Δρmin (e Å3)1.02, 0.49
Absolute structureFlack (1983), 1836 Friedel pairs
Absolute structure parameter0.030 (7)

Computer programs: SMART (Bruker, 2001), SAINT-Plus (Bruker, 2001), SHELXTL (Sheldrick, 2008).

 

Acknowledgements

We thank the State Program for Support of Leading Scientific Schools (grant LS-4645.2010.2.)

References

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