Reinvestigation of the Pb2[B5O9]Br structure based on single crystal data

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Acta Crystallographica Section E

Structure Reports

Online ISSN 1600-5368

Reinvestigation of the Pb

2

[B

5

O

9

]Br structure

based on single-crystal data

Olga V. Yakubovich,a_*

Natalya N. Mochenova,a

Olga. V. Dimitrovaa_and

Werner Massab_*

a_{Department of Geology, Moscow Lomonosov} State University, Vorob'evy Gory, 119899 Moscow, Russia, andb_{Department of Chemistry} and Materials Science Center, Philipps-University, D-35032 Marburg, Germany

Correspondence e-mail: [email protected], [email protected]

Key indicators Single-crystal X-ray study

T= 293 K

Mean(O±B) = 0.019 AÊ

Rfactor = 0.034

wRfactor = 0.080

Data-to-parameter ratio = 29.2

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

The structure of the title pentaborate, [Pb2(B5O9)Br] (dilead pentaborate bromide), known from powder data, has been re®ned based on single-crystal data (R = 0.034) and is discussed in terms of intercrossing anionic and cationic frameworks.

Comment

The mineral family of hilgardite includes three polymorphs with the common formula Ca2[B5O9]ClH2O (triclinic phases 1A and parahilgardite, and monoclinic hilgardite-4M), tyretskite Ca2[B5O9]OHH2O (Strunz & Nickel, 2001), that seems to be isotypic with hilgardite-1A (Ghose, 1985), and kurgantaite CaSr[B5O9]ClH2O (Pekov et al., 2001). Sr occupies one of two independent Ca positions of hilgardite-1A in the crystal structure of kurgantaite (Ferro, Pushcharovskiiet al., 2000). Several synthetic compounds of composition

M2+

2 [B5O9]X(M= Ca, Sr, Ba, Eu, Pb andX = Cl, Br) have been obtained during attempts to prepare boracite-type structures (Fouassieret al., 1971; Peters & Baglio, 1970). The crystal structure investigation of the calcium (Ca2[B5O9]Br; Lloydet al., 1973) and europium (Eu2[B5O9]Cl; Machidaet al., 1981) members of this group revealed their orthorhombic symmetry (space groupPnn2) and a close relationship to the hilgardite structure type. Zeolite-like construction and piezoelectric properties have been noted earlier for hilgardites (Ghose & Wan, 1979; Ghose, 1982; Wan & Ghose, 1983). According to Ghose & Wan (1979), hilgardite was successfully tested for second harmonic generation and gives piezoelectric signals comparable to quartz. Blue emission at about 430 and 435 nm was established for Eu2[B5O9]Br and Eu2[B5O9]Cl (Machidaet al., 1981), noting that their Eu2+_{activated alkaline} earth analogues are ef®cient phosphors.

The crystal structure of an orthorhombic synthetic Ba variety in the hilgardite structure group, Ba2[B5O9]Cl0.5H2O, was reported by Ferro, Merlinoet al.(2000) and two more

Pb-Received 26 August 2004 Accepted 20 September 2004 Online 9 October 2004

Figure 1

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containing phases in the hilgardite family, Pb2[B5O9]OHH2O (monoclinic, P21/n) (Belokoneva et al., 1998), viz. the lead formula analogue of tyretskite and Na0.5Pb2[B5O9]Cl(OH)0.5 (orthorhombic, Pnn2; Belokoneva et al., 2000), have been synthesized and studied in recent years. The crystal structure of an orthorhombic compound Pb2[B5O9]Br (Fouassieret al., 1971) was solved by Belokonevaet al.(2003) based on powder data. The present paper reports the results of an improved re®nement of this structure based on single-crystal diffraction data and a discussion of the structure in terms of intercrossing frameworks.

The cell parameters determined from 4734 single-crystal re¯ections deviate signi®cantly from the reported powder data, the a parameter being 0.03 AÊ smaller and b 0.04 AÊ larger. This is surely due to the pseudotetragonal metrics. In the single-crystal data, errors are induced by the observed twinning. As the ®rst domain dominates by 70%, the resulting lattice constantsaandbwill approach the correct values but become too nearly equal. In Rietveld re®nements, the pseudo-tetragonal metrics (overlap ofhklandkhlre¯ections) will lead to correlations with the pro®le function that may also in¯u-ence thea±b difference. As thecaxis differs also by 0.01 AÊ (10) between single-crystal and powder work, we decided to use the single-crystal cell constants for the re®nement. The difference in bond lengths calculated with both cells has been proved to be less than 0.01 AÊ.

The precision of bond lengths and angles derived from the single-crystal data is remarkably improved with respect to the powder work. The s.u. values of the PbÐO bonds, for instance, ranging in the latter between 0.03 and 0.08 AÊ, are between 0.009 and 0.013 AÊ in the present work. The absolute differ-ences in bond lengths obtained by the different methods are up to 0.08 AÊ in the PbÐO bonds and 0.10 AÊ in the BÐO bonds. In all cases of large differences, the new values appear more sensible. The discussion of correlations of non-linear optical properties and the coordination geometry of Pb can, therefore, refer to a more reliable basis.

As shown in Fig. 1, three [BO4] tetrahedra and two [BO3] triangular groups form a basic fragment [B5O12] of the anionic framework. This fragment can be interpreted as a combination of two three-membered boron-oxygen rings as found in the structures of the dimorphic minerals inderite and kurnakovite Mg[B3O3(OH)5]5H2O (Rumanova, 1971). These rings are

formed by two [BO4] tetrahedra and one [BO3] triangle sharing oxygen vertices. The vertices of the tetrahedra are directed to one side from the plane of the `inderite' ring (B1/ B2/B5) and to different sides from the plane of the `kurna-kovite' ring (B1/B3/B4). The BÐO distances in the triangular con®guration range from 1.34 (2) to 1.38 (2) AÊ. The BÐO distances in the tetrahedra are, as usual, larger and lie in the range 1.42 (2)±1.52 (2) AÊ, with the same average value of 1.48 AÊ for all three independent tetrahedra.

The O2ÿ_{and Br}ÿ_{anions form large nine-vertex polyhedra}

around two independent Pb2+_{cations, with Pb1ÐO distances} between 2.497 (13) and 3.076 (11) AÊ, and Pb2ÐO distances between 2.475 (9) and 3.010 (10) AÊ. The PbÐBr distances vary between 2.998 (2) and 3.055 (1) AÊ in the Pb1 polyhedron, and the Pb2ÐBr bond lengths between 3.056 (1) and 3.153 (2) AÊ. The average PbÐO(Br) distances coincide for both polyhedra and are 2.81 AÊ. These polyhedra can be described as distorted bipyramids with a hexagonal basis formed by O atoms and two apical vertices occupied by Br, similar to the Ca environment in Ca2[B5O9]Br (Lloydet al., 1973). The ninth ligands (O6 at Pb1 and O9 at Pb2) complicate the Pb bipyramids by capping a side plane (Fig. 2). Their PbÐ O distances are in the range of PbÐBr bond lengths.

The PbÐO distances in each polyhedron divide into two groups. Rather strong Pb±O bonds, corresponding to the criterion of the sum of ionic radii, lie between 2.497 (13) and 2.686 (9) AÊ at Pb1, and between 2.475 (10) and 2.695 (11) AÊ at Pb2 (dark in Fig. 2). O atoms forming these bonds are placed preferentially on one side of the Pb2+ _{cations. For Pb1, the} orientation of the short bonds is concentrated on the left side in Fig. 2a. For Pb2, an umbrella-like coordination is observed with the short Pb2ÐBr2 bond as handle (Fig. 2b). The oxygen ligands at longer distances [2.798 (10)±3.076 (11) AÊ from Pb1 and 2.838 (13)±3.010 (10) AÊ from Pb2] are mainly on the opposite side. Thus, the active lone pairs of the Pb2+_{ions might} be directed towards this side,i.e. approximately in the [011]

inorganic papers

i128

Olga V. Yakubovichet al. [Pb₂(B₅O₉)Br] Acta Cryst.(2004). E60, i127±i130

Figure 2

Coordination around Pb1 (a) and Pb2 (b). Short bonds are dark. Displacement ellipsoids are drawn at the 90% probability level.

Figure 3

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direction for the Pb1 and the [010] direction for the Pb2 polyhedron, respectively. The high non-linearity of the compound mentioned by Belokoneva et al. (1998) can be related to this asymmetric distribution of the electron density around the Pb atoms.

The crystal structure of Pb2[B5O9]Br can be considered as a combination of two different frameworks: the tetrahedral [BO4] and trigonal [BO3] units form a zeolite-like anionic framework of composition [B5O9]3ÿ by sharing common vertices, as discussed before. This framework can also be interpreted as formed by polar chains of [BO4] tetrahedra along the c axis that are joined together by [BO3] triangles along the a and b axes (Fig. 3). Regarding the PbÐBr substructure only, a second anticristobalite-like cationic [BrPb2]3+ framework can be identi®ed, built from strongly ¯attened [BrPb4] tetrahedra sharing vertices (Fig. 4). This is inserted into the large pores of the anionic borate framework (Fig. 5).

Experimental

Transparent colourless very small (maximum 0.1 mm long) crystals of prismatic shape were grown by soft hydrothermal synthesis in the system PbOÐB2O3ÐKBrÐH2O [T = 553 K, P = 70 bar (1 bar =

105_Pa),_t_{= 20 d, PbOÐB}

2O3ÐKBr ratio = 1:1:1] in 7 ml Cu tubes in a

steel autoclave. The presence of Pb and Br in the samples was con®rmed by qualitative X-ray spectral analysis (CamScan 4DV + EDA Link AN 1000).

Crystal data [Pb2(B5O9)Br]

Mr= 692.34 Orthorhombic,Pnn2 a= 11.4935 (19) AÊ b= 11.4717 (19) AÊ c= 6.5297 (11) AÊ V= 860.9 (2) AÊ3

Z= 4

Dx= 5.341 Mg mÿ3

MoKradiation Cell parameters from 4734

re¯ections

= 3.5±36.0 = 43.73 mmÿ1

T= 293 (2) K Column, colourless 0.130.030.02 mm

Data collection

Stoe IPDS-II diffractometer

!scans

Absorption correction: numerical (XPREPinSHELXTL; Sheldrick, 1996). Tmin= 0.093,Tmax= 0.387

7497 measured re¯ections

2544 independent re¯ections 2429 re¯ections withI> 2(I) Rint= 0.068

max= 31.0

h=ÿ12!16 k=ÿ16!16 l=ÿ8!9 Refinement

Re®nement onF2

R[F2_{> 2}₍_F2_{)] = 0.034}

wR(F2_{) = 0.080}

S= 1.06 2544 re¯ections 87 parameters w= 1/[2₍_F

o2) + (0.0337P)2 + 13.5461P]

whereP= (Fo2+ 2Fc2)/3

(/)max< 0.001 max= 1.96 e AÊÿ3 min=ÿ2.13 e AÊÿ3

Extinction correction:SHELXL97 Extinction coef®cient: 0.00036 (10) Absolute structure: Flack (1983),

1059 Friedel pairs Flack parameter =ÿ0.03 (2)

Table 1

Selected geometric parameters (AÊ,_).

Pb1ÐO5i _{2.497 (13)}

Pb1ÐO2i _{2.534 (12)}

Pb1ÐO3 2.659 (11) Pb1ÐO1i _{2.686 (9)}

Pb1ÐO7ii _{2.798 (10)}

Pb1ÐO9ii _{2.975 (11)}

Pb1ÐBr2i _{2.9977 (16)}

Pb1ÐBr1ii _{3.0554 (10)}

Pb1ÐO6ii _{3.076 (11)}

Pb2ÐO7 2.475 (10) Pb2ÐO8iii _{2.571 (11)}

Pb2ÐO1 2.647 (9) Pb2ÐO6iv _{2.695 (11)}

Pb2ÐO4 2.838 (13) Pb2ÐO9 2.864 (11) Pb2ÐO3iii _{3.010 (10)}

Pb2ÐBr2 3.0559 (8) Pb2ÐBr1 3.153 (2)

B1ÐO1 1.470 (18) B1ÐO5 1.48 (2) B1ÐO6 1.485 (18) B1ÐO7 1.473 (18) B2ÐO2 1.468 (19) B2ÐO3 1.504 (19) B2ÐO4 1.450 (19) B2ÐO7ii _{1.50 (2)}

B3ÐO1 1.453 (19) B3ÐO3 1.417 (19) B3ÐO8 1.516 (19) B3ÐO9 1.52 (2) B4ÐO4v _{1.358 (19)}

B4ÐO6 1.34 (2) B4ÐO8 1.35 (2) B5ÐO2 1.38 (2) B5ÐO5ii _{1.36 (2)}

B5ÐO9vi _{1.358 (19)}

O1ÐB1ÐO7 109.5 (11) O1ÐB1ÐO5 104.2 (12) O7ÐB1ÐO5 110.3 (12) O1ÐB1ÐO6 111.4 (12) O7ÐB1ÐO6 109.6 (12) O5ÐB1ÐO6 111.7 (11) O4ÐB2ÐO2 109.9 (13) O4ÐB2ÐO7ii _{110.4 (12)}

O2ÐB2ÐO7ii _{110.4 (14)}

O4ÐB2ÐO3 108.8 (13) O2ÐB2ÐO3 110.5 (12) O7ii_ÐB2ÐO3 _{106.7 (12)}

O3ÐB3ÐO1 115.8 (13) O3ÐB3ÐO8 105.0 (12) O1ÐB3ÐO8 110.3 (12) O3ÐB3ÐO9 114.8 (13) O1ÐB3ÐO9 103.7 (11) O8ÐB3ÐO9 107.0 (11) O6ÐB4ÐO8 121.9 (13) O6ÐB4ÐO4v _{114.5 (17)}

O8ÐB4ÐO4v _{123.4 (16)}

O5ii_ÐB5ÐO9vi _{121.1 (15)}

O5ii_ÐB5ÐO2 _{120.3 (14)}

O9vi_ÐB5ÐO2 _{118.7 (15)}

Symmetry codes: (i) 1

2ÿx;yÿ12;12z; (ii) x;y;1z; (iii) xÿ12;21ÿy;zÿ12; (iv)

xÿ1

2;12ÿy;12z; (v)12x;12ÿy;zÿ12; (vi)12ÿx;12y;12z. Figure 4

The cationic framework [Pb2Br]3+.

Figure 5

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The structure was re®ned as a pseudomerohedral (110) twin [twin ratio 0.688 (2):0.312 (2)] to residuals wR2 = 0.0803 (for all 2544

re¯ections) andR= 0.0344 [for 2429 re¯ections >2(I)] with aniso-tropic displacement parameters for Pb and Br atoms. The strong tetragonal pseudosymmetry of the structure and pseudomerohedral twinning of the studied crystal did not allow for re®nement of anisotropic displacement parameters for the O and B atoms, in view of the very high scattering power of Pb and Br. A Flack (1983) parameter ofx=ÿ0.03 (2) con®rms the correct choice of the absolute polarity of this crystal. The maximum residual electron density is located 1.70 AÊ from Pb1 and the minimum 0.64 AÊ from Pb1. The same atomic labelling scheme has been used as in the powder work of Belokoneva et al. (2003), with z parameters inverted. For better comparison, negativezvalues were retained.

Data collection: X-AREA (Stoe & Cie, 2002); cell re®nement:

X-AREA; data reduction: X-AREA; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to re®ne structure: SHELXL97 (Sheldrick, 1997); molecular graphics:

DIAMOND (Crystal Impact, 2000); software used to prepare material for publication:SHELXL97.

We thank Elena V. Guseva from Moscow State Lomonosov University for the X-ray spectral analysis of the samples. The ®nancial support of Deutscher Akademischer Auslandsdienst is gratefully acknowledged (OVY), as well as that of the Russian Foundation for Basic Research (grant No. 02-03-33316) (NNM and OVD).

References

Belokoneva, E. L., Dimitrova, O. V., Korchemkina, T. A. & Stefanovich, S. Yu. (1998).Crystallogr. Rep.43, 864±873.

Belokoneva, E. L., Kabalov, Yu. K., Dimitrova, O. V. & Stefanovich, S. Yu. (2003).Crystallogr. Rep.48, 44±48.

Belokoneva, E. L., Korchemkina, T. A., Dimitrova, O. V. & Stefanovich, S. Yu. (2000).Crystallogr. Rep.45, 744±753.

Crystal Impact (2000).DIAMOND.Release 2.1.d. Crystal Impact GmbH, D-53002 Bonn, Germany.

Ferro, O., Merlino, S., Vinogradova, S. A., Pushcharovskii, D. Yu. & Dimitrova, O. V. (2000).J. Alloys Compd,305, 63±71.

Ferro, O., Pushcharovskii, D. Yu., Teat, S., Vinogradova, S. A., Lovskaya, E. V. & Pekov, I. V. (2000).Crystallogr. Rep.45, 410±415.

Flack, H. D. (1983).Acta Cryst.A39, 876±881.

Fouassier, C., Levasseur, A. & Hagenmuller, P. (1971).J. Solid State Chem.3, 206±212.

Ghose, S. (1982).Am. Mineral.67, 1265±1272. Ghose, S. (1985).Am. Mineral.70, 636±637.

Ghose, S. & Wan, C. (1979).Am. Mineral.64, 187±195.

Lloyd, D. J., Levasseur, A. & Fouassier, C. (1973).J. Solid State Chem.6, 179± 186.

Machida, K.-I., Adachi, G.-Y., Moriwaki, Y. & Shiokawa, J. (1981).Bull. Chem. Soc. Jpn,54, 1048±1051.

Pekov, I. V., Lovskaya, E. V., Chukanov, N. V., Zadov, A. E., Apollonov, V. N., Pushcharovskii, D. Yu., Ferro, O. & Vinogradova S. A. (2001).Proc. RMS,3, 71±79.

Peters, T. E. & Baglio, J. (1970).J. Inorg. Nucl. Chem.32, 1089±1096. Rumanova, I. M. (1971).Kristallogra®ya,16, 1157±1160.

Sheldrick, G. M. (1996).SHELXTL.Version 5.03. Siemens Analytical X-ray Instruments Inc., Madison, Wisconsin, USA.

Sheldrick, G. M. (1997). SHELXS97 and SHELXL97. University of GoÈttingen, Germany.

Stoe & Cie (2002).X-AREA. Stoe & Cie, Darmstadt, Germany.

Strunz, H. & Nickel, E. H. (2001).Strunz Mineralogical Tables. Stuttgart: E. Schweizerbart'sche Verlagsbuchhandlung.

Wan, C. & Ghose, S. (1983).Am. Mineral.68, 604±613.

inorganic papers

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sup-1 Acta Cryst. (2004). E60, i127–i130

supporting information

Acta Cryst. (2004). E60, i127–i130 [https://doi.org/10.1107/S1600536804023232]

Reinvestigation of the Pb

2

[B

5

O

9

]Br structure based on single-crystal data

Olga V. Yakubovich, Natalya N. Mochenova, Olga. V. Dimitrova and Werner Massa

Dilead pentaborate bromide

Crystal data [Pb2(B5O9)Br]

Mr = 692.34

Orthorhombic, Pnn2 Hall symbol: P 2 -2n a = 11.4935 (19) Å b = 11.4717 (19) Å c = 6.5297 (11) Å V = 860.9 (2) Å3

Z = 4

F(000) = 1184 Dx = 5.341 Mg m−3

Mo Kα radiation, λ = 0.71073 Å Cell parameters from 4734 reflections θ = 3.5–36.0°

µ = 43.73 mm−1

T = 293 K

Column, colourless 0.13 × 0.03 × 0.02 mm

Data collection Stoe IPDS-II

diffractometer

Radiation source: fine-focus sealed tube Graphite monochromator

Detector resolution: 150 pixels mm-1

ω scans

Absorption correction: numerical

(XPREP in SHELXTL; Sheldrick, 1996). Tmin = 0.093, Tmax = 0.387

7497 measured reflections 2544 independent reflections 2429 reflections with I > 2σ(I) Rint = 0.068

θmax = 31.0°, θmin = 3.6°

h = −12→16 k = −16→16 l = −8→9

Refinement Refinement on F2

Least-squares matrix: full R[F2_{> 2}_σ₍_F2_{)] = 0.034}

wR(F2_{) = 0.080}

S = 1.06 2544 reflections 87 parameters 1 restraint

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

w = 1/[σ2₍_F

o2) + (0.0337P)2 + 13.5461P]

where P = (Fo2 + 2Fc2)/3

(Δ/σ)max < 0.001

Δρmax = 1.96 e Å−3

Δρmin = −2.13 e Å−3

Extinction correction: SHELXL97, Fc*_{=kFc[1+0.001xFc}2_λ3_/sin(2_θ_)]-1/4

Extinction coefficient: 0.00036 (10)

Absolute structure: Flack (1983), 1059 Friedel pairs

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supporting information

Special details

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 as pseudomerohedral (110) twin, twin ratio 31.2 (2)%. 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₎

x y z Uiso*/Ueq

Pb1 0.25762 (6) 0.04280 (6) 0.00433 (9) 0.01489 (12) Pb2 0.02631 (6) 0.23505 (5) −0.66205 (14) 0.01614 (13) Br1 0.0000 0.0000 −0.9081 (5) 0.0289 (6) Br2 0.0000 0.5000 −0.6476 (6) 0.0259 (5) O1 0.2376 (8) 0.3135 (8) −0.5784 (14) 0.0030 (16)* O2 0.2084 (8) 0.4248 (8) −0.173 (2) 0.0108 (16)* O3 0.2717 (8) 0.2256 (9) −0.2448 (16) 0.0079 (19)* O4 0.0686 (11) 0.2753 (11) −0.2398 (19) 0.017 (2)* O5 0.2790 (9) 0.4487 (11) −0.835 (2) 0.015 (2)* O6 0.3827 (9) 0.2616 (9) −0.8357 (17) 0.0092 (18)* O7 0.1785 (8) 0.2698 (9) −0.9231 (15) 0.0046 (16)* O8 0.4168 (8) 0.2110 (9) −0.4921 (18) 0.0090 (16)* O9 0.2339 (9) 0.1103 (10) −0.5577 (16) 0.0106 (19)* B1 0.2706 (13) 0.3217 (14) −0.795 (2) 0.008 (3)* B2 0.1803 (13) 0.3009 (14) −0.146 (3) 0.012 (3)* B3 0.2864 (14) 0.2180 (15) −0.460 (2) 0.010 (3)* B4 0.4556 (13) 0.2354 (16) −0.683 (3) 0.011 (3)* B5 0.2513 (15) 0.4950 (14) −0.019 (3) 0.009 (3)*

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Pb1 0.0172 (2) 0.0170 (2) 0.0105 (2) 0.0011 (2) 0.0010 (2) 0.0004 (3) Pb2 0.0187 (2) 0.0179 (2) 0.0118 (3) −0.0013 (2) 0.0034 (3) 0.0000 (3) Br1 0.0202 (12) 0.0154 (10) 0.0511 (19) −0.0011 (10) 0.000 0.000 Br2 0.0188 (11) 0.0179 (10) 0.0411 (16) 0.0002 (8) 0.000 0.000

Geometric parameters (Å, º)

Pb1—O5i _{2.497 (13)} _O1—Pb1viii _{2.686 (9)}

Pb1—O2i _{2.534 (12)} _B2—O2 _{1.468 (19)}

Pb1—O3 2.659 (11) B2—O3 1.504 (19)

Pb1—O1i _{2.686 (9)} _B2—O4 _{1.450 (19)}

Pb1—O7ii _{2.798 (10)} _B2—O7ii _{1.50 (2)}

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Pb1—Br2 2.9977 (16) B3—O1 1.453 (19)

Pb1—Br1ii _{3.0554 (10)} _B3—O3 _{1.417 (19)}

Pb1—O6ii _{3.076 (11)} _B3—O8 _{1.516 (19)}

Pb1—B5i _{3.160 (19)} _B3—O9 _{1.52 (2)}

Pb2—O7 2.475 (10) B4—O4x _{1.358 (19)}

Pb2—O8iii _{2.571 (11)} _B4—O6 _{1.34 (2)}

Pb2—O1 2.647 (9) B4—O8 1.35 (2)

Pb2—O6iv _{2.695 (11)} _B5—O2 _{1.38 (2)}

Pb2—O4 2.838 (13) B5—O5ii _{1.36 (2)}

Pb2—O9 2.864 (11) B5—O9xi _{1.358 (19)}

Pb2—O3iii _{3.010 (10)} _O3—Pb2xii _{3.010 (10)}

Pb2—Br2 3.0559 (8) O4—B4iv _{1.358 (19)}

Pb2—B1 3.104 (15) O5—B5vi _{1.36 (2)}

Pb2—Br1 3.153 (2) O5—Pb1viii _{2.497 (13)}

Br1—Pb1v _{3.0554 (10)} _O6—Pb2x _{2.695 (11)}

Br1—Pb1vi _{3.0554 (10)} _O6—Pb1vi _{3.076 (11)}

Br1—Pb2vii _{3.1532 (19)} _O7—B2vi _{1.50 (2)}

Br2—Pb1viii _{2.9977 (16)} _O7—Pb1vi _{2.798 (10)}

Br2—Pb1iii _{2.9977 (16)} _O8—Pb2xii _{2.571 (11)}

Br2—Pb2ix _{3.0559 (8)} _O9—B5xiii _{1.358 (19)}

B1—O1 1.470 (18) O9—Pb1vi _{2.975 (11)}

B1—O5 1.48 (2) B1—Pb1viii _{3.220 (16)}

B1—O6 1.485 (18) B4—Pb2x _{3.25 (2)}

B1—O7 1.473 (18) B5—Pb1viii _{3.160 (19)}

O5i_—Pb1—O2i _{122.1 (4)} _{B2—O3—Pb1} _{98.6 (9)}

O5i_—Pb1—O3 _{79.0 (4)} _{B3—O3—Pb2}xii _{94.1 (8)}

O2i_—Pb1—O3 _{157.0 (3)} _{B2—O3—Pb2}xii _{121.1 (8)}

O5i_—Pb1—O1i _{53.3 (3)} _{Pb1—O3—Pb2}xii _{93.9 (3)}

O2i_—Pb1—O1i _{68.9 (3)} _B4iv_—O4—B2 _{138.5 (15)}

O3—Pb1—O1i _{130.4 (3)} _B4iv_—O4—Pb2 _{95.0 (11)}

O5i_—Pb1—O7ii _{119.8 (3)} _{B2—O4—Pb2} _{126.4 (10)}

O2i_—Pb1—O7ii _{114.0 (3)} _B5vi_—O5—B1 _{121.5 (13)}

O3—Pb1—O7ii _{52.4 (3)} _B5vi_—O5—Pb1viii _{125.4 (10)}

O1i_—Pb1—O7ii _{162.2 (3)} _{B1—O5—Pb1}viii _{105.2 (9)}

O5i_—Pb1—O9ii _{161.5 (3)} _B4—O6—B1 _{121.0 (13)}

O2i_—Pb1—O9ii _{49.8 (3)} _{B4—O6—Pb2}x _{102.2 (9)}

O3—Pb1—O9ii _{112.8 (3)} _{B1—O6—Pb2}x _{131.6 (9)}

O1i_—Pb1—O9ii _{116.8 (3)} _{B4—O6—Pb1}vi _{111.3 (10)}

O7ii_—Pb1—O9ii _{64.2 (3)} _{B1—O6—Pb1}vi _{91.9 (8)}

O5i_—Pb1—Br2i _{78.0 (3)} _Pb2x_—O6—Pb1vi _{91.7 (3)}

O2i_—Pb1—Br2i _{92.5 (2)} _B1—O7—B2vi _{116.3 (11)}

O3—Pb1—Br2i _{82.6 (2)} _{B1—O7—Pb2} _{100.6 (8)}

O1i_—Pb1—Br2i _{75.76 (19)} _B2vi_—O7—Pb2 _{135.8 (8)}

O7ii_—Pb1—Br2i _{120.7 (2)} _Pb1viii_—Br2—Pb2 _{94.66 (3)}

O9ii_—Pb1—Br2i _{116.5 (2)} _Pb1iii_—Br2—Pb2 _{86.52 (3)}

O5i_—Pb1—Br1ii _{86.2 (3)} _Pb1viii_—Br2—Pb2ix _{86.52 (3)}

(8)

supporting information

O3—Pb1—Br1ii _{107.5 (2)} _{Pb2—Br2—Pb2}ix _{176.46 (16)}

O1i_—Pb1—Br1ii _{84.26 (19)} _B3—O1—B1 _{117.5 (11)}

O7ii_—Pb1—Br1ii _{78.6 (2)} _{B3—O1—Pb2} _{102.0 (8)}

O9ii_—Pb1—Br1ii _{76.9 (2)} _{B1—O1—Pb2} _{93.4 (7)}

Br2i_—Pb1—Br1ii _{159.43 (5)} _{B3—O1—Pb1}viii _{128.5 (8)}

O2i_—Pb1—O6ii _{94.7 (3)} _{Pb2—O1—Pb1}viii _{113.1 (3)}

O3—Pb1—O6ii _{62.3 (3)} _B5—O2—B2 _{123.9 (14)}

O7ii_—Pb1—O6ii _{48.3 (3)} _{B2—O2—Pb1}viii _{130.6 (11)}

O9ii_—Pb1—O6ii _{60.3 (3)} _B3—O3—B2 _{122.8 (13)}

Br2i_—Pb1—O6ii _{79.1 (2)} _{B3—O3—Pb1} _{124.4 (10)}

Br1ii_—Pb1—O6ii _{121.4 (2)} _{B2—O3—Pb1} _{98.6 (9)}

O5i_—Pb1—B5i _{142.3 (4)} _{B3—O3—Pb2}xii _{94.1 (8)}

O2i_—Pb1—B5i _{25.1 (4)} _{B2—O3—Pb2}xii _{121.1 (8)}

O3—Pb1—B5i _{137.8 (4)} _{Pb1—O3—Pb2}xii _{93.9 (3)}

O1i_—Pb1—B5i _{91.6 (4)} _B4iv_—O4—B2 _{138.5 (15)}

O7ii_—Pb1—B5i _{89.1 (4)} _B4iv_—O4—Pb2 _{95.0 (11)}

O9ii_—Pb1—B5i _{25.3 (4)} _{B2—O4—Pb2} _{126.4 (10)}

Br2i_—Pb1—B5i _{109.1 (3)} _B5vi_—O5—B1 _{121.5 (13)}

Br1ii_—Pb1—B5i _{75.9 (3)} _B5vi_—O5—Pb1viii _{125.4 (10)}

O6ii_—Pb1—B5i _{79.8 (4)} _{B1—O5—Pb1}viii _{105.2 (9)}

O7—Pb2—O8iii _{74.3 (3)} _B4—O6—B1 _{121.0 (13)}

O7—Pb2—O1 55.9 (3) B4—O6—Pb2x _{102.2 (9)}

O8iii_—Pb2—O1 _{122.7 (3)} _{B1—O6—Pb2}x _{131.6 (9)}

O7—Pb2—O6iv _{167.2 (3)} _{B4—O6—Pb1}vi _{111.3 (10)}

O8iii_—Pb2—O6iv _{111.1 (3)} _{B1—O6—Pb1}vi _{91.9 (8)}

O1—Pb2—O6iv _{113.2 (3)} _Pb2x_—O6—Pb1vi _{91.7 (3)}

O7—Pb2—O4 121.4 (3) B1—O7—B2vi _{116.3 (11)}

O8iii_—Pb2—O4 _{149.2 (3)} _{B1—O7—Pb2} _{100.6 (8)}

O1—Pb2—O4 65.6 (3) B2vi_—O7—Pb2 _{135.8 (8)}

O6iv_—Pb2—O4 _{48.3 (3)} _{B1—O7—Pb1}vi _{103.8 (8)}

O7—Pb2—O9 69.8 (3) B2vi_—O7—Pb1vi _{93.0 (7)}

O8iii_—Pb2—O9 _{136.7 (3)} _{Pb2—O7—Pb1}vi _{101.3 (3)}

O1—Pb2—O9 49.9 (3) B4—O8—B3 116.3 (12)

O6iv_—Pb2—O9 _{109.2 (3)} _{B4—O8—Pb2}xii _{124.1 (9)}

O4—Pb2—O9 73.0 (4) B3—O8—Pb2xii _{110.8 (8)}

O7—Pb2—O3iii _{122.7 (3)} _B5xiii_—O9—B3 _{131.8 (13)}

O8iii_—Pb2—O3iii _{48.5 (3)} _B5xiii_—O9—Pb2 _{129.5 (10)}

O1—Pb2—O3iii _{151.4 (3)} _{B3—O9—Pb2} _{91.4 (8)}

O6iv_—Pb2—O3iii _{62.9 (3)} _B5xiii_—O9—Pb1vi _{85.0 (9)}

O4—Pb2—O3iii _{108.5 (3)} _{B3—O9—Pb1}vi _{125.5 (8)}

O9—Pb2—O3iii _{158.0 (3)} _{Pb2—O9—Pb1}vi _{88.7 (3)}

O7—Pb2—Br2 86.1 (2) O1—B1—O7 109.5 (11) O8iii_—Pb2—Br2 _{74.8 (2)} _O1—B1—O5 _{104.2 (12)}

O1—Pb2—Br2 75.3 (2) O7—B1—O5 110.3 (12) O6iv_—Pb2—Br2 _{84.3 (2)} _O1—B1—O6 _{111.4 (12)}

(9)

O9—Pb2—Br2 124.9 (2) O5—B1—O6 111.7 (11) O3iii_—Pb2—Br2 _{76.1 (2)} _{O1—B1—Pb2} _{58.3 (6)}

O7—Pb2—B1 27.8 (4) O7—B1—Pb2 51.6 (6)

O8iii_—Pb2—B1 _{97.5 (4)} _{O5—B1—Pb2} _{115.0 (9)}

O1—Pb2—B1 28.2 (4) O6—B1—Pb2 133.3 (9) O6iv_—Pb2—B1 _{140.5 (4)} _{O1—B1—Pb1}viii _{55.9 (6)}

O4—Pb2—B1 93.8 (4) O7—B1—Pb1viii _{126.2 (9)}

O9—Pb2—B1 58.2 (4) O5—B1—Pb1viii _{48.5 (7)}

O3iii_—Pb2—B1 _{141.4 (4)} _{O6—B1—Pb1}viii _{124.1 (9)}

Br2—Pb2—B1 77.3 (3) Pb2—B1—Pb1viii _{89.4 (4)}

O7—Pb2—Br1 81.6 (2) O4—B2—O2 109.9 (13) O8iii_—Pb2—Br1 _{74.4 (2)} _O4—B2—O7ii _{110.4 (12)}

O1—Pb2—Br1 118.9 (2) O2—B2—O7ii _{110.4 (14)}

O6iv_—Pb2—Br1 _{110.9 (2)} _O4—B2—O3 _{108.8 (13)}

O4—Pb2—Br1 130.6 (3) O2—B2—O3 110.5 (12) O9—Pb2—Br1 76.9 (2) O7ii_—B2—O3 _{106.7 (12)}

O3iii_—Pb2—Br1 _{86.8 (2)} _{O4—B2—Pb1} _{100.7 (9)}

Br2—Pb2—Br1 148.95 (10) O2—B2—Pb1 149.2 (10) B1—Pb2—Br1 102.6 (3) O7ii_—B2—Pb1 _{59.5 (6)}

Pb1v_—Br1—Pb1vi _{158.42 (14)} _{O3—B2—Pb1} _{54.2 (7)}

Pb1v_—Br1—Pb2 _{109.01 (4)} _O3—B3—O1 _{115.8 (13)}

Pb1vi_—Br1—Pb2 _{82.24 (3)} _O3—B3—O8 _{105.0 (12)}

Pb1v_—Br1—Pb2vii _{82.24 (3)} _O1—B3—O8 _{110.3 (12)}

Pb1vi_—Br1—Pb2vii _{109.01 (4)} _O3—B3—O9 _{114.8 (13)}

Pb2—Br1—Pb2vii _{118.74 (11)} _O1—B3—O9 _{103.7 (11)}

Pb1viii_—Br2—Pb1iii _{141.35 (15)} _O8—B3—O9 _{107.0 (11)}

Pb1viii_—Br2—Pb2 _{94.66 (3)} _{O3—B3—Pb2} _{106.7 (9)}

Pb1iii_—Br2—Pb2 _{86.52 (3)} _{O1—B3—Pb2} _{52.3 (6)}

Pb1viii_—Br2—Pb2ix _{86.52 (3)} _{O8—B3—Pb2} _{148.2 (10)}

Pb1iii_—Br2—Pb2ix _{94.66 (3)} _{O9—B3—Pb2} _{61.0 (7)}

Pb2—Br2—Pb2ix _{176.46 (16)} _O6—B4—O8 _{121.9 (13)}

B3—O1—B1 117.5 (11) O6—B4—O4x _{114.5 (17)}

B3—O1—Pb2 102.0 (8) O8—B4—O4x _{123.4 (16)}

B1—O1—Pb2 93.4 (7) O6—B4—Pb2x _{54.1 (9)}

B3—O1—Pb1viii _{128.5 (8)} _{O8—B4—Pb2}x _{172.2 (11)}

B1—O1—Pb1viii _{97.2 (8)} _O4x_—B4—Pb2x _{60.4 (10)}

Pb2—O1—Pb1viii _{113.1 (3)} _O5ii_—B5—O9xi _{121.1 (15)}

B5—O2—B2 123.9 (14) O5ii_—B5—O2 _{120.3 (14)}

B5—O2—Pb1viii _{103.8 (9)} _O9xi_—B5—O2 _{118.7 (15)}

B2—O2—Pb1viii _{130.6 (11)} _O5ii_—B5—Pb1viii _{162.0 (11)}

B3—O3—B2 122.8 (13) O9xi_—B5—Pb1viii _{69.7 (9)}

B3—O3—Pb1 124.4 (10) O2—B5—Pb1viii _{51.1 (8)}