Crystals of lead oxobromide Pb
7O
4(OH)
4Br
2 have been synthesized by hydrothermal method. The structure of the new compound has been studied with X-ray single-crystal
diffraction analysis. The compound is monoclinic, space group
C112
1; unit-cell dimensions are
a = 5.852(4),
b = 13.452(7),
c = 19.673(9) Å, γ = 90.04°,
V = 1548.7(15) Å
3. The structure has been solved by direct methods and refined to
R
1 = 0.1138 for 1847 observed Pb
7O
4(OH)
4Br
2 unique reflections. The structure contains seven symmetrically independent bivalent Pb atoms. The coordination polyhedrons
of Pb are strongly distorted due to stereochemical activity of unshared electron pair 6
s
2. Oxygen atoms are tetrahedrally coordinated by four Pb
2+ cations with the formation of oxocentered tetrahedrons OPb
4. The compound is based on [O
2Pb
3]
2+ double chains formed by OPb
4 tetrahedrons. (OH)Pb
2 dimers combine the [O
2Pb
3]
2+ chains into 3D framework. Channels in the framework are parallel to [100] and are occupied by Br anions.
Original Russian Text © O.I. Siidra, S.V. Krivovichev, W. Depmeier, 2007, published in Zapiski Rossiiskogo Mineralogicheskogo
Obshchestva, 2007, Pt CXXXVI, No. 6, pp. 85–91.