American Chemical Society
ic6b01587_si_002.cif (1.62 MB)
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Lead Oxychloride Borates Obtained under Extreme Conditions

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posted on 2016-08-25, 13:52 authored by Oleg I. Siidra, Houria Kabbour, Olivier Mentre, Evgeny V. Nazarchuk, Philip Kegler, Diana O. Zinyakhina, Marie Colmont, Wulf Depmeier
[Pb10O4]­Pb2(B2O5)­Cl12 (1) and [Pb18O12]­Pb­(BO2OH)2Cl10 (2) were obtained via high-temperature high-pressure experiments. [O12Pb18]12+ and [O4Pb10]12+ oxocentered structural units of different dimensionality are excised from the ideal [OPb] layer in tetragonal α-PbO. 2 is formed with an excess of lead oxide component, and 1 is formed with an excess of borate and halide reagents. The structure of 2 can be visualized as the incorporation of {Pb(10)­Cl4(BO2OH)2} clusters into alternating PbO and chloride layers, with the existence of square vacancies in both. However, the structure of 1 is described as the intrusion of [O4Pb10]12+ tetramers linked by disordered Pb­(B2O5) groups into a halogen three-dimensional matrix. The structure of 2 contains 10 symmetrically independent Pb positions. The 6s2 lone electron pair is stereochemically active on Pb(1)–Pb(9) atoms, whereas it is inert on Pb(10). All of the Pb coordinations in the structure of 2, in accordance with ECCv (volume eccentricity) parameters and the density of states (DOS), can be subdivided into three groups. The current study is the first attempt to analyze this unusual behavior in structurally complex oxyhalide material with the rare case of Pb2+ cations, demonstrating both stereochemically active and inactive behavior of the lone pair via charge and first-principle calculations.