Synthesis and structure determinantion of the first lead arsenide phosphide Pb₂As _x P_14–x (x ~ 3.7)

Abstract

Pb2AsxP14–x was synthesized by reacting the pnicogens in a lead melt in sealed silica ampoules. A mixture of hydrogen peroxide and glacial acetic acid removed lead from the final product. Pb2AsxP14–x represents the first lead arsenide phosphide adopting a new structure type. Systematic substitution of phosphorus by arsenic leads to the formation of Pb2AsxP14–x with x ~ 3.7, a compound with a two-dimensional arrangement of polypnictide layers, coordinated by Pb2+ cations. Pb2AsxP14–x is structurally related to PbP7 where a three-dimensional polyphosphide network is realized instead. The structure of Pb2As3.7(1)P10.3(1) was determined from single crystal X-ray diffraction data: space group P212121 (no. 19), a = 10.060(1), b = 10.500(1), c = 13.711(2) Å, and V = 1448.3(4) Å3. The structure is discussed relative to PbP7 focusing on the differences in the polyanionic substructures of the two polypnictides.