High-pressure synthesis and structural characterization of three new polyphosphides, α-SrP3, BaP8, and LaP5

Three novel metal polyphosphides, alpha-SrP3, BaP8, and LaP5, were prepared in BN crucibles by the reaction of the respective stoichiometric mixtures under a high pressure of 3 GPa at 950-1000degreesC. Their crystal structures were determined from single-crystal X-ray data (alpha-SrP3: space group C2/m, a = 9.199(6) Angstrom, b = 7.288(3) Angstrom, c = 5.690(3) Angstrom, beta = 113.45(4)degrees, Z = 4 R(1/)wR(2) = 0.0684/0.1180 for 471 observed reflections and 22 variables; BaP8: space group P- 1, a = 6.762(2) Angstrom, b = 7.233(2) Angstrom, c = 8.567(2) Angstrom, alpha = 86.32(2)degrees, beta = 84.31(2)degrees, gamma = 70.40(2)degrees, Z = 2, R-1/wR(2) = 0.0476/0.1255 for 2702 observed reflections and 82 variables; LaP5: space group P2(1)/m, a = 4.885(1)Angstrom, b = 9.673(3) Angstrom, c = 5.577(2) Angstrom, beta = 105.32(2)degrees, Z = 2, R-1/wR(2) = 0.0391/0.1034 for 1272 observed reflections and 31 variables). alpha-SrP3 is isostructural with SrAs3 and the crystal structure consists of two-dimensional puckered polyanionic layers (2)(alpha) [P-3](2-) that stack along the c-axis yielding channels occupied by Sr2+ counterions. BaP8 crystallizes in a new structure type which contains a three-dimensional infinite polyanionic framework (3)(infinity) [P-3](2-) with large channels hosting the barium cations. LaP5 is a layered compound containing (2)(infinity) [P-5](3-) polyanionic layers separated by La3+ ions. All three compounds exhibit expected diamagnetic behaviors. (C) 2003 Elsevier Science (USA). All rights reserved.