Metal-Rich Phosphides Obtained from the Lead Flux: Synthesis, Crystal, and Electronic Structure of Sr₅Pt₁₂P₉ and BaPt₃P₂

Abstract

Using a high-temperature ampoule technique and lead metal as a flux, we have grown single crystals and determined crystal structures from single-crystal X-ray diffraction data of two metal-rich phosphides, Sr5Pt12P9 (P 2 1/m, a = 6.1472(3) Å, b = 25.1713(13) Å, c = 6.4635(3) Å, β = 99.604(2)°, Z = 2, R 1 = 0.0326, wR 2 = 0.0786) and BaPt3P2 (P 212121 , a = 6.3605(6) Å, b = 6.8541(7) Å, c = 11.3493(12) Å, Z = 4, R 1 = 0.0231, wR 2 = 0.0501). Both compounds belong to their own structure types and feature 3D networks of Pt and P atoms, with the channels occupied by alkaline earth metal cations. Density functional theory calculations reveal Sr5Pt12P9 to be a metal, while BaPt3P2 is a narrow-gap semiconductor with a band gap of 0.24 eV. Bonding analysis shows that both compounds feature networks of prominent covalent localized Pt–P bonds, responsible for their structural stability, as well as additional weaker and, likely, less localized Pt–Pt interactions.

Merging the AuCu3- and BaAl4-based structure motifs: flux-assisted synthesis, crystal, and electronic structure of Ca2Pt7XP4−δ phosphide platinides (X = Al, Ti, and Zn)

“…Such charge distribution picture confirms our description of the compounds in question as "phosphide platinides" rather than simply "phosphides". It must be noted that this picture of charge distribution is rather closely matched in the compounds like BaPt 3 P 2 , Sr 5 Pt 12 P 9 , 32 and Pt 5 ZnP, Pd 5 InAs, 3 as in all these compounds pnictogen atoms carry noticeably smaller negative charges (if at all) as compared to the group 10 metal negative charge.…”

“…Notably, in the case of compounds containing platinum metals, the use of tin is compromised, since platinum metals are known to form very stable stannides, and thus the use of lead flux gives the best results. 31 For example, crystals of Sr 5 Pt 12 P 9 , BaPt 3 P 2 , 32 Sm 15 Ir 33 P 26 , 33 Ca 2 Ir 12 P 7 , Ca 5 M 19 P 12 (M = Rh, Ir) 34 were obtained using lead as a flux. Therefore, for the synthesis of the Eu 2 Pt 7 AlP 2.95 -type compounds, lead was the flux of our choice.…”