Ternary palladium-indium-phosphorus and platinum-indium-phosphorus compounds based on the Cu3Au-type: Structure, bonding, and properties

Two metal-rich compounds, Pd5InP and Pt5InP, were synthesized as phase-pure powders using a high-temperature ampoule technique. According to the Rietveld analysis, they crystallize in the fairly rare Pd5TlAs structure type (tetragonal system, P4/mmm space group, Pearson symbol tP7, with a = 3.9303(5) A, c = 6.9269(1) A, Z = 1, Rp = 0.029, Rb = 0.004 for Pd5InP, and a = 3.9500(1) A, c = 6.9814(3) A, Z = 1, Rp = 0.034, Rb = 0.005 for Pt5InP. For both compounds, main structural units are indium-centered [TM12In] cuboctahedra (TM=Pd, Pt), alternating along the c axis with [TM8P] rectangular prisms of the PtHg2 type. DFT electronic structure calculations and magnetic measurements indicate 3D metallic conductivity and diamagnetic behavior for both compounds. According to the bonding analysis based on the electron localizability indicator topology and charge density, both compounds are intermetallic in nature and feature four-centered interactions of the 3TM+In type between the transition metal and indium atoms in their heterometallic fragments, complemented in the case of platinum by Pt-Pt pairwise interactions. Both compounds do not show any significant hydrogen uptake up to pressures of ca. 7 MPa and temperatures of 700 K.