Ternary palladium-indium-phosphorus and platinum-indium-phosphorus compounds based on the Cu 3 Au-type: Structure, bonding, and properties

Abstract Two metal-rich compounds, Pd 5 InP and Pt 5 InP, were synthesized as phase-pure powders using a high-temperature ampoule technique. According to the Rietveld analysis, they crystallize in the fairly rare Pd 5 TlAs structure type (tetragonal system, P 4 /mmm space group, Pearson symbol tP7, with a = 3.9303(5) A, c = 6.9269(1) A, Z  = 1, R p = 0.029, R b = 0.004 for Pd 5 InP, and a = 3.9500(1) A, c = 6.9814(3) A, Z  = 1, R p = 0.034, R b = 0.005 for Pt 5 InP. For both compounds, main structural units are indium-centered [TM 12 In] cuboctahedra (TM=Pd, Pt), alternating along the c axis with [TM 8 P] rectangular prisms of the PtHg 2 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.