A Russian Doll of Phosphide Platinides: Exploratory Synthesis, Crystal and Electronic Structure, and Magnetic Properties of the R6Pt30-xNi17+yP22 Compounds (R = Ca, Sr, Eu).

Based on the results of initial flux-assisted exploratory synthesis in the Eu-Pt-Ni-P system, three new quaternary R6Pt30-xNi17+yP22 compounds (R = Ca, Sr, Eu) were synthesized. According to the single-crystal XRD data, they crystallize in their own structure type (I4/mmm; a = 11.4716(4) Å, c = 16.2458(7) Å, R1 = 0.0386 (Ca6Pt27.1Ni19.8P22); a = 11.5784(5) Å, c = 16.2339(10) Å, R1 = 0.0305 (Sr6Pt27.7Ni19.2P22); a = 11.5882(5) Å, c = 16.3586(9) Å, R1 = 0.0273 (Eu6Pt28.8Ni18.1P22)), closely related to the Ce3Pt23Ge11 type. For the europium-containing compound, the structure was confirmed by the Rietveld refinement of the PXRD data from the bulk sample. The structure of the compounds is a complex 3D framework of nesting polyhedra, which, according to the DFT calculations and bonding analysis, is dominated by Pt-P and Ni-P bonds. According to the calculations, all the compounds are metallic. Magnetic measurements for Eu6Pt28.8Ni18.1P22 reveal it to be a soft ferromagnet with TC of ca. 4 K. These compounds represent the first quaternary compounds in the respective systems and the first examples of phosphorus-containing compounds with structures closely related to the Ce3Pt23Ge11 type.