Eu2Pt3Pb5 and SrPt2Pb4-lead-based intermetallics with Y2Rh3Sn5/NdRh2Sn4-type polyanionic platinum-lead 3D frameworks.

Two platinide plumbides, Eu2Pt3Pb5 and SrPt2Pb4, were discovered using high-temperature exploratory synthesis and flux-assisted crystal growth. Their crystal structures were determined from single-crystal X-ray diffraction. Both compounds crystallize in the orthorhombic system; Eu2Pt3Pb5 belongs to the Y2Rh3Sn5 structure type (Cmc21, a = 4.6146(2) Å, b = 27.3082(12) Å, c = 7.5147(3) Å, Z = 4, R1 = 0.0310, and wR2 = 0.0736) and SrPt2Pb4 to the NdRh2Sn4 type (Pnma, a = 19.411(5) Å, b = 4.5834(13) Å, c = 7.6548(19) Å, Z = 4, R1 = 0.0399, and wR2 = 0.0906). Both compounds feature complex frameworks of Pt-Pb and Pb-Pb bonds with very similar motifs, with Eu or Sr cations filling the cavities, which differ by the presence of the TiNiSi-type EuPtPb layer in Eu2Pt3Pb5. According to the DFT calculations, both compounds are metallic and feature Sr and Eu divalent cations along with a negatively charged mostly covalent framework of Pt and Pb atoms. Magnetic measurements show that the SrPt2Pb4 compound is non-magnetic, while Eu2Pt3Pb5 is a paramagnet above ca. 85 K and below that temperature transitions to the ferromagnetically ordered state with very low coercivity.