ИСТИНА

We have recently reported several new palladium- and platinum-rich compounds, such as Pd5InSe, Pd8In2Se, Pd17In4Se4, Pd5InAs, Pt5InAs, and Pt8In2As, all of which feature cuboctahedral [T12In] (T = Pd/Pt) fragments that are encountered in binary intermetallics of the Cu3Au structure type. The compounds with 5:1:1 atomic ratios belong to the Pd5TlAs structure type, a relatively uncommon type that was established in early 1970s [1] and until recently included only a few structurally characterized compounds, e.g. Pd5CdSe, Pd5CdAs [2], and Pd5HgSe [3]. The compounds with 8:2:1 atomic ratio belong to the Pd8In2Se-type, that we have discovered, which features double-stacked along the c axis [T12In] (T = Pd/Pt) fragments, and thus are essentially second homologues to the Pd5TlAs type of structures. Although several other palladium and platinum ternary pnictides, tetrelides and selenides, belonging to the Pd5TlAs structure type, were suggested in the same paper [1], no structural data was provided and the compositions were not established properly. And, surprisingly, neither structures nor any properties of most of the suggested compounds were never studied since then. Here we report the results of our purposeful synthesis of the compounds of the Pd5TlAs- and Pd8In2Se-type in Pd-In-P, Pt-In-P, Pd-Zn-Se, Pd-Zn-P, Pt-Zn-P systems, their crystal and electronic structures, bonding analysis, as well as magnetic properties and the response to hydrogenation. High-temperature ampoule technique was used for the synthesis. Crystal structures of compounds were determined using powder or single-crystal diffraction data. Electronic structures were established based on the DFT calculations. New compounds are built in a similar way to previously characterized ones belonging to the Pd5TlAs structure type. Their structures can be described either in terms of linear intergrowth structures of Cu3Au- and PtHg2-type blocks, or as layers of Pd- or Pt-based cuboctahedra separated by sheets of pnictogen or chalcogen. We have found no new second homologues neither for palladium, nor for platinum under equilibrium conditions.