Merging the AuCu 3 - and BaAl 4 -based structure motifs: flux-assisted synthesis, crystal, and electronic structure of Ca 2 Pt 7 XP 4- δ phosphide platinides (X = Al, Ti, and Zn).

Three quaternary phosphide platinides, Ca 2 Pt 7 AlP 3.00(4) , Ca 2 Pt 7 TiP 3.24(4) , and Ca 2 Pt 7 ZnP 2.78(2) , were synthesized by a high-temperature technique using lead as a flux. According to the single-crystal diffraction data, they are isotypic and crystallize in the tetragonal space group I 4/ mmm with Z = 2 (Ca 2 Pt 7 AlP 3.00(4) : a = 3.9893(6) Å, c = 26.832(5) Å; Ca 2 Pt 7 TiP 3.24(4) : a = 3.99610(10) Å, c = 26.9074(17) Å; Ca 2 Pt 7 ZnP 2.78(2) : a = 4.0020(2) Å, c = 26.5549(17) Å) and thus represent first europium-free compounds of the Eu 2 Pt 7 AlP 2.95 structure type. Their structures can be described as an intergrowth of the AuCu 3 - and CaBe 2 Ge 2 -type blocks. DFT calculations predict metallic conductivity and non-magnetic state for all three compounds. Bonding analysis based on the Bader charge distribution and ELF topology reveals a combination of localized covalent and ionic interactions in the CaBe 2 Ge 2 -type fragments and complex pattern of pairwise, multi-center, and ionic interactions in the AuCu 3 -type fragments that closely reproduces bonding in the parent Pt 3 X (X = Al, Ti, Zn) binary intermetallics.