Ternary Polar Intermetallics within the Pt/Sn/R Systems (R = La–Sm): Stannides or Platinides?

[Image: see text] Starting generally with a 4:6:3 molar ratio of Pt, Sn, and R (where R = La–Sm), with or without the application of a NaCl flux, seven ternary compounds were obtained as single crystals. The platinides Pt(4)Sn(6)R(3) (R = La–Nd) crystallize with the Pt(4)Ge(6)Pr(3) type of structure (oP52, Pnma, a = 27.6–27.8 Å, b = 4.59–4.64 Å, c = 9.33–9.40 Å). With R = Pr, Pt(4)Sn(6)Pr(3–x) (oP52, Pnma, a = 7.2863(3) Å, b = 4.4909(2) Å, c = 35.114(1) Å) is also obtained, which might be considered a high-temperature polymorph with disorder on the Sn- and Pr-sites. For R = Nd and Sm, a structurally related isostructural series with a slightly different composition Pt(3)Sn(5)R(2–x) (oP52, Cmc2(1), a = 4.50–4.51 Å, b = 26.14–26.30 Å, c ≈ 7.29 Å) has been observed, together with Pt(7)Sn(9)Sm(5) (oS42, Amm2, a = 4.3289(5) Å, b = 28.798(4) Å, c = 7.2534(9) Å) under the same conditions. The latter exhibits the rare Zr(5)Pd(9)P(7)-type structure, linking polar intermetallics to metal phosphides, in accord with P(7)Pd(9)Zr(5)≡Pt(7)Sn(9)Sm(5). All structures may be described in terms of either negative Pt/Sn networks encapsulating positive R atoms, or {PtSn(x)} clusters (x = 5, 6, or rarely 7) sharing vertices and edges with R in the second coordination sphere and with considerable heterometallic Pt–R bonding contributions.