A New Structure Type for Rare‐Earth‐Metal Cluster Compounds stabilized by transition metals: KPr6I10Os, CsPr6I10Fe, CsLa6I10Fe, and CsLa6I10Mn

Reactions of KI, Pr, PrI3, and Os in niobium tubes at 800° yielded black, air‐ and moisture‐sensitive crystals of Kpr6I10Os which were characterized by single crystal X‐ray diffraction (orthorhombic, Pnma, a = 15.362(3), b = 13.498(2), c = 14.128(3) Å, Z = 4, R(F)/Rw = 4.4/5.6%). Subsequent parallel experiments also gave, according to Guinier powder pattern data, the isostructural compounds CsPr6I10Fe (a = 15.312(2), b = 13.426(1), c = 14.154(1) Å), CsLa6I10Fe (a = 15.523(2), b = 13.646(2), c = 14.334(1) Å) and CsLa6I10Mn (a = 15.457(4), b = 13.737(2), c = 14.329(2) Å). The important structural feature is the presence of octahedral rare‐earth‐metal cluster units R6 that are centered by a transition‐metal atom Z and bridged and interconnected by halide atoms. The new compounds exhibit the same general pattern of halide connectivity (R6Z)X X X X as do the triclinic compounds R6X10Z. However, the structural arrangement of the metal octahedra is significantly different; they are linked by Ii–i atoms into zigzag chains along [010] and these are interconnected into a three dimensional network by Ii–a atoms to form channels in which the alkali‐metal atoms are located. The introduction of alkali‐metal atoms into reactions leads to new quaternary compounds with discrete rare‐earth‐metal clusters centered by transition metals and more open structure frameworks. Measurements of the temperature dependencies of the magnetic susceptibilities for CsLa6I10Fe and CsLa6I10Mn are consistent with expectations for 17‐ and 16‐electron cluster systems, respectively.