CsR(R₆CoI₁₂)₂(R = Gd, Er) and (CeI)_0.26(Ce₆MnI₉)₂:  Two New Structure Types Featuring R₆Z Clusters

Abstract

Compounds adopting two new structure types containing discrete lanthanide clusters have been found, CsR(R6CoI12)2 (R = Gd or Er) and (CeI)0.26(Ce6MnI9)2. CsEr(Er6CoI12)2 and CsGd(Gd6CoI12)2 were synthesized in reactions of CsI, RI3, CoI2, and R metals (3:19:6:23) heated to 750 degrees C for 500 h followed by slow cooling (0.1 degrees C/min). The X-ray crystal structure of CsEr(Er6CoI12)2 was solved in the Pa3 space group with a = 18.063(2) A at 250 K (Z = 4, R1 [I > 2sigma(I)] = 0.0459). (CeI)0.26(Ce6MnI9) was synthesized by combining KI, CeI3, MnI2, and Ce metal and heating to 850 degrees C for 500 h. The single-crystal X-ray structure for (CeI)0.26(Ce6MnI9)2 was solved in the trigonal, P3 (147) space group with lattice parameters of a = 11.695(1) A and c = 10.8591(2) A (Z = 2, R1 [I > 2sigma(I)] = 0.0895). Elemental analyses (X-ray photoelectron spectroscopy (XPS) and atomic absorption spectroscopy (AAS)) were performed and show the absence of potassium in the structure. A disorder model was refined for the atoms in the large cavity. The magnetic susceptibility data for CsGd(Gd6CoI12)2 is consistent with strong intracluster ferromagnetic coupling, but intercluster antiferromagnetic coupling suppresses the susceptibility below 70 K.