ALKALINE-EARTH TRANSITION-METAL ANTIMONIDES AT4SB12 (A=CA, SR, BA - T=FE, RU, OS) WITH LAFE4P12-STRUCTURE

The title compounds were prepared by reaction of CaSb2, SrSb2, or BaSb 3 with the transition metals and antimony in sealed silica tubes. They crystallize with the cubic LaFe4P12-structure, which was refined from single-crystal X-ray data of CaFe4Sb12, SrRu4Sb12, and BaRu4Sb12 to r esiduals of R = 0.014, 0.016, and 0.014, respectively. The thermal par ameters of the alkaline earth ions increase with decreasing ionic size . The Sb-Sb distances are greater in the iron compound than they are i n the two ruthenium compounds. This is rationalized to be due to a lar ger portion of electrons in antibonding Sb-Sb states in the iron compo und.