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 BaSb₃ 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 residuals of R = 0.014, 0.016, and 0.014, respectively. The thermal parameters of the alkaline earth ions increase with decreasing ionic size. The Sb? Sb distances are greater in the iron compound than they are in the two ruthenium compounds. This is rationalized to be due to a larger portion of electrons in antibonding Sb? Sb states in the iron compound.