Pr₆C₂‐Doppeltetraeder in Pr₆C₂Cl₁₀ und Pr₆C₂Cl₅Br₅

Abstract

Abstract Pr 6 C 2 ‐Bitetrahedra in Pr 6 C 2 Cl 10 and Pr 6 C 2 Cl 5 Br 5 The compounds Pr 6 C 2 Cl 10 and Pr 6 C 2 Cl 5 Br 5 are prepared by heating stoichiometric mixtures of Pr, PrCl 3 , PrBr 3 and C in sealed Ta capsules at 810 − 820 °C. They form bulky transparent yellow to green and moisture sensitive crystals which have different structures: space groups C 2/ c , ( a = 13.687(3) Å, b = 8.638(2) Å, c = 15.690(3) Å, β = 97.67(3)° for Pr 6 C 2 Cl 10 and a = 13.689(1) Å, b = 10.383(1) Å, c = 14.089(1) Å, β = 106.49(1)° for Pr 6 C 2 Cl 5 Br 5 ). Both crystal structures contain C ‐centered Pr 6 C 2 bitetrahedra, linked via halogen atoms above edges and corners in different ways. The site selective occupation of the halogen positions in Pr 6 C 2 Cl 5 Br 5 is refined in a split model and analysed with the bond length‐bond strength formalism. The compound is further characterized via TEM investigations and magnetic measurements ( μ eff = 3.66 μ B ).