Scandium Iridium Boride Sc3Ir5B2 and the Quaternary Derivatives Sc2MIr5B2 with M = Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge: Preparation, Crystal Structure, and Physical Properties

The new compounds Sc 3 Ir 5 B 2 and Sc 2 MIr 5 B 2 with M = Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge were prepared by arc-melting appropriate compressed mixtures of the elemental components in an argon atmosphere. They crystallize tetragonally with Z = 2 in the space group P 4 /mbm with lattice constants a = 952.6(1) pm and c = 304.8(1) pm for Sc 3 Ir 5 B 2 and ranging from a = 927.0(1) pm and c = 296.8(1) pm (Sc 2 BeIr 5 B 2 ) to a = 932.9(1) pm and c = 310.3(1) pm (Sc 2 TiIr 5 B 2 ) for the quaternary compounds. According to powder diagrams, all compounds are isotypic. Structure determinations based on single-crystal X-ray data were performed for Sc 2 SiIr 5 B 2, Sc 2 VIr 5 B 2, and Sc 2 FeIr 5 B 2 . Sc 3 Ir 5 B 2 crystallizes with the Ti 3 Co 5 B 2 -type compounds, while the quaternary compounds form an ordered substitutional variant of this structure. The M atoms are arranged in rows along [001] with M−M distances of ∼300 pm in the rows and ∼660 pm between the rows. For the compounds with M = Mn, Fe, or Co, this results in highly anisotropic magnetic properties. Susceptibility measurements with a Faraday balance in the range 7−770 K suggest ferromagnetic coupling in the rows at low temperatures. Between the rows, the coupling was antiferromagnetic for Sc 2 FeIr 5 B 2 ( T N ≈ 190 K) and ferromagnetic for Sc 2 MnIr 5 B 2 ( T C ≈ 115 K, μ s ≈ 1.2μ B ) and for Sc 2 CoIr 5 B 2 ( T C ≈ 135 K, μ s ≈ 1.2μ B ). The temperature dependence of the resistivity was measured for the compounds with M = Si, Mn, Fe, and Co.