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 P4/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.

The new ternary rhodium borides Mg 3 Rh 5 B 2 and Sc 3 Rh 5 B 2 (P4/mbm, Z = 2; a = 943.4(1) pm, c = 292.2(1) pm and a = 943.2(1) pm, c = 308.7(1) pm, respectively) crystallize with the Ti 3 Co 5 B 2 type structure. Mg and Sc may in part be substituted by a variety of elements M. For M = Si and Fe, homogeneity ranges were found according to A 3±x M x Rh 5 B 2 with 0 £ x £ 1.0 for A = Sc and with x up to 1.5 for A = Mg. Quaternary compounds with x = 1 (A 2 MRh 5 B 2 : A/M in short) were prepared with M = Be, Al, Si, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Sn (Co, Ni only with A = Mg; Sn only with A = Sc; P, As with deficiencies). Single crystal X-ray investigations show an ordered substitutional variant of the Ti 3 Co 5 B 2 type in which the M atoms are arranged in chains along [001] with intrachain and interchain M±M distances of about 300 pm and 660 pm, respectively. Measuring the magnetisation (1.7 K±800 K) of the phases Mg/Mn, Sc/Mn, Mg/Fe, and Sc/Fe reveals antiferromagnetic interactions in the first and dominating ferromagnetic intrachain interactions in the remaining ones. Interchain interactions of antiferromagnetic nature are evident in Sc/Mn and Mg/Fe leading to metamagnetism below T N = 130 K, while Sc/Fe behaves ferromagnetically below T C = 450 K. The overall trend towards stronger ferromagnetic interactions with increasing valence electron concentration is obvious.

The title compounds were prepared by reaction of the elemental components in metal ampoules under argon atmosphere (

structure structure (solids and liquids) D 2000 -004Ternary Rhodium Borides A 3 Rh 5 B 2 (A: Mg, Sc) and Quaternary Derivatives A 2 MRh 5 B 2 . Preparation, Crystal Structure (M: Main Group and 3d Elements), and Magnetism (M: Mn, Fe).-Most of the title compounds are prepared by arc melting of the elements followed by annealing under argon atmosphere. The new ternary compounds Mg 3 Rh 5 B 2 and Sc 3 Rh 5 B 2 crystallize in the Ti 3 Co 5 B 2 type structure (space group P4/mbm, Z = 2). Mg and Sc can in part be substituted by a variety of elements to form quaternary A 2 MRh 5 B 2 compounds (M: Be, Al, Si, P, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Sn). Single crystal XRD studies show an ordered substitution variant of the Ti 3 Co 5 B 2 type in which the M atoms are arranged in chains along [001]. Magnetization measurements are reported for the Mn and Fe substituted compounds. -(NAGELSCHMITZ, E. A.; JUNG, W.; FEITEN, R.; MUELLER, P.; LUEKEN, H.

Scandium Iridium Boride Sc 3 Ir 5 B 2 and the Quaternary Derivatives Sc 2 MIr 5 B 2 with M: Be, Al, Si, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Ga, or Ge: Preparation, Crystal Structure, and Physical Properties. -The new title compounds are prepared by arc-melting appropriate compressed mixtures of the elemental components in an argon atmosphere. They crystallize in the tetragonal space group P4/mbm with Z = 2. Structure determinations based on single crystal X-ray data are 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 and the quaternary compounds Sc 2 MIr 5 B 2 crystallize with the Ti 3 Co 5 B 2 -type structure. The compounds (M: Mn, Fe, Co) have highly anisotropic magnetic properties. -(NAGELSCHMITZ, E. A.; JUNG, W.; Chem. Mater. 10 (1998) 10, 3189-3195; Inst. Anorg. Chem., Univ. Koeln,