The crystal structure of Sc 2Ru 5B 4

Abstract

The crystal structure of Sc 2Ru 5B 4 has been determined by single-crystal X-ray analysis. Sc 2Ru 5B 4 crystallizes in the primitive monoclinic space group P2 m with a = 9.983(6), b = 8.486(4), c = 3.0001(3)Å, γ = 90.01(7)°, Z = 2. Deviations from the orthorhombic space group Pbam- D 9 2 h are small but significant. Intensity measurements were obtained from a four-circle diffractometer. The structure was solved by Patterson methods and refined by full matrix least-squares calculation. R = ∑|ΔF| ∑|F 0| = 0.036 for an asymmetric set of 863 independent reflections (| F 0|>2 σ( F 0)). The crystal structure is characterized by two different types of boron atoms: (a) isolated borons B(1) and B(3) in distorted trigonal Ru-prisms with tetrakaidekahedral metal coordination: 6Ru + 3Sc, and (b) boron atoms B(2) and B(4) with a pronounced tendency to form boron pairs (B(2)-B(2) = 1.86 Å, B(4)-B(4) = 1.89 Å); the metal coordination of these boron atoms is 6Ru + 2Sc. Sc atoms have a coordination number of 17 consisting of 10Ru + 2Sc + 5B. The crystal structure of Sc 2Ru 5B 4 is a pentagon layer structure (Ru, B atoms) with a 4.3.4.3 2-secondary layer of Sc atoms. The structure is furthermore related to the structure types of Ti 3Co 5B 2 and CeCo 3B 2. From powder photographs Sc 2Os 5B 4 is isotypic. No superconductivity was observed for Sc 2(Ru, Os) 5B 4 down to 1.5 K.