MgOs3B4 and ScOs3B4, ternary borides with a new channel structure

摘要

The new ternary osmium borides MgOs3B4 and ScOs3B4 were prepared by reaction of the elements. They crystallize orthorhombically with Z = 4 in the space group Cmcm. The crystal structures were determined from single crystal X-ray diffraction intensity data. MgOs3B4 (a = 291.28(2) pm, b = 1185.9(1) pm, c = 975.8(1) pm, 621 reflections, R-1 = 0.054) and ScOs3B4 (a = 295.03(4) pm, b = 1179.7(2) pm, c = 981.9(1) pm, 516 reflections, R-1 = 0.054) are isotypic, The structure contains isolated boron atoms coordinated by six osmium atoms at the corners of a trigonal prism and in addition boron atoms forming a new one-dimensional building element composed of corner sharing, slightly distorted squares with B-B distances of 200(1) pm in the Mg compound and 203(2) pm in the Sc compound. The Mg and Sc atoms, respectively, fill channels in the Os/B-framework running along the a axis. (C) 2000 Academic Press. [References: 17]