Synthese und Kristallstrukturen des Zink‐Rhodiumborids Zn 5 Rh 8 B 4 und der Lithium‐ Magnesium‐Rhodiumboride Li x Mg 5−x Rh 8 B 4 (x = 1.1 und 0.5) und Li 8 Mg 4 Rh 19 B 12

Synthesis and Crystal Structures of Zinc Rhodium Boride Zn 5 Rh 8 B 4 and the Lithium Magnesium Rhodium Borides Li x Mg 5−x Rh 8 B 4 (x = 1.1 and 0.5) and Li 8 Mg 4 Rh 19 B 12 The title compounds were prepared by reaction of the elemental components in metal ampoules under argon atmosphere (1100 °C, 7 d). In the case of Zn 5 Rh 8 B 4 (orthorhombic, space group Cmmm , a = 8.467(2) Å, b = 16.787(3) Å, c = 2.846(1) Å, Z = 2) a BN crucible enclosed in a sealed tantalum container was used. The syntheses of Li x Mg 5−x Rh 8 B 4 (orthorhombic, space group Cmmm , Z = 2, isotypic with Zn 5 Rh 8 B 4 , lattice constants for x = 1.1: a = 8.511(3) Å, b = 16.588(6) Å, c = 2.885(1) Å, and for x = 0.5: a = 8.613(1) Å, b = 16.949(3) Å, c = 2.9139(2) Å) and Li 8 Mg 4 Rh 19 B 12 (orthorhombic, space group Pbam , a = 26.210(5) Å, b = 13.612(4) Å, c = 2.8530(5) Å, Z = 2) were carried out in tantalum crucibles enclosed in steel containers using lithium as a metal flux. The crystal structures were solved from single crystal X‐ray diffraction data. In both structures Rh atoms reside at z = 0 and all non‐transition metal atoms at z = 1/2. Columns of Rh 6 B trigonal prisms running along the c‐axis are laterally connected to form three‐dimensional networks with channels of various cross sections containing Li‐, Mg‐, and Zn‐atoms, respectively. A very short Li‐Li distance of 2.29(7) Å is observed in Li 8 Mg 4 Rh 19 B 12 .