The orthorhombic crystal structure of Ru2Si3, Ru2Ge3, Os2Si3 and Os2Ge3

Single-Crystal studies have indicated that the true symmetry of Ru₂Ge₃ is not tetragonal but orthorhombic. Space group Pbcn (No. 60); a = 11-436, b = 9-238 and e = 5-716 Å; Z = 8, Dx = 9-23 g cm⁻³, F.W. 419-91, F(000)= 1472, μ(Mo Kα)=40-4 cm⁻¹. The structure was solved by the Patterson method and refined to an R of 0-085. The compounds Ru₂Si₃, Os₂Si₃ and Os₂Ge₃ are isotypic. The Ru₂Ge₃ structure is related to the tetragonal Ru₂Sn₃ structure. Two unit cells of the latter placed side by side give the orthorhombic unit cell of Ru₂Ge₃ (a/c=2). Whereas the positions of the transition element in both structures are nearly identical and of the β-tin type, there are differences between Sn and Ge sites and consequently different coordination polyhedra.