Pr₁₀(C₂)₂Br₁₆: Eine neue Struktur mit diskreten Pr₁₀‐Doppeloktaedern

Abstract

Abstract Pr 10 (C 2 ) 2 Br 16 : A New Structure with Discrete Octahedra Doubles The compound Pr 10 (C 2 ) 2 Br 16 is prepared from Pr, PrBr 3 , and C with a molar ratio of 7:8:6 at 780 to 820 °C as the major phase, forming polygonal black crystals with a metallic lustre which are moisture and air sensitive. It crystallizes in the triclinic system, $P{\bar 1}$ , with lattice parameters a = 9.096(2) Å, b = 12.185(2) Å, c = 16.688(3) Å, α = 79.57(3)°, β = 89.86(3)°, γ = 84.38(3)°. In the crystal structure the Pr atoms form Pr 6 octahedra centered by C 2 groups, and two such octahedra are condensed via edges to form Pr 10 units. The bromine atoms coordinate the doubleoctahedra above all free edges and connect them via $Br^{i-i}_{\rm 4/2} Br^{i-a}_{\rm 8/2} Br^{a-i}_{\rm 8/2}$ bridges. The mean C‐C distance in the C 2 unit is 1.42(2) Å. HRTEM micrographs display the characteristic fragment of the Pr 10 double octahedron. Furthermore antiphase domains are identified as specific defects in the structure.