Na2[Pr4O2]Cl9 und K2[Pr4O2]Cl9, die ersten reduzierten quaternären Praseodymchloride mit anti-SiS2-analogen [Pr4/2O]-Ketten

Na₂[Pr₄O₂]Cl₉ and K₂[Pr₄O₂]Cl₉, the First Reduced Quaternary Praseodymium Chlorides with Anti-SiS₂ Analogous [Pr_4/2O] Chains The compounds A₂[Pr₄O₂]Cl₉ (A = Na, K) are the first reduced quaternary praseodymium chlorides with anti-SiS₂ analogous [Pr_4/2O] chains. Synthesis took place in the temperature range from 900 to 600°C in silica-jacketed niobium containers from Pr metal, PrCl₃, PrOCl and NaCl (KCl) as starting materials. The X-ray structure analysis of a single crystal of Na₂[Pr₄O₂]Cl₉ (monoclinic, P2₁/m (No. 11), Z = 2, a = 812.2(2) pm, b = 1 134.1(2) pm, c = 937.6(2) pm, β = 106.51(2)°, R = 0.048, R_w = 0.037) exhibits trans-edge connected chains of [Pr_4/2O] tetrahedra running along [001] which are connected by surrounding common chloride ions forming layers parallel to (001). These layers are connected by further chloride ions to a three-dimensional network. The sodium ions surrounded by a heavily distorted octahedron of chloride ions are placed between the layers. The X-ray structure analysis of a single crystal of the otherwise isotypic K₂[Pr₄O₂]Cl₉ (monoclinic, P2₁/m (No. 11), Z = 2, a = 820.6(2) pm, b = 1 133.2(4) pm, c = 949.2(3) pm, β = 103.94(2)°, R = 0.073, R_w = 0.054) shows that potassium is coordinated by nine chloride ions.