Pr5F[SiO4]2[SeO3]3: Another Complex Fluoride Oxosilicate Oxoselenate(IV)

摘要: During attempts to synthesize lanthanoid(III) fluoride oxoselenates(IV) with the simple composition MF[SeO3], not only Pr3F[SeO3]4, but also Pr5F[SiO4]2[SeO3]3 appeared as pale green crystalline by-products in case of praseodymium. crystallizes triclinically space group P (no. 2) a = 701.14(5), b 982.68(7), c 1286.79(9) pm, α 70.552(3), β 76.904(3), γ 69.417(3)° and Z 2. The five crystallographically different Pr3+ cations on general positions 2i show coordination numbers eight nine. [(Pr1)O8]13– [(Pr2)O8]13– polyhedra are connected to{[(Pr1, 2)2O12]18–} chains along [100] direction. [(Pr3)O7F]12–, [(Pr4)O8F]14– generate [F(Pr3, 4, 5)3O19]30– units about their central F– anion triangular coordination. These form {[F(Pr3, 5)3O16]24–} strands, again running parallel [100]. Their alternating connection {[(Pr1, results {[Pr5O20F]26–} sheets (001) plane. Like already known related compound Er3F[SiO4][SeO3]2, three-dimensional network {[Pr5O17F]20–} is achieved without contribution both tetravalent silicon selenium components. However, two Si4+ three Se4+ forming tetrahedral [SiO4]4– ψ1-tetrahedral [SeO3]2– all O2– anions guarantee charge balance. formation was observed when praseodymium sesquioxide (Pr2O3: in-situ produced from Pr Pr6O11 molar ratio 3/11:4/11),praseodymium trifluoride (PrF3) dioxide (SeO2) 1:1:3 ratios were reacted CsBr fluxing agent for days at 750 °C evacuated fused silica (SiO2) ampoules.