Ein neues Selten-Erd-Metall(III)-Oxidchlorid-Oxotellurat(IV): Nd₅O₄Cl₃[TeO₃]₂ / A New Rare Earth-Metal(III) Oxide Chloride Oxotellurate(IV): Nd₅O₄Cl₃[TeO₃]₂

Pale violet, plate-like single crystals of the title compound, neodymium(III) oxide chloride oxotellurate( IV) Nd₅O₄Cl₃[TeO₃]₂, can be obtained by the reaction of Nd₂O₃ with NdCl₃ and TeO₂ in equimolar ratios in evacuated silica ampoules within five days at 775 °C with an excess of CsCl added as fluxing agent. Nd₅O₄Cl₃[TeO₃]₂ crystallizes in the monoclinic space group C2/m (no. 12) with the lattice parameters a = 1270.61(9), b = 562.70(4), c = 1008.97(8) pm, β = 90.784(3)°and Z = 2, and is thus isostructural to the lanthanoid(III) oxide halide oxoselenates(IV) Tb₅O₄Cl₃[SeO₃]₂ and Gd₅O₄Br₃[SeO₃]₂. The crystal structure exhibits three crystallographically different Nd³⁺ cations, of which (Nd1)³⁺ has a purely oxidic coordination sphere of eight oxide anions building up a square prism. (Nd2)³⁺ and (Nd3)³⁺ are both coordinated by oxide and chloride anions. The coordination polyhedron around (Nd2)³⁺ is a trigonal prism of oxide anions that is capped by one chloride anion to give a coordination number of seven. (Nd3)³⁺ resides in an eightfold coordination of five oxide and three chloride anions forming a square antiprism. All (O1)²− anions are surrounded tetrahedrally by Nd³⁺ cations as [ONd₄]¹⁰⁺ units. These tetrahedra share common edges and vertices to generate two-dimensional infinite layers of the composition _∞²{[O₄Nd₅]⁷⁺}, which extend parallel to the (001) plane. The chloride anions (Cl1)⁻are connecting those slabs via Nd3-Cl1-Nd3 bridges along the [001] direction, while the (Cl2)− anions alternate with the Te⁴⁺ cations above and below the layers. The three-dimensional crystal structure of Nd₅O₄Cl₃[TeO₃]₂ is completed by Te⁴⁺ cations, which are bonded to one (O2)²− and two (O3)²− anions to form ψ¹-tetrahedra [TeO₃]²− with a nonbinding, stereochemically active electron pair (“lone pair”) pointing into the free space between the chloride-decorated _∞²{[O₄Nd₅]⁷⁺} layers

Graphical Abstract

Ein neues Selten-Erd-Metall(III)-Oxidchlorid-Oxotellurat(IV): Nd₅O₄Cl₃[TeO₃]₂ / A New Rare Earth-Metal(III) Oxide Chloride Oxotellurate(IV): Nd₅O₄Cl₃[TeO₃]₂