Renaissance of the Stella Quadrangula: The Lanthanoid Nitride Tellurides Ln13N5Te12 (Ln = La–Nd)

• Published in: European journal of inorganic chemistry 2018-07, Vol.2018 (26), p.3014-3021
• Main Authors: Lissner, Falk, Foltin, Markus L., Schleid, Thomas
• Format: Article
• Language: English
• Subjects: Crystal structure; Fused silica; Gadolinium; Inorganic chemistry; Intermetallic compounds; Iodine; Lanthanoids; Lanthanum; Lattice parameters; Nitrides; Oligomers; Silicon dioxide; Single crystals; Sodium azides; Stella quadrangula; Structure elucidation; Tellurides; Tellurium; Trimers; Tubes
• ISSN: 1434-1948; 1099-0682
• DOI: 10.1002/ejic.201800018

Ln13N5Te12 (Ln = La–Nd), a quite unusual composition of the lanthanoid(III) nitride tellurides, appears with a new crystal structure and can be obtained by reactions of lanthanoid metal (Ln) with elemental tellurium (Te), sodium azide (NaN3), elemental iodine (I2) and sodium iodide (NaI) as flux in evacuated fused silica tubes for seven days at 900 °C. The black, shard‐shaped single crystals of the short new series Ln13N5Te12 (Ln = La–Nd) crystallize monoclinically in the space group P21/m with lattice parameters ranging from a = 1039.86(7), b = 1373.29(9), c = 1311.78(9) pm, β = 100.103(3)° for La13N5Te12 to a = 1016.73(7), b = 1337.58(9), c = 1288.92(9) pm, β = 100.094(3)° for Nd13N5Te12 and Z = 2. Unlike the other ternary compounds of the lanthanoid(III) nitride tellurides, two different types of isolated oligomers containing edge‐sharing [NLn4]9+ tetrahedra occur in their crystal structure. The fusion of two [NLn4]9+ units via one common edge forms [N2Ln6]12+ bitetrahedra, which are already known from the Ln3NTe3 examples with Ln = Gd–Ho. In contrast, the [N3Ln7]12+ trimers built up by three [NLn4]9+ tetrahedra with two sharing edges for each [NLn4]9+ unit, but three common edges overall, represent a new highlight. Both kinds of oligomers can be traced back to a stella quadrangula [N4Ln8]12+ and are embedded in a dense matrix of Te2– anions according to {[Ln6N2][Ln7N3]Te12}. The new ternary nitride tellurides Ln13N5Te12 (Ln = La–Nd) were synthesized and characterized by X‐ray diffraction. The monoclinic compounds crystallize in the space group P21/m with two types of oligomers, [N2Ln6]12+ and [N3Ln7]12+, both traced back to a stella quadrangula. In addition, a band gap of 1.4 eV was determined for black, semi‐conducting La13N5Te12 by diffuse reflectance spectroscopy (DRS).