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Two Structurally Related Oxide Nitride Chalcogenides of the Lanthanoids: Tb 3 ONSe 2 and La 5 O 2 NS 4
Author(s) -
Lissner Falk,
Strobel Sabine,
Schleid Thomas
Publication year - 2010
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.200900446
Subject(s) - lanthanide , monoclinic crystal system , chemistry , crystal structure , crystallography , nitride , oxide , inorganic chemistry , ion , organic chemistry , layer (electronics)
The structurally related oxide nitride chalcogenides Tb 3 ONSe 2 and La 5 O 2 NS 4 can be prepared by the oxidation of the respective lanthanoid metal ( M = Tb and La) with selenium or sulfur and sodium azide (NaN 3 ) in the presence of oxygen‐containing impurities, when iodine (I 2 ) or the corresponding lanthanoid trichloride ( M Cl 3 ) is used as sodium trap for the formation of NaI or NaCl, respectively. The thermal treatment of these mixtures along with additional NaI or NaCl as flux at 900 °C in evacuated silica tubes yielded transparent, yellow polyhedra in the case of Tb 3 ONSe 2 or orange, lath‐shaped crystals of La 5 O 2 NS 4 . Both monoclinic structures ( C 2/ m , Z = 4) were determined from X‐ray single‐crystal diffraction data (Tb 3 ONSe 2 : a = 1548.85(9), b = 392.02(2), c = 968.61(6) pm, β = 97.194(3)°; La 5 O 2 NS 4 : a = 1571.13(8), b = 409.67(2), c = 1681.03(9) pm, β = 101.204(3)°). The crystal structure of Tb 3 ONSe 2 comprises three crystallographically different Tb 3+ cations residing in six‐ and sevenfold coordination of the respective anions, whereas the crystal structure of La 5 O 2 NS 4 shows five different La 3+ cations with coordination numbers from six to eight. For the first time in the chemistry of oxide nitride chalcogenides of the lanthanides, an ordering of the light anions (O 2– and N 3– ) is observed, and proper structure descriptions based on vertex‐ and edge‐connected [O M 4 ] 10+ and [N M 4 ] 9+ tetrahedra ( M = Tb and La) becomes possible. As main structural feature, a bulky chain {}^1_\infty {[ONTb 3 ] 4+ } running along [010] can be detected in the crystal structure of Tb 3 ONSe 2 . The same morphology, but a different chemistry is realized in the related crystal structure of La 5 O 2 NS 4 , where these topologically equivalent strands {}^1_\infty {[O 2 La 3 ] 5+ } and an additional second chain {}^1_\infty {[NLa 2 ] 3+ }, built up by vertex‐ and edge connected [NLa 4 ] 9+ tetrahedra, compose the compound. As supporting tool for the distinction of the O 2– and N 3– anions in both crystal structures, the valence‐bond concept is also applied.