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摘要
Two new non-isostructural lanthanide(III) nitride tellurides with the composition M4N2Te3 bearing terbium (Tb4N2Te3) and dysprosium (Dy4N2Te3) could be synthesized by the reaction of terbium (Tb) or dysprosium (Dy) metal with sodium azide (NaN3), tellurium (Te), iodine (I-2), and sodium iodide (NaI) as flux in evacuated silica tubes for seven days at 950 degrees C. Tb4N2Te3 crystallizes orthorhombically in space group Pnna with the lattice parameters a = 727.14(5), b = 1164.37(8), c = 1100.93(7) pm, V-m = 140.33(2) cm(3).mol(-1) (Z = 4). In contrast, Dy4N2Te3 appears in the monoclinic space group P2(1)/n with the lattice parameters a = 719.56(5), b = 1164.05(8), c = 1097.34(7) pm, beta = 91.327(3)degrees, V-m = 138.34(2) cm(3).mol(-1) (Z = 4). Corresponding to the lanthanide contraction the cell parameters of Dy4N2Te3 show slightly smaller values compared to Tb4N2Te3, but the change of symmetry leads to a different crystal system. Symmetry operations related to a and c are lost according to P2/n2(1)/n2/a -%26gt; P12(1)/n(1) and the two crystallographically independent M3+ cations in Tb4N2Te3 split into four in Dy4N2Te3. Both Tb3+ cations are coordinated by six anions in first sphere plus one Te2- anion further apart for (Tb1)(3+) leading to capped trigonal prisms and distorted octahedra. The four Dy3+ cations with coordination numbers of six plus one and three times six also reside in capped and uncapped distorted octahedral anionic coordination. Both crystal structures have infinite zigzag chains in (1)(infinity){[NM4/2e](3+)} in common, which are formed by transedge connected [NM4](9+) tetrahedra. They run along [010] and exhibit two crystallographically different N3- anions in both cases. The latter are coordinated on the one hand to two sorts of Tb3+ cations in Tb4N2Te3 and on the other hand to four sorts of Dy3+ cations in Dy4N2Te3 as major structural difference. However, both crystal structures show a clear group-subgroup relationship.
- 出版日期2014-6
