title: Formation of complex three- and one-dimensional interpenetrating networks within carbodiimide chemistry: NCN2(-)-coordinated rare-earth-metal tetrahedra and condensed alkali-metal iodide octahedra in two novel lithium europium carbodiimide iodides, LiEu2(NCN)I3 and LiEu4(NCN)3I3.
abstract: Orange-red transparent single crystals of LiEu2(NCN)I3 and LiEu4(NCN)3I3 were synthesized from fluxes of europium iodide, sodium cyanide, sodium azide, and lithium iodide at elevated temperatures and structurally characterized by X-ray diffraction. While LiEu2(NCN)I3 crystallizes in the cubic system (Fdm, a = 15.1427(17) angstroms, V = 3472.2(7) angstroms3, Z = 16, R1 = 0.0322), LiEu4(NCN)3I3 adopts the hexagonal system (P6(3)/mmc, a = 10.6575(11) angstroms, c = 6.8232(10) angstroms, V = 671.16(14) angstroms3, Z = 2, R1 = 0.0246). Both extended structures are composed of complex frameworks built from europium tetrahedra coordinated by carbodiimide (symmetrical NCN2-) units on the one side and condensed iodine octahedra around lithium cations on the other. Within LiEu2(NCN)I3, vertex-sharing of the LiI6 subunits together with isolated europium tetrahedra results in two three-dimensional networks interpenetrating each other. Within LiEu4(NCN)3I3, face-sharing of the europium tetrahedra results in bitetrahedral units which further connect via two opposing vertexes into one-dimensional linkages. Likewise, the LiI6 octahedra share common faces to also yield one-dimensional linkages that fill the channels between the europium/carbodiimide substructure. The magnetic behavior of both compounds has been determined; the two phases follow Curie-Weiss laws with weak predominantly ferromagnetic exchange between the europium ions and atomic moments characterizing them as essentially divalent.
authors.affiliation: Institut für Anorganische Chemie der RWTH Aachen, Professor-Pirlet-Strasse 1, D-52056 Aachen, Germany.
authors.forename: Wuping
authors.initials: W
authors.lastname: Liao
authors.forename: Chunhua
authors.initials: C
authors.lastname: Hu
authors.forename: Reinhard K
authors.initials: RK
authors.lastname: Kremer
authors.forename: Richard
authors.initials: R
authors.lastname: Dronskowski