Das erste Alkalimetall-Lanthanoid(III)-Iodid-Oxotellurat(IV): Na2Lu3I3[TeO3]4
Résumé
Colourless platelets of Na2Lu3I3[TeO3]4 were obtained within five days at 775 °C by the reaction of Lu2O3 and TeO2 in a 3 : 8 molar ratio with NaI added in excess as both fluxing agent and reactant in evacuated silica ampoules. It crystallizes in the monoclinic space group P2/c with the lattice parameters a = 921.69(5), b = 552.71(3), c = 1664.37(9) pm, β = 90.218(4)° and Z = 2. The crystal structure of Na2Lu3I3[TeO3]4 exhibits two crystallographically different Lu3+ cations, both coordinated by eight O2- anions as square antiprisms. These polyhedra are interconnected via four common edges to build up 5-} layers (e = edge-linking) parallel to (100). Furthermore, the crystal structure includes a crystallographically unique Na+ cation surrounded by four O2- and four I- anions also in the shape of a square antiprism. These polyhedra connect via common (I2)-***(I2)- edges in generating 18-} double-strands that are further linked by (I1)- vertices to result in the formation of 17-} layers (v = vertex-linking) spreading out parallel to (100) as well. Thus, the crystal structure contains two crystallographically distinct I- anions, of which (I1)- is coordinated nearly linear (∢(Na-I1-Na) = 179.6°) by two Na+ cations, whereas (I2)- has contact to three of them displaying a distance of 114 pm from the triangular (Na+)3 plane. The crystal structure of Na2Lu3I3[TeO3]4 is completed by two crystallographically independent Te4+ cations that show stereochemically active non-bonding electron pairs ("lone pairs") and are located above and below the 5-} layers forming isolated ψ1-tetrahedral [TeO3]2- anions (d(Te-O) = 188 - 190 pm) with all oxygen atoms.
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