The first quaternary lanthanide(III) nitride iodides: NaM4N2I7 (M=La–Nd)

In attempts to synthesize lanthanide(III) nitride iodides with the formula M 2NI3 (M =La–Nd), moisture-sensitive single crystals of the first quaternary sodium lanthanide(III) nitride iodides NaM 4N2I7 (orthorhombic, Pna 21; Z =4; a =1391–1401, b =1086–1094, c =1186–1211 pm) could be obtained. The dominating structural features are View the MathML source{[NM4/2e]3+}∞1 chains of trans-edge linked [NM4]9+ tetrahedra, which run parallel to the polar 21-axis [001]. Between the chains, direct bonding via special iodide anions generates cages, in which isolated [NaI6]5– octahedra are embedded. The IR spectrum of NaLa4N2I7 recorded from 100 to 1000 cm–1 shows main bands at υ=337, 373 and 489 cm–1. With decreasing radii of the lanthanide trications these bands, which can be assigned as an influence of the vibrations of the condensed [NM4]9+ tetrahedra, are shifted toward higher frequencies for the NaM4N2I7 series (M=La–Nd), following the lanthanide contraction.