Chains of trans-edge connected [ZM4] tetrahedra (Z = N and O) in the lanthanide nitride chlorides M2NCl3 and Na2M4ONCl9 (M = La–Nd)

Single crystals of La2NCl3 and Na2Nd4ONCl9 were prepared from LaCl3, La and NaN3 or NdCl3, NdOCl, Nd and NaN3 (both at 850 °C for 7 d) in silica ampoules by a flux method with NaCl as flux and for the second compound also as sodium source. La2NCl3 crystallizes in the orthorhombic system with space group Ibam (no. 72) and four formula units in a unit cell of the dimensions a = 1375.32(9), b = 691.89(5) and c = 618.23(4) pm, while Na2Nd4ONCl9 crystallizes in space group P21/m (no. 11) of the monoclinic system with two formula units in a unit cell of the dimensions a = 803.54(6), b = 1134.26(8), c = 928.31(7) pm and β = 107.109(5)°. In both structures the dominating features are trans-edge connected [ZM4] tetrahedra in {[ZM4/2e]x+}∞1 chains (M2NCl3: M = La, Z = N, x = 3.0; Na2M4ONCl9: M = Nd, Z = (1/2)O + (1/2)N, x = 3.5; superscript e: edge connected). These straight chains run parallel to [0 0 1] in La2NCl3 and are connected via trans-edge sharing [(Cl1)La4]11+ tetrahedra in the same way as the [NLa4]9+ tetrahedra themselves. The second sort of chloride (Cl2) interconnects the layers of the two different types of chains. As a consequence of the lanthanide contraction the nitride chlorides with the composition M2NCl3 (M = La–Nd, Gd) crystallize in two different orthorhombic space groups. La2NCl3 is structurally isotypic with Ce2NCl3 and Pr2NCl3 (space group: Ibam), while Nd2NCl3 and Gd2NCl3 crystallize similarly, but in space group Pbcn. In Na2Nd4ONCl9 the connection between the zigzag chains of trans-edge shared [ZNd4]9.5+ tetrahedra (Z = O and N in a 1:1 molar ratio) appears to be more difficult. They are directly coupled via chloride anions and via Cl−–Na+–Cl− bridges (CN(Na+) = 6) in a three-dimensional framework, so the structure is the same as for Na2Gd4ONCl9. Different influences shape the layout of the individual chains as described in the following paper.

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