Chains of trans-edge connected [ZM 4] tetrahedra (Z = N and O) in the lanthanide nitride chlorides M 2NCl 3 and Na 2M 4ONCl 9 (M = La–Nd)

Abstract

Single crystals of La 2NCl 3 and Na 2Nd 4ONCl 9 were prepared from LaCl 3, La and NaN 3 or NdCl 3, NdOCl, Nd and NaN 3 (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. La 2NCl 3 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 Na 2Nd 4ONCl 9 crystallizes in space group P2 1/ 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 [ZM 4] tetrahedra in { [ Z M 4 / 2 e ] x + } ∞ 1 chains (M 2NCl 3: M = La, Z = N, x = 3.0; Na 2M 4ONCl 9: 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 La 2NCl 3 and are connected via trans-edge sharing [(Cl1)La 4] 11+ tetrahedra in the same way as the [NLa 4] 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 M 2NCl 3 (M = La–Nd, Gd) crystallize in two different orthorhombic space groups. La 2NCl 3 is structurally isotypic with Ce 2NCl 3 and Pr 2NCl 3 (space group: Ibam), while Nd 2NCl 3 and Gd 2NCl 3 crystallize similarly, but in space group Pbcn. In Na 2Nd 4ONCl 9 the connection between the zigzag chains of trans-edge shared [ZNd 4] 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 Na 2Gd 4ONCl 9. Different influences shape the layout of the individual chains as described in the following paper.