Chains of [RE6] Octahedra Coupled by (NCN) Links in the Network Structure of RE2Cl(CN2)N. Synthesis and Structure of Two Novel Rare Earth Chloride Carbodiimide Nitrides with Structures Related to the RE2Cl3 Type

Solid state metathesis reactions between RECl3 (RE = La, Ce) and Li2CN2 at 800 °C have led to the discovery of the rare earth chloride carbodiimide nitrides La2Cl(CN2)N (1) and Ce2Cl(CN2)N (2), respectively. Single crystal X-ray diffraction analyses revealed that 1 and 2 crystallize isotypic in an orthorhombic system (Cmmm, Z = 4, a = 13.3914(8) Å, b = 9.6345(7) Å, c = 3.9568(2) Å for 1 and a = 13.340(1) Å, b = 9.5267(8) Å, c = 3.9402(5) Å for 2). The crystal structures of 1 and 2 contain linear chains of edge-sharing octahedra built from rare earth metal atoms. Similar to [M6X8] type clusters, the [RE6] octahedra are capped by eight nitrogen atoms above their faces, of which four are from N3- ions and the other four are from (CN2)2- ions. The chains are interconnected by bridging (CN2)2- to form a three-dimensional network with Cl- ions in linear channels. Compounds 1 and 2 are surprisingly stable toward air and water. They have been characterized by thermal analysis, infrared spectroscopy, and magnetic susceptibility studies.