The Many Faces of Rare Earth Carbodiimide Compounds

Hans-Juergen Meyer

Solid state metathesis reactions have been established as a successful tool in syntheses of rare earth carbodiimide compounds. Current results evidence the new compounds LiRE(CN2)2 with RE = La, Ce and the carbodiimide nitride Ce3(CN2)3N. LiRE(CN2)2 compounds were synthesized by solid state metathesis reactions between REF3 and Li2(CN2) in 1 : 2 molar ratio. Ce3(CN2)3N was obtained via thermal conversion of LiCe(CN2)2. Crystal structures of LiLa(CN2)2 and Ce3(CN2)3N were determined from X-ray single crystal data (LiLa(CN2)2: P21/m, a = 542.4(2) pm, b = 379.16(7) pm, c = 1013.0(3) pm, β = 101.35(3) °; Ce3(CN2)3N: P212121, a = 672.97(9) pm, b = 1309.8(2) pm, c = 1697.7(3) pm) and LiCe(CN2)2 was assigned from indexed XRD pattern (LiCe(CN2)2: a = 541.9(1) pm, b = 374.50(8) pm, c = 1008.8(2) pm, β = 101.21(1) °). The crystal structure of LiLa(CN2)2 represents a layer-like arrangement of ions as typical for this type of compounds. The crystal structure of Ce3(CN2)3N reveals strings of [NCe4] tetrahedra running parallel to each other, and trigonal prismatic to trigonal antiprismatic arrangements of six distinctly interconnected [Ce3-NCN-Ce3] units. Both structures contain (CN2)2- ions deviating from their ideal Dh symmetry, with C–N distances ranging between 121 and 125 pm and N–C–N angles near 180 °.

Mots clés: Physical Sciences

Hans-Juergen Meyer. The Many Faces of Rare Earth Carbodiimide Compounds. Journal of Inorganic and General Chemistry / Zeitschrift für anorganische und allgemeine Chemie, 2009, 635 (12), pp.1947. ⟨10.1002/zaac.200900221⟩. ⟨hal-00520636⟩