Synthesis and characterization of the rare-earth dicyanamides Ln[N(CN)(2)](3) with Ln = La, Ce, Pr, Nd, Sm, and Eu

The rare-earth dicyanamides Ln[N(CN)(2)](3) (Ln = La, Ce, Pr, Nd, Sm, Eu) were obtained via ion exchange in aqueous medium and subsequent drying: The crystal structures were solved and refined based on X-ray powder diffraction data and they were found to be isotypic: Ln[N(CN)(2)](3); Cmem (no. 63), Z = 4, Ln = La: a = 799.88(9) pm, b = 11 58.2(1) pin, c = 1026.7(1) pm; Cc: a = 794.94(3) pm, b = 1152.15(4)pm, c = 1020.96(4)pm; Pr: a = 790.45(5)pm, b = 1146.19(6)pm, c = 1016.74(6)pm; Nd: a 787.79(3)pm, b = 1144.59(4)pm, c = 1015.54(4)pm; Sm: a = 781.30(5)pm, b = 1138.64(6)pm, c = 1012.04(5)pm; Eu: a 776.7(1)pm, b = 113 5. 1 (1) pm, c = 10 1 3.7(1) pm). The compounds represent the first dicyanamides with trivalent cations. The Ln(3+) ions are coordinated by three bridging N atoms and six terminal N atoms of the dicyanamide ions forming a three capped trigonal prism. The structure type is related to that of PuBr3. The novel compounds Ln[N(CN)(2)](3) have been characterized by IR and Raman spectroscopy (Ln = La) and the thermal behavior has been monitored by differential scanning calorimetry (Ln = Ce, Nd, Eu). (C) 2004 Elsevier Inc. All rights reserved.