Synthesis, crystal structure, vibrational spectroscopy, and thermal behaviour of lead dicyanamide Pb[N(CN)2]2

Lead dicyanamide, Pb[N(CN)(2)](2), was synthesized through ion exchange in water starting from Na[N(CN)(2)]. The crystal structure was determined by single-crystal X-ray diffraction (Pnma, Z = 4, a = 1350.45(10), b = 399.89(4), c = 1199.39(11) pm, R-1 = 0.0275, wR(2) = 0.0557, 68 parameters, 1073 independent reflections). In the solid Pb[N(CN)(2)](2) consists of Pb2+ ions and bent planar [N(CN)(2)](-) ions. The dicyanamide anions exhibit C-N bond lengths of 114.0(13)-116.0(10) pm to the terminal and 128.8(11)-131.9(12) pm to the bridging N atoms. The bond angles within the [N(CN)(2)](-) ions are 173.1(8)-174.5(10)degrees (N-C=N) and 122.0(8)degrees (C-N-C). The crystal structure of Pb[N(CN)(2)](2) is isotypic with that of Ba[N(CN)(2)](2). It can be derived from the cotunnite structure type (PbCl2). Above 230 degreesC Pb[N(CN)212 transforms into amorphous products. Detailed IR spectroscopic data of Pb[N(CN)(2)](2) are reported. The observed frequencies agree well with those observed for isotypic Ba[N(CN)(2)](2). (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.