NQR and X-ray crystal structure studies of cadmium halide complexes: [C(NH2)3]CdI3 and [4-ClC6H5NH3]3CdBr5

The crystal structures of [C(NH2)(3)]CdI3 (1) and [4-ClC6H5NH3](3)CdBr5 (2) have been determined at 100 K: monoclinic, Cc, a = 828.75(3) pm, b = 1615.31(5) pm, c = 810.64(3) pm, and beta = 106.5820(10)degrees for 1; monoclinic, P2(1)/c, a = 1486.93(5) pm, b = 794.31(3) pm, c = 2290.59(7) pm, and beta = 99.6830(10)degrees for 2. The structure of 1 has an infinite chain of anions consisting of [CdI4] tetrahedra sharing two corners. The structure of 2 has an infinite chain of anions consisting of [CdBr6] octahedra sharing two corners in cis positions. In both structures, isolated cations are connected to the anion chains through weak hydrogen bonds Cd-X center dot center dot center dot H to result in three-dimensional network structures. In accordance with the crystal structures, three I-127 (m = +/- 1/2. m = +/- 3/2), five Br-81, and three Cl-35 nuclear quadrupole resonance (NQR) lines were observed for 1 and 2. The NQR spectra reflect the anion chain structures and their weak hydrogen bonds. The MO calculations of the models [Cd5I16](6-) for 1 and [Cd3Br16](10-) for 2 estimate only about half the values for the NQR frequencies but give accurate electric field gradient directions.