Isolated versus Condensed Anion Structure VI: X-ray Structure Analysis and 81 Br NQR of Guanidinium Pentabromodicadmate(II), [C(NH2)3]Cd2Br5, fns-Hydrazinium Pentabromocadmate(II), [H2NNH3]3CdBr5, and fo's-Hydrazinium Tetrabromocadmate(II)-Tetra Hydrate, [H2NNH3]2CdBr4-4H20

The structure of the condensed bromocadmate anions in [C(NH2)3]Cd2Br5 (1) and [H2NNH3]3CdBr5 (2) were studied at room temperature by X-ray diffraction. (1) crystallizes with double-chains bridged by Br atoms (orthorhombic, Pmmn, Z = 2, a = 1394.0(5), b = 394.5(1), c = 1086.9(5) pm). This chain structure was not described previously. (1) shows three 8 'Br NQR lines at temperatures between 77 and 323 K. Structural phase transitions take place at 283 K and at 535 K. (2) crystallizes with Br bridged zigzag-chains (monoclinic, P2[, Z=2,a = 943.1(1), b = 778.8(2), c = 942.0(2) pm, ß = 102.10(2)°) and shows a first-order phase transition around 304 K with a large thermal hysteresis. Below the transition point five 81 Br NQR lines are observed at temperatures between 122 and 304 K, and above the transition point four 81 Br NQR lines at temperatures between 288 and 353 K. Two 81 Br NQR lines are observed in [H2NNH3]2CdBr4-4H20 (3) at temperatures between 77 and around 320 K with positive temperature coefficients.