Crystal Structures of Piperazinium Tetrahalogenometallates (II) [C4H12N2]MX4 (M = Zn, Hg; X = Br, I)

Abstract

The crystal structures of piperazinium tetrahalogenometallates (II) [C4H12N2]MX4(M = Zn, Hg; X = Br, I), orthorhombic with space group P212121 and Z = 4 are isostructural with [C4H12N2]CdI4. The structure consists of piperazinium cations and isolated tetrahedralMX4 anions. [C4H12N2]ZnBr4 (1): a = 850.4(2), b = 1146.5(3), and c = 1228.4(4) pm at 300(2) K, [C4H12N2]ZnI4 (2): a = 886.89(6), b = 1209.11(9), and c = 1293.79(9) pm at 223(2) K, [C4H12N2]HgBr4 (3): a = 865.48(14), b = 1158.7(3), and c = 1233.3(2) pm at 293(2) K, [C4H12N2]HgI4 (4): a = 899.6(2), b = 1230.0(2), and c = 1299.5(3) pm at 293(2) K. All crystals show a structural phase transition at about 560 K and decomposition temperatures above 600 K. The lattice stability of the crystals is well explained by N-H · · · X hydrogen bond networks.