Syntheses and Spectroscopic Properties of Halocadmates(II): Crystal and Molecular Structure of a New Tribromo[N-Benzylpiperazinium]Cadmium(II) Compound

Compounds of formula [CdX4]·(LH2)·(H2O) (LH2 = N-benzylpiperazinium dication X = Cl, Br, I) and one of formula [CdBr3(LH)] (LH = N-benzylpiperazinium monocation) wem prepared and characterized. The crystal structure of the monoprotonated N-benzylpiperazinium tribromocadmate(II) complex was determined by means of X-ray analysis. The [CdBr3·(LH)] salt is triclinic (space group and lattice constants: P1, a = 9.500(3), b = 13.145(7), c = 6.801(1) Å, α = 103.79(2), β = 96.24(2), γ = 96.17(5)°, Z = 2, R = 0.0392, Rw = 0.0394). Its structure consists of discrete monomeric [CdBr3(LH)] units, in which the coordination polyhedron around the cadmium ion is a distorted tetrahedron. The coordination sphere is comprised of the three anionic bromide ligands and one terminal N atom of the N-benzylpiperazinium monocation. All the compounds were also investigated by means of IR and Raman spectroscopic measurements. The CdBr stretching vibrations of the structurally known [CdBr3·(LH)] salt were unambiguously assigned on the basis of calculations performed on its spectra and by comparison with literature data. The Cd-X stretching vibrations of the [CdX4]·(LH2)·(H2O) compounds, assigned by comparing their spectra with those of the monoprotonated N-benzylpiperazinium tribromocadmate and on the basis of literature data, strongly suggest the presence of discrete [CdX4]2- anions.