Piperazinium and N-Methyl-Piperazinium Tetrahalocadmates(II) Containing Discrete [CdX4]2- units

Compounds of formula [CdX4] LH2·nH2O (LH2=piperazinium dication; XCl, Br, I; n=1 for Cl and Br. LH2N-methylpiperazinium dication; XCl, Br, I; n=O) were prepared and characterized. The crystal structure of the piperazinium tetrabromocadmate(II) monohydrated complex was also determined by means of X-ray analysis. The [CdBr4]·(pipzn)·(H2O) (pipzn=piperazinium dication) salt is monoclinic (space group and lattice constants:P2/c, a=6.887(4), b=13.429(8), c= 14.260(9) Å, β=92.82(5)o Z=4, R=0.072, Rw=0.073). Its structure consists of discrete monomeric [CdBr4]2- anions, piperazinium dications and water molecules. Coordination around the cadmium ion is a very slightly distorted tetrahedron. All the compounds were also investigated by means of IR and Raman spectroscopic measurements and in particular the CdX stretching vibrations were discussed and unambiguously assigned on the basis of calculations performed on the spectra of the structurally known piperazinium tetrabromocadmate(II) monohydrate compound and of literature data.