"Spectroscopic and structural investigation on tetrahalomercurates(II). Crystal and molecular structures of bis(N-ethylmorpholinium)tetrachloro-mercurate(II) and ammonium ethylmorpholinium) tetrachloromercurate (II) complexes".

Compounds of the type [LH]2HgX4 and [LH2]HgX4 [LH = N-ethylmorpholinium cation; LH2 = N-ammoniumethylmorpholinium dication; X = Cl, Br, 1] were prepared and characterized by means of Raman and far-IR spectroscopies. For two compounds [LH]2HgCl4 (A) and [LH2]HgCl4 (B), the crystal structures were also determined. Crystals of both compounds show that they are composed of discrete monomeric [HgCl4]2- units and counter-ions, [LH+] and [LH22+]. Coordination around the mercury atoms is distorted tetrahedral, arising from hydrogen bonding. In compound (A) there is one long (2.559(5) Å) and three short (av. 2.456(15) Å) HgCl distances, while in compound (B) a continuous range of HgCl distances (2.395(3)-2.562(3) Å) is present. The deviations from tetrahedral geometry of the [HgCl4]2- units do not play a significant role in vibrational spectra.