II Chloride Thiourea Complexes

Four different thiourea complexes of mercury(II) are easily prepared from aqueous solutions of mercury(II) chloride and thiourea. The proportions of reagents are not as critical as the temperature, elevation of which results in precipitation of black mercury (II) sulfide. Electrical conductivities and freezing points provide evidence for the constitution of the complexes. 

Equimolar proportions of mercury (II) chloride (27.15 g.) and thiourea (7.61 g.) in aqueous solution are heated together on a water bath for a short time. The cooled white precipitate of needle-shaped crystals may be washed with small quantities of cold water and dried on filter paper, or with alcohol followed by drying in vacuo.% 

Rosenheim and Y. J. Meyer assigned the formula Hg(CSN2H4)Cl2T/2H20 to the water-washed crystals of melting point 234° (with decomposition) and gave the fol- 

This can be prepared simply by stirring a cold, practically saturated aqueous solution of mercury (II) chloride into a cold, practically saturated aqueous solution of thiourea until the white precipitate (of the di-derivative) almost entirely redissolves. Large, colorless crystals separate out when the solution is filtered and allowed to evaporate at ordinary temperature, say, in a vacuum desiccator. The crystals may be dissolved in hot water, whereupon little decomposition takes place, and square microscopic platelets crystallize out of the filtered solution on cooling. The dried crystals sinter at about 174° and begin to decompose at about 179°. The yield is only moderately good. Anal. Calcd. for HgCl2-3CSN2H4 N, 16.80. Found N, 16.76, 16.89. 

The tetra-derivative, which is described in Beilstein6 as easily soluble in water, in fact gives barely a 1% solution at 0°. At room temperature the solubility is higher but only about one-fourth that of mercury(II) chloride and one-sixth that of thiourea. The tri-derivative is still less soluble in water, giving a 0.2% solution at 0°, and the mono-derivative even less so. The least soluble is the di-derivative which is precipitated on mixing 0.1% solutions of mercury-(II) chloride and thiourea.2 It is also virtually insoluble in brine and alcohol2 and only sparingly soluble in hydrochloric acid.1 

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