Raman spectra and solvent-solute interaction of mercury(II)-thiocyanate complexes in some aprotic donor solvents

Raman spectra of the species Hg(SCN)(2), [Hg(SCN)(3)], and [Hg(SCN)(4)](2-) in solution of ten aprotic donor solvents have been investigated in the region of the Hg-S vibration. Observed frequency values of measured band of Hg(SCN)(2) and [Hg(SCN)(3)](-) in different solutions correlate well with donor strength of the solvents. There is a linearity between HS-S frequency decreasing and increasing of the interaction of the solvent molecules with the mercury (II) ion in the thiocyanate complexes. No significant frequency changes have be found for [Hg(SCN)(4)](2-). Evidence based on the frequency shifts and depolarization ratios in various solvents supports the view that the Hg(SCN)(2) in solution undergos departure from linearity as a result of increasing solvent coordination to the mercury (II) ion. Almost constant frequencies of Hg-S vibration of [Hg(SCN)(4)](2-) in all investigated solvents suggest a regular tetrahedral structure of the ion in solution having much larger radius than corresponding HgX(4)(2-) (X=Cl,Br,I) ions.