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 mea sured band of Hg(SCN)(2) and [Hg(SCN)(3)](-) in different solutions co rrelate well with donor strength of the solvents. There is a linearity between HS-S frequency decreasing and increasing of the interaction o f the solvent molecules with the mercury (II) ion in the thiocyanate c omplexes. No significant frequency changes have be found for [Hg(SCN)( 4)](2-). Evidence based on the frequency shifts and depolarization rat ios in various solvents supports the view that the Hg(SCN)(2) in solut ion undergos departure from linearity as a result of increasing solven t coordination to the mercury (II) ion. Almost constant frequencies of Hg-S vibration of [Hg(SCN)(4)](2-) in all investigated solvents sugge st a regular tetrahedral structure of the ion in solution having much larger radius than corresponding HgX(4)(2-) (X=Cl,Br,I) ions.