S. Sasic et al., RAMAN-STUDY OF SOLVENT-SOLUTE INTERACTIONS IN SOLUTIONS OF MERCURY(II)-THIOCYANATE COMPLEXES, Journal of Raman spectroscopy, 29(4), 1998, pp. 321-325
Raman spectra of the Hg(SCN)(2), [Hg(SCN)(3)](-) and [Hg(SCN)(4)](2-)
complex species in solution were investigated for 10 donor solvents in
the v(CN) and v(CS) wavenumber regions. Attempts were made to relate
the solvent donor strength to overall vibrational properties of the co
mplexes. A good correlation of v(CN) with v(HgS) and consequently with
solvent donor properties was found in solutions of Hg(SCN)(2) and [Hg
(SCN)(3)](-). Wavenumber differences Delta (v) over tilde(CN), calcul
ated as the difference between wavenumbers of coordinated and free SCN
- ligands, correlate well with the solvent donor strength scale, D-s.
The Delta (v) over tilde(CN) values for Hg(SCN)(2) and [Hg(SCN)(3)](-)
can be used as an indicator of solvent donor capacity. Data derived f
rom the Delta v(CN) shifts show a better correlation with solvent dono
r ability than those obtained from the v(CS) wavenumber. The spectral
properties of [Hg(SCN)(4)](2-) complex depend only on the electrophili
c properties of the solvent and not on its donor strength, because sol
vent molecules cannot penetrate into the first coordination sphere and
donate an electron pair to Hg(II). Solvent electrophilic interaction
with coordinated thiocyanate is proportional to its acceptor number.