Resonance Raman spectra of bis (2,4-pentanedithionate) palladium (II) complex

Resonance Raman (RR) spectra of the bis (2,4-pentanedithionate) Pd(II) complex were measured upon excitation into the main band in the visible region of the electronic absorption spectra (λmax=513 nm in benzene,λmax=520 nm in CS2) and into its short wavelength shoulder (λmax=458 nm in benzene;λmax=469 nm in CS2). Only three of the eight totally symmetric normal vibrations of the complex are RR active. These modes consist predominantly of the symmetric stretch and the ring deformation. Totally symmetric Pd-S and stretching vibrations are inactive. The molecular geometry changes accompanying the resonant electronic transition are thus localized entirely on the ligand. This is consistent with a strongly localized metal-to-ligand charge transfer (MLCT) character of the transitions. The symmetry of the terminal ligand π* orbital involved in the transitions as determined from the RR spectra is au. The main band is attributed to b2g(dxz)→au(π*) and the shoulder to the b3g(dyz)→au(π*) MLCT transition.