REMARKABLE INFLUENCE OF X AND R ON THE CHARGE-TRANSFER CHARACTER (MLCT OR XLCT) OF THE COMPLEXES [RU(X)(R)(CO)2(L)] (X=HALIDE, CF3SO3 R=ALKYL L=ALPHA-DIIMINE) - A UV-VIS ABSORPTION AND RESONANCE RAMAN-STUDY

Complexes of the type [Ru(X)(R)(CO)2(L)] (X = halide, CF3SO3; R = alkyl; L = N,N'-diisopropyl-1,4-diaza-1,3-butadiene, pyridine-2-carbaldehyde N-isopropylimine, 2,2'-bipyridine) experience significant influences of X and R on the energies and relative intensities of their lowest-energy electronic transitions. The halide complexes show two absorption bands in the visible region, which are assigned to two sets of charge transfer transitions from mixed metal-halide orbitals. Variation of the halide from Cl to I gives rise to a change in character of the lowest-energy band from MLCT to XLCT, as evidenced by resonance Raman spectra. These spectra show enhancement of Raman intensity for both nu(s)(CN) and nu(s)(CO) in the case of the Cl complex, but only for mu(s)(CN) for the corresponding I complex. Variation of the alkyl ligand from Me to iPr leads to a shift of both absorption bands to lower energy with a concomitant change of their relative intensities. The tatter effect is again ascribed to a change of charge transfer character of the electronic transitions.