Resonance Raman spectra of chlorotetra-acetato- and chlorotetrabutyrato-diruthenium
Abstract
The metal–metal bonded species [Ru2Cl(O2CMe)4] and [Ru2Cl(O2CPr)4] both display a resonance Raman spectrum when irradiated with exciting lines which approach the wavenumber of the first electronic band maximum of each compound. The spectra are characterised in both cases by an overtone progression in the metal–metal stretching frequency, ν1(Ru–Ru)a1g, reaching 5ν1 for [Ru2Cl(O2CMe)4] and 4ν1 for [Ru2Cl(O2CPr)4]. Additionally, in the case of [Ru2Cl(O2CMe)4] a second progression has been observed, extending as far as ν2+ 3ν1, where ν2 is the ν2(Ru–O)a1g fundamental. The observation of such overtone progressions permits the determination of the spectroscopic constants ω1 and X11 for each molecule. The results form the basis for reassigning the electronic band in the visible region (the resonant electronic transition) of these compounds to the b1uâ†�b2g(δ*â†�δ) transition of the ruthenium–ruthenium moiety.