Structure and Spectroscopy of Triruthenium Dodecacarbonyl, Ru ₃ (CO) ₁₂

We have reinvestigated the structure and vibrational spectroscopy of triruthenium dodecacarbonyl, Ru₃(CO)₁₂, in the solid state by neutron powder diffraction, inelastic neutron scattering (INS), infrared and Raman spectroscopies. We find that the known room temperature <i>P</i>2₁/<i>n</i> structure is maintained down to 10 K. The unit-cell parameters follow a Debye relationship, with an overall 5.9% volume contraction from 300 to 10 K. The high resolution data at 10 K has enabled the most precise determination of the structure to date. INS spectroscopy, which has no selection rules, has allowed the observation of all the fundamentals below 700 cm^-1 for the first time. In combination with new low temperature infrared and Raman spectra, this has resulted in the reassignment of several of the modes. Our previous work has shown that density functional theory calculations of the vibrational spectra of metal carbonyls produces mixed results. For M(CO)₆, M = Cr, Mo, W the calculated spectra are in good agreement with the experimental spectra, whereas for Fe(CO)₅, and Fe₂(CO)₉ the agreement was poor. We find that for Ru₃(CO)₁₂ the agreement is also poor.