Synthesis, Computational Studies, Inelastic Neutron Scattering, Infrared and Raman Spectroscopy of Ruthenocene

Abstract

In this work we report a new and simplified synthesis of ruthenocene that prevents the formation of unwanted by‐products. We have also revisited the vibrational spectroscopy of this iconic molecule and in addition to infrared and variable temperature Raman spectra, we present the first inelastic neutron scattering (INS) spectrum, a technique that is little used in inorganic chemistry. The Raman spectra in the low energy range (< 200 cm–1) clearly show that the mode assigned as the ring–Ru–ring torsion is a librational mode. By generating the INS spectra predicted by previous assignment schemes we are able to show that they are all, at least partially, wrong because they fail to correctly predict the experimental INS spectrum. In the case of ruthenocene, the addition of INS data, in combination with periodic‐DFT calculations, has enabled the first correct assignment of the internal modes of ruthenocene. This straightforward means to test proposed assignments is one of the great strengths of vibrational spectroscopy with neutrons.