The structure of ruthenium pentacarbonyl: comparison to iron pentacarbonyl

Of the metal carbonyls, iron pentacarbonyl, Fe(CO)5, is iconic: it was first reported in 1891 and was only the second metal carbonyl to be discovered, the structure is that of a trigonal bipyramid. There is no neutron diffraction data for Fe(CO)5. The only characterisation of the ruthenium congener of Fe(CO)5, Ru(CO)5, is a gas phase electron diffraction structure and infrared spectra in the C≡O stretch region. We propose to carry out the first structural and spectroscopic (a parallel proposal for TOSCA has been submitted) characterisation of Ru(CO)5. As the only structural determinations of Fe(CO)5, were carried out near the melting point, we also wish to measure this at 10 K for comparison with the INS data. This work will allow a detailed structural comparison of Fe(CO)5 and Ru(CO)5, in particular there is still debate as to whether the equatorial and axial M–C bonds are different.