Spectral Evidence for Lanthanoid and Actinoid Carbonyl Compounds

The co‐condensation of actinoid or lanthanoid atoms and a mixture of argon containing small amounts carbon monoxide on a surface cooled with liquid helium leads, after annealing of the argon matrix, to a series of new binary actinoid and lanthanoid carbonyl compounds. Evidence for these new carbonyls is obtained using infrared spectroscopy. Preliminary interpretation of the IR spectra suggests that at least six complexes, M(CO)1–6, have been observed for each metal. A distinct difference in the infrared spectra is observed for the ytterbium derivative, probably associated with the fact that ytterbium lacks one electron from having entirely filled 4f orbitals. A brief description of the possible bond hybridization and its effect on the MCO bonding, which may explain the difference between ytterbium and the other lanthanoids, is presented.