An infrared study of CO activation by holmium ions, Ho and HoO.

We report a combined experimental and computational study of carbon dioxide activation at gas-phase Ho and HoO centres. Infrared action spectra of Ho(CO) and [HoO(CO)] ion-molecule complexes have been recorded in the spectral region 1700-2400 cm and assigned by comparison with simulated spectra of energetically low-lying structures determined by density functional theory. Little by way of activation is observed in Ho(CO) complexes with CO binding end-on to the Ho ion. By contrast, all [HoO(CO)] complexes ≥ 3 show unambiguous evidence for formation of a carbonate radical anion moiety, . The signature of this structure, a new vibrational band observed around 1840 cm for = 3, continues to red-shift monotonically with each successive CO ligand binding with net charge transfer from the ligand rather than the metal centre.