Soft X-ray signatures of cationic manganese-oxo systems, including a high-spin manganese() complex

Manganese-oxo species catalyze key reactions, including C-H bond activation or dioxygen formation in natural photosynthesis. To better understand relevant reaction intermediates, we characterize electronic states and geometric structures of [MnO n ] + manganese-oxo complexes that represent a wide range of manganese oxidation states. To this end, we apply soft X-ray spectroscopy in a cryogenic ion trap, combined with multiconfigurational wavefunction calculations. We identify [MnO 2 ] + as a rare high-spin manganese( v ) oxo complex with key similarities to six-coordinated manganese( v ) oxo systems that are proposed as reaction intermediates in catalytic dioxygen bond formation. Limitations in synthesis of high-valent metal-oxo complexes are circumvented by trapping a series of ionic Mn-oxo complexes. One of them is a rare high-spin Mn( v )-oxo, which can serve as a template to identify similar intermediates in catalysis.