Terminal Metal-Oxo Species with Unusual Spin States

This chapter discusses the influence of spin state on the properties of a series of relatively new, synthetic M-oxo complexes. It focuses on M-oxo complexes with unusual spin states and paramagnetic ground states. For most of the M-oxo complexes described in the chapter, magnetic measurements are an essential tool for describing the spin state of the species, with electron paramagnetic resonance (EPR) spectroscopy being one of the preferred methods. In addition, X-ray absorption near-edge spectroscopy (XANES) is often helpful in corroborating the oxidation state of a metal center. After a short discussion about the experimental methods needed for characterization, a series of case studies on M-oxo complexes are discussed to highlight recent developments in the field. The reactivity of M-oxo complexes has been linked to a variety of oxidative transformations, with O-atom transfer (OAT) and C-H bond functionalization being the two most common types.