The nature of chemical bonds between metals and light atoms such as oxygen, nitrogen, and carbon is of widespread interest because these interactions control the physics and chemistry of many technologically important processes. Among approaches explored previously, ligand K-edge X-ray absorption spectroscopy (XAS) has emerged as an effective method for quantitatively probing electronic structure and orbital mixing. The presence of covalent mixing is observed as a pre-edge feature in the ligand K-edge XAS, which only has transition intensity if the final state metal orbital contains a component of ligand p orbital character. Recent advances have shown that insights regarding the nature of orbital mixing can be obtained at the K-edge for oxygen through a combination of XAS with a scanning transmission X-ray microscope (STXM), non-resonant inelastic X-ray scattering (NIXS), and hybrid density functional theory calculations (DFT). Herein, a new effort is discussed that employs these techniques to probe d- and f-block bonds to oxygen and carbon atoms. Oxygen K-edge XAS measurements and DFT studies began with a series of six tetrahedral oxyanions, MO42- and MO41- (M = Cr, Mo W and Mn, Tc, Re). The lanthanide dioxides and sesquioxides, LnO2 and Ln2O3 (Ln = Ce, Pr, Tb), were chosen for subsequent work because covalency in the Ln�O bonds is already well-established from hard X-ray spectroscopies. Taken together, the research shows that orbital composition is influenced by a complex interplay between periodic changes in both orbital energy and radial extension. Efforts to evaluate M�C orbital mixing in d-block bent metallocenes and lanthanide organometallics will also be discussed.

Evaluating orbital mixing in metal�oxygen and carbon bonds using ligand K�edge X-ray absorption spectroscopy

248th National Meeting (2014)

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