The octahedral U(V) complexes recently reported by Hayton and co-workers represent a unique opportunity to directly probe the strengths of p and s interactions between the uranium f-orbitals and a variety of ligands. These octahedral complexes, [UX6]-, consist of pentavalent uranium coordinated by a variety of ligands including alkyl (X = CH2SiMe3), alkoxide (X = OtBu), amide (X = NC5H10), and ketimide (X = N=CtBuPh). This family of complexes is ideal for studying f-orbital bonding it spans a range of commonly used ligands in organouranium chemistry, and the spectroscopic data necessary to investigate the bonding is available. The bonding in these compounds may be compared to that in the well-known halide complexes ([UX6]-, X = F, Cl, Br; PaCl62-; NpF6), which have been extensively investigated. In this study, we develop an MO model based on earlier work by Thornley, but reduced, orbital-specific spin-orbit coupling constants are used rather than a single spin-orbit coupling constant. This model is used to fit the optical and EPR spectra for the octahedral f1 complexes, and is in excellent agreement with the experimental results. The new model is compared to the venerable Crystal Field model and the Thornley MO model using a single spin-orbit coupling constant. The new model involves much less covalency than the original MO model, yet this covalency plays a large role in determining the strength of the interaction between the f-orbitals and the ligand orbitals.

Investigating the [sigma]- and π-interactions between U(V) and halide, alkoxide, amide, and ketimide ligands

245th National Meeting (2013)

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