Actinide–Oxygen Multiple Bonds from Air: Synthesis and Characterization of a Thorium Oxo Supported by Redox-Active Ligands
D. M. Ramitha Y. P. Rupasinghe, Makayla R. Baxter, Himanshu Gupta, Andrew T. Poore, Robert F. Higgins, Matthias Zeller, Shiliang Tian, Eric J. Schelter, Suzanne C. Bart
Abstract
The first non-uranyl, f-element oxo complex synthesized from dioxygen in dry air is presented in this work. The synthesis was accomplished by treating the redox-active thorium amidophenolate complex, [Th(dippap)3][K(15-c-5)2]2 (1-ap crown), with dioxygen in dry air, forming a rare terminal thorium oxo, [O═Th(dippisq)2(dippap)][K(15-c-5)2]2 (2-oxo). Compound 1-ap crown was regenerated by treating 2-oxo with potassium graphite. X-ray crystallography of 2-oxo revealed a comparatively longer bond length for the thorium–oxygen double bond when compared to other thorium oxos. As such, several thorium–oxygen single bonds were synthesized for comparison, including Th(dippisq)2(OSiMe3)2(THF) (4-OSiMe3), Th(OSiMe3)4(bipy)2 (5-OSiMe3), and [Th(OH)2 (dippHap)4][K(15-c-5)2]2 (6-OH). Full spectroscopic and structural characterization of the complexes was performed via 1H NMR spectroscopy, X-ray crystallography, EPR spectroscopy, and electronic absorption spectroscopy as well as SQUID magnetometry, which all confirmed the electronic structure of these complexes.