Actinide-Oxygen Multiple Bonds from Air: Synthesis and Characterization of a Thorium Oxo Supported by Redox-Active Ligands

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((dipp)ap)(3)] [K(15-c-5)(2)](2) (1-as crown), with dioxygen in dry air, forming a rare terminal thorium oxo, [O=Th((dipp)isq)(2)((d)(ipp)ap)][K(1S-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((dipp)isq)(2) (OSiMe3)(2) (THF) (4-OSiMe3)(4) Th(OSiMe3)(4) (bipy)(2) (5-OSiMe3), and [Th(OH)(2) ((dipp)Hap)(4)] [K(15-c-5)(2)](2) (6-OH). Full spectroscopic and structural characterization of the complexes was performed via H-1 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.

Automated summary

This study presents the first synthesis of a non-uranyl, f-element oxo complex from dioxygen in dry air. The characterization of the complexes using various spectroscopic techniques confirmed their electronic structures.