Mono- and Bimetallic Alkoxides of Neptunium(IV) and Iron(III)

Although the chemistry of uranium alkoxides has been widely studied, not much attention has been paid to alkoxide chemistry of transuranic elements. In 1967, Samulski and Karraker were able to isolate a few examples of transuranic alkoxides. However, these complexes were only characterized using elemental analysis and absorption spectra. These compounds were never structurally characterized.
Based on recent achievements in synthesizing novel transuranic starting materials, we were able to isolate four mono- and bimetallic tert-butoxides with Np(IV). [Np₃O(OtBu)₁₀] and [K₄Np₂O(OtBu)₁₀] were synthesized using the ligand substitution between neptunium(IV) silylamides and HOtBu, whereas the salt metathesis between [NpCl₄(DME)₂] (DME = dimethoxyethane) and various amounts of LiOtBu resulted in the formation of the oxo-free alkoxides [Np(OtBu)₄(py)₂] (py = pyridine) and [Li(THF)]₂[Np(OtBu)₆]. To the best of our knowledge, these compounds represent the first structurally characterized Np(IV) alkoxides using single crystal X-ray diffraction and solid-state UV-vis-NIR spectroscopy. Furthermore, treatment of [Np(OtBu)₄(py)₂] with [Fe(OtBu)₃]₂ results in the formation of a heterobimetallic complex [NpFe(OtBu)₇(py)]. A solvent dependent coordination motif on both metal sides was observed, leading to the formation of [NpFe(OtBu)₇].