Chalcogen Atom Transfer to Uranium(III): Synthesis and Characterization of [(R₂N)₃U]₂(μ-E) and [(R₂N)₃U]₂(μ‑η²:η²‑S₂) (R = SiMe₃; E = S, Se, Te)

Addition of 0.0625 equiv of S₈ to U­(NR₂)₃ (R = SiMe₃) in Et₂O generates [(R₂N)₃U]₂(μ-S) (<b>1</b>), which can be isolated in moderate yield by crystallization from cold Et₂O. Interestingly, if the U­(NR₂)₃ starting material is contaminated with the U­(IV) metallacycle U­(<i>C</i>H₂SiMe₂<i>N</i>SiMe₃)­(NR₂)₂, then a second product is also formed in the reaction with S₈, namely, [(R₂N)₃U]₂(μ-η²:η²-S₂) (<b>2</b>). This species can be separated from <b>1</b>, in low yield, by virtue of its insolubility in Et₂O. Finally, addition of 0.5 equiv of E (E = Se, Te) to U­(NR₂)₃ (R = SiMe₃) results in the formation of [(R₂N)₃U]₂(μ-E) (E = Se (<b>3</b>), Te (<b>4</b>)) in moderate yields. Complexes <b>1</b>–<b>4</b> were fully characterized, including analysis by X-ray crystallography