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) (1), 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(CH2SiMe2NSiMe3)­(NR2)2, then a second product is also formed in the reaction with S8, namely, [(R2N)3U]2(μ-η2:η2-S2) (2). This species can be separated from 1, 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 (3), Te (4)) in moderate yields. Complexes 1–4 were fully characterized, including analysis by X-ray crystallography.