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 S-8 to U(NR2)(3) (R = SiMe3) in Et2O generates [(R2N)(3)U](2)(mu-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 S-8, namely, [(R2N)(3)U](2)(mu-eta(2):eta(2)-S-2) (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)(3)U](2)(mu-E) (E = Se (3), Te (4)) in moderate yields. Complexes 1-4 were fully characterized, including analysis by X-ray crystallography.