title: Anomalous one-electron processes in the chemistry of uranium nitrogen multiple bonds.
abstract: Novel reaction pathways are illustrated in the synthesis of uranium(IV), uranium(V), and uranium(VI) monoimido complexes. In contrast to the straightforward preparation of U(V)(═NSiMe3)[N(SiMe3)2]3 (1), the synthesis of a uranium(V) tritylimido complex, U(V)(═NCPh3)[N(SiMe3)2]3 (4), from U(III)[N(SiMe3)2]3 and Ph3CN3 was found to proceed through multiple one-electron steps. Whereas the oxidation of 1 with copper(II) salts produced the uranium(VI) monoimido complexes U(VI)(═NSiMe3)X[N(SiMe3)2]3 (X = Cl, Br), the reaction of 4 with CuBr2 undergoes sterically induced reduction to form the uranium(VI) monoimido complex U(VI)(═NCPh3)Br2[N(SiMe3)2]2, demonstrating a striking difference in reactivity based on imido substituent. The facile reduction of compounds 1 and 4 with KC8 allowed for the synthesis of the uranium(IV) monoimido derivatives, K[U(IV)(═NSiMe3)[N(SiMe3)2]3] (1-K) and K[U(IV)(═NCPh3)[N(SiMe3)2]3] (4-K), respectively. In contrast, an analogous uranium(IV) monoimido complex, K[U(IV)(═NPh(F))[N(SiMe3)Ph(F)]], Ph(F) = -pentafluorophenyl (6), was prepared through a loss of N(SiMe3)2Ph(F) concomitant with one-electron oxidation of a uranium(III) center. The uranium(IV) monoimido complexes were found to be reactive toward electrophiles, demonstrating N-C and N-Si single bond formation. One-electron reduction of nitrite provided a route to the uranium(VI) oxo/imido complex, [Ph4P][U(VI)O(═NSiMe3)[N(SiMe3)2]3]. The energetics and electrochemical processes involved in the various oxidation reactions are discussed. Finally, comparison of the U(VI)(═NSiMe3)X[N(SiMe3)2]3, X = Cl, Br, complexes with the previously reported U(VI)OX[N(SiMe3)2]3, X = Cl, Br, complexes suggested that the donor strength of the trimethylsilylimido ligand is comparable to the oxo ligand.
authors.affiliation: P. Roy and Diana T. Vagelos Laboratories, Department of Chemistry, University of Pennsylvania , 231 South 34th Street, Philadelphia, Pennsylvania 19104, United States.
authors.forename: Kimberly C
authors.initials: KC
authors.lastname: Mullane
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Lewis
authors.forename: Haolin
authors.initials: H
authors.lastname: Yin
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Carroll
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Schelter