科研之友
微信
新浪微博
Facebook
分享链接
摘要
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)Br-2[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(=NPhF)[N(SiMe3)Ph-F]], Ph-F = -pentafluorophenyl (6), was prepared through a loss of N(SiMe3)(2)Ph-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][(UO)-O-VI(=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 (UOX)-O-VI[N(SiMe3)(2)](3), X = Cl, Br, complexes suggested that the donor strength of the trimethylsilylimido ligand is comparable to the oxo ligand.
- 出版日期2014-9-1
