Multielectron C鈥揙 Bond Activation Mediated by a Family of Reduced Uranium Complexes

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• 作者：John J. Kiernicki ; Brian S. Newell ; Ellen M. Matson ; Nickolas H. Anderson ; Phillip E. Fanwick ; Matthew P. Shores ; Suzanne C. Bart
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：April 7, 2014
• 年：2014
• 卷：53
• 期：7
• 页码：3730-3741
• 全文大小：493K
• 年卷期：v.53,no.7(April 7, 2014)
• ISSN：1520-510X

文摘

A family of cyclopentadienyl uranium complexes supported by the redox-active pyridine(diimine) ligand, ^MesPDI^Me (^MesPDI^Me = 2,6-((Mes)N鈺怌Me)₂-C₅H₃N, Mes = 2,4,6-trimethylphenyl), has been synthesized. Using either Cp* or Cp^P (Cp* = 1,2,3,4,5-pentamethylcyclopentadienide, Cp^P = 1-(7,7-dimethylbenzyl)cyclopentadienide), uranium complexes of the type Cp^XUI₂(^MesPDI^Me) (1-Cp^X; X = * or P), Cp^XUI(^MesPDI^Me) (2-Cp^X), and Cp^XU(^MesPDI^Me)(THF)_n (3-Cp^X; *, n = 1; P, n = 0) were isolated and characterized. The series was generated via ligand centered reduction events; thus the extent of ^MesPDI^Me reduction varies in each case, but the uranium(IV) oxidation state is maintained. Treating 2-Cp^X, which has a doubly reduced ^MesPDI^Me, with furfural results in radical coupling between the substrate and ^MesPDI^Me, leading to C鈥揅 bond formation to form Cp^XUI(^MesPDI^Me-CHOC₄H₃O) (4-Cp^X). Exposure of 3-Cp* and 3-Cp^P, which contain a triply reduced ^MesPDI^Me ligand, to benzaldehyde and benzophenone, respectively, results in the corresponding pinacolate complexes Cp*U(O₂C₂Ph₂H₂)(^MesPDI^Me) (5-Cp*) and Cp^PU(O₂C₂Ph₄)(^MesPDI^Me) (5-Cp^P). The reducing equivalents required for this coupling are derived solely from the redox-active ligand, rather than the uranium center. Complexes 1鈥?b>5 have been characterized by ¹H NMR and electronic absorption spectroscopies, and SQUID magnetometry was employed to confirm the mono(anionic) [^MesPDI^Me]^{鈭?/sup> ligand in 1-CpP and 5-CpP. Structural parameters of complexes 1-CpP, 2-CpX, 4-Cp*, and 5-CpX have been elucidated by X-ray crystallography.}