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, <sup>Messup>PDI<sup>Mesup> (<sup>Messup>PDI<sup>Mesup> = 2,6-((Mes)N鈺怌Me)<sub>2sub>-C<sub>5sub>H<sub>3sub>N, Mes = 2,4,6-trimethylphenyl), has been synthesized. Using either Cp* or Cp<sup>Psup> (Cp* = 1,2,3,4,5-pentamethylcyclopentadienide, Cp<sup>Psup> = 1-(7,7-dimethylbenzyl)cyclopentadienide), uranium complexes of the type Cp<sup>Xsup>UI<sub>2sub>(<sup>Messup>PDI<sup>Mesup>) (1-Cp<sup>Xsup>; X = * or P), Cp<sup>Xsup>UI(<sup>Messup>PDI<sup>Mesup>) (2-Cp<sup>Xsup>), and Cp<sup>Xsup>U(<sup>Messup>PDI<sup>Mesup>)(THF)<sub>nsub> (3-Cp<sup>Xsup>; *, n = 1; P, n = 0) were isolated and characterized. The series was generated via ligand centered reduction events; thus the extent of <sup>Messup>PDI<sup>Mesup> reduction varies in each case, but the uranium(IV) oxidation state is maintained. Treating 2-Cp<sup>Xsup>, which has a doubly reduced <sup>Messup>PDI<sup>Mesup>, with furfural results in radical coupling between the substrate and <sup>Messup>PDI<sup>Mesup>, leading to C鈥揅 bond formation to form Cp<sup>Xsup>UI(<sup>Messup>PDI<sup>Mesup>-CHOC<sub>4sub>H<sub>3sub>O) (4-Cp<sup>Xsup>). Exposure of 3-Cp* and 3-Cp<sup>Psup>, which contain a triply reduced <sup>Messup>PDI<sup>Mesup> ligand, to benzaldehyde and benzophenone, respectively, results in the corresponding pinacolate complexes Cp*U(O<sub>2sub>C<sub>2sub>Ph<sub>2sub>H<sub>2sub>)(<sup>Messup>PDI<sup>Mesup>) (5-Cp*) and Cp<sup>Psup>U(O<sub>2sub>C<sub>2sub>Ph<sub>4sub>)(<sup>Messup>PDI<sup>Mesup>) (5-Cp<sup>Psup>). 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 <sup>1sup>H NMR and electronic absorption spectroscopies, and SQUID magnetometry was employed to confirm the mono(anionic) [<sup>Messup>PDI<sup>Mesup>]<sup>鈭?/sup> ligand in 1-Cp<sup>Psup> and 5-Cp<sup>Psup>. Structural parameters of complexes 1-Cp<sup>Psup>, 2-Cp<sup>Xsup>, 4-Cp*, and 5-Cp<sup>Xsup> have been elucidated by X-ray crystallography.