Radical Reductive Elimination from Tetrabenzyluranium Mediated by an Iminoquinone Ligand

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• 作者：Ellen M. Matson ; Sebastian M. Franke ; Nickolas H. Anderson ; Timothy D. Cook ; Phillip E. Fanwick ; Suzanne C. Bart
• 刊名：Organometallics
• 出版年：2014
• 出版时间：April 28, 2014
• 年：2014
• 卷：33
• 期：8
• 页码：1964-1971
• 全文大小：408K
• 年卷期：v.33,no.8(April 28, 2014)
• ISSN：1520-6041

文摘

Reductive elimination from U(CH₂Ph)₄ (1-Ph) mediated by 4,6-di-tert-butyl-2-[(2,6-diisopropylphenyl)imino]quinone (^dippiq) was observed, resulting in the formation of (^dippap)₂U(CH₂Ph)₂(THF)₂ (2) (^dippap = 4,6-di-tert-butyl-2-[(2,6-diisopropylphenyl)amido]phenolate) and bibenzyl. The crossover experiment with U(CD₂C₆D₅)₄ showed formation of bibenzyl-d₇, indicating that reductive elimination occurs in a stepwise fashion via benzyl radical extrusion, presumably through an iminosemiquinone tris(benzyl) intermediate, (^dippisq)U(CH₂Ph)₃. Synthesis of this intermediate was attempted by addition of the iminoquinone ligand to UI₃(THF)₄ to form (^dippisq)UI₃ (3), followed by alkylation with 3 equiv of benzylpotassium. However, this only resulted in the isolation of 2. Reduction of 3 with KC₈ afforded the amidophenolate diiodide species (^dippap)UI₂(THF)₂ (4), maintaining the tetravalent oxidation state of the uranium and reducing the ligand. Attempts at the formation of 2 via addition of 2 equiv of benzylpotassium to 4 resulted in decomposition. The uranium mono(alkyl) (^dippap)UI(CH₂Ph)(THF)₂ (5) was observed upon addition of 1 equiv of benzylpotassium to 4. All products have been characterized by ¹H NMR and electronic absorption spectroscopy. X-ray crystallography was employed to ascertain ligand reduction in 2, 3, and 5.