Palladacycle from Cyclometalation of the Unsubstituted Cyclopentadienyl Ring in Ferrocene: Synthesis, Characterization, Theoretical Studies, and Application to Suzuki鈥揗iyaura Reaction

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• 作者：Hengyu Qian ; Zhigang Yin ; Tongyan Zhang ; Shihai Yan ; Quanling Wang ; Chunxia Zhang
• 刊名：Organometallics
• 出版年：2014
• 出版时间：November 10, 2014
• 年：2014
• 卷：33
• 期：21
• 页码：6241-6246
• 全文大小：316K
• ISSN：1520-6041

文摘

The ferrocenylimines of general formula [(畏⁵-C₅H₅)Fe(畏⁵-C₅H₄)-CH₂N鈺怌H-C(R)鈺怌H-C₆H₅] with R = H (2a) and CH₃ (2b) were conveniently prepared from ferrocenylmethylamine. Reaction of 2a,b with lithium tetrachloropalladate in methanol in the presence of anhydrous sodium acetate resulted in the formation of the di-渭-chloro-bridged heteroannular cyclopalladated complexes 3a,b via the unsubstituted ferrocenyl C鈥揌 bond activation of the related ligands. Treatment of 3a,b with triphenylphosphine gave Pd{[(畏⁵-C₅H₄)Fe(畏⁵-C₅H₄)CH₂N鈺怌H-CH鈺怌H-C₆H₅]}ClPPh₃ (4a) and Pd{[(畏⁵-C₅H₄)Fe(畏⁵-C₅H₄)-CH₂N鈺怌H-C(CH₃)鈺怌H-C₆H₅]}ClPPh₃ (4b), respectively. The crystal structures of 4a,b confirmed the formation of a carbon鈥損alladium bond by using a carbon atom in the unsubstituted cyclopentadienyl ring. Additionally, theoretical studies using density functional theory calculations were carried out in order to account for the regioselectivity of cyclometalation. As for the catalysts, using 0.1% of palladacycles 4a,b in the presence of K₃PO₄路7H₂O as base exhibited excellent yields in the Suzuki鈥揗iyaura coupling reaction of aryl bromides with phenylboronic acid.