Mono-Oxidation of Bidentate Bis-phosphines in Catalyst Activation: Kinetic and Mechanistic Studies of a Pd/Xantphos-Catalyzed C鈥揌 Functionalization

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• 作者：Yining Ji ; R. Erik Plata ; Christopher S. Regens ; Michael Hay ; Michael Schmidt ; Thomas Razler ; Yuping Qiu ; Peng Geng ; Yi Hsiao ; Thorsten Rosner ; Martin D. Eastgate ; Donna G. Blackmond
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：October 21, 2015
• 年：2015
• 卷：137
• 期：41
• 页码：13272-13281
• 全文大小：780K
• ISSN：1520-5126

文摘

Kinetic, spectroscopic, crystallographic, and computational studies probing a Pd-catalyzed C鈥揌 arylation reaction reveal that mono-oxidation of the bis-phosphine ligand is critical for the formation of the active catalyst. The bis-phosphine mono-oxide is shown to be a hemilabile, bidentate ligand for palladium. Isolation of the oxidative addition adduct, with structural elucidation by X-ray analysis, showed that the mono-oxide was catalytically competent, giving the same reaction rate in the productive reaction as the Pd(II)/xantphos precursor. A dual role for the carboxylate base in both catalyst activation and reaction turnover was demonstrated, along with the inhibiting effect of excess phosphine ligand. The generality of the role of phosphine mono-oxide complexes in Pd-catalyzed coupling processes is discussed.