Connecting Neutral and Cationic Pathways in Nickel-Catalyzed Insertion of Benzaldehyde into a C鈥揌 Bond of Acetonitrile

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• 作者：Jacob B. Smith ; Alexander J. M. Miller
• 刊名：Organometallics
• 出版年：2015
• 出版时间：October 12, 2015
• 年：2015
• 卷：34
• 期：19
• 页码：4669-4677
• 全文大小：473K
• ISSN：1520-6041

文摘

Nickel catalysts supported by diethylamine- or aza-crown ether-containing aminophosphinite (NCOP) pincer ligands catalyze the insertion of benzaldehyde into a C鈥揌 bond of acetonitrile. The catalytic activity of neutral (NCOP)Ni(O^tBu) and cationic [(NCOP)Ni(NCCHb>3b>)]⁺ are starkly different. The neutral tert-butoxide precatalysts are active without any added base and give good yields of product after 24 h, while the cationic precatalysts require a base cocatalyst and still operate much more slowly (120 h in typical runs). A series of in situ spectroscopic studies identified several intermediates, including a nickel cyanoalkoxide complex that was observed in all of the reactions regardless of the choice of precatalyst. Reaction monitoring also revealed that the neutral tert-butoxide precatalysts decompose to form the cationic acetonitrile complex during catalysis; this deactivation involves alkoxide abstraction and can be hastened by the addition of lithium salts. While the deactivated cationic species is inactive under standard base-free conditions, catalysis can be reinitiated by the addition of catalytic amounts of base.