Ketone Hydrogenation with Iridium Complexes with 鈥渘on N鈥揌鈥?Ligands: The Key Role of the Strong Base

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• 作者：Joseph M. Hayes ; Eric Deydier ; Gregori Ujaque ; Agust铆 Lled贸s ; Raluca Malacea-Kabbara ; Eric Manoury ; Sandrine Vincendeau ; Rinaldo Poli
• 刊名：ACS Catalysis
• 出版年：2015
• 出版时间：July 2, 2015
• 年：2015
• 卷：5
• 期：7
• 页码：4368-4376
• 全文大小：437K
• ISSN：2155-5435

文摘

Ferrocenyl phosphine thioether ligands (PS), not containing deprotonatable functions, efficiently support the iridium catalyzed ketone hydrogenation in combination with a strong base cocatalyst. Use of an internal base ([Ir(OMe)(COD)]₂ in place of [IrCl(COD)]₂) is not sufficient to ensure activity and a strong base is still necessary, suggesting that the active catalyst is an anionic hydride complex. Computational investigations that include solvent effects demonstrate the thermodynamically accessible generation of the tetrahydrido complex [IrH₄(PS)]^{鈭?/sup> and suggest an operating cycle via a [Na+(MeOH)₃路路路Ir鈥?/sup>H₄(PS)] contact ion pair with an energy span of 18.2 kcal/mol. The cycle involves an outer sphere stepwise H鈥?/sup>/H+ transfer, the proton originating from H₂ after coordination and heterolytic activation. The base plays the dual role of generating the anionic complex and providing the Lewis acid cocatalyst for ketone activation. The best cycle for the neutral system, on the other hand, requires an energy span of 26.3 kcal/mol. This work highlights, for the first time, the possibility of outer sphere hydrogenation in the presence of non deprotonatable ligands and the role of the strong base in the activation of catalytic systems with such type of ligands.}