Selective Hydrogenation of Amides to Amines and Alcohols Catalyzed by Improved Iron Pincer Complexes

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• 作者：Felix Schneck ; Maik Assmann ; Markus Balmer ; Klaus Harms ; Robert Langer
• 刊名：Organometallics
• 出版年：2016
• 出版时间：June 13, 2016
• 年：2016
• 卷：35
• 期：11
• 页码：1931-1943
• 全文大小：694K
• 年卷期：0
• ISSN：1520-6041

文摘

A comparative study on the synthesis, stability, and catalytic activity of various iron pincer complexes with the general formula [(R-PN^HP)Fe(H) (CO) (BH₄)] is reported, where R denotes the substituent of the terminal PR₂-groups (R = ^tBu, Cy, ⁱPr, Ph, Et). By the example of the synthesized precatalysts, it is shown that the nature of the ligands has a surprising influence on the catalytic properties of the complexes. Bulky ligands and less electron donating ligands affect the stability of the complexes, which preferably react under the loss of CO or H₂ to deactivated products. In return, the reduced steric demand and the strong σ-donating properties of the Et-substituted precatalyst (2a) lead to an improved activity in the hydrogenation of esters to alcohols, compared to that of the previously reported ⁱPr-substituted complexes. The improved activity of complex 2a is clearly demonstrated in the direct hydrogenation of amides to alcohols and amines under mild conditions.