Selective Hydrogenation of Amides to Amines and Alcohols Catalyzed by Improved Iron Pincer Complexes
Selective Hydrogenation of Amides to Amines and Alcohols Catalyzed by Improved Iron Pincer Complexes
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DOI：
10.1021/acs.organomet.6b00251
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发表时间：
2016-05
期刊：
影响因子：
2.8
通讯作者：
F. Schneck;Maik Assmann;Markus Balmer;K. Harms;R. Langer
中科院分区：
文献类型：
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作者：
F. Schneck;Maik Assmann;Markus Balmer;K. Harms;R. Langer
报道了通式[(R-PNHP)Fe(H)(CO)(BH4)]的各种铁钳配合物的合成、稳定性和催化活性的比较研究，其中R表示末端PR2基团的取代基(R = tBu、Cy、iPr、Ph、Et)。通过合成预催化剂的例子，表明配体的性质对配合物的催化性能具有令人惊讶的影响。大配体和较少给电子配体影响配合物的稳定性，其优选在失去CO或H 2 的情况下反应生成失活产物。作为回报，与之前报道的 iPr 取代络合物相比，Et 取代预催化剂 (2a) 的空间需求减少和强大的 σ 供体特性导致酯氢化成醇的活性提高。在温和条件下将酰胺直接氢化为醇和胺，清楚地证明了络合物 2a 的活性得到了改善。
A comparative study on the synthesis, stability, and catalytic activity of various iron pincer complexes with the general formula [(R-PNHP)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.