Stegner Philipp, Färber Christian, Zenneck Ulrich, Knüpfer Christian, Eyselein Jonathan, Wiesinger Michael, Harder Sjoerd
Chair of Inorganic and Organometallic Chemistry, Universität Erlangen-Nürnberg, Egerlandstrasse 1, 91058, Erlangen, Germany.
Angew Chem Int Ed Engl. 2021 Feb 19;60(8):4252-4258. doi: 10.1002/anie.202014326. Epub 2020 Dec 21.
Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non-conjugated) mono-, di- and tri-substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba , that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba and BaH are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH ) confirm that the presence of metallic Ba has an accelerating effect.
钡金属通过蒸发以及与庚烷共缩合的方式被活化。这种黑色粉末是一种高活性氢化催化剂，可用于还原多种未活化（非共轭）的单取代、二取代和三取代烯烃、四苯乙烯、苯、多种多环芳烃、醛亚胺、酮亚胺以及各种吡啶。金属钡在氢化催化方面的性能超过了迄今最具活性的第2主族金属分子催化剂。根据底物的不同，提出了两种不同的催化循环。A：经典的金属氢化物循环；B：钡金属循环。后者适用于容易被钡还原的底物，即共轭烯烃、炔烃、稠环、亚胺和吡啶。此外，还讨论了一种钡和氢化钡都必不可少的机理。使用简单模型系统（Ba/BaH）对苯氢化进行的密度泛函理论计算证实，金属钡的存在具有加速作用。
