Two ruthenium-based pre-catalysts containing an ionic tag covalently connected to a N-heterocyclic carbene (NHC) ligand are reported. These novel complexes, bearing a polar benzimidazolium group, are air-stable and can be easily prepared from commercially available reagents. The quaternary benzimidazolium tag allows the efficient separation of ruthenium waste from the metathesis product after reaction. Application in several olefin metathesis transformations leads to desired products of high purity, which exhibit ruthenium contamination levels as low as 1 ppm after simple filtration through a pad of silica gel.
本研究报道了两种基于
钌的前催化剂,它们含有与 N-杂环碳烯(NHC)
配体共价连接的离子标记。这些带有极性
苯并咪唑基团的新型配合物在空气中十分稳定,而且很容易用市售试剂制备。四元
苯并咪唑标签可以在反应后有效地将
钌废料从偏析产物中分离出来。在几种烯烃复分解反应中的应用可得到高纯度的理想产物,通过
硅胶垫进行简单过滤后,
钌污染
水平可低至 1 ppm。