Benzimidazol-2-ylidene ligated palladacyclic complexes of N,N-dimethylbenzylamine – Synthesis and application to C–C coupling reactions

•Synthesis of bulky Pd-benzimidazol-2-ylidene complexes of N,N-dimethylbenzylamine.•Successful catalysis of Heck–Mizoroki and Suzuki–Miyaura reactions.•Steric bulk of benzimidazol-2-ylidenes influences synthetic and catalytic outcomes.

Palladacyclic complexes derived from N,N-dimethylbenzylamine (dmba) and the benzimidazol-2-ylidene ligands: 1,3-di(cyclohexyl)benzimidazol-2-ylidene (BzImCy), 1,3-di(tert-butyl)benzimidazol-2-ylidene (BzImtBu) and 1,3-di(1-adamantyl)benzimidazol-2-ylidene (BzImAd) were prepared. The yield for (BzImCy)Pd(Cl)dmba (2a) was 72% but yields for the more sterically encumbering analogues: (BzImAd)Pd(Cl)dmba (2b) and (BzImtBu)Pd(Cl)dmba (2c) were 34% and 38%, respectively. The complexes were obtained as off-white, moisture- and air-stable crystalline solids and were characterized by 1H NMR and 13C NMR spectroscopy, CHN analysis and IR spectroscopy. Complex 2c was further characterized by X-ray diffraction studies. The catalytic activity of all three complexes was explored for the Suzuki–Miyaura and Heck–Mizoroki coupling reactions of simple aryl bromides.

Graphical abstractOne-pot synthesis of bulky Pd-benzimidazol-2-ylidene complexes of N,N-dimethylbenzylamine and their application to benchmark Heck–Mizoroki and Suzuki–Miyaura reactions.Figure optionsDownload full-size imageDownload as PowerPoint slide