CCC–N-heterocyclic carbene pincer complexes: Synthesis, characterization and hydroamination activity of a hafnium complex

Our methodology for the stoichiometric preparation of CCC–NHC pincer complexes of Zr has been extended to Hf. The CCCBu–NHC pincer Hf complex has been characterized by X-ray crystal structure analysis. Catalytic activity in the intramolecular hydroamination/cyclization of unactivated alkenes is reported and compared to the recently reported Zr analog. An improved, scaled-up CuO-catalyzed aryl amination of 1,3-dibromobenzene and an improved salt formation methodology for preparation of bis(butyl-imidazolium)benzene are reported also.

Graphical abstractOur methodology for the stoichiometric preparation of CCC–NHC pincer complexes of Zr has been extended to Hf. Catalytic activity in the intramolecular hydroamination/cyclization of unactivated alkenes is reported and compared to the recently reported Zr analog.Figure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights► Large scale synthesis of the bis(imidazolium) salt CCCBu–NHC ligand precursor. ► Highly efficient synthesis of Hf CCC–NHC pincer complex with structural characterization. ► Catalytically active for hydroamination/cyclization yielding pyrrolidines and piperidines.