Air stable pincer (CNC) N-heterocyclic carbene–cobalt complexes and their application as catalysts for C–N coupling reactions

摘要: Abstract Two new pincer (CNC) N-heterocyclic carbene (NHC)–Co complexes: 3,3′-(dimethylimidazolin-2-ylidene)lutidine chlorocobalt(II) hexafluorophosphate, 3a and 3,3′-(dibenzylimidazolin-2-ylidine)lutidine 3b were synthesised in good yields via transmetalation of the corresponding Ag–NHC complexes. Spectroscopic analyses (1H, 13C, 31P, FT-IR) analytical techniques (melting point, MS-ES+) used to characterize showed distinct paramagnetic properties as observed from its 1H NMR data. Magnetic measurements that it has a susceptibility 4.12 μB, consistent with three un-paired electrons for high spin Co(II) specie. Both complexes excellent activity catalysing C–N coupling aryl halides primary amines yield desired secondary isolated yields. The catalysts selective monoarylated 2° amine products suppression 3° biphenyls. A mechanism is proposed action NHC–Co this reaction.