Mono- and dinuclear palladium(ii) complexes containing both N-heterocyclic carbenes and tetrazole ligands as catalysts for Hiyama coupling†
Abstract
Treatment of the dimeric compounds [Pd(μ-Cl)(Cl)(NHC)]2 with tetrazole ligands afforded a series of tetrazole ligand stabilized NHC–Pd complexes, including [PdCl2(IPr)(1H-tetrazole)] (1), [PdCl2(SIPr)(1H-tetrazole)] (2), [PdCl2(IPr)(1-phenyl-1H-tetrazole)] (3), [PdCl2(SIPr)(1-phenyl-1H-tetrazole)] (4), [Pd2(μ-Cl)(μ-5-phenyl-2H-tetrazole)Cl2(IPr)2] (5) and [Pd2(μ-Cl)(μ-5-pheny-2H-ltetrazole)Cl2(SIPr)2] (6) [IPr = N,N′-bis-(2,6-di(isopropyl)phenyl)imidazol-2-ylidene; SIPr = N,N′-bis-(2,6-di(isopropyl)phenyl)imidazolidin-2-ylidene]. Notably, compounds 1–4 are mononuclear NHC–Pd complexes, while compounds 5 and 6 show unprecedented μ-Cl and μ-5-phenyl-2H-tetrazole bridged dinuclear structures. The catalytic properties of the obtained NHC–Pd complexes in Hiyama coupling were initially investigated.