Premium
Iridium(III) Complexes Bearing Chelating Bis‐NHC Ligands and Their Application in the Catalytic Reduction of Imines
Author(s) -
Aznarez Francisco,
Iglesias Manuel,
Hepp Alexander,
Veit Benjamin,
Sanz Miguel Pablo J.,
Oro Luis A.,
Jin GuoXin,
Hahn F. Ekkehardt
Publication year - 2016
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201600922
Subject(s) - chemistry , carbene , deprotonation , imidazole , iridium , moiety , chelation , catalysis , medicinal chemistry , ligand (biochemistry) , transfer hydrogenation , stereochemistry , polymer chemistry , organic chemistry , ruthenium , ion , biochemistry , receptor
The Ir III complexes 4 and 5 bearing bis‐NHC ligands (NHC = N‐heterocyclic carbene) composed of one classical NR,NR NHC and one N,NR NHC donor were prepared by the reaction of the azolium/azole compounds 2 I and 3 Br, respectively, with [{Cp*IrCl(µ‐Cl)} 2 ] (Cp*=η 5 ‐C 5 Me 5 ) in the presence of NaOAc as base. Most likely, the salts 2 I and 3 Br were first selectively deprotonated at the C2 position of the disubstituted (NR,NR) diazaheterocycle to generate an NHC donor, which then coordinated to the Ir III center. Subsequently, NaOAc promoted C–H bond activation at the pendant imidazole moiety of the intermediate Ir III mono‐NHC complexes led to the formation of the six‐membered iridacycles 4 and 5 , which bear a chelating, doubly C ‐metalated C(NHC) ^ C(NHC′) bis‐NHC ligand. The Ir III complexes 4 and 5 were tested as precatalysts for the reduction of imines with molecular hydrogen. Moderate to good activity was observed at a catalyst loading of 5 mol‐% and an H 2 pressure of 3 bar in MeOH.