Air stable NHCs: a study of stereoelectronics and metallorganic catalytic activity

Abstract

The air stable NHC IPrBr is reported. A stereoelectronic study of IPrBr and its similarly stable relative IMesBr demonstrates metal complex specific changes in NHC donicity versus the ubiquitous IPr and IMes. Application to a Suzuki coupling and an iridium transfer hydrogenation gives superior outcomes using IPrBr and IMesBr.

The Golden Age of Transfer Hydrogenation

“…511 Colacino et al 512 reported iridium−NHC conplexes bearing 3,4,5-trimethoxybenzyl Nsubstituents, taking 144a and 144b as examples (Scheme 54).…”

Insights into the Catalytic Activity of [Pd(NHC)(cin)Cl] (NHC=IPr, IPrCl, IPrBr) Complexes in the Suzuki–Miyaura Reaction

“…As reported by Cole and co‐workers, [Pd(IPr Br )(cin)Cl] ( 9 c ) can be prepared in good yield by using the free carbene route . We also prepared [Pd(IPr Cl )(cin)Cl] ( 9 b ) from free IPr Cl .…”

“…KO t Bu) . Their corresponding salts were obtained in quantitative yields as previously reported ,. Under inert atmosphere, IPr was reacted with either CCl 4 or CBr 4 for three hours to generate the C 4,5 ‐haloganed carbene and one equivalent of haloform (CHX 3 , X=Cl or Br) .…”

“…The IPr Cl ligand analogue was involved in alkene metathesis transformations by Nolan and co‐workers, whereas IPent Cl ( 6 ) was used by Organ and co‐workers in Stille cross‐coupling and Pd‐catalyzed amination . More recently, Cole and co‐workers have reported on a series of metal complexes bearing IPr Br ( 8 ) along with [Pd(IPr Br )(cin)Cl] (Figure , 9 c ) which was briefly studied in the Suzuki–Miyaura cross‐coupling …”

Addition Homo‐ and Copolymerizations of Dicyclopentadiene and 5‐n‐Hexylnorbornene in the Presence of Pd‐N‐Heterocyclic Carbene Complexes

“…. Pd‐complexes (SIMesPd(cinn)Cl, SIPrPd(cinn)Cl and 6MesPd(cinn)Cl, IMesPd(cinn)Cl, IPrPd(cinn)Cl) were prepared according to the literature procedures.…”