Polyisobutylene-Anchored <i>N</i>-Heterocyclic Carbene Ligands

The synthesis of polyisobutylene (PIB)-supported <i>N</i>-heterocyclic carbenes (NHCs) that are useful as ligands for recoverable/recyclable organometallic complexes is described. Both PIB-bound carbenes analogous to SIMes and IMes as well as carbene precursors bound to PIB via 1,2,3-triazoles by alkyne−azide couplings are described. Both Ag(I) and Ru(II) complexes of these carbenes are shown to be phase selectively soluble in heptane. Hoveyda−Grubbs second-generation catalysts containing a PIB-supported NHC have also been used to catalyze ring-closing metathesis.