Methoxy-Functionalized N-Heterocyclic Carbenes

The effect of methoxy functionalization of three N-heterocyclic carbene ligands was assessed using a variety of methods. The steric environment of each carbene has been assessed in various coordination environments. The electronic properties, specifically the electron-donating character and pi-accepting ability, have been evaluated using nickel and iridium complexes and selenium adducts, respectively. Comparisons with the parent systems have been made with respect to both electronic and steric properties. The carbenes IPrOMe, SIPrOMe, and IPr*(Ome) have been found to be more electron donating than the parent systems IPr, SIPr, and IPr* and only slightly less pi accepting, yet they exhibit similar steric properties.