Rhodium and Iridium Complexes of N-Heterocyclic Carbenes via Transmetalation: Structure and Dynamics

Rhodium and iridium complexes of N-heterocyclic carbenes (3a−c and 4a−c) were obtained
by transmetalation from the corresponding Ag(I) complexes. The structure of 3b was verified
by X-ray diffraction. The compounds display restricted rotation about the metal−carbene
bond, the rate of which can be controlled by altering the steric bulk of the auxiliary ligands.
Infrared spectroscopy provides an estimate of the electron-donor power of the carbene ligands
from ν(CO) of the carbonyl derivatives.