Synthesis, Structures, and Electronic Properties of O- and S‑Heterocyclic Carbene Complexes of Iridium, Copper, Silver, and Gold

O- and S-heterocyclic carbenes (OHCs, SHCs) are shown experimentally and computationally to be stronger π acceptors than NHCs and lack, of course, substituents at the heteroatoms. These different electronic and steric characteristics make OHCs and SHCs interesting ligands for coordination chemistry. Convenient synthetic routes are presented to access their iridium­(I), iridium­(III), and coinage-metal­(I) (Cu, Ag, Au) complexes in good yields by means of dissociation of olefins, deprotonation of precursor salts, and transmetalation from a silver carbene complex. Molecular structures and detailed bonding analyses of these complexes are presented.