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.