Publication
Room-temperature stable diazoolefins provide access to a unique class of carbon-donor ligands: N-heterocyclic vinylidenes. Herein, we describe iridium complexes with terminal N-heterocyclic vinylidene ligands. Cationic complexes of type [CpIrClL]X (X = SbF6, OTf; L = N-heterocyclic vinylidene) were obtained by reaction of (CpIrCl2)2 with an N-heterocyclic diazoolefin, followed by chloride abstraction. Reduction instead of chloride abstraction gave a neutral Cp*IrL complex with a “pogo stick” geometry. Crystallographic analyses of the complexes revealed very short iridium–carbon bonds, suggesting partial carbyne character. The vinylidene ligands display ambiphilic reactivity. The cationic complex forms covalent adducts with halides and pseudohalides, whereas the neutral complex reacts with electrophiles. These transformations generate rare carbon-donor species, including anionic N-heterocyclic olefins with pronounced carbene character or a side-on bound alkylidene ketene