Metal‐Ligand Cooperativity in a Methandiide‐Derived Iridium Carbene Complex

The synthesis, electronic structure, and reactivity of the first Group 9 carbene complex, [Cp*IrL] [L=C(Ph 2 PS)(SO 2 Ph)] ( 2 ), based on a dilithio methandiide are reported. Spectroscopic as well as computational studies have shown that, despite using a late transition‐metal precursor, sufficient charge transfer occurred from the methandiide to the metal, resulting in a stable, nucleophilic carbene species with pronounced metal‐carbon double‐bond character. The potential of this iridium complex in the activation of a series of E−H bonds by means of metal‐ligand cooperation has been tested. These studies have revealed distinct differences in the reactivity of 2 compared to a previously reported ruthenium analogue. Whereas attempts to activate the O−H bond in different phenol derivatives resulted in ligand cleavage, H−H and Si−H activation as well as dehydrogenation of isopropanol have been accomplished. These reactions are driven by the transformation of the carbene to an alkyl ligand. Contrary to a previously reported ruthenium carbene system, the dihydrogen activation has been found to proceed by a stepwise mechanism, with the activation first taking place solely at the metal. The activated products further reacted to afford a cyclometalated complex through liberation of the activated substrates. In the case of triphenylsilane, cyclometalation could thus be induced by a substoichiometric (i.e., catalytic) amount of silane.