Decarbonylation of Aliphatic Aldehydes by a TpMe2Ir(III) Metallacyclopentadiene

The Ir­(III) compound TpMe2Ir­[C­(CO2Me)C­(CO2Me)­C­(CO2Me)C­(CO2Me)]­(OH2) (1) reacts thermally with aliphatic aldehydes RC­(O)H (R = Me, tBu) to lead to the decarbonylation products TpMe2Ir­[C­(CO2Me)C­(CO2Me)­C­(CO2Me)C­(CO2Me)]­(CO) (2) and RH. In turn, formaldehyde reacts with 1, yielding a product resulting from the hydrogenation of one of the double bonds of the iridacycle. Theoretical calculations reveal the role of the metallacycle as a shuttle for the transfer of the aldehyde H atom. Under photochemical (UV) irradiation, the decarbonylation reaction becomes catalytic for a variety of aliphatic aldehydes.