Reactivity Studies of Iridium Pyridylidenes [TpMe2Ir(C6H5)2(C(CH)3C(R)NH] (R=H, Me, Ph)

The reactivity of a series of iridiumpyridylidene complexes with the formula [TpMe2Ir(C6H5)2(C(CH)3C(R)NH] (1a1c) towards a variety of substrates, from small molecules, such as H2, O2, carbon oxides, and formaldehyde, to alkenes and alkynes, is described. Most of the observed reactivity is best explained by invoking 16e unsaturated [TpMe2Ir(phenyl)(pyridyl)] intermediates, which behave as internal frustrated Lewis pairs (FLPs). H2 is heterolytically split to give hydridepyridylidene complexes, whilst CO, CO2, and H2CO provide carbonyl, carbonate, and alkoxide species, respectively. Ethylene and propene form five-membered metallacycles with an IrCH2CH(R)N (R=H, Me) motif, whereas, in contrast, acetylene affords four-membered iridacycles with the IrC(CH2)N moiety. C6H5(CO)H and C6H5CCH react with formation of IrC6H5 and IrCCPh bonds and the concomitant elimination of a molecule of pyridine and benzene, respectively. Finally the reactivity of compounds 1a1c against O2 is described. Density functional theory calculations that provide theoretical support for these experimental observations are also reported.