Reactivity of Octahedral η1-Allenyl Iridium toward Hard Nucleophiles

Abstract

A labile octahedral (η1-allenyl)iridium complex, (OC-6-42)-Ir(Cl)(PPh3)2(OTf)(CO)(η1-CHCCH2) (2a), undergoes regioselective addition with water or alcohol at the allenyl central carbon to generate the (η3-2-hydroxyallyl) and (η3-2-alkoxyallyl)iridium complexes {Ir(Cl)-(PPh3)2(CO)[η3-CH2C(OR)CH2]}(OTf) (R = H (3), Me (4a), Et (4b)), respectively. The complex 3 and the η3-oxa-TMM species Ir(Cl)(PPh3)2(CO)[η3-CH2C(O)CH2] (5) constitutes a conjugate acid−base pair. Hydrolysis of the η3-alkoxyallyl complexes yields 3, which further transforms into the carbon-bound iridium enolate (OC-6-52)-{Ir(Cl)(PPh3)2(OH2)(CO)[η1-CH2C(O)CH3]}(OTf) (6). The reaction of 2a with ammonia results in the substitution of NH3 for the triflate ligand instead of hydroamination to the allenyl ligand. The construction of the C−N bond, however, is alternatively achieved by replacing the alkoxy group in 4a or 4b with the amino group, leading to the formation of the N-protonated and N-alkylated η3-aza-TMM iridium {Ir(Cl)(PPh3)2(CO)[η3-CH2...