Reactivity of octahedral η1-allenyl iridium toward hard nucleophiles

Article abstract of DOI:10.1021/om960261a

A labile octahedral (η¹-allenyl)iridium complex, (OC-6-42)-Ir(Cl)(PPh₃)₂(OTf)(CO)(η ¹-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-CH ₂C(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-CH ₂C(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)[η ¹-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-CH ₂C(NR₂)CH₂]}(OTf) (R = H (7a), Et (Tb)).