Reactivity of iridium(I) PNP amido complexes toward protonation and oxidation

Iridium PNP amido complex [Ir(PMe3){N((CH2CH2PPr2)-Pr-i)(2)}] (3(PMe3)) was prepared in high yield starting from ethylene amine complex [Ir(C2H4){HN((CH2CH2PPr2)-Pr-i)(2)}]PF6. The high nucleophilicity of the amido nitrogen atom is demonstrated by facile N-methylation with MeOTf. The N-basicity within the series [IrL {N((CH2CH2PPr2)-Pr-i)(2)}] (3(L); L = PMe3, cyclooctene, CO) is quantified by determination of the corresponding amine complex pK(a) values. Examination of chemical and electrochemical oxidation of 3(L) point toward decomposition of the primary oxidation product by ligand centered disproportionation. The strong dependence of the basicity and oxidation potentials on the nature of L is rationalized on the basis of 3c-4e N-M-L pi-interactions. (C) 2013 Elsevier B.V. All rights reserved.