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

Iridium PNP amido complex [Ir(PMe3){N(CH2CH2PiPr2)2}] (3PMe3) was prepared in high yield starting from ethylene amine complex [Ir(C2H4){HN(CH2CH2PiPr2)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(CH2CH2PiPr2)2}] (3L; L = PMe3, cyclooctene, CO) is quantified by determination of the corresponding amine complex pKa values. Examination of chemical and electrochemical oxidation of 3L 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 π-interactions.

Graphical abstractThe influence of auxiliary ligands on the basicity and redox properties of iridium(I) amido complexes [Ir(L){N(CH2CH2PiPr2)2}] (L = CO, cyclooctene, PMe3) was probed by pK measurements and cyclic voltammetry. The strong dependence of these properties on the nature of L is rationalized on the basis of 3c-4e N–M–L π-interactions.Figure optionsDownload full-size imageDownload as PowerPoint slide