What question did this study set out to answer?

This research focuses on understanding how unactivated terminal alkenes insert into Ir–N bonds in specific complexes.

March 30, 2026

Direct Observation of Selective Migratory Insertion of Unactivated Terminal Alkenes into Ir–N Bonds

Key Points

This research focuses on understanding how unactivated terminal alkenes insert into Ir–N bonds in specific complexes.
Synthesis and characterization of cationic bisphosphine-ligated hydridoiridium amides
Observation of alkene insertion at low temperatures (-80 °C)
NMR spectroscopy for characterization of resulting hydridoiridium alkyl complexes
DFT calculations to analyze the mechanism of insertion
Alkenes insert into the Ir–N bond faster than into the Ir–H bond
High enantiomeric excess of amine products observed
Reversible migratory insertion of alkenes noted for electron-rich 2-aminopyridines
Chelation by the 2-pyridylamido ligand is suggested to facilitate insertion

Abstract

We report fast insertions of alkenes into the metal-nitrogen bonds of cationic bisphosphine-ligated hydridoiridium amides that are potential intermediates in previously reported enantioselective hydroaminations of unactivated alkenes with 2-aminopyridines. The amido complexes were synthesized and structurally characterized, shown to undergo insertion at temperatures as low as -80 °C, and shown to insert alkene into the metal-amide bond more rapidly than into the metal-hydride bond. The hydridoiridium alkyl complexes resulting from this insertion were unambiguously characterized by NMR spectroscopy (1H, 13C, 31P, 15N) and shown to form the amine, with high enantiomeric excess matching that of the catalytic process, by reductive elimination at 25 °C. Reversible migratory insertion of terminal alkenes into the Ir-N bond was observed for amides derived from electron-rich 2-aminopyridines. The arrangement of ligands at iridium in the hydridoiridium(III) amides and precursor iridium(I) amides was elucidated by preparing 15N-enriched derivatives and was corroborated by matching experimental and computational coupling constants. DFT calculations suggest that chelation by the 2-pyridylamido ligand to iridium facilitates insertion of alkenes into the Ir-N bond and that the coordination geometry precludes insertion into the Ir-H bond. These studies clarify the origins of the favorable insertion of unactivated alkenes into the Ir-N bonds over the Ir-H bonds and show that late-transition-metal-amido complexes, even of third-row d6 metal centers, can insert alkenes with exceptionally high rates.

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