Iridium(III)–pyridone complexes are commonly found to react in a cooperative and redox-neutral manner with dihydrogen and alcohols. In this work, the reactivity preferences of IrI–pyridone complexes were investigated under a variety of conditions. We have found that, in contrast to IrIII–pyridones, IrI–pyridone complexes display a strong preference to react non-cooperatively. With a new chelating 2-hydroxy-8-diphenylphosphinoquinoline ligand that does not dissociate after hydrogen addition, oxidative addition is still preferred. In the preparation of mono- and bidentate neutral and anionic pyridone ligands, Vaska's complex was used as a point of reference. We expect these findings to have implications for catalyst development in the field of metal–ligand cooperation.
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