In Situ Generation Of Catalytically Relevant Nanoparticles From A Molecular Pincer Iridium Precatalyst During Polyol Deoxygenation

Pincer complexes such as ((POCOP)-P-R)Ir-based species ((POCOP)-P-R = kappa(3)-C6H3-1,3-[P(R)(2)](2)) are widely used as precatalysts for organic transformations with many mechanistic studies of these transformations based on the assumption that the precatalysts retain their molecular nature under catalytic conditions. We demonstrate that even ((POCOP)-P-tBu)IrCO ((POCOP)-P-tBu = kappa(3)-C6H3-1,3-[P(R)(2)](2)), a precatalyst valued for its stability, can be susceptible to the formation of nanoparticles at elevated temperatures under the acidic reducing conditions required for polyol deoxygenation and that the nanoparticles formed in situ can HO, contribute to the observed hydrogenation activity. The iridium nanoparticles isolated from reaction mixtures by centrifugation and detected on glass and polytetrafluoroethylene (PTFE) reactor liners exhibit a high degree of aggregation and resist common cleaning protocols.