The iridium fragment (tBuPCP)Ir (tBuPCP = {?3-2,6-bis[(di-tert-butylphosphino)methyl]phenyl}) has been shown to catalytically transform secondary and tertiary amines into imines and enamines, respectively. There have been, however, relatively few studies focused on the generation of more oxidized nitriles from primary amines using pincer-type iridium complexes. Recent experiments in our group have shown that primary amines (R-NH2; R = benzyl, isobutyl, propyl) will undergo double transfer dehydrogenation to give the respective nitriles, using (tBuPCP)Ir and norbornene as a hydrogen acceptor. Amine substrates, imine intermediates, and nitrile products all show reversible N-coordination to (tBuPCP)Ir. In reactions with benzylamine, a thermodynamically favorable, cyclometalated intermediate species results from the oxidative addition of an aryl C-H bond to iridium, followed by coordination of the amine (or imine) nitrogen atom. Surprisingly, this species is air-stable and may aid in the development of a method for recycling (tBuPCP)Ir that has been exposed to atmospheric water and oxygen.

Exploiting dehydrogenation of primary amines by a PCP-iridium complex: Catalytic generation of several useful nitriles and discovery of an air-stable cyclometalated complex

248th National Meeting (2014)

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