Acceptorless, Reversible Dehydrogenation and Hydrogenation of <i>N</i>‑Heterocycles with a Cobalt Pincer Catalyst

Abstract

Acceptorless, reversible dehydrogenation and hydrogenation reactions involving <i>N</i>-heterocycles are reported with a well-defined cobalt complex supported by an aminobis­(phosphine) [PN­(H)­P] pincer ligand. Several <i>N</i>-heterocycle substrates have been evaluated under dehydrogenation and hydrogenation conditions. The cobalt-catalyzed amine dehydrogenation step, a key step in the dehydrogenation process, has been independently verified. Control studies with related cycloalkanes suggest that a direct acceptorless alkane dehydrogenation pathway is unlikely. The metal–ligand cooperativity is probed with the related [PN­(Me)­P] derivative of the cobalt catalyst. These results suggest a bifunctional dehydrogenation pathway and a nonbifunctional hydrogenation mechanism