H/D exchange under mild conditions in arenes and unactivated alkanes with CD and DO using rigid, electron-rich iridium PCP pincer complexes.

The synthesis and characterization of an iridium polyhydride complex () supported by an electron-rich PCP framework is described. This complex readily loses molecular hydrogen allowing for rapid room temperature hydrogen isotope exchange (HIE) at the hydridic positions and the α-C-H site of the ligand with deuterated solvents such as benzene-d, toluene-d and THF-d. The removal of 1-2 equivalents of molecular H forms unsaturated iridium carbene trihydride () or monohydride () compounds that are able to create further unsaturation by reversibly transferring a hydride to the ligand carbene carbon. These species are highly active hydrogen isotope exchange (HIE) catalysts using CD or DO as deuterium sources for the deuteration of a variety of substrates. By modifying conditions to influence the speciation, deuteration levels can range from near exhaustive to selective only for sterically accessible sites. Preparative level deuterations of select substrates were performed allowing for procurement of >95% deuterated compounds in excellent isolated yields; the catalyst can be regenerated by treatment of residues with H and is still active for further reactions.