Phosphite-containing iridium polarization transfer catalysts for NMR signal amplification by reversible exchange

Two new iridium complexes with an N-heterocyclic carbine and phosphite ligands have been synthesized and characterized. Bubbling of parahydrogen through their solutions resulted in the formation of several hydride complexes. In the presence of pyridine, this process is accompanied by transfer of spin order from the molecular hydrogen to pyridine molecules undergoing dynamic exchange between free and complex-bound states.