The development and use of novel iridium complexes as catalysts for ortho-directed hydrogen isotope exchange reactions

The preparation and application of groups of new iridium complexes are described. In particular, iridium complexes possessing phosphine ligands and a bulky N-heterocyclic carbene have been shown to be robust and readily handled species and have been applied in a range of directed hydrogen-deuterium and -tritium exchange processes and, in particular, with drug-like substrates or within ADMET-related studies. Overall, these new iridium(I) complexes are shown to be highly active catalysts and display catalytic activity far in excess of the industry standard, Crabtree's catalyst, with excellent levels of labelling being achieved over short reaction times and at low metal complex loadings, whilst tolerating a wide range of functional moieties. Furthermore and again in contrast to systems employing Crabtree's catalyst, the low catalyst loadings and short reaction times made possible by these emerging iridium carbene comple have delivered tritiated products with very good levels of labelling and without any appreciable by-product waste production.