Rhodium(I) and iridium(I) complexes of pyrazolyl-N-heterocyclic carbene ligands

摘要

Several Rh( I) and Ir(I) complexes containing an N-heterocyclic carbene-pyrazolyl chelate ligand have been synthesised. Determination of the single-crystal X-ray structure of the Ir( I) complex showed a novel binding mode with the iridium centre coordinated to two ligands via two carbene donors in preference to one ligand forming the entropically favoured chelate. The hydrogenation activity of several of these complexes was investigated along with that of previously synthesised Rh( I) and Ir( I) complexes containing an analogous phosphine-pyrazolyl chelate.