Keywords: Charge transfer / NMR spectroscopy / Density functional calculations / Rhodium / IridiumOur recent results of the chemistry of group 9 Rh and Ir metal complexes bearing the ubiquitous pyridine, diimine (PDI) terdentate nitrogen donor are reviewed. Examples reflecting the special nature of the PDI ligand include a facile C-H activation process and the stabilization of a very rare late transition metal iridium nitrido compound, (PDI)IrϵN, and its direct hydrogenation to the corresponding amido complex according to (PDI)IrϵN + H 2 Ǟ (PDI)Ir-NH 2 . The amount of electron transfer to the PDI ligands in (PDI)Rh,Ir-R,X com-