Rhodium(I) and iridium(I) carbonyl complexes
of nitrogen (N) and nitrogen-oxygen (N-O) donor ligands are of much interest in
recent time because of their structural novelty, reactivities and catalytic
applications. Different types of N and N-O donor ligands like pyridine, hydroxyl
pyridines, pyridine alcohols, pyridine aldehydes, pyridine carboxylic acids,
pyridine esters, benzoylpyridines, aminophenols, aminobenzoic acids etc. form a
wide variety of interesting metal complexes of rhodium and iridium. Some N-O
ligands act as bidentate chelating donors and show interesting structural
features leading to development of supramolecular structures. The steric and
electronic effects as well as kinetics of oxidative addition of the complexes
with different electrophiles like CH3I, C2H5I,
I2 etc. are interesting.
The catalytic carbonylation of alcohol exhibited by different rhodium carbonyl
complexes are efficient and show high Turn Over Number. Iridium based catalytic
carbonylation of methanol is gaining much industrial importance compared to
rhodium based catalyst because of several advantages.