Syntheses and structural studies of η5-pentamethylcyclopentadienyl rhodium(III) and iridium(III) complexes of a Schiff-base expanded porphyrin

Reported here is the synthesis of new binuclear rhodium(III) and iridium(III) semisandwich complexes of a Schiff-base expanded porphyrin. Single crystals of these new complexes were subject to X-ray diffraction analysis. The resulting structures revealed that the Schiff-base macrocycle adopts a V-shape in which two {(eta(5)-C5Me5)MCl} (M = Rh and Ir) fragments are accommodated within the macrocyclic pocket. The coordination environment of the metal centers is typical to that of "piano stool"-type complexes. The X-ray analyses and complementary NMR studies (carried out in CD2Cl2) provide evidence for the existence of strong intramolecular hydrogen-bonding interactions between the pyrrolic NH protons and the chloride counteranion both in solution and in the solid state.