Low hapticity intermediates in the carbonylation of (η5-2,6-dimethyl-5-hydro-s-indacenide)-Ir(η4-COD)

The isomeric (η1-5-hydro-2,6-dimethyl-s-indacenide)-Ir(η4-COD)(CO)2 and (η1-7-hydro-2,6-dimethyl-s-indacenide)-Ir(η4-COD)(CO)2) complexes are produced in a 1/1 ratio in the first step of the carbonylation reaction of (η5-2,6-dimethyl-5-hydro-s-indacenide)-Ir(η4-COD) at 233 K. At 243 K, in the presence of excess CO, they slowly convert into the isomeric (η1-5-hydro-2,6-dimethyl-s-indacenide)-Ir[η2-COD)(CO)3) and (η1-7-hydro-2,6-dimethyl-s-indacenide]-Ir(η2-COD)(CO)3. The unprecedented η2-coordination of COD towards iridium has been detected both by conventional variable temperature 1D 1H NMR spectroscopy and by a single-temperature 2D EXSY experiment.