Low hapticity intermediates in the carbonylation of (eta(5)-2,6-dimethyl-5-hydro-s-indacenide)-Ir(eta(4)-COD)

The isomeric (eta(1)-5-hydro-2,6-dimethyl-s-indacenide)-Ir(eta(4)-COD)(CO)( 2) and (eta(1)-7-hydro-2,6-dimethyl-s-indacenide)-Ir(eta(4)-COD)(CO)(2)) co mplexes are produced in a ii I ratio in the first step of the carbonylation reaction of (eta(5)-2,6-dimethyl-5-hydro-s-indacenide)-Ir(eta(4)-COD) at 2 33 K. At 243 K, in the presence of excess CO, they slowly convert into the isomeric (eta(1)-5-hydro-2,6-dimethyl-s-indacenide)-Ir[eta(2)-COD)(CO)(3)) and (eta(1)-7-hydro-2,6-dimethyl-s-indacenide]-Ir(eta(2)-COD)(CO)(3). The u nprecedented eta(2)-coordination of COD towards iridium has been detected b oth by conventional variable temperature 1D H-1 NMR spectroscopy and by a s ingle-temperature 2D EXSY experiment. (C) 2000 Elsevier Science S.A. All ri ghts reserved.