Fig. 8. 1H NMR spectra of the reaction of 4Mes with CO in C6H6. Spectra collected on after reacting for 1 (red), 2 (yellow), 3 (green), 4 (light blue), 5 (dark blue) and 8 (purple) days. Time increases from bottom to top. Corresponding para methyl signals for 8 and 1,3-Mes2C6H4 overlap with other signals and are not shown See the ESI for full spectrum (Fig. S56)‡ and further details on how the data was collected. Inset, structures of proposed Fe–ketenyl intermediate 9 and cyclobutenone byproduct 10.
