Benzo annulated cycloheptatriene PCP pincer iridium complexes†
The benzo annulated cycloheptatriene PCP pincer ligand 5 was prepared in five steps. Treatment of 5 with Ir(CO)3Cl gave the meridional cyclometalated chlorohydrido carbonyl iridium complexes 6a–c which differ in their arrangement of the H, Cl, and CO ligands around iridium. Storing 6 in THF led to isomerization processes. Hydrogen shifts from the sp3-CH carbon bound to iridium into the ligand backbone produced the three isomers 7a–c. Reductive elimination of HCl from these complexes resulted in the square planar Ir(I) carbonyl complexes 8a–c. Abstraction of the hydrogen from the sp3-CH–Ir fragment could be achieved either by treatment of 6 with Ph3CBF4 or by the elimination of H2 which is initiated by CF3SO3H. The mass spectrometric characterisation of 6 using fast atom bombardment reveals a complex fragmentation pattern. These different “fragment” ions were further investigated by electro-spray ionisation (tandem) mass spectrometry in high and low resolution. The identified compounds were attributed to structures by DFT calculations.
- This article is part of the themed collection: The Carbon–Metal Bond and C–H Metalation