Metalated Ir–CNP Complexes Containing Imidazolin‐2‐ylidene and Imidazolidin‐2‐ylidene Donors – Synthesis, Structure, Luminescence, and Metal–Ligand Cooperative Reactivity

Abstract

The iridium complex 1 based on a metalated CNP ligand containing an imidazolin‐2‐ylidene fragment has been prepared by treatment of the ligand precursor 4 with Ag2O followed by reaction with [IrCl(COE)2]2. The chlorohydride imidazolidin‐2‐ylidene complex 6, which is isostructural to 1, was synthetized by reaction of the previously reported dihydride derivative 3 with CH2Cl2. Complexes 1 and 6 exhibit luminescence arising from a 3MLCT/ILCT state involving the metalated CNP ligand, which is particularly intense for 1 in the solid state at 298 K. Furthermore, the reactivity of complexes 1 and 6 towards bases was compared. Deprotonation of 1 with KOtBu produced the selective formation of the dinuclear complex 7; meanwhile, the reaction of 6 led to a complex mixture of products. The same reactions carried out in the presence of PPh3 produced the selective deprotonation of the P‐bonded methylene bridges of 1 and 6, yielding the isostructural derivatives 9 and 10. DFT calculations performed on the uNHC‐containing tautomers I and II, and the sNHC‐based isomers III and IV, showed that the NHC‐deprotonated derivatives II and IV are more stable by 3.20 and 2.73 kcal mol–1, respectively, than their P‐deprotonated counterparts (I and III). However, a reverse stability order was observed for hexacoordinated tautomers I·L and II·L, and III·L and IV·L (L = PPh3, CO, MeCN). Finally, the catalytic activity of complex 3 in the transfer hydrogenation of ketones has been assessed.