Iridium complexes of acridine-based PNP-type pincer ligands: Synthesis, structure and reactivity

Acridine-based PNP-type pincer ligands (AcrPNP) have previously been used for the construction of a small number of Ru(II), Mn(I), Rh(III) and Ir(III) complexes, with most attention being given to the catalytically-active ruthenium complexes. In the present work, we significantly expand the scope of known AcrPNP complexes by introducing a series of new Ir(I) and Ir(III) complexes. These were synthesized from two AcrPNP ligands differing in their P-substituents (ⁱPr vs Ph), in conjunction with various Ir(I)-olefin precursors, through different sequences of reactions that include intramolecular C[sbnd]H activations and additions of H₂ and NaBEt₃H. The new iridium complexes, with their observed structures and reactivities, reflect the unique properties of the acridine-based PNP ligands, i.e., their inherent structural flexibility and ability to support both metal-centered reactivity (C[sbnd]H and H[sbnd]H oxidative addition) and ligand-centered reactivity (hydride- and H₂-induced dearomatization).