Cyclometalated Iridium(III) Complexes with Ligand Effects on the Catalytic C–H Bond Activation of Toluene

Abstract

New cyclometalated iridium(III) complexes have been designed, prepared and applied as catalytic systems for the C-H bond activation (CHA) of toluene through a clean, highly efficient, and environmentally friendly process. The complexes have the general formula [(C^N) 2 Ir(N^O)]. The C^N ligands are the monoanionic bidentate cyclometalating ligands 2-phenylpyridinato (ppy), 2-phenylbenzoxazolato (pbo), and 2-(3.5-difluorophenyl)benzoxazolato (dfpbo). The (N^O) ligand is also a monoanionic bidentate cyclometalating ligand, namely picolinato (pic). The complexes [(ppy) 2 Ir(pic)] (1), [(pbo) 2 Ir(pic)] (2), and [(dfpbo) 2 -Ir(pic)] (3) were structurally characterized by 1 H and 13 C NMR spectroscopy, FAB-MS, and X-ray crystallography. The activation [a] 2023 Scheme 1. Synthetic route to the C^N ligands and complexes 1-3.

Neutral 2-phenylbenzimidazole-based iridium(iii) complexes with picolinate ancillary ligand: tuning the emission properties by manipulating the substituent on the benzimidazole ring

“…The bite angles of both cyclometallating ligand and ancillary ligand are similar through the series and comparable with that of [Ir(ppy) 2 pic]; the bite angles of ppy ligand and 2-phenylbenzimidazole are around 80°. 60 The C–Ir–C′ angles are about 90.5° for the three complexes, of the same order as the one encountered in [Ir(ppy) 2 pic] (88.7°). Brought together, the different parameters are coherent with the expected octahedral coordination geometry, with slight distortions of the ligands caused by the formation of the five-membered metallacycles.…”

“…Crystallographic quality single crystals of IrL 6 2 , IrL 9 2 and IrL 10 2 have been obtained by slow vapor diffusion of diethyl ether or pentane in a concentrated solution of each complex in dichloromethane. The cell parameters of each complex are summarized in Table S1† and selected bond lengths and angles of the three complexes are presented in Table 1, along with those of complex [Ir(ppy) 2 pic] 60 for comparison purpose. The crystallization space groups and Bravais lattices are monoclinic P 2 1 / m for IrL 6 2 and IrL 9 2 , and triclinic P 1̄ for IrL 10 2 .…”

Cyclometalated Iridium(III) Complexes Containing Benzoxazole Derivatives and Different Ancillary Ligands for Catalytic Oxidation of Toluene

“…Previously, we have reported some cyclometalated iridium(III) complexes composed of benzoxazole ligand that can spontaneously release metalloradicals to promote two types of reactions: the carbon-hydrogen bond activation (CHA) and carbon-carbon bond activation (CCA) for ketones and aldehydes [5]. We have also demonstrated that the cyclometalated iridium(III) complexes could directly transform toluene into benzaldehyde [6].…”