C–H, N–H, and O–H Bond Activations to Prepare Phosphorescent Hydride-Iridium(III)-Phosphine Emitters with Photocatalytic Achievement in C–C Coupling Reactions

Complex IrH5(PiPr3)2 (1) activates two different σ-bonds of
3-phenoxy-1-phenylisoquinoline,
2-(1H-benzimidazol-2-yl)-6-phenylpyridine, 2-(1H-indol-2-yl)-6-phenylpyridine, 2-(2-hydroxyphenyl)-6-phenylpyridine, N-(2-hydroxyphenyl)-N′-phenylimidazolylidene,
and 1,3-di­(2-pyridyl)-4,6-dimethylbenzene to give IrH­{κ3-C,N,C-[C6H4-isoqui-O-C6H4]}­(PiPr3)2 (2), IrH­{κ3-N,N,C-[NBzim-py-C6H4]}­(PiPr3)2 (3), IrH­{κ3-N,N,C-[Ind-py-C6H4]}­(PiPr3)2 (4), IrH­{κ3-C,N,O-[C6H4-py-C6H4O]}­(PiPr3)2 (5), IrH­{κ3-C,C,O-[C6H4-Im-C6H4O]}­(PiPr3)2 (6), and IrH­{κ3-N,C,C-[py-C6HMe2-C5H3N]}­(PiPr3)2 (7), respectively. The activations
are sequential, with the second generally being the slowest. Accordingly,
dihydride intermediates IrH2{κ2-C,N-[C6H4-isoqui-O-C6H5]}­(PiPr3)2 (2d), IrH2{κ2-N,N-[NBzim-py-C6H5]}­(PiPr3)2 (3d), IrH2{κ2-N,N-[Ind-py-C6H5]}­(PiPr3)2 (4d), and IrH2{κ2-N,C-[py-C6HMe2-py]}­(PiPr3)2 (7d) were characterized
spectroscopically. Complexes 3 and 5 are
green phosphorescent emitters upon photoexcitation, exhibiting good
absorption over a wide range of wavelengths, emission quantum yields
about 0.70 in solution, long enough lifetimes (10–17 μs),
and reversible electrochemical behavior. In agreement with these features,
complex 3 promotes the photocatalytic α-amino C­(sp3)–H arylation of N,N-dimethylaniline and N-phenylpiperidine with 1,4-dicyanobenzene
and 4-cyanopyridine under blue LED light irradiation. The C–C
coupling products are isolated in high yields with only 2 mol % of
photocatalyst after 24 h.