Authors: María José Benítez | Marı́a L. Buil | Miguel A. Esteruelas | Ana M. López | Cristina Martín-Escura | Enrique Oñate
Source: Inorganic Chemistry (article, 2024-03-28)
Field: Chemistry — Organic Chemistry

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 IrH<sub>5</sub>(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>1</b>) activates two different σ-bonds of 3-phenoxy-1-phenylisoquinoline, 2-(1<i>H</i>-benzimidazol-2-yl)-6-phenylpyridine, 2-(1<i>H</i>-indol-2-yl)-6-phenylpyridine, 2-(2-hydroxyphenyl)-6-phenylpyridine, <i>N</i>-(2-hydroxyphenyl)-<i>N</i>'-phenylimidazolylidene, and 1,3-di(2-pyridyl)-4,6-dimethylbenzene to give IrH{κ<sup>3</sup>-<i>C,N,C</i>-[C<sub>6</sub>H<sub>4</sub>-isoqui-O-C<sub>6</sub>H<sub>4</sub>]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>2</b>), IrH{κ<sup>3</sup>-<i>N,N,C</i>-[NBzim-py-C<sub>6</sub>H<sub>4</sub>]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>3</b>), IrH{κ<sup>3</sup>-<i>N,N,C</i>-[Ind-py-C<sub>6</sub>H<sub>4</sub>]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>4</b>), IrH{κ<sup>3</sup>-<i>C,N,O</i>-[C<sub>6</sub>H<sub>4</sub>-py-C<sub>6</sub>H<sub>4</sub>O]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>5</b>), IrH{κ<sup>3</sup>-<i>C,C,O</i>-[C<sub>6</sub>H<sub>4</sub>-Im-C<sub>6</sub>H<sub>4</sub>O]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>6</b>), and IrH{κ<sup>3</sup>-<i>N,C,C</i>-[py-C<sub>6</sub>HMe<sub>2</sub>-C<sub>5</sub>H<sub>3</sub>N]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>7</b>), respectively. The activations are sequential, with the second generally being the slowest. Accordingly, dihydride intermediates IrH<sub>2</sub>{κ<sup>2</sup>-<i>C,N</i>-[C<sub>6</sub>H<sub>4</sub>-isoqui-O-C<sub>6</sub>H<sub>5</sub>]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>2d</b>), IrH<sub>2</sub>{κ<sup>2</sup>-<i>N,N</i>-[NBzim-py-C<sub>6</sub>H<sub>5</sub>]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>3d</b>), IrH<sub>2</sub>{κ<sup>2</sup>-<i>N,N</i>-[Ind-py-C<sub>6</sub>H<sub>5</sub>]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>4d</b>), and IrH<sub>2</sub>{κ<sup>2</sup>-<i>N,C</i>-[py-C<sub>6</sub>HMe<sub>2</sub>-py]}(P<sup>i</sup>Pr<sub>3</sub>)<sub>2</sub> (<b>7d</b>) were characterized spectroscopically. Complexes <b>3</b> and <b>5</b> 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 <b>3</b> promotes the photocatalytic α-amino C(sp<sup>3</sup>)-H arylation of <i>N</i>,<i>N</i>-dimethylaniline and <i>N</i>-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. Iridium ; Chemistry ; Phosphorescence ; Phosphine ; Hydride ; Stereochemistry ; Medicinal chemistry ; Crystallography ; Photochemistry ; Catalysis ; Physics ; Metal ; Fluorescence ; Organic chemistry Catalytic C–H Functionalization Methods ; Catalytic Cross-Coupling Reactions ; Radical Photochemical Reactions