Acetylides for the Preparation of Phosphorescent Iridium(III) Complexes: Iridaoxazoles and Their Transformation into Hydroxycarbenes and N,C(sp 3 ),C(sp 2 ),O -Tetradentate Ligands.

The preparation of three families of phosphorescent iridium(III) emitters, including iridaoxazole derivatives, hydroxycarbene compounds, and N,C(sp 3 ),C(sp 2 ),O -tetradentate containing complexes, has been performed starting from dimers cis -[Ir(μ 2 -η 2 -C≡CR){κ 2 - C,N -(MeC 6 H 3 -py)} 2 ] 2 (R = t Bu ( 1a ), Ph ( 1b )). Reactions of 1a with benzamide, acetamide, phenylacetamide, and trifluoroacetamide lead to the iridaoxazole derivatives Ir{κ 2 - C,O -[C(CH 2 t Bu)NC( R )O]}{κ 2 - C,N -(MeC 6 H 3 -py)} 2 (R = Ph ( 2 ), Me ( 3 ), CH 2 Ph ( 4 ), CF 3 ( 5 )) with a fac disposition of carbons and heteroatoms around the metal center. In 2-methyltetrahydrofuran and dichloromethane, water promotes the C-N rupture of the IrC-N bond of the iridaoxazole ring of 3-5 to form amidate-iridium(III)-hydroxycarbene derivatives Ir{κ 1 - N- [NHC( R )O]}{κ 2 - C,N -(MeC 6 H 3 -py)} 2 {═C(CH 2 t Bu)OH} (R = Me ( 6 ), CH 2 Ph ( 7 ), CF 3 ( 8 )). In contrast to 1a , dimer 1b reacts with benzamide and acetamide to give Ir{κ 4 - N,C,C ' ,O -[py-MeC 6 H 3 -C(CH 2 -C 6 H 4 )NHC( R )O]}{κ 2 - C,N -(MeC 6 H 3 -py)}(R = Ph ( 9 ), Me ( 10 )), which bear a N,C(sp 3 ),C(sp 2 ),O -tetradentate ligand resulting from a triple coupling (an alkynyl ligand, an amide, and a coordinated aryl group) and a C-H bond activation at the metal coordination sphere. Complexes 2-4 and 6-10 are emissive upon photoexcitation, in orange ( 2-4 ), green ( 6-8 ), and yellow ( 9 and 10 ) regions, with quantum yields between low and moderate (0.01-0.50) and short lifetimes (0.2-9.0 μs).