Preparation of five- and six-coordinate aryl(hydrido) iridium(iii) complexes from benzene and functionalized arenes by C–H activation

Abstract

The reaction of the in situ generated cyclooctene iridium(I) derivative trans-[IrCl(C₈H₁₄)(PiPr₃)₂] with benzene at 80 °C gave a mixture of the five-coordinate dihydrido and hydrido(phenyl) iridium(III) complexes [IrH₂(Cl)(PiPr₃)₂] 2 and [IrH(C₆H₅)(Cl)(PiPr₃)₂] 3 in the ratio of about 1 : 2. The chloro- and fluoro-substituted arenes C₆H₅X (X = Cl, F), C₆H₄F₂ and C₆H₄F(CH₃) reacted also by C–H activation to afford the corresponding aryl(hydrido) iridium(III) derivatives [IrH(C₆H₄X)(Cl)(PiPr₃)₂] 7, 8, [IrH(C₆H₃F₂)(Cl)(PiPr₃)₂] 9–11 and [IrH{C₆H₃F(CH₃)}(Cl)(PiPr₃)₂] 12, 13, respectively. The formation of isomeric mixtures had been detected by ¹H, ¹³C, ¹⁹F and ³¹P NMR spectroscopy. Treatment of 3 and 7–13 with CO gave the octahedral carbonyl iridium(III) complexes [IrH(C₆H₃XX′)(Cl)(CO)(PiPr₃)₂] 5, 14–20 without the elimination of the arene. The reactions of trans-[IrCl(C₈H₁₄)(PiPr₃)₂] with aryl ketones C₆H₅C(O)R (R = Me, Ph), aryl ketoximes C₆H₅C(NOH)R (R = Me, Ph) and benzaloxime C₆H₅C(NOH)H resulted in the formation of six-coordinate aryl(hydrido) iridium(III) compounds 21–25 with the aryl ligand coordinated in a bidentate κ²-C,O or κ²-C,N fashion. With C₆H₅C(O)NH₂ as the substrate, the two isomers [IrH{κ²-N,O-NHC(O)C₆H₅}(Cl)(PiPr₃)₂] 26 and [IrH{κ²-C,O-C₆H₄C(O)NH₂}(Cl)(PiPr₃)₂] 27 were prepared stepwise. Treatment of trans-[IrCl(C₈H₁₄)(PiPr₃)₂] with benzoic acid gave the benzoato(hydrido) complex [IrH{κ²-O,O-O₂CC₆H₅}(Cl)(PiPr₃)₂] 29 which did not rearrange to the κ²-C,O isomer.