Iridium derivatives of fluorinated aromatics by C–H activation: isolation of classical and non-classical hydrides

Abstract

A reaction of trans-[Ir(H)₅(PiPr₃)₂] (1) with 2,3,5,6-tetrafluoropyridine, pentafluorobenzene or 1,3-difluorobenzene in the presence of neohexene affords the square-pyramidal C–H activation products cis–trans-[Ir(4-C₅NF₄)(H)₂(PiPr₃)₂] (2), cis–trans-[Ir(C₆F₅)(H)₂(PiPr₃)₂] (4) and cis–trans-[Ir(2-C₆H₃F₂)(H)₂(PiPr₃)₂] (6). Irradiation of complex 1 with 2,3,5,6-tetrafluoropyridine or pentafluorobenzene gave the hydrides cis–trans-[Ir(4-C₅NF₄)(H)₂(H₂)(PiPr₃)₂] (3) or cis–trans-[Ir(C₆F₅)(H)₂(H₂)(PiPr₃)₂] (5). The presence of non-classical bound H₂ moieties has been demonstrated by the measurement of T₁ times at different temperatures. For 3 the H–H distance in the H₂ ligand can be estimated to be 0.82 Å. The dihydride compounds 2, 4 and 6 react with CO to yield the complexes cis–trans-[Ir(Ar)(H)₂(CO)(PiPr₃)₂] (7: Ar = 4-C₅NF₄, 8: Ar = C₆F₅, 9: Ar = 2-C₆H₃F₂). A reaction of 2 or 3 with an excess of ethylene leads to the formation of ethane and the Ir(I) ethylene complex trans-[Ir(4-C₅NF₄)(η²-C₂H₄)(PiPr₃)₂] (10). Treatment of 10 with CO furnishes the Ir(I) complex trans-[Ir(4-C₅NF₄)(CO)(PiPr₃)₂] (11).