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

Abstract

A reaction of trans-[Ir(H)(5)(PiPr(3))(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-C(5)NF(4))(H)(2)(PiPr(3))(2)] (2), cis-trans-[Ir(C(6)F(5))(H)(2)(PiPr(3))(2)] (4) and cis-trans-[Ir(2-C(6)H(3)F(2))(H)(2)(PiPr(3))(2)] (6). Irradiation of complex 1 with 2,3,5,6-tetrafluoropyridine or pentafluorobenzene gave the hydrides cis-trans-[Ir(4-C(5)NF(4))(H)(2)(H(2))(PiPr(3))(2)] (3) or cis-trans-[Ir(C(6)F(5))(H)(2)(H(2))(PiPr(3))(2)] (5). The presence of non-classical bound H(2) moieties has been demonstrated by the measurement of T(1) times at different temperatures. For 3 the H-H distance in the H(2) ligand can be estimated to be 0.82 A. The dihydride compounds 2, 4 and 6 react with CO to yield the complexes cis-trans-[Ir(Ar)(H)(2)(CO)(PiPr(3))(2)] (7: Ar = 4-C(5)NF(4), 8: Ar = C(6)F(5), 9: Ar = 2-C(6)H(3)F(2)). 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-C(5)NF(4))(eta(2)-C(2)H(4))(PiPr(3))(2)] (10). Treatment of 10 with CO furnishes the Ir(i) complex trans-[Ir(4-C(5)NF(4))(CO)(PiPr(3))(2)] (11).

Synthesis and Reactivity of Ru(NHC)(dppp)(CO)H2 and Ru(NHC)(dppp)(CO)HF Complexes: C–H and C–F Activation

“…Previous studies on the reactivity of partially fluorinated aromatic molecules with a wide range of transition metal complexes have revealed a wide variation of chemoselectivity. Thus, [(η 5 -C 5 Me 5 )Re(CO) 3 ], [27] [Rh(PEt 3 ) 3 H], [28] [Ir(PiPr 3 ) 2 H 5 ] [29] and [35,36] to undergo oxidative addition of either C-F or C-H bonds indicate that while C-F activation is always thermodynamically more favourable, a lower kinetic barrier usually exists for C-H cleavage.…”

Synthesis and characterization of new pentamethylcyclopentadienyl iridium hydride complexes

“…The IR spectra shows medium absorptions at 2109 and 1922 cm À1 for compound 1, and strong absorptions at 2095 and 1896 cm À1 for compound 2, attributable to the n (IreH) vibrations [8,9]. The 1 H NMR spectrum shows a high field doublets at d À17.83 ppm ( 2 J HeP ¼ 31.4 Hz) (compound 1), and at d À17.91 ppm ( 2 J HeP ¼ 32.5 Hz) (compound 2), both integrating by two protons, suggesting the presence of two hydride ligands coupled to the phosphorus nucleus of the phosphane ligand.…”

Synthesis, Reactivity and Structures of Iridium Tetrafluoropyridyl Complexes: Ammonia Coordination and Activation

“…Isotope labeling experiments at the ammine complex cis-trans- )(H) 2 (ND 3 )(PiPr 3 ) 2 ] (2b) confirmed an exchange of metal-bound hydrogen atoms with deuterium atoms at the N-D moiety. A hydride abstraction from cis-trans- )(H) 2 (PiPr 3 ) 2 ] (1) or cis-trans- )(H) 2 (NH 3 )-(PiPr 3 ) 2 ] (2a) on using [Ph 3 C] + in benzene gave the cation [(η 6 -C 6 H 6 )Ir(H) 2 (PiPr 3 )] + as well as the C-C coupling product 9-phenyl-9-fluorene (8).…”