1007096-32-3Relevant academic research and scientific papers
Carbon-hydrogen bond activation of arenes by a [bis(oxazolinyl)phenyl]- rhodium(III) acetate complex
Ito, Jun-Ichi,Nishiyama, Hisao
, p. 1114 - 1119 (2007)
Thermolysis of the rhodium(III) complex [(dm-Phebox-dm)-Rh(OAc) 2(H2O)] [1; dm-Phebox-dm = 2,6-bis(4,4-dimethyloxazolinyl) phenyl] in various arenes results in the formation of the corresponding aryl complexes [(dm-Phebox-dm)Rh(Ar) (κ2-OAc)] [Ar = C 6H5 (2), 3,5-Me2C6H3 (3), 3,4-Me2C6H3 (4), C6H4Me (5), C6H4CF3 (6), C6H4OMe (7), C6H4COMe (8), C6H4Cl (9)]. The reaction of 1 with monosubstituted benzenes such as toluene, anisole, acetophenone, trifluorotoluene, and chlorobenzene produces a mixture of meta- and para-activated complexes, the ratio of which depends on the substituents on the benzene ring. The relative rate of the reaction of 1 with monosubstituted benzenes C6H5X was determined to be: X = OMe (1.8) > COMe (1.6) > CF3 (1.2), Cl (1.2) > CH3 (1). The acetato ligand of 1 appears to be essential for C-H bond activation of arenes as no reaction of the RhIII complex [(dm-Phebox-dm)RhCl 2(H2O)] is observed in chlorobenzene at 120°C. The first-order rate constants obtained by thermolysis of 1 in [D 8]toluene at 97.1-116.5°C yielded the following activation parameters: ΔH? = 22(2) kcalmol-1 ΔS? = -24(5) calmol-1 K-1. The kinetic isotope effect for the C-H bond activation of toluene by 1 was determined to be kH/k D = 5.4 at 100 °C. These data suggest that the rate-determining step involves the C-H bond cleavage with a rigid, cyclic transition structure. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.
