4165-62-2Relevant articles and documents
Hotta
, p. 687 (1967)
Acid p Ka Dependence in O-O Bond Heterolysis of a Nonheme FeIII-OOH Intermediate to Form a Potent FeVa? O Oxidant with Heme Compound I-Like Reactivity
Xu, Shuangning,Draksharapu, Apparao,Rasheed, Waqas,Que, Lawrence
, p. 16093 - 16107 (2019)
Protons play essential roles in natural systems in controlling O-O bond cleavage of peroxoiron(III) species to give rise to the high-valent iron oxidants that carry out the desired transformations. Herein, we report kinetic and mechanistic evidence that acids can control the mode of O-O bond cleavage for a nonheme S = 1/2 FeIII-OOH species [(BnTPEN)FeIII(OOH)]2+ (2, BnTPEN = N-benzyl-N,N′,N′-tris(2-pyridylmethyl)-1,2-diaminoethane). Addition of acids having pKa values of >8.5 in CH3CN results in O-O bond homolysis, leading to the formation of hydroxyl radicals that give rise to alcohol/ketone (A/K) ratios of around 1 in the oxidation of cyclohexane. However, the introduction of acids with pKa values of III-OOH intermediate at -40 °C. These results implicate the generation of a highly reactive FeV? O species via proton-assisted O-O bond heterolysis of the FeIII-OOH intermediate, which is unprecedented for nonheme iron complexes supported by neutral pentadentate ligands and serves as a nonheme analogue for heme enzyme compounds I.
Efficient continuous-flow HD exchange reaction of aromatic nuclei in D2O/2-PrOH mixed solvent in a catalyst cartridge packed with platinum on carbon beads
Park, Kwihwan,Ito, Naoya,Yamada, Tsuyoshi,Sajiki, Hironao
supporting information, p. 600 - 605 (2021/03/29)
Herein, a continuous-flow deuteration methodology for various aromatic compounds is developed based on heterogeneous platinum-catalyzed hydrogen-deuterium exchange. The reaction entails the transfer of a substrate dissolved in a mixed solvent of 2-propanol and deuterium oxide into a catalyst cartridge packed with platinum on carbon beads (Pt/CB). Pt/ CB could be continuously used without significant deterioration of catalyst activity for at least 24 h. Deuteration proceeded within 60 s of the substrate solutions being passed through the Pt/CB layer in the Pt/CB-packed cartridge.
Single-step benzene hydroxylation by cobalt(ii) catalysts: Via a cobalt(iii)-hydroperoxo intermediate
Anandababu, Karunanithi,Mayilmurugan, Ramasamy,Muthuramalingam, Sethuraman,Velusamy, Marappan
, p. 2540 - 2548 (2020/05/14)
The cobalt(ii) complexes of 4N tetradentate ligands have been synthesized and characterized as the catalysts for phenol synthesis in a single step. The molecular structure of the complexes showed a geometry in between square pyramidal and trigonal bipyramidal (τ, 0.49-0.88) with Co-Namine and Co-NPy bond distances of 2.104-2.254 ? and 2.043-2.099 ?, respectively. The complexes exhibited a Co2+/Co3+ redox potential around 0.489-0.500 V vs. Ag/Ag+ in acetonitrile. The complexes catalyzed hydroxylation of benzene using H2O2 (30%) and afforded phenol selectively as the major product. A maximum yield of phenol up to 29% and turnover number (TON) of 286 at 60 °C, and a yield of 19% and TON of 191 at 25 °C are achieved. This is the highest catalytic performance reported using cobalt(ii) complexes as catalysts to date. This aromatic hydroxylation presumably proceeded via a cobalt(iii)-hydroperoxo species, which was characterized by ESI-MS, and vibrational and electronic spectral methods. The formation of key intermediate [(L)CoIII(OOH)]2+ was accompanied by the appearance of the characteristic O → Co(iii) ligand to metal charge transfer (LMCT) transition around 488-686 nm and vibration modes at 832 cm-1 (O-OH) and 564 cm-1 (Co-O). The geometry of one of the catalytically active intermediates was optimized by DFT and its spectral properties were calculated by TD-DFT calculations. These data are comparable to the experimental observations. The kinetic isotope effect (KIE) values (0.98-1.07) support the involvement of cobalt-bound oxygen species as a key intermediate. Isotope-labeling experiments using H218O2 showed an 89% incorporation of 18O, revealing that H2O2 is the main oxygen supplier for phenol formation from benzene. The catalytic efficiencies of cobalt complexes are tuned by ligand architectures via their geometrical configurations and steric properties.
