Synthesis, Characterization, and Efficient Catalytic Activities of a Nickel(II) Porphyrin: Remarkable Solvent and Substrate Effects on Participation of Multiple Active Oxidants. Issue 49 (9th August 2017)

• Record Type: Journal Article
• Authors: Ahn, Hye Mi; Bae, Jeong Mi; Kim, Min Jeong; Bok, Kwon Hee; Jeong, Ha Young; Lee, Suk Joong; Kim, Cheal
• Is Part Of: Chemistry. Volume 23:Issue 49(2017)
• Page Start: 11969
• Page End: 11976
• Publication Date: 2017-08-09
• Subjects: multiple active oxidants -- nickel -- ni-oxo species -- porphyrins -- olefin epoxidation; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201702750
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: A new nickel(II) porphyrin complex, [Ni II (porp)] (1 ), has been synthesized and characterized by 1 H NMR, 13 C NMR and mass spectrometry analysis. This Ni II porphyrin complex 1 quantitatively catalyzed the epoxidation reaction of a wide range of olefins with meta ‐chloroperoxybenzoic acid ( m ‐CPBA) under mild conditions. Reactivity and Hammett studies, H2 18 O‐exchange experiments, and the use of PPAA (peroxyphenylacetic acid) as a mechanistic probe suggested that participation of multiple active oxidants Ni II −OOC(O)R2, Ni IV ‐Oxo3, and Ni III ‐Oxo4 within olefin epoxidation reactions by the nickel porphyrin complex is markedly affected by solvent polarity, concentration, and type of substrate. In aprotic solvent systems, such as toluene, CH2 Cl2, and CH3 CN, multiple oxidants, Ni II −(O)R2, Ni IV ‐Oxo3, and Ni III ‐Oxo4, operate simultaneously as the key active intermediates responsible for epoxidation reactions of easy‐to‐oxidize substrate cyclohexene, whereas Ni IV ‐Oxo3 and Ni III ‐Oxo4 species become the common reactive oxidant for the difficult‐to‐oxidize substrate 1‐octene. In a protic solvent system, a mixture of CH3 CN and H2 O (95:5), the Ni II −OOC(O)R2 undergoes heterolytic or homolytic O−O bond cleavage to afford Ni IV ‐Oxo3 and Ni III ‐Oxo4 species by general acid catalysis prior to direct interaction between2 and olefin, regardless of the type of substrate. In this case, only Ni IV ‐Oxo3 and Ni III ‐Oxo4 species were the common reactive oxidant responsible for olefin epoxidation reactions. Abstract : Multiple active oxidants : In oxidation reactions catalyzed by a new nickel(II) porphyrin complex, participation of the active oxidants is markedly influenced by solvent polarity, concentration, and type of substrate. Three active oxidants, Ni IV ‐Oxo, Ni III ‐Oxo, and Ni II ‐OOC(O)R, operate simultaneously in aprotic solvents, whereas two active oxidants, Ni IV ‐Oxo and Ni III ‐Oxo, operate in protic solvents.