TY - JOUR
T1 - Synthesis, Characterization, and Catalytic Activities of A Nickel(II) Monoamido-Tetradentate Complex
T2 - Evidence For NiIII–Oxo and NiIV–Oxo Species
AU - Bok, Kwon Hee
AU - Lee, Myoung Mi
AU - You, Ga Rim
AU - Ahn, Hye Mi
AU - Ryu, Ka Young
AU - Kim, Sung Jin
AU - Kim, Youngmee
AU - Kim, Cheal
N1 - Publisher Copyright:
© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
PY - 2017/3/2
Y1 - 2017/3/2
N2 - A new mononuclear nickel(II) complex, [NiII(dpaq)Cl] (1), containing a tetradentate monoamido ligand, dpaq (dpaq=2-[bis(pyridin-2-ylmethyl)amino]-N-(quinolin-8-yl)acetamide), has been synthesized and characterized by IR spectroscopy, elemental analysis, and UV/Vis spectroscopy. The structure of the nickel complex has been determined by X-ray crystallography. This nonheme NiII complex 1 catalyzed the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (m-CPBA) under mild conditions. Olefin epoxidation using this catalytic system has been proposed to involve a new reactive NiIV–oxo (4) species, based on the evidence from a PPAA (peroxyphenylacetic acid) probe, Hammett studies, H218O exchange experiments, and ESI mass spectroscopic analysis. Moreover, the nature of solvent significantly influenced partitioning between heterolytic and homolytic O−O bond cleavage of the Ni–acylperoxo intermediate (2). The O−O bond of 2 proceeded predominantly through heterolytic cleavage in a protic solvent, such as CH3OH. These results suggest that possibly a NiIV–oxo species is a common reactive intermediate in protic solvents. The two active oxidants, namely NiIV–oxo (3) and NiIII–oxo (4), which are responsible for stereospecific olefin epoxidation and radical-type oxidations, respectively, operate in aprotic solvents.
AB - A new mononuclear nickel(II) complex, [NiII(dpaq)Cl] (1), containing a tetradentate monoamido ligand, dpaq (dpaq=2-[bis(pyridin-2-ylmethyl)amino]-N-(quinolin-8-yl)acetamide), has been synthesized and characterized by IR spectroscopy, elemental analysis, and UV/Vis spectroscopy. The structure of the nickel complex has been determined by X-ray crystallography. This nonheme NiII complex 1 catalyzed the epoxidation reaction of a wide range of olefins with meta-chloroperoxybenzoic acid (m-CPBA) under mild conditions. Olefin epoxidation using this catalytic system has been proposed to involve a new reactive NiIV–oxo (4) species, based on the evidence from a PPAA (peroxyphenylacetic acid) probe, Hammett studies, H218O exchange experiments, and ESI mass spectroscopic analysis. Moreover, the nature of solvent significantly influenced partitioning between heterolytic and homolytic O−O bond cleavage of the Ni–acylperoxo intermediate (2). The O−O bond of 2 proceeded predominantly through heterolytic cleavage in a protic solvent, such as CH3OH. These results suggest that possibly a NiIV–oxo species is a common reactive intermediate in protic solvents. The two active oxidants, namely NiIV–oxo (3) and NiIII–oxo (4), which are responsible for stereospecific olefin epoxidation and radical-type oxidations, respectively, operate in aprotic solvents.
KW - epoxidation
KW - nickel
KW - nickel-oxo species
KW - olefins
KW - oxidation
UR - http://www.scopus.com/inward/record.url?scp=85014570880&partnerID=8YFLogxK
U2 - 10.1002/chem.201605157
DO - 10.1002/chem.201605157
M3 - Article
C2 - 28000284
AN - SCOPUS:85014570880
SN - 0947-6539
VL - 23
SP - 3117
EP - 3125
JO - Chemistry - A European Journal
JF - Chemistry - A European Journal
IS - 13
ER -