TY - JOUR
T1 - Mononuclear Manganese(III) Superoxo Complexes
T2 - Synthesis, Characterization, and Reactivity
AU - Lin, Yen Hao
AU - Cramer, Hanna Hinrika
AU - Van Gastel, Maurice
AU - Tsai, Yi Hsuan
AU - Chu, Chi Yi
AU - Kuo, Ting Shen
AU - Lee, I. Ren
AU - Ye, Shengfa
AU - Bill, Eckhard
AU - Lee, Way Zen
N1 - Funding Information:
We thank Mr. Dennis Skerra at the Max-Planck Institute for Chemical Energy Conversion for resonance Raman measurements. We are grateful for the financial support from the Ministry of Science and Technology of Taiwan (MOST 105-2113-M-003-005-MY3 to W.-Z.L.) and the Max-Planck Society, in particular, the joint work space between MPI-CEC and MPI-KOFO. W.-Z.L. and S.Y. also acknowledge the MOST-DAAD Project-Based Personnel Exchange Program (MOST 107-2911-I-003-502 and DAAD 57320810).
PY - 2019/8/5
Y1 - 2019/8/5
N2 - Metal-superoxo species are typically proposed as key intermediates in the catalytic cycle of dioxygen activation by metalloenzymes involving different transition metal cofactors. In this regard, while a series of Fe-, Co-, and Ni-superoxo complexes have been reported to date, well-defined Mn-superoxo complexes remain rather rare. Herein, we report two mononuclear MnIII-superoxo species, Mn(BDPP)(O2 •-) (2, H2BDPP = 2,6-bis((2-(S)-diphenylhydroxylmethyl-1-pyrrolidinyl)methyl)pyridine) and Mn(BDPBrP)(O2 •-) (2′, H2BDPBrP = 2,6-bis((2-(S)-di(4-bromo)phenylhydroxyl-methyl-1-pyrrolidinyl)methyl)pyridine), synthesized by bubbling O2 into solutions of their MnII precursors, Mn(BDPP) (1) and Mn(BDPBrP) (1′), at -80 °C. A combined spectroscopic (resonance Raman and electron paramagnetic resonance (EPR) spectroscopy) and computational study evidence that both complexes contain a high-spin MnIII center (SMn = 2) antiferromagnetically coupled to a superoxo radical ligand (SOO• = 1/2), yielding an overall S = 3/2 ground state. Complexes 2 and 2′ were shown to be capable of abstracting a H atom from 2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPO-H) to form MnIII-hydroperoxo species, Mn(BDPP)(OOH) (5) and Mn(BDPBrP)(OOH) (5′). Complexes 5 and 5′ can be independently prepared by the reactions of the isolated MnIII-aqua complexes, [Mn(BDPP)(H2O)]OTf (6) and [Mn(BDPBrP)(H2O)]OTf (6′), with H2O2 in the presence of NEt3. The parallel-mode EPR measurements established a high-spin S = 2 ground state for 5 and 5′.
AB - Metal-superoxo species are typically proposed as key intermediates in the catalytic cycle of dioxygen activation by metalloenzymes involving different transition metal cofactors. In this regard, while a series of Fe-, Co-, and Ni-superoxo complexes have been reported to date, well-defined Mn-superoxo complexes remain rather rare. Herein, we report two mononuclear MnIII-superoxo species, Mn(BDPP)(O2 •-) (2, H2BDPP = 2,6-bis((2-(S)-diphenylhydroxylmethyl-1-pyrrolidinyl)methyl)pyridine) and Mn(BDPBrP)(O2 •-) (2′, H2BDPBrP = 2,6-bis((2-(S)-di(4-bromo)phenylhydroxyl-methyl-1-pyrrolidinyl)methyl)pyridine), synthesized by bubbling O2 into solutions of their MnII precursors, Mn(BDPP) (1) and Mn(BDPBrP) (1′), at -80 °C. A combined spectroscopic (resonance Raman and electron paramagnetic resonance (EPR) spectroscopy) and computational study evidence that both complexes contain a high-spin MnIII center (SMn = 2) antiferromagnetically coupled to a superoxo radical ligand (SOO• = 1/2), yielding an overall S = 3/2 ground state. Complexes 2 and 2′ were shown to be capable of abstracting a H atom from 2,2,6,6-tetramethyl-1-hydroxypiperidine (TEMPO-H) to form MnIII-hydroperoxo species, Mn(BDPP)(OOH) (5) and Mn(BDPBrP)(OOH) (5′). Complexes 5 and 5′ can be independently prepared by the reactions of the isolated MnIII-aqua complexes, [Mn(BDPP)(H2O)]OTf (6) and [Mn(BDPBrP)(H2O)]OTf (6′), with H2O2 in the presence of NEt3. The parallel-mode EPR measurements established a high-spin S = 2 ground state for 5 and 5′.
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U2 - 10.1021/acs.inorgchem.9b00767
DO - 10.1021/acs.inorgchem.9b00767
M3 - Article
C2 - 31328507
AN - SCOPUS:85071059958
VL - 58
SP - 9756
EP - 9765
JO - Inorganic Chemistry
JF - Inorganic Chemistry
SN - 0020-1669
IS - 15
ER -