Syntheses, structures, and spectroscopic properties of cobalt(III) complexes containing 3- or 4-pyridyl-substituted nitronyl and imino nitroxide ligands

Masahiro Ogita, Youhei Yamamoto, Takayoshi Suzuki, Sumio Kaizaki

Research output: Contribution to journalArticle

28 Citations (Scopus)

Abstract

Several new cobalt(III) complexes incorporating 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NITnpy) (n = 3 or 4) or 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)-imidazolin-1-oxyl (IMnpy) have been prepared. The X-ray crystallographic analyses and the spectroscopic investigations have revealed that the nitronyl or imino nitroxides with the radical character are bound through the pyridyl-N atom to a CoIII center. There are some influences from the radical unpaired electron toward the CoIII complex moiety and those from the coordination of the CoIII ion toward the nature of these radicals which can be detected by 59Co NMR and UV/Vis spectroscopy. Such observed changes coincide with the proposed spin density on the N atom of the pyridyl substituent. Furthermore, it was found that trans-[Co-(acac)2(PPh3)(NIT4py)]+ in methanol was gradually converted into the corresponding IM4py complex, while free NIT4py is stable in methanol. The CoII species formed on the partial decomposition of the NIT4py complex in methanol seems to catalyze the deoxygenation of NIT4py to IM4py.

Original languageEnglish
Pages (from-to)886-894
Number of pages9
JournalEuropean Journal of Inorganic Chemistry
Issue number4
Publication statusPublished - 2002
Externally publishedYes

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Cobalt
Methanol
Ligands
Atoms
Ultraviolet spectroscopy
Oxides
Nuclear magnetic resonance
Ions
Decomposition
X rays
Electrons

Keywords

  • Cobalt
  • Deoxygenation
  • Nitroxides
  • NMR spectroscopy
  • Radicals

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

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abstract = "Several new cobalt(III) complexes incorporating 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NITnpy) (n = 3 or 4) or 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)-imidazolin-1-oxyl (IMnpy) have been prepared. The X-ray crystallographic analyses and the spectroscopic investigations have revealed that the nitronyl or imino nitroxides with the radical character are bound through the pyridyl-N atom to a CoIII center. There are some influences from the radical unpaired electron toward the CoIII complex moiety and those from the coordination of the CoIII ion toward the nature of these radicals which can be detected by 59Co NMR and UV/Vis spectroscopy. Such observed changes coincide with the proposed spin density on the N atom of the pyridyl substituent. Furthermore, it was found that trans-[Co-(acac)2(PPh3)(NIT4py)]+ in methanol was gradually converted into the corresponding IM4py complex, while free NIT4py is stable in methanol. The CoII species formed on the partial decomposition of the NIT4py complex in methanol seems to catalyze the deoxygenation of NIT4py to IM4py.",
keywords = "Cobalt, Deoxygenation, Nitroxides, NMR spectroscopy, Radicals",
author = "Masahiro Ogita and Youhei Yamamoto and Takayoshi Suzuki and Sumio Kaizaki",
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journal = "Chemische Berichte",
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T1 - Syntheses, structures, and spectroscopic properties of cobalt(III) complexes containing 3- or 4-pyridyl-substituted nitronyl and imino nitroxide ligands

AU - Ogita, Masahiro

AU - Yamamoto, Youhei

AU - Suzuki, Takayoshi

AU - Kaizaki, Sumio

PY - 2002

Y1 - 2002

N2 - Several new cobalt(III) complexes incorporating 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NITnpy) (n = 3 or 4) or 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)-imidazolin-1-oxyl (IMnpy) have been prepared. The X-ray crystallographic analyses and the spectroscopic investigations have revealed that the nitronyl or imino nitroxides with the radical character are bound through the pyridyl-N atom to a CoIII center. There are some influences from the radical unpaired electron toward the CoIII complex moiety and those from the coordination of the CoIII ion toward the nature of these radicals which can be detected by 59Co NMR and UV/Vis spectroscopy. Such observed changes coincide with the proposed spin density on the N atom of the pyridyl substituent. Furthermore, it was found that trans-[Co-(acac)2(PPh3)(NIT4py)]+ in methanol was gradually converted into the corresponding IM4py complex, while free NIT4py is stable in methanol. The CoII species formed on the partial decomposition of the NIT4py complex in methanol seems to catalyze the deoxygenation of NIT4py to IM4py.

AB - Several new cobalt(III) complexes incorporating 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NITnpy) (n = 3 or 4) or 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)-imidazolin-1-oxyl (IMnpy) have been prepared. The X-ray crystallographic analyses and the spectroscopic investigations have revealed that the nitronyl or imino nitroxides with the radical character are bound through the pyridyl-N atom to a CoIII center. There are some influences from the radical unpaired electron toward the CoIII complex moiety and those from the coordination of the CoIII ion toward the nature of these radicals which can be detected by 59Co NMR and UV/Vis spectroscopy. Such observed changes coincide with the proposed spin density on the N atom of the pyridyl substituent. Furthermore, it was found that trans-[Co-(acac)2(PPh3)(NIT4py)]+ in methanol was gradually converted into the corresponding IM4py complex, while free NIT4py is stable in methanol. The CoII species formed on the partial decomposition of the NIT4py complex in methanol seems to catalyze the deoxygenation of NIT4py to IM4py.

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