Axial Donor Effects on Oxidatively Induced Ethane Formation from Nickel-Dimethyl Complexes

Sofia M. Smith, Nigam P. Rath, Liviu M. Mirica

Research output: Contribution to journalArticle

Abstract

Tetradentate pyridinophane ligands have been shown to stabilize uncommon high-valent palladium and nickel organometallic complexes. Described herein are the synthesis and detailed characterization of a series of NiII- and NiIII-dimethyl complexes supported by modified tetradentate pyridinophane ligands in which one or both of the N-methyl substituents were replaced with electron-withdrawing p-toluenesulfonyl groups, thus reducing the amine N atom donicity and favoring the formation of Ni complexes with lower coordination numbers. The corresponding NiII-dimethyl complexes exhibit accessible oxidation potentials, and their oxidation generates NiIII species that were characterized by EPR and X-ray crystallography. Moreover, the NiII-dimethyl complexes exhibit selective ethane formation upon oxidatively induced reductive elimination using various oxidants - including O2 and H2O2, without the generation of any C-heteroatom products. Overall, these results suggest that the (RN4)NiIIMe2 complexes with more weakly donating axial ligands are more reactive toward ethane formation, likely due to destabilization of the corresponding high-valent Ni intermediates and formation of 5- and 4-coordinate conformations for these Ni species.

Original languageEnglish (US)
Pages (from-to)3602-3609
Number of pages8
JournalOrganometallics
Volume38
Issue number19
DOIs
StatePublished - Oct 14 2019

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Ethane
Nickel
ethane
nickel
Ligands
ligands
Oxidation
X ray crystallography
Palladium
Organometallics
Oxidants
oxidation
Amines
Paramagnetic resonance
Conformations
destabilization
coordination number
crystallography
palladium
elimination

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry

Cite this

Axial Donor Effects on Oxidatively Induced Ethane Formation from Nickel-Dimethyl Complexes. / Smith, Sofia M.; Rath, Nigam P.; Mirica, Liviu M.

In: Organometallics, Vol. 38, No. 19, 14.10.2019, p. 3602-3609.

Research output: Contribution to journalArticle

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N2 - Tetradentate pyridinophane ligands have been shown to stabilize uncommon high-valent palladium and nickel organometallic complexes. Described herein are the synthesis and detailed characterization of a series of NiII- and NiIII-dimethyl complexes supported by modified tetradentate pyridinophane ligands in which one or both of the N-methyl substituents were replaced with electron-withdrawing p-toluenesulfonyl groups, thus reducing the amine N atom donicity and favoring the formation of Ni complexes with lower coordination numbers. The corresponding NiII-dimethyl complexes exhibit accessible oxidation potentials, and their oxidation generates NiIII species that were characterized by EPR and X-ray crystallography. Moreover, the NiII-dimethyl complexes exhibit selective ethane formation upon oxidatively induced reductive elimination using various oxidants - including O2 and H2O2, without the generation of any C-heteroatom products. Overall, these results suggest that the (RN4)NiIIMe2 complexes with more weakly donating axial ligands are more reactive toward ethane formation, likely due to destabilization of the corresponding high-valent Ni intermediates and formation of 5- and 4-coordinate conformations for these Ni species.

AB - Tetradentate pyridinophane ligands have been shown to stabilize uncommon high-valent palladium and nickel organometallic complexes. Described herein are the synthesis and detailed characterization of a series of NiII- and NiIII-dimethyl complexes supported by modified tetradentate pyridinophane ligands in which one or both of the N-methyl substituents were replaced with electron-withdrawing p-toluenesulfonyl groups, thus reducing the amine N atom donicity and favoring the formation of Ni complexes with lower coordination numbers. The corresponding NiII-dimethyl complexes exhibit accessible oxidation potentials, and their oxidation generates NiIII species that were characterized by EPR and X-ray crystallography. Moreover, the NiII-dimethyl complexes exhibit selective ethane formation upon oxidatively induced reductive elimination using various oxidants - including O2 and H2O2, without the generation of any C-heteroatom products. Overall, these results suggest that the (RN4)NiIIMe2 complexes with more weakly donating axial ligands are more reactive toward ethane formation, likely due to destabilization of the corresponding high-valent Ni intermediates and formation of 5- and 4-coordinate conformations for these Ni species.

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