Inorganic Chemistry
Article
concentration of the nitrite and Co catalyst, and independent
of pH. In addition, this mechanism is consistent with the
experimentally observed KIE, as proton transfer occurs
intramolecularly from the amine group of the DIM ligand.
ORCID
Notes
SUMMARY AND CONCLUSIONS
This work provides mechanistic insights into the electro-
catalytic reduction of nitrite by [Co(DIM)Br ] . In contrast to
our work on the electrocatalytic reduction of nitrate, which
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The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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The authors thank the National Science Foundation for
financial support (CHE-1566258).
revealed complex aqueous speciation for [Co(DIM)Br ] , use
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of the stronger field nitrite ligand results in six-coordinate
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complex [Co(DIM)(NO ) ] being the only species observed
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REFERENCES
in aqueous solutions. One-electron reduction of this complex is
coupled to the loss of an axial nitrite ligand. An additional
single-electron reduction leads to the formally Co(I) active
catalyst that is better described as Co(II)-DIM(-I) according
to the electronic structure calculations, which can reversibly
bind nitrite. Thus, despite the stronger metal−ligand bond
formed with nitrite, the active catalyst is similar to that
previously proposed for nitrate reduction. However, in contrast
to this earlier work, our investigations here reveal the critical
importance of the macrocycle N−H groups to electrocatalysis.
Specifically, intramolecular proton transfer facilitates N−O
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both DFT calculations and the experimentally determined
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(
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