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Deactivation of a Cobalt Catalyst for Water Reduction through Valence Tautomerism
Author(s) -
Baydoun Habib,
Mazumder Shivnath,
Schlegel H. Bernhard,
Verani Cláudio N.
Publication year - 2017
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201701783
Subject(s) - catalysis , tautomer , chemistry , overpotential , protonation , cobalt , ligand (biochemistry) , valence (chemistry) , metal , pyridine , medicinal chemistry , inorganic chemistry , organic chemistry , ion , electrode , biochemistry , receptor , electrochemistry
The activity of the water reduction catalyst [Co III (L 1 )(pyr) 2 ]PF 6 ( 1 ), where (L 1 ) 2− is a bis‐amido pyridine ligand and pyr is pyrrolidine, is investigated. Catalyst 1 has an overpotential of 0.54 V and a high observed TOF of 23 min −1 , albeit for a relatively short time. Considering the significant activity of 1 and aiming to improve catalyst design, a detailed structural and electronic study is performed to understand the mechanisms of deactivation. Experimental and theoretical evidence support that the metal‐reduced [Co I (L 1 )] − is in tautomeric equilibrium with the ligand‐reduced [Co II (L 1 . )] − species. While [Co I (L 1 )] − favors formation of a Co III −H − relevant for catalysis, the [Co II (L 1 . )] − species leads to ligand protonation, structural distortions, and, ultimatley, catalyst deactivation.