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Nickel is a Different Pickle: Trends in Water Oxidation Catalysis for Molecular Nickel Complexes
Author(s) -
Hessels Joeri,
MasferrerRius Eduard,
Yu Fengshou,
Detz Remko J.,
Klein Gebbink Robertus J. M.,
Reek Joost N. H.
Publication year - 2020
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.202002164
Subject(s) - catalysis , nickel , chemistry , ligand (biochemistry) , imine , context (archaeology) , transition metal , rational design , combinatorial chemistry , inorganic chemistry , organic chemistry , materials science , nanotechnology , paleontology , biochemistry , receptor , biology
The development of novel water oxidation catalysts is important in the context of renewable fuels production. Ligand design is one of the key tools to improve the activity and stability of molecular catalysts. The establishment of ligand design rules can facilitate the development of improved molecular catalysts. In this paper it is shown that chemical oxidants can be used to probe oxygen evolution activity for nickel‐based systems, and trends are reported that can improve future ligand design. Interestingly, different ligand effects were observed in comparison to other first‐row transition metal complexes. For example, nickel complexes with secondary amine donors were more active than with tertiary amine donors, which is the opposite for iron complexes. The incorporation of imine donor groups in a cyclam ligand resulted in the fastest and most durable nickel catalyst of our series, achieving oxygen evolution turnover numbers up to 380 and turnover frequencies up to 68 min −1 in a pH 5.0 acetate buffer using Oxone as oxidant. Initial kinetic experiments with this catalyst revealed a first order in chemical oxidant and a half order in catalyst. This implies a rate‐determining oxidation step from a dimeric species that needs to break up to generate the active catalyst. These findings lay the foundation for the rational design of molecular nickel catalysts for water oxidation and highlight that catalyst design rules are not generally applicable for different metals.