Top Organomet Chem (2021) 68: 135–180
https://doi.org/10.1007/3418_2020_68
# Springer Nature Switzerland AG 2020
Published online: 29 October 2020
Redox-Active Pincer Ligands
Jarl Ivar van der Vlugt
Contents
1 General Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
2 Pincer Ligands That Undergo Reductive Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
2.1 Bis(imino)pyridine as Redox-Active Pincer Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
2.2 2,2
0 ,2
00 -Terpyridine and Substituted Derivatives Thereof . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
2.3 Other Bis-Azadiene-Based Pincer Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
2.4 Miscellaneous Pincer Systems Amenable to Ligand-Centred Reduction . . . . . . . . . . . . 153
3 Pincer Ligands That Undergo Oxidative Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
3.1 Trianionic Pincer Ligands . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . 155
3.2 Dianionic Pincer Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
3.3 Monoanionic Pincer Ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
3.4 Neutral Pincer Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
4 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Abstract This review aims to provide a comprehensive overview of the emerging
field of redox-active pincer ligands. As such, following a short general introduction
on ligand-centred redox activity, the recent literature is discussed in two separate
sections. The first deals with ligand platforms that predominantly display reductive
chemistry from the ‘parent’ scaffold; the second focusses more on systems that
readily undergo oxidative chemistry. Fundamental stoichiometric reactivity as well
as, where explored, catalytic applications will be discussed. This combined survey
hopefully inspires the exploration and uncovering of many new avenues within the
realm of redox-active pincer chemistry.
Keywords Homogeneous catalysis · Pincer ligand · Redox-active ligand · Singleelectron transfer · Transition metals
J. I. van der Vlugt (*)
Bioinspired Coordination Chemistry and Catalysis Group, Institute of Chemistry Carl von
Ossietzky University Oldenburg, Oldenburg, Germany
e-mail: jarl.ivar.van.der.vlugt@uni-oldenburg.de
https://doi.org/10.1007/3418_2020_68
# Springer Nature Switzerland AG 2020
Published online: 29 October 2020
Redox-Active Pincer Ligands
Jarl Ivar van der Vlugt
Contents
1 General Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
2 Pincer Ligands That Undergo Reductive Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
2.1 Bis(imino)pyridine as Redox-Active Pincer Platform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
2.2 2,2
0 ,2
00 -Terpyridine and Substituted Derivatives Thereof . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
2.3 Other Bis-Azadiene-Based Pincer Platforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
2.4 Miscellaneous Pincer Systems Amenable to Ligand-Centred Reduction . . . . . . . . . . . . 153
3 Pincer Ligands That Undergo Oxidative Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
3.1 Trianionic Pincer Ligands . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . 155
3.2 Dianionic Pincer Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
3.3 Monoanionic Pincer Ligands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
3.4 Neutral Pincer Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
4 Concluding Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Abstract This review aims to provide a comprehensive overview of the emerging
field of redox-active pincer ligands. As such, following a short general introduction
on ligand-centred redox activity, the recent literature is discussed in two separate
sections. The first deals with ligand platforms that predominantly display reductive
chemistry from the ‘parent’ scaffold; the second focusses more on systems that
readily undergo oxidative chemistry. Fundamental stoichiometric reactivity as well
as, where explored, catalytic applications will be discussed. This combined survey
hopefully inspires the exploration and uncovering of many new avenues within the
realm of redox-active pincer chemistry.
Keywords Homogeneous catalysis · Pincer ligand · Redox-active ligand · Singleelectron transfer · Transition metals
J. I. van der Vlugt (*)
Bioinspired Coordination Chemistry and Catalysis Group, Institute of Chemistry Carl von
Ossietzky University Oldenburg, Oldenburg, Germany
e-mail: jarl.ivar.van.der.vlugt@uni-oldenburg.de