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Review
. 2023 Oct 23;4(1):41-58.
doi: 10.1021/acsorginorgau.3c00048. eCollection 2024 Feb 7.

Diazines and Triazines as Building Blocks in Ligands for Metal-Mediated Catalytic Transformations

Julianna S Doll  1 , Felix J Becker  1 , Dragoş-Adrian Roşca  1
Affiliations
Review

Diazines and Triazines as Building Blocks in Ligands for Metal-Mediated Catalytic Transformations

Julianna S Doll et al. ACS Org Inorg Au. .

Abstract

Pyridine is a ubiquitous building block for the design of very diverse ligand platforms, many of which have become indispensable for catalytic transformations. Nevertheless, the isosteric pyrazine, pyrimidine, and triazine congeners have enjoyed thus far a less privileged role in ligand design. In this review, several applications of such fragments in the design of new catalysts are presented. In a significant number of cases described, diazine- and triazine-based ligands either outperform their pyridine congeners or offer alternative catalytic pathways which enable new reactivities. The potential opportunities unlocked by using these building blocks in ligand design are discussed, and the origin of the enhanced catalytic activity is highlighted where mechanistic studies are available.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Figure 1
Figure 1
Brief overview of role and binding modes of pyridine ligands in transition metal chemistry.
Figure 2
Figure 2
(a) NICS data; optimization: B3LYP/def2-TZVP/D3BJ, NMR: pcSseg-3. (b) Data from ref (16). (c) Data from ref (14). (d) Values are given relative to vertical excitation energy of pyridine: 4.94 eV.
Figure 3
Figure 3
Remote-site functionalization effects in catalysis exemplified on diazine ligands.
Figure 4
Figure 4
Generation of “abnormal” NHCs from pyrazines and pyrimidines and application in redox-switchable catalysis.
Figure 5
Figure 5
Ligand-design elements for pyridine-diimines (PDI), their diazine-analogues, and other examples of diazine-based redox-active pincers.
Figure 6
Figure 6
Calculated frontier orbital energies in (PDI)Fe(CO)2 and their diazine analogues. Comparison of experimental redox-potentials and νCO stretching frequencies from IR spectroscopy. aData taken from ref (53).
Figure 7
Figure 7
Pyrmidinediimine (PPymDI) iron and cobalt complexes and examples of enhanced stability compared to the pyridine analogues under [2 + 2]-cycloaddition and hydroboration conditions.
Figure 8
Figure 8
1,3,5-Selective trimerization of alkynes catalyzed by (PPymDI)Fe-systems.
Figure 9
Figure 9
Observed deactivation pathways and limitations of (PPymDI)Fe-complexes.
Figure 10
Figure 10
Chemical MLC mechanisms of pyridine-based PNP-ligands and examples of known diazine and triazine analogues.
Figure 11
Figure 11
Diazine- and triazine-based PNP ligands as actor ligands.
Figure 12
Figure 12
Pyrazine-based PNP active ligands in CO2 hydrogenation catalysis.
Figure 13
Figure 13
Triazine-based PNP complexes in MLC-type bond activation reactions and their applications in catalysis.
Figure 14
Figure 14
Key steps in imine reduction, highlighting the role of secondary triazine···K···substrate interactions.
Figure 15
Figure 15
Active triazine-based PNP ligands.
See this image and copyright information in PMC

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