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. 2023 Apr 27;42(9):832-837.
doi: 10.1021/acs.organomet.3c00114. eCollection 2023 May 8.

Synthesis and Characterization of Palladium Pincer Bis(carbene) CCC Complexes

Daniel C Najera  1 , Gabriel Espinosa Martinez  1 , Alison R Fout  2
Affiliations

Synthesis and Characterization of Palladium Pincer Bis(carbene) CCC Complexes

Daniel C Najera et al. Organometallics. .

Abstract

The metalation of the DIPPCCC (DIPPCCC = bis(diisopropylphenyl-imidazol-2-ylidene)phenyl) ligand platform with Pd was achieved under mild conditions by reacting [H3(DIPPCCC)]Cl2 with Pd(OAc)2 at room temperature in the presence of 3.1 equiv of LiN(SiMe3)2. The resulting complexes (DIPPCCC)PdX (X = Cl or Br) were oxidized by two-electron oxidants PhICl2, Br2, and BTMABr3. All the complexes were crystallographically characterized, and analysis of structural parameters around the ligand scaffold show no evidence of a ligand-centered radical, rendering the metal center in the oxidized species, (DIPPCCC)PdX3 (X = Cl or Br), a formal PdIV oxidation state. Unlike their NiIV analogues, these PdIV complexes are stable to air and moisture. The addition of styrene to (DIPPCCC)PdBr3 resulted in the clean reduction of PdIV to PdII, along with the formation of the halogenated alkane. The oxidation to PdIV and subsequent return to PdII upon reduction, as opposed to formation of PdIII species, showcases the accessibility of high-valent palladium DIPPCCC complexes.

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Conflict of interest statement

The authors declare no competing financial interest.

Figures

Scheme 1
Scheme 1. Synthesis of (DIPPCCC)PdCl
Figure 1
Figure 1
Solid-state structures of 1, 2, 3, and 4 shown with 50% probability ellipsoids. H atoms have been omitted for clarity.
Scheme 2
Scheme 2. Oxidation of 1 to (DIPPCCC)PdCl3 (2)
Scheme 3
Scheme 3. Oxidation of 3 to (DIPPCCC)PdBr3 (4)
Scheme 4
Scheme 4. Oxidation of 3 to 4 with SelectFluor
See this image and copyright information in PMC

References

    1. Firsan S. J.; Sivakumar V.; Colacot T. J. Emerging Trends in Cross-Coupling: Twelve-Electron-Based L1Pd(0) Catalysts, Their Mechanism of Action, and Selected Applications. Chem. Rev. 2022, 122, 16983–17027. 10.1021/acs.chemrev.2c00204. - DOI - PMC - PubMed
    1. González-Sebastián L.; Morales-Morales D. Cross-Coupling Reactions Catalysed by Palladium Pincer Complexes. A Review of Recent Advances. J. Organomet. Chem. 2019, 893, 39–51. 10.1016/j.jorganchem.2019.04.021. - DOI
    1. Ruiz-Castillo P.; Buchwald S. L. Applications of Palladium-Catalyzed C–N Cross-Coupling Reactions. Chem. Rev. 2016, 116, 12564–12649. 10.1021/acs.chemrev.6b00512. - DOI - PMC - PubMed
    1. Chen X.; Engle K. M.; Wang D.-H.; Yu J.-Q. Palladium(II)-Catalyzed C-H Activation/C-C Cross-Coupling Reactions: Versatility and Practicality. Angew. Chem., Int. Ed. 2009, 48, 5094–5115. 10.1002/anie.200806273. - DOI - PMC - PubMed
    1. Xue L.; Lin Z. Theoretical Aspects of Palladium-Catalysed Carbon–Carbon Cross-Coupling Reactions. Chem. Soc. Rev. 2010, 39, 1692–1705. 10.1039/B814973A. - DOI - PubMed

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