The role of a redox-active non-innocent ligand in additive-free C-C Glaser-Hay and Suzuki coupling reactions by an -aminophenol palladium() complex
A novel mononuclear palladium complex with 2-(3,5-di- tert -butyl-2-hydroxyphenyl amino) benzonitrile as a non-innocent ligand (abbreviated as Pd II L 2 NIS ) was synthesized, and characterized by IR, UV-Vis, 1 H and 13 C NMR spectroscopies and elemental analysis. The crystal structure clearly showe...
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Published in | RSC advances Vol. 13; no. 5; pp. 3278 - 3289 |
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Main Authors | , , , , |
Format | Journal Article |
Published |
20.01.2023
|
Online Access | Get full text |
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Summary: | A novel mononuclear palladium complex with 2-(3,5-di-
tert
-butyl-2-hydroxyphenyl amino) benzonitrile as a non-innocent ligand (abbreviated as Pd
II
L
2
NIS
) was synthesized, and characterized by IR, UV-Vis,
1
H and
13
C NMR spectroscopies and elemental analysis. The crystal structure clearly showed that the metal center was in a square planar environment. The bond lengths obtained from X-ray structure analysis revealed that both ligands are in the
o
-iminobenzosemiquinone radical form. The neutral complex showed strong absorptions in the NIR region, corresponding to the ILCT (intra-ligand charge transfer). Catalytic tests performed for the coupling reaction of terminal alkynes showed that the palladium Pd
II
L
2
NIS
complex acts as a highly effective catalyst for the base-free C-C coupling reactions, leading to diyne derivatives with excellent yields. The Pd
II
L
2
NIS
complex in ethanol, as a green solvent, is demonstrated to be an exceptionally active phosphine-free catalyst for the Suzuki reaction of aryl iodides and bromides. The reaction can be carried out under mild conditions (room temperature) with high yields without using a microwave or phosphine ligands. This catalyst exhibits an interesting application of redox non-innocent ligands, the electron reservoir behavior, which makes it needless to use additional reagents. The theoretical calculation provides more details about the complex structure, molecular orbitals, and electronic state.
A palladium complex of non-innocent ligand a was synthesized, and characterized by IR, UV-Vis,
1
H and
13
C NMR spectroscopies and elemental analysis. |
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Bibliography: | Electronic supplementary information (ESI) available. CCDC For ESI and crystallographic data in CIF or other electronic format see DOI https://doi.org/10.1039/d2ra07252a 2157991 |
ISSN: | 2046-2069 |
DOI: | 10.1039/d2ra07252a |