Controlled monodefluorination and alkylation of C(sp)-F bonds by lanthanide photocatalysts: importance of metal-ligand cooperativity
The controlled functionalization of a single fluorine in a CF 3 group is difficult and rare. Photochemical C-F bond functionalization of the sp 3 -C-H bond in trifluorotoluene, PhCF 3 , is achieved using catalysts made from earth-abundant lanthanides, (Cp Me4 ) 2 Ln(2- O -3,5- t Bu 2 -C 6 H 2 )(1-C{...
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Veröffentlicht in: | Chemical science (Cambridge) 2022-12, Vol.13 (47), p.149-141 |
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Hauptverfasser: | , , , , , , , , |
Format: | Artikel |
Sprache: | eng |
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Zusammenfassung: | The controlled functionalization of a single fluorine in a CF
3
group is difficult and rare. Photochemical C-F bond functionalization of the sp
3
-C-H bond in trifluorotoluene, PhCF
3
, is achieved using catalysts made from earth-abundant lanthanides, (Cp
Me4
)
2
Ln(2-
O
-3,5-
t
Bu
2
-C
6
H
2
)(1-C{N(CH)
2
N(
i
Pr)}) (Ln = La, Ce, Nd and Sm, Cp
Me4
= C
5
Me
4
H). The Ce complex is the most effective at mediating hydrodefluorination and defluoroalkylative coupling of PhCF
3
with alkenes; addition of magnesium dialkyls enables catalytic C-F bond cleavage and C-C bond formation by all the complexes. Mechanistic experiments confirm the essential role of the Lewis acidic metal and support an inner-sphere mechanism of C-F activation. Computational studies agree that coordination of the C-F substrate is essential for C-F bond cleavage. The unexpected catalytic activity for all members is made possible by the light-absorbing ability of the redox non-innocent ligands. The results described herein underscore the importance of metal-ligand cooperativity, specifically the synergy between the metal and ligand in both light absorption and redox reactivity, in organometallic photocatalysis.
The controlled functionalization of a single fluorine in a CF
3
group is difficult and rare. Photochemical C-F bond functionalization is achieved using catalysts made from a range of earth-abundant lanthanides by using a ligand that enables M-L cooperativity. |
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ISSN: | 2041-6520 2041-6539 |
DOI: | 10.1039/d2sc04192h |