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C-F bond activation of perfluorinated arenes using NHC-stabilized cobalt half-sandwich complexes
A study on the reactivity of NHC cobalt half-sandwich complexes [(η 5 -C 5 R 1 5 )Co(R 2 2 Im)(η 2 -C 2 H 4 )] (R 1 = H; R 2 = Me 1 , iPr 2 ) and [(η 5 -C 5 R 1 5 )Co(R 2 2 Im)(η 2 -C 2 H 3 {SiMe 3 })] (R 1 = H, R 2 = Me 3 , iPr 4 ; R 1 = Me, R 2 = Me 5 , iPr 6 ) towards selected perfluoroarenes is...
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| Published in: | New journal of chemistry 2021-08, Vol.45 (33), p.14999-1516 |
|---|---|
| Main Authors: | , , , , |
| Format: | Article |
| Language: | English |
| Subjects: | |
| Citations: | Items that this one cites Items that cite this one |
| Online Access: | Get full text |
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| Summary: | A study on the reactivity of NHC cobalt half-sandwich complexes [(η
5
-C
5
R
1
5
)Co(R
2
2
Im)(η
2
-C
2
H
4
)] (R
1
= H; R
2
= Me
1
, iPr
2
) and [(η
5
-C
5
R
1
5
)Co(R
2
2
Im)(η
2
-C
2
H
3
{SiMe
3
})] (R
1
= H, R
2
= Me
3
, iPr
4
; R
1
= Me, R
2
= Me
5
, iPr
6
) towards selected perfluoroarenes is presented (R
2
Im = 1,3-di(organyl)-imidazolin-2-ylidene). The reaction with hexafluorobenzene, perfluorotoluene and decafluorobiphenyl at 100 °C led to the isolation of the cobalt(
ii
) complexes [CpCo(iPr
2
Im)(C
6
F
5
)]
7
, [CpCo(iPr
2
Im)(C
7
F
7
)]
8
, [CpCo(iPr
2
Im)(C
12
F
9
)]
9
, [Cp*Co(iPr
2
Im)(C
6
F
5
)]
10
, [Cp*Co(iPr
2
Im)(C
7
F
7
)]
11
and [Cp*Co(iPr
2
Im)(C
12
F
9
)]
12
(Cp* = η
5
-C
5
{CH
3
}
5
), Cp = η
5
-C
5
H
5
). The cobalt(
ii
) fluoride [CpCo(iPr
2
Im)(F)] was detected as a side product of these reactions. The reaction of [CpCo(R
2
2
Im)(η
2
-C
2
H
4
)] (R
2
= Me
1
, iPr
2
) with C
6
F
6
and C
7
F
8
at 60 °C afforded the dinuclear complexes [{CpCo(R
2
2
Im)}
2
(μ-η
2
,η
2
-C
6
F
6
)] (R
2
= Me
13
, iPr
14
) and [{CpCo(R
2
2
Im)}
2
(μ-η
2
,η
2
-C
7
F
8
)] (R
2
= Me
15
, iPr
16
). Furthermore, the dinuclear complexes [{CpCo(Me
2
Im)}
2
(μ-η
2
,η
2
-C
10
F
8
)]
17
, [{CpCo(iPr
2
Im)}
2
(μ-η
2
,η
2
-C
10
F
8
)]
18
and mononuclear [CpCo(iPr
2
Im)(η
2
-C
10
F
8
)]
19
were isolated from the reaction of
1
and
2
with octafluoronaphthalene at room temperature. Based on the experimental data a mechanism is proposed for the C-F bond activation of perfluoroarenes with complexes [Cp
(*)
Co(NHC)(olefin)]. Transfer of [Cp
(*)
Co(NHC)] to the perfluoroarene, which is limited by the activation barrier to replace the alkene ligand, affords mononuclear cobalt complexes [Cp
(*)
Co(NHC)(η
2
-Ar
F
)]. Ligand dismutation at higher temperatures leads to dinuclear complexes [{Cp
(*)
Co(NHC)}
2
(μ-η
2
,η
2
-Ar
F
)], which are precursors for the formation of the cobalt(
ii
) complexes [Cp
(*)
Co(NHC)(Ar
F
)] and [Cp
(*)
Co(NHC)(F)]. One electron oxidative addition prevails in the C-F bond activation step using these cobalt half-sandwich complexes.
A study on the reactivity of cobalt half-sandwich complexes [Cp
(*)
Co(NHC)(olefin)] with perfluoroarenes demonstrates that C-F activation occurs along a one-electron oxidative addition pathway. |
|---|---|
| ISSN: | 1144-0546 1369-9261 |
| DOI: | 10.1039/d0nj06137a |