Cobalt-catalyzed selective C-F bond activation and alkylation of polyfluoroaryl imines

Article abstract of DOI:10.1002/cjoc.201300340

In this paper the C-F bond activation of polyfluoroaryl imines is explored at cobalt(0) center with an imine-N atom as an anchoring group. The reaction of F₅C₆-CH-N-(2′-ClC₆H₄) (2) and F₅C₆

Full text of DOI:10.1002/cjoc.201300340

FULL PAPER
DOI: 10.1002/cjoc.201300340
Cobalt-catalyzed Selective C－F Bond Activation and
Alkylation of Polyfluoroaryl Imines
Faguan Lu, Hongjian Sun, and Xiaoyan Li*
School of Chemistry and Chemical Engineering, Key Laboratory of Special Functional Aggregated Materials,
Ministry of Education, Shandong University, Jinan, 250100 Shandong, China
In this paper the C－F bond activation of polyfluoroaryl imines is explored at cobalt(0) center with an imine-N
atom as an anchoring group. The reaction of F5C6-CH＝N-(2'-ClC6H4) (2) and F5C6-CH＝N-C6H5 (3) with
Co(PMe3)4 afforded the C－F bond activation products (ortho-F4C6-CH＝N-(2'-ClC6H4))Co(I)(PMe3)3 (5) and
(ortho-F4C6-CH＝N-C6H5)Co(II)(F)(PMe3)2 (6), while only π-(C＝N) coordinated cobalt(0) complex (2,4,5-
F3C6H2-CH＝N-(4'-ClC6H4))Co(0)(PMe3)3 (4) was obtained from 2,4,5-F3C6H2-CH＝N-(4'-ClC6H4) (1) without
C－F bond activation. Complexes 4－6 were characterized through X-ray single crystal diffraction. It was also
found that dialkylation of N-(perfluorobenzylidene)benzenamine with organozinc reagents could be catalyzed by
Co(PMe3)4 via C,C-coupling reaction under mild conditions.
Keywords C－F bond activation, cobalt, imine, organozinc reagent, C,C-coupling
Introduction
R
N
F
H
F
PMe3
R
+
H
pentane
-2PMe3
F
Activation of C－F bonds is very meaningful and
remains a significant challenge. How to design transi-
tion metal complexes as catalysts for selective activa-
tion and functionalization of C－F bonds under mild
conditions is attracting more and more attention.[1-6]
There have been some reports on activation of C－F
bonds of fluorinated compounds by the first-row transi-
tion metals.[7-11] Love published her review on cross
coupling reactions of polyfluoroarenes via C－F activa-
tion.[12] However publications on C－F activation by
cobalt complexes are rare. Klein disclosed the C－F
bond activation by Co(PMe3)4Me with the hard donor
atom oxygen as anchoring group. The reaction is pro-
moted by the release of CH3F.[13]
In 2006 we reported our first example about co-
balt(III) complex containing a [C-Co-F] fragment
through cyclometalation reaction involving C－F bond
activation at a cobalt(I) center with an aldazine-N atom
as an anchoring group.[14] After that a series of cobalt
complexes involved C－F bond activation were synthe-
sized.[15-18]
N
(1)
(2)
CoMe(PMe )
Co
PMe3
3 4
F
Me
F
F
H
R
R
pentane
-PMe3
N
Co(PMe3)4
+
N
Co
F
F
PMe3
Me3P
PMe3
As our continuation to study C－F bond activation
of fluorinated imines, the substrates in this investigation
were extended from the 2,6-difluorinated imines in our
early study to the 2,4,5-trifluorinated imine and per-
fluorinated imine in order to increase the opportunity of
C－F bond activation by Co(PMe3)4. As 2,6-difluori-
nated imines, similar π-coordinated cobalt(0) complex 4
was obtained from the reaction of 2,4,5-trifluorinated
imine with Co(PMe3)4. Under similar reaction condi-
tions the reaction of Co(PMe3)4 with perfluorinated im-
ines afforded the C－F bond activation products, co-
balt(I) complexes 5 and cobalt(II) complex 6 containing
[C-Co-F] fragment. To our knowledge, complex 6 is the
first covalent organocobalt(II) fluoride.[19] The struc-
tures of complexes 4, 5 and 6 were determined by X-ray
single crystal diffraction. Based on these research re-
Recently we have found that the C－F bonds of
2,6-difluorinated imines were activated by Co(PMe3)4-
Me (Eq. 1).[16] But in the case of tetrakis(trimethyl-
phosphine)cobalt(0), the expected C－F activation did
not occur. Only a π-coordinated cobalt(0) complex was
isolated (Eq. 2).
*
E-mail: xli63@sdu.edu.cn; Tel.: 0086-0531-88361350; Fax: 0086-0531-88564464
Received April 22, 2013; accepted June 12, 2013; published online July 19, 2013.
Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/cjoc.201300340 or from the author.
Chin. J. Chem. 2013, 31, 927—932
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Lu, Sun & Li
FULL PAPER
X-ray structure determination
sults, the alkylation of perfluorinated imines catalyzed
by Co(PMe3)4 was explored involving C－F bond acti-
vation via C,C-coupling reaction.
Table 1 Crystallographic data for complexes 4, 5 and 6
4
5
6
Experimental
C22H34Cl-
CoF3NP3
C22H32Cl-
CoF4NP3
C19H24-
CoF5NP2
Formula
General procedures and materials
0.22×0.2× 0.21×0.19× 0.32×0.24×
0.19
Size/mm3
Standard vacuum techniques were used in manipula-
tions of volatile and air-sensitive materials. Solvents
were dried by known procedures and distilled under
nitrogen before use. Literature methods were used in the
preparation of Co(PMe3)4.[20,21] Schiff bases were ob-
tained by condensation of polyfluorobenzaldehyde with
amines by refluxing in alcohol solution. Infrared spectra
(4000－400 cm−1), as obtained from Nujol mulls be-
tween KBr disks, were recorded on a Bruker ALPHA
0.15
0.22
Formula weight/
(g•mol−1)
556.79
573.78
482.26
Crystal system
monoclinic orthorhombic monoclinic
Space group
a/Å
P21/n
P212121
P21/c
15.102(3)
1156.80(10) 868.20(7)
b/Å
9.7154(19) 1298.10(10) 1402.10(18)
c/Å
19.236(4)
1633.5(2)
1771.5(2)
1
FT-IR. H, 19F and 31P NMR (300, 282 and 121 MHz,
α/(°)
β/(°)
90
90
90
102.35(3)
90
96.823(9)
respectively) spectra were recorded on a Bruker Avance
300 spectrometer. 19F and 31P NMR resonances were
obtained with broadband proton decoupling. X-ray
crystallography was performed with a Bruker Smart
1000 diffractometer. Elemental analyses were carried
out on an Elementar Vario EL III. Melting points were
measured in capillaries sealed under nitrogen and were
uncorrected.
γ/(°)
V/Å3
90
90
90
2757.0(9)
4
2452.9(4)
4
2141.2(4)
4
Z
Calculated density/
(mg•cm−3)
Absorption coeffi-
cient/mm−1
1.341
0.924
1.554
1.046
1.496
0.998
Reflections collected 15675
18973
5172
15702
4502
Synthesis of complex 4
Indep Rflns
R(int)
6089
A solution of 1 (0.54 g, 2.00 mmol) in 30 mL of
pentane was added to a solution of Co(PMe3)4 (0.91 g,
2.50 mmol) in 30 mL of pentane at −80 ℃ dropwise
within 5 min under N2 atmosphere. The reaction mix-
ture was allowed to warm to ambient temperature and
stirred for 24 h. During this period, the reaction mixture
turned brown in color. After filtering, crystallization
from pentane solution at 4 ℃ yielded brown single
crystals suitable for X-ray structure analysis. Yield 0.53
g (46%). Dec.＞119 ℃. IR (KBr) ν: 1626 (C＝N),
1575 (C ＝ C), 935 (PMe3) cm−1. Anal. calcd for
C22H34ClCoF3NP3 (556.79 g•mol−1): C 47.45, H 6.16, N
2.52; found C 47.52, H 6.48, N 2.46.
0.0431
289
0.0930
417
0.0270
349
Parameters
R1 (all data)
wR2 (all data)
R1 [I＞2σ(I)]
wR2 [I＞2σ(I)]
0.0790
0.1215
0.0479
0.1070
0.0492
0.1350
0.0482
0.1321
1.077
0.0402
0.1023
0.0343
0.0971
0.863
Goodness of fit on F2 1.054
Catalytic study
Compound 3 (0.0542 g, 0.2 mmol) with Co(PMe3)4
(0.02 mmol) and 1.5 equiv. of ZnR2 were dissolved in 3
mL of DME. The reaction mixture was heated to the
given temperature and stirred for the given hours. After
cooled to ambient temperature, the solution was charac-
terized by in situ 19F NMR spectra.
Complexes 5 and 6 were synthesized according to
the method given above for 4.
1
Complex 5 Yield 0.59 g (50%). Dec.＞88 ℃. H
NMR (300 MHz, C6D6, 296 K) δ: 0.85－1.12 (m, 27H,
PCH3), 6.91－7.16 (m, 4H, ArH), 9.28 (s, 1H, CH＝N);
31P NMR (121 MHz, C6D6, 296K) δ: −15.9 (s, 1P,
PMe3), −13.6 (s, 1P, PMe3), −0.8 (s, 1P, PMe3); 19F
NMR (282 MHz, 296 K) δ: −112.1 (s, 1F), −145.5 (s,
1F), −163.4 (s, 1F), −167.9 (s, 1F); IR ν: 1624 (C＝N),
1582 (C ＝ C), 944 (PMe3). Anal. calcd for
C22H32ClCoF4NP3 (573.78 g•mol−1): C 46.05, H 5.62, N
2.44; found C 46.22, H 5.48, N 2.54.
Complex 6 Yield 0.38 g (41%). Dec.＞280 ℃. IR
ν: 1624 (C＝N), 1591, 1541 (C＝C), 942 (PMe3). Anal.
calcd for C19H24CoF5NP2 (482.26 g•mol−1): C 47.32, H
5.02, N 2.90; found C 47.18, H 5.28, N 2.79.
Results and Discussion
Reaction of Co(PMe3)4 with fluorinated benzalimine
In our early study we found that increasing the
number of fluorine atoms on the aromatic rings benefits
the C－F bond cleavage. At first we explored the reac-
tion of trifluoroaryl imine with Co(PMe3)4. The reaction
of compound 1 with Co(PMe3)4 afforded a π-(C＝N)
coordinated cobalt(0) complex 4 as brown crystals in
the yield of 46%. The expected C－F bond activation
product could not be found. The molecular structure of
complex 4 was identified by X-ray diffraction (Figure 1).
928
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Chin. J. Chem. 2013, 31, 927—932

Cobalt-catalyzed Selective C－F Bond Activation and Alkylation of Polyfluoroaryl Imines
Complex 4 has a tetrahedral coordination geometry with
a π-coordinated imine group [C(7)－N(1)] and three
σ-coordinated trimethylphosphine ligands. The C＝N
bond length [N(1)－C(7)＝1.382(4) Å] is a bit shorter
than that [N(1)－C(7)＝1.403(6) Å] in the similar co-
balt complex.[16] This difference might be caused
through the electron-withdrawing effect of fluorine and
chlorine atoms, which makes the π-coordination in
complex 4 weaker.
Cl
F
n-pentane
F
F
N
Co(PMe3)4
+
F2PMe3
F
F
2
F
Cl
N
F
F
(4)
PMe3
PMe3
Co
F
Me3P
Cl
Cl
F
5
F
F
F
Co(PMe )
+
3 4
(3)
N
N
PMe3
F
Co
PMe3
F
Me3P
PMe3
1
4
Figure 2 Molecular structure of complex 5 (all the hydrogen
atoms were omitted for clarity). Selected bond distances (Å) and
angles (°): Co(1)－C(6) 1.940(3), Co(1)－P(1) 2.1914(9), Co(1)
－ P(3) 2.1947(10), Co(1) － P(2) 2.2028(8), N(1) － Co(1)
1.923(3), N(1)－C(7) 1.305(4); N(1)-Co(1)-C(6) 80.87(13), N(1)-
Co(1)-P(1) 109.04(9), C(6)-Co(1)-P(1) 84.94(10), N(1)-Co(1)-
P(3) 124.54(9), C(6)-Co(1)-P(3) 90.35(10), P(1)-Co(1)-P(3)
124.66(4), N(1)-Co(1)-P(2) 97.76(8), C(6)-Co(1)-P(2) 177.21(11),
P(1)-Co(1)-P(2) 93.25(3), P(3)-Co(1)-P(2) 92.43(4).
Figure 1 Molecular structure of complex 4. (All the hydrogen
atoms were omitted for clarity) Selected bond distances (Å) and
angles (°): Co(1)－N(1) 1.905(2), Co(1)－C(7) 2.024(3), Co(1)－
P(2) 2.1953(11), Co(1) － P(3) 2.2013(11), Co(1) － P(1)
2.2245(12), N(1)－C(7) 1.382(4); N(1)-Co(1)-C(7) 41.05(11),
N(1)-Co(1)-P(2) 136.48(8), C(7)-Co(1)-P(2) 103.34(9), N(1)-
Co(1)-P(3) 102.77(8), C(7)-Co(1)-P(3) 142.76(9), P(2)-Co(1)-P(3)
102.24(4), N(1)-Co(1)-P(1) 108.56(8), C(7)-Co(1)-P(1) 99.86(10),
P(2)-Co(1)-P(1) 100.55(4), P(3)-Co(1)-P(1) 101.54(5).
resonate are recorded at δ 0.82 as a doublet (9H, 2JPH＝
6 Hz) and at δ 0.92 as a broad singlet (18H). In the 31P
NMR spectra, three broad singlets at δ −15.7, −16.0 and
1.1 with the integral ratio of 1∶1∶1 suggest that the
three phosphorus atoms have different chemical envi-
ronments. This is typical for the 31P NMR spectra of the
pentacoordinate cobalt(I) complexes.[22]
This result is verified by X-ray single crystal diffrac-
tion. The molecular structure of 5 is shown in Figure 2.
Complex 5 has a trigonal bipyramid gemometry with
P(1), P(3) and N(1) atoms in the equatorial plane. The
three bond angles in this plane are N(1)-Co(1)-P(3)＝
124.54(9)°, N(1)-Co(1)-P(1)＝109.04(9)° and P(1)-
Co(1)-P(3)＝124.66(4)°. The P(2) and C(6) atoms are
located in the axial positions with a bond angle of
C(6)-Co(1)-P(2)＝177.2(1)°. The distance of C(7)－N(1)
(1.305(4) Å) is remarkably shorter than that of C＝N
(1.382(4) Å) in 4, while π-coordination of the C＝N
group is indicated in complex 4. However, this value is
larger than those (average: 1.286 Å) in the ortho-
metalated cobalt(III) fluoride.[16] The distance of Co(1)
－P(2) [2.2028(8) Å] is longer than that of Co(1)－P(1)
[2.1914(9) Å] and Co(1)－P(3) [2.1917(1) Å] due to the
Under similar reaction conditions, the reaction of
perfluoroaryl imine 2 with Co(PMe3)4 resulted in the
formation of ortho-metalated Co(I) complex 5 as a C－
F bond activation product (Eq. 4).
Complex 5 was isolated as dark brown crystals in the
yield of 50%. Complex 5 is not stable in the air and de-
composes above 88 ℃ under nitrogen. Complex 5 was
characterized by IR and NMR spectroscopy. In the in-
frared spectra of complex 5, the characteristic ν(C＝N)
band was recorded at 1624 cm−1. Compared with the
(C＝N) band (1647 cm−1) of free ligand 2, this substan-
tial red shift upon coordination of the N-donor atom of
the imine group indicates a weakening of the C＝N
double bond after coordination to the cobalt centre. In
1
the H NMR spectra, the CH proton of the imine group
appears at δ 9.28 as a singlet while three PMe3 protons
Chin. J. Chem. 2013, 31, 927—932
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Lu, Sun & Li
FULL PAPER
Scheme 1 Proposed formation mechanism of 5
F
F
Cl
N
Cl
F
F
n-pentane
F
F
N
2
Co(PMe3)4
2
PMe3
2
F
+
+
PMe3
PMe3
F2PMe3
Co
F
Me3P
F
2
5
2
PMe3
3 PMe3
F2PMe3
+
F
F
F
Cl
F
F
F
F
2PMe3
2
N
2
F
N
Cl
PMe3
PMe3
F
Co
Co
PMe3
F
Me3P
Me3P
B
trans-influence of the phenyl-C(6) atom.
A possible formation mechanism of complex 5 is
suggested in Scheme 1. The first step is the π-coordina-
tion of the imine group to the cobalt(0) center after dis-
sociation of one phosphine ligand to give rise to inter-
mediate A. With the chelate effect C－F bond is cleav-
aged by ortho-metalation to afford intermediate B, an
organocobalt(II) fluoride via oxidative addition. The
redox reaction of B with PMe3 results in the formation
of the end product 5 and difluorotrimethylphosphorane
(F2PMe3). The formation of F2PMe3 in solution was
verified via 31P NMR and 19F NMR.[15] Similar reaction
mechanism was reported in our early work on the reac-
tion of Co(PMe3)4 with perfluorinated toluene.[15]
In order to verify this mechanism, the following ex-
periment was designed. To catch intermediate organo-
cobalt(II) fluoride B, ligand 3 was introduced because 3
is more electron-rich than 2 due to the lack of one chlo-
rine atom on the phenyl ring. Ligand 3 and Co(PMe3)4
were combined in pentane (Eq. 5). This mixture was
stirred under ambient temperature for 24 h. After work-
up, an organocobalt(II) fluoride, complex 6, was suc-
cessfully isolated as dark brown crystal from the pen-
tane solution in the yield of 41%. This is the first exam-
ple of cobalt(II) complex containing a [C-Co-F] frag-
ment. Complex 6 is paramagnetic and was characterized
by X-ray single crystal diffraction.
Figure 3 Molecular structure of 6. (all the hydrogen atoms were
omitted for clarity) Selected bond distances (Å) and angles (°):
Co(1)－F(1) 1.9143(11), Co(1)－N(1) 2.1396(15), Co(1)－P(1)
2.2151(6), Co(1)－P(2) 2.2291(6), Co(1)－C(1) 1.9087(18), C(7)
－N(1) 1.297(2); C(1)-Co(1)-F(1) 169.85(6), C(1)-Co(1)-N(1)
81.56(7), F(1)-Co(1)-N(1) 108.09(5), C(1)-Co(1)-P(1) 91.27(6),
F(1)-Co(1)-P(1) 84.69(4), N(1)-Co(1)-P(1) 96.08(4), C(1)-Co(1)-
P(2) 90.75(6), F(1)-Co(1)-P(2) 91.32(4), N(1)-Co(1)-P(2)
95.99(4), P(1)-Co(1)-P(2) 167.93(2).
The molecular structure of 6 is shown in Figure 3.
The cobalt atom attains a penta-coordinate tetragonal
pyramid with the imine-N(1) atom at the apical position.
The distance of C(7)－N(1) (1.297(2) Å) in 6 is compa-
rable with that in complex 5 (1.305(4) Å)). The Co－F
bond length (Co(1)－F(1)＝1.914(1) Å) in complex 6 is
obviously shorter than those (1.926－1.941 Å) in the
organocobalt(III) fluorides (with a [C-Co-F] frag-
ment).[14,16] The Co－C bond lengths in both complex 6
[Co－C(1)＝1.9087(18) Å] and complex 5 [Co(1)－C(6)
＝1.940(3) Å] are in the normal region.
The completely different products of reactions 4 and
5 are entirely caused by the ortho-chlorine atom on the
phenyl ring linked to the imine-N atom. In general, C－
Cl bond is more easily activated than C－F bond, be-
cause the bond energy of the former is smaller than that
of the latter. However, the C－F bonds of a perfluoro-
phenyl ring are remarkably activated because the elec-
tron-withdrawing effect of the fluorine atoms. The
F
F
F
N
n-pentane
Co(PMe3)4
+
F2PMe3
F
F
3
F
F
F
N
(5)
PMe3
Co
F
F
Me3P
6
930
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Chin. J. Chem. 2013, 31, 927—932

Cobalt-catalyzed Selective C－F Bond Activation and Alkylation of Polyfluoroaryl Imines
similar selectivity on C－F bond activation with plati-
num was also reported by Crespo.[23] In addition, chela-
tion is also beneficial to the formation of complex 6 and
the imine group acts as an anchoring group for this
ortho-metalation.
The reaction of CoMe(PMe3)4 with 2,6-difluoro-
benzophenone imine afforded the imine cobalt(I) com-
plex via C－H bond activation, while the combination
of Co(PMe3)4 with the same imine delivered another
imine cobalt(I) complex via C－F bond activation.[17]
The imine cobalt(I) and cobalt(III) chlorides were ob-
tained through the reaction of ortho-chlorinated phenyl
imine with electron-rich cobalt(I) complexes supported
by trimethylphosphine ligands.[24]
Table 2 Optimization of conditions for catalytic dimethylation
Reaction
temp./℃
Reaction
time/h
Compound 7
yielda/%
Entry
Solvent
1
toluene
DMF
50
50
50
50
50
50
30
30
30
30
30
30
30
30
24
24
24
24
24
24
24
24
24
24
12
8
95
5
2
3
DMSO
dioxane
THF
95
97
95
99
64
70
95
99
96
95
35
0
4
5
6
DME
7
toluene
DMSO
dioxane
DME
8
9
10
11
12
13
Catalyitc alkylation of fluorinated benzalimine with
zinc reagents by Co(PMe3)4
DME
DME
Kumada reported the first example of catalytic C－C
bond cross-coupling of fluorobenzene with Grignard re-
agents by nickel catalysts.[25] Crespo and Martinez pub-
lished that [Me2Pt(µ-SMe2)]2 could be used in the
stoichiometric C－F activation.[23] Love disclosed the
first example of Pt-catalyzed methylation and methoxyla-
tion of a variety of polyfluoroaryl imines through the
mono-substitution reaction.[26] Nickel-catalyzed C,C-
coupling reaction of aryl fluorides via C－F bond activa-
tion was studied by Chatani and his co-workers.[27] The
nickel complexes Ni(PMe3)4 and NiMe2(PMe3)3 sup-
ported by trimethyphosphine were also used to explore
C,C-coupling reactions via C－F bond activation.[28]
Inspired by those results, we studied the catalytic
C,C-coupling reaction of compound 3 and dimethyl zinc
with Co(PMe3)4 as catalyst (Eq. 6). Bis-dimethylated
product 7 was formed in excellent yields (Table 2).
DME
4
14b
DME
8
a
Yield based on in situ 19F NMR spectra and is the average of 2
times. b Blank experiment.
F
Co(PMe3)4
10 mol%
F
F
N
ZnRX
3
+
F
F
R
F
F
F
N
(7)
R
Table 3 Co-catalyzed dimethylation with other organozinc
reagents
F
Co(PMe )
10 mol%
3 4
F
F
N
1.5
ZnMe2
+
Reaction
time/h
Reaction
temp./℃
Entry Organozinc
Solvent
Yielda%
F
F
3
1
2
3
4
5
6
7
8
ZnBnCl
ZnBnCl
ZnBnCl
ZnBnCl
ZnBnCl
ZnBnCl
ZnBnCl
ZnPhBr
ZnCyCl
8
DME
30
50
60
80
80
80
3
Me
F
8
DME
14
52
75
35
33
83
16
22
F
F
N
(6)
24
8
toluene
toluene
DMF
Me
8
7
8
DMSO
Comparing the results of Entry 1 to 10, it is con-
8
dioxane 80
cluded that DME is the best solvent and 30 ℃ is the
best reaction temperature. From the results of Entry 11
to 13, it can be drawn that 8 h is enough for the reaction.
Entry 14 is a control experiment.
24
toluene
70
9
24
DME
50
Yield based on in situ 19F NMR spectra and is average of 2
a
To expand this catalytic system, other organozinc
compounds (ZnBnCl, ZnPhBr and ZnCyCl) as alkylat-
ing reagents were also studied (Eq. 7). However, the
reactivity of these three organozinc reagents is weaker
than that of dimethylzinc. At the higher temperatures the
C,C-coupling products could be obtained in different
yields (Table 3).
times.
Conclusions
In conclusion, we have taken a step forward in selec-
tive C－F bond activation of polyfluorinated imines by
cobalt(0) complex supported by trimethylphosphine
Chin. J. Chem. 2013, 31, 927—932
© 2013 SIOC, CAS, Shanghai, & WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.cjc.wiley-vch.de
931

Lu, Sun & Li
FULL PAPER
23, 6140.
ligands. For the first time, an ortho-chelated covalent
cobalt(II) complex containing a [C－Co－F] fragment
was isolated and structurally characterized by X-ray
diffraction. The catalytic ortho-dialkylation of per-
fluoroaryl imine with organozinc reagents involving
selective C－F bond activation via C,C-coupling reac-
tion was studied with Co(PMe3)4 as catalyst under mild
conditions. This work is of importance for cobalt-cata-
lyzed C－F bond activation and functionalization of
organic fluorides.
[9] Park, S.; Pontier-Johnson, M.; Roundhill, D. M. J. Am. Chem. Soc.
1989, 111, 3101.
[10] Edelbach, B. L.; Jones, W. D. J. Am. Chem. Soc. 1997, 119, 7734.
[11] Johnson, S. A.; Hatnean, J. A.; Doster, M. E. Prog. Inorg. Chem.
2011, 255.
[12] Sun, A. D.; Love, J. A. Dalton Trans. 2010, 39, 10362.
[13] Camadanli, S.; Beck, R.; Flörke, U.; Klein, H.-F. Dalton Trans. 2008,
5701.
[14] Li, X.; Sun, H.; Yu, F.; Floerke, U.; Klein, H.-F. Organometallics
2006, 25, 4695.
[15] Zheng, T.; Sun, H.; Chen, Y.; Li, X.; Duerr, S.; Radius, U.; Harms,
K. Organometallics 2009, 28, 5771.
[16] Lian, Z.; Xu, X.; Sun, H.; Chen, Y.; Zheng, T.; Li, X. Dalton Trans.
2010, 39, 9523.
[17] Zheng, T.; Sun, H.; Ding, J.; Zhang, Y.; Li, X. J. Organomet. Chem.
2010, 695, 1873.
[18] Li, J.; Zheng, T.; Sun, H.; Xu, W.; Li, X. Dalton Trans. 2013, 42,
5740.
[19] Hao, L.; Fettinger, J. C.; Power, P. P. Inorg. Chem. 2012, 51, 1821.
[20] Klein, H.-F.; Karsch, H. H. Chem. Ber. 1975, 108, 944.
[21] Klein, H.-F.; Karsch, H. H. Inorg. Chem. 1975, 14, 473.
[22] Li, X.; Sun, H.; Klein, H.-F.; Flörke, U. Z. Anorg. Allg. Chem. 2005,
631, 1929.
[23] Crespo, M.; Martinez, M.; Sales, J. Organometallics 1993, 12, 4297.
[24] Chen, Y.; Sun, H.; Flörke, U.; Li, X. Organometallics 2008, 27, 270.
[25] Kiso, Y.; Tamao, K.; Kumada, M. J. Organomet. Chem. 1973, 50,
C12.
[26] Wang, T.; Alfonso, B. J.; Love, J. A. Org. Lett. 2007, 9, 5629.
[27] Shimasaki, T.; Konno, Y.; Tobisu, M.; Chatani, N. Org. Lett. 2009,
11, 4890.
[28] Yang, X.; Sun, H.; Zhang, S.; Li, X. J. Organomet. Chem. 2013, 723,
36.
Acknowledgement
We gratefully acknowledge the support by National
Natural Science Foundation of China (No. 21172132).
We also thank the kind assistance from Prof. Dieter
Fenske and Dr. Olaf Fuhr (Karlsruhe Nano-Micro Facil-
ity, KNMF) for the X-ray diffraction analysis.
References
[1] Kiplinger, J. L.; Richmond, T. G.; Osterberg, C. E. Chem. Rev. 1994,
94, 373.
[2] Crespo, M. Organometallics 1995, 14, 355.
[3] Torrens, H. Coord. Chem. Rev. 2005, 249, 1957.
[4] Amii, H.; Uneyama, K. Chem. Rev. 2009, 109, 2119.
[5] Klahn, M.; Rosenthal, U. Oganometallics 2012, 31, 1235.
[6] Johns, K.; Stead, G. J. Fluor. Chem. 2000, 104, 5.
[7] Braun, T.; Perutz, R. N. Chem. Commun. 2002, 23, 2749.
[8] Jasim, N. A.; Perutz, R. N.; Whitwood, A. C.; Braun, T.; Izundu, J.;
Neumann, B.; Rothfeld, S.; Stammler, H. G. Organometallics 2004,
(Cheng, F.)
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Chin. J. Chem. 2013, 31, 927—932