Cobalt-Catalyzed Regioselective Borylation of Arenes: N-Heterocyclic Silylene as an Electron Donor in the Metal-Mediated Activation of C?H Bonds

Article abstract of DOI:10.1002/chem.201605937

C?H Borylation of arenes has been a subject of great interest recently because of its atom-economy and the wide applicability of borylated products in value-added synthesis. A new bis(silylene)cobalt(II) complex bearing a bis(N-heterocyclic silylene)-pyridine pincer ligand (SiNSi) has been synthesized and structurally characterized. It enabled the regioselective catalytic C?H borylation of pyridines, furans, and fluorinated arenes. Notably, it exhibited complementary regioselectivity for the borylation of fluorinated arenes compared to previously known catalytic systems, demonstrating that N-heterocyclic silylene donors have enormous potential in metal-catalyzed catalytic applications.

Full text of DOI:10.1002/chem.201605937

A Journal of
Accepted Article
Title: Cobalt-Catalyzed Regioselective Borylation of Arenes: N-
Heterocyclic Silylene as Electron Donors in Metal-Mediated
Activation of CꢀH Bonds
Authors: Chunming Cui, Hailong Ren, Yu-Peng Zhou, Yun-Ping Bai,
and Matthias Driess
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Chem. Eur. J. 10.1002/chem.201605937
Link to VoR: http://dx.doi.org/10.1002/chem.201605937
Supported by

10.1002/chem.201605937
Chemistry - A European Journal
COMMUNICATION
Cobalt-Catalyzed Regioselective Borylation of Arenes: N-
Heterocyclic Silylene as Electron Donors in Metal-Mediated
Activation of CH Bonds
Hailong Ren,[a] Yu-Peng Zhou,[b] Yunping Bai,[a] Chunming Cui*,[a,c] and Matthias Driess[b]
Abstract: C-H Borylation of arenes has been a subject of great
current interest because of its atom-economy and the wide
applicability of borylated products in value-added synthesis. A new
bis(silylene)cobalt(II) complex bearing a bis(N-heterocyclic silylene)–
pyridine pincer ligand (SiNSi) has been synthesized and structurally
characterized. It enabled the regioselective catalytic C–H borylation
of pyridines, furans and fluorinated arenes. Notably, it exhibited the
complementary regioselectivity for the borylation of fluorinated
arenes compared to previously known catalytic systems,
demonstrating that N-heterocyclic silylene donors have enormous
potential in metal-catalyzed catalytic applications.
mediated by rhodium and iridium-NHSi complexes with the
ligand II (Chart 1) complexes has been reported by Driess and
co-workers.[18] The latter group has recently developed new
pincer-type ligands with two NHSi arms such as III and IV, which
have been successfully employed for the preparation of Ir, Co,
Ni and Fe complexes.[19-21] Interestingly, the Ir complexes
enabled catalytic CH borylation of arenes. These results
demonstrated that NHSis can act as very useful electron-donors
in metal-mediated catalytic transformations and current studies
are aiming at widen the scope of applications of such ligands in
catalysis.
Encouraged by the advances of NHSi ligands and cobalt-
mediated catalysis, we became interested in the investigation of
cobalt complexes supported by the pyridine-based pincer ligand
IV modified with two NHSi donor arms (SiNSi, Chart 1) and its
catalytic ability. Herein, we report the synthesis of the CoBr2
complex 1 supported by the SiNSi pincer ligand IV (Chart 1) and
its application in catalytic C-H borylation of arenes. Notably, this
system enabled highly regioselective borylation of fluorinated
arenes distinct from the known cobalt PNP system.
Selective C–H functionalization of organic compounds is an
important and long–standing goal in synthetic chemistry.[1]
A
vast number of C–H functionalization reactions are currently
available, whereas C–H borylation is often preferred due to the
versatility of the organoboron compounds in synthesis.[2-3] In
comparison to the precious–metal based catalysts such as Rh,
Pt and Ir,[2,4-6] cheap and nontoxic metals are of great current
interest. Recently, iron-, nickel-, cobalt- and copper-based
catalysis for C–H borylation have been developed.[7-9] In this
context, cobalt pincer complexes have attracted a great deal
attention.[10-13] Remarkably, CH borylation of arenes has
recently been reported by Chirik et al. using PNP cobalt pincer
complexes.[13] However, cheap metal-catalyzed CH borylation
is still in its infancy, and the selective metal catalysts are still
highly desirable.
But
But
tBu
Et
N
Et
N
But
But
But
But
N
N
N
N
N
O
N
O
Si
Si
N
N
N
N
Si
Si
Si
N
Si
Ph
Ph
Ph
Ph
N
tBu
N
But
But
But
But
IV
I
II
III
To modulate the reactivity and selectivity of metal catalysts,
the electron donors on suitable ligand frameworks play important
roles. While -donors based on phosphines and N-heterocyclic
carbenes have been extensively studied. Recent surge in the
development of silylene chemistry has shown that silylenes,
isoelectronic with singlet carbenes, are potential -donors for
catalysis. Although a large number of stable silylenes could be
isolated and their coordination ability toward transition-metals
has been studied as well,[14,15] the application of silylenes in
catalysis remains largely unexplored. Nevertheless, Fürstner
and Roesky et al. have shown that palladium the complexes
supported by the NHSi ligand I (Chart 1) were active for Suzuki
and Heck reactions.[16,17] Reduction of amides to amines
Chart 1. N-Heterocyclic silylenes appplied as electron donors in metal-
catalyzed reactions.
Et
Et
N
Et
N
Et
N
N
N
Si
N
tBu
N
N
N
tBu
Ph
0.9 CoBrr
tBu
tBu
Ph
22
N
N
Si
Si
Si
Co
THF, rt, 122 h
N
N
N
Ph
Br
Br
tBu
Ph
tBu
tBu
tBu
IV
1, 79%
Scheme 1. Synthesis of (SiNSi)CoBr2 1.
The cobalt complex (SiNSi)CoBr2 1 was obtained as dark
crystals in 79% yield by the reaction of IV with CoBr2 in THF
(Scheme 1). The structure of the paramagnetic complex 1 has
been elucidated by a single-crystal X–ray diffraction analysis
(Figure 1, Tables S1-S2 in the SI). The SiNSi ligand acts as a
tridentate pincer ligand to cobalt. The N5Co1 bond distance of
2.026(3) Å is short compared to those observed in related
bis(imino)- and bis(phosphino)pyridine cobalt halides (2.051(3)-
2.102(5) Å).[22] The SiCo bond lengths of 2.1949 and 2.2244(11)
Å are close to those found in (LSiCl)2CoBr2 (L = PhC(NtBu)2,
2.1949(5) and 2.1793(5) Å).[23] Magnetic susceptibility
[a]
[b]
[c]
H. Ren, Y. Bai, Prof. C. Cui.
State Key Laboratory of Elemento-Organic Chemistry
Nankai University, Tianjin 300071 (China)
E-mail: cmcui@nankai.edu.cn
Y.-P. Zhou, Prof. M. Driess
Department of Chemistry: Metalorganics and Inorganic Materials
Sekr C2, Strasse des 17. Juni 135, Technische Universiteat Berlin
Berlin 10623, Germany
Prof. C. Cui
Collaborative Innovation Center of Chemical Science and
Engineering (Tianjin), Tianjin 300072, China
Supporting information for this article is given via a link at the end of
the document.((Please delete this text if not appropriate))
This article is protected by copyright. All rights reserved.

10.1002/chem.201605937
Chemistry - A European Journal
COMMUNICATION
measurements of 1 (μeff = 2.12 μB) revealed a low–spin d7-Co
the SI). B2Pin2 cannot be separated in pure form and has been
detected in the mixture by the 11B NMR spectrum (Figure S1). In
contrast, the reaction of cyclohexene with B2Pin2 under the
similar conditions only yielded trace of C6H11BPin and C6H10Bpin.
The results indicated that cyclohexene does not consume B2Pin2
noticeably.
center, comparable with
a bis(carbene)pyridine dibromido
cobalt(II) complex (μeff = 2.00 μB).[24] On the basis of the
previous studies applying the strongly electron-donating
properties of NHSis, we reasoned that 1 could be a potentially
useful precatalyst for the selective CH functionalization which
are otherwise difficult to achieve.
BPin
1
4 mol%%of , 8 mol% of NaBHEt3
+
B2Pin2
1 eq
+
HBPin
4 eq
ccyclohexene (1 eq)
TTHF, 100°C, 24 h
N
N
1 eq
trace
Scheme 3. Borylation of 2,6-lutidine in prresence of excess HBPin.
Next we investigated the CH borylation of various arenes;
we found that 1 can catalyze the borylation of benzene
derivatives with electron-donating groups but only very low
conversions. This indicates the pronounced electronic effects of
the catalytic borylation. We then focussed on heteroarenes such
as pyridines and furans and benzene derivatives with electron-
withdrawing groups.
Figure 1. The ORTEP representation of complex 1 in the solid state. Thermal
ellipsoids are drawn at the 30% probability level. Hydrogen and solvent atoms
are omitted for clarity.
Table 1. Co-catalyzed borylation of N-annd O-heteroarenes.
At first we probed the borylation of 2,6–lutidine 1a with
bis(pinacolato)diboron B2Pin2 as a model reaction (Scheme 2).
The reaction was initially conducted with 4.0 mol% loading of 1
and 8.0 mol% loading of NaBHEt3 (0.1 M in THF) as the
reductant. Although the borylation of 2,6–lutidine with B2Pin2 at
100 C yielded the expected product, the lutidine cannot be
completely converted to the desired borylated product even after
prolonged reaction time (Table S3 in the SI). We reasoned that
the side product HBpin may suppress the CH borylation.
Indeed, upon addition of one equivalent of cyclohexene, the
borylation at 100 C for 24 h led to a complete conversion with
the selective formation of the 4-substituted product 2a (Table S3
in the SI), along with the formation of C6H11BPin and
cyclohexane as the side products. Furthermore, the borylation
reaction in the presence of four molar equivalents of HBPin and
cyclohexene only led to the formation of trace borylated product
2a, and cyclohexene was completely consumed as indicated by
the proton NMR spectroscopy (Scheme 3). These results
indicated that HBpin was generated in the course of borylation
and could be consumed by the addition of cyclohexene.
BPin
BPin
BPin
PinB
5
4
PinB
OMe
O
O
C6H5
N
N
N
BPin
2f
[b]>99 (87%)
2b
2c
2e
2d
[b]100 (85%)
[a]71 (50%)
>98 (77%) >98 (90%)
49:51 (4:5)
Reaction conditions: pyridines (0.5 mmol), B2Pin2 (0.5 mmol) and
cyclohexene (0.5 mmol); furan (0.5 mmmol) and B2Pin2 (0.5 mmol); 2-
methylfuran (0.5 mmol) and B2Pin2 (0.255 mmol), in 0.4 mL THF at 100C for
24 h with precatalyst 1 (4 mol%) and NNaBHEt3 (8 mol%). Reported values
are % conversions with respect to the arenes as determined by 1H NMR
spectroscopy, the ratios of the prooduct were determined by NMR
spectroscopy, and the values in pareentheses are isolated yield. [a]with
precatalyst 1 (8 mol%) and NaBHEt3 (16 mol%); [b] without cyclohexene.
We first investigated the borylation of substituted pyridines
and furans. The results are summarized in Table 1. The
borylation of 2-methoxy–6–methyl pyridine is much slower than
that of lutidine 1a and required 8 mol% loading of precatalyst 1
for an acceptable conversion, selectively yielding the 4-
substituted product in ca 71% yield in 24 h based on NMR
analysis. The borylation of 2,3–lutidine 1c with 4 mol% of 1
selectively borylated the 5-position of the ring (2c), whereas
borylation of 2–benzylpyridine 1d furnished a mixture containing
almost the same amount of 4– and 5–borylated regioisomers 2d.
BPin
1
4 mol%of , 8 mol% of NaBHEt3
B2Pin2
+
cyclohexene (1 eq)
THF, 100°C, 24 h
N
N
1a
2a
(> 98%)
Scheme 2. Borylation of 2,6-lutidine 1a with B2Pin2.
In contrast to the borylation of pyridines, the borylation of
furan did not require cyclohexene. The borylation of furan 1e led
to the bis-borylation of 2- and 5-positions (Scheme 4 and Table
1, 2e) of the ring with one molar equiv of B2Pin2, while 2–
methylfuran 1f selectively occurred at the 5-position with 0.5
molar equiv of B2Pin2 to give 2f. This indicated that the
borylation of furan can be performed with HBPin. Indeed, the
In order to clarify the role of cyclohexene, hydroboration of
cyclohexene with one equivalent of HBPin under the similar
catalytic conditions was conducted. The reaction yielded ca. 19%
C6H11BPin, 23% cyclohexane and ca 29% B2Pin2 as estimated
1
by the GCMS and H NMR spectroscopy (Figures S1 and S2 in
This article is protected by copyright. All rights reserved.

10.1002/chem.201605937
Chemistry - A European Journal
COMMUNICATION
borylation of both furan and 2–methylfuran with HBPin yielded
the expected borylated products in good yields.
combination of the electronic and steric factors afforded by the
[NSiN] donor ligand. However, the deep understanding of these
factors has yet to be investigated.
1
4 mol% 0f , 8 mol% of NaHBEt3
+
B2Pin2
BPin
BPin
Bpin
Bpin
THF, 100 oC, 24 h
O
1e
O
2e
Chart 2. Comparison of 1 with iridium, pplatinum and PNP cobalt precatalysts
for the CH borylation of fluorinated arennes.
1
4 mol% 0f , 8 mol% of NaHBEt3
+
2 HBPin
THF, 100 oC, 24 h
O
O
1e
2e
F
F
F
F
2
F
F
F
2
3
3
4
Scheme 4. Borylation of furan with B2Pin2 and HBPin.
3
4
6
5
5
4
4
5
2:4:5
3:4
2:3:4
5:6
3:4:5
As fluorinated arylboronic esters are highly valuable building
blocks in pharmaceutical and material chemistry,[25] catalytic
borylation of fluoro- and trifluoromethylarenes has been probed
as well. The results are summarized in Table 2. Disubstituted
benzenes with at least one trifluoromethyl substituent undergo
selective borylation at the least hindered positions (Table 2, 2g-
2k), indicating that the selectivity is controlled by steric effects of
the ring. Borylation of 1–methyl–2–(trifluoromethyl)- and 1-
methoxyl-2(trifluoromethyl)benzenes (2j and 2k) led to the
formation of a mixture containing two regioisomers. However,
the regioselectivity for the two substrates was observed to some
extend at the para-position to the CF3 group in the ring. It has
been reported that similar selectivity could be achieved for 2j
and 2k with iridium catalysts.[4d, 6f]
This work
88:12
49:41[d]
24:76
33:67[a]
[PSiN]Pt[e] 91:9
[NHC]Pt[f] 99:1
[PNP]Co[g]
1:2:97
11:75:14
155:55:28[c]
884:13:3
773:20:7
89:11
7:72:21
Ir
17:33:50[b]
78:18:4
82:18
71:16:4:6
[a]
Ref 6c; [b] Ref 6d; [c] Ref 6e; [d] Ref 44d; [e] Ref 5b; [f] Ref 5a; [g] Ref 13a.
Table 2. Catalytic borylation of fluorine-ccontaining arenes and polyarenes.
CF3
Me
F3C
CF3
CF3
Me
CF3
4
PinB
CF3
BPin
PPinB
PinB
5
2g
2h
2i
2j
Borylation of 1,2–difluorobenzene (Table 2, 2l) proceeded
smoothly under the similar reaction conditions to yield the
corresponding 4-borylated product as a major regioisomer
(24:76). Notably, 1,3–difluorobenzene predominantly gave the 5-
borylated product 2m in 97% yield as determined by 19F NMR
spectroscopy. To the best of our knowledge, there has been no
catalyst reported reaching such a high level of regioselectivity for
this substrate. It was shown that iridium–catalyzed borylation of
1,3–difluorobenzene yielded 2-, 4- and 5-positional regioisomers
in the molar ratio of 17:33:50.[6c] Chatani and Iwasawa et al.
reported that the platinum–catalyzed borylation of 1,3–
difluorobenzene occurred preferentially at the 2–position.[5]
Borylation of 2–substituted 1,3–difluorobenzenes proceeded at
the 5–position selectively in good yields (2n and 2o), whereas
1,2,3-trifluorobezene led to a relatively low selectivity at the 5-
position with the contamination of 4-borylated product in ca 22%
yield (2p). Fluorobenzene underwent smooth borylation, yielding
the 3-borylated regioisomer (2q) as the major product with high
efficiency. This regioselectivity is opposite and complementary
to that catalyzed by PNP cobalt pincer complexes.[12a] Similarly,
borylation of 2–methylfluorobenzene preferably occurred at the
4–position (2r) with 2- and 5-borylated products as side products.
1-Fluoro-3-methylbenzene selectively borylated at the meta
position of the fluorine atom (Table 2, 2s), and the borylation of
1-fluoro-3-(trifluoromethyl)benzene yielded the single borylated
product 2t.
100% (94%)
>98% (90%)
>98% (96%)
100 (95%)
43:57 (4:5)
Me
F
CF3
F
F
F
OMe
F
2
5
3
4
PinB
PPinB
F
BPin
4
5
4
BPin
2n
2k
2l
2m
[a]100 (95%)
>98% (91%)
97:2:1 (5:4:2)
>99 (90%)
[b](83%)
32:68 (4:5)
24:76 (3:4)
BPin
F
F
F
F
F
F
F
2
3
3
4
4
BPin
4
BPin
5
5
BPin
BPin
2o
2p
2q
2r
[c]>99 (91%)
[b](70%)
[b](90%)
[b](97%)
22:78 (4:5)
111:75:14 (2:3:4) 7:72:21 (3:4:5)
BPin
F
CF3
F
BPin
PinB
7
6
6
PinB
PinB
5
BPin
2s
2t
2u
2v
[d](78%)
[dd](77%)
(87%)
88:12 (5:6)
(93%)
255:75 (6:7)
Reaction conditions: arenes (0.5 mmol)), B2Pin2 (0.5 mmol) and cyclohexene
(0.5 mmol) in 0.4 mL THF at 100C for 224 h, with precatalyst 1 (4 mol%) and
NaBHEt3 (8 mol%); Reported values arre % conversions with respect to the
arenes as determined by 1H NMR spectroscopy, product ratios were
determined by NMR spectroscopy, and tthe values in parentheses are isolated
It can be seen from Chart 2, this cobalt-catalyzed borylation
of selected fluorinated arenes exhibited good regioselectivity at
the meta-position to the fluorine atom(s). It appeared to be more
yield. [a] 36 h; [b]10 molar equiv of arenees (5 mmol); 2-(2,6-difluorophenyl)-
[c]
6]
regioselective compared to iridium catalysts,[4d,
whereas it
4,4,5,5-tetramethyl-1,3,2-dioxaborolane aas substrate; [d] 8.0 mol% loading of 1
exhibited opposite regioselectivity to platinum and cobalt pincer
precatalysts.[5, 13] This regioselectivity could be attributed to the
and 16 mol% of NaBHEt3, 2 molar equiv of cyclohexene and B2Pin2 for 48 h.
This article is protected by copyright. All rights reserved.

10.1002/chem.201605937
Chemistry - A European Journal
COMMUNICATION
to elucidate the differences of NHSi ligands from phosphine
ligands are ongoing in our laboratories.
The bis-borylation of naphthalene and pyrene was also
examined (Table 2, 2u and 2v). These reactions led to the
isolation of the corresponding products in 77 and 78% yields,
respectively. The borylation of naphthalene yielded the 6- and 7-
borylated products in the molar ratio of 1:3, whereas borylation
of pyrene selectively gave the single product 2v.
Acknowledgements
HR, YPB and CC are grateful to the National Natural Science
Foundation of China (Grant No. 21390401 and 21472098) for
financial support. MD and YPZ thank the Deutsche
Forschungsgemeinschaft (Cluster of Excellence UniCat, ExIn
314/2) for support.
On the basis of the cobalt-catalyzed CH borylation
mechanism previously proposed[13] and our experiment results,
the tentative mechanism for the borylation reaction is outlined in
Scheme 5. It is reasoned that the cobalt(I) hydride A was
generated in situ upon addition of NaHBEt3 to precatalyst 1.
Unfortunately, many attempts to isolate and detect A were
unsuccessful date. The oxidative-addition of B2Pin2 to A could
lead to the intermediate B. Subsequently, the reductive
elimination of HBPin from B yielded the active cobalt (I) boryl
intermediate C. The CH oxidative-addition of an arene to C
followed by the reductive elimination of arylboronate ester
regenerated the cobalt (I) hydride A. In the presence of
cyclohexene, it reacted with the hydride A via coordinate-
insertion to form the intermediate E. Subsequent reductive
elimination yielded cyclohexane and C6H11BPin with the
generation of the cobalt boryl species C and hydride A,
respectively. In the absence of cyclohexene, with the increase of
the amounts of HBPin in the catalytic cycle the reductive
elimination of B to form C could be suppressed, thus the
catalytic cycle was interrupted.
Keywords: silylene • pincer ligand• cobalt • CH borylation •
silicon
References
[1]
Selected recent reviews: a) B. SSu, Z.–C. Cao, Z.–J. Shi, Acc. Chem.
Res. 2015, 48, 886; b) J. Wencel––Delord, F. Glorius, Nat. Chem. 2013,
5, 369; c) M. Miura, T. Satoh, K. HHirano, Bull. Chem. Soc. Jpn. 2014, 87,
751; d) J. Yamaguchi, A. D. Yamaaguchi, K. Itami, Angew. Chem. Int. Ed.
2012, 51, 8960; Angew. Chem. 20012, 124, 9092; e) T. W. Lyons, M. S.
Sanford, Chem. Rev. 2010, 110,, 1147; f) K. M. Engle, T.–S. Mei, M.
Wasa, J.–Q. Yu, Acc. Chem. Rees. 2012, 45, 788; g) F. Kakiuchi, T.
Kochi, S. Murai, Synlett 2014, 255, 2390; h) S. De Sarkar, W. Liu, S. I.
Ko-zhushkov, L. Ackermann, Advv. Synth. Catal. 2014, 356, 1461; i) G.
Rouquet, N. Chatani, Angew. Cheem. Int. Ed. 2013, 52, 11726; Angew.
Chem. 2013, 125, 11942.
[2]
[3]
[4]
a) I. A. I. Mkhalid, J. H. Barnardd, T. B. Marder, J. M. Murphy, J. F.
Hartwig, Chem. Rev. 2010, 110, 8890; b) J. F. Hartwig, Acc. Chem. Res.
2012, 45, 864.
a) D. G. Hall, Boronic Acids; Wileyy–VCH: Weinheim, Germany, 2005; b)
G. R. Dick, E. M. Woerly, M. D. Buurke, Angew. Chem. Int. Ed. 2012, 51,
2667; Angew. Chem. 2012, 124, 22721.
a) H. Chen, S. Schlecht, T. C. SSemple, J. F. Hartwig, Science 2000,
287, 1995; b) J.–Y. Cho, C. N. Ivverson, M. R. Smith, III. J. Am. Chem.
Soc. 2000, 122, 12868; (c) S. Kaawamorita, T. Miyazaki, H. Ohmiya, T.
Iwai, M. Sawamura, J. Am. Chem. Soc. 2011, 133, 19310; d) C. Cheng,
J. F. Hartwig, Science 2014, 343, 853.
[5]
[6]
a) T. Furukawa, M. Tobisu, N. Chhatani, J. Am. Chem. Soc. 2015, 137,
12211; b) J. Takaya, S. Ito, H. Noomoto, N. Saito, N. Kirai, N. Iwasawa,
Chem. Commun. 2015, 51, 176622.
a) M. A. Larsen, J. F. Hartwig, J. Am. Chem. Soc. 2014, 136, 4287; b)
S. M. Preshlock, B. Ghaffari, PP. E. Maligres, S. W. Krska, R. E.
Maleczka, M. R. Smith, III. J. Am. Chem. Soc. 2013, 135, 7572; c) G. A.
Chotana, M. A. Rak, M. R. Smitth, III. J. Am. Chem. Soc. 2005, 127,
10539; d) M. I. Gonzalez, E. D. Bloch, J. A. Mason, S. J. Teat, J. R.
Long, Inorg. Chem. 2015, 54, 29995; e) C. F. Rentzsch, E. Tosh, W. A.
Herrmann, F. E. Kühn, Green CChem. 2009, 11, 1610; f) Y. Saito, Y.
Segawa, K. Itami, J. Am. Chem. SSoc. 2015, 137, 5193; g) H. Tajuddin,
P. Harrisson, B. Bitterlich, J. C. CCollings, N. Sim, A. S. Batsanov, M. S.
Cheung, S. Kawamorita, A. C. Maaxwell, L. Shukla, J. Morris, Z. Lin, T.
B. Marder, P. G. Steel, Chem. Scii. 2012, 3, 3505.
Scheme 5. Proposed mechanism for [SiNSi]Cocatalyzed CH borylation of
arenes.
[7]
a) T. Hatanaka, Y. Ohki, K. Tatsuumi, Chem. Asian J. 2010, 5, 1657; b)
G. Yan, Y. Jiang, C. Kuang, S. Waang, H. Liu, Y. Zhang, J. Wang, Chem.
Commun. 2010, 46, 3170; c) T. DDombray, C. G. Werncke, S. Jiang, M.
Grellier, L. Vendier, S. Bontempss, J.–B. Sortais, S. Sabo–Etienne, C.
Darcel, J. Am. Chem. Soc. 2015, 137, 4062.
In summary, we reported the synthesis of the first bis(NHSi)
pyridine cobalt complex. This well-defined complex enabled the
facile and regioselective C–H borylation of fluorinated benzenes
in high yields. In particular, the observed distinct regioselectivity
from the known [PNP] cobalt catalyst suggested that NHSi
ligands can be complementary to phosphine ligands and thus
very promising for a wide scope of applications. Further studies
[8]
[9]
a) T. Furukawa, M. Tobisu, N. Chatani, Chem. Commun. 2015, 51,
6508; b) H. Zhang, S. Hagihara, KK. Itami, Chem. Lett. 2015, 44, 779.
T. J. Mazzacano, N. P. Mankad, JJ. Am. Chem. Soc. 2013, 135, 17258.
[10] a) G. Zhang, K. V. Vasudevan, B.. L. Scott, S. K. Hanson, J. Am. Chem.
Soc. 2013, 135, 8668; b) G. Zhanng, B. L. Scott, S. K. Hanson, Angew.
Chem. Int. Ed. 2012, 51, 12102; AAngew. Chem. 2012, 124, 12268.
This article is protected by copyright. All rights reserved.

10.1002/chem.201605937
Chemistry - A European Journal
COMMUNICATION
[11] L. Zhang, Z. Zuo, X. Leng, Z. Huang, Angew. Chem. Int. Ed. 2014, 53,
2696; Angew. Chem. 2012, 126, 2734.
[12] a) S. Monfette, Z. R. Turner, S. P. Semproni, P. J. Chirik, J. Am. Chem.
Soc. 2012, 134, 4561; b) C. C. H. Atienza, T. Diao, K. J. Weller, S. A.
Nye, K. M. Lewis, J. G. P. Delis, J. L. Boyer, A. K. Roy, P. J. Chirik, J.
Am. Chem. Soc. 2014, 136, 12108; c) M. R. Friedfeld, M. Shevlin, G. W.
Margulieux, L–C. Campeau, P. J. Chirik, J. Am. Chem. Soc. 2016, 138,
3314.
[13] a) J. V. Obligacion, S. P. Sempromi, P. J. Chirik, J. Am. Chem. Soc.
2014, 136, 4133; b) J. V. Obligacion, S. P. Sempromi, I. Pappas, P. J.
Chirik, J. Am. Chem. Soc. 2016, 138, 10645; c) B. A. Schaefer, G. W.
Margulieux, B. L. Small, P. J. Chirik, Organometallics 2015, 34, 1307.
[14] M. Denk, R. Lennon, R. Hayashi, R. West, A. V. Belyakov, H. P. Verne,
A. Haaland, M. Wagner, N. Metzler, J. Am. Chem.Soc. 1994, 116, 2691.
[15] For reviews see: a) B. Blom, M. Stoelzel, M. Driess, Chem. Eur. J.
2013, 19, 40; b) B. Blom, D. Gallego, M. Driess, Inorg. Chem. Front.
2014, 1, 134; c) S. Raoufmoghaddam, Y.-P. Zhou. Y. Wang, M. Driess,
J. Organomet. Chem. 2016, DOI: 10.1016/j.jorganchem.2016.07.014
[16] A. Fürstner, H. Krause, C. W. Lehmann, Chem. Commun. 2001, 2372.
[17] M. Zhang, X. Liu, C. Shi, C. Ren, Y. Ding, H. W. Roesky, Z. Anorg. Allg.
Chem. 2008, 634, 1755.
[18] M. Stoelzel, C. Präsang, B. Blom, M. Driess, Aust. J. Chem. 2013, 66,
1163.
[19] (a) A. Brück, D. Gallego, W. Wang, E. Irran, M. Driess, J. F. Hartwig,
Angew. Chem., Int. Ed. 2012, 51, 11478; Angew. Chem. 2012, 124,
11645; b) W. Wang, S. Inoue, S. Enthaler, M. Driess, Angew. Chem.,
Int. Ed. 2012, 51, 6167; Angew. Chem. 2012, 124, 6271.
[20] D. Gallego, A. Brück, E. Irran, F. Meier, M. Kaupp, M. Driess, J. F.
Hartwig, J. Am. Chem. Soc. 2013, 135, 15617.
[21] D. Gallego, S. Inoue, B. Blom, M. Driess, Organometallics 2014, 33,
6885.
[22] a) G. J. P. Britovsek, M. Bruce, V. C. Gibson, B. S. Kimberley, P. J.
Maddox, S. Mastroianni, S. J. McTavish, C. Redshaw, G. A. Solan, S.
Strömberg, A. J. P. White, D. J. Williams, J. Am. Chem. Soc. 1999, 121,
8728; b) P. Barbaro, C. Bianchini, G. Giambastiani, I. G. Rios, A. Meli,
W. Oberhauser, A. Segarra, L. Sorace, A. Toti, Organometallics 2007,
26, 4639; c) G. Müller, M. Klinga, M. Leskelä, B. Rieger, Z. Anorg. Allg.
Chem. 2002, 628, 2839.
[23] R. Azhakar, R. S. Ghadwal, H. W. Roesky, J. Hey, L. Krause, D. Stalke,
Dalton Trans. 2013, 42, 10277.
[24] A. A. Danopoulos, J. A. Wright, W. B. Motherwell, S. Ellwood,
Organometallics 2004, 23, 4807.
[25] a) W. K. Hagmann, J. Med. Chem. 2008, 51, 4359; b) P. Jescjke,
ChemBioChem. 2004, 5, 570.
This article is protected by copyright. All rights reserved.

10.1002/chem.201605937
Chemistry - A European Journal
COMMUNICATION
COMMUNICATION
Silylene in C-H Borylation. A
new SiNSi cobalt pincer
complex with two N-
H. Ren, Y.-P. Zhou, Y. Bai, C. Cui,* and
M. Driess
heterocyclic silylene (NHSi)
arms enabled the direct and
facile C-H borylation of
heteroarenes and fluorinated
arenes with complementary
regioselectivity compared to
previously reported transition-
metal-based catalysts.
Page No. – Page No.
Cobalt-Catalyzed Regioselective
Borylation of Arenes: N-Heterocyclic
Silylene as Electron Donors in Metal-
Mediated Activation of CH Bonds
This article is protected by copyright. All rights reserved.