A Bis(silylene)-Substituted ortho-Carborane as a Superior Ligand in the Nickel-Catalyzed Amination of Arenes

Article abstract of DOI:10.1002/anie.201606979

The synthesis and structure of the first 1,2-bis(NHSi)-substituted ortho-carborane [(LSi:)C]₂B₁₀H₁₀(termed SiCCSi) is reported (NHSi=N-heterocyclic silylene; L=PhC(NtBu)₂). Its suitability to serve as a reliable bis(silylene) chelating ligand for transition metals is demonstrated by the formation of [SiCCSi]NiBr₂and [SiCCSi]Ni(CO)₂complexes. The CO stretching vibration modes of the latter indicate that the Si^IIatoms in the SiCCSi ligand are even stronger σ donors than the P^IIIatoms in phosphines and C^IIatoms in N-heterocyclic carbene (NHC) ligands. Moreover, the strong donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr₂to act as an outstanding precatalyst (0.5 mol % loading) in the catalytic aminations of arenes, surpassing the activity of previously known molecular Ni-based precatalysts (1–10 mol %).

Full text of DOI:10.1002/anie.201606979

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International Edition: DOI: 10.1002/anie.201606979
German Edition: DOI: 10.1002/ange.201606979
Homogeneous Catalysis
A Bis(silylene)-Substituted ortho-Carborane as a Superior Ligand in
the Nickel-Catalyzed Amination of Arenes
Yu-Peng Zhou+, Saeed Raoufmoghaddam+, Tibor Szilvꢀsi, and Matthias Driess*
Dedicated to Professor Herbert W. Roesky
Abstract: The synthesis and structure of the first 1,2-bis-
(NHSi)-substituted ortho-carborane [(LSi:)C]2B10H10 (termed
SiCCSi) is reported (NHSi = N-heterocyclic silylene; L =
PhC(NtBu)2). Its suitability to serve as a reliable bis(silylene)
chelating ligand for transition metals is demostrated by the
formation of [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 complexes.
The CO stretching vibration modes of the latter indicate that
the SiII atoms in the SiCCSi ligand are even stronger s donors
than the PIII atoms in phosphines and CII atoms in N-
heterocyclic carbene (NHC) ligands. Moreover, the strong
donor character of the [SiCCSi] ligand enables [SiCCSi]NiBr2
to act as an outstanding precatalyst (0.5 mol% loading) in the
catalytic aminations of arenes, surpassing the activity of
previously known molecular Ni-based precatalysts (1–
10 mol%).
N
-Heterocyclic silylenes (NHSis),[1] the silicon analogues of
N-heterocyclic carbenes (NHCs), are no longer laboratory
curiosities but valuable building blocks for the synthesis of
new functional silicon compounds[2] that are accessible in
multigram quantities; they can even serve as very effective
s donor ligands for transition metals (TMs).[3] In fact, the
electronic nature of NHSi ligands, with a singlet electronic
ground state akin to NHCs, leads to a strong s-donor and p-
acceptor character of the divalent Si center toward TM sites.
Experimental data indicate that the s-donor strengths of
NHSi ligands can be greatly varied by modifying the nature of
the heterocyclic backbone around the divalent Si atom,[3a] and
DFT calculations indicate that they can compete with or even
exceed the electronic features of commonly used NHCs or
phosphine ligands with respect to s-donor and p-acceptor
strengths, ligand-to-metal charge transfer, and steric param-
eters.[4] Therefore, NHSis are attractive steering ligands in
homogeneous catalysis.[5] Currently, the chelating bis-
(silylene) ligands A and D, and the SiXSi pincer-type NHSi
Scheme 1. Multidentate NHSi ligands.
ligands B (X = CH) and C (X = N) have been synthesized in
our laboratory (Scheme 1).[6] TM complexes of the latter type
of ligands can act as very active precatalysts in the borylation
of benzenes,[7a] Sonogashira coupling,[7b] Kumada–Corriu
coupling,[7c] the cyclotrimerization of alkynes, the co-cyclo-
trimerization of alkynes and organocyanides to form pyridi-
nes,[7d] the hydrosilylation of ketones,[7e–g] and the reduction of
amides to amines.[7h] However, compared to the rich struc-
tural diversity of phosphine and NHC ligands, multidentate
NHSi ligands are still scarce. Herein we report the synthesis of
the first bis(NHSi) ligand (termed SiCCSi; Scheme 1) with an
ortho-carborane backbone,[8] and its superior function in the
Ni-catalyzed amination of arenes (Buchwald–Hartwig cou-
pling reactions).
SiCCSi was synthesized and isolated in 84% yield through
a salt metathesis reaction of (LiC)2B10H10 with N,N’-di-tert-
butyl(phenylamidinato)chlorosilylene (Scheme 2). Single-
crystal X-ray diffraction analysis of SiCCSi revealed that
the SiII atoms of the NHSi motifs pointed towards each other
[*] Y.-P. Zhou,[+] Dr. S. Raoufmoghaddam,[+] Prof. Dr. M. Driess
Technische Universitꢀt Berlin, Department of Chemistry:
Metalorganics and Inorganic Materials, Sekr. C2
Strasse des 17. Juni 135, 10623 Berlin (Germany)
E-mail: matthias.driess@tu-berlin.de
ꢀ
with an Si Si distance of 3.267 ꢀ to form a pre-organized
chelating “pocket” for metal coordination (Figure 1, top).
This allows SiCCSi to serve as a reliably strong chelating SiII
ligand for NiII, affording [SiCCSi]NiBr2 after reacting with
L2NiBr2 (L2 = 1,2-dimetheoxyethane). The 29Si NMR signal at
d = 58.7 ppm is drastically downfield shifted compared to the
“free” ligands (d = 18.9 ppm) and other known NHSi-NiII
complexes.[6,7a,b] Single-crystal X-ray analysis of [SiCCSi]-
NiBr2 revealed that the NiII center is, as expected, in a square-
Dr. T. Szilvꢁsi
Department of Inorganic and Analytical Chemistry
Budapest University of Technology and Economics
Szent Gellꢂrt tꢂr 4, 1111 Budapest (Hungary)
[+] These authors contributed equally to this work.
Supporting information and the ORCID identification number(s) for
the author(s) of this article can be found under http://dx.doi.org/10.
1002/anie.201606979.
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around the Ni0 center (see Figures S14 and S14A in the
Supporting Information). The IR stretching vibration fre-
quencies of the CO groups in [SiCCSi]Ni(CO)2 were observed
at n = 1982 and 1934 cmꢀ1 . These observed frequencies are
red-shifted compared to [LSi:(CH2)NHCNi(CO)2] (n = 1952,
1887 cmꢀ1)[7c] and [(NHCCy)2Ni(CO)2] (n = 1949, 1878 cmꢀ1
Cy = cyclohexyl)[8b]
but blue-shifted compared to
{[(R2PC)2B10H10]Ni(CO)2} (R = Ph: n = 2021 and 1966 cmꢀ1
;
;
R = Et: n = 2013 and 1955 cmꢀ1),[8c] and [(NHCMes)2Ni(CO)2]
(n = 2051, 1887 cmꢀ1; Mes = 2,4,6-Me3C6H2).[8b] This suggests
that the s-donor strength of SiCCSi can be larger than that of
NHC or phosphine ligands and even exceeds that of the
[SiFcSi] ligand D in [SiFcSi]NiBr2, which was synthesized and
structurally characterized as well (see Figure S15 and
Table S6 in the Supporting Information). DFT calculations
ꢀ
showed elongation of the Ni Si distances in [SiFcSi]NiBr2 vs.
[SiCCSi]NiBr2, which indicates weaker donor ability of the
SiFcSi ligand towards Ni.[4] The calculated charge of the Ni
center is + 0.72 in [SiCCSi]NiBr2 and + 0.78 in [SiFcSi]NiBr2
(see the Supporting Information). We also calculated the Si-
Ni-Si angle. The somewhat smaller bite angle of [SiCCSi]-
NiBr2 (89.338) vs. [SiFcSi]NiBr2 (91.018) might also predict
increased catalytic activity in the oxidative addition step,
which has been suggested for phosphines before.[9]
Scheme 2. Synthesis of the [SiCCSi]NiBr2 and [SiCCSi]Ni(CO)2 com-
plexes.
Both complexes were successfully applied in Ni-mediated
Buchwald–Hartwig amination reactions of arenes. The orig-
ꢀ
inal reports on this important C N bond-formation reaction
were based on molecular palladium precatalysts.[10] Since
then, however, reports utilizing first-row TM complexes have
appeared.[11] Among these, either structurally defined Ni
complexes or the combination of NiII salts with different
ligands such as phosphines, NHCs, and various nitrogen-
donor-based ligands have been shown to act as suitable
precatalysts in amination reactions.[12,13] Herein, we show that
applying the stronger SiCCSi donor ligand leads to the most
active Ni precatalyst reported to date.
Our initial screening experiments revealed that just
0.5 mol% loading of [SiCCSi]NiBr2 can effectively catalyze
the reaction of phenyl chloride 1 with morpholine 2 in high
yield (93%) after 25 h at 1008C in the presence of catalytic
amounts of AgBPh4 and 1.2 molar equivalents of KOtBu as
a base (Scheme 3). In contrast, using Ni(dme)Br2 as a pre-
catalyst leads to moderate yields of 3a (24%; Table S9,
Entry 1 in the Supporting Information). Moreover, poisoning
studies and control experiments showed that the reaction is
Figure 1. Molecular structure of SiCCSi (top) and [SiCCSi]NiBr2
(bottom). Thermal ellipsoids are set at 50% probability. Hydrogen
atoms and solvent molecules are omitted for clarity.
mediated by
a
molecular nickel catalyst (Table S9,
Entries 18–19). Since the [SiFcSi]NiBr2 precatalyst resulted
in lower yields of 3a (78%; Scheme 3), we reason that the
higher activity of [SiCCSi]NiBr2 is due to the stronger donor
character of SiCCSi towards NiII, which facilitates the
oxidative addition step at the Ni site. For comparison of the
catalytic performance of [SiCCSi]NiBr2 with that of related
NiII complexes containing the bis(diphenylphosphine)-[14] and
ꢀ
planar environment (Figure 1, bottom). The Ni(1) Si(1)
ꢀ
(2.1378(5) ꢀ) and Ni(1) Si(2) (2.1447(5) ꢀ) distances are
shorter than those in NHSi-NiII complexes supported by
pincer-type
B
(2.1737(7) ꢀ)[7b] and related NHC-NHSi
ligands.[7c]
Reduction of [SiCCSi]NiBr2 with KC8 in the presence of
CO furnished the corresponding Ni0 complex [SiCCSi]Ni-
(CO)2. Its 29Si NMR signal appears at d = 86.0 ppm, which is,
in turn, significantly downfield shifted compared to [SiCCSi]-
NiBr2, thus indicating strong p-acceptor character for the CO
ligands. Single-crystal X-ray diffraction data for [SiCCSi]Ni-
(CO)2 and DFT calculations confirm tetrahedral geometry
bis-(cyclodiaminophosphine)-substituted
o-carborane
ligands, the [(NP)CC(NP)]NiBr2 and [(PhP)CC(PPh)]NiBr2
complexes were synthesized, fully characterized, and tested in
the catalytic amination of 1 with 2 under identical reaction
conditions (Scheme 3). This revealed that both phosphine
complexes catalyze the formation of 3a in considerably lower
2
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Table 1, Entries 1–2, 6–7). These results show that the
reaction rate depends on the electronic nature of the
substrates applied in the reaction. Since aryl substrates with
substituents at the para position gave higher yields compared
to those with substituents in the meta and ortho positions (in
the order 4-Me > 3-Me > 2-Me; Table 1, Entries 2, 8–9), steric
effects play a role as well.
The remarkable catalytic performance of [SiCCSi]NiBr2
was further demonstrated using various amines with different
steric and electronic properties (Scheme 4). It was found that
the amination of phenyl chloride results in moderate to
Scheme 3. Catalytic performance of different chelating bis(NHSi) and
bis(phosphine) nickel precatalysts in the Buchwald–Hartwig coupling
of phenyl chloride 1 with morpholine 2 to give 3a.
yields (66 and 63%, respectively; for details see
Tables S9,S10) than [SiCCSi]NiBr2 (93%).
Next, we studied the effect of different leaving groups. It
was shown that changing from iodide to trifluoromethylsul-
fonate (TfO) lowers the overall rate of the reaction from 87%
to 11% (conversion after 25 hours; Table 1, Entries 2–5).
Moreover, the reaction of aryl halides bearing electron-
donating group at the para position yielded lower conver-
sions, while electron-withdrawing groups at the para position
increase the overall reaction rate (CF3 > H > Me > OMe;
Scheme 4. Catalytic performance of the [SiCCSi]NiBr2 precatalyst in the
Buchwald–Hartwig coupling of phenyl chloride with different amines.
[a] triphenylamine formed as a byproduct.
Table 1: [SiCCSi]NiBr2-catalyzed amination of various aryl halides.[a]
excellent yields (44 to 96%) depending on the steric and
electronic nature of the amine substrates, as was the case with
varying the aryl substituent. In general, bulky substituents on
the amine substrates hamper the catalytic performance of the
catalyst, thus resulting in lower yields (e.g., diisopropylamine
3d, 69%, Scheme 4). The relatively low yield of 3e (44%) is
likely due to the fact that 3e undergoes further transforma-
tion with phenyl chloride to form triphenyl amine as
a byproduct. It was also shown that the reaction of benzyl
chloride with morpholine proceeds very efficiently, giving 3i
in 83% yield.
As previously proposed for this type of coupling reac-
tion,[15] and according to a control experiment in the presence
of 2,2,6,6-tetramethyl-l-piperidinoxyl (TEMPO; Table S9,
Entry 20), we reason that the catalytic cycle starts with the
formation of [SiCCSi]Ni0 as the catalytically active species
through the known base-assisted reduction of [SiCCSi]NiBr2
by amines. The former complex undergoes oxidative addition
of an aryl halide and subsequent replacement of the halide
anion by an amide substrate to give the corresponding
ArX (1)
R
Conversion[b]
%
Selectivity [%][b]
3’
X
1
2
3
4
5
6
7
8
9
H
Cl
Cl
Br
I
OTf
Cl
Cl
Cl
Cl
76
62
86
87
11
61
81
33
50
99
99
97
45[c]
15
98
98
99
96
4-Me
4-Me
4-Me
4-Me
4-OMe
4-CF3
2-Me
3-Me
[a] Reaction conditions: 1 (0.5 mmol), 2 (0.75 mmol), [SiCCSi]NiBr2
(0.5 mol%), AgBPh4 (1.25 mol%), KOtBu (1.2 equiv), T=1008C, sol-
vent=dioxane (1.5 mL), internal standard=decane, t=16 h. [b] Con-
versions and selectivities were determined by GC and GC/MS using
decane as internal standard and based on the substrate 1. [c] Homo-
coupling product formed.
ꢀ
[SiCCSi]Ni(Ar)NR2 intermediate. The desired C N coupling
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Driess, J. Organomet. Chem. 2016, DOI: 10.1016/j.jorgan-
chem.2016.07.014.
product is then liberated through a reductive elimination step
to regenerate the Ni0 catalyst. Accordingly, the Ni0-based
[SiCCSi]Ni(CO)2 complex can also be used as a precatalyst
[7] a) A. Brꢁck, D. Gallego, W. Wang, E. Irran, M. Driess, J. F.
Hartwig, Angew. Chem. Int. Ed. 2012, 51, 11478 – 11482; Angew.
Chem. 2012, 124, 11645 – 11649; b) D. Gallego, A. Brꢁck, E.
Irran, F. Meier, M. Kaupp, M. Driess, J. F. Hartwig, J. Am. Chem.
Soc. 2013, 135, 15617 – 15626; c) G. Tan, S. Enthaler, S. Inoue, B.
Blom, M. Driess, Angew. Chem. Int. Ed. 2015, 54, 2214 – 2218;
Angew. Chem. 2015, 127, 2242 – 2246; d) W. Wang, S. Inoue, S.
Enthaler, M. Driess, Angew. Chem. Int. Ed. 2012, 51, 6167 – 6171;
Angew. Chem. 2012, 124, 6271 – 6275; e) T. T. Metsꢃnen, D.
Gallego, T. Szilvꢆsi, M. Driess, M. Oestreich, Chem. Sci. 2015, 6,
7143 – 7149; f) D. Gallego, S. Inoue, B. Blom, M. Driess,
Organometallics 2014, 33, 6885 – 6897; g) B. Blom, S. Enthaler,
S. Inoue, E. Irran, M. Driess, J. Am. Chem. Soc. 2013, 135, 6703 –
6713; h) M. Stoelzel, C. Prꢃsang, B. Blom, M. Driess, Aust. J.
Chem. 2013, 66, 1163 – 1170; i) W. Wang, S. Inoue, E. Irran, M.
Driess, Angew. Chem. Int. Ed. 2012, 51, 3691 – 3694; Angew.
Chem. 2012, 124, 3751 – 3754; j) W. Wang, S. Inoue, S. Yao, M.
Driess, J. Am. Chem. Soc. 2010, 132, 15890 – 15892.
ꢀ
but results in significantly lower yields of the desired C N
coupling products (e.g., 22% lower yield for 3a compared to
[SiCCSi]NiBr2), thus indicating that CO decreases the activity
of the catalyst due to favorable OC!Ni coordination. The
higher catalytic activity of [SiCCSi]Ni compared to [SiFcSi]Ni
and related bis(phosphine)Ni systems is in accord with
a stronger donor character of [SiCCSi], which facilitates the
oxidative addition step at Ni0, whilst its steric bulk favors the
reductive elimination step, thus enabling a superior steering
role of that ligand throughout the reaction.
In summary, the first chelating bis(NHSi)-substituted o-
carborane ligand, SiCCSi, was synthesized and fully charac-
terized. Due to its extraordinarily strong s-donor character,
the corresponding [SiCCSi]NiBr2 complex surpasses the
catalytic activity of the Ni-based precatalysts reported to
date for Buchwald–Hartwig amination reactions of aryl
halides with secondary amines.
[8] a) M. Joost, L. Estꢂvez, K. Miqueu, A. Amgoune, D. Bourissou,
Angew. Chem. Int. Ed. 2015, 54, 5236 – 5240; Angew. Chem.
2015, 127, 5325 – 5329; b) N. M. Scott, H. Clavier, P. Mahjoor,
E. D. Stevens, S. P. Nolan, Organometallics 2008, 27, 3181 – 3186;
c) F. Rçhrscheid, R. H. Holm, J. Organomet. Chem. 1965, 4,
335 – 338, and references therein.
Acknowledgements
[9] Z. Freixa, P. W. N. M. van Leeuwen, Dalton Trans. 2003, 1890 –
1901.
We are grateful to the Cluster of Excellence UniCat for
financial support (sponsored by the Deutsche Forschungsge-
meinschaft and administered by the TU Berlin). We thank Dr.
Somenath Garai, Dr. Zhenbo Mo, Marcel Lꢁcke, and Paula
Nixdorf for their contributions and helpful discussions. Y.P.Z.
wishes to thank the Berlin International Graduate School of
Natural Sciences and Engineering (BIG-NSE) for support.
T.S. is grateful for generous support from The New Szꢂchenyi
Plan TAMOP-4.2.2/B- 10/1-2010-0009.
[10] a) D. S. Surry, S. L. Buchwald, Angew. Chem. Int. Ed. 2008, 47,
6338 – 6361; Angew. Chem. 2008, 120, 6438 – 6461; b) J. F.
Hartwig, Acc. Chem. Res. 2008, 41, 1534 – 1544; c) J. P. Wolfe,
S. Wagaw, J.-F. Marcoux, S. L. Buchwald, Acc. Chem. Res. 1998,
31, 805 – 818; d) J. F. Hartwig, Angew. Chem. Int. Ed. 1998, 37,
2046 – 2067; Angew. Chem. 1998, 110, 2154 – 2177.
[11] a) R. M. Bullock, Science 2013, 342, 1054 – 1055; b) S. Chakra-
borty, P. Bhattacharya, H. Dai, H. Guan, Acc. Chem. Res. 2015,
48, 1995 – 2003; c) P. J. Chirik, Acc. Chem. Res. 2015, 48, 1687 –
1695; d) P. L. Holland, Acc. Chem. Res. 2015, 48, 1696 – 1702;
e) E. McNeill, T. Ritter, Acc. Chem. Res. 2015, 48, 2330 – 2343;
f) J. Miao, H. Ge, Eur. J. Org. Chem. 2015, 7859 – 7868; g) R. H.
Morris, Acc. Chem. Res. 2015, 48, 1494 – 1502; h) B. Su, Z.-C.
Cao, Z.-J. Shi, Acc. Chem. Res. 2015, 48, 886 – 896; i) S. Z. Tasker,
E. A. Standley, T. F. Jamison, Nature 2014, 509, 299 – 309; j) S. A.
Johnson, Dalton Trans. 2015, 44, 10905 – 10913; k) T. Kurahashi,
S. Matsubara, Acc. Chem. Res. 2015, 48, 1703 – 1716; l) E. A.
Standley, S. Z. Tasker, K. L. Jensen, T. F. Jamison, Acc. Chem.
Res. 2015, 48, 1503 – 1514; m) A. Thakur, J. Louie, Acc. Chem.
Res. 2015, 48, 2354 – 2365; n) M. Tobisu, N. Chatani, Acc. Chem.
Res. 2015, 48, 1717 – 1726.
Keywords: homogeneous catalysis · N-heterocyclic silylenes ·
ligand design · nickel · o-carboranes
[1] 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 – 2692.
[12] a) V. Ritleng, M. Henrion, M. J. Chetcuti, ACS Catal. 2016, 6,
890 – 906; b) E. B. Corcoran, M. T. Pirnot, S. Lin, S. D. Dreher,
D. A. DiRocco, I. W. Davies, S. L. Buchwald, D. W. C. MacMil-
lan, Science 2016, 353, 279 – 283; c) M. S. Oderinde, N. H. Jones,
A. Juneau, M. Frenette, B. Aquila, S. Tentarelli, D. W. Robbins,
J. W. Johannes, Angew. Chem. Int. Ed. 2016, DOI: 10.1002/
anie.201604429; Angew. Chem. 2016, DOI: 10.1002/
ange.201604429.
[13] a) A. R. Martin, Y. Makida, S. Meiries, A. M. Z. Slawin, S. P.
Nolan, Organometallics 2013, 32, 6265 – 6270; b) S. Kuhl, Y. Fort,
R. Schneider, J. Organomet. Chem. 2005, 690, 6169 – 6177; c) R.
Omar-Amrani, A. Thomas, E. Brenner, R. Schneider, Y. Fort,
Org. Lett. 2003, 5, 2311 – 2314; d) B. T. Gradel, E. Brenner, R.
Schneider, Y. Fort, Tetrahedron Lett. 2001, 42, 5689 – 5692;
e) R. A. Green, J. F. Hartwig, Angew. Chem. Int. Ed. 2015, 54,
3768 – 3772; Angew. Chem. 2015, 127, 3839 – 3843; f) A. Bor-
zenko, N. L. Rotta-Loria, P. M. MacQueen, C. M. Lavoie, R.
McDonald, M. Stradiotto, Angew. Chem. Int. Ed. 2015, 54, 3773 –
[2] a) M. Asay, C. Jones, M. Driess, Chem. Rev. 2011, 111, 354 – 396;
b) S. Yao, Y. Xiong, M. Driess, Organometallics 2011, 30, 1748 –
1767.
[3] a) A. Meltzer, S. Inoue, C. Prꢃsang, M. Driess, J. Am. Chem. Soc.
2010, 132, 3038 – 3046; b) C. Zybill, Top. Curr. Chem. 1992, 160,
1 – 45; c) H. Ogino, H. Tobita, Adv. Organomet. Chem. 1998, 42,
223 – 290; d) M. Okazaki, H. Tobita, H. Ogino, Dalton Trans.
2003, 493 – 506; e) R. Waterman, P. G. Hayes, T. D. Tilley, Acc.
Chem. Res. 2007, 40, 712 – 719; f) L. ꢄlvarez-Rodrꢅguez, J. A.
Cabeza, P. Garcꢅa-ꢄlvarez, D. Polo, Coord. Chem. Rev. 2015,
300, 1 – 28.
[4] Z. Benedek, T. Szilvꢆsi, RSC Adv. 2015, 5, 5077 – 5086.
[5] a) A. Fꢁrstner, H. Krause, C. W. Lehmann, Chem. Commun.
2001, 2372 – 2373; b) M. Zhang, X. Liu, C. Shi, C. Ren, Y. Ding,
H. W. Roesky, Z. Anorg. Allg. Chem. 2008, 634, 1755 – 1758.
[6] a) B. Blom, D. Gallego, M. Driess, Inorg. Chem. Front. 2014, 1,
134 – 148; b) B. Blom, M. Stoelzel, M. Driess, Chem. Eur. J. 2013,
19, 40 – 62; c) S. Raoufmoghaddam, Y.-P. Zhou. Y. Wang, M.
4
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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Angewandte
Communications
Chemie
3777; Angew. Chem. 2015, 127, 3844 – 3848; g) N. H. Park, G.
7664; p) E. Brenner, R. Schneider, Y. Fort, Tetrahedron 1999, 55,
Teverovskiy, S. L. Buchwald, Org. Lett. 2014, 16, 220 – 223;
h) S. S. Kampmann, A. N. Sobolev, G. A. Koutsantonis, S. G.
Stewart, Adv. Synth. Catal. 2014, 356, 1967 – 1973; i) S. Ge, R. A.
Green, J. F. Hartwig, J. Am. Chem. Soc. 2014, 136, 1617 – 1627;
j) L. Hie, S. D. Ramgren, T. Mesganaw, N. K. Garg, Org. Lett.
2012, 14, 4182 – 4185; k) S. D. Ramgren, A. L. Silberstein, Y.
Yang, N. K. Garg, Angew. Chem. Int. Ed. 2011, 50, 2171 – 2173;
Angew. Chem. 2011, 123, 2219 – 2221; l) T. Shimasaki, M. Tobisu,
N. Chatani, Angew. Chem. Int. Ed. 2010, 49, 2929 – 2932; Angew.
Chem. 2010, 122, 2991 – 2994; m) G. Manolikakes, A. Gav-
ryushin, P. Knochel, J. Org. Chem. 2008, 73, 1429 – 1434;
n) Chen, L.-M. Yang, J. Org. Chem. 2007, 72, 6324 – 6327; o) C.
Desmarets, R. Schneider, Y. Fort, Tetrahedron 2001, 57, 7657 –
12829 – 12842; q) C. M. Lavoie, P. M. MacQueen, N. L. Rotta-
Loria, R. S. Sawatzky, A. Borzenko, A. J. Chisholm, B. K.
Hargreaves, R. McDonald, M. J. Ferguson, M. Stradiotto, Nat.
Chem. 2016, DOI: 10.1038/ncomms11073.
[14] J. Dou, D. Zhang, D. Li, D. Wang, J. Organomet. Chem. 2006,
691, 5673 – 5679.
[15] K. Matsubara, K. Ueno, Y. Koga, K. Hara, J. Org. Chem. 2007,
72, 5069 – 5076.
Received: July 19, 2016
Published online: && &&, &&&&
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.angewandte.org
5
These are not the final page numbers!

Angewandte
Communications
Chemie
Communications
Homogeneous Catalysis
The right bite: A chelating bis-N-hetero-
cyclic silylene ligand bridged by an o-
carborane (SiCCSi) and its corresponding
Ni complexes (see example) were syn-
thesized, fully characterized, and suc-
cessfully applied in Ni-catalyzed Buch-
wald–Hartwig coupling reactions. [SiCC-
Si]NiBr2 is the most active precatalyst for
this transformation that has been
reported to date.
Y.-P. Zhou, S. Raoufmoghaddam,
T. Szilvꢁsi, M. Driess*
&&&& — &&&&
A Bis(silylene)-Substituted ortho-
Carborane as a Superior Ligand in the
Nickel-Catalyzed Amination of Arenes
6
www.angewandte.org
ꢀ 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2016, 55, 1 – 6
These are not the final page numbers!