Stereoselective hydrodehalogenation via a radical-based mechanism involving T-shaped chiral nickel(I) pincer complexes

Article abstract of DOI:10.1002/chem.201403243

We herein report the catalytic enantioselective hydrodehalogenation based on the interplay of a chiral molecular nickel(I)/nickel(II)hydride system. Prochiral geminal dihalogenides are dehalogenated via a secondary configurationally unstable, potentially metal-stabilized radical intermediate. In a subsequent step, the liberated radical is then trapped by the nickel(II) hydrido complex, present in a large excess under the catalytic conditions, which in turn induces the enantioselectivity during the hydrogen atom transfer onto the radical intermediate. These new chiral nickel(I) complexes were found to catalyze the asymmetric hydrodehalogenation of geminal dihalogenides with moderate to good enantiomeric excess values using LiEt₃BH as reductant. The main side product generally observed is the dehalogenated alkene, whereas the hydrodehalogenation of the chiral monohalogen compound occurred much more slowly despite the large excess of reductant. Take and give: A chiral molecular nickel(I)/nickel(II)hydride system transforms prochiral geminal dihalogenides in a catalytic hydrodehalogenation to secondary organohalides. Abstraction of a halogen atom by the nickel(I) species generates an organoradical, possibly in rapid equilibrium with a metal-stabilized form, which is enantioselectively reduced by the hydrido nickel complex (see scheme).

Full text of DOI:10.1002/chem.201403243

DOI: 10.1002/chem.201403243
Full Paper
&
Asymmetric Catalysis
Stereoselective Hydrodehalogenation via a Radical-Based
Mechanism Involving T-Shaped Chiral Nickel(I) Pincer Complexes
[
a]
Christoph Rettenmeier, Hubert Wadepohl, and Lutz H. Gade*
Dedicated to Professor Helmut Werner on the occasion of his 80th birthday
Abstract: We herein report the catalytic enantioselective hy-
drodehalogenation based on the interplay of a chiral molec-
ular nickel(I)/nickel(II)hydride system. Prochiral geminal diha-
logenides are dehalogenated via a secondary configuration-
ally unstable, potentially metal-stabilized radical intermedi-
ate. In a subsequent step, the liberated radical is then
trapped by the nickel(II) hydrido complex, present in a large
excess under the catalytic conditions, which in turn induces
the enantioselectivity during the hydrogen atom transfer
onto the radical intermediate. These new chiral nickel(I)
complexes were found to catalyze the asymmetric hydrode-
halogenation of geminal dihalogenides with moderate to
good enantiomeric excess values using LiEt BH as reductant.
3
The main side product generally observed is the dehalogen-
ated alkene, whereas the hydrodehalogenation of the chiral
monohalogen compound occurred much more slowly de-
spite the large excess of reductant.
Introduction
Radical-based mechanistic pathways have been proposed both
for nickel-catalyzed hydrodehalogenations and related CꢀC
[
1]
coupling reactions. For the latter, remarkable enantioselectivi-
[2]
ties have been achieved using chiral molecular catalysts. On
the other hand, whereas there have been a few attempts to
[
3]
achieve enantioselective hydrodehalogenation, no example
we are aware of employs a well-defined chiral molecular cata-
lyst. A key question underlying the development of enantiose-
lective hydrodehalogenation involving potential radical inter-
mediates and multiple oxidation states of the metal concern
the mechanism of stereo induction in such a transformation.
Our approach is based on the partial hydrodehalogenation
of prochiral geminal dihalides catalyzed by a molecular Ni cata-
lyst. Two distinct molecular forms in different oxidation states
interact with the substrate as well as the resulting reaction in-
termediate in subsequent steps of the catalytic transformation.
Both nickel complexes contain the same chiral ligand, however,
their role during the catalysis differs substantially: In a first
step, the nickel(I) complex abstracts a halogen atom from the
geminal dihalogenide, generating a nickel(II) chlorido complex
and a configurationally labile radical species. The latter may be
stabilized by a reversible coordination to the generated NiꢀCl
Scheme 1. Reactivity pattern observed for the hydrodehalogenation.
excess under the catalytic conditions, which in turn induces
the enantioselectivity during the hydrogen atom transfer onto
the radical intermediate (Scheme 1).
Results and Discussion
We have previously reported the synthesis of the bisoxazolin-
methylpyrrolido nickel chlorido complex 1b and investigated
its isomerization to the bis(oxazolinylmethylidene)pyrrolidinido
[5]
complex 2b (Scheme 2). The rearrangement involves the pla-
narization of the pincer ligand in which a conjugated 10-p-
electron system strongly interacts with the metal center result-
ing in a significant stabilization. The latter has been found to
be essential for the synthesis of a series of remarkably stable
[
4]
complex. In a subsequent step, the liberated radical is then
trapped by the nickel(II) hydrido complex, present in a large
[6,7]
nickel(I) complexes
by the reaction of the chlorido nickel
complexes with LiEt BH. The nickel hydrido complexes 3,
3
[
a] C. Rettenmeier, Prof. Dr. H. Wadepohl, Prof. Dr. L. H. Gade
Anorganisch-Chemisches Institut, Univeristꢀt Heidelberg
Im Neuenheimer Feld 270, 69120 Heidelberg (Germany)
E-mail: lutz.gade@uni-hd.de
which are initially formed, undergo H elimination to generate
2
the T-shaped nickel(I) species 4 (Figure 1).
2
cðLigNiHÞ
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/chem.201403243.
K ¼
I
2
cðLigNi Þ ꢁ pðH Þ
2
Chem. Eur. J. 2014, 20, 9657 – 9665
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Scheme 2. Synthesis of new nickel hydrido complexes 3 and nickel(I) com-
plexes 4.
Figure 1. Second-order dependency on the concentration of 3a for the rate
of hydrogen elimination in 3a at 273 K.
In solution the nickel(I) and nickel hydrido complexes are in
a hydrogen pressure-dependent dynamic equilibrium (K=
ꢀ
1
1
2.4 bar at 295 K for 3a/4a, Scheme 2) with the rate of the
II
I
Ni ꢀH!Ni interconversion being of second order in hydrido
Figure 2. a) Molecular structure of deuterido complex 3a[D]. Only one of
the two independent molecules is shown, hydrogen atoms are removed for
clarity. Selected bond length [ꢂ] and angles [8]: Ni1–N3
complex concentration, which is consistent with a bimolecular
ꢀ
4
ꢀ1 ꢀ1
mechanism (k=5.31ꢁ10 Lmol
s
at 273 K for 4a;
1
1
1
9
.8632(19)/[1.8544(17)], Ni1–N1 1.8649(19)/[1.8589(17)], Ni1–N2
.9368(18)/[1.9311(17)], N3-Ni1-N1 172.65(9)/[172.53(8)], N2-Ni1-D1
74.6(10)/[176.5(11)], N3-Ni1-N2 93.45(8)/[93.34(8)], N1-Ni1-N2
3,80(8)/[94,10(8)]; b) molecular structure of 4a. Selected bond length [ꢂ]
Figure 1).
Single-crystal X-ray structure analyses of 3a and 4a estab-
lished an almost perfectly planar ligand frame in a meridional
coordination to the nickel center with small differences in its
coordination geometry (Figure 2). Whereas 3a contains
a square-planar coordination site, the absence of the hydride
ligand in 4a results in a minor distortion towards a Y-shaped
arrangement of the N donor atoms around the Ni center. The
and angles [8]: Ni–N1 1.875(2), Ni–N3 1.877(2), Ni–N2 1.920(2), N1-Ni-N3
69.44(9), N1-Ni-N2 94,52(9), N3-Ni-N2 96,00’(10); c) SOMO-orbital of 4a cal-
1
culated at the open shell DFT B3LYP/6-311G(d,p) level (isovalue of 0.4).
central NiꢀN
bond is slightly shortened on going from 3a
1.876(2) ꢂ) and the NcentralꢀNiꢀN angles widen (93.67(8) to
95.26(10)8). Nevertheless, the coordination geometry of 4a re-
mains very close to the ideal T-shaped geometry in compari-
central
to 4a (average values: 1.9349(18) to 1.920(2) ꢂ), whereas the
NiꢀNox distances become slightly longer (1.8604(18) to
Chem. Eur. J. 2014, 20, 9657 – 9665
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son to other nickel(I) structures described in literature
Table 1. Catalyst screening for selected substrates.
[
6b,8]
as such.
In view of the observed importance of the ligand
rearrangement, which gives rise to the conjugated p-
I
electron system, for the formation of the Ni species
Entry
Substrate
t
Cat.
Yield
ee
[%]
(no such transformation was observed for 1a–d), the
[
a]
[
%]
question inevitably arose as to the degree in which
the unpaired electron in 4 is located on the ligand
itself. In other words, we were interested to assess
whether the complex was better described as
a ligand-located rather than as a metal-centered radi-
cal, a notion which has implications for the assign-
ment of the redox state at the metal.
1
2
3
4
48 h
48 h
48 h
48 h
4a
4b
4c
4d
81
50
28
81
49
ꢀ51
ꢀ13
33
The spin density distribution calculated using open
[
9,10]
shell DFT methods at the B3LYP/6-311G(d,p)
level
clearly indicates a mainly metal-located unpaired
electron with a Mulliken atomic spin density of 0.97
5
6
5 d
5 d
4a
4d
59
48
74
46
at the nickel atom. The g value (g =2.16) of the EPR
av
resonances of 4a–d (see the Supporting Information)
observed by X-band EPR spectroscopy has been ade-
quately modeled by the DFT study which supports
the assignment of complexes 4a–d as nickel(I) com-
1
[a] Conversion determined by H NMR spectroscopy after work-up using an internal
standard.
[
1d]
pounds.
These new chiral nickel(I) complexes were found to
catalyze the asymmetric hydrodehalogenation of
geminal dihalogenides with moderate-to-good enan-
tiomeric excesses (ee values, Table 1 and Table 2). The
reactions were carried out in THF as solvent using
Table 2. Substrate scope of the asymmetric hydrodehalogenation.
LiEt BH as reductant. Among the catalysts tested the
3
nickel complex 4a, containing the phenyl-substituted
ligand, yielded the best results (Table 1). The main
side product generally observed is the dehalogenat-
ed alkene, whereas the hydrodehalogenation of the
chiral monohalogen compound occurred much more
slowly despite the large excess of reductant. Dibro-
moalkanes reacted faster than dichloro compounds,
Entry
Substrate
t
T
[8C]
Yield
[%]
ee
[%]
[
a]
1
2
3
48 h
48 h
48 h
ꢀ20
ꢀ20
ꢀ20
81
49
84
83
47
42
however, LiEt BH itself is capable of reducing the di-
3
bromoalkanes below room temperature, whereas in
the case of dichloroalkanes no significant non-cata-
lyzed background reaction is observed at tempera-
tures of up to 608C.
4
5 d
ꢀ20
59
74
5
6
7
3 d
0
0
84
36
63
70
ꢀ21
48
As indicated above, hydrodehalogenations can be
carried out using a wide range of different homoge-
neous or heterogeneous catalysts, but it previously
proved very difficult to obtain significant chiral induc-
tion in such a transformation. Given the promising re-
sults obtained with the nickel complexes reported in
this work, we aimed to gain a better understanding
of the processes involved in this reaction. To this end,
a series of mechanistic studies was carried out to es-
tablish the active species in the process and to ad-
dress the question at which stage the stereochemis-
try of the products was determined.
3 d
48 h
ꢀ50
8
3 d
ꢀ78
74
60
1
[
a] Conversion determined by H NMR spectroscopy after work-up using an internal
standard.
Initially we probed the possibility of the involvement of sev-
eral competing reaction pathways: An Eyring plot of the enan-
tiomeric ratio of the product obtained from the catalytic hy-
drodehalogenation of 2,2-dichloro-1,2,3,4-tetrahydronaphtha-
lene with 4a as catalyst displayed a linear correlation for the
given temperature range, indicating a single mechanism for
[11]
the catalysis (Figure 3). Furthermore, the enantiomeric excess
was found to be constant during the course of the reaction
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Figure 3. Eyring plot of the enantiomeric ratio (e.r.) of the product obtained
from the catalytic hydrodehalogenation of 2,2-dichloro-1,2,3,4-tetrahydro-
naphthalene with 4a as catalyst.
(see the Supporting Information), and the presence of mercury
had no effect on the outcome. Thus, the participation of a het-
[1b,12]
erogeneous colloidal system as (a potentially competing)
reactive species in the catalysis appears unlikely. In addition,
the formation of nickel(0) colloids through disproportionation
of the nickel(I) complex as described in the literature for other
[
13]
nickel(I) species was not observed when 4a was heated in
toluene at 1108C for several hours.
As a precatalyst the halogenido (e.g., 2) or acetato nickel(II)
complexes could also be used. In the catalytic reaction, these
compounds were transformed very rapidly to the correspond-
ing hydrido species 3, which then slowly dehydrogenated to
give the Ni complex 4 (k=5.31ꢁ10 mol Ls , see above).
This conversion to 4 initially limits the activity of the catalyst
system until a steady state concentration of 4 is attained.
The importance of nickel(I) for the catalytic reaction was
demonstrated using the radical scavenger 2,2,6,6-tetramethyl-
piperidin-1-yl)oxy (TEMPO) during the ongoing catalytic con-
version. After the addition at ꢀ208C of a quantity of 7.5 mol%
of TEMPO, which corresponded to half the catalyst loading
Figure 4. Top: Effect of the addition of TEMPO (7.5 mol%) during the cataly-
sis on the course of the reaction monitored by H NMR spectroscopy.
Bottom: Processes causing the halt of the catalytic reaction (left) and molec-
ular structure of the isolated complex 5a (right).
1
I
ꢀ4
ꢀ1
ꢀ1
The key role of nickel(I) in the initiation step of the catalytic
dehalogenation led us to investigate its behavior in stoichio-
metric reactions with organohalides, which act as radical
probes. Rearrangements were observed both in the stoichio-
metric conversion with (bromomethyl)cyclopropane as well as
supermesityl bromide (Scheme 3a and b), as expected for the
(15 mol%) in the given experiment, the generation of the
product immediately halted. After 3 h (in the case at hand, the
time required for the complete reduction of TEMPO) the trans-
formation re-started and the reaction continued to full conver-
sion (Figure 4). The fact that the concentration of starting ma-
terial during the inhibition remained constant indicated that
the reaction did not stop due to the trapping of possibly gen-
erated organic radical intermediates, but that the initial step of
the catalytic cycle is suppressed. Stoichiometric reactions in-
volving the individual species represented in the TEMPO inhibi-
tion cycle depicted in Figure 4 were carried out: The NiꢀH
complexes 3a did not directly react with TEMPO under the
chosen conditions, whereas the corresponding nickel(I) species
[14]
occurrence of radical intermediates. A similar behavior was
observed in the catalytic reduction of supermesityl bromide
using LiEt BD (Scheme 3c).
3
To clarify the nature of the hydride transferring species
during the catalysis, a competition experiment was carried out
with the deuterido nickel complex 3a[D] and LiEt BH. A clear
3
preference for the incorporation of deuterium at the early
stage of the experiment was observed (Scheme 3d), indicating
that the nickel hydrido complex is the hydrogen atom transfer
reagent to the organic substrate rather than LiEt BH (see the
3
Supporting Information).
II
very rapidly formed the Ni -TEMPO addition product 5a, which
Furthermore, the fact that the product of the catalysis is ob-
tained enantiomerically enriched and that the transformation
can be run stoichiometrically with the same ee value by using
only the in situ-generated nickel hydrido complex and the sub-
strate also indicates that the hydrido complex is indeed trans-
ferring the hydride onto the substrate during the catalysis.
subsequently reacted with LiEt BH to give the nickel hydrido
3
complex 3a again. During the inhibition of the catalytic cycle
the concentration of 3a remained nearly constant, whereas
TEMPO acted as a nickel(I) scavenger and thereby inhibited the
initial reaction with the dichloro substrate.
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period of the catalysis when nickel(I) is added as precatalyst.
Nickel(I) reacts with the substrate to give the radical intermedi-
ate, which is then trapped by another nickel(I) complex instead
of being reduced by the nickel hydrido species as in the main
catalytic cycle. This is the two-site oxidative addition as repre-
sented in the stoichiometric reactions in Scheme 3a and b.
The nickel chloride complex, which is formed, is transformed
by LiEt BH to the nickel hydrido complex and re-enters the cat-
3
alytic cycle. We propose that the a-chloroalkyl complex elimi-
nates the dechlorinated alkene as observed experimentally and
the resulting NiCl species is transformed rapidly to the hydride
as discussed above. These transformations proceed until the
concentration of nickel(I) has decreased to a level at which the
competitive reduction of the intermediate radical by the hydri-
do complex is favored. The second regulatory path is the dy-
namic equilibrium between 3 and 4 mentioned above,
through which the nickel(I) species is continuously reformed.
To further support this mechanistic proposal depicted in
Scheme 4 and to substantiate the key role of NiꢀH as the
enantioselective hydrogen transfer reagent in the catalytic
cycle, the reaction with 2,2-dichloro-1,2,3,4-tetrahydronaphtha-
lene (entry 1, Table 2) was run at ꢀ208C using tris(trimethylsi-
lyl)silane (TTMSS) as hydride source and nickel(I) as precatalyst
(Scheme 5). TTMSS is incapable of transferring the hydride
Scheme 3. a), b) Stoichiometric reactions of 4a with bromo compounds;
c) isomerization of the bromo-2,4,6-tri-tert-butylbenzene-derived radical
during the catalytic hydrodehalogenation; d) competition experiment for
the hydride transfer onto the substrate of the catalysis between LigNiD and
3
LiEt BH.
Scheme 5. Reaction scheme for the catalytic hydrodehalogenation using
tris(trimethylsilyl)silane (TTMSS) and 4a as radical initiator.
Scheme 4. Proposed mechanism for the catalytic cycle of the hydrodehalo-
genation of geminal dihalogenes.
The proposed mechanism for the catalytic conversion under
steady state conditions based on the observations described
above is depicted in Scheme 4. The main catalytic cycle con-
tains the initial reaction of nickel(I) 4 with the dihalogeno sub-
strate 8 to form the halogenido complex 2 and the organorad-
ical 9 (possibly in rapid equilibrium with a metal-stabilized
form 10), which is enantioselectively reduced by the hydrido
nickel complex 3 to yield the product of the catalytic reaction
either to the nickel(I) or to the nickelchlorido complex. Control
experiments also excluded the possibility of a direct reaction
of TTMSS with the dichloro substrate under the chosen condi-
tions of the catalysis. In the catalytic transformation depicted
in Scheme 5 the racemic mixture of the corresponding mono-
chloro-substituted reaction product was obtained. TTMSS is
known to hydrodehalogenate organohalides at elevated tem-
[15]
peratures in the presence of radical starters. This is consis-
tent with a nickel(I)-initiated radical halide abstraction step and
a subsequent silane-based hydrogen atom transfer that mimics
the role of the chiral nickel hydride in the catalytic reaction.
The silane being achiral, the resulting product has to be race-
mic, as was observed.
11 and simultaneously regenerates the nickel(I) complex 4.
Crucial for the observed catalytic activity is the nickel(I) con-
centration, which is mainly regulated through two different
I
pathways that dominate depending on whether the Ni com-
plex is employed as catalyst or the nickel(II) hydrido complex is
II
generated initially from an appropriate Ni precursor. The
I
downregulation in c(Ni) occurs predominantly at the initial
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Preparation of (R)-Lig (iso)NiCl (2a)
Conclusion
Ph
Complex 1a (705 mg, 1.47 mmol) was dissolved in toluene (40 mL)
and heated to 908C for 8 h. The solvent was removed and the
product was recrystallized from a dichloromethane/pentane mix-
We have developed a chiral nickel-based hydrodehalogenation
catalyst that acts as a molecular system capable of mono-de-
halogenating prochiral geminal organodihalogenides with sig-
nificant enantioselectivities. A detailed mechanistic study has
unraveled the key species involved in the dehalogenation and
the subsequent enantioselective hydrogen-transfer step. The
well-behaved molecular nature of the system, along with the
mechanistic insight obtained in this study will provide the
basis for the further development of this methodology.
ture to give the product as dark-brown crystalline solid in 93%
1
yield (655 mg). H NMR (C
D
6
, 600.130 MHz, 295 K): d=7.35 (m, 4H,
6
8
9
10
3
3
H ), 7.19 (m, 4H, H ), 7.06 (m, 2H, H ), 5.71 (dd, J=8.8 Hz, J=
.9 Hz 2H, H ), 4.79 (s, 2H, H ), 3.57 (dd, J=8.3 Hz, J=8.7 Hz, 2H,
H ), 3.54 (dd, J=8.2 Hz, J=3.0 Hz, 2H, H ), 1.92–1.77 ppm (m, 4H,
); C NMR (C D , 150.903 MHz, 295 K): d=170.7 (C ), 163.7 (C ),
6 6
44.7 (C ), 128.8 (C ), 127.5 (C ), 126.9 (C ), 82.2 (C ), 74.0 (C ), 66.5
C ), 30.5 ppm (C ); HRMS (DART+): m/z calcd: for
C H ClN3 NiO : 478.0832; found: 478.0843; elemental analysis
6
3
2
3
2
5
2
3
5’
1,1’ 13
2
4
H
7
9
10
8
3
5
1
(
6
1
35
58
24
23
2
calcd (%) for C H ClN NiO : C 60.23, H 4.63, N 8.78; found: C
24
22
3
2
Experimental Section
5
9.90, H 4.63, N 8.72.
All manipulations of air- and moisture-sensitive materials were per-
formed under an inert atmosphere of dry argon using standard
Schlenk techniques or by working in a glovebox. Solvents were
dried over sodium (toluene), potassium (hexanes) or sodium/potas-
sium alloy (pentane, diethyl ether), distilled, and degassed prior to
Preparation of (R)-Lig (iso)NiOAc
Ph
To
a suspension of nickel(II) acetate tetrahydrate (0.82 g,
3
.28 mmol, 1.2 equiv) in methanol (15 mL), a solution of the protio-
[
16]
ligand (Lig H; 1.06 g, 2.74 mmol) in methanol (15 mL) was added.
use.
Deuterated solvents were dried over potassium (C D ,
ph
6
6
After stirring for 18 h at room temperature, the solvent was re-
moved under reduced pressure, toluene was added and the solu-
tion was filtered. After removal of the solvents, the product was re-
crystallized from a dichloromethane/pentane mixture to give the
[
D ]toluene, [D ]THF), vacuum distilled and stored in Teflon valve
8
8
ampoules under argon. Samples for NMR spectroscopy were pre-
pared under argon in 5 mm Wilmad tubes equipped with J. Young
Teflon valves. H- and C NMR spectra were recorded on Bruker
Avance 200, 400 and 600 NMR spectrometers and were referenced
1
13
product as red crystalline solid in 80% yield (1.09 g,
1
1
13
[17]
2.17 mmol). H NMR (CDCl , 399.890 MHz, 233 K): d=7.44–7.36 (m,
internally using the residual protio solvent ( H) or solvent ( C).
3
9
10
8
4
H, H ), 7.36–7.29 (m, 2H, H ), 7.25–7.16 (m, 4H, H ), 5.20 (m, 2H,
H ), 4.65 (s, 2H, H ), 4.31 (dd, J=8.3 Hz, J=8.3 Hz, 2H, H ), 4.15
d, J=8.1 Hz, 2H, H ), 2.50 (m, 4H, H ), 1.73 ppm (s, 3H,
H ); C NMR (CDCl , 100.552 MHz, 233 K): d=173.5 (C ), 168.0 (C ),
66.8 (C ), 144.2 (C ), 128.9 (C ), 127.7 (C ), 125.7 (C ), 83.4 (C ),
7.7 (C ), 69.3 (C ), 38.2 (C ), 29.2 ppm (C ); HRMS (FAB+): m/z
Elemental analyses were recorded by the analytical service of the
Heidelberg Chemistry Department. The enantioselectivities of the
products obtained from the catalytic hydrodehalogenation were
measured on a Finnigan Focus GC device using a Chiraldex G-TA
column. The phenyl-, isopropyl-, tert-butyl- and indandiyl-substitut-
ed bis(oxazolinylmethyl)pyrrole protioligands (Lig H, Lig H,
LigtBuH, LigindH) and complexes 1b, 2b and the corresponding ace-
tato complex (Lig (iso)NiOAc) were synthesized according to liter-
ature.
6
3
2
3
5
3
5’
1,1’
(
12
13
2
11
3
4
7
9
10
8
3
1
7
5
6
1
12
ph
iPr
calcd for C H N NiO : 501.1199; found: 501.1198; elemental analy-
26 25
3
4
sis calcd (%) for C H N NiO : C 62.18, H 5.02, N 8.37; found: C
26 25
3
4
iPr
[5b,c]
6
1.99, H 4.93, N 8.38.
All other reagents were obtained from commercial sour-
ces and used as received unless explicitly stated otherwise.
I
For Compounds 1–4, and the geminal dihalides the experimental
detail of only one representative example is shown here. Details of
the preparative procedures and characterization data for all other
compounds reported in this work as well as the atom labeling are
given in the Supporting Information.
Preparation of (R)-LigPhNi (4a)
LiEt BH (2.84 mmol, 1.2 equiv, 1m in THF) was added to a solution
of the nickel(II) acetato complex ((R)-LigPh(iso)NiOAc; 1.19 g,
3
2
.36 mmol) in toluene (20 mL), at ꢀ788C. After 10 min, the cooling
bath was removed and the reaction was stirred for another 40 min.
Pentane (80 mL) was added and the solution was filtrated, concen-
trated to 3 mL and stirred for 2 h at 908C under reduced pressure.
Subsequently, the solvent was removed completely and the prod-
uct was recrystallized from a toluene/pentane mixture at ꢀ408C to
give a dark-red crystalline solid in 82% yield (860 mg). Magnetic
susceptibility (Evans method): meff =1.92 mB; ESR (X-Band, toluene,
Preparation of (R)-LigPhNiCl (1a)
NaH (3.39 mmol, 1.4 equiv) was added at 08C to a solution of the
protioligand (Lig H; 936 mg, 2.43 mmol) in THF (20 mL), and
ph
stirred for 1 h. The solution was subsequently filtered and canulat-
ed to a suspension of [NiCl (dme)] (dme=dimethoxyethane)
2
(
4.86 mmol, 2 equiv) and THF (20 mL) at low temperature. After
9.444404 GHz, 120 K) g
x
=2.326, g
H NMR ([D ]toluene, 600.130 MHz, 295 K): d=27.1 (H ), 13.2 (H ),
8
y z z
=2.147, g =2.038, A =14.6 G;
1
6
8
the mixture was stirred for another 2 h at 08C the solvents were re-
moved. The residue was treated with a toluene/pentane (3:1) mix-
ture and the inorganic metal salts were filtered off. After the re-
moval of the solvents, the product was recrystallized from a di-
chloromethane/pentane mixture to give the product as dark-red
crystalline solid in 72% yield (840 mg). H NMR ([D ]toluene,
3
5
(
1
10
5
5’
9
3
1,1’
8.0 (H ), 6.4 (H ), 5.7 (H ), 4.8 (H ), ꢀ8.2 (H ), ꢀ39.2 ppm (H ); IR
(KBr): n˜ =2962 (w), 2894 (w), 1952 (w), 1878 (w), 1811 (w), 1606 (s),
1589 (s), 1535 (s), 1338 (m), 1288 (m), 1250 (s), 1215 (s), 1000 (s),
ꢀ1
960 (m), 768 (m), 733 (m), 698 cm (s); HRMS (FAB+); m/z calcd
1
58
for C24
H
N
3
NiO
: 442.1066; found: 442.1079; elemental analysis
NiO : C 65.05, H 5.00, N 9.48; found: C 64.82,
8
22
2
8
,9,10
1
99.890 MHz, 190 K): d=7.40–6.77 (m, 10H, H
), 6.07 (s, 2H, H ),
calcd (%) for C24
H 5.18, N 9.20.
H
22
N
3
2
6
3,3’,5,5’ 13
.29 (m, 2H, H ), 3.56–2.86 ppm (m, 8H,
[D ]toluene, 100.552 MHz, 190 K): d=170.5 (C ), 141.8 (C ), 130.0–
8
), 124.7 (C ), 106.4 (C ), 75.8 (C ), 65.4 (C ), 27.5 ppm
C ); HRMS (DART+): m/z calcd for C H ClN3 NiO : 478.0832;
24 23 2
H
); C NMR
4
7
8
/9/10
2
1
5
6
23.6 (C
Preparation of (R)-LigPhNiH[D] (3a/3a[D])
3
35
58
(
found: 478.0838; elemental analysis calcd (%) for C H ClN NiO : C
A solution of the nickel(I) complex 4a (18.4 mg, 0.042 mmol) in
24
22
3
2
6
0.23, H 4.63, N 8.78; found: C 60.23, H 4.72, N 8.85.
a toluene/pentane mixture was subjected to a 10 bar H (D ) pres-
2
2
Chem. Eur. J. 2014, 20, 9657 – 9665
www.chemeurj.org
9662
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
sure. After 48 h, crystals had formed and the solution was deca-
Preparation of (R)-Lig Ni-(iso)supermesityl (7a)
Ph
nted and finally completely removed under reduced pressure to
1
A
solution of 1-bromo-2,4,6-tri(tert-butyl)benzene (47 mg,
give the product in 75% yield (14 mg). H NMR ([D ]toluene,
8
8,9
0.144 mg, 1 equiv) in THF (5 mL) was added to a solution of the
nickel(I) complex 4a (127 mg, 0.287 mmol) in THF (2 mL), and was
stirred for 2 h. The solvents were removed and the residue was
treated with pentane, stirred for 30 min and filtered. After removal
6
00.130 MHz, 295 K): d=7.17–7.08 (m, 8H, H ), 7.08–7.02 (m, 2H,
1
0
3
6
5
H ), 5.12 (s, 2H, H ), 4.46 (m, 2H, H ), 3.74 (m, 2H, H ), 3.65 (m, 2H,
H ), 2.29 (m, 4H,
5’
1,1’
11
13
H
), ꢀ24.86 ppm (s, 1H, H ); C NMR
2
4
(
(
[D ]toluene, 150.903 MHz, 295 K): d=169.5 (C ), 165.0 (C ), 145.7
C ), 128.6 (C ), 127.3 (C ), 127.2 (C ), 80.7 (C ), 75.6 (C ), 73.6 (C ),
8
7
9
8
10
3
6
5
of the solvents, the product was obtained as an orange solid in
1
1
45% yield (90 mg). H NMR (C
D
6
6
, 600.130 MHz, 295 K): d=7.61 (d,
3
0.9 ppm (C ); IR (KBr): n˜ =3025 (w), 2953 (w), 2891 (w), 1858 (Ni-
4
16
8
18
J=1.6 Hz, 2H, H ), 7.34–7.21 (m, 4H, H ), 7.32 (m, 1H, H ), 7.14
H) (s), 1593 (s), 1522 (s), 1451 (m), 1432 (m), 1340 (m), 1289 (s),
9
3
10
3
(
m, 4H, H ), 7.02 (t, J=7.4 Hz, 2H, H ), 5.10 (s, 2H, H ), 4.73 (dd,
J=8.5 Hz, J=2.2 Hz, 2H, H ), 3.48 (dd, J=7.6 Hz, J=2.3 Hz, 2H,
1
5
4
249 (s), 1215 (s), 1069 (m), 1018 (s), 979 (s), 733 (s), 699 (s),
3
3
6
2
3
ꢀ1
60
33 cm
(m); HRMS (FAB+): m/z calcd for C H DN NiO2:
24 22 3
5
5‘
13
1,1‘
58
H ), 3.35–3.15 (m, 2H, H ), 2.71 (s, 3H, H ), 2.27 (m, 4H, H ), 1.40
(s, 18H, H ), 1.18 (d, J=9.2 Hz, 1H, H ), 1.07 (d, J=9.2 Hz, 1H,
H ), 0.77 ppm (s, 3H, H ); C NMR (C D , 150.903 MHz, 295 K): d=
46.1161; found: 446.1117; m/z calcd for C H DN NiO (444.1207)
24
22
3
2
20
2
11
2
6
0
and C H N NiO2 (444.1020): one signal at m/z 444.1074 was
2
4
22
3
11’
14 13
6
6
found; elemental analysis calcd (%) for C H N NiO : C 64.90, H
24
23
3
2
2
4
15
17
7
9
1
1
6
70.8 (C ), 165.0 (C ), 153.5 (C ), 149.4 (C ), 145.1 (C ), 129.0 (C ),
27.6 (C ), 126.4 (C ), 121.4 (C ), 118.8 (C ), 80.5 (C ), 73.5 (C ),
9.8 (C ), 42.8 (C ), 35.1 (C ), 34.2 (C ), 31.9 (C ), 30.9 (C ), 29.1
5
.22, N 9.46; found: C 64.85, H 5.32, N 9.13.
10
8
16
18
3
5
6
12
13
19
20
1
Preparation of (R)-Lig Ni-TEMPO (5a)
14
11
58
Ph
(C ), 20.2 ppm (C ); HRMS (DART+): m/z calcd for C H N NiO2:
42 52 3
6
88.3413; found: 688.3428; elemental analysis calcd (%) for
A solution of TEMPO (14.1 mg, 0.090 mmol, 1 equiv) in a toluene/
pentane (1:3) mixture (1 mL) was added to a solution of complex
C H N NiO : C 73.26, H 7.47, N 6.10; found: C 72.74, H 7.95, N
42
41
3
2
5
.42.
4
a (40 mg, 0.090) in toluene (0.5 mL), at room temperature and
stirred for 5 min. Subsequently, pentane (3 mL) was added and the
reaction mixture was stored at ꢀ408C to give the product as dark-
1
Preparation of geminal dihalides
brown crystalline solid in 67% yield (36 mg). H NMR ([D ]toluene,
8
3
8
3
9
4
99.890 MHz, 238 K): d=7.70 (d, J=7.5 Hz, 2H, H ), 7.26–6.96 (m,
The geminal dihalides used as substrates for the catalysis were pre-
pared following the methodology by Takeda et al.
6
,9,10,18,19,20
3
16
3/13
H, H
), 5.13 (d, J=7.4 Hz, 1H, H ), 5.06 (s, 1H, H ),
.94 (s, 1H, H ), 4.14 (dt, J=8.1 Hz, J=8.1 Hz, 1H, H ), 3.98 (d,
J=8.0 Hz, 1H, H ), 3.80 (dt, J=7.7 Hz, J=7.6 Hz, 1H, H ), 3.67 (d,
J=7.8 Hz, 1H, H ), 2.08 (s, 3H, H ), 2.00–1.71 (m, 4H, H
), 1.14 (s, 3H, H ), 0.91 (s, 3H, H ),
.28 ppm (s, 3H, H ); C NMR ([D ]toluene, 100.552 MHz, 238 K):
d=171.4 (C ), 171.2 (C ), 165.2 (C ), 164.1 (C ), 145.7 (C ), 144.9
[18]
3
/13
2
3
5
2
,2-Dichloro-1,2,3,4-tetrahydronaphthalene: Yield: 810 mg color-
5’
15
1
less solid, 47%. H NMR (CDCl , 600.130 MHz, 295 K): d=7.22–7.12
1
5‘
26
1,1‘,11,11’
3
8
),
7,6,5
1
3
(m, 3H, H ), 7.04 (s, 1H, H ), 3.69 (s, 2H, H ), 3.10 (t, J=6.6 Hz,
2
2,22’,23,23’,24,24’
28
29
1
0
.59–1.09 (m, 6H, H
4
3
3
13
2
1
H, H ), 2.62 ppm (t, J=6.6 Hz, 2H, H );
C NMR (CDCl3,
2
7
13
8
10
9
5
50.903 MHz, 295 K): d=133.1 (C ), 132.5 (C ), 128.9 (C ), 128.7
2
/12
2/12
14
4
7
8
6/7
6/7
2
1
3
(
(
C ), 127.1 (C ), 126.5 (C ), 88.2 (C ), 50.1 (C ), 42.5 (C ), 28.3 ppm
1
7
9
19
10/20
10/20
8
(
1
5
C ), 128.9 (C ), 128.1 (C ), 126.7 (C ), 126.3 (C ), 126.3 (C ),
4
35
C ); HR-MS (EI+): m/z calcd for C H
L2: 200.0160; found:
10 10
1
8
3/13
3/13
5
15
16
25.4 (C ), 82.2 (C ), 81.2 (C ), 75.7 (C ), 74.8 (C ), 59.1 (C ),
2
00.0151; elemental analysis calcd (%) for C H Cl : C 59.73, H
10 10 2
2
5
21
6
24
22
26
8.1 (C ), 58.1 (C ), 55.3 (C ), 41.1 (C ), 40.8 (C ), 34.7 (C ), 31.2
C ), 30.5 (C ), 30.3 (C ), 23.5 (C ), 20.2 (C ), 18.1 ppm (C );
5
.01; found: C 59.86, H 5.05.
2
8
1/11
1/11
29
27
23
(
58
HRMS (DART+): m/z calcd for C H N NiO : 599.2532; found:
33
40
4
3
5
6
99.2532; elemental analysis calcd (%) for C H N NiO : C 66.13, H
33 40 4 3
.73, N 9.35; found: C 65.65, H 6.74, N 9.17.
General procedure for the catalytic conversion of geminal
dichlorides using LiEt BH as reductant
3
A solution of the catalyst (7.5 mol% in 0.2 mL THF) was slowly
added to a solution of the geminal dichloride (0.099 mmol) and
Preparation of (R)-Lig Ni-butenyl (6a)
Ph
After the activation of Mg turnings (80 mg) by traces I , (bromome-
2
LiEt BH (0.20 mol) in THF (0.5 mL) at the indicated temperature.
3
thyl)cyclopropane (78 mg, 0.57 mmol) dissolved in THF (5 mL) was
added and stirred for 2 h at RT. The reaction mixture was filtered
and canulated to a solution of the nickel chlorido complex 2a
After the given time, the reaction was quenched using a saturated
NH Cl solution and the reaction products were extracted with pen-
4
tane (3ꢁ1 mL). After removal of the volatiles, the crude was dis-
solved in a pentane/diethyl ether (9:1) mixture and flushed
through a silica plug (washed with 3ꢁ1 mL of the 9:1 mixture).
After removal of the solvents, the product was dissolved in CDCl3
and 1,4-dimethoxybenzene as internal standard was added to de-
termine the yield of the reaction. GC analysis was performed to de-
termine the enantiomeric excess of the product.
(
97 mg, 0.20 mmol) at 08C. After 10 min, the solvents were re-
moved and the residue was treated with a toluene/pentane mix-
ture (1:20), stirred for 15 min and filtrated. After removal of the sol-
vents, the product was obtained as yellow powder in 75% yield
(
75 mg). The direct reaction of the nickel(I) complex 4a with an
excess of (bromomethyl)cyclopropane in C D at room temperature
6
6
1
led to the same isomerized compound (6a). H NMR (C D ,
6
6
3
8
6
00.130 MHz, 295 K): d=7.21 (d, J=7.5 Hz, 4H, H ), 7.12 (m, 4H,
H ), 7.01 (m, 2H, H ), 5.79 (m, 1H, H ), 5.16 (s, 2H, H ), 4.91 (dd,
9
10
13
3
General procedure for the catalytic conversion of geminal
3
3
6
14,14‘
J=8.6 Hz, J=2.1 Hz, 2H, H ), 4.90–4.84 (m, 2H, H
), 3.74 (dd,
dibromides using LiEt BH as reductant
2
3
5
2
3
3
J=8.1 Hz, J=8.6 Hz, 2H, H ), 3.64 (dd, J=8.1 Hz, J=2.5 Hz, 2H,
), 2.04 (m, 1H, H ), 0.75 (m, 1H, H ),
.54 ppm (m, 1H, H ); C NMR (C D , 150.903 MHz, 295 K): d=
71.5 (C ), 165.9 (C ), 144.9 (C ), 141.1 (C ), 128.9 (C ), 127.5 (C ),
26.1 (C ), 110.6 (C ), 81.0 (C ), 73.5 (C ), 67.8 (C ), 37.0 (C ), 31.1
C ), 10.3 ppm (C ); HRMS (FAB+): m/z calcd for C H N NiO2:
24 22 3
5
‘
1,1‘,12
12‘
11
H ), 2.24–2.10 (m, 5H, H
LiEt BH (0.6 mL of 1.0m THF solution, 0.60 mol) was added to a so-
3
11‘
13
0
1
1
lution of the catalyst (9.9 mg, 7.5 mol%) in THF (1.2 mL), and
cooled to the indicated temperature. A solution of the dibromide
(0.29 mmol in 0.6 mL) was added slowly and stirred for the given
time. The reaction mixture was treated using the work-up proce-
dure and analytic methods described above.
6
6
2
4
7
13
9
10
8
14
3
5
6
12
1
11
58
(
4
97.1613; found: 497.1667.
Chem. Eur. J. 2014, 20, 9657 – 9665
www.chemeurj.org
9663
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
[
23]
[24]
Determination of the enantiomeric excess by chiral GC anal-
ysis
ods; 4a: direct methods with dual-space recycling; 5a: charge
[
25]
2
flip. Refinement: full-matrix least squares methods based on F ;
all non-hydrogen atoms anisotropic, hydrogen atoms (except the
deuterides in 3a, which were refined) at calculated positions (re-
Fused Silica Capillary GC Column: Astec Chiraldex G-TA (2,6-di-O-
pentyl-3-trifluoroacetyl derivative of g-cyclodextrin); Dimension:
[26]
fined riding).
5
0 mꢁ0.25 mm; Film thickness: 0.12 mm; Carrier gas: He. For a de-
CCDC-978128 (3a), CCDC-978129 (4a), CCDC-978130 (5a) contain
the supplementary crystallographic data for this paper. These data
can be obtained free of charge from The Cambridge Crystallo-
graphic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
tailed description of the methodologies used see the Supporting
Information.
Computational studies (general)
[9]
The unrestricted DFT-B3LYP computational tool has been em-
ployed to model complex 4a with a 6-311g(d,p) basis set. All the
[10]
Acknowledgements
calculations have been carried out with the Gaussian 09 program
[19]
package. Stationary points were verified by frequency analysis.
The Cartesian coordinates of the optimized structure of 4a are
available in the Supporting Information.
We thank Prof. Dr. M. Enders, Dr. Marion Kerscher, Jan Freuden-
berg, Mathias Ronellenfitsch and Tim Stçßer for advice and ex-
perimental support. We acknowledge funding by the Deutsche
Forschungsgemeinschaft (SFB 623, TP B6).
Calculation of EPR parameters
The g-values of complex 4a were calculated using the Orca soft-
ware (version 2.9.1). Therefore, the optimized geometry above
was used as input geometry and the eprnmr feature on the B3LYP/
Keywords: asymmetric
enantioselectivity · nickel · radicals
catalysis
·
dehalogenation
·
[20]
6
-311G*(d,p) level was applied. Scalar relativistic corrections were
[
1] Selected key references for mechanistic investigations on CꢀC coupling
and hydrodehalogenation reactions: a) A. Bakac, J. H. Espenson, J. Am.
Chem. Soc. 1986, 108, 719–723; b) F. Alonso, I. P. Beletskaya, M. Yus,
Chem. Rev. 2002, 102, 4009–4092; c) T. J. Anderson, G. D. Jones, D. A.
Vicic, J. Am. Chem. Soc. 2004, 126, 8100–8101; d) G. D. Jones, J. L.
Martin, C. McFarland, O. R. Allen, R. E. Hall, A. D. Haley, R. J. Brandon, T.
Konovalova, P. J. Desrochers, P. Pulay, D. A. Vicic, J. Am. Chem. Soc. 2006,
applied for the electron structure calculations, and SO interactions
were accounted for using the mean-field approx. Spin-orbit mean
field (SOMF; incl. both spin-own-orbit and spin-other-orbit interac-
[21]
tions). G values (calcd): g =2.042, g =2.183, g =2.216.
x
y
z
Crystal data
Complex 3a: C H DN NiO , M=445.17, monoclinic, space group
1
28, 13175–13183; e) V. B. Phapale, E. BuÇuel, M. Garcꢃa-Iglesias, D. J.
Cꢄrdenas, Angew. Chem. 2007, 119, 8946–8951; Angew. Chem. Int. Ed.
2007, 46, 8790–8795; f) X. Hu, Chem. Sci. 2011, 2, 1867–1886; g) J. Brei-
tenfeld, J. Ruiz, M. D. Wodrich, X. Hu, J. Am. Chem. Soc. 2013, 135,
12004–12012.
2
4
22
3
2
P21, a=14.39570(10), b=7.40300(10), c=19.3928(2) ꢂ, b=
3
ꢀ3
1
04.6980(8)8, V=1999.09(4) ꢂ , Z=4, d =1.4790 Mgm , Cu
calcd Ka
1
ꢀ
radiation, l=1.5418 ꢂ, m=1.613 mm , F =928. T=115(1) K, q
000
[
[
2] Selected references for Ni-catalyzed enantioselective CꢀC coupling re-
range 3.4 to 72.08. Index ranges h, k, l: ꢀ17…17, ꢀ8…7, ꢀ23…23.
actions: a) F. O. Arp, G. C. Fu, J. Am. Chem. Soc. 2005, 127, 10482–
Reflections measured: 60179; independent: 7185 [R =0.027]; ob-
int
1
0483; b) F. Glorius, Angew. Chem. 2008, 120, 8474–8476; Angew. Chem.
Int. Ed. 2008, 47, 8347–8349; c) A. Rudolph, M. Lautens, Angew. Chem.
009, 121, 2694–2708; Angew. Chem. Int. Ed. 2009, 48, 2656–2670; d) J.
served [I>2s(I)]: 7162. Final R indices [F >4s(F )]: R(F)=0.0220,
o
o
2
ꢀ3
wR(F )=0.0605, GooF=1.039, residual dens.=0.36, ꢀ0.20 eꢂ
,
2
abs. structure parm. ꢀ0.001(8).
Choi, G. C. Fu, J. Am. Chem. Soc. 2012, 134, 9102–9105; e) J. T. Binder,
C. J. Cordier, G. C. Fu, J. Am. Chem. Soc. 2012, 134, 17003–17006.
Complex 4a: C H N NiO , M=443.15, orthorhombic, space group
2
4
22
3
2
3] a) R. Hazard, S. Jaouannet, A. Tallec, Tetrahedron 1982, 38, 93–102;
b) H.-U. Blaser, S. K. Boyer, U. Pittelkow, Tetrahedron: Asymmetry 1991, 2,
P2 2 2 ,
a=8.714(4),
b=10.859(6),
c=20.875(11) ꢂ,
V=
1
1 1
3
ꢀ3
1
0
3
975.3(18) ꢂ , Z=4, d
=1.490 Mg·m , MoKa radiation, l=
calcd
7
21–732; c) M. F. Kuehnel, T. Schlçder, S. Riedel, B. Nieto-Ortega, F. J.
Ramꢃrez, J. T. Lꢅpez Navarrete, J. Casado, D. Lentz, Angew. Chem. 2012,
24, 2261–2263; Angew. Chem. Int. Ed. 2012, 51, 2218–2220.
ꢀ1
.71073 ꢂ, m=1.009 mm , F000 =924. T=100(1) K, q range 2.0 to
2.28. Index ranges h, k, l: ꢀ12…12, ꢀ16…16, ꢀ30…31. Reflec-
1
tions measured: 41198, independent: 6672 [R =0.051], observed.
int
[4] a) D. G. Kelley, A. Marchaj, A. Bakac, J. H. Espenson, J. Am. Chem. Soc.
1991, 113, 7583–7587; b) B. B. Wayland, G. Poszmik, S. L. Mukerjee, M.
Fryd, J. Am. Chem. Soc. 1994, 116, 7943–7944.
[5] a) C. Mazet, L. H. Gade, Chem. Eur. J. 2003, 9, 1759–1767; b) F. Konrad, J.
Lloret Fillol, C. Rettenmeier, H. Wadepohl, L. H. Gade, Eur. J. Inorg. Chem.
2
[I>2s(I)]: 5820. Final R indices [F >4s(F )]: R(F)=0.0327, wR(F )=
o o
ꢀ
3
0
.0650, GooF=0.949, residual dens.=0.47, ꢀ0.30 eꢂ , abs. struc-
ture parm. ꢀ0.009(5).
Complex 5a·0.5 n-pentane: C3 H N NiO , M=635.47, orthorhom-
bic, space group P2 2 2 , a=14.0328(6), b=15.5952(6), c=
2
5.5
46
4
3
2
009, 4950–4961; c) F. Konrad, J. Lloret Fillol, H. Wadepohl, L. H. Gade,
1
1 1
Inorg. Chem. 2009, 48, 8523–8535.
3
ꢀ3
9.2027(15) ꢂ, V=6390.8(5) ꢂ , Z=8, d =1.321 Mg·m , Cu ra-
I
calcd
Ka
[
6] Selected key references for Ni complexes based on N-containing li-
ꢀ
1
diation, l=1.5418 ꢂ, m=1.200 mm , F =2712. T=110(1) K, q
000
gands: a) P. L. Holland, T. R. Cundari, L. L. Perez, N. A. Eckert, R. J. Lachi-
cotte, J. Am. Chem. Soc. 2002, 124, 14416–14424; b) E. Kogut, A. Zeller,
T. H. Warren, T. Strassner, J. Am. Chem. Soc. 2004, 126, 11984–11994;
c) S. Pfirrmann, C. Limberg, C. Herwig, R. Stçßer, B. Ziemer, Angew.
Chem. 2009, 121, 3407–3411; Angew. Chem. Int. Ed. 2009, 48, 3357–
3361; d) S. Wiese, P. Kapoor, K. D. Williams, T. H. Warren, J. Am. Chem.
Soc. 2009, 131, 18105–18111; e) S. Yao, Y. Xiong, C. Milsmann, E. Bill, S.
Pfirrmann, C. Limberg, M. Driess, Chem. Eur. J. 2010, 16, 436–439; f) S.
Yao, M. Driess, Acc. Chem. Res. 2012, 45, 276–287; g) S. Wiese, J. L.
McAfee, D. R. Pahls, C. L. McMullin, T. R. Cundari, T. H. Warren, J. Am.
Chem. Soc. 2012, 134, 10114–10121; h) C. Uyeda, J. C. Peters, Chem. Sci.
2013, 4, 157–163; i) B. Horn, C. Limberg, C. Herwig, B. Braun, Chem.
Commun. 2013, 49, 10923–10925; j) H. Gehring, R. Metzinger, C.
range 4.0 to 67.98. Index ranges h, k, l: ꢀ16…16, ꢀ18…18,
34…30. Reflections measured: 168170; independent: 11472
=0.208]; observed [I>2s(I)]: 8019. Final R indices [F >4s(F )]:
ꢀ
[R
int
o
o
2
R(F)=0.0631, wR(F )=0.1481, GooF=0.966, residual dens.=0.47,
ꢀ
3
ꢀ
0.76 eꢂ , abs. structure parm. ꢀ0.03(2). Data collection: Agilent
Technologies Supernova-E CCD diffractometer, microfocus X-Ray
tube, multilayer mirror optics (complexes 3a and 5a) or Bruker
AXS Smart 1000 CCD diffractometer, graphite monochromator
(
complex 4a). Lorentz, polarization and numerical (3a, 5a)/semi-
[22]
empirical absorption correction.
Structure solution: 3a: heavy
atom method combined with structure expansion by direct meth-
www.chemeurj.org 9664
Chem. Eur. J. 2014, 20, 9657 – 9665
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
Herwig, J. Intemann, S. Harder, C. Limberg, Chem. Eur. J. 2013, 19,
629–1636.
7] Selected key references for Ni complexes based on P-containing li-
[15] a) T. Fukuyama, M. Kobayashi, M. T. Rahman, N. Kamata, I. Ryu, Org. Lett.
2008, 10, 533–536; b) J. Wang, Z. Zhu, W. Huang, M. Deng, X. Zhou, J.
Organomet. Chem. 2008, 693, 2188–2192.
1
I
[
gands: a) D. A. Vicic, W. D. Jones, J. Am. Chem. Soc. 1999, 121, 7606–
[16] W. L. F. Armarego, C. L. L. Chai, Purification of Laboratory Chemicals,
Elsevier/Butterworth-Heinemann, 2009.
[17] G. R. Fulmer, A. J. M. Miller, N. H. Sherden, H. E. Gottlieb, A. Nudelman,
B. M. Stoltz, J. E. Bercaw, K. I. Goldberg, Organometallics 2010, 29, 2176–
2179.
7
4
617; b) D. J. Mindiola, G. L. Hillhouse, J. Am. Chem. Soc. 2001, 123,
623–4624; c) R. Melenkivitz, D. J. Mindiola, G. L. Hillhouse, J. Am.
Chem. Soc. 2002, 124, 3846–3847; d) D. A. Vicic, T. J. Anderson, J. A.
Cowan, A. J. Schultz, J. Am. Chem. Soc. 2004, 126, 8132–8133; e) Y.
Chen, C. Sui-Seng, D. Zargarian, Angew. Chem. 2005, 117, 7899–7903;
Angew. Chem. Int. Ed. 2005, 44, 7721–7725; f) A. L. Keen, M. Doster, S. A.
Johnson, J. Am. Chem. Soc. 2007, 129, 810–819; g) V. M. Iluc, G. L. Hill-
house, J. Am. Chem. Soc. 2010, 132, 11890–11892.
[18] T. Takeda, R. Sasaki, S. Yamauchi, T. Fujiwara, Tetrahedron 1997, 53, 557.
[19] Gaussian 09, Revision A.02, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E.
Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Men-
nucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian,
A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara,
K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, T. Vreven, J. A. Montgomery, J. E. Peralta., Jr., F. Ogliaro,
M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Ko-
bayashi, J. Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyen-
gar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B.
Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin,
K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg,
S. Dapprich, A. D. Daniels, ꢆ. Farkas, J. B. Foresman, J. V. Ortiz, J. Cio-
slowski, D. J. Fox, Gaussian, Inc., Wallingford CT, 2009.
[20] F. Neese, ORCA: An ab initio, Density Functional and Semiempirical Pro-
gram Package, Version 2.9.1 (MPI fꢇr Chemische Energiekonversion).
[21] F. Neese, J. Chem. Phys. 2001, 115, 11080.
[22] a) SAINT, Bruker AXS, Karlsruhe, 1997–2011; b) R. H. Blessing, Acta Crys-
tallogr. Sect. A 1995, 51, 33; c) G. M. Sheldrick, SADABS, Bruker AXS,
Karlsruhe, 2004–2008; d) CrysAlisPro, Agilent Technologies UK Ltd.,
Oxford 2011;e) SCALE3 ABSPACK, CrysAlisPro, Agilent Technologies UK
Ltd., Oxford 2011.
[
8] a) C. Eaborn, M. S. Hill, P. B. Hitchcock, J. D. Smith, Chem. Commun.
2000, 691–692; b) K. D. Kitiachvili, D. J. Mindiola, G. L. Hillhouse, J. Am.
Chem. Soc. 2004, 126, 10554–10555; c) E. Kogut, H. L. Wiencko, L.
Zhang, D. E. Cordeau, T. H. Warren, J. Am. Chem. Soc. 2005, 127, 11248–
11249; d) N. A. Eckert, A. Dinescu, T. R. Cundari, P. L. Holland, Inorg.
Chem. 2005, 44, 7702–7704.
[
9] a) A. D. Becke, Phys. Rev. A 1988, 38, 3098–3100; b) B. Miehlich, A.
Savin, H. Stoll, H. Preuss, Chem. Phys. Lett. 1989, 157, 200–206; c) A. D.
Becke, J. Chem. Phys. 1993, 98, 5648–5652.
[
10] a) A. J. H. Wachters, J. Chem. Phys. 1970, 52, 1033–1036; b) P. J. Hay, J.
Chem. Phys. 1977, 66, 4377–4384; c) R. Krishnan, J. S. Binkley, R. Seeger,
J. A. Pople, J. Chem. Phys. 1980, 72, 650–654; d) A. D. McLean, G. S.
Chandler, J. Chem. Phys. 1980, 72, 5639–5648; e) C. Lee, W. Yang, R. G.
Parr, Phys. Rev. B 1988, 37, 785–789; f) K. Raghavachari, G. W. Trucks, J.
Chem. Phys. 1989, 91, 1062–1065; g) R. C. Binning, L. A. Curtiss, J.
Comput. Chem. 1990, 11, 1206–1216; h) M. P. McGrath, L. Radom, J.
Chem. Phys. 1991, 94, 511–516; i) L. A. Curtiss, M. P. McGrath, J. P. Blau-
deau, N. E. Davis, R. C. Binning, L. Radom, J. Chem. Phys. 1995, 103,
6104–6113; j) J.-P. Blaudeau, M. P. McGrath, L. A. Curtiss, L. Radom, J.
Chem. Phys. 1997, 107, 5016–5021.
11] a) H. Buschmann, H.-D. Scharf, N. Hoffmann, P. Esser, Angew. Chem.
[23] a) P. T. Beurskens, G. Beurskens, R. de Gelder, J. M. M. Smits, S. Garcia-
Granda, R. O. Gould, DIRDIF-2008, Radboud University Nijmegen, The
Netherlands, 2008; b) P. T. Beurskens, in Crystallographic Computing 3
(Eds.: G. M. Sheldrick, C. Krꢇger, R. Goddard), Clarendon, Oxford, 1985,
p.216.
[
1991, 103, 480–518; Angew. Chem. Int. Ed. Engl. 1991, 30, 477–515;
b) T. Gçbel, K. B. Sharpless, Angew. Chem. 1993, 105, 1417–1418; Angew.
Chem. Int. Ed. Engl. 1993, 32, 1329–1331.
[
12] Nickel(II) chloride itself was found to act as a precatalyst for the hydro-
dehalogenation, most likely due to the formation of reactive nickel(0)
particles under the reaction conditions (therefore see: A. Roy, V. Srini-
vas, S. Ram, J. A. De Toro, J. P. Goff, J. Appl. Phys. 2006, 100, 094307).
13] J. Breitenfeld, R. Scopelliti, X. Hu, Organometallics 2012, 31, 2128–2136.
14] a) G. Brunton, D. Griller, L. R. C. Barclay, K. U. Ingold, J. Am. Chem. Soc.
[24] a) G. M. Sheldrick, SHELXD, University of Gçttingen and Bruker Nonius
2000–4; b) G. M. Sheldrick, H. A. Hauptman, C. M. Weeks, R. Miller, I.
Usꢅn in International Tables for Crystallography, Vol. F (Eds.: M. G. Ross-
mann, E. Arnold), IUCr/Kluwer, Dordrecht 2001, pp. 333–351.
[25] a) L. Palatinus, SUPERFLIP, EPF Lausanne, Switzerland 2007; b) L. Palati-
nus, G. Chapuis, J. Appl. Crystallogr. 2007, 40, 786.
[
[
1
976, 98, 6803–6811; b) D. Griller, K. U. Ingold, Acc. Chem. Res. 1980, 13,
[26] a) G. M. Sheldrick, SHELXL-2012, University of Gçttingen, 2013; b) G. M.
Sheldrick, Acta Crystallogr. Sect. A 2008, 64, 112.
317–323; c) B. C. Childress, A. C. Rice, P. B. Shevlin, J. Org. Chem. 1974,
39, 3056–3058; d) D. C. Nonhebel, Chem. Soc. Rev. 1993, 22, 347–359;
e) D. Zhu, I. Korobkov, P. H. M. Budzelaar, Organometallics 2012, 31,
958–3971.
3
Received: April 25, 2014
Chem. Eur. J. 2014, 20, 9657 – 9665
www.chemeurj.org
9665
ꢀ 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim