Carbon Halide Bond Activation of Benzyl Chloride and Benzyl Bromide
H-δoop), 705 (m, Ph-C-H-δoop), 722 (w), 736 (w), 752 (w), 799 (w), (5 mg, 10.2 μmol) or complex 3 (5 mg, 9.4 μmol) in an NMR tube
79 (vw), 999 (vw), 1027 (w), 1064 (w), 1132 (m), 1153 (vw), 1185 and the tubes were flame-sealed. According to NMR spectroscopy no
1
425 (m), 1445 (w), 1461 (w), 1486 (vw),1562 (w), 1613 (m), 1661 days at room temperature or upon heating the reaction mixtures to
(
m), 2874 (vw, νC–H), 2935 (vw, νC–H), 2976 (w, νC–H), 3060 (vw, νC–H). 80 °C for 2 hours.
1
3
H NMR (400 MHz, C
6
D
6
, 23 °C): δ = 1.23 (d, 12 H, JHH = 6.8 Hz,
3
iPr-CH
3
), 1.62 (d, 12 H, JHH = 6.8 Hz, iPr-CH
3
), 2.13 (s, 2 H, CH
2
),
3
6
.30 (sept, 4 H, JHH = 6.8 Hz, iPr-CH), 6.36 (s, 4 H, CHCH), 6.69 Crystallography
(m, 2 H, aryl-H), 6.89 (m, 1 H, aryl-H
p
), 6.97 (m, 2 H, aryl-H).
, 23 °C): δ = 10.4 (CH ), 22.6 (iPr-
),
1
3
1
Crystals were immersed in a film of perfluoropolyether oil on a glass
fiber and transferred to an Smart Apex-I diffractometer (Mo-K , 173
K, compound 2) equipped with a CCD area detector or a Stoe-IPDS I
C{ H} NMR (100 MHz, C
6
D
6
2
α
CH
3
), 24.4 (iPr-CH
3
), 52.0 (iPr-CH), 115.6 (NCCN), 116.3 (aryl-C
p
1
27.0 (aryl-Ctert), 128.1 (aryl-Ctert), 154.9 (aryl-C
i
), 186.4 (NCN).
α
image plate diffractometer (Mo-K , 203 K, compound 3), respectively.
trans-[Ni(iPr Im) (Br)(CH Ph)] (3):
2
2
2
A
suspension
of The structures were solved by direct methods and refined with the
(COD)] (1) (336 mg, 0.40 mmol) in hexane (100 mL) SHELXTL software package.[ All non-hydrogen atoms were refined
8]
[Ni (iPr Im)
2
2
4
was cooled to –78 °C and a solution of benzyl bromide (95 μL, anisotropically. Hydrogen atoms were assigned to idealized positions
0
.80 mmol) in hexane (75 mL) was added dropwise over a period of and were included in structure factor calculations. Extinction correc-
one hour. The reaction mixture was allowed to reach room temperature tions were applied as required.
overnight and was stirred for another 5 hours at room temperature.
Crystal Data for 2: C25
4 r
H39ClN Ni, M = 489.76, yellow plate, 0.30
Subsequently all volatiles were removed in vacuo. The residue was
suspended in hexane (20 mL), filtered, washed with hexane (10 mL)
and dried in vacuo. An orange colored powder was obtained in a yield
of 379 mg (89 %). Single crystals suitable for X-ray diffraction were
obtained by cooling a saturated solution of the compound in toluene
to –30 °C. Anal. Calcd. (found) for C25H39BrN Ni (534.20 g·mol ):
4
C 56.21 (55.85), H 7.36 (7.34), N 10.49 (10.46) %. EI/MS: m/z (%):
×
0.17 × 0.06 mm, monoclinic space group C2/c, a = 33.155(7) Å, b =
3
1
0.042(2) Å, c = 16.149(3) Å, β = 97.70(3)°, V = 5328.6(18) Å , Z =
, ρcalcd. = 1.221 g·cm , μ = 0.846 mm , F(000) = 2096, T = 173(2)
= 0.0592 and
–3
–1
8
1 2 1
K, all data: R = 0.0633 and wR = 0.1493, I > 2σ(I): R
–1
wR = 0.1432, Goof 1.290, 6638 independent reflections [2θ ≤ 56.7°]
2
and 356 parameters, 0 restraints. Some of the NHC isopropyl groups
+
+
were positionally disordered. C(5) and C(6) were refined with occu-
pancy factors of 65 % and 35 %, C(8) with occupancy factors of 77 %
and 23 %, and C(18) with occupancy factors of 83 % and 17 %. The
positionally disordered phenyl group of the benzyl ligand containing
C(31) to C(36) was refined with occupancy factors of 65 % and 35 %.
4
43 (78.7) [Ni(iPr
2
Im)
2
2
(Br)] , 362 (79.2) [Ni(iPr
2
Im)
2
] , 243 (62.1)
+
[Ni(CH CHHIm)(CH
2
Ph)] . IR (ATR): 403 (vw), 425 (vw), 450 (vw),
552 (vw), 580 (vw), 675 (w), 694 (vs, Ph-C-H-δoop), 703 (vs, Ph-C-
H-δoop), 735 (w), 752 (w), 802 (w), 880 (vw), 932 (vw), 1027 (w),
132 (w), 1176 (vw), 1214 (vs, NHC-γC–H), 1262 (vw), 1300 (w), 1370
m), 1392 (w), 1405 (w), 1424 (m), 1447 (vw), 1462 (vw), 1462 (vw),
1
(
1
4 7 8 r
Crystal Data for 3: (C25H39BrN Ni)(C H ), M = 626.36, yellow
486 (vw), 1594 (vw), 2872 (vw, νC–H), 2931 (vw, νC–H), 2971 (w,
1
block, 0.45 × 0.30 × 0.25 mm, monoclinic space group Pn, a =
10.423(2) Å, b = 10.878(2) Å, c = 15.098(3) Å, β = 102.57(3)°, V =
ν
C–H), 3089 (vw, νC–H), 3116 (vw, νC–H). H NMR (400 MHz, C
6
D
6
,
3
2
3 °C): δ = 1.21 (d, 12 H, JHH = 6.8 Hz, iPr-CH
3
), 1.61 (d, 12 H,
), 6.28 (sept, 4 H, JHH
3
–3
–1
3
3
1670.8(6) Å , Z = 2, ρcalcd. = 1.245 g·cm , μ = 1.801 mm , F(000) =
60, T = 203(2) K, all data: R = 0.0599 and wR = 0.1325, I > 2σ(I):
= 0.0496 and wR = 0.1251, Goof 1.023, 5931 independent reflec-
J
HH = 6.8 Hz, iPr-CH
3
), 2.22 (s, 2 H, CH
2
=
6
1
2
6
3
2
(
(
.8 Hz, iPr-CH), 6.36 (s, 4 H, CHCH), 6.67 (m, 2 H, aryl-H), 6.93 (m,
1
3
1
R
1
2
H, aryl-H). C{ H} NMR (100 MHz, C
2.7 (iPr-CH ), 24.0 (iPr-CH ), 52.0 (iPr-CH), 115.9 (NCCN), 116.6
), 121.1 (aryl-Ctert), 127.1 (aryl-Ctert), 154.5 (aryl-C ), 186.1
6 6 2
D , 23 °C): δ = 13.1 (CH ),
tions [2θ ≤ 61.7°] and 332 parameters, 2 restraints. Racemic twin re-
finement using the BASF and TWIN commands of SHELXTL has
been used (BASF/Flack Parameter x = 0.54039).
3
3
aryl-C
NCN).
p
i
Crystallographic data for the structures reported in this paper have
been deposited with the Cambridge Crystallographic Data Centre as
supplementary publication no.s CCDC-819561 (compound 2) and to
CCDC-819562 (compound 3). Copies of the data can be obtained free
of charge on application to CCDC, 12 Union Road, Cambridge, CB2
General procedure for the cross-couplings of the benzyl halides
with phenylboronic acid: The results obtained for the cross-coupling
reactions of benzyl chloride and benzyl bromide, especially the bases
applied, are summarized in Table 1. In a typical experiment phenylbo-
ronic acid (656 mg, 5.37 mmol, 1.1 equivalents), catalyst 1 (50 mg,
1EZ, UK (Fax: *44-1223/336-033; E-mail: deposit@ccdc.cam.ac.uk).
5
9.5 μmol, 1.22 mol-%) and the corresponding base (14.64 mmol, 3.0
equivalents: 1.64 g KOtBu, 3.11 g K PO , 851 mg KF, 2.22 g CsF and
.77 g Cs CO ) were suspended in toluene (20 mL). After addition
3
4
4
2
3
Acknowledgement
of benzyl chloride (561 μL, 4.88 mmol, 1.0 equivalents) the reaction
mixture was heated to 110 °C in periods of 60 minutes, cooled with
the use of liquid nitrogen and a GC sample was taken. The reactions
using 3.0 equivalents phenylboronic acid (14.64 mmol, 1.785 g) and
the reaction using benzyl bromide (4.88 mmol, 1.0 equivalents,
We are grateful for financial support of the Deutsche Forschungsge-
meinschaft (DFG), the University of Karlsruhe (TH), and the Julius-
Maximilians-University Würzburg. T. Z. acknowledges a scholarship
of the Landesgraduiertenförderung Baden-Württemberg. We thank Dr.
Stephan Wagner for his technical assistance using GC–MS.
5
80 μL) instead of benzyl chloride were performed using the same
+
procedure. The GC–MS analysis revealed the [M] peaks at m/z = 154
(
biphenyl), 168 (diphenylmethane), 164 (benzyl tert-butyl ether), 182
(1,2-diphenylethane) at retention times of 9.218 min, 9.547 min,
References
7.635 min and 10.125 min, respectively.
[
1] a) P. J. Stang, F. Diederich, Metal-Catalyzed Cross-Coupling Reac-
tions, Wiley-VCH, Weinheim, Germany, 1998; b) N. Miyaura,
Cross-Coupling Reactions, A Practical Guide, Topics in Current
Chemistry 219, Springer, Berlin, Germany, 2002; c) A. de Meijere,
Reactions of trans-[Ni(iPr Im) (Cl)(CH
2
2
2
Ph)] (2) and trans-
(0.8 mL)
[
Ni(iPr Im) (Br)(CH Ph)] (3) with an excess CsF: C
2
2
2
6 6
D
was added to a mixture of CsF (152 mg, 1.00 mmol) and complex 2
Z. Anorg. Allg. Chem. 2011, 1858–1862
© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.zaac.wiley-vch.de
1861