Arylcalcium halides as substrates in Kumada-type cross-coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2013.07.022

A precondition of a Kumada-type cross-coupling reaction with arylcalcium halides is the easy availability of these organometallics. Arylcalcium halides are accessible with high yields via reduction of arylhalides with activated calcium in ethers such as tetrahydrofuran. In order to demonstrate the generality of this Grignard-type reduction of haloarenes, [(4-BrC ₆H₄)CaI(thf)₄] (1) and [(β-naphthyl) CaBr(thf)₄] (2) are prepared. First investigations regarding arylcalcium halides as substrates in cross-coupling reactions are undertaken choosing [(C₆H₅)CaI(thf)₄] (3) and [(4-CH ₃C₆H₄)CaI(thf)₄] (4) as the organometallic substrate in a cross-coupling with chlorobenzene and 4-chlorotoluene. The nickel-mediated conversion of arylcalcium iodides and chloroarenes to (substituted) biphenyls proceeds with moderate yields and significant amounts of homo-coupling products are observed.

Full text of DOI:10.1016/j.jorganchem.2013.07.022

Journal of Organometallic Chemistry 751 (2014) 563e567
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Arylcalcium halides as substrates in Kumada-type cross-coupling
reactions
*
Jens Langer, Mathias Köhler, Helmar Görls, Matthias Westerhausen
Institute of Inorganic and Analytical Chemistry, Friedrich Schiller University Jena, Humboldtstrasse 8, D-07743 Jena, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
A precondition of a Kumada-type cross-coupling reaction with arylcalcium halides is the easy availability
of these organometallics. Arylcalcium halides are accessible with high yields via reduction of arylhalides
with activated calcium in ethers such as tetrahydrofuran. In order to demonstrate the generality of this
Received 4 June 2013
Received in revised form
3 July 2013
Grignard-type reduction of haloarenes, [(4-BrC6H4)CaI(thf)4] (1) and [(b-naphthyl)CaBr(thf)4] (2) are
Accepted 5 July 2013
prepared. First investigations regarding arylcalcium halides as substrates in cross-coupling reactions are
undertaken choosing [(C6H5)CaI(thf)4] (3) and [(4-CH3C6H4)CaI(thf)4] (4) as the organometallic substrate
in a cross-coupling with chlorobenzene and 4-chlorotoluene. The nickel-mediated conversion of aryl-
calcium iodides and chloroarenes to (substituted) biphenyls proceeds with moderate yields and signif-
icant amounts of homo-coupling products are observed.
Keywords:
Grignard reagents
Calcium
Arylcalcium halides
Cross coupling
Ó 2013 Elsevier B.V. All rights reserved.
Nickel-mediated catalysis
Kumada-type cross-coupling
1. Introduction
In contrast to the related benzylcalcium and allylcalcium de-
rivatives [5], the potential of arylcalcium reagents in organic syn-
Calcium-based organometallics are currently gaining impor-
tance due to many factors [1]. First of all, suitable minerals for the
calcium production are widespread and available in enormous
quantities; guaranteeing its worldwide accessibility at low prices.
Furthermore, the calcium cation is considered non-toxic regardless
of its concentration [2], making calcium-based reagents and cata-
lysts an interesting choice for the synthesis of drugs and other
compounds with potential medical applications, since residual
calcium contents in the products do not add health risks and
therefore do not have to be removed. Consequently, calcium-based
catalysis attracted much attention and led to the development
of calcium-mediated hydroamination, hydrosilylation, hydro-
phosphanylation, and other catalytic processes in recent years [3].
The attractiveness of organocalcium reagents is also based on
the low electronegativity (comparable to lithium leading to very
heteropolar CaeC bonds with a high reactivity) and the possibility
of d-orbital participation (comparable to early transition metals
with catalytic activity). In case of arylcalcium derivatives, im-
provements of the direct Grignard-type synthesis and refined
protocols for subsequent derivatizations led to a tremendous
development of their organocalcium chemistry [4].
theses remained almost uninvestigated. Only one example of a
directed ortho-metalation reaction [6] and one of an oligomeriza-
tion reaction of nitriles involving arylcalcium compounds have been
briefly mentioned [7]. Here we investigate if arylcalcium halides can
serve as substrates in nickel-catalyzed Kumada-type cross-coupling
reactions. In general nickel-mediated cross-coupling reactions
represent a powerful tool for the formation of CeC bonds involving
sp2- and also sp3-hybridized carbon atoms [8,9]. Typically, in the
presence of catalytic amounts of Ni0 (or Pd0) complexes the reaction
of the Grignard reagent R-Mg-X with R0-X yields ReR0. The reaction
mechanism of this Kumada-type coupling is discussed in detail in
several general text books and reviews [10,11].
2. Results and discussion
2.1. Availability of arylcalcium halides
The use of arylcalcium halides as substrates in organic synthesis
requires a straight forward approach to these calcium-based re-
agents. Although the synthesis of first derivatives via a Grignard-
analogous reaction dates back to the beginning of the 20th cen-
tury [12], reliable and easily applicable protocols based on those
early results were just developed within the last decade [13] and
recently refined to overcome existing limitations e.g. in case of
halosubstituted polycyclic aromatic carbons as substrates [14].
* Corresponding author.
E-mail address: m.we@uni-jena.de (M. Westerhausen).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.07.022

564
J. Langer et al. / Journal of Organometallic Chemistry 751 (2014) 563e567
Finely divided calcium powders, generated by dissolution of the
bulk metal in ammonia and subsequent reduction of the resulting
solution to dryness, are nowadays commonly used and allow the
synthesis of a variety of arylcalcium iodides and bromides [4].
Doubly metalated derivates are also accessible [15]. Chloroarenes
are not suitable as substrates for Grignard-type reactions with
activated calcium, in contrast to magnesium. THF and THP are the
most commonly used solvents. In order to demonstrate the gen-
erality of this Grignard-type reduction of haloarenes, we prepared
[(4-BrC6H4)CaI(thf)4] (1) and [(b-naphthyl)CaBr(thf)4] (2) showing
that even halogeno-substituted arylcalcium halides are accessible
by this procedure (Scheme 1).
The molecular structures and numbering schemes of [(4-BrC6H4)
CaI(thf)4]$0.5 THF (1) and [(
in Figs. 1 and 2. In contrast to the closely related derivatives [(
naphthyl)Ca( -Br)(thf)3]2 [16] and [(phenanthryl)Ca( -Br)(thf)3]2
b-naphthyl)CaBr(thf)4] (2) are depicted
a-
m
m
[14b], compound 2 is monomeric in solid state as it was also
observed for [(C6H5)CaBr(thf)4] [17] and [(phenanthryl)CaBr(thp)4]
[14b]. In 1 and 2, the aryl group and the halide ion are trans-arranged
due to electrostatic reasons. The structure of 2 contains a crystal-
lographic mirror plane containing the naphthylcalcium-bromide
fragment. The CaeC bond lengths of 257.2 (6) and 256.9 (5) pm lie
in the expected region [4].
For our first investigations regarding arylcalcium halides as
substrates in cross-coupling reactions we have chosen [(C6H5)
CaI(thf)4] (3) [17] and [(4-CH3C6H4)CaI(thf)4] (4) [17] in order to
limit side-reactions caused by any functional groups.
Fig. 1. Molecular structure and numbering scheme of [(4-BrC6H4)CaI(thf)4]$0.5 THF
(1). The ellipsoids represent a probability of 40%, H atoms are omitted for clarity
reasons. In addition, the THF molecule in the gap between the calcium-based organ-
ometallics is neglected. Selected bond lengths (pm): Ca1eC1 257.2(6), Ca1eI1
311.81(12), Ca1eO1 238.2(4), Ca1eO2 235.0(4), Ca1eO3 243.3(9), Ca1eO4 239.7(4),
Br1eC4 194.8(7); angle (deg.): C1eCa1eI1 173.59(14).
2.2. Nickel-mediated cross-coupling reaction with arylcalcium
iodides
of 62% and 67% of the haloarenes after 24 h and yielded the cor-
responding symmetric products biphenyl and 4,40-dimethylbi-
phenyl in yields of 56% and 52%, respectively. Although complete
conversion of the halobenzenes was not anticipated because 10% of
the arylcalcium reagent is expected to be consumed in the activa-
tion process of the precatalyst, the observed conversion is signifi-
In absence of a suitable nickel- or palladium-based catalyst,
[(C6H5)CaI(thf)4] (3) does not react with chlorobenzene to form
biphenyl in a Wurtz-type reaction (Table 1, entry 1). The corre-
sponding experiment with iodobenzene (Table 1, entry 2) did not
result in biphenyl formation either [18], although biphenyl was
observed as a by-product in the synthesis of 3 in an earlier investi-
gation [19]. In order to confirm this fact, the mother liquor of the
synthesis of 3 was hydrolyzed, extracted with chloroform and
analyzed by gas chromatography. Biphenyl and unreacted iodo-
benzene are the only high boiling by-products observed. Together
with the above mentioned experiment, it can be concluded that this
biphenyl formation is rather the result of a reaction of metallic
calcium and iodobenzene than of a reaction betweenphenylcalcium
iodide and iodobenzene. It is likely that its formation is closely
related to the radical conditions of the Grignard-type reaction.
The catalytic coupling experiments were performed in 0.1M
solution of the arylcalcium iodides [(C6H5)CaI(thf)4] (3) or [(4-
CH3C6H4)CaI(thf)4] (4) in THF with equimolar amounts of either
chlorobenzene or 4-chlorotoluene. [(dppp)NiCl2] [dppp ¼ 1,3-
bis(diphenylphosphanyl)-propane] was employed as the pre-
catalyst (see Scheme 2 and Table 1).
cantly lower than the achievable mark of 90%.
A possible
explanation is the known instability of arylcalcium reagents in THF
at ambient temperature. It was reported that around 15% of
tolylcalcium iodide decomposes within 24 h in THF at room tem-
perature via solvent degradation reactions [14a]. The performed
cross-coupling experiments of phenylcalcium iodide
3 with
4-chlorotoluene led to the formation of all possible biphenyl de-
rivatives, namely biphenyl, 4-methylbiphenyl, and 4,40-dime-
thylbiphenyl with
a ratio of 23:23:5. In a complementary
experiment, using 4 and chlorobenzene (see Table 1, entry 5), the
three products were detected in a ratio of 7:32:21. In both cases, the
desired product 4-methylbiphenyl is accompanied by large
amounts of the homo-coupling product derived from the arylcal-
cium component of the reaction. Part of these homo-coupling
products stems from the activation of the precatalyst [(dppp)
NiCl2] by arylcalcium iodide yielding [(dppp)Ni(Ar)2] followed by
the reductive elimination of biphenyls and formation of catalyti-
cally active Ni0 species. The contribution of this activation reaction
to the overall formation of homo-coupling products can be
minimized by reduction of the catalyst loading. However, the
Using 5 mol% of [(dppp)NiCl2], the nickel-mediated homo-
coupling of phenylcalcium iodide with chlorobenzene as well as of
4-tolylcalcium iodide with 4-chlorotoluene gave conversion rates
I
O
O
O
O
O
Br
Br
Ca Br
Ca*
Br
Ca
O
I
THF
THF
O
O
1
2
Scheme 1. Syntheses of 1 and 2.

J. Langer et al. / Journal of Organometallic Chemistry 751 (2014) 563e567
565
reactivities similar to their lithium congeners and the ability of
arylcalcium iodides to transfer aryl groups to transition metals is
well documented [24].
3. Conclusion and perspective
Arylcalcium halides are easily accessible substrates for catalytic
coupling reactions. These organometallics can be prepared via the
reduction of iodoarenes in THF; even bromo substituents and fused
aromatic systems represent useful substrates in this Grignard-type
reaction. Thus, [(4-BrC6H4)CaI(thf)4] (1) and [(b-naphthyl)CaBr(thf)4]
(2) were prepared by this procedure.
[(C6H5)CaI(thf)4] (3) and [(4-CH3C6H4)CaI(thf)4] (4) were chosen
for initial testing of the suitability of these substrates in Kumada-
type homo- and cross-coupling reactions with chlorobenzene and
4-chlorotoluene. In all catalytic cross-coupling reactions all
possible products biphenyl, 4-methylbiphenyl and 4,40-dime-
thylbiphenyl were detected. This finding was ascribed to the in-
termediate formation of tetraarylnickelate anions.
Summarizing the catalytic nickel-mediated Kumada-type cross
coupling with arylcalcium iodides and chloroarenes being the
substrates the following conclusions can be drawn:
Fig. 2. Molecular structure and numbering scheme of [(b-naphthyl)CaBr(thf)4] (2). The
ellipsoids represent a probability of 40%, H atoms are not shown for the sake of clarity.
The molecule contains a mirror plane (ꢀ, -y, z) and symmetry-related atoms are
marked with the letter “A”. Selected bond lengths (pm): Ca1eC1 256.9(5), Ca1eBr1
298.96(8), Ca1eO1 238.8(2), Ca1eO2 237.1(2); angle (deg.): C1eCa1eBr1 173.56 (12).
1. Without nickel-mediated catalysis arylcalcium iodides do not
react with chloroarenes or iodoarenes in
coupling reaction.
2. The nickel-mediated conversion of arylcalcium iodides and
chloroarenes to (substituted) biphenyls proceeds with moder-
ate yields.
a Wurtz-type
employment of only 0.5 mol% catalyst just halves the overall
product yield with an insignificant improvement of the selectivity
of the system (Table 1, entry 7).
In order to gain further information on the catalysis, the reaction
mixture of run 6 was investigated after 24 h by 31P{H} NMR mea-
surement. Surprisingly, only one phosphorus containing species
3. The selectivity of the cross-coupling is rather poor and signif-
icant amounts of homo-coupling products are found.
was detected. The observed singlet at
d 11.8 (THF/d8-THF) was
assigned to [(dppp)2Ni] in agreement with the literature value [20].
This assignment was further confirmed by comparison with an
authentic sample, independently prepared from [(cod)2Ni]
(cod ¼ 1,5-cyclooctadiene) and two equivalents of dppp.
Due to the rather large difference in electronegativity between
strongly electropositive calcium (AllredeRochow electronegativity
EN: 1.04 [21]) and nickel (EN: 1.75 [21]), the observed lacking
selectivity of the catalytic system and the detection of [(dppp)2Ni],
it can be assumed that the investigated catalysis does not proceed
via the commonly accepted mechanism. Instead of neutral nick-
el(II) and nickel(0) compounds, we propose the formation of cal-
cium nickelates as key intermediates of the system according to
Scheme 3.
4. Experimental
4.1. General comments
All manipulations were carried out under an inert argon at-
mosphere using standard Schlenk techniques. THF was dried over
KOH and distilled over sodium/benzophenone in an argon atmo-
sphere; deuterated THF was dried over sodium, degassed, and
saturated with argon. The yields given are not optimized. 1H and 13
C
{1H} NMR spectra were recorded on Bruker AC 200, AC 400, or AC
600 spectrometers. Chemical shifts are reported in parts per million
relative to Me4Si as an external standard. The residual signals of
[D8]THF were used as an internal standard. Data are reported as
follows: s ¼ singlet; m ¼ multiplet; br ¼ broad.
Similar compounds of other s-block metals e.g. [{(thf)2Li}2{(m-
Ph)4Ni}] are well documented [22]. Furthermore, this lithium
complex is known to undergo reductive elimination of biphenyl in
presence of phenyllithium [23] and it was shown that it is an
active but rather unselective catalyst in Kumada-type cross-
coupling reactions even in absence of supporting neutral phos-
phane ligands [22b]. Arylcalcium iodides have properties and
Gas chromatographic investigation was performed on a Varian
CP-3800 gas chromatograph equipped with a Varian CP8410
autoinjector and
15 m ꢀ 0.25 mm ID.
a FactorFour Capillary Column VF-1 ms,
Calcium was activated by dissolution in liquid NH3 and subse-
quent reduction of the deep blue solution to dryness, resulting in
Table 1
Coupling experiments of arylcalcium iodides and haloarenes.
Entry
Arylcalcium iodide
Substrate
Catalyst [mol %]
Conversion of haloarene
Yield [%]a 5a
Yield [%]a 5b
Yield [%]a 5c
1
2
3
4
5
6
7
3
3
3
4
4
3
3
PhCl
PhI
0
0
5
5
5
5
0.5
<1
<5
62
67
70
56
30
e
e
e
e
e
52
21
5
e
e
PhCl
TolClb
PhCl
TolClb
TolClb
56
e
e
e
7
23
10
32
23
12
3
a
GC yields using mesitylene as an internal standard.
TolCl ¼ 4-chlorotoluene.
b

566
J. Langer et al. / Journal of Organometallic Chemistry 751 (2014) 563e567
thf thf
Ca
thf thf
cat.: [(dppp)NiCl2]
R
I
Cl
R'
R
R'
THF, 24h, r.t.
-[(thf)4CaICl]
5a: R, R' = H
5b: R = H, R' = CH3
5c: R, R' = CH3
3: R = H
4: R = CH3
R' = H, CH3
Scheme 2. Cross-coupling reaction of arylcalcium iodides and chloroarenes.
finely divided calcium powders. The complexes [(C6H5)CaI(thf)4]
(3) and [(4-CH3C6H4)CaI(thf)4] (4) were prepared according to
known procedures [17] and recrystallized from THF before use. The
precatalyst [(dppp)NiCl2] was prepared as reported previously
[25]. Chlorobenzene and 4-chlorotoluene were obtained from
commercial sources, dried over calcium hydride and distilled
before use.
The calcium content of the products was determined by com-
plexometric titration of a hydrolyzed aliquot with 0.05 M EDTA
using Eriochrome BlackT as the indicator [26].
extracted with THF (40 mL) and discarded afterward. The com-
bined THF solutions (67.4% yield of organocalcium compounds,
determined by acid consumption by a hydrolyzed aliquot) were
stored at ꢁ40 ꢂC for 2 days. The precipitated crystalline solid was
collected on a cooled Schlenk frit and dried in vacuo. Yield of 2:
1.10 g (2.07 mmol, 17.9%) crude product, containing a very small
amount of a dark violet impurity. Anal. Calcd. for C26H39CaBrO4
(535.58 g molꢁ1): Ca 7.48%; found: Ca 7.15%. 1H NMR ([D8]THF,
400 MHz):
d 1.77 (m, 12H, CH2 thf), 3.62 (m, 12H, OCH2 thf), 7.05
(m, 1H, CH), 7.12 (m, 1H, CH), 7.31 (m, 1H, CH), 7.51 (m, 2H, CH),
7.99 (m, 1H, CH), 8.19 (br, 1H, CH). 13C NMR ([D8]THF, 100.6 MHz):
d
26.3 (8C, CH2 thf), 68.1 (8C, OCH2 thf), 122.1 (1C, CH), 122.2 (1C,
4.2. Synthesis of [(4-BrC6H4)CaI(thf)4] (1)
CH), 123.3 (1C, CH), 127.4 (1C, CH), 127.8 (1C, CH), 132.8 (1C, C),
133.8 (1C, C), 139.7 (1C, CH), 141.1 (1C, CH), 189.7 (1C, CeCa).
Suitable colorless crystals for X-ray diffraction experiments of the
Activated calcium (1.20 g, 29.9 mmol) was suspended in
tetrahydrofuran (32 mL) and 4-bromo-iodobenzene (7.07 g,
25.0 mmol) was added at ꢁ20 ꢂC. The resulting suspension was
shaken for 1 h at 0 ꢂC, warmed to ambient temperature and
shaken for additional 4 h at this temperature. Thereafter, residual
calcium was removed by filtration using a Schlenk frit covered
with diatomaceous earth. The conversion (66.0%) was determined
by acidimetric titration of an aliquot of the resulting brown so-
lution. The mother liquor was stored at ꢁ40 ꢂC for 4 days. The
formed colorless crystals were isolated by filtration and were
dried in vacuo. Yield of 1: 2.89 g (4.73 mmol, 18.9%). Anal. Calcd.
for C22H36CaIBrO4 (611.41 g molꢁ1): Ca 6.56%; found: Ca 6.90%. 1H
composition [(b-Naph)Ca(Br)(thf)4] were obtained by recrystalli-
zation from THF at ꢁ40 ꢂC.
4.4. Coupling reaction (typical procedure)
The arylcalcium iodide (2 mmol) was dissolved in THF
(20 mL). Afterward, the chlorosubstituted arene (2 mmol), solid
[(dppp)NiCl2] (0.1 mmol) as catalyst and mesitylene (100 mL) as
internal standard were added to the solution in that order. The
resulting reaction mixture was stirred for 24 h at ambient
temperature. Thereafter, a sample of the solution was hydro-
lyzed with 2 M hydrochloric acid (2 mL) and extracted with
n-heptane (1 mL). The organic phase was analyzed by gas
chromatography.
NMR ([D8]THF, 600 MHz):
d 1.77 (m, 16H, CH2 thf), 3.63 (m, 16H,
OCH2 thf), 6.96 (AA0 part of an AA0BB0 spin system, 2H, CH), 7.61
(BB0 part of an AA0BB0 spin system, 2H, CH). 13C{1H} NMR ([D8]THF,
150.9 MHz):
d 26.3 (8C, CH2 thf), 68.2 (8C, OCH2 thf), 117.9 (1C, Ce
Br), 127.8 (2C, CH), 143.0 (2C, CH), 188.5 (1C, CeCa). Suitable
crystals for X-ray diffraction experiments of the composition [(4-
Br-C6H4)Ca(I)(thf)4] ∙ 0.5 THF were obtained by recrystallization
from THF at ꢁ40 ꢂC.
4.5. Crystal structure determinations
The intensity data for the compounds were collected on a
Nonius KappaCCD diffractometer using graphite-monochromated
Mo-Ka radiation. Data was corrected for Lorentz and polarization
effects but not for absorption effects [27,28].
4.3. Synthesis of [(b-naphthyl)CaBr(thf)4] (2)
Finely divided calcium (0.58 g, 14.5 mmol) was suspended in
The structures were solved by direct methods (SHELXS [29]) and
refined by full-matrix least squares techniques against F02 (SHELXL-
97 [29]). All hydrogen atoms were included at calculated positions
with fixed thermal parameters. All non-disordered, non-hydrogen
atoms were refined anisotropically [29]. Crystallographic data as
well as structure solution and refinement details are summarized
in Table 2. XP (SIEMENS Analytical X-ray Instruments, Inc.) was
used for structure representations.
20 mL of THF and the suspension was cooled to ꢁ20 ꢂC. At this
temperature 2.40 g (11.6 mmol) of
b-bromonaphthalene and
0.21 g (0.81 mmol) of iodine were added and the mixture was
warmed to 0 ꢂC while shaking. After 1 h at 0 ꢂC the reaction
mixture was shaken for additional 5 h at ambient temperature.
The resulting dark violet mixture was filtered through a Schlenk
frit covered with diatomaceous earth. The solid residue was
2-
Ph2
P
Ni
Ph2
P
Ni
+
Ph2
P
thf thf
thf thf
Ca
thf thf
Cl
Cl
THF
+
6
2
thf Ca
I
I
Ni
P
- 4 [(thf)4CaICl]
- Biphenyl
thf thf
Ph2
P
P
2
Ph2
Ph2
Scheme 3. Proposed formation of calcium nickelates.

J. Langer et al. / Journal of Organometallic Chemistry 751 (2014) 563e567
567
Table 2
Heidelberg. (b) M. Westerhausen, Z. Anorg. Allg. Chem. 635 (2009) 13e32;
(c) M. Westerhausen, Coord. Chem. Rev. 252 (2008) 1516e1531;
(d) M. Westerhausen, M. Gärtner, R. Fischer, J. Langer, L. Yu, M. Reiher, Chem.
Eur. J. 13 (2007) 6292e6306;
Crystal data and refinement details for the X-ray structure determinations of [(4-
BrC6H4)CaI(thf)4]$0.5 THF (1) and [(b-naphthyl)CaBr(thf)4] (2).
Compound
1
2
(e) M. Westerhausen, M. Gärtner, R. Fischer, J. Langer, Angew. Chem. Int. Ed.
46 (2007) 1950e1956. Angew. Chem. 2007, 119, 1994e2001.
[5] (a) P. Jochmann, V. Leich, T.P. Spaniol, J. Okuda, Chem. Eur. J. 17 (2011) 12115e
12122;
Formula
fw (g mol-1
T/ꢂC
C22H36BrCaIO4* 0.5C4H8O
647.45
C26H39BrCaO4
535.56
ꢁ140 (2)
Monoclinic
C m
12.1895 (5)
13.4158 (4)
8.3097 (3)
90
100.350 (2)
90
)
ꢁ140 (2)
(b) P. Jochmann, T.S. Dols, T.P. Spaniol, L. Perrin, L. Maron, J. Okuda, Angew.
Chem. Int. Ed. 49 (2010) 7795e7798;
Crystal system
Space group
Triclinic
ꢀ
P ı
(c) D.F.-J. Piesik, K. Häbe, S. Harder, Eur. J. Inorg. Chem. (2007) 5652e5661;
(d) S. Harder, Angew. Chem. Int. Ed. 43 (2004) 2714e2718;
(e) F. Feil, S. Harder, Eur. J. Inorg. Chem. 18 (2003) 3401e3408;
(f) F. Feil, C. Müller, S. Harder, J. Organomet. Chem. 683 (2003) 56e63.
[6] R. Fischer, M. Gärtner, H. Görls, L. Yu, M. Reiher, M. Westerhausen, Angew.
Chem. Int. Ed. 46 (2007) 1618e1623. Angew. Chem. 2007, 119, 1642e1647.
[7] M. Gärtner, H. Görls, M. Westerhausen, Organometallics 26 (2007) 1077e1083.
[8] K. Tamao, K. Sumitani, Y. Kiso, M. Zembayashi, A. Fujioka, S.-I. Kodama,
I. Nakajima, A. Minato, M. Kumada, Bull. Chem. Soc. Jpn. 49 (1976)
1958e1969.
ꢁ
a/A
9.4871 (3)
11.7654 (3)
12.6768 (3)
91.907 (2)
97.181 (1)
96.539 (1)
1393.13 (7)
2
ꢁ
b/A
ꢁ
c/A
ꢂ
ꢂ
a
/
b
/
ꢂ
g
/
3
ꢁ
V/A
1336.79 (8)
2
1.331
Z
r
(g cmꢁ3
(cmꢁ1
)
1.543
27.95
[9] Selected reviews: (a) S.P. Stanforth, Tetrahedron 54 (1998) 263e303;
(b) K. Tamao, N. Miyaura, Top. Curr. Chem. 219 (2002) 1e9;
(c) N. Yoshikai, H. Mashima, E. Nakamura, J. Am. Chem. Soc. 127 (2005)
17978e17979;
m
)
17.57
Measured data
9075
3774
Data with I > 2
s(I)
5434
2450
Unique data/Rint
6260/0.0228
0.1658
0.0657
2494/0.0203
0.0752
0.0275
(d) P. Knochel, T. Thaler, C. Diene, Isr. J. Chem. 50 (2010) 547e557;
(e) K. Tamao, J. Organomet. Chem. 653 (2002) 23e26;
(f) E.-I. Negishi, Q. Hu, Z. Huang, G. Wang, N. Yin, in: Z. Rappoport, I. Marek
(Eds.), The Chemistry of Organozinc Compounds, Part 1, Wiley, Chichester,
2006, pp. 457e553 (Chapter 11);
wR2 (all data, on F2)a
R1 (I > 2
s
(I))a
sb
1.070
1.121
ꢁꢁ3
Res. dens./e A
CCDC No.
2.367/ꢁ1.326
0.351/ꢁ0.490
(g) S. Lin, T. Agapie, Synlett (2011) 1e5;
942049
942050
(h) P. Kumar, J. Louie, Angew. Chem. Int. Ed. 50 (2011) 10768e10769;
(i) Z.-X. Wang, N. Liu, Eur. J. Inorg. Chem. (2012) 901e911.
[10] See e.g.: (a) J.P. Collman, L.S. Hegedus, J.R. Norton, R.G. Finke, Principles and
Applications of Organotransition Metal Chemistry, University Science Books,
Mill Valley CA, 1987;
P
Definition of the R indices: R1 ¼ (SrrFor ꢁ rFcrr)/SrFor; wR2
¼
f
½wðFo2 ꢁ Fc2Þ2ꢃ=
a
P
½wðFo2Þ2ꢃg1=2with wꢁ1
¼
s2ðFo2Þ þ ðaPÞ2 þ bP; P ¼ ½2Fc2 þ MaxðFo2Þꢃ=3:
P
s ¼ f ½wðFo2 ꢁ Fc2Þ2ꢃ=ðNo ꢁ NpÞg1=2
.
b
(b) C. Elschenbroich, Organometallics, third ed., Wiley-VCH, Weinheim, 2005;
(c) D. Steinborn, Grundlagen der metallorganischen Komplexkatalyse, Teub-
ner, Wiesbaden, 2007;
(d) J. Hartwig, Organotransition Metal Chemistry: from Bonding to Catalysis,
University Science Books, Sausalito CA, 2010.
[11] B.M. Rosen, K.W. Quasdorf, D.A. Wilson, N. Zhang, A.-M. Resmerita, N.K. Garg,
V. Percec, Chem. Rev. 111 (2011) 1346e1416.
Acknowledgment
[12] E. Beckmann, Chem. Ber. 38 (1905) 904e906.
M.K. is grateful to the Fonds der Chemischen Industrie (Frankfurt/
Main, Germany) for a generous Ph.D. stipend. We also appreciate the
financial support of the Verband der Chemischen Industrie (VCI/FCI,
Frankfurt/Main, Germany). Infrastructure of our institute was pro-
vided by the EU (European Regional Development Fund, EFRE) and
the Friedrich Schiller University Jena. We acknowledge the support
of Mr. J. Ahner in the frame of an advanced laboratory course.
[13] M. Gärtner, H. Görls, M. Westerhausen, Synthesis (2007) 725e730.
[14] (a) J. Langer, M. Köhler, R. Fischer, F. Dündar, H. Görls, M. Westerhausen,
Organometallics 31 (2012) 6172e6182;
(b) M. Köhler, J. Langer, R. Fischer, H.Görls, M.Westerhausen, Chem. Eur. J.,
DOI: 10.1002/chem.201301152.
[15] J. Langer, H. Görls, M. Westerhausen, Inorg. Chem. Commun. 10 (2007)
853e855.
[16] M. Gärtner, H. Görls, M. Westerhausen, J. Organomet. Chem. 693 (2008)
221e227.
[17] R. Fischer, M. Gärtner, H. Görls, M. Westerhausen, Organometallics 25 (2006)
3496e3500.
Appendix A. Supplementary material
[18] In related experiments, the coupling of two allyl moities at calcium was
observed upon addition of I2 to bis(allyl)calcium: (a) P. Jochmann, S. Maslek,
T.P. Spaniol, J. Okuda, Organometallics 30 (2011) 1991e1997;
(b) P. Jochmann, T.S. Dols, T.P. Spaniol, L. Perrin, L. Maron, J. Okuda, Angew.
Chem. Int. Ed. 48 (2009) 5715e5719. Angew. Chem. 2009, 121, 5825e5829.
[19] R. Fischer, H. Görls, M. Westerhausen, Inorg. Chem. Commun. 8 (2005)
1159e1161.
CCDC 942049 and 942050 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
[20] R. Fischer, J. Langer, A. Malassa, D. Walther, H. Görls, G. Vaughan, Chem.
Commun. (2006) 2510e2512.
References
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(b) K. Lamm, M. Stollenz, M. Meier, H. Görls, D. Walther, J. Organomet. Chem.
681 (2003) 24e36.
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