Carbocyclic carbene ligands in palladium-catalyzed C-N coupling reactions

Article abstract of DOI:10.1016/j.jorganchem.2008.03.016

Palladium complexes bearing a cycloheptatrienylidene ligand are powerful precatalysts for C-N coupling reactions. Their catalytic performance is directly compared to analogous 2,3-diphenylcyclopropenylidene complexes. The crystal structure of cis-dibromo(

Full text of DOI:10.1016/j.jorganchem.2008.03.016

Journal of Organometallic Chemistry 693 (2008) 2231–2236
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Carbocyclic carbene ligands in palladium-catalyzed C–N coupling reactions
*
Christian Taubmann, Evangeline Tosh, Karl Öfele, Eberhardt Herdtweck, Wolfgang A. Herrmann
Lehrstuhl für Anorganische Chemie, Department Chemie, Technische Universität München, Lichtenbergstrasse 4, D-85747 Garching, Germany
a r t i c l e i n f o
a b s t r a c t
Article history:
Palladium complexes bearing a cycloheptatrienylidene ligand are powerful precatalysts for C–N coupling
reactions. Their catalytic performance is directly compared to analogous 2,3-diphenylcyclopropenylidene
complexes. The crystal structure of cis-dibromo(cycloheptatrienylidene)(triphenylphosphane)palla-
dium(II) is presented.
Received 29 January 2008
Received in revised form 14 March 2008
Accepted 15 March 2008
Available online 25 March 2008
Ó 2008 Elsevier B.V. All rights reserved.
Keywords:
C–N coupling
Carbenes
Carbocycles
Homogeneous catalysis
Palladium
1. Introduction
tion was unforeseen and seems even more astonishing if one takes
into account that transition metal complexes of both NHCs and
Hartwig’s and Buchwald’s palladium-catalyzed aromatic ami-
nation has become a powerful tool for the synthesis of a great vari-
ety of products, ranging from laboratory to technical scale [1,2].
The palladium metal centers are supported and controlled by
strong donor ligands. The most common ligand concepts comprise
a wide range of phosphanes, including phosphapalladacycles, and
N-heterocyclic carbenes (NHC) [3]. It is noteworthy and probably
intrinsic for these systems that ligand-free catalysis is intensely
discussed for C–C coupling, but not yet for C–N coupling reactions
[4].
carbocyclic carbenes have the same origin [6], though the latter
have been treated as laboratory curiosities over decades [7,8]. In
this context the recently reported isolation of a stable diaminocy-
clopropenylidene derivative and its corresponding lithium adduct
by Bertrand et al. [9] as well as a chiral analogue [10] deserves to
be mentioned. These precursors readily afford a range of metal
carbene complexes [11] and will certainly stimulate growth in this
area. We first described the catalytic application of this ligand
class for the Heck and Suzuki coupling. Expanding our efforts to
explore and optimize this new class of catalysts, we also included
the analogous palladium complexes bearing the smallest possible
carbocyclic carbene ligand cyclopropenylidene II [12,13]. The
three-membered ring systems yielded inferior catalytic activities
in C–C coupling, especially for deactivated chloro arenes. Hence,
we focused further work on the seven-membered ring system
and now report on a new application of the CHT ligand, as well
as on a comparison with the 2,3-diphenylcyclopropenylidene li-
gand [14].
2. Discussion
In the course of our research with and beyond NHCs in organo-
metallic chemistry and catalysis, we recently discovered that a
simple carbocyclic carbene I, cycloheptatrienylidene (CHT), is
comparable and even superior as a supporting ligand in catalysis
in comparison to well-established NHC systems [5]. This observa-
A series of dinuclear halo-bridged carbocyclic carbene palla-
dium(II) complexes 1 [5a], 2, 5 [6c,12,14] and the mononuclear
compounds 3a [5a], 3b, 4, 6 [6,12,13] bearing a carbocyclic carbene
and a phosphane ligand (Fig. 1) were used for investigations into
the catalytic activity for Hartwig–Buchwald amination.
It was not surprising that the synthesis of the cyclopropenyli-
* Corresponding author. Tel.: +49 89 289 13080; fax: +49 89 289 13473.
E-mail address: lit@arthur.anorg.chemie.tu-muenchen.de (W.A. Herrmann).
dene Pd(II) complex
5 also works straightforwardly with
0022-328X/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2008.03.016

2232
C. Taubmann et al. / Journal of Organometallic Chemistry 693 (2008) 2231–2236
Fig. 1. Palladium precatalysts supported by carbocyclic carbene ligands.
Table 1
molecularly defined soluble palladium sources like bis(dibenzyli-
deneacetone)palladium(0) [Pd(dba)2] as reported by Wass et al.
[14] instead of palladium black. We exploited this minor variation
for the synthesis of the seven-membered ring complexes, thus
obtaining almost quantitative yields for bis[dibromo(cyclohept-
atrienylidene)palladium(II)] (2). Nevertheless, the bad atom econ-
omy (M(Pd(dba)2) = 575.0 g/mol vs. M(Pd) = 106.4 g/mol), high
price and the air-sensitivity of this precursor must be seen critical.
As we extended our catalytic studies to the bromo derivatives 2
and 4, we were interested if any significant structural differences
would occur. Hence, we employed a comparison of the solid-state
structure of complex 4 (Fig. 2) [15] to that of 3a already reported
previously [5a]. Both compounds crystallize in cis-configuration
with nearly identical bond angles and a similar carbene bond
length lying in the range typical for NHC–Pd complexes (Table 1).
A considerable trans-influence of the CHT ligand indicated by a
longer Pd–Br2 bond length (0.017 Å) compared to Pd–Br1 in 4 is
a further hint for the strong r-donor and poor p-acceptor character
of this carbene ligand. Moreover, almost identical C–C bond
lengths (1.39 0.02 Å) in the seven-membered ring suggest exten-
Selected bond lengths (Å) and bond angles (°) of the CHT palladium complexes 3a and
4
3a
4
Pd–C1
Pd–X1
Pd–X2
Pd–P
X1–Pd–X2
X1–Pd–P
X1–Pd–C1
X2–Pd–P
X2–Pd–C1
P–Pd–C1
1.968(2)
2.3697(6)
2.3884(7)
2.2483(6)
91.83(2)
175.89(2)
85.14(7)
92.27(2)
174.55(6)
90.76(7)
1.983(3)
2.4895(5)
2.5064(4)
2.2575(9)
92.38(2)
175.15(3)
84.78(11)
92.42(3)
174.63(9)
90.38(11)
For compound 3a X = Cl, for compound 4 X = Br.
sive 6p delocalization including the carbene pz-orbital in the bro-
mo derivative, too.
However, we note that a similar stabilization for the three-
membered ring system (2p–eꢀ-aromaticity), as proposed inter alia
by Wass et al. [14], was recently ruled out by an experimental
Fig. 2. ORTEP style plot of compound 4 ꢁ ACN in the solid state; thermal ellipsoids set at 50% probability.

C. Taubmann et al. / Journal of Organometallic Chemistry 693 (2008) 2231–2236
2233
Table 3
Catalysis data
charge-density approach for free as well as coordinated cyclopro-
penylidene carbenes by Scherer et al. [16]. Clearly a higher p-
acceptor capability relative to N-heterocyclic carbenes was shown.
Work is underway to further elucidate the r-donor/p-acceptor
properties of the CHT ligand.
a
Entry
Cat.
mol% Pd
T/°C
Base
R
X
Yieldb/%
For a catalytic evaluation, we followed established standard
protocols [1] to facilitate the comparison of the results obtained.
We extended phosphane screening with compound 1 (Table 2) as
this in situ-method provides an efficient and valuable probe for
identifying which catalytic systems may warrant further study.
The halo-bridged complexes 1, 2, 5 are known to undergo easy
cleavage by phosphanes, thus yielding the relevant precatalysts.
In the coupling of the activated bromo substrate p-bromo benzotri-
fluoride with morpholine at elevated temperatures, our CHT com-
plex is active with a variety of phosphanes employed (Table 2,
entries 2–7). For the corresponding chloro substrate distinct differ-
ences were observed. Appreciable yields could only be obtained
with the more basic alkylphosphanes PCy3 and PtBu3 (Table 2, en-
tries 13 and 14). In addition, the phosphane with the largest cone
angle, PMes3, was not compatible with the CHT ligand and yielded
the same poor results as the phosphane-free runs (Table 2, entries
1, 5, 8 and 12) suggesting the crucial role of a second suitable do-
nor ligand attached to the palladium metal center. Comparing GC-
based conversions and yields in terms of catalyst selectivity for
several runs, more than 30% higher conversion than yield was ob-
served due to side reactions (Table 2, e.g. entries 6 and 13). How-
1
2
3a
3a
6
2.0
2.0
2
100
100
100
100
100
100
100
100
100
100
100
100
75
50
50
50
50
100
100
100
r.t.
100
100
NaOtBu
NaOtBu
NaOtBu
NaOtBu
NaOtBu
NaOtBu
NaOtBu
NaOtBu
KOtBu
F3C
MeO
F3C
MeO
F3C
H
MeO
MeO
F3C
F3C
F3C
F3C
F3C
F3C
F3C
F3C
F3C
Br
Br
Br
Br
Cl
Cl
Cl
Br
Br
Br
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
Cl
Cl
Cl
Cl
70
31
63
23
66
41
12
62
77
81
78
37
79
50
81
100
100
100
94
86
11
50
31
3 [14]
4 [14]
5
6
7
6
2
3b
3b
3b
4
3a
4
3a
3a
3a
3a
4
2.0
2.0
2.0
2.0
2.0
2.0
1.0
0.5
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
2.0
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
KOtBu
c
1
KOtBu
5c
KOtBu
c
1
2
5
2
NaOtBu
NaOtBu
NaOtBu
KOtBu
MeO
MeO
MeO
MeO
MeO
MeO
c
c
c
NaOtBu
NaOtBu
c
Pd(PhCN)2Cl2
Pd(PhCN)2Cl2
d
a
Conditions: 1.0 mmol of aryl halide, 1.2 mmol of morpholine, 1.4 mmol of base,
8 ml toluene, 18 h.
ever, employing only conversion as
a measure for catalyst
b
activity is in a way misleading and the importance of yield-based
discussion should be emphasized [13]. Finally in this screening
experiment for each run (except Table 2, entry 1) with the CHT
system superior results could be realized in comparison with the
preliminary data published by Wass et al. for the 2,3-diphenylcy-
clopropenylidene system [14].
Having in mind the strong influence of the participating phos-
phane, further investigations as to the effects of aryl halide deacti-
vation, catalyst loading, temperature, base, etc., were carried out
with various catalytic systems (Table 3). Similar yields were ob-
served for application of an in situ-mixture in comparison to the
isolated precatalyst suggesting the same active species is present
in both reactions (Table 2, entry 3 vs. Table 3, entry 1). The amina-
tion of chloro-arenes is possible with precatalyst 3b; however, the
GC yield with n-eicosane as the internal standard.
In situ with 1.0 equiv. PtBu3.
c
In situ with 2.0 equiv. PtBu3.
d
efficiency is strongly governed by the degree of substrate activa-
tion (Table 3, entries 5–7). On the one hand, this highlights the lim-
itations of catalyst 3b. On the other hand, it emphasizes the
important role of PtBu3 in this particular catalytic system. A signif-
icant loss of activity was also observed by decreasing the catalyst
concentration from 2% to 0.5% (Table 3, entries 9, 11 and 12). The
use of the stronger base KOtBu instead of NaOtBu resulted in
slightly higher yields (Table 3, entries 1 and 9). A carbene-free pal-
ladium source was employed to confirm the importance of the car-
bocyclic carbene ligand (Table 3, entry 22). As previously reported,
an excess of phosphane is shown to be rather detrimental to the
system (Table 3, entry 23) [17].
The role of the halogen attached to the palladium by parallel
screening of the halo-bridged complexes 1 and 2 and the mononu-
clear complexes 3a and 4 was investigated, too. Both 1 and 2, in
combination with PtBu3, are able to aminate deactivated chloro-
arenes in excellent yields (Table 3, entries 18 and 19). In compar-
ison to its chloro derivative, compound 4 with p-bromo anisole
gave significantly higher yields (Table 3, entries 2 and 8). More-
over, better performance at moderate temperatures could be ob-
served (Table 3, entries 14 and 15), though for the coupling of
deactivated chloro-arenes, i.e. p-chloro anisole at room tempera-
ture (Table 3, entry 21), our CHT-system requires further optimiza-
tion to be competitive with other highly active catalysts [18].
In agreement with our phosphane screening experiments (Table
2), the CHT system was shown to be superior to the 2,3-cyclopro-
penylidene system when employed as isolated mixed carbene
phosphane complexes (Table 3, entries 1–4) or when generated
by the in situ-method (Table 3, entries 18 and 20). High reactivity
with a variety of other amines (2,4,6-trimethylaniline, N-methy-
laniline, o-toluidine, diphenylamine) was also observed (not
shown). However, quantification using 1H NMR as suggested by
Wass et al. [14] for these substrates, particularly for the diphenyl-
amine, turned out to be capricious, as such GC-FID quantification
was employed [1].
Table 2
Phosphane screening
Entrya
Phosphane
X
Conversionb (yield)c%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
None
P(p-F–Ph)3
PPh3
Br
Br
Br
Br
Br
Br
Br
Cl
Cl
Cl
Cl
Cl
Cl
Cl
35 (19)
100 (69)
100 (70)
100 (90)
37 (20)
100 (68)
100 (100)
5 (1)
1 (1)
1 (1)
10 (5)
8 (3)
P(o-Tol)3
PMes3
PCy3
PtBu3
None
P(p-F–Ph)3
PPh3
P(o-Tol)3
PMes3
PCy3
100 (64)
100 (98)
PtBu3
a
Conditions: 1.0 mmol of aryl halide, 1.2 mmol of morpholine, 1.4 mmol of
NaOtBu, 2.0 mol% of Pd, 1.0 equiv. of phosphane, 8 ml toluene, 100 °C, 18 h.
b
GC conversion based on aryl halide with n-eicosane as the internal standard.
GC yield with n-eicosane as the internal standard.
c

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C. Taubmann et al. / Journal of Organometallic Chemistry 693 (2008) 2231–2236
tor. Compounds 1, 3a, 5 and 6 were prepared according to the lit-
erature [5a,12].
4.1. Synthesis
4.1.1. Bis[dibromo(cycloheptatrienylidene)palladium(II)] (2)
This compound has been prepared by combination, with slight
modifications, of two procedures reported previously [5a,14].
Pd(dba)2 (244 mg, 0.424 mmol) and dibromocycloheptatriene
(104 mg, 0.416 mmol) were suspended in 10 ml THF at ꢀ78 °C.
The mixture was allowed to reach room temperature and was stir-
red over night. The precipitate formed was filtered off, thoroughly
washed with diethyl ether and dried in vacuo. Compound 2 was
obtained as bright orange microcrystalline powder containing
0.5 equiv. of diethyl ether. Yield: 151 mg (97%).
1H NMR (ACN-d3)1: d [ppm] = 9.54 (d, 3J = 10 Hz, 2H, CHT), 8.34
(dd, 3J = 3.6/6.4 Hz, 2H, CHT), 8.05 (m, 2H, CHT), 3.42 (q, 3J = 6.9 Hz,
1H, O–CH2–CH3), 1.12 (t, 3J = 6.8 Hz, 1.5H, O–CH2–CH3).
13C NMR (ACN-d3)1: d [ppm] = 217.5 (carbene C), 162.7 (CHT),
147.7 (CHT), 139.8 (CHT), 66.1 (O–CH2–CH3), 15.5 (O–CH2–CH3).
Fig. 3. Yield vs. time plot at room temperature for the coupling of p-bromo benz-
otrifluoride (1.0 mmol) with morpholine (1.2 mmol) catalyzed by 1 (–ꢂ–) and 5
(–j–) in situ with 1.0 equiv. PtBu3 (other conditions: 2 mol% Pd, 1.4 mmol NaOtBu,
8 ml toluene; GC yield with n-eicosane as the internal standard).
Elemental analysis calcd for
(M = 749.76 g/mol): C, 25.63; H, 2.29; Pd, 28.39. Found: C, 25.16;
C
14H12Br4Pd2 ꢁ 0.5C4H10
O
H, 2.21; Pd, 28.2%.
4.1.2. cis-Dichloro(cycloheptatrienylidene)(tricyclohexylphosphane)
palladium(II) (3b)
This compound has been prepared by a procedure reported pre-
viously [5a].
As already shown, carbocyclic carbene palladium precatalysts
do not suffer from an induction period [5,12–14]. We could con-
firm these findings also for C–N coupling catalysis, even at room
temperature (Fig. 3). It was surprising to observe even for the
strongly activated substrate p-bromo benzotrifluoride that the
CHT system is superior over the 2,3-diphenylcyclopropenylidene
system: the CHT system gave quantitative yields already after ca.
10 min, while the three-membered carbocyclic carbene had its
limit at 70% maximum.
Elemental analysis calcd for C25H39Cl2PPd (M = 547.88 g/mol):
C, 54.81; H, 7.17; Pd, 19.42. Found: C, 54.50; H, 7.40; Pd, 19.4%.
1H NMR (ACN-d3): d [ppm] = 9.49 (d, 3J = 10 Hz, 2H, CHT), 8.40
(m, 2H, CHT), 8.13 (m, 2H, CHT), 2.1–1.1 (m, 33H, PCy3).
31P{1H} NMR (ACN-d3): d [ppm] = 51.6 (s).
MS(FAB): m/z (%): 513 (16, [MꢀCl]+).
3. Conclusion
4.1.3. cis-Dibromo(cycloheptatrienylidene)(triphenylphosphane)-
palladium(II) (4)
Our carbocyclic carbene palladium complexes show high activ-
ity in Hartwig–Buchwald amination reactions. In each particular
screening experiment, the CHT-supported palladium precatalysts
in combination with a phosphane ligand formed catalytically more
active species than the analogous 2,3-diphenylcyclopropenylidene
This compound has been prepared by a procedure reported pre-
viously [5a].
Elemental analysis calcd for C25H21Br2PPd (M = 618.64 g/mol):
C, 48.54; H, 3.42; Pd, 17.20. Found: C, 50.06; H, 3.80; Pd, 16.9%.
1H NMR (ACN-d3): d [ppm] = 9.30 (d, 3J = 10 Hz, 2H, CHT), 8.09
(dd, 3J = 4.2/6.6 Hz, 2H, CHT), 7.69 (m, 2H, CHT), 7.62 (m, 6H,
o-Ph), 7.41 (m, 3H, p-Ph), 7.31 (m, 6H, m-Ph).
31P{1H} NMR (ACN-d3): d [ppm] = 29.2 (s).
systems.
Both
isolated
mononuclear
complexes
cis-
(CHT)(PPh3)PdX2 (X = Cl, Br) exhibit very similar structural features
in the solid state. However, the catalytic activity of the bromo
derivative is significantly higher. Work is underway to investigate
electronically and sterically modified CHT ligands, and to elucidate
the role of the carbocyclic carbene ligand in the catalytic cycle.
MS(FAB): m/z (%): 538 (100, [MꢀBr]+).
4.2. C–N coupling
4. Experimental
An analogous procedure was followed in each case and is exem-
plified here for Table 2, entry 2. The reaction vessel was loaded
with precatalyst 1 (0.010 mmol), P(p-F–Ph)3 (0.020 mmol) and
the internal standard n-eicosane which were suspended in toluene
(8 ml) followed by addition of p-bromo benzotrifluoride
(1.0 mmol), morpholine (1.2 mmol) and NaOtBu (1.4 mmol). The
reaction mixture was heated at 100 °C for 18 h (agitation speed
550 minꢀ1). After this time, the mixture was cooled to room tem-
perature and quenched with water (2 ml). The organic phase was
separated and dried over Na2SO4. The kinetic runs at room temper-
ature were performed in the same way, only an aliquot of a phos-
phane-solution with defined concentration in toluene was added
General comments: All manipulations were performed under an
inert atmosphere of argon using standard Schlenk and dry-box
techniques. Dry, oxygen-free solvents were employed. 1H, 13C
and 31P NMR spectra were recorded on a JEOL-JMX-GX 400 spec-
trometer (frequencies: 1H 399.8 MHz, 13C 100.5 MHz, 31P
161.8 MHz) at room temperature and referenced to the residual
1H and 13C signals of the solvents or 85% H3PO4 as an external stan-
dard (31P). NMR multiplicities are abbreviated as follows: s, singlet;
d, doublet; t, triplet; q, quartet, m, multiplet. Elemental analyses
were carried out by the Microanalytical Laboratory at TU München.
Mass spectra were performed on a Finnigan MAT 90 spectrometer
using the FAB technique (Mass Spectrometry Laboratory, TU Mün-
chen). Catalysis was performed with a Heidolph Synthesis 1 Liquid
system. GC spectra were measured on a Varian gas chromatograph
CP-3800 (column: FactorFour VF-5 ms) equipped with a FID detec-
1
Compound 2 is insoluble in common non-coordinating solvents. Most likely the
bromo bridge is cleaved by acetonitrile yielding (ACN)(CHT)PdBr2 (unpublished
results).

C. Taubmann et al. / Journal of Organometallic Chemistry 693 (2008) 2231–2236
2235
at the end to start the experiment (t = 0 min). Conversions and
Acknowledgement
yields were determined by GC analysis.
We gratefully acknowledge support and funding from NanoCat,
an International Graduate Program within the ‘‘Elite Network
Bavaria”, as well as the Fonds der Chemischen Industrie (Frankfurt
a. Main).
4.3. Single crystal X-ray structure determination of compound 4 ꢁ ACN
General: Crystal data and details of the structure determination
are presented in Table 4. A suitable single-crystal for the X-ray dif-
fraction study was grown with standard cooling techniques. The
selected crystals was stored under perfluorinated ether, trans-
ferred in a Lindemann capillary, fixed, and sealed. Preliminary
examination and data collection were carried out on an area
detecting system with graphite-monochromated Mo Ka radiation
(k = 0.71073 Å, OXFORD DIFFRACTION, Xcalibur, j-CCD; sealed tube, En-
hance X-ray Source, SPELLMAN, DF3). The unit cell parameters were
obtained by full-matrix least-squares refinements during the scal-
ing procedure. Data collection were performed at low tempera-
tures (T = 153 K, OXFORD CRYOSYSTEMS cooling device). The crystal was
measured with nine data sets in rotation scan modus (D//
Dx = 2.00°; dx = 50). Intensities were integrated and the raw data
were corrected for Lorentz, polarization, and, arising from the scal-
ing procedure for latent decay and absorption effects. The struc-
tures were solved by a combination of direct methods and
difference Fourier syntheses. All non-hydrogen atoms were refined
with anisotropic displacement parameters. Methyl hydrogen atoms
were calculated as a part of rigid rotating groups, with dC–H = 0.98 Å
and iso(H) = 1.5Ueq(C). All other hydrogen atoms were placed in
ideal positions and refined using a riding model, with aromatic
dC–H distances of 0.95 Å, and Uiso(H) = 1.2Ueq(C). Full-matrix least-
squares refinements were carried out by minimizing
Appendix A. Supplementary material
CCDC 680443 contains the supplementary crystallographic 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.
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P
2
wðF2o ꢀ F2c Þ with the SHELXL-97 weighting scheme and stopped
at shift/err <0.001. The final residual electron density maps showed
no remarkable features. Neutral atom scattering factors for all
atoms and anomalous dispersion corrections for the non-hydrogen
atoms were taken from International Tables for Crystallography.
All calculations were performed with the WINGX system, including
[4] For example see M.T. Reetz, J.G. de Vries, Chem. Commun. (2004) 1559.
[5] (a) W.A. Herrmann, K. Öfele, S.K. Schneider, E. Herdtweck, S.D. Hoffmann,
Angew. Chem. 118 (2006) 3943; Angew. Chem., Int. Ed. 45 (2006) 3859;
(b) W.A. Herrmann, K. Öfele, S.K. Schneider, DE 102005062920, 2007.
[6] (a) K. Öfele, Angew. Chem. 80 (1968) 1032; Angew. Chem., Int. Ed. 7 (1968)
950;
the programs PLATON, SHELXL-97, and SIR92 [15].
Table 4
Crystallographic data for 4 ꢁ ACN
(b) K. Öfele, J. Organomet. Chem. 12 (1968) P42;
(c) K. Öfele, J. Organomet. Chem. 22 (1970) C9.
4 ꢁ ACN
C27H24Br2NPPd
[7] For examples of the cyclopropenylidene system see (a) H. Konishi, S.
Matsumoto, Y. Kamitori, H. Ogoshi, Z. Yoshida, Chem. Lett. (1978) 241;
(b) R. Weiss, C. Priesner, Angew. Chem. 90 (1978) 491; Angew. Chem., Int. Ed.
Engl. 17 (1978) 457;
Formula
Formula weight
659.66
Color/habit
Yellow/fragment
0.30 ꢃ 0.56 ꢃ 0.58
Triclinic
Crystal dimensions (mm3)
(c) R.D. Wilson, Y. Kamitori, H. Ogoshi, Z. Yoshida, J.A. Ibers, J. Organomet.
Chem. 173 (1979) 199;
(d) Z. Yoshida, Pure Appl. Chem. 54 (1982) 1059;
Crystal system
Space group
a (Å)
b (Å)
c (Å)
a (°)
b (°)
ꢀ
P1 (no. 2)
(e) S. Miki, T. Ohno, H. Iwasaki, Z. Yoshida, J. Phys. Org. Chem. 1 (1988) 333;
(f) H. Schumann, M. Glanz, F. Girgsdies, F.E. Hahn, M. Tamm, A. Grzegorzewski,
Angew. Chem. 109 (1997) 2328; Angew. Chem., Int. Ed. Engl. 36 (1997) 2232;
(g) A. de Meijere, S. Müller, T. Labahn, J. Organomet. Chem. 617 (2001) 318;
(h) J.T. DePinto, W.A. deProphetis, J.L. Menke, R.J. McMahon, J. Am. Chem. Soc.
129 (2007) 2308.
9.9435(6)
10.6413(6)
12.4012(7)
98.629(5)
94.270(5)
90.529(5)
1293.46(13)
2
153
1.694
3.883
648
2.74–25.35
11, 12, 14
23678
4703/0.030
3722
4703/0/290
0.0291/0.0678
0.0429/ 0.0769
1.154
c (°)
[8] For examples of the CHT-system see (a) P.E. Riley, R.E. Davis, N.T. Allison, W.M.
Jones, Inorg. Chem. 21 (1982) 1321;
V (Å3)
Z
(b) F.J. Manganiello, M.D. Radcliffe, W.M. Jones, J. Organomet. Chem. 228
(1982) 273;
(c) J.R. Lisko, W.M. Jones, Organometallics 5 (1986) 1890;
(d) Z. Lu, W.M. Jones, Organometallics 12 (1993) 1344.
[9] (a) V. Lavallo, Y. Canac, B. Donnadieu, W.W. Schoeller, G. Bertrand, Science 312
(2006) 722;
(b) V. Lavallo, Y. Ishida, B. Donnadieu, G. Bertrand, Angew. Chem. 118 (2006)
6804; Angew. Chem., Int. Ed. 45 (2006) 6652.
[10] D. Holschumacher, C.G. Hrib, P.G. Jones, M. Tamm, Chem. Commun. (2007)
3661.
[11] G. Kuchenbeiser, B. Donnadieu, G. Bertrand, J. Organomet. Chem. 693 (2008)
899.
[12] W.A. Herrmann, K. Öfele, C. Taubmann, E. Herdtweck, S.D. Hoffmann, J.
Organomet. Chem. 692 (2007) 3846.
[13] We note that simultaneously our cyclopropenylidene Pd catalysts were
screened in C–C coupling reactions by Wass et al., too. However,
unfortunately no product yields only conversions were reported in this
preliminary communication, cf.: D.F. Wass.; M.F. Haddow, T.W. Hey, A.G.
Orpen, C.A. Russell, R.L. Wingad, M. Green, Chem. Commun. (2007) 2704.
T (K)
Dcalcd (g cmꢀ3
)
l (mmꢀ1
F(000)
)
h Range (°)
Index ranges (h,k,l)
Number of reflections collected
Number of independent reflections/Rint
Number of observed reflections (I > 2r(I))
Number of data/restraints/parameters
R1/wR2 (I > 2r(I))a
R1/wR2 (all data)a
Goodness-of-fit (on F2)a
Largest diffraction peak and hole (e Åꢀ3
)
+0.86/ꢀ0.76
P
P
P
P
2
2
1=2
a
R1
¼
ðkFoj ꢀ jFckÞ= jFoj; wR2 ¼ f ½wðF2o ꢀ Fc2Þ ꢄ= ½wðFo2Þ ꢄg
;
P
2
1=2
GOF ¼ f ½wðF2o ꢀ F2c Þ ꢄ=ðn ꢀ pÞg
.

2236
C. Taubmann et al. / Journal of Organometallic Chemistry 693 (2008) 2231–2236
[14] D.F. Wass, T.W. Hey, J. Rodriguez-Castro, C.A. Russell, I.V. Shishkov, R.L.
Wingad, M. Green, Organometallics 26 (2007) 4702.
(f) L.J. Farrugia, WINGX, Version 1.70.01 January 2005, J. Appl. Crystallogr. 32
(1999) 837–838.
[15] (a) CRYSALIS Data Collection Software and Data Processing Software for Oxford
Diffraction Xcalibur devices, Version 1.171, Oxford Diffraction Ltd.,
Oxfordshire, United Kingdom, 2005.;
[16] W. Scherer, M. Tafipolsky, K. Öfele, Inorg. Chim. Acta 361 (2008) 513.
[17] J.F. Hartwig, M. Kawatsura, S.I. Hauck, K.H. Shaughnessy, L.M. Alcazar-Roman,
J. Org. Chem. 64 (1999) 5575.
(b) A. Altomare, G. Cascarano, C. Giacovazzo, A. Guagliardi, M.C. Burla, G.
[18] (a) For example see O. Navarro, N. Marion, J. Mei, S.P. Nolan, Chem. Eur. J. 12
(2006);
Polidori, M. Camalli, J. Appl. Crystallogr. 27 (1994) 435–436. SIR92
;
(c) A.J.C. Wilson (Ed.), International Tables for Crystallography, vol. C, Kluwer
Academic Publishers, Dordrecht, The Netherlands, 1992, Tables 6.1.1.4, 4.2.6.8,
and 4.2.4.2.;
(d) G.M. Sheldrick, SHELXL-97, Universität Göttingen, Göttingen, Germany, 1998.;
(e) A.L. Spek, PLATON, A Multipurpose Crystallographic Tool, Utrecht University,
Utrecht, The Netherlands, 2007.;
(b) J.P. Stambuli, R. Kuwano, J.F. Hartwig, Angew. Chem. 114 (2002) 4940;
Angew. Chem., Int. Ed. 41 (2002) 4746;
(c) S.R. Stauffer, S. Lee, J.P. Stambuli, S.I. Hauck, J.F. Hartwig, Org. Lett. 2 (2000)
1423;
(d) J.P. Wolfe, S.L. Buchwald, Angew. Chem. 111 (1999) 2570; Angew. Chem.,
Int. Ed. 38 (1999) 2413.