Synthesis and structural characterization of mixed carbene-carboxylate complexes of palladium(II)

Article abstract of DOI:10.1016/j.jorganchem.2004.02.033

Mixed carbene-carboxylate complexes of Palladium(II) have been prepared by reacting {1,1′-dimethyl-3,3′- methylenediimidazoline-2,2′-diylidene} palladium(II) diiodide (1) [Angew. Chem. 107 (1995) 2602; Angew. Chem. Int. Ed. Engl. 34 (1995) 2371; J. Organomet. Chem. 557 (1998) 93] with AgO₂CR, where R=CF₃, CF₂CF₃ and CF₂CF₂CF₃. In this manner, {1,1′-dimethyl-3,3′-methylenediimidazoline-2,2′- diylidene} palladium(II) bis(trifluo-roacetate) (2), {1,1′-dimethyl-3,3′-methylenediimidazoline-2,2′- diylidene} palladium(II) bis(pentafluoropropionate) (3) and {1,1′-dimethyl-3,3′-methylenediimidazoline-2,2′- diylidene} palladium(II) bis(heptafluorobutyrate) (4) were obtained. All three complexes were fully characterized by ¹H-, ¹³C- and ¹⁹F NMR spectroscopy as well as ESI mass spectrometry. X-ray crystal structure analyses of complexes 3 and 4 reveal mononuclear species with a square planar metal center coordinated by a cis-chelating dicarbene and two monodentate carboxylate ligands. The results show that the introduction of a cis-chelating N,N-heterocyclic carbene ligand stabilizes the palladium-carboxylate moiety effectively.

Full text of DOI:10.1016/j.jorganchem.2004.02.033

Journal of Organometallic Chemistry 689 (2004) 1766–1770
www.elsevier.com/locate/jorganchem
Synthesis and structural characterization of mixed
carbene-carboxylate complexes of palladium(II)
Han Vinh Huynh , Duc Le Van , F. Ekkehardt Hahn b,*, T.S. Andy Hor a
a,
b
*
a
Department of Chemistry, National University of Singapore, 3 Science Drive 3, Singapore 117543, Singapore
Institut f €u r Anorganische und Analytische Chemie der Westf €a lischen, Wilhelms-Universit €a t M €u nster, Wilhelm Klemm-Strasse 8,
b
D-48149 M €u nster, Germany
Received 10 November 2003; accepted 12 February 2004
Abstract
0
0
Mixed carbene-carboxylate complexes of Palladium(II) have been prepared by reacting {1,1 -dimethyl-3,3 -methylenediimidaz-
0
oline-2,2 -diylidene} palladium(II) diiodide (1) [Angew. Chem. 107 (1995) 2602; Angew. Chem. Int. Ed. Engl. 34 (1995) 2371; J.
0
Organomet. Chem. 557 (1998) 93] with AgO2CR, where R ¼ CF3, CF2CF3 and CF2CF2CF3. In this manner, {1,1 -dimethyl-3,
0
0
0
0
0
3
-methylenediimidazoline-2,2 -diylidene} palladium(II) bis(trifluo-roacetate) (2), {1,1 -dimethyl-3,3 -methylenediimidazoline-2,2 -
0
0
0
diylidene} palladium(II) bis(pentafluoropropionate) (3) and {1,1 -dimethyl-3,3 -methylenediimidazoline-2,2 -diylidene} palla-
dium(II) bis(heptafluorobutyrate) (4) were obtained. All three complexes were fully characterized by 1H-, 13C- and 19F NMR
spectroscopy as well as ESI mass spectrometry. X-ray crystal structure analyses of complexes 3 and 4 reveal mononuclear species
with a square planar metal center coordinated by a cis-chelating dicarbene and two monodentate carboxylate ligands. The results
show that the introduction of a cis-chelating N,N-heterocyclic carbene ligand stabilizes the palladium-carboxylate moiety effec-
tively.
ꢀ
2004 Elsevier B.V. All rights reserved.
Keywords: Palladium; N-Heterocyclic carbene; Carboxylate; Crystal structure
1
. Introduction
complexes supported by the chelating and thus stabiliz-
0
ing 1,1 -bis(diphenylphosphino)ferrocene (dppf) ligand.
Carboxylate ligands have been widely used in coordi-
Bianchini et al. [4b] isolated bis(acetate) complexes of
palladium stabilized by 1,2-bis-(diphenylphosphino)eth-
ane (dppe) and the more complicated meso-2,3-bis(di-
phenyl-phosphino)butane (meso-2,3-dppb) and rac-2,
3-bis(diphenylphosphino)butane (rac-2,3-dppb) ligands.
We attempted to stabilize the palladium-carboxylate
moiety further by replacing the diphosphine with a dic-
arbene ligand. In doing so, we are also a step closer to
achieve the objective of making phosphine-free catalysts
[7]. Nucleophilic carbene ligands could have similar
properties to phosphine ligands (‘‘phosphine mimics’’),
but they are free of the dissociative problems that many
phosphines experience. The use of carbene instead of
phosphine as a supporting entity is therefore currently a
topic of intense interest [7]. Notable examples are recently
found in ruthenium chemistry, in which the second gen-
eration Grubbs catalysts for olefin metathesis reactions
have been developed. In these, the phosphine ligand of
nation chemistry and their complexes are in general
known to be stable [1]. However, there are notable ex-
ceptions such as Pd(II) phosphine carboxylates, which
are believed to decompose through a reductive pathway
giving anionic Pd(0) complexes [2,3], black palladium or
undergo an autoionization process, especially in polar
solvents such as methanol [4]. As catalytically active
species in C–C-coupling reactions, such as Heck-type
syntheses [5] and CO/olefin copolymerization [4], much
effort was put into the study of their reactivities and
structures. Hor and co-workers [6] reported the isolation
and structural characterization of palladium carboxylate
*
Corresponding authors. Tel.: +65-6874-2670; fax: +65-6779-1691
H.V. Huynh); fax: +49-251-833-3108 (F.E. Hahn).
(
E-mail addresses: chmhhv@nus.edu.sg (H.V. Huynh), fehahn@uni-
muenster.de (F. Ekkehardt Hahn).
0
022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.02.033

H.V. Huynh et al. / Journal of Organometallic Chemistry 689 (2004) 1766–1770
1767
the original Grubbs-type catalyst is replaced by an N,N-
heterocyclic ‘‘Arduengo carbene’’ resulting in higher
stability as well as catalytic activity. Another interesting
example is the substitution of phosphine ligands for N-
heterocyclic carbenes in palladium complexes for Heck-
type reactions [8]. However, mixed carbene carboxylate
complexes of palladium(II) have not been studied in
depth, yet palladium carboxylates remain the key mate-
rials for Heck-syntheses. Herein, we report the synthesis
and the first structural characterization of cis-dicarbene-
bis(carboxylate) complexes of palladium(II).
obtained as crystalline and colorless plates, both suitable
for X-ray structure determination.
The coordination of the carboxylate ligands to the
carbene complex fragment results only in minor changes
1
of the H resonances of the cis-chelating dicarbene li-
gand in 2–4 compared to the precursor 1 [8a,8b]. These
resonances are also not strongly influenced by the length
of the carboxylate chains and have almost identical
values for complexes 2–4. Furthermore, all three com-
plexes showed only a singlet for the methylene bridge
between the carbene moieties at d ¼ 6:34–6:36 ppm in-
dicating fluxional behavior of the boat conformation of
the six-membered chelate rings at room temperature
[9,10]. 13C NMR spectroscopy has been carried out for
further characterization. Fig. 1 depicts the 13C NMR
spectrum of complex 4 as a representative. Upon coor-
dination of carboxylate ligands, a significant upfield
shift for the carbene carbon resonance is observed as
compared to the precursor 1 [8a,8b]. Values for 1
(d ¼ 185:5 ppm) and the corresponding bis(acetate)
complex (d ¼ 154:8 ppm) [9] have been reported. For
the fluorocarboxylate complexes 2–4, values of
d ¼ 148:9, 149.3 and 149.1 ppm were found, respec-
tively, demonstrating an increased shielding effect due to
the fluoro substituents. However, only substituents at
the a-carbon atom of the carboxylate are involved and
an increase of the fluorocarboxylate chain again shows
no influence on the chemical shift of the carbene carbon
resonance. The resonances for the fluorocarboxylates
ligands were more difficult to assign due to the relative
low intensities and the complicated pattern resulting
from C–F coupling, especially for complex 4 with three
inequivalent C–F groups (Fig. 1). The CF coupling
2
. Results and discussion
2
.1. Synthesis and characterization
The mixed carbene-carboxylate complexes 2, 3 and 4
0
0
were synthesized by reacting [{1,1 -dimethyl-3,3 -
0
methylenediimidazoline-2,2 -diylidene}palladium(II) di-
iodide] (1) [8] with appropriate silver fluorocarboxylates
under elimination of AgI as depicted in Scheme 1. A
similar approach has already been used by Herrmann et
al. [9] to generate the corresponding Pd(II) bis(acetate)
complex. We prefer to work with fluorocarboxylates
owing to their higher degree of coordination mobility
[
6a], which is a key element in the catalyst design. The
complexes 2–4 are air-stable in the solid state and show
an excellent solubility in polar solvents such as aceto-
nitrile, acetone, DMF and DMSO. As expected, the
solubility increases with the chain length of the fluoro-
carboxylates. While the pentafluoropropionate deriva-
tive 3 is only sparingly soluble in dichloromethane,
chloroform and THF, the bis(heptafluorobutyrate) de-
rivative 4 readily dissolves in these solvents. The stability
in solution is also influenced by the carboxylate chain
length. The tendency to decompose to black palladium,
which is related to the basicity of the carboxylate ligand,
increases in the order CO CF < CO CF CF < CO -
1
constants fall in the range of J(C,F) ¼ 263–295 Hz and
2
J(C,F) ¼ 23–37 Hz. Although both the carbene and
carboxylate ligand can coordinate in a bridging mode,
there is no evidence for such coordination in the NMR
spectra.
2
3
2
2
3
2
CF CF CF . However, decomposition occurs very
3
2.2. Molecular structure of complexes 3 and 4
2
2
slowly and even DMSO solutions of 3 and 4 can be kept
for at least a week, while 2 is stable in solution for
months without any sign of decomposition. Complex 3
crystallizes as colorless prisms and complex 4 can be
Single crystals suitable for X-ray diffraction studies of
complexes 3 and 4 were obtained by slow evaporation of
the solvents at ambient temperature from a concentrated
acetonitrile/toluene solution. The molecular structure of
3
and 4 are depicted in Fig. 2. As found by NMR
spectroscopy in solution, both compounds crystallize as
mononuclear complexes. In both cases the palladium
atom is coordinated in a nearly perfect square-planar
geometry (sum of angles around Pd 359.96ꢁ for 3 and
359.98ꢁ for 4) by two monodentate carboxylates and a
cis-chelating dicarbene ligand. The resulting six-mem-
bered C3N2Pd ring is fixed in the boat conformation
typically found for such compounds. The pendant oxy-
gen atoms of the carboxylates in both complexes are in a
syn-conformation and exo-orientated to the methylene
Scheme 1. Preparation of complexes 2–4 from 1.

1768
H.V. Huynh et al. / Journal of Organometallic Chemistry 689 (2004) 1766–1770
Fig. 1. 13C NMR spectrum of complex 4.
bridge of the dicarbene ligand. Since the molecular
structure of both complexes are very similar, only that
of complex 3 is discussed in detail herein.
The Pd–C bond lengths in 3 (1.948(3) and 1.949(3) A)
are almost identical. They are shorter than those re-
ꢀ
ꢀ
ported for 1 (1.988(7), 1.989(8) A) [8c] and its bis(benz-
ꢀ
imidazolin-2-ylidene) homologue (1.990(8), 1.991(7) A)
[
11], presumably a reflection of the higher electron do-
nation of the carbene centers to palladium as a conse-
quence of higher Lewis acidity of the metal center
induced by the fluorocarboxylates. The Pd–O distances
ꢀ
of 2.085(2) and 2.071(3) A are consistent with those in
ꢀ
(dppf)Pd(O2CCF2CF3)2] (2.076(3), 2.065(3) A) [6a] and
ꢀ
(dppf)Pd(O2CCF2CF2CF3)2] (2.096(4), 2.105(4) A) [6b].
[
[
Due to the short methylene bridge between the carbenes,
the C–Pd–C bite angle is reduced from the ideal value for
a square planar complex to 84.6(1)ꢁ. It has been dem-
onstrated, that lengthening of the bridge between two
cis-coordinated N-heterocyclic carbenes increases this
angle [12].
The two monodentate carboxylate ligands are rela-
tively flexible and free from distortion, apart from the
interligand van der Waals repulsion. However, the O–
Pd–O angle is also short of ideal (84.88(11)ꢁ), which
gives rise to an almost linear C–Pd–O arrangement with
angles of 177.48(11)ꢁ and 177.18(12)ꢁ, respectively. The
monodentate coordination mode of the carboxylate li-
gands is also reflected in the COcoord bond lengths of
1
ꢀ
.245(5) and 1.259(4) A as compared to the significantly
ꢀ
shorter C–Opendant distances of 1.195(5) and 1.213(4) A.
Further structural parameters for complex 3 are unex-
ceptional and do not require further comment.
We have demonstrated that stable carbene-fluoro-
carboxylate complexes of palladium(II) can be conve-
niently synthesized and isolated. Current directions in
our laboratories involve their use as precursors for
mixed-metal carbene-carboxylates, which are not com-
mon in the literature, and their application in catalytic
trasnsformations in an environment that demands the
exclusion of phosphines.
Fig. 2. Molecular structure of complexes 3 (top) and 4 (bottom). Se-
ꢀ
lected bond lengths (A) and bond angles (ꢁ) for 3 [4]: Pd–O1 2.085(2)
[
2.080(3)], Pd–O3 2.071(3) [2.083(3)], Pd–C1 1.948(3) [1.955(4), Pd–C6
.949(3) [1.958(4)], N1–C1 1.343(4) [1.360(5)], N1–C5 1.444(4)
1.456(6)], N2–C1 1.338(4) [1.349(5)], N3–C5 1.449(4) [1.447(6)], N3–
C6 1.345(4) [1.353(6)], N4–C6 1.339(4) [1.349(6)]; O1–Pd–O3 84.88(11)
1
[
[
[
[
84.39(12)], O1–Pd–C1 92.99(12) [93.76(15)], O1–Pd–C6 177.18(12)
176.83(15)], O3–Pd–C1 177.48(11) [178.12(15)], O3–Pd–C6 97.53(12)
97.0(2)], C1–Pd–C6 84.56(13) [84.8(2)], Pd–C1-N1 123.3(2) [124.3(3)],
Pd–C1–N2 130.9(3) [130.9(3)], N1–C1–N2 105.7(3) [104.8(4)], Pd–C6-
N3 123.3(2) [123.9(3)], Pd–C6–N4 131.6(3) [130.9(3)], N3–C6–N4
105.0(3) [105.2(4)], N1–C5-N3 109.3(3) [108.8(4)].

H.V. Huynh et al. / Journal of Organometallic Chemistry 689 (2004) 1766–1770
1769
3
. Experimental
C, 30.02; H, 2.09; N, 9.04%. 1HNMR (300 MHz,
3
DMSO-d6): d 7.67 (d, J(H,H) ¼ 1.5 Hz, 2H, CH), 7.40
3
3
.1. General procedures
(d, J(H,H) ¼ 1.5 Hz, 2H, CH), 6.36 (s, 2H, CH2), 3.75
1
3
1
(
s, 6H, NCH3). C{ H} NMR (75.48 MHz, DMSO-
2
All manipulations were performed in an atmosphere
of dry nitrogen by standard Schlenk techniques. All
solvents were used as received and degassed prior to use.
d6): d 159.7 (t, J(C,F) ¼ 24.7 Hz, COO), 149.3 (s, N–C–
N), 123.8 (s, CH), 122.2 (s, CH), 119.0 (qt,
2
1
J(C,F) ¼ 285.7 Hz, JðC; F Þ ¼ 36.0 Hz, CF ), 116.8 (tq,
3
0
0
1
2
1
,1 -dimethyl-3,3 -methylenediimidazolium diiodide and
0
J(C,F) ¼ 263.5 Hz, J(C,F) ¼ 37.0 Hz, CF ), 62.2 (s,
2
0
0
19
[{1,1 -dimethyl-3,3 -methylenediimidazoline-2,2 -diylid-
ene}palladium(II) diiodide] (1) were prepared according
CH2), 36.7 (s, CH3). F NMR (282.38 MHz, DMSO-
d6): d )77.07 (s, CF3), )113.58 (s, CF2). MS (ESI,
þ
to the literature procedures [8]. Pd(OAc)2 was purchased
ꢂ
positive ions): m=z: 1054 [2M–O2CCF2CF3] , 395 [M–
þ
from Avocado , silver carboxylates from Sigma–Al-
O2CCF2CF3] .
drich and used as received. H-, 13C- and 19F NMR
ꢂ
1
0
0
spectra were recorded on Bruker AC 200 or Bruker
ACF 300 spectrometers using Me Si as internal and
3.4. Synthesis of {1,1 -dimethyl-3,3 -methylenediimidazo-
0
line-2,2 -diylidene}-palladium(II) bis(heptafluorobuty-
rate) (4)
4
CCl F as an external standard. ESI mass spectra were
3
obtained using a Finnigan MAT LCQ spectrometer.
Elemental analyses were performed on a Perkin–Elmer
PE 2400 elemental analyzer at the Department of
Chemistry, National University of Singapore.
Complex 4 was prepared like 2 an 3 from 1 (300 mg,
0.68 mmol) and AgO2CCF2CF2CF3 (301 mg, 1.36
mmol). The off white crude product was brought into a
Soxhlet-thimble and extracted with dichloromethane (50
ml). Evaporation of the solvent afforded a white powder
(400 mg, 83%). Slow evaporation at ambient tempera-
ture of a concentrated acetonitrile/toluene solution af-
forded transparent plates suitable for X-ray diffraction
studies. Anal. Calc. for C17H12F14N4O4Pd: C, 28.81; H,
0
0
3
line-2,2 -diylidene}-palladium(II) bis(trifluoroacetate)
.2. Synthesis of {1,1 -dimethyl-3,3 -methylenediimidazo-
0
(
2)
A mixture of 1 (300 mg, 0.68 mmol) and AgO2CCF3
301 mg, 1.36 mmol) was suspended in acetonitrile (40
1
(
1.71; N, 7.91. Found: C, 29.19; H, 1.93; N, 7.90%. H
3
ml) and stirred at 70 ꢁC for 12 hours shielded from light.
The resulting brownish suspension was filtered from the
precipitated AgI over celite and the acetonitrile was re-
moved in vacuo to give the crude product as an off-white
solid. Recrystallization from acetone/hexane gave the
product as an analytically pure white solid (249 mg, 0.49
mmol, 72%). Anal. Calc. for C13H12F6N4O4Pd: C,
NMR (200 MHz, DMSO-d6): d 7.67 (d, J(H,H) ¼ 1.8
3
Hz, 2H, CH), 7.40 (d, J(H,H) ¼ 1.8 Hz, 2H, CH), 6.36
1
3
1
(s, 2H, CH ), 3.75 (s, 6H, NCH ). C{ H} NMR (50.33
2
3
2
MHz, DMSO-d ): d 159.2 (t, J(C,F) ¼ 23.7 Hz, COO),
6
149.1 (s, N–C–N), 123.5 (s, CH), 122.0 (s, CH), 117.6
1
2
(qt, J(C,F) ¼ 287.8 Hz, J(C,F) ¼ 34.7 Hz, CF3), 108.7
1
1
(m, J(C,F) ¼ 263.0 Hz, CF2CF3), 108.1 (tt, J(C,F) ¼
2
3
1
0.70; H, 2.38; N, 11.01. Found: C, 30.79; H, 2.69; N,
1
264.7 Hz, J(C,F) ¼ 30.8 Hz, CF2COO), 62.0 (s, CH2),
19
1.04%. H NMR (300 MHz, DMSO-d6): d 7.67 (d,
36.4 (s, CH3). F NMR (188.29 MHz, DMSO-d6): d
3
3
3
J(H,H) ¼ 2.2 Hz, 2H, CH), 7.40 (d, J(H,H) ¼ 2.2 Hz, 2
)75.30 (t, J(F,F) ¼ 8.3 Hz, 3 F, CF3), 110.87 (q,
13
1
3
H, CH), 6.34 (s, 2H, CH ), 3.76 (s, 6H, NCH ). C{ H}
2
J(F,F) ¼ 8.3 Hz, 2 F, CF ), )121.31 (br, 2 F, CF -
3
2
2
NMR (75.48 MHz, DMSO-d ):
6
d
159.8 (q,
COO). MS (ESI, positive ions): m=z: 1202 [2M–
2
þ
O CCF CF CF ] , 495 [M–O CCF CF CF ] .
2 2 2 3 2 2 2
þ
J(C,F) ¼ 28.4 Hz, COO), 148.9 (s, N–C–N), 123.8 (s,
3
1
CH), 122.2 (s, CH), 116.5 (q, J(C,F) ¼ 295.0 Hz, CF3),
19
6
2.2 (s, CH2), 36.7 (s, CH3). F NMR (282.38 MHz,
3.5. Selected crystallographic details for 3
DMSO-d6): d )101.31 (s, CF3). MS (ESI, positive ions):
þ
þ
m=z: 904 [2M–O2CCF3] , 395 [M–O2CCF3] .
Colorless crystals of 3 were obtained from a con-
centrated acetonitrile/toluene solution by evaporation of
the solvent. Selected crystallographic details for 3: size
of data crystal 0.21 · 0.17 · 0.11 mm, formula
C H F N O Pd, M ¼ 608:69 amu, triclinic, space
0
0
3.3. Synthesis of {1,1 -dimethyl-3,3 -methylenediimidazo-
0
line-2,2 -diylidene}-palladium(II) bis(pentafluoropropio-
nate) (3)
1
5
12 10
4
4
ꢁ
ꢀ
ꢀ
group P1 (No. 2), a ¼ 8:6909ð13Þ A, b ¼ 10:1922ð15Þ A,
ꢀ
Complex 3 was prepared in analogy to 2 from 1 (300
mg, 0.68 mmol) and AgO2CCF2CF3 (370 mg, 1.37
mmol). Yield: 393 mg (0.65 mmol, 95%). Slow evapo-
ration at ambient temperature of a concentrated aceto-
nitrile/toluene solution yielded transparent prisms
suitable for X-ray diffraction studies. Anal. Calc. for
C H F N O Pd: C, 29.60; H, 1.99; N, 9.20. Found:
c ¼ 11:676ð2Þ A, a ¼ 90:023ð3Þꢁ, b ¼ 97:936ð3Þꢁ,
ꢀ
3
c ¼ 95:599ð3Þꢁ, V ¼ 1019:4ð3Þ A , Z ¼ 2, q ¼ 1:983 g
calc
ꢀ
3
ꢀ1
cm , Mo Ka radiation, l(Mo Ka) ¼ 1.033 mm . 4665
symmetry independent diffraction data were measured
at 203(2) K in the 2H-range 3–55ꢁ. Structure solution
with Patterson and refinement with Fourier methods,
2
refinement (on F ) of positional parameters of all
1
5
12 10
4
4

1770
H.V. Huynh et al. / Journal of Organometallic Chemistry 689 (2004) 1766–1770
non-hydrogen atoms with anisotropic thermal parame-
ters. R ¼ 0:040, wR2 ¼ 0:104 for 4133 structure factors
I P 2rðIÞ and 309 refined parameters, maximum resid-
F.E.H. We also thank T. Pape for assistance in X-ray
crystal structure analysis.
ꢀ
ꢀ3
ual electron density 0.87 ()0.55) e A hydrogen atoms
reside on calculated positions and were refined as riding
atoms. All calculations were carried out with the SHELX
program package [13,14].
References
[
1] C. Oldham, in: G. Wilkinson, R.D. Gillard, J.A. McCleverty
(Eds.), Comprehensive Coordination Chemistry, vol. 2, Pergamon
Press, Oxford, 1987, p. 435 (Chapter 15.6).
3
.6. Selected crystallographic details for 4
[
[
2] F. Ozawa, A. Kubo, T. Hayashi, Chem. Lett. (1992) 2177.
3] (a) C. Amatore, A. Jutand, M.A. M’Barki, Organometallics 11
Colorless crystals of 4 were obtained from a con-
(
(
1992) 3009;
b) C. Amatore, E. Carr ꢂe , A. Jutand, M.A. M’Barki, Organo-
centrated acetonitrile/toluene solution by evaporation of
the solvent. Selected crystallographic details for 4: size
of data crystal 0.23 · 0.11 · 0.04 mm, formula
C H F N O Pd, M ¼ 708:71 amu, triclinic, space
metallics 14 (1995) 1818;
(c) C. Amatore, E. Carr ꢂe , A. Jutand, M.A. M’Barki, G. Meyer,
Organometallics 14 (1995) 5605;
(d) C. Amatore, A. Jutand, J. Organomet. Chem. 576 (1999) 254;
1
7
12 14
4
4
ꢁ
ꢀ
ꢀ
group P1 (No. 2), a ¼ 8:504ð2Þ A, b ¼ 10:245ð3Þ A,
(
e) C. Amatore, A. Jutand, Acc. Chem. Res. 33 (2000) 314.
ꢀ
c ¼ 12:634ð3Þ A, a ¼ 99:891ð4Þꢁ, b ¼ 91:770ð5Þꢁ,
[
[
4] (a) A. Marson, A.B. van Oort, W.P. Mul, Eur. J. Inorg. Chem.
(2002) 3028;
ꢀ
3
c ¼ 95:223ð5Þꢁ, V ¼ 1183:9ð5Þ A , Z ¼ 2, q ¼ 1:988 g
calc
ꢀ
3
ꢀ1
cm , Mo Ka radiation, l(Mo Ka) ¼ 0.928 mm . 4146
symmetry independent diffraction data were measured
at 123(2) K in the 2H-range 3–50ꢁ. Structure solution
with Patterson and refinement with Fourier methods,
(b) C. Bianchini, H.M. Lee, A. Meli, W. Oberhauser, M.
Peruzzini, F. Vizza, Organometallics 21 (2002) 16;
(
(
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2
refinement (on F ) of positional parameters of all non-
hydrogen atoms with anisotropic thermal parameters.
Hydrogen positions were identified and refined with
isotropic thermal parameters. R ¼ 0:040, wR2 ¼ 0:104
for 3569 structure factors I P 2rðIÞ and 409 refined
parameters, maximum residual electron density 1.22
(
(
(
(
c) A. de Meijere, F.E. Meyer, Angew. Chem., Int. Ed. Engl. 33
1994) 2379;
d) W. Cabri, I. Candiani, Acc. Chem. Res. 28 (1995) 2;
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[
[
6] (a) Y.C. Neo, J.J. Vittal, T.S.A. Hor, J. Chem. Soc., Dalton
Trans. (2002) 337;
ꢀ
ꢀ3
(
)0.52) e A . All calculations were carried out with the
(b) Y.C. Neo, J.S.L. Yeo, P.M.N. Low, S.W. Chien, T.C.W.
Mak, J.J. Vittal, T.S.A. Hor, J. Organomet. Chem. 658 (2002) 159.
SHELX program package [13,14].
7] (a) For reviews, see: W.A. Herrmann, K. K o€ cher, Angew. Chem.
1
09 (1997) 2256;
4
. Supplementary material
(
(
(
b) W.A. Herrmann, K. K o€ cher, Angew. Chem., Int. Ed. Engl. 36
1997) 2162;
c) W.A. Herrmann, Angew. Chem. 114 (2002) 1342, and
Further details of the crystal structure investigations
excluding structure factors) may be obtained free of
references cited within;
d) W.A. Herrmann, Angew. Chem. Int. Ed. 41 (2002) 1290.
(
(
charge from the Cambridge Crystallographic Data
Center, 12 Union Road, Cambridge CB2 1ZE, UK (e-
mail: deposit@ccdc.cam.ac.uk) on quoting the deposi-
tory numbers CCDC 223475 for 3 and CCDC 223476
for 4.
[
[
8] (a) W.A. Hermann, M. Elison, J. Fischer, C. K o€ cher, G.R.J.
Artus, Angew. Chem. 107 (1995) 2602;
(b) W.A. Hermann, M. Elison, J. Fischer, C. K o€ cher, G.R.J.
Artus, Angew. Chem., Int. Ed. Engl. 34 (1995) 2371;
(c) W.A. Herrmann, C.-P. Reisinger, M. Spiegler, J. Organomet.
Chem. 557 (1998) 93.
9] W.A. Herrmann, J. Schwarz, M.G. Gardiner, M. Spiegler, J.
Organomet. Chem. 575 (1999) 80.
€
Acknowledgements
[10] (a) K. Ofele, W.A. Herrmann, D. Mihalios, M. Elison, E.
Herdtweck, T. Priermeier, P. Kiprof, J. Organomet. Chem. 498
(
(
1995) 1;
b) W.A. Herrmann, J. Schwarz, M.G. Gardiner, Organometal-
H.V.H. and T.S.A.H. acknowledge the National
University of Singapore for financial support (R 143-
lics 18 (1999) 4082.
11] F.E. Hahn, M. Foth, J. Organomet. Chem. 585 (1999) 241.
0
00-195-101) and technical assistance from our depart-
[
ment. We are also grateful to the Alexander von Hum-
boldt Foundation (fellowship for H.V.H. and research
stipend for T.S.A.H.) for supporting our collaboration
with the WWU M u€ nster. Financial support by the
Fonds der Chemischen Industrie and the Deutsche
Forschungsgemeinschaft is gratefully acknowledged by
[12] F.E. Hahn, L. Wittenbecher, D. Le Van, R. Fr o€ hlich, Angew.
Chem. 112 (2000) 551;
Angew. Chem. Int. Ed. 39 (2000) 541.
[
[
13] G.M. Sheldrick, SHELXS-97, Acta Crystallogr. Sect. A 46 (1990)
67.
4
14] G.M. Sheldrick, SHELXL-97, Universit €a t G o€ ttingen, G o€ ttingen,
Germany, 1997.