Bimacrocyclic NHC transition metal complexes

Article abstract of DOI:10.1016/j.jorganchem.2007.11.064

The preparation of seven concave NHC metal complexes derived from bimacrocyclic imidazolinium salt 1 is reported. The silver complex 2, obtained in 86% yield by reacting 1 with silver(I) oxide, was used to give copper complex 3, rhodium complex 5 and iridium complex 6 by transmetalation in good yields. Palladium complex 4 was obtained by reaction of the azolium salt 1 with palladium dichloride in 3-chloropyridine. The rhodium and iridium dicarbonyl complexes 7 and 8 were prepared via ligand exchange from the COD complexes 5 and 6. Silver complex 2, copper complex 3 and palladium complex 4 were characterized by single-crystal X-ray analysis. Silver complex 2 and copper complex 3 were tested in the cyclopropanation of styrene and indene with EDA (ethyl diazoacetate), where good results were obtained with 3, while low conversion and catalyst decomposition was observed with 2.

Full text of DOI:10.1016/j.jorganchem.2007.11.064

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 923–932
www.elsevier.com/locate/jorganchem
q
Bimacrocyclic NHC transition metal complexes
a
b
a,
*
Ole Winkelmann , Christian N a¨ ther , Ulrich L u¨ ning
a
Otto-Diels-Institut f u¨ r Organische Chemie, Christian-Albrechts-Universit a¨ t zu Kiel, Olshausenstraße 40, D-24098 Kiel, Germany
b
Institut f u¨ r Anorganische Chemie, Christian-Albrechts-Universit a¨ t zu Kiel, Olshausenstraße 40, D-24098 Kiel, Germany
Received 1 November 2007; received in revised form 27 November 2007; accepted 28 November 2007
Available online 14 December 2007
Abstract
The preparation of seven concave NHC metal complexes derived from bimacrocyclic imidazolinium salt 1 is reported. The silver com-
plex 2, obtained in 86% yield by reacting 1 with silver(I) oxide, was used to give copper complex 3, rhodium complex 5 and iridium com-
plex 6 by transmetalation in good yields. Palladium complex 4 was obtained by reaction of the azolium salt 1 with palladium dichloride in
3
-chloropyridine. The rhodium and iridium dicarbonyl complexes 7 and 8 were prepared via ligand exchange from the COD complexes 5
and 6. Silver complex 2, copper complex 3 and palladium complex 4 were characterized by single-crystal X-ray analysis. Silver complex 2
and copper complex 3 were tested in the cyclopropanation of styrene and indene with EDA (ethyl diazoacetate), where good results were
obtained with 3, while low conversion and catalyst decomposition was observed with 2.
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Carbenes; Bimacrocycles; Transmetalation; N-heterocyclic carbenes; Homogeneous catalysis; Cyclopropanation
1
. Introduction
been shown to possess increased stability and catalytic
activity in numerous reactions, the second generation of
Grubbs’ catalyst for olefin metathesis being a prominent
example [10]. Besides their unique electronic properties,
the steric demand of the NHC ligands is an important
factor in cross-coupling reactions, and bulky NHC have
been synthesized for challenging Suzuki-Miyaura [11] or
Sonogashira [12] couplings. We have recently reported
the synthesis of bimacrocyclic imidazolinium ions as pre-
cursors to respective NHC [13], expecting to effect reactiv-
ity and selectivity due to the tailored concave structure of
the ligands. In this contribution, we report the synthesis
of seven NHC metal complexes derived from the imidaz-
olinium salt 1 [13a] and preliminary results on their cata-
lytic activity.
Since the first reports of N-heterocyclic carbene (NHC)
¨
metal complexes by Wanzlick and Sch o¨ nherr [1] and Ofele
2] in 1968 and the isolation of a stable crystalline carbene
[
by Arduengo et al. [3] in 1991, NHC and their coordina-
tion chemistry are an emerging field of research [4]. Nota-
bly, NHC also exhibit excellent catalytic activity in metal-
free organocatalysis [5], including umpolung and conden-
sation of carbonyl compounds [6] and transesterification
reactions [7]. As ligands, the nucleophilic NHC are strong
two-electron r-donors, displaying similar ligand proper-
ties as trialkylphosphines [8]. The extent of their p-accept-
ing ability is under investigation [9]. In comparison to
related phosphine complexes, NHC metal complexes have
q
Concave reagents, Part ##. For part ###, see (current numbers will be inserted in the proofs).
Corresponding author. Tel.: +49 431 880 2450; fax: +49 431 880 1558.
E-mail address: luening@oc.uni-kiel.de (U. L u¨ ning).
*
0
022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.11.064

924
O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
Cl
X
X
X
X
O
O
O
O
O
O
N
N
Ag2O
N
OX
N
CuCl
N
OX
N
O
O
O
O
Ag
Cl
Cu
Cl
1
: X = (CH2)
8
2
3
N
[
M(COD)Cl]2
Cl
PdCl K CO
3
M = Rh, Ir
2,
2
X
X
X
O
O
O
O
N
O
O
N
OX
Cl Pd Cl
N
N
OX
Cl
N
OX
Cl
N
CO
O
O
O
M
M
CO
N
CO
Cl
5: M = Rh
: M = Ir
7: M = Rh
8: M = Ir
4
6
1
3
2
. Results and discussion
.1. Synthesis and reactivity of silver complex 2 and copper
complex 3
bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), the C reso-
nance for C-2 could not be observed at natural abundance
of the C isotope, but for the C labeled complex it was
observed with resolved Ag– C coupling (185 ppm,
1
3
13
2
1
3
1
1
J107AgC = 234 Hz, J
= 270 Hz) [20d]. In all cases,
109AgC
The reaction of azolium salt 1 with silver(I) oxide in
dichloromethane resulted in the formation of complex 2 in
6% yield, with no requirement to exclude oxygen or mois-
the ratio of the magnetogyric constants of the silver nuclei
is reflected by the observed coupling constants.
8
Ag(I)–NHC complexes possess a great structural diver-
sity with various ionic and neutral structures in the solid
state [14,20e]. The crystal structure analysis of 2 revealed
a monomeric structure with an almost linear coordinated
silver atom, the angle C1–Ag1–Cl1 being 178.24(7)° (see
ture from the reaction mixture. Ag(I)–NHC complexes are
frequently used as carbene transfer reagents to produce
NHC metal complexes by transmetalation, avoiding the
handling of the sensitive free carbenes [14]. Besides this
important application, Ag(I)–NHC have been reported to
catalyze the diboration of alkenes [15], carbene transfer from
EDA (ethyl diazoacetate) [16] and the hydrosilylation of
aldehydes [17]. The thermal decomposition of Ag(I)–NHC
was used to generate free carbenes as catalysts for the ring-
opening polymerization of lactide and transesterification
reactions [18]. The NHC migration in transmetalation reac-
tions is explained by the lability of the Ag–C bond, with the
Figs. 1 and 2). In both ESI and LD-ToF mass spectra,
+
however, a dimeric (NHC) Ag cation was observed with
2
+
high intensity, while (NHC)Ag was not observed. The
bond lengths C1–Ag1 and Cl1–Ag1 are 2.084(3) A and
2.3282(7) A, respectively, the internal ring angle N1–C1–
˚
˚
N2 is 108.3(2)°, and these data are comparable to those
reported for other Ag(I)–NHC [20a,20d,20e]. In contrast
to IMesAgCl and azolium salt 1, the complex 2 does not
possess a crystallographic twofold axis bisecting the hetero-
cycle, with the torsion angles C1–N1–C4–C9 and C1–N2–
C23–C18 being 78.66(1)° and 63.16(1)°, respectively, and
107,109
13
13
lack of
Ag– C coupling in the C NMR being a proof
of this fluxionality (on the NMR timescale) in solution [19].
1
3
The C resonance for the carbene carbon atom C-2 in 2,
˚
however, was observed with low intensity as a pair of well
four different Ag–O distances, which are 3.606(5) A for
1
˚
˚
resolved doublets at 209.7 ppm ( J
= 234 Hz,
07AgC
Ag1–O1, 3.174(4) A for Ag1–O2, 4.937(4) A for Ag1–O3
1
1
˚
J109AgC = 270 Hz), and also the resonance for C-4,5 of the
and 4.621(12) A for Ag1–O4. This desymmetrization is
3
NHC at 50.6 ppm was split into a doublet ( J
= 8.6 Hz).
probably due to packing effects, and the structure is flexible
AgC
1
13
To the best of our knowledge, there are eight examples of
in solution as indicated by both H and C NMR spectra.
The chlorine atom is in vague contact with two of the pro-
tons in 4,5-position of the neighbouring heterocycle, with
1
3
Ag(I)–NHC with resolved Ag– C couplings reported in
the literature [19a,20], and some of these complexes were
used in transmetalations. For IMesAgCl (IMes = 1,3-
˚
˚
distances of 2.971(7) A and 2.978(5) A, respectively.

O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
925
Fig. 3), the bond distances Cu1–C1, Cu1–Cl1 are
˚
˚
1
.8852(19) A and 2.1172(6) A, respectively, in good
agreement with the data reported for IPrCuCl [21b]
IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene)
(
and SIMesCuCl [21c] (SIMes = 1,3-bis(2,4,6-trimethyl-
phenyl)imidazolidin-2-ylidene).
The bond angles C–Cu–Cl reported for these are
1
78.48(13)° (SIMesCuCl) and 180.00 (IPrCuCl), while C1–
Cu1–Cl1 is 173.44(6)° in 3, respectively. As for 2, the NHC
ligand is not C -symmetric in the solid state, and the hetero-
2
cycle is twisted out of an idealized geometry inside the bimac-
rocycle, even more expressed in 3 with torsion angles of
60.51(1)° and 61.30(1)° for C1–N1–C4–C9 and C1–N2–
C23–C18, respectively. The copper atom is bent out of the
plane of the NHC, and the torsion angles C2–N1–C1–Cu1,
C3–N2–C1–Cu1 are 169.06(0)° and 164.72(0)°, respectively.
This is possibly due to a weak attraction of the copper atom
to two of the neighbouring oxygen atoms (bond lengths
˚
Cu1–O1, Cu1–O2, Cu1–O3, Cu1–O4 are 2.925(4) A,
Fig. 1. Crystal structure of silver complex 2 with displacement ellipsoids
drawn at the 30% probability level. Five carbon atoms in one octylene
chain are disordered in two positions, and only the atoms of higher
occupancy are shown for clarity.
˚ ˚ ˚
2.868(4) A, 4.864(10) A, 4.929(14) A, respectively). The
internal ring angle N1–C1–N2 is 107.09(0)°.
Cu(I)–NHC have been reported to be beneficial catalysts
in numerous reactions, including the reduction of a,b-
unsaturated carbonyl compounds [21a], hydrosilylation of
ketones [21b,21c], [3 + 2] cycloadditions (‘‘click chemis-
try”) [22] and the methylenation of aldehydes and ketones
[
23]. As IPrCuCl is known to catalyze the cyclopropana-
tion of styrene [24] and both IPrCuCl and IPrAgCl were
reported as catalysts for carbene transfer from EDA into
unactivated C–H bonds [16], we investigated the reactivity
of the complexes 2 and 3 in the cyclopropanation of styrene
and indene with EDA (see Scheme 1 and Table 1 ).
Very low EDA consumption, along with the formation
of unidentified by-products, was observed with silver com-
Fig. 2. Space filling representation of the X-ray structure of silver complex
2, highlighting the concave structure. The chlorine atom is omitted for
clarity.
Silver complex 2 was used for transmetalation, and cop-
per complex 3 was obtained in 67% yield by stirring a solu-
tion of 2 in dichloromethane with copper(I) chloride. The
NMR spectra of the complexes 2 and 3 are very similar
1
3
1
(
the average Dd is 0.1 ppm for C and 0.01 ppm for H),
but the resonance for C-2 was observed as a singlet at
05.3 ppm for 3. Notably, the reaction of azolium salt 1
2
with sodium tert-butoxide and copper(I) chloride in THF
led to a complex mixture of unidentified products, and
complex 3 could not be obtained by this general method
Fig. 3. Crystal structure of copper complex 3 with displacement ellipsoids
drawn at the 30% probability level. The chlorine atom and all eight carbon
atoms in one octylene chain are disordered in two positions, and only the
atoms of higher occupancy are shown for clarity.
[
21]. In the crystal structure of copper complex 3 (see

926
O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
COOEt
the reaction of silver complex 2 with palladium dichloride
EDA
in 3-chloropyridine at room temperature afforded none of
2
.5 mol% cat.
13
the desired product. The C resonance for C-2 was
Scheme 1. Cyclopropanation of styrene and indene with EDA. The extra
methylene group in indene is indicated by the dashed line.
observed at 183.5 ppm for 4. In the crystal structure of 4
(see Fig. 4), the asymmetric unit contains three crystallo-
graphically independent molecules. Selected bond distances
and angles are given in Table 2.
Table 1
a
Catalytic activity of complexes 2 and 3 in the cyclopropanation of styrene
Each of the three palladium atoms adopts a slightly dis-
torted square-planar coordination, and these data are com-
parable to those reported for the respective complex using
the IPr NHC ligand [29]. In contrast to the crystal struc-
tures of azolium salt 1 and complexes 2 and 3, the two phe-
nyl substituents of the NHC are oriented almost
perpendicular to the heterocycle in 4, and the torsion
angles C1–N1–C4–C5 and C1–N2–C23–C18 are 86.06(2)°
and 87.81(2)°, which seems to be due to sterical interactions
of the ligands alkyl chains with the two chloride anions.
The internal ring angle N1–C1–N2 is 109.39(2)°. Palladium
complex 4 has not yet been tested for its catalytic properties
in cross coupling reactions because of the insufficient yield.
and indene
b,c
c
Olefine
Catalyst
Conversion (%)
d.r.
d
d
Styrene
Indene
Styrene
Indene
a
2
2
3
3
<5
<5
63 (100)
42:58
1:99
29:71 (30:70)
e
f
d,f
e
100
22:78
Conditions: 25 lmol catalyst, 1 mmol EDA, 10 mmol olefine, 16 h at
room temperature.
b
Based on EDA.
Determined by GC, average of two experiments.
Diastereomeric ratio cis:trans.
Diastereomeric ratio endo:exo.
c
d
e
f
48 hours reaction time.
plex 2. Product formation could not be raised with higher
catalyst loadings or longer reaction time, and a precipitate
of silver chloride was observed in the reaction mixtures,
indicating catalyst decomposition. In contrast to these
unpleasant results, copper complex 3 afforded clean con-
version to cyclopropanation products, along with the for-
mation of maleate and fumarate (approx. 20%), known
by-products of the reaction. The cis:trans ratio (30:70)
observed in the cyclopropanation of styrene is comparable
to that reported for IPrCuCl (32:68). A higher reactivity
and selectivity compared to styrene was observed with
indene, due to the more electron-rich double bond and a
greater steric hindrance of the substrate.
2
.2. Synthesis of palladium complex 4
In palladium catalyzed C–C and C–N cross coupling
reactions, NHC have shown to be valuable ligands, allow-
ing for the oxidative addition of challenging substrates (e.g.
hindered aryl-chlorides) due to their electronic properties,
while their bulkyness facilitates reductive elimination [4f].
Besides formation of the active catalyst from a palladium
source and the azolium precursor in situ, stable Pd–NHC
precatalysts are used, which allow to control for the opti-
mum Pd:NHC ratio of 1:1 [25] and are activated upon dis-
sociation of a second, labile ligand. NHC-substituted
phospha-palladacycles [26], N-palladacycles [27] and palla-
dium-allyl complexes [28] were found to be beneficial in this
respect. The heating of azolium salts with palladium
dichloride and potassium carbonate in 3-chloropyridine
has recently been reported to produce Pd(II)–NHC that
were found to be highly active in Suzuki-Miyaura [29],
Negishi [30] and Kumada-Tamao-Corriu [31] cross cou-
pling reactions.
Fig. 4. Crystal structure of palladium complex 4 with displacement
ellipsoids drawn at the 30% probability level. Only one of the three
crystallographically independent molecules is represented.
Table 2
˚
Selected bond lengths (A) and bond angles (°) for palladium complex 4
Pd1
Pd2
Pd3
Bond lengths
Pd–C1/C41/C81
Pd–N3/N13/N23
Pd–Cl1/Cl11/Cl22
Pd–Cl2/Cl12/Cl23
1.963(4)
2.178(5)
2.308(12)
2.294(13)
1.949(19)
2.148(11)
2.316(11)
2.294(11)
1.954(2)
2.175(2)
2.308(9)
2.313(8)
Bond angles
C–Pd–N
Cl–Pd–Cl
179.64(1)
175.22(1)
178.19(1)
177.40(1)
178.52(1)
176.03(1)
Subjecting azolium salt 1 to these reaction conditions
gave palladium complex 4 in very poor yield (5%), while
Pd1, Pd2, Pd3 belong to the respective crystallographically independent
complexes.

O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
927
The synthesis and reactivity of a related NHC–palladium-
allyl complex is currently under investigation in our
laboratory.
to be significantly more electron donating. The CO stretch-
ing frequencies are listed in Table 3.
The complexes were synthesized by transmetalation
4
from silver complex 2 with the respective chloro(g -1,5-
2
.3. Synthesis of rhodium and iridium complexes 5, 6, 7, 8
cyclooctadiene = COD)metal dimers to give rhodium com-
plex 5 and iridium complex 6 in good yields (69% and 64%,
respectively). Both compounds display restricted rotation
about the metal–carbene bond as can be judged from the
NMR spectra. A similar behavior of Rh(I)– and Ir(I)–
NHC COD complexes has been described before and
We finally prepared the rhodium complex 7 and iridium
complex 8 to determine their carbonyl stretching frequen-
cies which are a popular indirect measure of the ligands’
electronic properties [32,11]. A low stretching frequency
1
3
(
wavenumber) of CO corresponds to strong r-donation
explained in terms of steric interactions [32c]. The C res-
of the NHC. By using a linear fit procedure [32c], the CO
stretching frequencies of respective Ir(I)–NHC can be used
to estimate Tolman’s electronic parameter (TEP) [33],
which is well documented for various phosphines. The
CO stretching frequencies and TEP values of respective
NHC complexes fall in a narrow range, and the NHC are
more electron donating than the most donating phos-
phines. Compared to standard NHC, our new ligand seems
onance for C-2 was observed as a doublet at 215.2 ppm
1
( J
= 48.4 Hz) for 5, while the resonance for C-2 could
RhC
not be observed for 6. By bubbling CO through solutions
of 5 and 6 in dichloromethane, the complexes 7 and 8 were
produced in almost quantitative yields (91% and 93%,
respectively). The spectra are consistent with the cis-con-
formation of both carbonyl ligands, showing two strong
~m CO bands in the IR spectra, and three signals are observed
1
3
in the C NMR spectra between 210 and 165 ppm for both
and 8, corresponding to the two CO carbon atoms and
7
Table 3
13
C-2. By using C labeled CO in the synthesis of respective
Rh(I)–NHC (derived from pyrazolium, imidazolium and
benzimidazolium), Herrmann et al. could demonstrate that
the two CO carbon atoms resonate at lower field than the
carbene carbon atom C-2 [32e]. The C-2 resonance for rho-
Carbonyl stretching frequencies ~m (measured in dichloromethane) of
complexes 7, 8 and related complexes known from the literature
1
ꢀ1
a
ꢀ1
Compound
~m ðCOÞ ðcmꢀ
Þ
~m ðCOÞ ðcm
Þ
TEP (cm
)
b
b
7
2069 (2062)
1995 (1984)
–
–
c
b
b
SIMesRhCl(CO)
2
(2081)
(1996)
dium complex 7, however, was undoubtedly identified to
8
2058
2068
2064
1977
1981
1982
2050
2055
2054
1
appear at 206.6 ppm ( J
= 41.3 Hz) by observing the
RhC
c
SIMesIrCl(CO)
ICyIrCl(CO)
2
c
correlation with 4,5-H in the HMBC (heteronuclear multi-
2
ple bond correlation) spectrum, and so the two resonances
a
TEPðTolman’s electronic parameterÞ ¼ 0:722½ ~m averageðCOÞꢁ þ 593 cmꢀ1
,
1
at
( J
186.6 ppm
( J
= 53.3 Hz)
and
183.2 ppm
RhC
according to Ref. [32c].
b
1
= 75.6 Hz) must be assigned to the CO ligands
RhC
Measured in KBr.
Literature values [32b,32f,32g]; SIMes = 1,3-bis(2,4,6-trimethyl-
c
(see Fig. 5). For iridium complex 8, this correlation could
phenyl)imidazolidin-2-ylidene, ICy = 1,3-dicyclohexylimidazol-2-ylidene.
not be observed and the assignment remains uncertain.
Fig. 5. HMBC spectrum (313 K, parts) of rhodium complex 7 used to assign the carbon atoms of the NHC (C-2, 206.6 ppm) and the carbonyl ligands
186.6 and 183.2 ppm, respectively). The cross-peak between C-2 and H-4,5 is indicated by an arrow.
(

928
O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
3
3
. Conclusion
J = 8.5 Hz, 4H, Ar-H-3,5), 4.12 (m , 4H, OCH H ), 4.01
c a b
(
s, 4H, Im-4,5-H), 3.99 (m , 4H, OCH H ), 1.79 (m ,
c a b c
1
1
3
Bimacrocyclic NHC metal complexes can readily be
4H), 1.70 (m , 8H), 1.48 (m , 12H). C{ H} NMR
c c
(125 MHz, CDCl ): d (ppm) = 209.7 (dd, J107AgC =
3
234 Hz, J109AgC = 270 Hz, Im-C-2), 156.5 (Ar-C-2,6),
1
obtained from either azolium salt 1 or via transmetalation
from silver complex 2. All of the synthesized complexes are
stable under ambient conditions, and copper complex 3
proved to be active as a catalyst in carbene transfer reac-
tions. Compared to standard NHC, our new concave
ligand seems to be more electron donating. The reactivity
of the synthesized complexes and the accessibility of other
concave NHC metal complexes are under investigation.
1
129.2 (Ar-C-4), 118.2 (Ar-C-1), 104.7 (Ar-C-3,5), 68.1
3
(OCH ), 50.6 (d, JAgC = 8.6 Hz, Im-C-4,5), 28.5, 26.4,
2
23.8. MS (ESI, MeOH): m/z (%) = 1119.54/1121.54 (87/
+
+
100, [(C H N O ) Ag] ), 507.33 (30, [C H N O ] ).
3
1
42
2
4 2
31 43
2
4
MS
(LD-ToF):
m/z
IR
(%) = 1119/1121
(70/100,
+
ꢀ1
[(C H N O ) Ag] ).
(KBr):
~m ðcm Þ ¼ 2936;
3
1
42
2
4 2
2854; 1596; 1499; 1463; 1268; 1099; 775; 730: Anal. Calc.
4
. Experimental
for C H AgClN O (649.99): C, 57.28; H, 6.51; N, 4.31.
3
1
42
2
4
Found: C, 57.48; H, 6.61; N, 4.32%.
4
.1. General
4.3. Synthesis of chloro(2,11,13,22-tetraoxa-1,12(1,3,2)-
dibenzena-23-(1,3)-imidazolidina-bicyclo[10.10.1]-
During all reactions and manipulations, no precautions
2
tricosaphane-23 -ylidene)copper(I) (3)
were taken to exclude oxygen or moisture, except for the
cyclopropanation reactions. The NHC precursor 1 was
prepared according to the method reported earlier [13a].
Melting points were determined with a B u¨ chi 530 melting
A suspension of copper(I) chloride (32 mg, 0.32 mmol)
and silver complex 2 (210 mg, 323 lmol) in 15 mL of
dichloromethane was stirred for 20 h at room temperature.
The reaction mixture was passed through a short pad of sil-
ica gel, eluting with dichloromethane. After removal of the
solvent in vacuo, 3 was obtained as a colorless solid. Yield:
1
13
point apparatus. H and C NMR spectra were recorded
with Bruker DRX 500 or AV 600 instruments at room tem-
perature and referenced to tetramethylsilane. Assignments
are supported by COSY, HSQC and HMBC. The HMBC
spectrum of complex 7 was recorded at 313 K, with the first
131 mg (216 lmol, 67%).
1
1
(
/2J delay being adjusted for a coupling constant of 5 Hz
M.p. 207 °C.
H
NMR (600 MHz, CDCl3):
d
1
3
3
D = 10 ms). The C resonances for the carbene carbon
(ppm) = 7.19 (t, J = 8.4 Hz, 2H, Ar-H-4), 6.57 (d,
3
atoms C-2 were observed with low intensities for all com-
pounds. NMR multiplicities are abbreviated as follows:
s = singlet, d = doublet, t = triplet, m(c) = multiplet (cen-
tered), br = broad signal. The following abbreviations are
used for assignments: Ar = aromatic, Im = imidazolidin,
Py = 3-chloropyridine. Mass spectra were obtained using
either an Applied Biosystems Mariner Spectrometry Work-
station (ESI), Bruker Biflex III (LD-ToF) or Finnigan
MAT 8200 (EI). IR spectra were recorded with a Perkin–
J = 8.5 Hz, 4H, Ar-H-3,5), 4.12 (m , 4H, OCH H ), 4.00
c
a
b
(m , 4H, OCH H ), 3.99 (s, 4H, Im-4,5-H), 1.81 (m ,
c
a
b
c
1
3
1
4H), 1.70 (m , 8H), 1.47 (m , 12H). C{ H} NMR
c
c
(150 MHz, CDCl ): d (ppm) = 205.3 (Im-C-2), 156.3 (Ar-
3
C-2,6), 128.9 (Ar-C-4), 118.2 (Ar-C-1), 104.7 (Ar-C-3,5),
68.1 (OCH ), 50.4 (Im-C-4,5), 28.5, 26.6, 24.0. MS (LD-
2
+
ToF): m/z (%) = 569 (13, [C H CuN O ] ), 507 (100,
[C H N O ] ).
1593; 1500; 1478; 1459; 1388; 1295; 1258; 1182; 1101; 772;
726: Anal. Calc. for C H ClCuN O (605.66): C, 61.47;
3
1
42
2
ꢀ1
4
+
IR
(KBr):
~m ðcm Þ ¼ 2936; 2856;
3
1
43
2
4
ꢀ1
Elmer Paragon 1000 spectrometer (a resolution of 4 cm
was used for routine spectra, while the spectra of 7 and 8
3
1
42
2
4
H, 6.99; N, 4.63. Found: C, 61.72; H, 7.19; N, 4.63%.
ꢀ
1
were recorded with a resolution of 1 cm ). Elemental anal-
yses were carried out with a EuroEA 3000 Elemental Ana-
lyzer from Euro Vector. GC analyses were performed on
an Agilent 6890 N gas chromatograph.
4.4. Synthesis of trans-dichloro(3-chloropyridine)-
(2,11,13,22-tetraoxa-1,12(1,3,2)-dibenzena-23-(1,3)-
2
imidazolidina-bicyclo[10.10.1]-tricosaphane-23 -
ylidene)palladium(II) (4)
4.2. Synthesis of chloro(2,11,13,22-tetraoxa-1,12(1,3,2)-
dibenzena-23-(1,3)-imidazolidina-bicyclo[10.10.1]-
2
tricosaphane-23 -ylidene)silver(I) (2)
A
suspension of palladium dichloride (89 mg,
0.50 mmol),
50 lmol)
imidazolinium
and potassium
chloride
1
(299 mg,
(346 mg,
5
carbonate
A suspension of silver(I) oxide (45 mg, 0.19 mmol) and
imidazolinium chloride 1 (210 mg, 387 lmol) in 10 mL of
dichloromethane was stirred for 14 h at room temperature
excluding light. The reaction mixture was passed through a
short pad of silica gel, eluting with dichloromethane. After
removal of the solvent in vacuo, 2 was obtained as a color-
2.50 mmol) in 2 mL of 3-chloropyridine was heated
for 16 h at 80 °C. After cooling, the reaction mixture
was diluted with dichloromethane and passed through
a short pad of silica gel covered by celite, eluting with
dichloromethane. The volatiles were removed in vacuo
and the crude product was purified by column chroma-
tography on silica gel [dichloromethane/ethyl acetate
less solid. Yield: 215 mg (331 lmol, 86%).
1
M.p. 229 °C.
H
NMR (500 MHz, CDCl3):
d
(3:1), R = 0.12] to give 4 as a yellow solid. Yield:
f
3
(
ppm) = 7.20 (t, J = 8.5 Hz, 2H, Ar-H-4), 6.57 (d,
18 mg (23 lmol, 5%).

O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
929
1
M.p. 233 °C.
H
NMR (600 MHz, CDCl3):
d
passed through a short pad of silica gel, eluting with dichlo-
romethane. The crude product was purified by crystallisa-
tion from dichloromethane/diethyl ether. Yellow crystals
4
(
ppm) = 8.54 (d, J = 2.4 Hz, 1H, Py-H-2), 8.46 (dd,
3
4
J = 5.5 Hz, J = 1.3 Hz, 1H, Py-H-6), 7.48 (ddd,
J = 8.2 Hz, J = 2.4 Hz, J = 1.4 Hz, 1H, Py-H-4), 7.26
t, J = 8.4 Hz, 2H, Ar-H-4), 6.99 (dd, J = 8.2 Hz,
J = 5.5 Hz, 1H, Py-H-5), 6.60 (d, J = 8.4 Hz, 4H, Ar-
H-3,5), 4.20 (m , 4H, OCH H ), 4.06 (s, 4H, Im-4,5-H),
3
4
4
were obtained. Yield: 83 mg (99 lmol, 64%).
3
3
1
(
M.p. 231 °C.
H
NMR (600 MHz, CDCl3):
d
3
3
3
(ppm) = 7.23 (t, J = 8.4 Hz, 2H, Ar-H-4), 6.59 (dd,
J = 0.9 Hz, 2H, Ar-H-3), 6.51 (dd,
J = 8.4 Hz, J = 1.0 Hz, 2H, Ar-H-5), 4.26 (m , 2H,
c
3
4
J = 8.4 Hz,
c
a
b
3
4
4
1
.01 (m , 4H, OCH H ), 2.09 (m , 4H), 1.75 (m , 4H),
.63 (m , 4H), 1.51 (m , 12H). C{ H} NMR (150 MHz,
c
a
b
c
c
1
3
1
OCH H ), 4.11 (m , 2H, OCH H ), 4.01–3.88 (m,
a1 b1 c a2 b2
c
c
CDCl ): d (ppm) = 183.5 (Im-C-2), 157.4 (Ar-C-2,6),
12H, OCH H , Im-4,5-H , @CH
), 3.86 (m , 2H, Im-
aCOD c
3
a
b
a
1
50.4 (Py-C-2), 149.5 (Py-C-6), 137.0 (Py-C-4), 131.7 (Py-
4,5-H ), 3.44 (br s, 2H, @CH
), 2.12 (m , 2H), 1.80
bCOD c
b
C-3), 129.3 (Ar-C-4), 124.0 (Py-C-5), 117.5 (Ar-C-1),
(m , 4H), 1.67 (m , 4H), 1.61–1.47 (m, 16H), 1.38 (m ,
2H), 1.28 (m , 4H). C{ H} NMR (150 MHz, CDCl ): d
c 3
(ppm) = 158.0 (Ar-C-6), 156.8 (Ar-C-2), 128.8 (Ar-C-4),
118.5 (Ar-C-1), 104.5 (Ar-C-3), 102.8 (Ar-C-5), 81.6
c
c
c
1
3
1
1
2
1
03.7 (Ar-C-3,5), 68.1 (OCH ), 50.5 (Im-C-4,5), 28.6,
6.8, 24.1. IR (KBr): ~m ðcm Þ ¼ 3059; 2923; 2853;
592; 1506; 1460; 1388; 1298; 1261; 1100; 1024; 802; 726:
2
ꢀ
1
(
@C H
), 68.3 (OCH ), 67.6 (OCH ), 51.4 (@C HCOD),
a
COD
2
2
b
4
4
tetraoxa-1,12(1,3,2)-dibenzena-23-(1,3)-imidazolidina-
.5. Synthesis of chloro(g -1,5-cyclooctadiene)-(2,11,13,22-
51.0 (Im-C-4,5), 33.4, 29.0, 28.9, 28.3, 26.5, 26.2, 23.3, 23.1;
no signal observed for Im-C-2. MS (EI): m/z (%) = 840/842
2
bicyclo[10.10.1]-tricosaphane-23 -ylidene)rhodium(I) (5)
+
ꢀ1
(53/100, [C H ClIrN O ] ). IR (KBr): ~m ðcm Þ ¼
3
9
54
2
4
2
920; 2863; 1593; 1498; 1479; 1459; 1426; 1295; 1259; 1103;
A solution of silver complex 2 (207 mg, 318 lmol) in
mL of dichloromethane was added to chloro(g -1,5-
770; 722: Anal. Calc. for C H ClIrN O (842.53): C,
55.60; H, 6.46; N, 3.32. Found: C, 55.66; H, 6.64; N,
3.36%.
3
9
54
2
4
4
5
cyclooctadiene)rhodium(I) dimer (79 mg, 0.16 mmol). The
reaction mixture was stirred for 16 h at room temperature
and then passed through a short pad of silica gel, eluting
with dichloromethane. The crude product was purified by
crystallisation from dichloromethane/diethyl ether. Yellow
4.7. Synthesis of cis-dicarbonylchloro(2,11,13,22-tetraoxa-
1,12(1,3,2)-dibenzena-23-(1,3)-imidazolidina-
2
bicyclo[10.10.1]-tricosaphane-23 -ylidene)rhodium(I) (7)
crystals were obtained. Yield: 165 mg (219 lmol, 69%).
1
M.p. 228 °C.
H
NMR (600 MHz, CDCl3):
d
CO was bubbled through a solution of 5 (25 mg,
33 lmol) in 2 mL of dichloromethane at 0 °C for 10 min.
The solvent was removed in vacuo, the residue was washed
with cold pentane (3 ꢂ 2 mL) and dried in vacuo. A yellow
3
(
ppm) = 7.27 (t, J = 8.4 Hz, 2H, Ar-H-4), 6.65 (dd,
J = 8.4 Hz, J = 1.1 Hz, 2H, Ar-H-3), 6.55 (dd, J =
.4 Hz, J = 1.1 Hz, 2H, Ar-H-5), 4.39 (br s, 2H,
CHaCOD), 4.30 (m , 2H, OCH H ), 4.13 (m , 2H,
OCH H ), 3.96 (mc, 2H, OCH H ), 3.91 (mc,
H, OCH H ), 3.89 (m , 2H, Im-4,5-H ), 3.83 (m , 2H,
Im-4,5-H ), 3.71 (br s, 2H, @CH
.81–1.42 (m, 28H), 1.36 (m , 2H).
150 MHz, CDCl ): d (ppm) = 215.2 (d, J
3
4
3
4
8
@
powder was obtained. Yield: 21 mg (30 lmol, 91%).
c
a1 b1
c
1
M.p. >250 °C.
H NMR (500 MHz, CDCl3): d
a2 b2
a1 b1
3
2
(ppm) = 7.24 (t, J = 8.4 Hz, 2H, Ar-H-4), 6.57 (d,
J = 8.5 Hz, 4H, Ar-H-3,5), 4.17 (m , 4H, OCH H ), 4.02
a2 b2
c
a
c
3
), 2.12 (m , 2H),
b
bCOD
c
c
a
b
1
3
1
1
(
C{ H} NMR
(s, 4H, Im-4,5-H), 3.96 (m , 4H, OCH H ), 1.94 (br s,
c a b
c
1
= 48.4 Hz,
4H), 1.76 (br s, 4H), 1.64 (m , 4H), 1.51 (br s, 12H).
3
RhC
c
1
3
1
Im-C-2), 158.2 (Ar-C-6), 156.9 (Ar-C-2), 128.9 (Ar-C-4),
18.7 (Ar-C-1), 104.7 (Ar-C-3), 102.7 (Ar-C-5), 95.9 (d,
C{ H} NMR (150 MHz, CDCl ): d (ppm) = 206.6 (d,
JRhC = 41.3 Hz, Im-C-2), 186.6 (d, JRhC = 53.3 Hz,
CO), 183.2 (d, JRhC = 75.6 Hz, CO), 157.1 (Ar-C-2,6),
129.4 (Ar-C-4), 117.6 (Ar-C-1), 104.0 (Ar-C-3,5), 68.0
3
1
1
1
1
1
JRhC = 6.7 Hz, @C H
), 68.3 (OCH ), 67.7 (OCH ),
a
COD
2
2
1
6
7.5 (d, JRhC = 14.2 Hz, @C HCOD), 50.7 (Im-C-4,5),
b
3
2.8, 28.8, 28.4, 28.3, 26.5, 26.1, 23.3, 23.1. MS (ESI,
(OCH ), 51.0 (Im-C-4,5), 28.4, 26.5, 23.4; the signal for
2
+
MeOH): m/z (%) = 717.32 (100, [C H N O Rh] ). IR
Ar-C-2,6 is broad and of low intensity. IR (CH Cl ):
3
9
54
2
4
2
2
ꢀ
1
ꢀ1
ꢀ1
(
KBr): ~m ðcm Þ ¼ 2927; 2862; 1591; 1497; 1479; 1466; 1426;
385; 1296; 1259; 1176; 1101; 770; 722: Anal. Calc. for
C H ClN O Rh (753.22): C, 62.19; H, 7.23; N, 3.72.
~m COðcm Þ ¼ 2069; 1995;
IR
(KBr):
~m ðcm Þ ¼
1
2928; 2858; 2062; 1984; 1596; 1508; 1478; 1459; 1383; 1297;
1260; 1183; 1103; 774; 726: Anal Calc. for C H
3
9
54
2
4
33 42
Found: C, 62.24; H, 7.32; N, 3.74%.
ClN O Rh (701.06): C, 56.54; H, 6.04; N, 4.00. Found:
2
6
C, 56.48; H, 6.18; N, 4.05%.
4
4
tetraoxa-1,12(1,3,2)-dibenzena-23-(1,3)-imidazolidina-
.6. Synthesis of chloro(g -1,5-cyclooctadiene)-(2,11,13,22-
4.8. Synthesis of cis-dicarbonylchloro(2,11,13,22-tetraoxa-
1,12(1,3,2)-dibenzena-23-(1,3)-imidazolidina-
2
bicyclo[10.10.1]-tricosaphane-23 -ylidene)iridium(I) (8)
2
bicyclo[10.10.1]-tricosaphane-23 -ylidene)iridium(I) (6)
Dichloromethane (8 mL) was added to a flask contain-
ing silver complex 2 (100 mg, 154 lmol) and chloro(g -
4
CO was bubbled through a solution of 6 (34 mg,
40 lmol) in 2 mL of dichloromethane at 0 °C for 10 min.
The solvent was removed in vacuo, the residue was washed
1
,5-cyclooctadiene)iridium(I) dimer (50 mg, 75 lmol). The
reaction mixture was stirred for 2 h at 40 °C and then

930
O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
with cold pentane (3 ꢂ 2 mL) and dried in vacuo. A yellow
and the silica gel was rinsed with diethylether (20 mL).
The filtrate was then filled up to 25 mL with diethylether
and analyzed by GC, following an established procedure
[34]; conditions: split ratio 11:1, injector temp. 250 °C,
detector temp. 300 °C; column: HP-5/30 m; temperature:
80 °C for 5 min, 10 °C/min until 140 °C, 1 min 140 °C,
2 °C/min until 160 °C, 1 min 160 °C, 20 °C/min until
240 °C, 20 min 240 °C.
powder was obtained. Yield: 29 mg (37 lmol, 93%).
1
M.p. 234 °C.
H
NMR (600 MHz, CDCl3):
d
3
(
ppm) = 7.24 (t, J = 8.4 Hz, 2H, Ar-H-4), 6.55 (d,
3
J = 8.4 Hz, 4H, Ar-H-3,5), 4.17 (br s, 4H, OCH H ),
a
b
4
.07–3.90 (m, 8H, 4,5-H, OCH H ), 1.95 (br s, 4H), 1.77
a b
1
3
1
(
br s, 4H), 1.64 (m , 4H), 1.52 (br s, 12H). C{ H} NMR
c
(
150 MHz, CDCl ): d (ppm) = 203.0( ), 182.2( ), 169.0( ),
3
* * *
1
57.1 (Ar-C-2,6), 129.5 (Ar-C-4), 117.2 (Ar-C-1), 103.9
(
Ar-C-3,5), 68.0 (OCH ), 51.2 (Im-C-4,5), 28.4, 26.4, 23,4;
4.10. Single-crystal X-ray structure determination of
compounds 2–4
2
:
Im-C-2 and CO, assignment uncertain; the signal for Ar-
*
C-2,6 is broad and of low intensity. IR (CH Cl ):
2
2
ꢀ
1
ꢀ1
~
2
1
m
ðcm Þ ¼ 2058; 1977;
IR
(KBr):
~m ðcm Þ ¼
General: Crystal data and details of the structure deter-
mination are given in Table 4. Suitable single crystals were
grown by slow diffusion of either diethyl ether (2, 3) or n-
pentane (4) into solutions of the respective complexes in
dichloromethane. Data collection was performed using an
STOE Imaging Plate Diffraction System (IPDS-1) with
CO
928; 2857; 2050; 1968; 1595; 1508; 1478; 1459; 1383; 1296;
183; 1101; 773; 726: Anal Calc. for C H ClIrN O
6
3
3
42
2
(
5
790.37): C, 50.15; H, 5.36; N, 3.54. Found: C, 50.57; H,
.52; N, 3.54%.
4
.9. Cyclopropanation experiments
A flask was charged with the respective catalyst
graphite-monochromated Mo Ka radiation (k =
˚
0.71073 A). Structure solutions were performed with direct
methods using SHELXS-97. Structure refinements were per-
2
(
25 lmol), EDA (114 mg, 1 mmol) and 1,2-dichloroethane
formed against F with SHELXL-97 [35]. Some of the carbon
(
2 mL). The flask was flushed with nitrogen, sealed with a
atoms in the alkyl chains of compounds 2, 3 and 4 and the
chlorine atom in 3 are disordered in two positions and were
refined using a split model. All non-hydrogen atoms except
the disordered carbon atoms of lower occupancy were
refined anisotropic. The hydrogen atoms were placed in
rubber septum and the mixture was stirred for 5 min. The
respective olefine (10 mmol) was injected via syringe and
the mixture was stirred at room temperature. After 16 h,
the mixture was passed through a short pad of silica gel
Table 4
Crystallographic data for 2–4
Compound
2
3
4
Formula
C
H42AgClN O
31 2 4
C
H42ClCuN O
31 2 4
36 3 3 4
C H46Cl N O Pd
Formula weight
Color/habit
Crystal size (mm)
Crystal system
Space group
649.99
Colorless/block
605.66
797.51
Colorless/block
0.3 ꢂ 0.1 ꢂ 0.2
Monoclinic
Yellow/block
0.5 ꢂ 0.4 ꢂ 0.3
Triclinic
0.2 ꢂ 0.14 ꢂ 0.08
Monoclinic
ꢀ
P2
1
/c (no. 14)
P2
1
/c (no. 14)
P1 (no. 2)
˚
a (A)
9.8314(6)
32.2408(15)
9.7324(6)
90
93.374(8)
90
9.5044(6)
17.1456(10)
18.3443(14)
90
92.551(8)
90
15.7630(11)
20.0189(14)
21.1372(14)
108.412(8)
90.506(8)
100.428(8)
6208.5(7)
6
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
˚
3
V (A )
3079.6(3)
4
2986.4(3)
4
Z
T (K)
l (mm
170(2)
0.778
170(2)
0.859
200(2)
0.679
ꢀ1
)
h Range (°)
2.17–22.38
± 10, ± 34, ± 10
18554
2.52–28.03
± 11, ± 22, ± 19
21940
2.28–26.02
± 19, ± 24, ± 24
48286
Index ranges (h, k, l)
Measured reflections
Independent reflections
3964
6991
23979
R
int
0.0434
0.0404
0.0387
Reflections with [I > 2r(I)]
3257
5567
17870
Parameters
370
388
1306
a
R
R
1
/wR
/wR
2
2
[I > 2r(I)]
(all data)
0.0254/0.0661
0.0330/0.0685
0.982
0.0387/0.0972
0.0516/0.1033
1.031
0.0416/0.1047
0.0592/0.1113
0.960
+0.897 and ꢀ0.681
a
1
2
a
GOF (on F )
Largest difference in peak and hole (e A
˚
ꢀ3
)
+0.356 and ꢀ0.357
+0.547 and ꢀ0.591
P
P
P
P
P
a
2
o
2
c
2
2
o
2
1=2
2
o
2
c
2
1=2
R1 ¼ ðkF oj ꢀ jF ckÞ= jF oj; wR2 ¼ f ½wðF ꢀ F Þ ꢁ= wðF Þ g ; GOF ¼ f ½wðF ꢀ F Þ ꢁ=ðn ꢀ pÞg
.

O. Winkelmann et al. / Journal of Organometallic Chemistry 693 (2008) 923–932
931
ideal positions and refined using a riding model. The asym-
metric unit of 4 contains three crystallographically inde-
pendent molecules.
[12] Y. Ma, C. Song, W. Jiang, Q. Wu, Y. Wang, X. Liu, M.B. Andrus,
Org. Lett. 5 (2003) 3317.
[
13] (a) O. Winkelmann, C. N a¨ ther, U. L u¨ ning, Eur. J. Org. Chem. (2007)
81;
b) O. Winkelmann, D. Linder, J. Lacour, C. N a¨ ther, U. L u¨ ning,
9
(
Acknowledgements
Eur. J. Org. Chem. (2007) 3687.
[
[
[
14] I.J.B. Lin, C.S. Vasam, Coord. Chem. Rev. 251 (2007) 642, and
references therein.
We thank Prof. Dr. Frank S o¨ nnichsen (NMR spectros-
copy) and Markus Luft (synthesis).
15] J. Ramirez, R. Corber a´ n, M. Sana u´ , E. Peris, E. Fernandez, Chem.
Commun. (2005) 3056.
16] M.M. Diaz-Requejo, P.J. P e´ rez, J. Organomet. Chem. 690 (2005)
5441.
Appendix A. Supplementary material
[
[
17] B.M. Wile, M. Stradiotto, Chem. Commun. (2006) 4104.
18] A.C. Sentman, S. Csihony, R.M. Waymouth, J.L. Hedrick, J. Org.
Chem. 70 (2005) 2391.
CCDC 664014, 664015 and 664016 contain the supple-
mentary crystallographic data for 2, 3 and 4. These data
can be obtained free of charge via http://www.ccdc.cam.
ac.uk/conts/retrieving.html, or from the Cambridge Crys-
tallographic Data Centre, 12 Union Road, Cambridge
CB2 1EZ, UK; fax: (+44) 1223-336-033; or e-mail: deposit@
ccdc.cam.ac.uk.
[
[
19] (a) H.M.J. Wang, I.J.B. Lin, Organometallics 17 (1998) 972;
(
b) J.C. Garrison, R.S. Simons, J.M. Talley, C. Wesdemiotis, C.A.
Tessier, W.J. Youngs, Organometallics 20 (2001) 1276;
(c) X. Hu, I. Castro-Rodriguez, K. Meyer, Organometallics 23 (2004)
7
55.
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Organometallics 12 (1993) 3405;
(
b) L.G. Bonnet, R.E. Douthwaite, R. Hodgson, Organometallics 22
(2003) 4384;
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