Synthesis of N,N′-bis(thioether)-functionalized imidazolium salts: Their reactivity towards Ag and Pd complexes and first S,CNHC,S free carbene

Article abstract of DOI:10.1039/c0dt00351d

The synthesis of bis(thioether)-functionalized imidazolium salts, the characterisation of the first S,C_NHC,S free carbene ligand and the corresponding Ag(i) and Pd(ii) functional carbene complexes are reported. The latter have been prepared from the isolated Ag(i) carbene complexes using the transmetallation procedure or by reaction of the imidazolium salts with [PdCl₂(COD)], followed by deprotonation of the intermediate in which both thioether functions are coordinated to Pd(ii).

Full text of DOI:10.1039/c0dt00351d

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Synthesis of N,N’-bis(thioether)-functionalized imidazolium salts: their
reactivity towards Ag and Pd complexes and first S,CNHC,S free carbene†
Christophe Fliedel, Alessandra Sabbatini and Pierre Braunstein*
Received 21st April 2010, Accepted 18th June 2010
DOI: 10.1039/c0dt00351d
The synthesis of bis(thioether)-functionalized imidazolium salts, the characterisation of the first
S,CNHC,S free carbene ligand and the corresponding Ag(I) and Pd(II) functional carbene complexes are
reported. The latter have been prepared from the isolated Ag(I) carbene complexes using the
transmetallation procedure or by reaction of the imidazolium salts with [PdCl2(COD)], followed by
deprotonation of the intermediate in which both thioether functions are coordinated to Pd(II).
introduction of identical or different thioether groups. The silver
NHC complexes prepared from the corresponding imidazolium
salts have been fully characterised and, in one case, used for the
synthesis by transmetallation of a S,CNHC,S Pd(II) pincer complex.
Introduction
N-Heterocyclic carbenes (NHCs) are known to be strong donors
and robust ligands1 and therefore have been extensively studied in
organometallic chemistry and homogenous catalysis.2 They have
An alternative pathway to S,CNHC,S complexes was used, which
been used as phosphine mimics and their palladium complexes
involved first, coordination of the thioether functions to Pd(II),
have been successfully used in many cross-coupling reactions.3 The
possibility of attaching donor groups to the nitrogen atoms opens
followed by deprotonation of the imidazolium group. The first
examples of cationic, imidazolium-containing bis(thioether) S,S-
new possibilities for creating heterofunctional donor ligands.
PdCl2 complexes were thus isolated and characterized. Neutral
Different combinations have emerged, which have allowed the
formation of N–,4 O–,5 and P–CNHC complexes. Owing to their
bis(thioether) complexes have recently been studied for allylic
oxidation and displayed better performances than previous
systems.10
6
hemilabile character,7 these compounds rapidly attracted attention
for applications in homogeneous catalysis. Few examples of
S–CNHC metal complexes have been recently described and the
presence of the S-containing function appears beneficial in cat-
alytic reactions (Scheme 1). These complexes have been obtained
by conventional methods8,16 or by oxidative-addition of a C–S
bond across a zero valent metal centre,9 and generally showed in
solution fast exchange on the 1H NMR time-scale, consistent with
the lability of the coordinated thioether.
Results and Discussion
Synthesis of the Ligands
The N-functionalized imidazoles A and B were obtained by a reac-
tion between imidazole and commercially available 2-chloroethyl
ethylsulfide or 2-chloroethyl methylsulfide, respectively, in the pres-
ence of sodium tert-butoxide in refluxing toluene (Scheme 2). The
NMR spectra show typical resonances for aliphatic-substituted
imidazoles at 7.56 and 7.41 ppm for the 2-H protons, respectively,
and at 137.1 ppm for the NCN carbon of both A and B. The
Scheme 1 Examples of S,CNHC and S,CNHC,S precursors.
Here we report the stepwise synthesis of new NHC precur-
sors bearing a thioether function on each nitrogen atom of
the imidazolium salt. The methodology used allows for the
Laboratoire de Chimie de Coordination, Institut de Chimie (UMR 7177
CNRS), Universite´ de Strasbourg, 4 rue Blaise Pascal, F-67081, Strasbourg
Cedex, France. E-mail: braunstein@unistra.fr; Fax: +33 368 851 322;
Tel: +33 368 851 308.
† CCDC reference number 781531. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/c0dt00351d
Scheme 2 Ligand synthesis. (a) 1.2 equiv. KOt-Bu, toluene, reflux,
overnight; (b) neat, 150 ◦C, 2 h; (c) 1 equiv. KHMDS, THF, room
temperature, 2 h; (d) 1 equiv. S8, THF, room temperature, 2 h.
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analogous products obtained from 2-chloroethyl phenylsulfide
could be observed by NMR spectroscopy but were not isolated
in pure form.
carbenes 2 and 3 were prepared similarly from 2·HCl and 3·HCl,
respectively.
Synthesis of the Silver(I) Complexes
An atom efficient reaction applied to A and B afforded
homo- and hetero-bis(thioether) imidazolium salts, respectively
(Scheme 2). The C2-symmetric cation in 1·HCl was obtained
in nearly quantitative yield by neat reaction between A and 2-
chloroethyl ethylsulfide, following a method described for the
synthesis of mono(thioether) imidazoliums.8e,16 When the same
procedure was applied to the reaction of B with 2-chloroethyl
ethylsulfide or 2-chloroethyl phenylsulfide, it afforded the unsym-
metrical derivatives 2·HCl and 3·HCl, respectively (Scheme 2). To
the best of our knowledge, the latter are the only reported examples
of hetero-bis(thioether) imidazolium salts, while C2-symmetric
homo-bis(thioether) imidazolium salts were published during the
course of our work.8b The 1H NMR spectra of 1·HCl–3·HCl
show typical resonances between 10.40 and 10.68 ppm for the 2-H
Reaction of the imidazolium salts with excess Ag2O at room
temperature in dichloromethane afforded, after filtration through
Celite to remove unreacted Ag2O, the corresponding silver (I)
NHC complexes 1·AgCl–3·AgCl in good yields (Scheme 3a).
Formation of the latter was established by the absence of the 2H-
1
imidazolium proton resonance in the H NMR spectrum, which
also showed a significant upfield shift of the 4,5H-imidazolium
1
protons. The 13C{ H} NMR spectra showed typical downfield
shifts, compared to the corresponding imidazolium salts, of the
C2-carbon signals between 179.8 and 179.9 ppm, characteristic of
the formation of Ag(I) NHC complexes.
1
proton and the 13C{ H} NMR peak of their NCN carbon is found
between 137.7 and 138.2 ppm. The 1H NMR spectrum of 1·HCl
contains only one signal for the equivalent 4,5-H imidazolium
protons, consistent with a C2-symmetry of the ligand, while two
4
pseudo-triplets are observed for 2·HCl and 3·HCl (3J ª J ª 1.5–
1.8 Hz). The most intense peaks in the ESI mass spectra
correspond to [M–Cl]+.
The free carbene 1 was readily generated in quantitative yield
by deprotonation of 1·HCl with potassium hexamethyldisilazane
(KHMDS) in THF at room temperature. It was characterized by
multinuclear NMR spectroscopy, but degraded slowly in solution
after several hours.
1
The H NMR spectrum of 1 confirms the absence of the 2H-
imidazolium proton and shows a significant upfield shift of the
4,5-H imidazolium protons from 7.58 (in CDCl3) to 6.96 ppm
(in THF-d8). A strong downfield shift was observed for the
1
broad and weak 13C{ H} NMR signal of the NCN carbon at
195.9 ppm. For comparison, the carbene carbon of free N,N’-
(dimethyl)imidazol-2-ylidene resonates at 215.2 ppm.11 This could
be consistent with the significant influence of N-substitution on
the electronic properties of the carbene centre12 and/or with
the formation in solution of a potassium adduct favored by the
presence of stabilizing donor functions on the imidazole ring.
Unfortunately, all attempts to crystallize 1 were unsuccessful
owing to its low stability and since no similar ligand is available for
comparison, we could not confirm the latter hypothesis. Ligand
1 is the first characterized bis(thioether)-functionalized carbene
and despite the recent report of bis(thioether) imidazolium
salts, the authors did not characterize the corresponding free
carbenes.8b
Scheme 3 Synthesis of the Ag(I) complexes and the S,S and S,CNHC,S
Pd(II) complexes. (a) 1 equiv. Ag2O, CH2Cl2, room temperature, 2 h; (b)
1 equiv. [PdCl2(COD)], CH2Cl2, room temperature, 4 h; (c) 1.1 equiv.
Cs2CO3, 5 equiv. KPF6, MeCN, reflux, 6 h; (d) 1 equiv. [PdCl2(COD)],
5 equiv. KPF6, CH2Cl2, room temperature, 4 h.
Synthesis of the Palladium(II) Complexes
The coordination chemistry of bis(thioether) NHC-type ligands
was then investigated using Pd(II). The in situ reaction of carbene
1 with [PdCl2(COD)] (COD = 1,5-cyclooctadiene) afforded a
mixture of complexes (NMR evidence). Different routes were thus
investigated to obtain the desired complexes in pure form. The
carbene complex 1·AgCl was reacted in situ with [PdCl2(COD)]
and excess KPF6 to form the Pd(II) carbene complex 7 by
transmetallation (Scheme 3a and d).13
An alternative, stepwise synthesis consisted first of the for-
mation of the non-NHC, cationic complexes 4–6 by reaction
of [PdCl2(COD)] with 1·HCl–3·HCl, respectively (Scheme 3b).
Their 1H NMR spectra confirmed the presence of the 2-H proton,
between 9.23 and 9.26 ppm. For complex 4, this spectrum also
revealed the equivalence of the two side chains because the 4,5H-
imidazolium protons gave rise to only one doublet (4J = 1.5 Hz)
owing to coupling with 2-H. The presence of a cis-PdCl2 unit is
Since 1 was not stable enough to be structurally character-
ized, we attempted to isolate its thione derivative 1·S. Stepwise
formation of 1·S involved first the deprotonation of 1·HCl by
one equivalent KHMDS in THF at room temperature, followed
by the addition of one equivalent S8 to the reaction mixture.
After filtration, 1·S was obtained in good yield and was fully
characterized. As in the case of 1, disappearance of the 2H-
1
imidazolium 1H NMR signal was noted. A typical 13C{ H}
NMR signal at 161.8 ppm is assigned to the NCN carbon. In
contrast to the free carbene 1, its thione derivative 1·S is air-
stable in solution and in the solid state, but unfortunately, no
crystal suitable for X-ray diffraction could be obtained. The free
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proposed on the basis of the values of the n(Pd–Cl) stretching
vibrations (e.g. obtained for 4: 304 and 289 cm-1) in the far
infrared spectrum.14 These complexes are very stable and easy
to handle, which offers a significant advantage over the silver
derivatives used for the preparation of the pincer complexes 7–
9 (Scheme 3). The coordination of both sulfur atoms provides
a spatial pre-organisation, favoring the formation of the pincer
complex. Reaction of 4 with a weak base, such as Cs2CO3, in
the presence of excess KPF6 in refluxing acetonitrile afforded the
desired complex [PdCl(S,CNHC,S)]PF6 (7). The pincer complexes
8 and 9 were prepared following the same method (Scheme 3b
and c).
The pincer structure of complexes 7–9 was confirmed using
their 1H NMR spectra, which contain broad signals at room
temperature for the aliphatic protons of the side chains, which
all become chemically and/or magnetically inequivalent owing to
the presence of stereogenic sulfur centres, after formation of the
S,CNHC,S pincer. The pincer bonding mode is also consistent with
the broad signal for the 4,5H-imidazolium protons, which reveals
a symmetrical structure, maintaining the equivalence of these
two protons. Two other structural arrangements corresponding
to the same formula could be envisaged for these products.
The first one is a chloride bridged-dinuclear structure, in which
only one thioether function from each ligand is coordinated to
palladium, while the other remains dangling (Scheme 4a). Another
conceivable non-pincer structure would be that of a dinuclear
complex, in which the ligand acts as a S,CNHC bridge between two
PdCl moieties, chelation of the other thioether would complete
the Pd(II) coordination sphere (Scheme 4b). In both cases, two
chemically inequivalent thioether arms would result but none of
these structures are supported by our spectroscopic data.
Scheme 5 Synthesis of the dinuclear trans-[PdBr2(m-S,CNHC)]2 complex
reported by Labande et al.8g
Variable Temperature 1H NMR Studies
Variable temperature 1H NMR studies were performed to identify
the different isomers in solution and to confirm that no dinuclear
structures are present in our case. Upon cooling a solution of
complex 7 from 298 K to 223 K, a splitting of the signals was
observed. The broad singlet observed at room temperature for
the 4,5H-imidazolium protons was progressively split into two
well separated and sharp singlets at 223 K (Fig. 1), confirming
that the pincer form is retained in solution. The signals of all the
CH2 protons also sharpen at this temperature. The presence of a
chloride-bridged or CNHC,S-bridged dinuclear species (Scheme 4)
was ruled out since this should give rise to two doublets for
the non-equivalent 4- and 5H-imidazolium protons. We are
therefore confident that the only isomers present in solution are
mononuclear structures in equilibrium through in-place inversion
of the stereogenic sulfur atoms, giving rise to two singlets for the
two equivalent 4,5H-imidazolium protons (Scheme 6).15
1
Scheme
4 Hypothetical (a) chloride-bridged dinuclear and (b)
Fig. 1 Variable temperature H NMR spectra in the 4,5H-imidazolium
S,CNHC-bridged dinuclear structures for 7, ruled out by VT NMR studies
protons region of complex 7.
(see text).
For comparison, we also prepared the mono-thioether palla-
dium dichloride complex 11 (Scheme 7) to compare its catalytic
properties in Suzuki–Miyaura cross-coupling reactions with those
of the bis(thioether) complex 7 (see below). We applied the
transmetallation procedure, using the N-(2,4,6-trimethylphenyl)-
A similar approach to that described in Scheme 3c has been
used in only three other cases, to the best of our knowledge.
Mono(thioether) imidazolium salts have been first S-coordinated
to a Pd(II) centre before deprotonation, resulting in the formation
of a dinuclear complex where two PdBr2 centres were bridged
by two S,CNHC ligands in a trans, head-to-tail arrangement
(Scheme 5).8g However, when this approach was applied to
Ni(II)/phosphine-functionalized imidazolium systems, formation
of cis-P,CNHC Ni(II) chelate complexes was suggested.6f Although
not isolated, a phosphine imidazolium Ru(II) complex was sug-
gested to be an intermediate in the synthesis of a cis-P,“abnormal
carbene” complex.6a
N’-ethyl-ethyl-sulfide imidazolium iodide recently described,16
1
equiv. Ag2O in dichloromethane and 1 equiv. of [PdCl2(COD)]
(Scheme 7). This reaction afforded the S,CNHC complex 11 in good
1
yield. Its chelate structure was suggested by the broad H NMR
signals for the aliphatic protons of the thioether function, as always
reported after formation upon coordination of stereogenic sulfur
centres.8 The far-infrared spectrum of this complex contained
absorptions for the n(Pd–Cl) stretching modes at 319 and 300 cm-1,
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and not 90◦, which would be the most electronically/sterically
preferred orientation.
This cis-S,CNHC chelate structure observed in all metal
complexes involving thioether- or thiophene-functionalized
NHCs8a–f,8h–l,9 contrasts with the dinuclear structure of the trans-
dibromo palladium complex obtained by Labande et al.8g from N-
(2,4,6-trimethylphenyl)-N’-ethyl-ethyl-sulfide imidazolium bro-
mide (Scheme 5). In view of the structure of complex 11·CH2Cl2,
which contains the same ligand, we can conclude that S,CNHC
chelation or m-S,CNHC bridge formation, i.e. a cis or trans
arrangement of the donor groups, is not controlled here by the
steric properties on the N- or S-substituents, the only differences
between the reactions of Schemes 6 and 7 being the nature of the
halides and the reaction/crystallization conditions. We obtained
11 via the transmetallation reaction, whereas the dinuclear com-
plex of Scheme 5 was formed by deprotonation of the imidazolium
salt.8g
Scheme 6 Proposed equilibria for complex 7 in solution with in-place S
inversion.
Evaluation of the NHC Complexes in Suzuki–Miyaura
Cross-Coupling Reaction
Preliminary catalytic studies were performed in Suzuki–Miyaura
cross-coupling reactions of 4-bromotoluene with phenyl boronic
acid to evaluate the potential of complex 7. We compared the
conversions to 4-methylbiphenyl obtained with complexes 7,
11 and 12 (prepared in situ)17 under the same conditions (see
experimental section) to identify a potential beneficial effect of
one and/or two thioether functions. The results are reported in
Scheme 8. An increase in activity was observed upon introduction
of one thioether function from 64% (12) to 77% (11), but no
significant improvement was noticed upon introduction of a
second thioether function, 83% (7). The conversions are limited
by the life-time of the catalyst, as shown by addition of fresh
substrates after the reaction was performed for 2 h which did not
lead to further conversion.
Scheme 7 Synthesis of complex 11.
typical for a cis-PdCl2 unit.14 The chelate arrangement could
finally be unambiguously confirmed from the solid state structure
of 11·CH2Cl2 determined by single crystal X-ray diffraction
analysis (Fig. 2). The structure reveals a distorted square planar
coordination geometry around the palladium centre, in which the
sulfur and the carbene ligands are in a mutual cis arrangement. The
stronger trans influence of the carbene donor explains the longer
˚
Pd1–Cl1 [2.3645(10) A] bond compared to Pd1–Cl2 [2.3066(10)
˚
A]. The angle between the imidazole ring (C1–N1–C4–C5–N2)
and the coordination mean plane (C1–Pd1–S1–Cl1–Cl2) is 49.04◦
Scheme 8 NHC–Pd(II) complexes were compared in Suzuki–Miyaura
cross-coupling reactions and the corresponding conversions were observed
under the conditions detailed in the experimental section.
Conclusions
We have reported an efficient stepwise synthesis of bis(thioether)
functionalized imidazolium salts, with the first examples of hetero-
bis(thioether) carbene precursors. We also reported a unique
S,CNHC,S free carbene and chelated [PdCl2(S,S)] complexes con-
taining an imidazolium group well positioned to readily afford
S,CNHC,S pincer carbene complexes upon deprotonation.
These studies have shown that thioether functions are strong
enough donors to displace the COD ligand from the palla-
dium precursor for the preparation of 4–6 and exert favorable
Fig. 2 View of the molecular structure of 11·CH2Cl2. Hydrogen atoms
and solvent molecule have been omitted for clarity. Ellipsoids represented
◦
˚
at 50% probability level. Selected bond lengths (A) and angles ( ): Pd1–C1
1.976(4); Pd1–S1 2.2823(11); Pd1–Cl2 2.3066(10); Pd1–Cl1 2.3645(10);
C1–Pd1–S1 90.39(11); C1–Pd1–Cl2 89.48(11); N1–C1–N2 106.2(3).
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anchimeric assistance for the formation of the pincer complexes
7–9, even in the presence of MeCN.
for C7H12N2S (156.25): C, 53.81; H, 7.74; N, 17.93. Found: C,
53.69; H, 7.486; N, 17.34. FTIR: nmax(oil) cm-1: 3106br, 3033br,
2965br, 2925br, 2869br, 2690br, 2606br, 2361w, 2343w, 2324w,
1675w, 1650w, 1589w, 1505 s, 1447 m, 1393w, 1375w, 1357w,
1324w, 1287 m, 1263 m, 1228 s, 1155w, 1107 m, 1077 s, 1063 m,
1033 m, 971w, 926sh, 906 m, 871w, 817 m, 739 s, 698 m, 663vs. 1H
NMR (CDCl3, 300 MHz) d: 1.23 (3H, t, 3J = 7.5 Hz, SCH2CH3),
The synthesis and variable temperature studies performed on
complex 7 allow us to conclude that no decoordination of the
sulfur atom occurs in solution and that the broad signals observed
are due only to in-place inversion of the sulfur centres, giving rise to
different stereoisomers in solution. The structural characterization
of the cis, mononuclear complex 11 provides an interesting
contrast with the trans, dinuclear structure reported previously
for a dibromo complex bearing the same S,CNHC ligand.8g
We plan to use the new pincer complexes 7–9 described here in
other catalytic reactions to examine further the influence of two
thioether functions on the imidazolium ring.
3
3
2.44 (2H, q, J = 7.5 Hz, SCH2CH3), 2.86 (2H, t, J = 7.2 Hz,
NCH2CH2S), 4.14 (2H, t, 3J = 7.2 Hz, NCH2CH2), 6.97 (1H, br s,
CH CH), 7.08 (1H, br s, CH CH), 7.56 (1H, br s, NCHN).
1
13C{ H} NMR (CDCl3, 75.5 MHz) d: 14.72 (SCH2CH3), 26.34
(SCH2CH3), 32.84 (NCH2CH2S), 47.26 (NCH2CH2S), 118.86
(HCNCH2), 129.58 (C NCH), 137.14 (NCN). MS (ESI): m/z
157.1 [M+H]+.
B, R = methyl. The same procedure was used with imidazole
(3.08 g, 45.21 mmol), sodium tert-butoxide (6.59 g, 58.77 mmol)
and 2-chloroethyl methylsulfide (4.50 ml, 5.00 g, 45.21 mmol).
Yield: 36%. Anal. Calc. for C6H10N2S (142.22): C, 50.67; H,
7.09; N, 19.70. Found: C, 50.02; H, 7.274; N, 19.51. FTIR:
Experimental Section
General procedures.
All operations were carried out using standard Schlenk techniques
under inert atmosphere. Solvents were purified and dried under
nitrogen by conventional methods. d6-DMSO was degassed and
n
max(oil) cm-1: 3108br, 2916br, 2835br, 2361w, 2343w, 1650w,
1506 s, 1441 m, 1357w, 1324w, 1288 m, 1228 s, 1158w, 1107
m, 1078 s, 1064 m, 1033w, 961w, 915 m, 907 m, 819 m, 741 s,
683 m, 662vs. 1H NMR (CDCl3, 300 MHz) d: 1.88 (3H, s, SCH3),
˚
stored over 4 A molecular sieves. CDCl3 and CD3CN were dried
˚
over 4 A molecular sieves, degassed by freeze-pump-thaw cycles
3
3
2.69 (2H, t, J = 6.6 Hz, NCH2CH2S), 4.01 (2H, t, J = 6.9 Hz,
NCH2CH2), 6.85 (1H, br s, CH CH), 6.92 (1H, br s, CH CH),
and stored under argon. NMR spectra were recorded at room tem-
perature on a Bruker AVANCE 300 spectrometer (1H, 300 MHz;
7.41 (1H, br s, NCHN). 13C{ H} NMR (CDCl3, 75.5 MHz) d:
1
1
1
13C{ H}, 75.47 MHz; and31P{ H} 121.49 MHz) and referenced
using the residual proton solvent (1H) or solvent (13C) resonance
15.66 (SCH3), 35.24 (NCH2CH2S), 46.75 (NCH2CH2S), 118.91
(HCNCH2), 129.39 (C NCH), 137.12 (NCN). MS (ESI): m/z
143.1 [M+H]+.
1
or 85% H3PO4 for 31P{ H}. Chemical shifts are given in ppm.
Assignments are based on 1H, 1H–COSY, 1H, 13C–HMQC and 1H,
13C–HMBC experiments. IR spectra were recorded in the region
4000–100 cm-1 on a Nicolet 6700 FT-IR spectrometer (ATR mode,
SMART ORBIT accessory, diamond crystal). Elemental analyses
were performed by the “Service de microanalyses”, Universite´
de Strasbourg and by the “Service Central d’Analyse”, USR-
59/CNRS, Solaize. Electrospray mass spectra (ESI-MS) were
recorded on a microTOF (Bruker Daltonics, Bremen, Germany)
instrument using nitrogen as a drying agent and nebulising
gas and Maldi-TOF analyses were carried out on a Bruker
AutiflexII TOF/TOF (Bruker Daltonics, Bremen, Germany),
using dithranol (1.8.9 trihydroxyanthracene) as a matrix. Gas
chromatographic analyses were performed on a Thermoquest
GC8000 Top series gas chromatograph using a HP Pona column
(50 m, 0.2 mm diameter, 0.5 mm film thickness). The complex
[PdCl2(COD)]18 was prepared according to the literature. All other
reagents were used as received from commercial suppliers.
Synthesis of N-ethyl-(R)-sulfide-N’-ethyl-(R’)-sulfide imidazolium
chloride:
These compounds are known to be very hygroscopic and the ele-
mental analyses performed always afforded carbon and nitrogen
percentages lower than the calculated values.
1·HCl: R = R’ = ethyl [N,N’-bis(ethyl-ethyl-sulfide) imidazolium
chloride]. A (1.10 g, 7.04 mmol) was placed in a Schlenk
tube equipped with a magnetic stirrer and then 2-chloroethyl
ethylsulfide (0.820 ml, 0.877 g, 7.04 mmol) was added. The mixture
◦
was heated for 2 h at 120 C and then allowed to cool to room
temperature. The pale yellow oil obtained was washed with dry
THF (2 ¥ 40 ml) and dried in vacuo. Yield: 93%. Anal. Calc. for
C11H21ClN2S2 (280.88): C, 47.04; H, 7.54; N, 9.97. Found: C, 45.34;
H, 6.970; N, 8.161. FTIR: nmax(oil) cm-1: 3364br, 3130sh, 3043br,
2962 s, 2925 s, 2868 m, 1561 s, 1448 s, 1415 m, 1375w, 1354w,
1332w, 1264 m, 1155vs, 1105w, 1062w, 1026w, 971w, 835 m, 757 s,
Synthesis of N-ethyl-(R)-sulfide imidazole
1
3
690m. H NMR (CDCl3, 300 MHz) d: 1.21 (6H, t, J = 7.4 Hz,
3
3
A, R = ethyl. Pure imidazole (5.00 g, 73.44 mmol), sodium tert-
butoxide (10.59 g, 96.10 mmol) and toluene (100 ml) were placed
in a Schlenk tube equipped with a magnetic stirrer. After 2-
chloroethyl ethylsulfide (8.55 ml, 9.15 g, 73.44 mmol) was added
to the suspension, the mixture was refluxed for 12 h. During
heating, the colourless mixture turned light brown. After cooling,
the mixture was filtered and the precipitate washed with dry
toluene (2 ¥ 20 ml). The volatiles were evaporated under reduced
pressure and the brown oil was washed with dry diethyl ether
(2 ¥ 40 ml) and dried in vacuo. The product was purified by
column chromatography (100% EtOAc). Yield: 25%. Anal. Calc.
SCH2CH3), 2.58 (4H, q, J = 7.4 Hz, SCH2CH3), 3.04 (4H, t, J
3
= 6.3 Hz, NCH2CH2S), 4.57 (4H, t, J = 6.4 Hz, NCH2CH2),
7.58 (2H, d, 4J = 1.6 Hz, CH=CH), 10.68 (1H, s, NCHN).
13C{ H} NMR (CDCl3, 75.5 MHz) d: 14.71 (SCH2CH3), 26.14
1
(SCH2CH3), 31.92 (NCH2CH2S), 49.36 (NCH2CH2S), 122.24,
(CH CH), 138.27 (NCN). MS (ESI): m/z 245.1 [M–Cl]+.
2·HCl: R = methyl; R’ = ethyl. The same procedure was used with
B (0.810 g, 5.70 mmol) and 2-chloroethyl ethylsulfide (0.663 ml,
0.710 g, 5.70 mmol). Yield: 95%. Anal. Calc. for C10H19ClN2S2
(266.85): C, 45.01; H, 7.18; N, 10.50. Found: C, 43.42; H, 6.685;
N, 8.868. FTIR: nmax(oil)/cm-1: 3375br, 3132w, 3052br, 2962 m,
8824 | Dalton Trans., 2010, 39, 8820–8828
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2918 m, 2868w, 2720br, 1630w, 1561 m, 1449 m, 1375w, 1355w,
1331w, 1261 m, 1215sh, 1154vs, 1086vs, 1062 s, 1028 s, 970sh,
862m, 797s, 760m, 729s, 697m. 1H NMR (CDCl3, 300 MHz)
d: 1.21 (3H, t, 3J = 7.2 Hz, SCH2CH3), 2.05 (3H, s, NCH3),
assigned to the C S stretching vibration), 1153 s, 1107w, 1061w,
1
971w, 869w, 752s. H NMR (CDCl3, 300 MHz) d: 1.24 (6H, t,
3
3J = 7.4 Hz, SCH2CH3), 2.54 (4H, q, J = 7.4, Hz, SCH2CH3),
3
3
2.90 (4H, t, J = 7.1 Hz, NCH2CH2), 4.19 (4H, t, J = 6.7 Hz,
3
3
1
2.47 (2H, q, J = 7.5 Hz, SCH2CH3), 2.94 (4H, t, J = 6.6 Hz,
NCH2CH2S), 4.48 (4H, m, NCH2CH2), 7.66 (1H, pseudo t, 3J =
NCH2CH2), 6.74 (2H, s, CH=CH). 13C{ H} NMR (CDCl3, 75.5
MHz) d: 14.82 (SCH2CH3), 26.19 (SCH2CH3), 29.94 (NCH2CH2),
47.23 (NCH2CH2), 117.26 (CH CH), 161.75 (NCN). MS (ESI):
m/z 277.1 [M+H]+.
3
4
4J = 1.5 Hz, CH CH), 7.72 (1H, pseudo t, J = J = 1.5 Hz,
1
CH CH), 10.40 (1H, br s, NCHN). 13C{ H} NMR (CDCl3,
75.5 MHz) d: 14.68 (SCH2CH3), 15.46 (SCH3), 25.97 (SCH2CH3),
31.77 (NCH2CH2SEt), 34.22 (NCH2CH2SMe), 48.51 and 49.18 (2
NCH2CH2S), 122.50 and 122.55 (CH CH), 137.72 (NCN). MS
(ESI): m/z 231.1 [M-Cl]+.
Synthesis of the silver(I) carbene complexes:
1·AgCl: R = R’ = ethyl.
3·HCl: R = methyl; R’ = phenyl. The same procedure was
used with B (0.760 g, 5.34 mmol) and 2-chloroethyl phenylsulfide
(0.789 ml, 0.923 g, 5.34 mmol). Yield: 88%. Anal. Calc. for
C14H19ClN2S2 (314.90): C, 53.40; H, 6.08; N, 8.90. Found: C, 53.11;
H, 6.243; N, 8.241. FTIR: nmax(oil)/cm-1: 3370br, 3132sh, 3051br,
2980br, 2916 m, 2832w, 2722br, 2603br, 1629w, 1561 s, 1508w,
1480 m, 1438 s, 1354w, 1331w, 1289w, 1274w, 1229w, 1155 s,
The imidazolium 1·HCl (0.100 g, 0.356 mmol) was dissolved in
dry CH2Cl2 and solid Ag2O (0.083 g, 0.356 mmol) was added under
nitrogen. The reaction mixture was stirred overnight in the dark
at room temperature. Then the suspension was filtered through a
Celite pad and the solvent was evaporated under reduced pressure
to give a light sensitive white solid. Yield: 0.116 g, 84%. Anal.
Calc. for C11H20AgClN2S2 (387.74): C, 34.07; H, 5.20; N, 7.22.
Found: C, 34.19; H, 5.013; N, 6.904. 1H NMR (CDCl3, 300 MHz)
d: 1.23 (6H, t, 3J = 7.4 Hz, SCH2CH3), 2.52 (4H, q, 3J = 7.4 Hz,
1
1106sh, 1087 m, 1024 m, 963w, 865w, 744vs, 693vs. H NMR
(CDCl3, 300 MHz) d: 2.14 (3H, s, NCH3), 2.96 (2H, t, 3J = 6.6 Hz,
NCH2CH2S), 3.49 (2H, t, 3J = 6.3 Hz, NCH2CH2S), 4.52 (4H, m,
SCH2CH3), 2.91 (4H, t, J = 6.5 Hz, NCH2CH2S), 4.28 (4H, t,
3
3
1
NCH2CH2), 7.19–7.36 (5H, m, H arom), 7.48 (1H, pseudo t, J
3J = 6.6 Hz, NCH2CH2S), 7.08 (2H, s, CH CH). 13C{ H} NMR
4
3
4
= J = 1.8 Hz, CH CH), 7.59 (1H, pseudo t, J = J = 1.8 Hz,
(CDCl3, 75.5 MHz) d: 14.70 (SCH2CH3), 26.49 (SCH2CH3), 33.16
(NCH2CH2S), 51.68 (NCH2CH2S), 121.46 (CH CH), 179.80
(NCN). MS (ESI): m/z 353.0 [M-Cl]+.
CH CH), 10.50 (1H, br s, NCHN). 13C{ H} NMR (CDCl3, 75.5
1
MHz) d: 15.55 (SCH3), 34.25 and 34.37 (2 NCH2CH2S), 48.67
and 49.17 (2 NCH2CH2S), 122.26 and 122.64 (CH CH), 127.38
(Cpara), 129.48 (Cmeta), 130.40 (Cortho), 133.30 (Cipso), 137.94 (NCN).
MS (ESI): m/z 279.1 [M-Cl]+.
2·AgCl: R = methyl; R’ = ethyl.
The same procedure was used with 2·HCl (0.042 g, 0.157 mmol)
and Ag2O (0.036 g, 0.157 mmol). Yield: 88%. Anal. Calc. for
C10H18AgClN2S2 (373.71): C, 32.14; H, 4.85; N, 7.50. Found: C,
1
31.88; H, 4.799; N, 7.316. H NMR (CDCl3, 300 MHz) d: 1.21
Synthesis of N,N’-bis(ethyl-ethyl-sulfide)imidazol-2-ylidene: 1
(3H, t, 3J = 7.5 Hz, CH2CH3), 2.08 (3H, s, SCH3), 2.50 (2H, q,3J
= 7.5 Hz, SCH2CH3), 2.89 (4H, m, 2 NCH2CH2S), 4.28 (4H, m,
In the glovebox, solid potassium bis(trimethylsilyl)amide
(KHMDS) (0.071 g, 0.36 mmol) was added to a suspension of
1·HCl (0.100 g, 0.36 mmol) in dry d8-THF at room temperature.
The suspension was stirred at room temperature for 2 h, until
1·HCl was totally dissolved, and then filtered through a Celite pad.
The remaining light orange solution was analysed by multinuclear
1
2 NCH2CH2), 7.09 (2H, s, 2 CH CH). 13C{ H} NMR (CDCl3,
75.5 MHz) d: 14.74 (CH2CH3), 16.01 (SCH3), 26.52 (CH2CH3),
33.18 (SCH2CH2), 35.72 (SCH2CH2), 51.14 (NCH2CH2SEt),
51.69 (NCH2CH2SMe), 121.47 and 121.58 (CH CH), 179.90
(NCN). MS (ESI): m/z 339.0 [M-Cl]+.
1
NMR spectroscopy. H NMR (d8-THF, 300 MHz) d: 1.24 (6H,
3·AgCl: R = methyl; R’ = phenyl.
t, 3J = 7.5 Hz, SCH2CH3), 2.54 (4H, q, 3J = 7.5, Hz, SCH2CH3),
The same procedure was used with 3·HCl (0.036 g, 0.114 mmol)
and Ag2O (0.027 g, 0.114 mmol). Yield: 79%. Anal. Calc. for
C14H18AgClN2S2 (421.76): C, 39.87; H, 4.30; N, 6.64. Found: C,
3
3
2.91 (4H, t, J = 7.5 Hz, NCH2CH2), 4.13 (4H, t, J = 7.5 Hz,
NCH2CH2), 6.96 (2H, s, CH CH). 13C{ H} NMR (d8-THF, 75.5
1
1
MHz) d: 14.31 (SCH2CH3), 25.45 (SCH2CH3), 32.76 (NCH2CH2),
50.87 (NCH2CH2), 118.62 (CH CH), 195.87 (NCN).
40.11; H, 4.306; N, 6.891. H NMR (CDCl3, 300 MHz) d: 2.09
(3H, s, SCH3), 2.84 (2H, t,3J = 6.6 Hz, NCH2CH2S), 3.32 (2H,
t,3J = 6.6 Hz, NCH2CH2S), 4.27 (4H, m, 2 NCH2CH2), 7.01 and
7.02 (2H, AB spin system,3J = 1.8 Hz, CH CH), 7.32 (5H, m,
Synthesis of N,N’-bis(ethyl-ethyl-sulfide)imidazol-2-thione: 1·S
1
H arom). 13C{ H} NMR (CDCl3, 75.5 MHz) d: 16.01 (SCH3),
1·HCl (0.100 g, 0.36 mmol) and sulfur (0.091 g, 0.36 mmol)
were placed in a Schlenk tube and dry THF was added. The
suspension was stirred at room temperature and then solid potas-
sium bis(trimethylsilyl)amide (KHMDS) (0.071 g, 0.36 mmol)
was added under nitrogen. The reaction mixture was stirred for
2 h and then filtered through a Celite pad. The volatiles were
removed under reduced pressure and the residue washed with
pentane (2 ¥25ml). 1·S was obtained as an orange solid. Yield:
78%. Anal. Calc. for C11H20N2S3 (276.48): C, 47.78; H, 7.29; N,
10.13. Found: C, 47.57; H, 7.201; N, 10.24. FTIR: nmax(solid) cm-1
3372 s, 3139 m, 2967 m, 2927 m, 2870w, 1630 m, 1562 s, 1451
m, 1415w, 1375w, 1354w, 1333w, 1264 m, 1176 m (tentatively
35.41 (NCH2CH2S), 35.66 (NCH2CH2S), 51.17 (2 NCH2CH2),
121.30 and 121.77 (CH CH), 127.09 (Cpara), 129.45 (Cmeta), 129.96
(Cortho), 137.24 (Cipso), 179.91 (NCN). MS (ESI): m/z 387.0 [M-Cl]+.
Synthesis of complexes 4–6.
1
No 13C{ H} NMR spectra could be recorded because of the low
solubility of these compounds.
1·HCl (0.050 g, 0.178 mmol) was dissolved in dry CH2Cl2
and solid [PdCl2(COD)] (0.050 g, 0.178 mmol) was added under
inert atmosphere. The reaction mixture was stirred for 4 h until
formation of a yellow precipitate was observed. The volatiles
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were removed via cannula and the solid washed with pentane
(3 ¥ 25 ml) and dried in vacuo. Complex 4 was isolated as an
orange solid, it is poorly soluble in organic solvents. Yield: 76%.
Anal. Calc. for C11H21Cl3N2PdS2 (458.21): C, 28.83; H, 4.62; N,
6.11. Found: C, 28.58; H, 4.607; N, 5.994. FTIR: nmax(solid)/cm-1:
3131sh, 3095 m, 3046 m, 2966 m, 2926 m, 2869sh, 1616w, 1558 s,
1446 m, 1411 m, 1375w, 1357w, 1334w, 1265 m, 1154 s, 1103w,
1063w, 1044w, 1018sh, 972w, 881w, 829br, 727vs, 698 s, 304vs
(nPd–Cl), 289s (nPd–Cl). 1H NMR (d6-DMSO, 300 MHz) d: 1.17 (6H,
1256 m, 1195w, 1160 m, 1115w, 1069 m, 1057 m, 971w, 952w, 818vs,
754sh, 747sh, 670s. 1H NMR (CD3CN, 300 MHz) d: 1.45 (6H, t,
3J = 7.5 Hz, SCH2CH3), 2.89 (4H, br, SCH2CH3), 3.04 (4H, br,
NCH2CH2S), 4.57 (4H, br, NCH2CH2), 7.23 (2H, s, CH CH).
1
13C{ H} NMR (CD3CN, 75.5 MHz) d: 13.77 (SCH2CH3), 28.97
(SCH2CH3), 32.48 (NCH2CH2S), 49.31 (NCH2CH2S), 123.08
1
(CH CH), 148.94 (NCN). 31P{ H} NMR (CD2Cl2, 121.5 MHz)
1
d: -143.4 (sept., JP,F = 707 Hz, PF6). MS (ESI): m/z 387.0 [M-
PF6]+.
3
3
t, J = 7.2 Hz, SCH2CH3), 2.54 (4H, q, J = 7.5 Hz, SCH2CH3),
Low temperature 1H NMR spectrum: 1H NMR (CD3CN, 223 K,
3
3
3
2.98 (4H, t, J = 6.6 Hz, NCH2CH2S), 4.38 (4H, t, J = 6.6 Hz,
400 MHz) d: 1.36 (3.3H, t, J = 7.6 Hz, SCH2CH3, isomer A),
4
NCH2CH2), 7.82 (2H, d, J = 1.5 Hz, CH CH), 9.24 (1H, s,
1.40 (2.7H, t, 3J = 7.2 Hz, SCH2CH3, isomer B), 2.66 (1H, br m,
SCHHCH3, isomer A), 2.76 (1H, br m, SCHHCH3, isomer A),
2.94 (2H, br m, SCHHCH3, and SCHHCH3, isomer B), 3.06–
3.25 (2.3H, br m, NCH2CH2S, isomer A), 3.33–3.42 (1.7H, br
m, NCH2CH2S, isomer B), 4.24 (2.2H, br m, NCHHCH2S and
NCHHCH2S, isomer A), 4.41 (0.8H, br m, NCHHCH2S, isomer
B), 4.48 (1.0H, br m, NCHHCH2S, isomer B), 7.20 (1.1H, s,
CH CH, isomer A), 7.21 (0.9H, s, CH CH, isomer B).
NCHN). MS (ESI): m/z 423.0 [M-Cl]+.
The same procedure was followed for the formation of complex
5 with 2·HCl (0.100 g, 0.375 mmol) and [PdCl2(COD)] (0.107 g,
0.375 mmol) and afforded complex 5 as an orange solid. Yield:
81%. Anal. Calc. for C10H19Cl3N2PdS2 (444.18): C, 27.04; H,
4.31; N, 6.31. Found: C, 26.71; H, 4.024; N, 6.607. FTIR:
n
max(solid)/cm-1: 305vs (nPd–Cl), 287s (nPd–Cl). 1H NMR (d6-DMSO,
3
300 MHz) d: 1.17 (3H, t, J = 7.3 Hz, SCH2CH3), 2.08 (3H, s,
SCH3), 2.51 (overlapped with solvent peak, SCH2CH3), 2.97 (4H,
br m, 2 NCH2CH2S), 4.40 (4H, q, 3J = 6.5 Hz, 2 NCH2CH2), 7.82
(2H, br s, CH CH), 9.26 (1H, s, NCHN). MS (ESI): m/z 408.9
[M-Cl]+.
The same procedure was followed for the formation of complex
6 with 3·HCl (0.100 g, 0.318 mmol) and [PdCl2(COD)] (0.091 g,
0.318 mmol) and afforded complex 6 as an orange solid. Yield:
84%. Anal. Calc. for C14H19Cl3N2PdS2 (492.22): C, 34.16; H,
3.89; N, 5.69. Found: C, 33.86; H, 4.019; N, 5.771. FTIR:
Synthesis of complexes 8 and 9 via Method B
The same procedure was used with Cs2CO3 (0.122 g, 0.375 mmol),
complex 5 (0.166 g, 0.375 mmol) and KPF6 (0.345 g, 1.87 mmol)
and afforded complex 8 as a yellow solid. Yield: 68%. Anal.
Calc. for C10H18ClF6N2PPdS2 (517.23): C, 23.22; H, 3.51; N, 5.42.
Found: C, 22.82; H, 3.681; N, 5.406. FTIR: nmax(solid)/cm-1:
3143w, 2924w, 1563 m, 1441 m, 1413 m, 1157 m, 1107w, 1025
m, 814vs, 693sh. 1H NMR (CD3CN, 300 MHz) d: 1.35 (3H, t, 3J =
7.4 Hz, SCH2CH3), 2.33 (3H, s, SCH3), 2.76 (4H, br, SCH2CH3),
3.25 (4H, br, 2 NCH2CH2S), 4.61 (4H, br, 2 NCH2CH2), 7.50 (2H,
n
max(solid) cm-1: 306vs (nPd–Cl), 291s (nPd–Cl). 1H NMR (d6-DMSO,
300 MHz) d: 2.09 (3H, s, SCH3), 2.93 (2H, t, 3J = 6.6 Hz,
NCH2CH2SCH3), 3.50 (2H, t, 3J = 6.4 Hz, NCH2CH2SPh), 4.33–
4.43 (4H, m, 2 NCH2CH2), 7.25–7.40 (5H, m, Ph), 7.77 (1H, br s,
CH CH), 7.80 (1H, br s, CH CH), 9.23 (1H, s, NCHN). MS
(ESI): m/z 456.9 [M-Cl]+.
1
br s, CH CH). 31P{ H} NMR (CD2Cl2, 121.5 MHz) d: - 143.4
(sept., 1JP,F = 707 Hz, PF6). MS (ESI): m/z 373.0 [M-PF6]+.
The same procedure was used with Cs2CO3 (0.103 g, 0.318
mmol), complex 6 (0.156 g, 0.318 mmol) and KPF6 (0.292 g,
1.59 mmol) and afforded complex 9 as a yellow solid. Yield:
74%. Anal. Calc. for C14H18ClF6N2PPdS2 (565.27): C, 29.75;
H, 3.21; N, 4.96. Found: C, 29.47; H, 3.009; N, 5.243. FTIR:
Synthesis of complex 7.
Method A: Transmetallation reaction. 1·HCl (0.140 g, 0.498
mmol) was dissolved in dry CH2Cl2 and solid Ag2O (0.116 g, 0.498
mmol) was added under nitrogen. The reaction mixture was stirred
for 2 h in the dark at room temperature. Then the suspension was
filtered through a Celite pad under nitrogen and the resulting
clear solution was slowly added to a suspension of [PdCl2(COD)]
(0.139 g, 0.498 mmol) in CH2Cl2. Awhite solid precipitated rapidly.
The suspension was then filtered through Celite and the solvent
was evaporated under reduced pressure. The resulting orange solid
was then washed with pentane (2 ¥ 25 mL). Yield: 61%.
n
max(solid)/cm-1: 1564w, 1448w, 1413m, 1292w, 1157w, 1034w,
817vs. 1H NMR (CD3CN, 300 MHz) d: 2.33 (3H, s, SCH3), 3.28
(2H, br, NCH2CH2SCH3), 3.41 (2H, br, NCH2CH2SPh), 4.35
(2H, br, NCH2CH2), 4.58 (2H, br, NCH2CH2), 7.28–7.56 (7H,
m, Ph and CH CH). 13C{ H} NMR (CD3CN, 75.5 MHz) d:
1
19.38 (SCH3), 33.14 and 36.93 (2 NCH2CH2S), 46.81 and 49.08 (2
NCH2CH2S), 122.78 and 123.03 (CH CH), 127.14 (Cpara), 129.46
(Cmeta), 129.96 (Cortho), 136.44 (Cipso), (NCN) not observed. 31P{ H}
1
NMR (CD2Cl2, 121.5 MHz) d: -143.4 (sept., 1JP,F = 707 Hz, PF6).
MS (ESI): m/z 421.0 [M-PF6]+.
Method B: Deprotonation of complex 4. Solid Cs2CO3 (0.255 g,
0.783 mmol) was added to a suspension of complex 4 (0.326 g,
0.712 mmol) and KPF6 (0.655 g, 3.56 mmol) in acetonitrile and
the reaction mixture was refluxed for 6 h. During the heating,
the colourless liquid phase became orange. The suspension was
then filtered through Celite and the solvent was evaporated
under reduced pressure. The resulting orange solid was then
washed with pentane (2 ¥ 25 mL). Yield: 79%. Anal. Calc. for
C11H20ClF6N2PPdS2 (531.94): C, 24.87; H, 3.79; N, 5.27. Found: C,
24.63; H, 3.826; N, 5.066. FTIR: nmax(solid)/cm-1: 2970br, 2934w,
1566 m, 1474 s, 1440 s, 1415 s, 1380 m, 1341 m, 1333 m, 1265 m,
Synthesis of complex 11
Following Method A: Transmetallation reaction, with imida-
zolium 10·HI (0.120 g, 0.298 mmol), Ag2O (0.069 g, 0.298 mmol)
and [PdCl2(COD)] (0.085 g, 0.298 mmol) afforded complex 11 as
an orange powder. Yield: 87%. Anal. Calc. for C16H22Cl2N2PdS
(451.75): C, 42.54; H, 4.91; N, 6.20. Found: C, 42.84; H, 4.87;
N, 6.07. FTIR: nmax(solid)/cm-1: 3113w, 3087w, 2966 m, 2919 m,
2858 m, 1609w, 1564w, 1485 m, 1449 m, 1404 s, 1375 m, 1347
m, 1300 m, 1262 m, 1238 m, 1203 m, 1156 m, 1110w, 1088w,
8826 | Dalton Trans., 2010, 39, 8820–8828
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Table 1 Crystallographic data for complex 11·CH2Cl2
Acknowledgements
Compound reference
Chemical formula
Formula mass
11·CH2Cl2
We are grateful to the CNRS, the Ministe`re de l’Enseignement
Supe´rieur et de la Recherche (Paris), the DFH/UFA (Interna-
tional Research Training Group 532-GRK532 of the Deutsche
Forschungsgemeinschaft) and the Erasmus Program for support.
A. S. is grateful for the support from the University of Camerino
(Italy). We thank Dr Roberto Pattacini for the determination of
the crystal structure of 11·CH2Cl2 and Marc Mermillon-Fournier
for technical assistance.
C16H22Cl2N2PdS· CH2Cl2
536.64
Crystal system
Monoclinic
12.778(1)
11.845(1)
14.879(2)
103.886(4)
2186.0(3)
173(2)
P21/c
4
1.437
12428
5857
0.0413
0.0490
0.1138
0.0964
0.1348
1.045
˚
a/A
˚
b/A
˚
c/A
b (◦)
3
˚
Unit cell volume/A
T/K
Space group
Z
Absorption coefficient, m/mm-1
No. of reflections measured
No. of independent reflections
Rint
Notes and references
1 H. Jacobsen, A. Correa, A. Poater, C. Costabile and L. Cavallo, Coord.
Chem. Rev., 2009, 253, 687.
2 (a) P. de Fre´mont, N. Marion and S. P. Nolan, Coord. Chem. Rev.,
2009, 253, 862; (b) F. E. Hahn and M. C. Jahnke, Angew. Chem., Int.
Ed., 2008, 47, 3122; (c) F. E. Hahn, Angew. Chem., Int. Ed., 2006, 45,
1348; (d) N. M. Scott and S. P. Nolan, Eur. J. Inorg. Chem., 2005, 1815;
(e) W. A. Herrmann, Angew. Chem., Int. Ed., 2002, 41, 1290; (f) D.
Bourissou, O. Guerret, F. P. Gabba¨ı and G. Bertrand, Chem. Rev.,
2000, 100, 39.
R1 values (I > 2s(I))
wR(F2) values (I > 2s(I))
R1 values (all data)
wR(F2) values (all data)
S on F2
3 (a) N. Marion and S. P. Nolan, Acc. Chem. Res., 2008, 41, 1440;
(b) E. A. B. Kantchev, C. J. O’Brien, M. G. Organ and Angew, Angew.
Chem., Int. Ed., 2007, 46, 2768; (c) C. Fliedel, A. Maisse-Franc¸ois and
S. Bellemin-Laponnaz, Inorg. Chim. Acta, 2007, 360, 143.
4 (a) M. C. Jahnke, T. Pape and F. E. Hahn, Eur. J. Inorg. Chem., 2009,
1960; (b) M. V. Jime´nez, J. J. Pe´rez-Torrente, M. I. Bartolome´, V.
Gierz, F. J. Lahoz and L. A. Oro, Organometallics, 2008, 27, 224;
(c) A. A. Danopoulos, N. Tsoureas, S. A. Macgregor and C. Smith,
Organometallics, 2007, 26, 253; (d) N. Stylianides, A. A. Danopoulos
and N. Tsoureas, J. Organomet. Chem., 2005, 690, 5948; (e) L. H.
Gade, V. Ce´sar and S. Bellemin-Laponnaz, Angew. Chem., Int. Ed.,
2004, 43, 1014; (f) V. Ce´sar, S. Bellemin-Laponnaz and L. H. Gade,
Organometallics, 2002, 21, 5204; (g) D. S. McGuinness and K. J. Cavell,
Organometallics, 2000, 19, 741.
1034 m, 969 m, 935w, 883w, 852 m, 731vs, 694vs, 319 s (nPd–Cl),
1
3
300 s (nPd–Cl). H NMR (CDCl3, 300 MHz) d: 1.50 (3H, t, J =
7.2 Hz, SCH2CH3), 2.18 (6H, s, 2 CH3 ortho-Mes), 2.31 (3H, s, CH3
para-Mes), 2.78 (2H, br, SCH2CH3), 3.28 (2H, br, NCH2CH2),
4.67 (2H, br, NCH2CH2), 6.80 (1H, br s, CH=CH), 6.95 (2H, s,
CH meta-Mes), 7.38 (1H, br s, CH CH). MS (ESI): m/z 417.0
[M-Cl]+.
Procedure for the Suzuki–Miyaura cross-coupling reaction
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Complex 7 (10.63 mg, 0.02 mmol), phenyl boronic acid (146.3 mg,
1.20 mmol) and Cs2CO3 (651.6 mg, 2.00 mmol) were placed in a
Schlenk tube and dioxane (3 ml) was added under nitrogen. Then
4-bromotoluene (123.1 ml, 171.0 mg, 1.00 mmol) was added and
◦
the reaction mixture was heated for 2 h at 100 C. The reaction
was then quenched by rapid cooling down to room temperature
and the suspension was filtered through a Celite pad. The resulting
solution was then analysed by gas chromatography and showed
83% conversion in 4-methyl-biphenyl.
The same procedure was used with complexes 11 (9.04 mg,
0.02 mmol) and 12 (7.15 mg, 0.02 mmol), showing 77% and 64%
conversion, respectively.
X-Ray data collection, structure solution and refinement
Suitable crystals for the X-ray analysis of 11·CH2Cl2 were obtained
by slow diffusion of pentane into a saturated dichloromethane
solution of complex 11. The intensity data were collected on
a Kappa CCD diffractometer19 (graphite monochromated Mo-
˚
Ka radiation, l = 0.71073 A) at 173(2) K. Crystallographic
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into the geometrically calculated positions (SHELXS-97 proce-
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MULTISCAN correction was applied.21 CCDC 781531.†
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The Royal Society of Chemistry 2010
Dalton Trans., 2010, 39, 8820–8828 | 8827
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©