Synthesis of novel palladium allyl complexes bearing heteroditopic NHC-S ligands. kinetic study on the carbene exchange between bis-carbene palladium allyl complexes

Article abstract of DOI:10.1016/j.jorganchem.2013.01.016

We have synthesized several novel palladium allyl and 1,1-dimethylallyl complexes bearing different heteroditopic NHC-S ligands giving rise to a five-membered chelate ring with the metal center. We were able to synthesize some homoleptic bis-carbene allyl derivatives by taking advantage of the hemilability of the thioetheric sulfur. Attempts at preparing mixed bis-carbene complexes bearing two different heteroditopic carbenes (i.e. NHC-S and NHC-Py) simultaneously coordinated to the palladium center lead to a carbene transmetalation with the formation of a statistically distributed equilibrium mixture of the two pure homoleptic and of the mixed bis-carbene palladium allyl complexes in solution. In two different cases the rate of the equilibrium reaction was measured and a mechanistic hypothesis provided. Finally, we have determined the solid state structures of a complex bearing only one NHC-S heteroditopic carbene and of the bis-carbene (NHC-S, NHC-Py) palladium allyl derivatives.

Full text of DOI:10.1016/j.jorganchem.2013.01.016

Journal of Organometallic Chemistry 732 (2013) 27e39
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Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Synthesis of novel palladium allyl complexes bearing heteroditopic NHCeS
ligands. Kinetic study on the carbene exchange between bis-carbene palladium
allyl complexes
,
a
a
a
b
Luciano Canovese a , Fabiano Visentin , Carlo Levi , Claudio Santo , Valerio Bertolasi
*
a Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari, Calle Larga S. Marta, 30129 Venice, Italy
b Dipartimento di Chimica e Centro di Strutturistica Difrattometrica, Università di Ferrara, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
We have synthesized several novel palladium allyl and 1,1-dimethylallyl complexes bearing different
heteroditopic NHCeS ligands giving rise to a five-membered chelate ring with the metal center. We were
able to synthesize some homoleptic bis-carbene allyl derivatives by taking advantage of the hemilability
of the thioetheric sulfur. Attempts at preparing mixed bis-carbene complexes bearing two different
heteroditopic carbenes (i.e. NHCeS and NHCePy) simultaneously coordinated to the palladium center
lead to a carbene transmetalation with the formation of a statistically distributed equilibrium mixture of
the two pure homoleptic and of the mixed bis-carbene palladium allyl complexes in solution. In two
different cases the rate of the equilibrium reaction was measured and a mechanistic hypothesis provided.
Finally, we have determined the solid state structures of a complex bearing only one NHCeS hetero-
ditopic carbene and of the bis-carbene (NHCeS, NHCePy) palladium allyl derivatives.
Received 22 October 2012
Received in revised form
15 January 2013
Accepted 18 January 2013
Keywords:
Palladium allyl complexes
Heteroditopic carbene ligands
Carbene exchange reaction
Ó 2013 Elsevier B.V. All rights reserved.
1. Introduction
by monodentate carbene ligands [7]. On the contrary, the bidentate
heteroditopic derivatives are comparatively less common [8]
The family of efficient
s
donor N-heterocyclic carbenes (NHC)
whereas the NHCeS complexes represent a rarity [5c,d], although
the thioether wing might impart peculiar catalytic properties to
their complexes owing to the stereogenic nature of the coordinated
sulfur [5k].
which impart a remarkable stability and catalytic performances to
their transition metal derivatives [1], has been soon extended to
include a new class of bidentate ligands carrying another coordi-
nating functionality. The coordination of heteroditopic NHCeE
(E ¼ P, N, O) ligands to transition metals yields an important class
of new compounds [2]. In particular, the complexes characterized
by a secondary, labile heteroatom act as efficient and stable cata-
lysts since the dangling wing can restore the starting complexes by
re-coordination of the site made vacant by their catalytic activity
[3]. We have been long involved in the study of the synthesis,
behavior in solution and reactivity of Pd(0) and Pd(II) complexes
with bidentate or terdentate ligands bearing at least one thioether
function [4]. Thus, owing to the not particularly high number of
heteroditopic bidentate sulfurecarbene ligands in the literature [5],
we decided to synthesize some new NHCeS chelating moieties and
the corresponding palladium allyl complexes. We undertook such
an investigation since the majority of NHC palladium allyl com-
plexes displaying a marked catalytic activity [6] is mainly stabilized
The NHCeS ligands that can form five-membered CeS ring upon
coordination to a metal center, are also rare [5h,l,n] and no allyl
derivatives with this kind of spectator ligands are reported in the
literature. In addition, it is known that two different heteroditopic
carbene ligands bearing nitrogen or sulfur as secondary atom can
simultaneously coordinate to either Pd(0) [5n,9] or Pd(II) [10] and
this very fact might suggest interesting studies on the possible
carbene exchange. As a matter of fact, despite the great deal of
papers on the transmetalation reactions involving different metals
such as the carbonyl carbene complexes of the group 6 metals [11]
or AgBr(NR,NCH2R0-NHC) substrates [12] with several different
transition metal derivatives, to the best of our knowledge no
studies on the carbene exchange between Pd(II) compounds have
appeared in the literature, although Caddick and Cloke have already
demonstrated the feasibility of carbene exchange in Pd(0) com-
plexes, whereas Yamamoto and Espinet have found that the aryl
groups can exchange between Pd(II) aryl complexes [13]. In the
present study we show that the allyl palladium derivatives bearing
five-membered NHCeS ligands can be easily synthesized and that
* Corresponding author. Tel.: þ39 (0)41 2348571; fax: þ39 (0)41 2348517.
E-mail address: cano@unive.it (L. Canovese).
0022-328X/$ e see front matter Ó 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.jorganchem.2013.01.016

28
L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
the transmetalation reaction involving exchange of the hetero-
bidentate ligands between different palladium allyl complexes
takes place through an associative mechanism that is strongly
dependent on the nature of the dangling wing.
donating atom often undergo rapid inversion of the sulfur absolute
configuration at RT. At low temperature such an inversion is frozen
and the consequent formation of a second chiral center becomes
apparent since a couple of diastereoisomers due to the different
mutual orientation between the allyl central atom and the sub-
stituent at the chiral sulfur can be detected [4]. As a matter of fact,
the low temperature 1H NMR spectra of the title complexes
(ꢀ193 K) display the splitting of each group of signals related to the
allyl protons into two further groups of signals with different in-
tensity, which can be traced back to the different diastereoisomers
(Supplementary material; Fig. 2 SM).
2. Results and discussion
2.1. Palladium allyl complexes
We have firstly synthesized the imidazolium salts described in
Scheme 1 by reacting the suitable R-imidazole with chloromethyl-
methyl sulfide, chloromethyl-phenyl sulfide or chloromethyl-
pyridine in acetonitrile in the presence of KBr (Scheme 1):
1a and 1c represent newly synthesized ligands, whereas 1b [5l],
1d [5n] are literature compounds. All the bidentate NHCeS ligands
in Scheme 1 form a five-membered chelate ring upon complexation
with the group 10 metals.
The RT 13C NMR spectra display two well separated signals due
to the peripheral allyl carbons. The allyl carbon trans to carbene
affected by the highest trans influence [18] resonates at ca. 70 ppm,
whereas the allyl carbon trans to sulfur is detected at ca. 50 ppm.
Finally, the coordinated carbon of the carbene moiety resonates at
ca. 180 ppm.
Moreover, the nature of the cationic complexes 4 is confirmed
by their IR spectra displaying the characteristic stretching and
The silver carbene derivatives (2) were then obtained in rea-
sonable yield (70e90%) by reacting the imidazolium salts 1 with
Ag2O in CH2Cl2 [2f,g]. Moreover, for reasons that will be discussed
further on and according to published procedures we have syn-
thesized the complex {[1-(2-pyridyl)methylene-3-methyl]imida-
zolyl-2-ene}silver bromide (2e) [14]. The disappearance of the
broad signal of the acidic C2-H proton of the imidazolium salt at
w10 ppm in the 1H NMR spectrum and the appearance of the signal
related to the coordinated carbene carbon at w180 ppm in the 13C
NMR testified the progress of the reaction. Finally, taking advantage
of the synthetic strategy based on Ag(I) carbene transfer developed
by Lin et al. [15] and widely employed by other authors, we have
carried out the synthesis of the title complexes 4 by means of
a slight modification of Li’s method [16]. Thus, the transfer of car-
bene from the Ag(I) derivative to the palladium allyl chloro dimer
was followed by dechlorination of the firstly formed monodentate
carbene allyl chloro complexes 3 with a solution of NaClO4 in
methanol (Scheme 2):
ꢁ
bending bands of the ClO4 counter-ion at ca. 1080 and 620 cmꢁ1
respectively.
,
When NaClO4 is not added, the reaction of the complexes of type
2 with palladium chloro allyl dimer yields the corresponding
monodentate NHC chloro allyl derivatives 3 (Scheme 2). Complexes
3aed have not been isolated but their 1H NMR spectra have been
recorded in situ. They are characterized by a remarkable up-field
shift of both the syn and anti allyl protons trans to chloride with
respect to those trans to sulfur in complexes 4aed, whereas those
trans to the carbene carbon do not shift significantly [7a,19]. At
variance with chloride, which confirms its remarkable coordinative
capability in non coordinating solvents [16], this phenomenon is
strictly related to the not particularly strong coordinative nature of
the thioetheric sulfur toward Pd(II) [4] which in this case is almost
independent of the substituent at sulfur. The CH2eS protons of
complexes 3aed are detected as an AB system which is however
considerably narrower than that of the corresponding derivatives
4aed. Such a not unprecedented phenomenon is probably due to
sterically hampered free rotation of the substituents at the unco-
ordinated sulfur [20].
The [1-(2-pyridyl)methylene-3-methyl]imidazolyl-2-ene de-
rivatives 2e [14], 3e and 4e obtained by similar procedure, are
shown in Chart 1.
The structure of the chelate allyl complexes 4aed in solution is
clearly apparent from comparison of their NMR spectra with those
of the derivatives 3 (vide post). The heterotopicity of spectator li-
gands is reflected in the spectroscopic behavior of the allyl frag-
ment for which five distinct signals are detectable in the 1H NMR
spectra at RT. In particular, the syn and anti peripheral allyl protons
trans to carbene resonate at higher field than the corresponding
protons trans to the thioether group (Supplementary material;
Fig. 1SM). In addition, the coordination of the sulfur is inferred
from the diastereotopism of the endocyclic CH2eS protons reso-
nating as an AB system centered at ca. 5.5 ppm [17]. The allyl pal-
ladium complexes bearing the thioetheric sulfur as secondary
2.2. Palladium Me2-allyl complexes
Similarly to the synthetic protocol reported in Scheme 2, the
transmetalation reaction between the silver derivatives 2 and the
1,1-dimethyl allyl palladium chloro dimer in the presence of NaClO4
yields the complexes 5 (Chart 2). Significantly, at RT only the isomer
with the di-methyl substituted allyl termini trans to the carbene is
present in solution.
The assignment of the structure of complexes 5 in solution is
easily achieved by HMBC analysis which displays an intense cross-
peak between the carbene carbon and the protons of the methyl
substituents of the terminal allyl carbon (Supplementary material;
Fig. 3 SM). As a matter of fact, it was shown that such phenomenon
is observable when the carbene and the bis-substituted allyl carbon
occupy a mutual trans position [21]. The hypothesized structure
was definitely confirmed by X-ray crystallographic analysis of 5b
(vide infra).
The marked trans influence and the consequent trans effect
exerted by unhindered carbenes when compared with pyridine and
even with phosphines was clearly pointed out by Danopoulos and
co-workers in the case of the protonation of dimethyl palladium
complexes bearing unsymmetrical phosphino-pyridine spectator
ligands [8a]. Therefore, it is not quite surprising that the trans in-
fluence exerted by the carbene forces the less coordinating allyl
termini to the trans position. However, the complete selectivity of
Scheme 1.

L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
29
Scheme 2.
the phenomenon observed in the case of all palladium Me2-allyl
complexes 5 is remarkable since it was never observed in similar
complexes bearing different heteroditopic ligands [22].
(Chart 3) by reacting the complex 2e with 4e. Complex 6e behaves
in solution similarly to derivatives 6a and 6b and therefore the
relevant features of their 1H and 13C NMR spectra are quite com-
parable (see Experimental).
In order to rationalize the reaction rates observed for the trans-
metalation between the complexes 6a and 6e and to obtain an un-
ambiguous kinetic response, we have synthesized the monodentate
ligands 1-methyl-3-(benzyl)-2,3-dihydro-1H-imidazolium bromide
1f and 1-(4-methyl-benzyl)-3-methyl-2,3-dihydro-1H-imidazolium
bromide 1g by quaternization of the 1-methyl-1H-imidazole with 1-
2.3. Palladium bis-carbene allyl complexes
According to Scheme 3, addition of the Ag(I) carbene derivatives
2 to complexes 4 causes fast and complete formation of the bis-
carbene allyl palladium substrates 6 [23]. It is noteworthy that
these reactions are effective only when at least one of the imidazole
substituents is the poorly hindered methyl group.
chloromethyl-benzene
or
1-chloromethyl-4-methyl-benzene,
respectively in acetonitrile in the presence of KBr. The corresponding
bis-carbene allyl derivatives were prepared by dechlorination with
AgBF4 of the complexes 3f and 3g which were obtained by reacting
Owing to the enhanced symmetry of complexes 6, the ensuing
RT 1H spectra appear considerably simplified with respect to those
of complexes 4. Thus, only one doublet ascribable to the syn and
one for the anti protons together with the multiplet of the central
allyl proton integrating 2:2:1, respectively, are detectable. More-
over, the protons of the CH3eN group coordinated to both ligands
resonate as an independent singlet. Similar behavior is observed in
the case of the CH2eS protons although they are no longer dia-
stereotopic as a consequence of the de-coordination of sulfur.
Consistently, in the 13C NMR spectra both carbons of the allyl ter-
mini resonate as only one singlet. Finally, the carbene carbons
resonate at ca. 180 ppm without any significant shift with respect to
those of the starting complexes 4.
the substrates 2f and 2g with [Pd(h m-Cl)]2 followed by a fur-
3-allyl)(
ther attack of 2f or 2g at the solvato species (Scheme 4). It is note-
worthy that similar complexes were only identified by Cavell and co-
workers as by-products in the synthesis of mixed NHCephosphine
Pd allyl derivatives, but never isolated [24].
2.4. Exchange between carbenes in Pd(II) allyl complexes
The carbene transfer between Pd(0) complexes has been
described by Caddick and Cloke [13]. However, a similar reaction
involving Pd(II) carbene derivatives was never studied. Such an
exchange reaction was even ruled out by Chen and co-workers on
Following the same synthetic protocol used for the synthesis
of complexes 6a, b (vide supra), we synthesized the complex 6e
Chart 1. Complexes 2e, 3e and 4e.

30
L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
Chart 3. Complex 6e.
involved. In Fig. 1 we show the 1H NMR spectra and the concen-
tration vs. time plot in the case of the reaction between 6a and 6f
complexes. The mathematical treatment was carried out by
a locally adapted program written in the SCIENTISTÒ environment.
All the concentration vs. time plots and the mathematical analysis
are reported in Figs. 4 SM, 5 MI, 6 SM and equation (1) SM in
Supplementary material.
Although the equilibrium constants KE calculated as the ratios of
rate constants reasonably fit the estimated values obtained from
integration of the 1H NMR signals of the equilibrium mixture, the
reaction rates raise some perplexity since the observed trend is
apparently inconsistent.
As a matter of fact, the rate of reaction between the complexes
bearing a coordinating function in the dangling wing (6a and 6e to
give 7) is higher than that related to the formation of 8 (only 6a
bears a coordinating function) but smaller than that for 7 (no
coordinating function is present in the wings of 6f and 6g). We
think that a possible interpretation shouldn’t take into account the
activation energy required for the formation of the species that
reasonably represents the intermediates involved in different re-
actions. Thus, in all cases studied the carbene transfer occurs as
a consequence of the formation of a dimeric transition state which
can be represented in Chart 4 in the case of complexes 7, 8 and 9,
according to the classical theory of nucleophilic attack in d8
complexes:
Therefore, the formation of 9 involves an intermediate of type I1
whereas the presence of a second coordinating function in the
dangling wing might impose the formation of other types of in-
termediates (I2 and I3) which would collapse slowly into the
products 7 and 8. The doubly bridged intermediate I2 appears to be
more reactive than I3 probably because its more compact structure
favors the subsequent interaction between the carbene carbons
and the metal.
Chart 2. Complexes 5.
the basis of the observation that dimeric complexes of the type
[Pd(NHC)Cl2]2 never convert into the [Pd(NHC)2Cl2] species [25].
However, in an attempt at preparing mixed carbene derivatives in
situ we have reacted equimolecular solutions of the complexes 4a
and 2e in CD2Cl2 at RT in an NMR test tube. It was clear that the
immediately formed complex 7 slowly evolves into an equilibrium
mixture of three different statistically distributed (50, 25, 25%,
respectively) chemical species, namely complexes 7, 6a and 6e
(Scheme 5).
We therefore surmise that the transmetalation involving two
palladium(II) complexes is possible in some cases. Therefore, with
the aim of exploring the feasibility and the potentiality of such
reaction, we decided to plan further experiments in which equi-
molecular solutions of two homoleptic but different bis-carbene
allyl palladium complexes were mixed together. Preliminary 1H
NMR experiments involving complexes 6a, 6b and 6e clearly indi-
cated that the reaction occurs, although not completely, and again
an equilibrium mixture was detected at the end of the process. As
expected, owing to the presumably very similar
D
Gꢂf of all the
complexes involved, the products of the equilibrium reaction were
obtained in a statistical distribution (KE y 4) [22c]. Therefore, we
decided to study quantitatively by 1H NMR the reactions involving
complexes 6a, 6e and 6a, 6f and eventually 6f, 6g. Thus, we have set
up kinetic experiments in an attempt at determining the mecha-
nism of the transmetalation reaction. In Scheme 6, the reactions
studied and the related reaction products 7, 8 and 9, are listed.
Table 1 reports a summary of the kinetic data determined by
non linear regression analysis of the concentrationetime profiles as
deduced from the NMR integration of selected signals of the species
Scheme 3.

L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
31
Scheme 4.
2.5. Crystal structure determinations
and h
3-coordinated to the 1,1-dimethyl substituted allyl group. The
trans effect exerted by the carbene atom can be evidenced by the
ꢀ
The asymmetric unit of compound 5b contains two indepen-
dent ionic couples. ORTEP [26] views of both independent Pd(II)
cationic complexes 5b and of the Pd(II) cationic complex 6d are
reported in Figs. 2 and 3. A selection of bond distances and angles
is given in Tables 2 and 3. In complex 5b the palladium is bonded
to a dissymmetric NHC bidentate ligand through the carbene car-
bon and the sulfur atom of the methylthiomethyl N-substituent
longer Pd1eC3 distances of 2.235(3) A as compared to those where
a terminal allyl carbon is in trans position to the sulfur atoms:
ꢀ
(Pd1eC1 ¼ 2.108(4) and 2.131(4) A for the cations A and B,
respectively).
In the cationic complex 6d the palladium is bonded to two
carbene carbons of two dissymmetric NHC ligands and
nated to the allyl group.
h
3-coordi-
Scheme 5.

32
L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
Scheme 6.
The 1,1-dimethyl substituted allyl group is almost perpendicular
equilibrium mixture. When possible, we have calculated the reac-
tion rates relating to the equilibrium reaction and surmised
a plausible mechanism.
to the Pd(II) basal coordination plane in both cationic complexes of
compound 5b, forming dihedral angles in the range of 85.2(6)e
86.9(2)ꢂ (Table 2), whereas in the cationic complex 6d the allyl
group forms an angle of 68.2(7)ꢂ with the basal Pd(II) coordination
plane (Table 3).
4. Experimental
4.1. Solvents and reagents
3. Conclusions
All solvents were purified by standard procedures and distilled
under argon immediately before use. 1D- and 2D-NMR spectra
were recorded using a Bruker 300 Avance spectrometer. Chemical
shifts (ppm) are given related to TMS (1H and 13C NMR). Peaks are
We have synthesized and characterized some potentially five-
membered NHCeS ligands and the corresponding new chelate
palladium allyl derivatives by transmetalation between the silver
carbene derivatives AgBr(NR,NCH2SR0-NHC) and the Pd(II) allyl
chloro dimer, followed by dechlorination of the monodentate de-
rivative with NaClO4. In the case of the reaction involving the dimer
[Pd(h m-Cl)]2 only the complex with the bis-substituted
2-Me2-ally)(
allyl terminus trans to the carbene carbon was obtained in any case.
Furthermore, we have synthesized and characterized some palla-
dium bis-carbene allyl derivatives and shown that the carbene
fragments can be easily exchanged between different bis-carbene
complexes giving rise to an equilibrium situation in which the
starting and final complexes generate a statistically distributed
Table 1
Second order rate constants and calculated and estimated equilibrium constants for
the carbene exchange reaction in complexes 6a, 6e; 6a, 6f; 6f, 6g.
Formed
complex
k2 ꢃ 10ꢁ2
k
ꢁ2 ꢃ 10ꢁ2
KE
(molꢁ1 dm3 sꢁ1
)
(molꢁ1 dm3 sꢁ1
)
7
8
9
4.9 ꢄ 0.2
0.22 ꢄ 0.01
Fast
1.2 ꢄ 0.2
0.067 ꢄ 0.001
Fast
4.1 ꢄ 0.7a (w4b)
3.2 ꢄ 0.2a (w4b)
(w4b)
Fig. 1. Simplified plot of concentration vs. time (s) for the reaction: 6a þ 6e ¼ 2 $ 8
[6a] ¼ 9.7 ꢃ 10ꢁ3, [6e] ¼ 1.3 ꢃ 10ꢁ2 (mol dmꢁ3). For the sake of clarity the concen-
a
Calculated values (KE ¼ k2/kꢁ2).
tration of 6e and several concentrations of 6a (,) and 8 (D) vs time data (three every
b
Estimated value obtained from 1H NMR integration of the equilibrium mixture.
four) were omitted.

L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
33
Fig. 3. An ORTEP view of Pd(II) cationic complex 6d showing the thermal ellipsoids at
30% probability level.
in SI together with the dedicated program written in the SCIEN-
TISTÒ environment.
Chart 4. Dimeric transition state formed by the complexes 7, 8 and 9.
labeled as singlet (s), doublet (d), triplet (t), quartet (q), multiplet
(m) and broad (b). The proton and carbon assignments were carried
out by 1He2D COSY, 1He2D NOESY, 1He13C HMQC and HMBC
experiments.
IR spectra were recorded on a PerkineElmer Spectrum One
spectrophotometer.
4.3. Synthesis of the N-arylimidazoles (1)
The N-arylimidazoles 1b [5l], 1d [5n] and 1e [14] are literature
products and were synthesized accordingly.
4.3.1. 1-Methyl-3-methylsulfanylmethyl-2,3-dihydro-1H-
imidazolium bromide (1a)
4.2. Kinetic measurements
To a suspension of 1.96 g of KBr in 100 mL of anhydrous aceto-
nitrile 0.92 mL (11 mmol) of chloromethylsulfide and 0.97 mL
(12.1 mmol) of 1-methyl-1H-imidazole were added under inert
atmosphere (Ar). The mixture was vigorously stirred for 24 h and
the solvent removed by a rotary evaporator. The residual was dis-
solved in CH2Cl2 (20 mL) and KBr filtered off on a celite filter. The
solution was completely dried under vacuum and the oily residual
was washed with diethyl ether and dried under vacuum. 2.1 g (yield
88%) of the title product were obtained as a pale yellow oil.
The transmetalation reactions were followed by 1H NMR tech-
nique by dissolving one of the complexes under study (6a or 6f) in
0.8 mL of CD2Cl2 ([complex] w0.01 mol dmꢁ3) at 25 ꢂC. An equi-
molar aliquot of the reacting counterpart (6e, 6f or 6g) was added
as a solid and the reaction was followed to completion by mon-
itoring the disappearance of the starting complexes and the con-
comitant appearance of the final bis-carbene species. The plots of
the concentrationetime profiles of the substrates involved (calcu-
lated from integration of the 1H NMR relevant peaks) are reported
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 2.26 (s, 3H, S-CH3), 4.12 (s,
3H, N-CH3), 5.58 (s, 2H, CH2S), 7.59 (t, J ¼ 1.7 Hz, 1H, CH]CH Im),
Fig. 2. ORTEP views of both Pd (II) cationic complexes of compound 5b showing the thermal ellipsoids at 30% probability level.

34
L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
Table 2
4.3.2. 1-(2,6-Diisopropyl-phenyl)-3-methylsulfanylmethyl-2,3-
dihydro-1H-imidazolium bromide (1c)
White solid. Yield 93%.
Selected bond distances and angles (A and ꢂ) for 5b.
ꢀ
A
B
1H NMR (CDCl3, T ¼ 298 K, ppm)
d
: 1.19 (d, J ¼ 6.8 Hz, 6H, Pr-
i
Distances
Pd1eC1
Pd1eC2
Pd1eC20
Pd1eC3
Pd1eC6
Pd1eS1
C1eC2
C1eC20
C2eC3
C20eC3
C6eN1
C6eN2
CH3), 1.28 (d, J ¼ 6.8 Hz, 6H, iPr-CH3), 2.32 (sept, 2H, J ¼ 6.8 Hz, iPr-
CH), 2.37 (s, 3H, S-CH3), 6.09 (s, 2H, CH2S), 7.23 (bt, 1H, CH]CH Im),
7.34 (d, J ¼ 7.8 Hz, 2H, m-aryl-H), 7.57 (t, J ¼ 7.8 Hz, 2H, p-aryl-H),
8.01(bt, 1H, CH]CH Im), 10.82 (bt, 1H, NCHN).
2.108(4)
2.131(4)
2.152(3)
2.132(5)
2.230(11)
2.235(3)
2.026(3)
2.3703(8)
1.439(9)
1.384(14)
1.363(7)
1.439(14)
1.343(4)
1.348(4)
2.235(3)
2.026(3)
2.3545(9)
1.459(6)
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 14.3 (CH3, S-CH3), 23.9
i
i
i
(CH3, Pr-CH3), 24.4 (CH3, Pr-CH3), 28.7 (CH, Pr-CH), 52.7 (CH2,
SCH2),123.0 (CH, CH]CH Im),124.4 (CH, CH]CH Im),124.6 (CH, m-
aryl-CH); 129.9 (C, i-aryl-C); 131.9 (CH, p-aryl-CH); 138.2 (CH,
NCHN); 145.5 (C, o-aryl-C).
1.395(5)
1.353(4)
1.354(4)
Angles
4.3.3. 1-Methyl-3-(benzyl)-2,3-dihydro-1H-imidazolium bromide
(1f)
Sticky yellowish oil (washed with diethyl ether and pentane).
Yield 92%.
C1ePd1eS1
C2ePd1eS1
C20ePd1eS1
C3ePd1eS1
C1ePd1eC6
C2ePd1eC6
C20ePd1eC6
C3ePd1eC6
S1ePd1eC6
C1ePd1eC2
C1ePd1eC20
C1ePd1eC3
C2ePd1eC3
C20ePd1eC3
C1eC2eC3
C1eC20eC3
Dihedral angles
169.8(1)
131.5(2)
133.3(49
101.5(1)
106.5(1)
141.2(2)
135.8(3)
173.2(1)
83.6(1)
39.7(2)
37.2(4)
68.4(1)
36.3(2)
168.3(1)
132.1(1)
100.5(1)
106.4(1)
141.8(1)
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 3.99 (s, 3H, N-CH3), 5.53 (s, 2H,
CH2N), 7.27e7.32 (m, 3H, aryl-H), 7.42e7.46 (m, 3H, CH]CH Im, aryl-
H), 7.56 (t, J ¼ 1.8 Hz, 1H, CH]CH Im), 10.25 (bt, 1H, NCHN). 13C {1H}
171.2(1)
83.9(1)
39.8(2)
NMR(CDCl3, T¼ 298K, ppm)
d:36.7(CH3, N-CH3), 53.0(CH2, Ph-CH2),
122.0 (CH, CH]CH Im), 123.7 (CH, CH]CH Im), 128.9 (CH, m-Ph);
129.2 (CH, o-Ph); 129.3 (CH, p-Ph); 133.0 (C, i-Ph); 136.9 (CH, NCHN).
68.6(1)
37.0(1)
4.3.4. 1-(4-Methyl-benzyl)-3-methyl-2,3-dihydro-1H-imidazolium
bromide (1g)
Sticky yellowish oil (washed with diethyl ether and pentane).
Yield 96%.
37.6(3)
121.2(6)
119.5(1)
119.1(3)
86.2(2)
Pd1,C1,C2,C6,S1 ˇ C1,C2,C3,C4,C5
Pd1,C1,C20,C6,S1 C1,C20,C3,C40,C5
86.9(2)
85.2(6)
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 1.34 (s, 3H, tolyl-CH3), 4.08 (s,
ˇ
3H, N-CH3), 5.52 (s, 2H, CH2N), 7.19 (d, J ¼ 7.8 Hz, 2H, aryl-H), 7.29 (t,
J ¼ 1.8 Hz, 1H, CH]CH Im), 7.36 (d, J ¼ 7.8 Hz, 2H, aryl-H), 7.43 (t,
J ¼ 1.8 Hz, 1H, CH]CH Im), 10.55 (bt, 1H, NCHN). 13C {1H} NMR
7.74 (t, J ¼ 1.7 Hz, 1H, CH]CH Im), 10.47 (bs, 1H, NCHN). 13C {1H}
(CDCl3, T ¼ 298 K, ppm)
d: 21.1(CH3,Ph-CH3), 36.7 (CH3, N-CH3),
53.0 (CH2, Ph-CH2), 121.8 (CH, CH]CH Im), 123.6 (CH, CH]CH Im),
128.9 (CH, m-Ph); 129.9 (CH, o-Ph); 129.9 (C, i-Ph); 137.0 (CH,
NCHN); 139.4 (C, p-Ph).
NMR (CDCl3, T ¼ 298 K, ppm)
d: 14.9 (CH3, S-CH3), 37.0 (CH3, N-
CH3), 52.9 (CH2, SCH2), 121.8 (CH, CH]CH Im), 123.7 (CH, CH]CH
Im), 137.4 (C, NCHN).
The following compounds were synthesized by a similar
procedure.
4.4. Synthesis of AgBr(NR,NCH2SR0-NHC) carbene derivatives
The N-arylimidazoles 2b [5l], 2d [5n] and 2e [14] are literature
products and were synthesized accordingly.
Table 3
Selected bond distances and angles (A and ꢂ) for 6d.
ꢀ
4.4.1. AgBr(NMe,NCH2SMe-NHC) (2a)
Distances
To 0.4633 g (2.09 mmol) of 1a dissolved in 20 mL of anhydrous
CH2Cl2 underinert atmosphere(Ar), 0.2658g(1.14 mmol)of Ag2Owas
added, and the resulting mixturewas vigorouslystirred inthe dark for
24 h. The excess of Ag2O was eventually removed by filtration on
a millipore filter and the resulting clear solution concentrated under
vacuum to small volume. Addition of diethyl ether yields the precip-
itation of a sticky solid which was separated by decantation, washed
with some portions of diethyl ether and dried under high vacuum.
0.5125 g of the title complex was obtained as white solid (yield 75%).
Pd1eC1
Pd1eC2
Pd1eC3
Pd1eC4
Pd1eC15
C1eC2
C2eC3
C4eN1
C4eN2
C15eN3
C15eN4
Angles
C1ePd1eC4
C2ePd1eC4
C3ePd1eC4
C1ePd1eC15
C2ePd1eC15
C3ePd1eC15
C4ePd1eC15
C1ePd1eC2
C1ePd1eC3
C2ePd1eC3
Dihedral angle
Pd1,C1,C3,C4,C15 ˇ C1,C2,C3
2.211(11)
2.162(6)
2.133(12)
2.022(11)
2.070(9)
1.354(17)
1.434(18)
1.348(14)
1.387(12)
1.366(11)
1.317(14)
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 2.13 (s, 3H, S-CH3), 3.88 (s,
3H, N-CH3), 5.16 (s, 2H, CH2S), 7.05 (d, J ¼ 1.8 Hz, 1H, CH]CH Im),
168.6(4)
133.3(4)
101.1(5)
96.9(4)
127.5(4)
164.3(5)
94.5(1)
36.0(4)
67.6(3)
39.0(5)
7.25 (d, J ¼ 1.8 Hz, 1H, CH]CH Im). 13C {1H} NMR (CDCl3, T ¼ 298 K,
ppm) d: 14.4 (CH3, S-CH3), 38.9 (CH3, N-CH3), 54.7 (CH2, SCH2),
120.4 (CH, CH]CH Im), 123.0 (CH, CH]CH Im), 181.8 (C, NCN).
The following complexes were synthesized by
procedure.
a
similar
4.4.2. AgBr(Ndi-i-propylphenyl,NCH2SMe-NHC) (2c)
White solid. Yield 64%.
i
1H NMR (CDCl3, T ¼ 298 K, ppm)
d
: 1.15 (d, J ¼ 6.8 Hz, 6H, Pr-
68.2(7)
CH3), 1.25 (d, J ¼ 6.8 Hz, 6H, iPr-CH3), 2.17 (s, 3H, S-CH3), 2.38 (sept,

L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
35
i
2H, J ¼ 6.8 Hz, Pr-CH), 5.29 (s, 2H, CH2S), 7.09 (d, J ¼ 1.7 Hz, 1H,
CH]CH Im), 7.09 (d, J ¼ 7.7 Hz, 2H, m-aryl-H), 7.47 (d, J ¼ 1.7 Hz,1H,
CH]CH Im), 7.50 (t, J ¼ 7.7 Hz, 2H, p-aryl-H). 13C {1H} NMR (CDCl3,
4.6. Synthesis of the palladium allyl carbene complexes (4)
4.6.1. [Pd(h
3-allyl)(NMe,NCH2SMe-NHC)]ClO4 (4a)
T ¼ 298 K, ppm)
d
: 14.1 (CH3, S-CH3), 24.1 (CH3, iPr-CH3), 24.5 (CH3,
To 0.0255 g (0.069 mmol) of [Pd(
3-allyl)Cl]2 dissolved in
h
iPr-CH3), 28.3 (CH, iPr-CH), 54.7 (CH2, SCH2),120.0 (CH, CH]CH Im),
124.3 (CH, m-aryl-CH); 125.0 (CH, CH]CH Im), 130.6 (CH, p-aryl-
CH); 134.3 (C, i-aryl-C); 145.5 (C, o-aryl-C); 183.5 (d, JAgC ¼ 271 Hz,
C, NCN).
anhydrous CH2Cl2 (20 mL) under inert atmosphere (Ar), 0.0452
(0.137 mmol) of the silver complex 2a was added. Precipitation of
AgBr as a cloudy suspension was immediately noticed and after 1 h
the reaction mixture was filtered off on a millipore filter. The clear
solution was treated with 0.0392 g (0.279 mmol) of mono-
hydrated NaClO4 dissolved in MeOH (7 mL). The reaction mixture
was stirred for 30 min and the solvent removed by a rotary
evaporator. The residue was treated with anhydrous CH2Cl2
(10 mL) and the NaCl filtered off. The resulting clear solution was
reduced to small volume and the title product was precipitated by
addition of diethyl ether, filtered off and dried under high vacuum.
0.0394 g (yield 84%) of the title complex as white solid was
obtained.
4.4.3. AgBr(NMe,NCH2Ph-NHC) (2f)
White solid. Yield 91%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 3.86 (s, 3H, N-CH3), 5.30 (s,
2H, CH2N), 6.94 (d, J ¼ 1.8 Hz, 1H, CH]CH Im), 6.99 (d, J ¼ 1.8 Hz,
1H, CH]CH Im), 7.24e7.28 (m, 2H, aryl-H), 7.32e7.39 (m, 3H, aryl-
H). 13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 38.8 (CH3, N-CH3), 55.6
(CH2, Ph-CH2), 121.0 (CH, CH]CH Im), 122.5 (CH, CH]CH Im), 127.7
(CH, m-Ph); 129.1 (CH, o-Ph); 129.4 (CH, p-Ph); 135.3 (C, i-Ph); 181.2
(C, NCN).
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 2.64 (s, 3H, S-CH3), 3.29 (bd,
2H, anti allyl-H trans-S, anti allyl-H trans-C), 3.88 (s, 3H, N-CH3),
4.54 (bd, 1H, syn allyl-H trans-S), 4.59 (bd, 1H, syn allyl-H trans-C),
5.32 (broad AB system, 2H, CH2S), 5.52 (m, 1H, central-allyl-H), 7.16
(d, J ¼ 1.8 Hz, 1H, CH]CH Im). 7.59 (d, J ¼ 1.8 Hz, 1H, CH]CH Im).
4.4.4. AgBr(NMe,NCH2Tol-NHC) (2g)
White solid. Yield 88%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 2.35 (s, 3H, tolyl-CH3), 3.86 (s,
3H, N-CH3), 5.24 (s, 2H, CH2N), 6.92 (d, J ¼ 1.8 Hz, 1H, CH]CH Im),
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 20.9 (CH3, S-CH3), 39.5
6.97 (d, J ¼ 1.8 Hz, 1H, CH]CH Im), 7.15 (m, 4H, aryl-H). 13C {1H}
(CH3, N-CH3), 55.7 (CH2, SCH2), 58.7 (CH2, allyl trans-S), 69.3 (CH2,
allyl trans-C), 118.9 (CH, central allyl), 120.9 (CH, CH]CH Im), 123.8
(CH, CH]CH Im), 179.3 (C, NCN).
NMR (CDCl3, T ¼ 298 K, ppm)
d: 21.1(CH3, Ph-CH3), 38.7 (CH3, N-
CH3), 55.4 (CH2, Ph-CH2), 120.9 (CH, CH]CH Im), 122.4 (CH, CH]
CH Im), 127.8 (CH, m-Ph); 129.7 (CH, o-Ph); 132.3 (C, i-Ph); 145.5 (C,
p-Ph); 181.5 (C, NCN).
IR (KBr pellet, cmꢁ1): 1092 (ClO stretching), 623 (ClO bending).
Anal. Calcd. for C9H15ClN2O4PdS: C, 27.78; H, 3.89; N, 7.20.
Found: C, 27.91; H, 3.77; N, 7.27%.
4.5. Synthesis of the palladium allyl carbene complexes (3)
The following complexes were synthesized by
procedure.
a similar
4.5.1. [Pd(
h
3-allyl)(NMe,NCH2SMe-NHC)Cl] (3a)
3-allyl)Cl]2 [27] dissolved in
To 0.0389 g (0.105 mmol) of [Pd(
h
4.6.2. [Pd(h
3-allyl)(NMesityl,NCH2SMe-NHC)]ClO4 (4b)
20 mL of anhydrous CH2Cl2, 0.0692 g (0.21 mmol) of complex 2a
was added under inert atmosphere (Ar). The reaction mixture was
stirred for 1 h and the AgBr filtered off on a millipore filter. The clear
solution was concentrated under vacuum. Addition of diethyl ether
yields the precipitation of 0.0273 g (yield 40%) of the title com-
pounds as a whitish sticky solid which was washed several times
with diethyl ether.
White solid. Yield 72%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 1.93 (s, 3H, o-aryl-CH3),
2.02 (s, 3H, o-aryl-CH3), 2.40 (s, 3H, p-aryl-CH3), 2.48 (d, J ¼ 13.6,
1H, anti allyl-H trans-S), 2.72 (s, 3H, S-CH3), 2.93 (d, J ¼ 6.8 Hz, 1H,
syn allyl-H trans-S), 3.08 (d, J ¼ 13.8 Hz, 1H, anti allyl-H trans-C),
4.43 (dd, J ¼ 7.7, 2.1 Hz, 1H, syn allyl-H trans-C), 5.21 (m, 1H,
central-allyl-H), 5.57 (broad AB system, 2H, CH2S), 7.04 (s, 2H, m-
aryl-H), 7.08 (d, J ¼ 1.9 Hz, 1H, CH]CH Im), 7.88 (d, J ¼ 1.9 Hz, 1H,
CH]CH Im).
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 2.15 (s, 3H, S-CH3), 2.52 (bd,
1H, anti allyl-H trans-Cl), 3.34 (d, J ¼ 14.0 Hz, 1H, anti allyl-H trans-
C), 3.51 (bs, 1H, syn allyl-H trans-Cl), 3.84 (s, 3H, N-CH3), 4.36 (d,
J ¼ 7.4 Hz, 1H, syn allyl-H trans-C), 5.29 (bs 2H, CH2S), 5.37 (bm, 1H,
central-allyl-H), 6.98 (bd,1H, CH]CH Im). 7.24 (bd,1H, CH]CH Im).
The following complexes were synthesized similarly.
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 17.6 (CH3, o-mesityl-
CH3), 21.1 (CH3, p-mesityl-CH3), 21.3 (CH3, S-CH3), 56.3 (CH2, SCH2),
59.2 (CH2, allyl trans-S), 68.3 (CH2, allyl trans-C), 119.0 (CH, central
allyl), 121.7 (CH, CH]CH Im), 123.3 (CH, CH]CH Im), 129.0 (CH, m-
mesityl-CH); 129.1 (CH, m-mesityl-CH); 134.7 (C, o-mesityl-C);
135.0 (C, o-mesityl-C); 136.6 (C, i-mesityl-C); 139.9 (C, p-mesityl-C);
180.5 (C, NCN).
4.5.2. [Pd(h
3-allyl)(NMe,NCH2SPh-NHC)Cl] (3f)
Whitish solid. Yield 88%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d
: 2.21 (d, J ¼ 12.3 Hz, 1H, anti
IR (KBr pellet, cmꢁ1): 1102 (ClO stretching), 623 (ClO bending).
Anal. Calcd. for C17H23ClN2O4PdS: C, 41.39; H, 4.70; N, 5.68.
Found: C, 41.51; H, 4.61; N, 5.76%.
allyl-H trans-Cl), 3.22e3.26 (m, 2H, anti allyl-H trans-C, syn allyl-H
trans-Cl), 3.85 (s, 3H, N-CH3), 4.28 (dd, J ¼ 7.6, 2.2 Hz, 1H, syn allyl-H
trans-C), 5.23 (bm, 1H, central-allyl-H), 5.44 (broad AB system, 2H,
CH2S), 6.89 (d, J ¼ 1.9 Hz, 1H, CH]CH Im), 6.94 (d, J ¼ 1.9 Hz, 1H,
CH]CH Im), 7.25e7.37 (m, 5H, SPh).
4.6.3. [Pd(h
3-allyl)(Ndi-i-propylphenyl,NCH2SMe-NHC)]ClO4 (4c)
White solid. Yield 90%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d
: 1.07 (d, J ¼ 6.8 Hz, 3H, Pr-
i
4.5.3. [Pd(
h
3-allyl)(NMe,NCH2Tol-NHC)Cl] (3g)
CH3), 1.15 (d, J ¼ 6.8 Hz, 3H, iPr-CH3), 1.18 (d, J ¼ 6.8 Hz, 6H, iPr-CH3),
i
Whitish solid. Yield 77%.
2.27 (sept, 1H, J ¼ 6.8 Hz, Pr-CH), 2.44 (d, J ¼ 13.9, 1H, anti allyl-H
1H NMR (CDCl3, T ¼ 298 K, ppm)
d
: 2.25 (d, J ¼ 12.5 Hz, 1H, anti
trans-S), 2.48 (sept, 1H, J ¼ 6.8 Hz, iPr-CH), 2.69 (s, 3H, S-CH3), 2.75
(bd, J ¼ 6.4 Hz, 1H, syn allyl-H trans-S), 3.04 (d, J ¼ 13.7 Hz, 1H, anti
allyl-H trans-C), 4.41 (dd, J ¼ 7.5, 2.3 Hz,1H, syn allyl-H trans-C), 5.12
(m, 1H, central-allyl-H), 5.63 (bs, 2H, CH2S), 7.16 (d, J ¼ 1.9 Hz, 1H,
CH]CH Im), 7.32 (d, J ¼ 8.1 Hz, 1H, m-aryl-H), 7.33 (d, J ¼ 8.1 Hz, 1H,
m-aryl-H), 7.56 (t, J ¼ 8.1 Hz, 1H, p-aryl-H), 7.94 (d, J ¼ 1.9 Hz, 1H,
CH]CH Im).
allyl-H trans-Cl), 2.34 (s, 3H, tolyl-CH3), 3.26e3.28 (m, 2H, anti allyl-
H trans-C and syn allyl-H trans-Cl), 3.85 (s, 3H, N-CH3), 4.30 (d,
J ¼ 7.7 Hz, J ¼ 2.2 Hz, 1H, anti allyl-H trans-C), 5.26 (bm, 1H, central
allyl-H), 5.35, 5.43 (AB system, J ¼ 15.0 Hz, 2H, CH2N), 6.86 (d,
J ¼ 1.9 Hz, 1H, CH]CH Im), 6.92 (d, J ¼ 1.9 Hz, 1H, CH]CH Im), 7.16
(m, 4H, tolyl-H).

36
L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d
: 21.2 (CH3, S-CH3), 23.4
129.1 (CH, m-mesityl-CH);134.7 (C, o-mesityl-C); 134.9 (C, o-mesityl-
C); 136.7(C, i-mesityl-C); 139.8 (C, p-mesityl-C); 189.9 (C, NCN).
IR (KBr pellet, cmꢁ1): 1089 (ClO stretching), 623 (ClO bending).
i
i
i
(CH3, Pr-CH3), 23.7 (CH3, Pr-CH3), 24.3 (CH3, Pr-CH3), 24.7 (CH3,
i
i
iPr-CH3), 28.2 (CH, Pr-CH), 28.3 (CH3, Pr-CH3), 56.3 (CH2, SCH2),
60.5 (CH2, allyl trans-S), 68.0 (CH2, allyl trans-C), 118.8 (CH, central
allyl), 121.6 (CH, CH]CH Im), 123.9 (CH, m-aryl-CH); 124.0 (CH, m-
aryl-CH); 124.5 (CH, CH]CH Im), 130.7 (CH, p-aryl-CH); 136.4 (C, i-
aryl-C); 145.6 (C, o-aryl-C); 145.7 (C, o-aryl-C); 181.3 (C, NCN).
IR (KBr pellet, cmꢁ1): 1089 (ClO stretching), 623 (ClO bending).
Anal. Calcd. for C20H29ClN2O4PdS: C, 44.87; H, 5.46; N, 5.23.
Found: C, 44.94; H, 5.37; N, 5.14%.
4.7.3. [Pd(h
3-1,1-Me2allyl)(Ndi-i-propylphenyl,NCH2SMe-NHC)]
ClO4 (5c)
White solid. Yield 61%.
i
1H NMR (CDCl3, T ¼ 298 K, ppm)
d
: 1.11 (d, J ¼ 6.9 Hz, 3H, Pr-
CH3), 1.15 (d, J ¼ 6.9 Hz, 3H, iPr-CH3), 1.17 (d, J ¼ 6.9 Hz, 3H, iPr-CH3),
1.19 (d, J ¼ 6.9 Hz, 3H, iPr-CH3), 2.23e2.34 (m, 2H, anti allyl-H and
iPr-CH), 2.48 (sept, 1H, J ¼ 6.9 Hz, iPr-CH), 2.58 (s, 3H, S-CH3), 2.58
(bd, partially obscured,1H, syn allyl-H), 5.12 (dd, J ¼ 13.4, 7.7 Hz, 1H,
central-allyl-H), 5.57 (bs, 2H, CH2S), 7.13 (d, J ¼ 1.9 Hz, 1H, CH]CH
Im), 7.32 (d, J ¼ 7.8 Hz, 2H, m-aryl-H), 7.56 (t, J ¼ 7.8 Hz, 1H, p-aryl-
H), 7.92 (d, J ¼ 1.9 Hz, 1H, CH]CH Im).
4.6.4. [Pd(h
3-allyl)(NMe,NCH2SPh-NHC)]ClO4 (4d)
White solid. Yield 87%.
1H NMR (CD2Cl2, T ¼ 298 K, ppm)
: 3.33 (d, J ¼ 13.6 Hz, 1H, anti
d
allyl-H trans-C), 3.43 (d, J ¼ 12.5 Hz, 1H, anti allyl-H trans-S), 3.93 (s,
3H, NCH3), 4.62 (dd, J ¼ 7.6, J ¼ 2.2, 1H, syn allyl-H trans-S), 4.73 (dt,
J ¼ 7.0, 1.9 Hz, 1H, syn allyl-H trans-C), 5.33, 5.43 (AB system,
J ¼ 12.9 Hz, 2H, CH2S), 5.62 (m, 1H, central-allyl-H), 7.23 (d,
J ¼ 1.9 Hz, 1H, CH]CH Im), 7.46 (d, J ¼ 1.9 Hz, 1H, CH]CH Im),
7.43e751 (m, 3H, SPh-H), 7.57e7.61 (m, 2H, SPh-H).
13C{1H} NMR(CDCl3,T¼298K, ppm)
d:20.1 (CH3,S-CH3), 20.1 (CH3,
i
i
S-CH3), 21.0 (CH3, anti allyl-CH3), 23.4 (CH3, Pr-CH3), 23.6 (CH3, Pr-
CH3), 24.4 (CH3, iPr-CH3), 24.6 (CH3, iPr-CH3), 21.0 (CH3, syn allyl-CH3),
28.2 (CH, iPr-CH), 28.3 (CH3, iPr-CH3), 52.3 (CH2, allyl), 55.6 (CH2, SCH2),
102.7 (C. allyl), 110.4 (CH, central-allyl), 121.9 (CH, CH]CH Im), 123.9
(CH, m-aryl-CH); 124.0 (CH, m-aryl-CH); 124.4 (CH, CH]CH Im), 130.6
(CH, p-aryl-CH); 136.6 (C, i-aryl-C); 145.5 (C, o-aryl-C); 180.8 (C, NCN).
IR (KBr pellet, cmꢁ1): 1086 (ClO stretching), 621 (ClO bending).
13C {1H} NMR (CD2Cl2, T ¼ 298 K, ppm)
d: 39.6 (CH3, CH3-Im),
59.4 (CH2, CH2-SPh), 59.8 (CH2 allyl trans-S), 70.6 (CH2 allyl trans-C),
119.4 (CH allyl), 120.0 (CH, CH]CH Im), 124.3 (CH, CH]CH Im),
129.7 (C, i-Ph), 130.1 (C, o-Ph), 131.0 (C, p-Ph), 132.1 (C, m-Ph), 179.2
(C, Im).
4.7.4. [Pd(h
3-1,1-Me2allyl)(NMe,NCH2SPh-NHC)]ClO4 (5d)
IR (KBr pellet, cmꢁ1): 1082 (ClO stretching), 623 (ClO bending).
Anal. Calcd. for C14H17ClN2O4PdS: C, 37.26; H, 3.80; N, 6.21.
Found: C, 37.37; H, 3.69; N, 6.12%.
White solid. Yield 80%.
1H NMR (CD2Cl2, T ¼ 298 K, ppm)
d: 1.24 (s, 3H, anti allyl-CH3),
1.89 (s, 3H, syn allyl-CH3), 3.32 (dd, J ¼ 12.9, 2.2 Hz, 1H, anti allyl-H),
3.93 (s, 3H, NCH3), 4.28 (dd, J ¼ 7.5, 2.4 Hz, 1H, syn allyl-H), 5.20 (dd,
J ¼ 12.9, 7.5 Hz, 1H, central-allyl-H), 5.42, 5.47 (AB system,
J ¼ 13.4 Hz, 2H, CH2S), 7.26 (d, J ¼ 1.9 Hz, 1H, CH]CH Im), 7.46 (d,
J ¼ 1.9 Hz, 1H, CH]CH Im), 7.44e7.56 (m, 5H, SPh-H).
4.6.5. [Pd(h
3-allyl)(NMe,NCH2Py-NHC)]ClO4 (4e) was synthesized
according to a published procedure [8c]
The synthesis of the following complexes is similar to that of the
unsubstituted allyl derivative and was carried out starting from
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 20.8 (CH3 anti allyl-
[Pd(
h
3-1,1-Me2allyl)(
m-Cl)]2 [28].
CH3), 27.2 (CH3 syn allyl-CH3), 39.7 (CH3 CH3-NHC), 51.4 (CH2 allyl),
58.8 (CH2, CH2-SPh), 105.8 (C allyl), 110.3 (CH allyl), 120.8 (CH, CH]
CH Im), 124.2 (CH, CH]CH Im), 129.6 (C, i-Ph), 130.3 (C, o-Ph), 131.0
(C, p-Ph), 131.7 (C, m-Ph), 178.4 (C, NHC).
4.7. Synthesis of the palladium Me-allyl carbene complexes (5)
3-1,1-Me2allyl)(NMe,NCH2SMe-NHC)]ClO4 (5a)
4.7.1. [Pd(
h
IR (KBr pellet, cmꢁ1): 1085 (ClO stretching), 625 (ClO bending).
Whitish solid. Yield 69%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d
: 1.47 (s, 3H, CH3 anti allyl-
4.7.5. [Pd(h
3-1,1-Me2allyl)(NMe,NCH2Py-NHC)]ClO4 (5e)
CH3); 2.04 (s, 3H, CH3 syn allyl-CH3); 2.53 (s, 3H, S-CH3), 3.16 (dd,
J ¼ 12.7, 2.1 Hz,1H, anti allyl-H), 3.87 (s, 3H, N-CH3), 4.59 (dd, J ¼ 7.6,
2.1 Hz, 1H, syn allyl-H), 5.14 (dd, J ¼ 12.7, 7.6 Hz, 1H, central-allyl-H),
5.28 (broad AB system, 2H, CH2S), 7.17 (d, J ¼ 1.8 Hz, 1H, CH]CH
Im), 7.56 (d, J ¼ 1.8 Hz, 1H, CH]CH Im). 13C {1H} NMR (CDCl3,
White solid. Yield 91%.
1H NMR (CD2Cl2, T ¼ 298 K, ppm)
d: 1.54 (s, 3H, anti allyl-CH3),
1.79 (s, 3H, syn allyl-CH3), 2.86 (dd, J ¼ 12.4, 2.8 Hz, 1H, anti allyl-H),
3.65 (dd, J ¼ 7.4, 2.8 Hz, 1H, syn allyl-H), 3.80 (s, 3H, NCH3), 5.71 (dd,
J ¼ 12.4, 7.4 Hz, 1H, central-allyl-H), 5.30, 5.40 (AB system,
J ¼ 14.9 Hz, 2H, CH2N), 7.05 (d, J ¼ 1.9 Hz, 1H, CH]CH Im), 7.46 (d,
J ¼ 1.9 Hz, 1H, CH]CH Im), 7.58 (ddd, J ¼ 7.7, 4.5, 1.4 Hz, 1H, 5-Pyr),
7.89 (d, J ¼ 7.7 Hz, 1H, 3-Pyr), 8.04 (td, 1H, J ¼ 7.7, 1.7 Hz, 4-Pyr), 8.52
(d, 1H, J ¼ 4.5 Hz, 6-Pyr).
T ¼ 298 K, ppm)
d: 20.0 (CH3, syn allyl-CH3), 21.1 (CH3, anti allyl-
CH3), 27.4 (CH3, S-CH3), 39.6 (CH3, N-CH3), 50.4 (CH2, allyl trans-S),
55.0 (CH2, SCH2), 104.2 (C, allyl), 110.2 (CH, central allyl), 121.3 (CH,
CH]CH Im), 123.6 (CH, CH]CH Im), 178.4 (C, NCN).
IR (KBr pellet, cmꢁ1): 1091 (ClO stretching), 623 (ClO bending).
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 20.6 (CH3 anti allyl-
CH3), 25.7 (CH3 syn allyl-CH3), 38.1 (CH3 CH3-Im), 40.0 (CH2 allyl),
54.6 (CH2 CH2-Py), 104.2 (C allyl), 109.7 (CH allyl), 121.7 (CH, CH]
CH Im), 123.6 (CH, CH]CH Im), 125.4 (CH 5-Py), 127.0 (CH 3-Py),
140.2 (CH 4-Py), 150.3 (CH 6-Py), 154.0 (C 2-Py), 175.2 (C, Im).
IR (KBr pellet, cmꢁ1): 1093 (ClO stretching), 622 (ClO bending).
4.7.2. [Pd(h
3-1,1-Me2allyl)(NMesityl,NCH2SMe-NHC)]ClO4 (5b)
Whitish solid. Yield 79%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 1.35 (s, 3H, CH3 anti allyl-
CH3), 1.94 (s, 3H, o-aryl-CH3), 1.97 (s, 3H, CH3 syn allyl-CH3); 2.02 (s,
3H, o-aryl-CH3), 2.29 (dd, J ¼ 13.2, 3.1 Hz, 1H, anti allyl-H), 2.40 (s,
3H, p-aryl-CH3), 2.60 (s, 3H, S-CH3), 2.67 (dd, J ¼ 7.4, 3.2 Hz, 1H, syn
allyl), 4.87 (dd, J ¼ 13.2, 7.4 Hz 1H, central-allyl-H), 5.53 (broad AB
system, 2H, CH2S), 7.03 (s, 2H, m-aryl-H), 7.06 (d, J ¼ 1.9 Hz, 1H,
CH]CH Im), 7.87 (d, J ¼ 1.9 Hz, 1H, CH]CH Im).
4.8. Synthesis of the palladium allyl bis-carbene complexes (6)
4.8.1. [Pd(
To a solution of 0.0528 g (0.155 mmol) of the complex [Pd(h3
h
3-allyl)(NMe,NCH2SMe-NHC)2]ClO4 (6a)
-
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 17.5 (CH3, o-mesityl-CH3),
allyl)(NMe,NCH2SMe-NHC)]ClO4 (4a) in 10 mL of anhydrous
CH2Cl2, 0.051 g (0.155 mmol) of AgBr(NMe,NCH2SMe-NHC) (2a)
dissolved in 10 mL of CH2Cl2 was added under inert atmosphere
(Ar). The reaction mixture was stirred for 1 h and the precipitated
AgBr filtered off on a millipore filter. The resulting solution was
17.6 (CH3, o-mesityl-CH3), 20.1 (CH3, S-CH3), 20.7 (CH3, anti allyl-
CH3), 21.1 (CH3, p-mesityl-CH3), 27.3 (CH3, syn allyl-CH3), 50.7 (CH2,
allyl), 55.6 (CH2, SCH2), 102.9 (C, allyl), 110.6 (CH, central allyl), 122.1
(CH, CH]CH Im), 123.2 (CH, CH]CH Im), 129.0 (CH, m-mesityl-CH);

L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
37
concentrated under vacuum and addition of diethyl ether yielded
the precipitation of 0.0682 g (yield 85%) of the title complex as
a light brown solid. The complex was filtered off on a Gooch,
washed with diethyl ether and dried under high vacuum.
CH Im, Ph-H), 6.87 (d, J ¼ 1.9 Hz, 2H, CH]CH Im), 7.28e7.32 (m, 6H,
Ph-H). 13C {1H} NMR (CDCl3, T ¼ 298 K, ppm). 13C {1H} NMR (CDCl3,
T ¼ 298 K, ppm)
d: 38.1 (CH3, N-CH3), 54.0 (CH2, Ph-CH2), 60.1 (CH2,
CH2-allyl), 119.1 (CH, CH-allyl), 122.2 (CH, CH]CH Im), 123.9 (CH,
CH]CH Im), 126.4 (CH, m-Ph); 128.0 (CH, p-Ph); 128.8 (CH, o-Ph);
135.7 (C, i-Ph); 176.8 (C, NCN).
Anal. Calcd. for C25H29BF4N4 Pd: C, 51.88; H, 5.05; N, 9.68. Found:
C, 51.79; H, 4.95; N, 9.46%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 2.03 (s, 6H, S-CH3), 2.80 (d,
J ¼ 13.4 Hz, 2H, anti allyl-H), 3.76 (s, 6H, N-CH3), 3.98 (d, J ¼ 6.4 Hz,
2H, syn allyl-H), 4.92 (s, 4H, CH2S), 5.44 (m, 1H, central-allyl-H), 7.16
(d, J ¼ 1.9 Hz, 2H, CH]CH Im), 7.32 (d, J ¼ 1.9 Hz, 2H, CH]CH Im).
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d
: 14.4 (CH3, S-CH3), 38.5
The following complex was synthesized by a similar procedure.
(CH3, N-CH3), 53.8 (CH2, SCH2), 60.2 (CH2, allyl), 119.1 (CH, central
allyl), 122.2 (CH, CH]CH Im), 123.6 (CH, CH]CH Im), 176.9 (C,
NCN).
4.8.5. [Pd(h
3-allyl)(NMe,NCH2Tol-NHC)2]BF4 (6g)
Whitish solid. Yield 89%.
IR (KBr pellet, cmꢁ1): 1092 (ClO stretching), 623 (ClO bending).
Anal. Calcd. for C15H25ClN4O4PdS2: C, 33.90; H, 4.74; N, 10.54.
Found: C, 33.79; H, 4.63; N, 10.42%.
1H NMR (CDCl3, T ¼ 298 K, ppm)
d: 2.29 (s, 6H, tolyl-CH3), 2.62
(d, J ¼ 13.3 Hz, 2H, anti allyl-H), 3.67 (s, 6H, N-CH3), 3.87 (d,
J ¼ 7.3 Hz, 2H, syn allyl-H), 5.04 (s, 4H, CH2N), 5.26 (m, 1H, central
allyl-H), 6.79 (d, J ¼ 7.9 Hz, 2H, tolyl-H), 6.87 (d, J ¼ 1.8 Hz, 2H,
CH]CH Im), 7.06e7.10 (m, 6H, CH]CH Im, tolyl-H). 13C {1H} NMR
The following complexes were synthesized by a similar proce-
dure using the appropriate complexes.
(CDCl3, T ¼ 298 K, ppm)
d: 21.0(CH3, Ph-CH3), 38.1 (CH3, N-CH3),
4.8.2. [Pd(
h
3-allyl)(NMe,NCH2SPh-NHC)2]ClO4 (6d)
53.9 (CH2, Ph-CH2), 60.0 (CH2, CH2-allyl), 119.1 (CH, CH-allyl),
122.1 (CH, CH]CH Im), 123.9 (CH, CH]CH Im), 126.5 (CH, m-
Ph); 129.5 (CH, o-Ph); 132.6 (C, i-Ph); 137.9 (C, p-Ph); 176.4
(C, NCN).
Whitish solid. Yield 91%.
1H NMR (CD2Cl2, T ¼ 298 K, ppm)
: 2.59 (d, J ¼ 13.2 Hz, 2H, anti
d
allyl-H), 3.70 (s, 6H, NCH3), 3.78 (d, J ¼ 7.5 Hz, 2H, syn allyl-H), 5.16
(s, 4H, CH2S), 5.22 (m, 1H, central-allyl-H), 7.00 (d, J ¼ 1.9 Hz, 2H,
CH]CH Im), 7.10 (d, J ¼ 1.9 Hz, 2H, CH]CH Im), 7.43e7.44 (m, 10H,
SPh-H).
Anal. Calcd. for C27H33BF4N4Pd: C, 53.44; H, 5.48; N, 9.23. Found:
C, 53.37; H, 5.36; N, 9.03%.
The complexes 7, 8 and 9 cannot be separated in their pure form
and were identified in solution from their relevant 1H NMR signals
among the well-known peaks belonging to the symmetric bis-car-
bene complexes concurring to their formation.
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 38.5 (CH3 CH3-Im), 55.9
(CH2 CH2-SPh), 60.3 (CH2 allyl), 119.2 (CH allyl), 121.9 (CH, CH]CH
Im), 123.6 (CH, CH]CH Im),128.9 (C, p-Ph),129.5 (C, o-Ph),132.0 (C,
i-Ph), 133.2 (C, m-Ph), 176.8 (C, Im).
IR (KBr pellet, cmꢁ1): 1093 (ClO stretching), 622 (ClO bending).
Anal. Calcd. for C25H29ClN4O4PdS2: C, 45.81; H, 4.46; N, 8.55.
Found: C, 45.72; H, 4.35; N, 8.63%.
4.8.6. [Pd(h
3-allyl)(NMe,NCH2SMe-NHC)(NMe,NCH2Py-NHC)]þ (7)
1H NMR (CD2Cl3, T ¼ 298 K, ppm)
d: 2.01 (s, 3H, S-CH3), 2.66 (d,
J ¼ 12.4 Hz, 1H, anti allyl-H), 2.74 (d, J ¼ 13.6 Hz, 1H, anti allyl-H),
3.65 (s, 3H, N-CH3),
d
: 3.78 (s, 3H, NCH3), 3.90 (d, J ¼ 7.0 Hz, 1H,
4.8.3. [Pd(
h
3-allyl)(NMe,NCH2Py-NHC)2]ClO4 (6e)
syn allyl-H), 3.95 (d, J ¼ 7.5 Hz, 1H, syn allyl-H), 4.88 (s, 2H, CH2S),
5.28 (s, 2H, CH2N), 6.86 (d, J ¼ 7.0 Hz, 1H, 3-Pyr), 6.98 (d, J ¼ 1.7 Hz,
1H, CH]CH Im), 7.05 (dd, J ¼ 7.7, 4.1 Hz, 1H, 5-Pyr), 7.17 (d,
J ¼ 1.9 Hz, 1H, CH]CH Im), 7.21 (d, J ¼ 2.1 Hz, 1H, CH]CH Im), 7.67
(td, 1H, J ¼ 7.6, 1.6 Hz, 4-Pyr), 8.52 (d, 1H, J ¼ 5.2 Hz, 6-Pyr).
Whitish solid. Yield 89%.
1H NMR (CD2Cl2, T ¼ 298 K, ppm)
: 2.55 (d, J ¼ 13.2 Hz, 2H, anti
d
allyl-H), 3.67 (s, 6H, NCH3), 3.80 (d, J ¼ 6.8 Hz, 2H, syn allyl-H), 5.21
(m, 1H, central-allyl-H), 5.25 (s, 4H, CH2N), 6.88 (d, J ¼ 7.7 Hz, 2H, 3-
Pyr); 7.04 (d, J ¼ 1.9 Hz, 2H, CH]CH Im), 7.07 (d, J ¼ 1.9 Hz, 2H, CH]
CH Im), 7.05 (dd, J ¼ 7.7, 4.1 Hz, 2H, 5-Pyr), 7.65 (td, 2H, J ¼ 7.6,
1.7 Hz, 4-Pyr), 8.50 (d, 2H, J ¼ 4.1 Hz, 6-Pyr).
4.8.7. [Pd(h
3-allyl)( NMe,NCH2SMe-NHC)(NMe,NCH2Ph-NHC)]þ (8)
1H NMR (CD2Cl2, T ¼ 298 K, ppm)
d: 2.03 (s, 3H, S-CH3), 2.73 (d,
13C {1H} NMR (CDCl3, T ¼ 298 K, ppm)
d: 38.2 (CH3 CH3-Im), 55.7
J ¼ 13.4 Hz, 1H, anti allyl-H), 2.76 (d, J ¼ 13.6 Hz, 1H, anti allyl-H),
3.62 (s, 3H, N-CH3), 3.79 (s, 3H, N-CH3), 3.98 (d, J ¼ 7.2 Hz, 2H,
syn allyl-H), 4.85 (s, 2H, CH2S), 5.21 (s, 2H, CH2N), 6.90e6.94 (m, 2H,
Ph-H), 7.02 (d, J ¼ 1.8 Hz, 1H, CH]CH Im), 7.03 (d, J ¼ 1.7 Hz, 1H,
CH]CH Im), 7.20 (d, J ¼ 1.9 Hz, 1H, CH]CH Im), 7.24 (d, J ¼ 1.9 Hz,
2H, CH]CH Im), 7.32e7.35 (m, 3H, Ph-H).
(CH2 CH2-Py), 60.0 (CH2 allyl), 119.0 (CH allyl), 121.3 (CH, CH]CH
Im), 122.6 (CH 5-Py), 122.8 (CH 3-Py), 123.6 (CH, CH]CH Im), 137.3
(CH 4-Py), 149.3 (CH 6-Py), 155.4 (C 2-Py), 177.3 (C, Im).
IR (KBr pellet, cmꢁ1
) n: 1593 (CN Py stretching), 1093 (ClO
stretching), 622 (ClO bending).
Anal. Calcd. for C23H27ClN6O4Pd: C, 46.56; H, 4.59; N, 14.16.
Found: C, 46.48; H, 4.70; N, 14.25%.
4.8.8. [Pd(h
3-allyl)( NMe,NCH2Ph-NHC)( NMe,NCH2Tol-NHC)]þ (9)
1H NMR (CD2Cl2, T ¼ 298 K, ppm)
d: 2.34 (s, 3H, tolyl-CH3), 2.66
4.8.4. [Pd(
h
3-allyl)(NMe,NCH2Ph-NHC)2]BF4 (6f)
(d, J ¼ 12.8 Hz, 2H, anti allyl-H), 3.68 (s, 3H, N-CH3), 3.70 (s, 3H, N-
CH3), 3.89e3.96 (m, 2H, syn allyl-H), 5.06 (s, 2H, CH2N), 5.12 (s, 2H,
CH2N), 5.26 (m, 1H, central allyl-H), 6.83 (d, J ¼ 7.2 Hz, tolyl-H),
6.90e6.98 (m, 2H, Ph-H), 7.07e7.17 (m, CH]CH Im), 7.30e7.37
(m, 3H, Ph-H).
To a solution of 0.1 g (0.28 mmol) of the complex [Pd(h3
-
allyl)(NMe,NCH2Ph-NHC)Cl] (3 h) in 8 mL of anhydrous CH2Cl2,
0.101 g (0.28 mmol) of AgBr(NMe,NCH2Ph-NHC) (2f) dissolved in
7 mL of anhydrous CH2Cl2 were added under inert atmosphere (Ar).
To the resulting solution 0.055 g (0.28 mmol) of AgBF4 were added
and the resulting mixture was vigorously stirred for 30 min and the
precipitated AgBr filtered off on a millipore filter. The clear solution
was concentrated under vacuum to the final volume of 2 mL and
treated with diethyl ether (10 mL). The precipitated oil was sepa-
rated by decantation and dried under vacuum. 0.155 g (yield 95%) of
the title complex was isolated as a whitish solid.
4.9. Crystal structure determinations
The crystal data of compounds 5b and 6d were collected at room
temperature using a Nonius Kappa CCD diffractometer with
graphite monochromated Mo-Ka radiation. The data sets were in-
tegrated with the Denzo-SMN package [29] and corrected for Lor-
entz, polarization and absorption effects (SORTAV) [30]. The
structures were solved by direct methods using SIR97 [31] system
of programs and refined using full-matrix least-squares with all
1H NMR (CDCl3, T ¼ 298 K, ppm)
: 2.64 (d, J ¼ 13.3 Hz, 2H, anti
d
allyl-H), 3.71 (s, 6H, N-CH3), 3.85 (d, J ¼ 7.4 Hz, 2H, syn allyl-H), 5.12
(s, 4H, CH2N), 5.27 (m, 1H, central allyl-H), 6.88e6.92 (m, 12H, CH]

38
L. Canovese et al. / Journal of Organometallic Chemistry 732 (2013) 27e39
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non-hydrogen atoms anisotropically and hydrogens included on
calculated positions, riding on their carrier atoms.
The asymmetric unit of 5b contains two independent ionic
couples with one cationic complex displaying a disordered 1,1-
dimethyl substituted allyl group whose central C2 atom and both
methyl groups were refined over two positions with occupancies of
0.73 and 0.27, respectively.
All calculations were performed using SHELXL-97 [32] and
PARST [33] implemented in WINGX [34] system of programs. The
crystal data are given in Table 1 SI.
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CCDC 894208 and 894209 contain the supplementary crys-
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charge from The Cambridge Crystallographic Data Centre via www.
ccdc.cam.ac.uk/data_request/cif.
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