(2,2-Dibromovinyl)ferrocene as a building block for the assembly of heterodinuclear complexes - Preparation of an σ-alkenylpalladium complex and dimetallic dithioether complexes

Article abstract of DOI:10.1002/ejic.200700470

The oxidative addition of (2,2-dibromovinyl)ferrocene [Br ₂C=C(H)-Fc] (1) to [Pd(PPh₃)₄] yields the heterodinuclear σ-alkenyl complex trans-[{Pd(Br)(PPh₃) ₂}-C(Br)=C(H)-Fc] (2). Nucleophilic attack of sodium thiolates on 1 unexpectedly affords the vinyl thioether derivatives (Z)-[(RS)(H)C=C(H)-Fc] (4a: R = Ph; 4b: R = tBu; 4c: R = Et). Complexes 4a and 4c can also be prepared by addition of NaSR across the triple bond of Fc-C≡C-H (3). Addition of an excess of NaSR to 1 affords the dithioether derivatives (Z)-[(RS)(H)C=C(SR)-Fc] (5a: R = Ph; 5b: R = p-tolyl; 5c: R = Et). An addition/elimination sequence is suggested to account for this surprising result. The yield of 5c is very low due to a competing formation of ethynylferrocene (3). Reaction of 5b with [Re(thf)(CO)₃(μ-Br)]₂ and [PtCl₂(PhCN) ₂] leads to the heterodinuclear chelate complexes [Fc{C(S-p-tolyl)=C(H)(S-p-tolyl)}Re(Br)(CO)₃] (6) and [Fc{C(S-p-tolyl)=C(H)(S-p-tolyl)}PtCl₂] (7a), respectively. Metathesis of the fluxional compound 7a in the presence of NaI affords [Fc{C(S-p-tolyl)=C(H)(S-p-tolyl)}PtI₂] (7b). The electrochemical properties of some of these complexes have been studied by means of cyclic voltammetry, and the molecular structures of 1, 2, 3, 4b, 4c and 6 have been determined by X-ray diffraction. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700470

FULL PAPER
DOI: 10.1002/ejic.200700470
(2,2-Dibromovinyl)ferrocene as a Building Block for the Assembly of
Heterodinuclear Complexes – Preparation of an σ-Alkenylpalladium Complex
and Dimetallic Dithioether Complexes
Sébastien Clément,[a] Laurent Guyard,[a] Michael Knorr,*[a] Fernando Villafañe,[b]
Carsten Strohmann,[c] and Marek M. Kubicki[d]
Keywords: Oxidative addition / Thioether ligands / Platinum / Rhenium / Palladium / Electrochemistry
The oxidative addition of (2,2-dibromovinyl)ferrocene
[Br2C=C(H)–Fc] (1) to [Pd(PPh3)4] yields the heterodinuclear
σ-alkenyl complex trans-[{Pd(Br)(PPh3)2}–C(Br)=C(H)–Fc] (2).
Nucleophilic attack of sodium thiolates on 1 unexpectedly
affords the vinyl thioether derivatives (Z)-[(RS)(H)C=C(H)–
Fc] (4a: R = Ph; 4b: R = tBu; 4c: R = Et). Complexes 4a and
4c can also be prepared by addition of NaSR across the triple
bond of Fc–CϵC–H (3). Addition of an excess of NaSR to
1 affords the dithioether derivatives (Z)-[(RS)(H)C=C(SR)–Fc]
(5a: R = Ph; 5b: R = p-tolyl; 5c: R = Et). An addition/elimi-
nation sequence is suggested to account for this surprising
tion of ethynylferrocene (3). Reaction of 5b with [Re(thf)(CO)3-
(µ-Br)]2 and [PtCl2(PhCN)2] leads to the heterodinuclear che-
late
complexes
[Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}Re(Br)-
(CO)3] (6) and [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}PtCl2] (7a),
respectively. Metathesis of the fluxional compound 7a in the
presence of NaI affords [Fc{C(S–p-tolyl)=C(H)(S–p-tolyl)}PtI2]
(7b). The electrochemical properties of some of these com-
plexes have been studied by means of cyclic voltammetry,
and the molecular structures of 1, 2, 3, 4b, 4c and 6 have
been determined by X-ray diffraction.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
result. The yield of 5c is very low due to a competing forma- Germany, 2007)
the synthesis of (dibromovinyl)[2.2]paracyclophane and in-
Introduction
vestigated its reactivity towards [M(PPh3)4] (M = Pd,
Pt).[11c] For comparison, we embarked on a study on the
reactivity of (2,2-dibromovinyl)ferrocene (1), which shares
some common features with (dibromovinyl)[2.2]paracyclo-
phane such as planar chirality, redox activity and potential
applications in materials science. We now wish to report the
use of 1 for the synthesis of a functionalised vinylpalladi-
um(II) complex, the reactivity of 1 towards various thio-
lates (NaSR) and the subsequent rearrangement reactions
that lead to vinylic thioether compounds, which may also
serve as ligands in coordination chemistry. This work also
includes electrochemical investigations and several crystal
structure determinations.
Ethynylferrocene[1] is increasingly being used as building
block for the construction of di- and polymetallic organo-
metallic systems[2–5] due to the presence of an electrochemi-
cally active ferrocenyl unit. In contrast, only a few examples
of the preparation of polymetallic arrays starting from alk-
enylferrocenes have been reported in the literature.[6–9] In
addition to a covalent connection to other metal centres,
vinylferrocene has also been used as side-on bound π-ligand
for the synthesis of dimetallic compounds of the type
[M(CO)5{η2-H2C=C(H)Fc}] (M = Cr, Mo, W).[10] For the
past few years, we have been interested in the assembly of
homo- and heterodinuclear transition metal complexes and
the evaluation of their physicochemical properties (electro-
chemistry, luminescence).[11] Indeed, we recently published
Results and Discussion
[a] Institut UTINAM UMR CNRS 6213, Université de Franche-
Comté, Faculté des Sciences,
Oxidative Addition of (2,2-Dibromovinyl)ferrocene (1) to
[Pd(PPh3)4]
16, Route de Grey, 25030 Besançon Cedex, France
Fax: +33-3-81666438
E-mail: michael.knorr@univ-fcomte.fr
The starting material 1 was prepared according to a lit-
erature procedure under Corey–Fuchs conditions by treat-
ment of ferrocenecarbaldehyde with CBr4 in the presence
of zinc dust and PPh3 (Scheme 1).[12,13] An X-ray diffrac-
tion study (Figure 1) revealed that, in contrast to (dibro-
movinyl)[2.2]paracyclophane,[11c] the alkenyl unit and the
cyclopentadienido ring are almost parallel, with an in-
terplanar angle of only 10.43°.
[b] IUCINQUIMA/Química Inorgánica, Facultad de Ciencias,
Universidad de Valladolid,
47005 Valladolid, Spain
[c] Institut für Anorganische Chemie der Universität Würzburg,
Am Hubland, 97074 Würzburg, Germany
[d] Institut de Chimie Moléculaire UMR CNRS 5260, Université
de Bourgogne,
9, Avenue Alain Savary, 21078 Dijon, France
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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(2,2-Dibromovinyl)ferrocene in Heterodinuclear Complexes
Scheme 1.
Figure 1. Ball-and-stick view of the molecular structure of 1. Se-
lected bond lengths [Å] and angles [°]: C(12)–Br(2) 1.892(2), C(12)–
Br(1) 1.873(3), C(12)–C(11) 1.318(4), C(11)–C(1) 1.445(4); Br(1)–
C(12)–Br(2) 113.56(15), Br(2)–C(12)–C(11) 120.7(2), Br(1)–C(12)–
C(11) 125.7(2), C(12)–C(11)–C(1) 130.8(2).
Figure 2. Ball-and-stick view of the molecular structure of 2. For
clarity, only the vinylic hydrogen atom is shown. Selected bond
lengths [Å] and angles [°]: Pd–P(1) 2.3375(17), Pd–P(2) 2.3185(18),
Pd–Br(2) 2.4479(8), Pd–C(12) 2.037(6), C(12)–Br(1) 1.952(6),
C(12)–C(11) 1.272(9), C(11)–C(1) 1.481(8); P(1)–Pd–P(2)
166.74(5), Br(2)–Pd–C(12) 173.86(16), P(1)–Pd–C(12) 92.66(17),
P(2)–Pd–C(12) 90.21(17), P(1)–Pd–Br(2) 84.76(4), P(2)–Pd–Br(2)
93.61(4), Br(1)–C(12)–Pd 108.8(3), Pd–C(12)–C(11) 120.4(5),
C(12)–C(11)–C(1) 135.2(6).
Several experimental and theoretical studies have shown
that the oxidative addition of vinyl halides to low-valent
Pd0 centres leads to PdII complexes bearing a σ-alkenyl li-
gand.[14–18] For example, treatment of [Pd(PPh3)4] with β-
bromostyrene results in the formation of trans-
[PdBr(CH=CHPh)(PPh3)2].[18] The vinyl bromide 1 adds
oxidatively to [Pd(PPh3)4] at 60 °C in toluene solution in
a similar manner to produce the heterodinuclear σ-alkenyl
complex trans-[PdBr{C(Br)=C(H)–Fc}(PPh3)2] (2) in 76%
yield (Scheme 1). The trans geometry of the PPh3 ligands is
Reactivity of 1 Towards Various Thiolates
In the context of our work on the development of new
evidenced by the presence of a single resonance at δ = dithioether ligands and their coordination chemistry,[19–21]
22.7 ppm in the 31P{1H} NMR spectrum. Unfortunately, we recently demonstrated that the nucleophilic attack of
the reaction with [Pt(PPh3)4] under identical conditions led various thiolates on the π-conjugated 2-azabutadiene
mainly to the formation of cis-[PtBr2(PPh3)2].
[Cl2C=C(H)N=CPh2] in dmf affords the functionalised de-
The X-ray structure of 2, which is shown in Figure 2, rivatives [(RS)2C=C(H)–N=CPh2] (R = Ph, iPr) by replace-
reveals a slightly deformed square-planar coordination ment of the two vinylic chloro substituents by SR–.[22] If the
around Pd consisting of two trans PPh3 residues, a terminal reaction with sodium thiophenolate is carried out in a 1:1
bromo ligand and a vinylferrocene moiety. The C(11)–C(12) ratio, the monosubstituted product [(PhS)(Cl)C=C(H)-
double bond in 2 is shorter than in 1 [1.318(4) vs. N=CPh2] can be isolated. Unexpectedly, treatment of 1 with
1.272(9) Å]. The latter ligands are placed almost linearly, thiolates was less straightforward. Thus, when 1 is treated
with a Br(2)–Pd–C(12) angle of 173.86(16)°. Due to a ster- with just 1 equiv. of thiophenolate the reaction is incom-
eoselective activation of the Br(2)–C(12) bond during the plete and leads to the formation of a mixture of 1, the sub-
oxidative addition process, the stereochemistry about the stitution product 4a and some ethynylferrocene (3). Treat-
vinylic C(11)=C(12) double bond is anti (E) with respect to ment of 1 with a slight excess of NaSPh in dmf allowed us
the ferrocene unit and the Pd centre, with a C(1)–C(11)– to isolate the vinylic thioether 4a as an orange-red solid.
C(12)–Pd dihedral angle of 164.7°.
However, the elemental analysis and NMR spectroscopic
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M. Knorr et al.
FULL PAPER
data of 4a did not match the expected values for [(PhS)(Br)-
C=C(H)–Fc] but instead suggested the formulation (Z)-
[(PhS)(H)C=C(H)–Fc] (4a; Scheme 2). Treatment of 1 with
an excess of NaStBu in dmf also did not lead to the antici-
pated dithioether compound [(tBuS)2C=C(H)–Fc]. Instead,
analysis of the crude product by TLC indicated the presence
of (Z)-[(tBuS)(H)C=C(H)–Fc] (4b) together with a large
amount of ethynylferrocene (3). The formation of ethynyl-
ferrocene, which was isolated by column chromatography,
was unambiguously confirmed by an X-ray diffraction
analysis.
Figure 3. Ball-and-stick view of the molecular structure of 4b show-
ing the (Z) configuration around the C=C bond. For clarity, only
the vinylic hydrogen atoms are shown. Selected bond lengths [Å]
and angles [°]: C(10)–C(11) 1.458(7), C(11)–C(12) 1.351(8), C(12)–
S 1.749(5), C(13)–S 1.845(5), C(13)–C(14) 1.545(7); C(9)–C(10)–
C(11) 123.1(5), C(10)–C(11)–C(12) 128.8(5), C(11)–C(12)–S
125.0(4), C(12)–S–C(13) 103.0(3), C(14)–C(13)–S 110.1(3), C(15)–
C(13)–S 110.8(4), C(16)–C(13)–S 103.5(4).
Scheme 2.
The (Z) stereochemistry about the vinylic double bond
of 4b and the unexpected replacement of the Br substituent
by an H atom were also confirmed by X-ray diffractometry.
As illustrated in Figure 3, the crystallographic data unam-
Scheme 3.
biguously confirm the replacement of one bromine atom in toluenethiolate in dmf produces (Z)-1-phenyl-2-(p-tolylmer-
the (Z) position relative to the ferrocene unit by an StBu capto)ethene in a stereospecific manner. According to the
group and replacement of the second bromine atom by a kinetics of the reaction, a stepwise mechanism has been
hydrogen atom. The Cp ring bearing the vinyl group and suggested for this addition which is initiated by nucleophilic
the thioether function are almost coplanar, with a C(10)– attack of SR– at the β-carbon atom of Ph–CϵC–H, fol-
C(11)–C(12)–S torsion angle of 2.8°. We were unable to lowed by protonation of the resulting carbanionic interme-
synthesise the corresponding SEt derivative (Z)-[(EtS)(H)- diate.[27] We therefore attempted an alternative synthesis of
C=C(H)–Fc] (4c) by this method as, except for some minor 4c along this route by treating Fc–CϵC–H (3) with NaSEt
amounts of the dithioether compound (Z)-[(EtS)(H)- in dmf at room temperature. Indeed, 4c was now accessible
C=C(SEt)–Fc] (5c; see below), only ethynylferrocene (3) in 78% isolated yield as a red crystalline solid after workup
could be isolated from this reaction. X-ray checks carried in aqueous solution. An X-ray diffraction study confirmed
out on several differently shaped crystals and full analysis the (Z) disposition of the Fc moiety and the SEt substituent
of one sample always showed the presence of ethynylferro- about the C=C bond (see Figure 4). As in 4b, the Cp ring
cene.[23,24]
bearing the vinyl group and the thioether function are al-
A related structural motif was recently crystallographi- most coplanar, with a C(10)–C(11)–C(12)–S torsion angle
cally established for the vinylferrocene derivatives A and of 2.7°. The Cp rings of 4c are again placed in an eclipsed
B, which were obtained after hydrolysis or alcoholysis conformation.
of 2,3-diferrocenyl-1-(methylthio)cyclopropenylium iodide
The complex (Z)-[(PhS)(H)C=C(H)–Fc] (4a) is also ac-
cessible by this route. The (Z) arrangement of the two vi-
(Scheme 3).[25]
The formation of large amounts of ethynylferrocene can nylic hydrogen atoms of 4a is corroborated by the 1H NMR
be rationalised by a dehydrobromination reaction induced spectrum, which exhibits an AB pattern centred at δ =
by the basic thiolate reagent. It is well established that ad- 6.31 ppm with a typical vicinal (Z) coupling constant of
3
dition of thiolates (or thiols under basic conditions) across 10.1 Hz. Similar values (δ = 6.45 ppm, JA,B = 10.8 Hz)
the CϵC bond of alkynes leads to vinyl thioethers.[26–30] were recently reported for (Z)-[(PhS)(H)C=C(H)–C6H4O-
For example, treatment of phenylacetylene with sodium p- Me].[31a] In contrast, a JH,H coupling constant of 15.3 Hz
3
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(2,2-Dibromovinyl)ferrocene in Heterodinuclear Complexes
Figure 4. Ball-and-stick view of the molecular structure of 4c. Se-
lected bond lengths [Å] and angles [°]: C(10)–C(11) 1.463(7), C(11)–
C(12) 1.314(7), C(12)–S 1.750(4), C(13)–S 1.789(6), C(13)–C(14)
1.522(5); C(10)–C(11)–C(12) 129.6(4), C(11)–C(12)–S 126.8(4),
C(12)–S–C(13) 101.6(2), C(14)–C(13)–S 114.3(3).
has been reported for (E)-[(PhS)(H)C=C(H)–Ph], which
was obtained by Rh-catalysed hydrothiolation of phenyl-
acetylene.[31b] The NOESY spectrum (see Supporting Infor-
mation) reveals a weak correlation between the unresolved
Figure 5. Ball-and-stick view of the molecular structure of 6. Se-
Cp signal at δ = 4.62 ppm and the vinylic resonance at δ = lected bond lengths [Å] and angles [°]: Re–S(1) 2.4705(18), Re–S(2)
4
2.4807(16), Re–Br 2.6304(8), Re–C(27) 1.908(8), Re–C(28)
6.35 ppm, thereby proving the existence of a weak JH,H
1.944(9), Re–C(29) 1.947(9), C(12)–S(1) 1.755(7), C(11)–S(2)
1.807(7), C(12)–C(11) 1.331(9), C(11)–C(10) 1.466(9); Br–Re–C(27)
176.2(2), Br–Re–S(1) 79.42(5), Br–Re–S(2) 81.00(5), C(28)–Re–
“W-coupling”.
With the aim of synthesising ferrocene-based dithioether
ligands, complex 1 was treated with an excess of aromatic
thiolate (10 equiv.) at room temperature. Although the vi-
nylic dithioether complexes (Z)-[(ArS)(H)C=C(SAr)–Fc]
(5a,b) were formed as orange-red solids, albeit in moderate
yields (46–51%) due to a competing elimination reaction
that produces ethynylferrocene (3; Scheme 4), a closer look
at the NMR spectra of 5a,b and the X-ray data for the
heterodinuclear compound 6 (see Figure 5 for the rhenium
dithioether complex) revealed that a rearrangement reac-
tion again occurred.[32] The overall yield of 5c was lower
still (22%) with the more basic ethyl thiolate as nucleophile,
giving 3 in more than 50% yield as the main product.
C(29) 90.2(3), C(28)–Re–S(1) 92.5(3), C(28)–Re–S(2) 172.5(2),
C(29)–Re–S(2) 94.0(2), C(29)–Re–S(1) 172.7(2), C(10)–C(11)–
C(12) 124.0(6), C(11)–C(12)–S(1) 126.9(6), C(12)–C(11)–S(2)
119.1(5), C(10)–C(11)–S(2) 116.8(5), C(12)–S(1)–C(13) 100.3(3),
C(11)–S(2)–C(20) 101.3(3).
Coordination Chemistry of the Dithioether Ligand 5b
Preliminary studies demonstrated that dithioether com-
pounds 5 can be used as chelating ligands to assemble het-
erodinuclear compounds.[35] Thus, reaction monitoring by
IR spectroscopy revealed that treatment of dimeric
[Re(thf)(CO)3(µ-Br)]2 with 2 equiv. of 5b in CH2Cl2 solu-
tion led to formation of the brick-red complex [Fc{C(S–p-
tolyl)=C(S–p-tolyl)(H)}–Re(Br)(CO)3] (6; Scheme 5) almost
quantitatively, within 15 min. The facial arrangement of the
carbonyl groups of air-stable 6 can be deduced from the
observation of three ν(CO) vibrations in KBr at 2031, 1958
and 1930 cm–1.
Scheme 4.
The rearrangement discussed above, which results in a
(Z) substitution of C(11) and C(12) by S–p-tolyl groups,
A literature survey indicates that this rearrangement has was corroborated by an X-ray diffraction study. Figure 5
a precedent in organic chemistry. Thus, the mechanistic in- reveals that the octahedral coordination around the Re cen-
vestigations of Truce and Boudakian on the reactivity of tre is achieved by three carbonyl groups, a chelating dithio-
1,1-dichloroethylene towards an excess of sodium p-tolu- ether ligand and a bromo ligand, thus conferring an 18-
enethiolate in EtOH demonstrate that this reaction affords electron count at the ReI centre. The bromo substituent and
exclusively (Z)-1,2-bis(p-tolylmercapto)ethene. The inter- the ferrocenyl moiety of the dithioether ligand are directed
mediacy of an alkyne species ArS–CϵCH was suggested to in the same sense. The dithioether ligand forms a five-mem-
rationalize this interesting addition/elimination sequence.[33] bered ring with mean Re–S bond lengths of 2.4807 Å,
Another research group later independently confirmed which are somewhat shorter than those found for fac-
these findings with NaSPh as nucleophile and dmf as sol- [{(PhSCH2)2SiPh2}Re(Br)(CO)3] (2.515 Å).[36] Like in the
vent.[34]
latter compound, the aryl rings of the thioether groups are
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M. Knorr et al.
FULL PAPER
Scheme 5.
both syn-orientated and form a meso invertomer, although
they point in the opposite direction to the bromo li-
gand.[36,37]
Similarly, treatment of [PtCl2(PhCN)2] with a slight ex-
cess of 5b yielded the brownish air-stable square-planar
dithioether
complex
[Fc–{C(S–p-tolyl)=C(S–p-tolyl)-
(H)}PtCl2] (7a). The spectroscopic and elemental analysis
data are in agreement with a bidentate chelating coordina-
tion mode of 5b at the platinum atom, similar to that en-
countered in cis-[MCl2(MeSCH=CHSMe)] (M = Pd, Pt)
and other related PdII and PtII compounds.[38] Metathesis
with NaI in acetone solution converted 7a into red-brown
[Fc–{C(S–p-tolyl)=C(S–p-tolyl)(H)}PtI2] (7b), whose FAB+
mass spectrum displays the peak for the molecular ion. The
1H NMR spectrum of 7a recorded at 293 K displays a
rather broad unresolved signal between δ = 4.80 and
4.10 ppm for the Cp resonances; the vinylic proton gives
rise to a very broad hump centred at δ = 6.41 ppm. At
213 K, the vinylic proton appears sharper at δ = 6.54 ppm
and the Cp protons give rise to several signals in the range
δ = 4.58–3.92 ppm. This temperature-dependent behaviour
is most probably due to a pyramidal inversion process op-
erating for the two sulfur atoms that gives rise to meso and
 invertomers, as outlined in Scheme 6. Since this phe-
nomenon has been studied by us and several other groups
in the past,[20a,21a,36a,39] we did not undertake a detailed ki-
netic variable-temperature study. In contrast, the diiodo an-
alogue 7b displays well-resolved signals at room tempera-
ture, which barely sharpen upon heating to 313 K. This in-
dicates a fast exchange such that only one “averaged
planar” conformation is observed on the NMR time-
scale.
Scheme 6.
The vinylic proton signal at δ = 6.32 ppm exhibits a
3JPt,H coupling of 73 Hz, and two distinct singlets are ob-
served at δ = 2.41 and 2.34 ppm in a 1:1 ratio for the methyl
groups of the p-tolyl rings. We and others have previously
noted this finding for various PtX2 complexes ligated with
chelating dithioethers. The enhanced thermodynamic trans
influence of I over Cl elongates the Pt–S bonds (as corrobo-
rated by several X-ray structures), and the concomitant
weakening of the metal–sulfur bonds accounts for the lower
activation barrier of the inversion process.[20a,20b,21,39]
Electrochemistry
The anodic sweep of 1 in MeCN between –0.25 and
+0.75 V vs. Ag/Ag+ on a Pt electrode leads to a totally re-
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(2,2-Dibromovinyl)ferrocene in Heterodinuclear Complexes
versible peak in the cyclic voltammogram (CV), even for tween –0.40 and +2.00 V vs. Ag/Ag+ at a Pt electrode at
low scan rates (i.e. 100 mVs–1). The separation between the 100 mVs–1 leads to a voltammogram similar to that of 5b
anodic and cathodic peaks is about 60 mV, which indicates (see Supporting Information). However, the two irreversible
a fast electron transfer. The peak potential for 1 is about peaks in this voltammogram obtained after oxidation of the
+0.25 V vs. Ag/Ag+. In comparison with the corresponding two S-p-tolyl substituents are less well-defined than that for
peak values measured for the non-substituted ferrocene/ 5b. Moreover, the ferrocenium radical cation of 7a is more
ferrocenium couple (Ep = 0.21 V vs. Ag/Ag+) or the vinyl- stable than the corresponding radical cation of 5b. In fact,
ferrocene/ferrocenium couple (Ep = 0.24 V vs. Ag/Ag+), the we observe a partial reversibility of the first oxidation peak,
introduction of the CH=CBr2 group does not significantly even at low scan rate (100 mVs–1).
change the oxidation peak potential.[40a]
The CV of 2 in MeCN exhibits a reversible one-electron
oxidation peak at +0.08 V vs. Ag/Ag+ (ipc/ipa = 1, ∆E =
60 mV; see Supporting Information). This oxidation is
“easier” (i.e. occurs at lower positive potential) than that
for precursor 1 due to the electronic communication with
the electron-rich Pd(PPh3)2Br moiety. A contribution from
a Pd(PPh3)2Br motif was recently observed in (vinylferro-
cene)PdII complexes containing thiophene spacers of the
type [(C5H5)Fe(C5H4CH=CH–th–Pd(PPh3)2(Br)] (th = 2,5-
disubstituted thiophene).[41] The potentials of these com-
plexes were reported to be lower than those without an end-
capping Pd(PPh3)2Br unit, thereby implying the delocalis-
ation of Pd electron density into the spacer chain through
a dπǞpπ interaction. This behaviour is also observed for
dithioether 5b. The CV of 5b between –0.25 and +0.50 V
vs. Ag/Ag+ on a Pt electrode at 100 mVs–1 reveals the pres-
ence of a reversible peak also involving a fast electron trans-
Figure 6. CV of 5b (1 m) in CH2Cl2 + Bu4NPF6 (0.1 ) at
100 mVs–1 at a platinum electrode.
fer (see Supporting Information). Since this ferrocene deriv-
The same electrochemical measurements were also per-
ative bears two electron-donating substituents, the oxi-
formed using glassy carbon electrodes. All voltammograms
dation is “easier” than that for 1. The potential of the re-
are very similar. The only difference observed between plati-
versible peak for 5b (Ep = 0.19 V vs. Ag/Ag+) is lower than
num and carbon electrodes concerns the value of Ep
that for 1. Oxidation of 7a between 0.00 and +0.60 V vs.
(Table 1).
Ag/Ag+ on a platinum electrode at 100 mVs–1 again leads
to a reversible signal (see Supporting Information). Actu-
ally, the complexation of 5b with a PtCl2 fragment decreases
the electronic density on the ferrocene moiety and the oxi-
dation peak is therefore shifted towards higher oxidation
potentials with respect to that for 1 and 5b. The E0 value
(Ep = 0.39 V vs. Ag/Ag+) is larger than that for compound
1. This behaviour is also observed for compound 6. The E0
value for the couple 6/6·+ (Ep = 0.33 V vs. Ag/Ag+) is in the
same range as that for the couple 7a/7a·+ (Ep = 0.39 V vs.
Ag/Ag+). A shift after complexation with metal centres has
also been noted previously for other ferrocene-based thio-
ether ligands.[35e]
Table 1. Values of standard potentials or peak potentials for mono-
mer/radical cation in dichloromethane (vs. Ag/Ag+) deduced from
CV measurements.
Compound
Ep [V] on Pt electrode
Ep [V] on C electrode
1
2
5b
6
7
0.25
0.25
0.08
0.13, 1.21
0.32, 1.59
0.36, 1.59
0.19, 1.16, 1.19
0.33, 1.61
0.39, 1.72
Solid-State Luminescence of 5b and 6
When excited at 270 nm, the solid-state emission spectra
The CV of 5b between –0.40 and +2.00 V vs. Ag/Ag+ on
a Pt electrode at 100 mVs–1 reveals a different shape of the
voltammogram curve (Figure 6). Thus, we now observe of 5b and the heterometallic system 6 (Figure 7) at room
three irreversible waves at 0.19, 1.16 and 1.29 V vs. Ag/Ag+. temperature are quite similar, with a broad band at 668 and
The first irreversible wave corresponds to the oxidation of 670 nm, respectively. This band is tentatively assigned to an
the ferrocene moiety. Surprisingly, the lifetime of the ferro- intraligand transition. More importantly, the incorporation
cenium radical cation formed during the oxidation in this of ferrocene and its derivatives in a luminescent system pro-
experiment is not long enough to be observed during the duced effective quenchers of excited states by energy-trans-
reversible scan. This behaviour is usually not observed for fer processes.[42a] These compounds are known for their ca-
ferrocenium radical cations. This phenomenon is probably pacity to inhibit the lowest energy states of a number of
due to the low scan rate and the high value of the final molecules frequently used as photosensitizers.[42b,42c] This
potential. Partial peak reversibility is again observed when finding may also explain the luminescence quenching of the
we increase the scan rate to 200 mVs–1. The CV of 7a be- rhenium fragment in compound 6.
Eur. J. Inorg. Chem. 2007, 5052–5061
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5057

M. Knorr et al.
FULL PAPER
supporting electrolyte. The concentration of the monomeric sub-
strate was 10–3 . Under these conditions, the E1/2 of Cp2Fe+/0 was
found to be 0.21 VϮ0.01 V (CH2Cl2) vs. an Ag reference.
Preparation of trans-[(PPh3)2PdBr{C(Br)=C(H)–Fc}] (2): Com-
pound 1 (185 mg, 0.5 mmol) was added to a suspension of
[Pd(PPh3)4] (520 mg, 0.45 mmol) in toluene (15 mL) and the mix-
ture was warmed to 60 °C for 1 d. The resulting clear, red solution
was then concentrated to 8 mL and layered with heptane. Complex
2 crystallised as red needles after storing this solution in a refrigera-
1
tor overnight. Yield: 76% (380 mg). H NMR: δ = 7.77 (m, 10 H,
Figure 7. Corrected and normalised solid-state luminescence spec-
tra recorded at room temperature for compounds 5b (solid) and 6
(dotted).
Ph), 7.17–7.41 (m, 20 H, Ph), 6.09 (s, 1 H, Hvinyl), 3.93 (m, 2 H,
Cp), 3.81 (m, 2 H, Cp), 3.72 (s, 5 H, Cp) ppm. 31P{1H} NMR: δ
=
22.7 (s) ppm. UV/Vis (CH2Cl2): λmax (ε) = 229 nm
(62800 –1 cm–1), 310 (13100), 365 (13600). C48H40Br2FeP2Pd
(1000.9): calcd. C 57.60, H 4.03; found C 57.48, H 4.09.
Conclusion and Perspectives
Typical Procedure for the Conversion of the Dibromo Olefin 1 into
4a–c and 5a–c: Compound 1 (1 mmol) was stirred with an excess
of thiolate (10 mmol) in dry dmf (10 mL) at room temperature for
1 d. The reaction mixture was then poured into water (10 mL). The
organic layer was extracted with Et2O (2ϫ25 mL), washed with
brine (20 mL) and water (2ϫ25 mL) and dried with Na2SO4. Evap-
oration of the solvents gave the crude products. Purification was
carried out by chromatography on silica gel. In the case of treat-
ment of 1 with 4 equiv. of thiolates, the ratios of thioether com-
pounds 4a/3 and 4b/3 were both 25%/75%.
This study has demonstrated that the reactivity of 1
towards thiolates is not trivial. We are currently investiga-
ting these rearrangement reactions in more detail {isolation
of intermediates, influence of temperature and solvent, uti-
lisation of [Cl2C=C(H)–Fc] instead of [Br2C=C(H)–Fc] as
starting material, use of other aromatic substrates such as
(dibromovinyl)[2.2]paracyclophane, …} to develop a clear
mechanistic understanding of these interesting transforma-
tions. Moreover, the preparation of π-conjugated thioether
ligands 4 and 5 allows a promising development in organo-
metallic coordination chemistry. We are currently working
on the synthesis, reactivity and electrochemical investiga-
tion of other neutral and ionic complexes ligated by 4 and
5. Furthermore, the substitution of the bromo substituents
of 1 by –OR, –NR2 or –PR2 may also lead to promising new
ligand systems.
FcCH=CH(SPh) (4a): Eluent: CH2Cl2/petroleum ether (1:9). M.p.
3
50 °C. 1H NMR: δ = 7.25–7.52 (m, 5 H, Ph), 6.35 (d, JH,H
=
10.1 Hz, 1 H, HA,vinyl), 6.26 (d, 3JH,H = 10.1 Hz, 1 H, HB,vinyl), 4.62
(br. s, 2 H), 4.27 (br. s, 2 H, Cp), 4.16 (s, 5 H, Cp) ppm. 13C{1H}
NMR: δ = 68.9, 69.2, 69.3, 80.8 (CpHC=), 121.0 (CpHC=), 126.5,
126.8, 129.0, 129.3 [C-14, C-15, C-16, C-17, C-18, =CH(SPh)],
136.6 (C-13) ppm. C18H16FeS (320.23): calcd. C 67.51, H 5.04, S
10.01; found C 67.42, H 5.74, S 9.80.
FcCH=CH(StBu) (4b): Eluent: CH2Cl2/petroleum ether (1:9).
1
3
Yield: 52% (156 mg). M.p. 50–52 °C. H NMR: δ = 6.19 (d, JH,H
Experimental Section
3
= 10.0 Hz, 1 H, HA,vinyl), 6.11 (d, JH,H = 10.0 Hz, 1 H, HB,vinyl),
General: All reactions were performed using a conventional
vacuum/argon line with standard Schlenk techniques. (2,2-Di-
bromovinyl)ferrocene (1), [Pd(PPh3)4], [Re(µ-Br)(CO)3(thf)]2 and
[PtCl2(PhCN)2] were prepared according to literature meth-
ods.[13,43] Thiophenol, p-thiocresol, 2-methyl-2-propanethiol and
ethanethiol were purchased from commercial sources and used
without further purification. All solvents were distilled from appro-
priate drying agents. IR spectra were recorded with a Nicolet
Nexus 470 spectrometer. All NMR spectra were recorded in CDCl3
with a Bruker AC 300 (1H: 300.13 MHz; 13C: 75.48 MHz; 31P:
121.49 MHz) using the solvent as reference, except for 31P, where
the chemical shifts are quoted relative to 85% H3PO4 in D2O. UV/
Vis spectra were recorded with a Varian Cary 50 spectrophotome-
ter. The solid-state emission spectra were recorded at room tem-
perature with a Jobin–Yvon Fluorolog-3 spectrometer using a cy-
lindrical quartz capillary (diameter: 0.5 cm) with a scan speed of
1 nms–1. Intensity scales are presented in arbitrary units. The FAB+
mass spectrum of 7b was obtained with a VG Autospec spectrome-
ter using NBA as matrix.
4.58 (br. s, 2 H, Cp), 4.23 (br. s, 2 H, Cp), 4.15 (s, 5 H, Cp), 1.43
(s, 9 H, CH3) ppm. 13C{1H} NMR: δ = 30.9 (CH3), 43.8 [C-
(CH3)3], 68.5, 69.1, 69.2, 81.9 (CpHC=), 119.5 (CpHC=), 124.1
[=CH(StBu)] ppm. UV/Vis (CH2Cl2): λmax (ε) = 229 (16200), 251
(10500), 298 (9100), 351 (7100), 452 nm (3900 –1 cm–1). C16H20FeS
(300.23): calcd. C 64.00, H 6.67, S 10.67; found C 63.98, H 6.58, S
10.62.
1
FcCH=CH(SEt) (4c): Eluent: petroleum ether. M.p. 38–39 °C. H
3
3
NMR: δ = 6.14 (d, JH,H = 10.4 Hz, 1 H, HA,vinyl), 5.95 (d, JH,H
= 10.4 Hz, 1 H, HB,vinyl), 4.32 (br. s, 2 H, Cp), 4.24 (br. s, 2 H, Cp),
3
4.12 (s, 5 H, Cp), 2.75 (q, JH,H = 7.4 Hz, 2 H, SCH2CH3), 1.22 (t,
3JH,H = 7.4 Hz, 2 H, SCH2CH3) ppm. UV/Vis (CH2Cl2): λmax (ε)
= 229 (11500), 250 (9200), 298 (10900), 351 (550), 452 nm
(350 –1 cm–1). C14H16FeS (272.18): calcd. C 61.76, H 5.88, S 11.76;
found C 61.68, H 5.73, S 11.67.
Alternative Preparation of 4a and 4c: Ethynylferrocene (210 mg,
1 mmol) was added to a stirred solution of thiolate (10 mmol) in
dmf (10 mL). The solution was stirred at room temperature for 1 d
and then poured into water. The organic layer was extracted with
diethyl ether, washed with water (5 mL) and brine (2ϫ5 mL) and
dried with Na2SO4. Solvent evaporation provided the crude prod-
ucts. Column chromatography with petroleum ether as eluent af-
forded 207 mg of 4a (yield: 76%) and 249 mg of 4c (yield: 78%).
Electrochemical Setup: Analytical experiments were performed in a
three-compartment cell fitted with an AgClO4 (0.1  in CH3CN)|
Ag reference electrode, a glassy carbon electrode (diameter: 3 mm)
or a Pt electrode (diameter: 1 mm) and a platinum counter elec-
trode. The electrochemical apparatus was an Autolab PGSTAT 20
Potentiostat Galvanostat (Ecochemie). The solvent was spectro-
scopic grade CH2Cl2 or acetonitrile with [Bu4N][PF6] (TBAF) as
FcC(SPh)=CH(SPh) (5a): Obtained by column chromatography on
1
silica gel with petroleum ether as eluent (197 mg, 46%). H NMR:
5058
www.eurjic.org
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 5052–5061

(2,2-Dibromovinyl)ferrocene in Heterodinuclear Complexes
δ = 4.17 (s, 5 H, Cp), 4.23 (s, 2 H, Cp), 4.48 (br. s, 2 H, Cp), 7.13
(s, 1 H, Hvinyl), 7.23–7.52 (m, 10 H, Ph) ppm. 13C{1H} NMR: δ =
69.3, 69.8, 70.1 (C-1–C-9), 79.7 (C-10), 123.5, 125.6, 127.1, 127.3,
127.4, 129.0, 129.2, 129.9, 130.1, 130.7, 132.2, 134.7, 135.0, 135.5,
135.9, 141.2 (C-11–C-24) ppm. C24H20FeS2 (428.39): calcd. C
67.29, H 4.67, S 14.95; found C 67.18, H 4.59, S 14.83.
(47800), 300 (16100), 382 (2200), 482 nm (1700 –1 cm–1).
C29H24BrFeReO3S2·0.5CH2Cl2 (849.09): calcd. C 41.72, H 2.95;
found C 41.85, H, 3.00.
[FcC(S–p-tolyl)=C(H)(S–p-tolyl)PtCl2]
(7a):
[PtCl2(PhCN)2]
(127 mg, 0.3 mmol) was added in several portions to a solution of
5b (136 mg, 0.3 mmol) in CH2Cl2 (8 mL). The reaction mixture was
stirred at room temperature for 4 h and then concentrated to 5 mL
FcC(S–p-tolyl)=CH(S–p-tolyl) (5b): Eluent: petroleum ether/
1
CH2Cl2 (9:1). Yield: 51% (230 mg). M.p. 135–136 °C. H NMR: δ under reduced pressure. Addition of light petroleum gave an orange
= 7.30–7.00 (m, 9 H, C6H4 + Hvinyl), 4.40 (br. s, 2 H, Cp), 4.15 (br.
powder, which was filtered off and dried under vacuum. Yield: 91%
s, 2 H, Cp), 4.09 (s, 5 H, Cp), 2.31 (s, 3 H, CH3), 2.24 (s, 3 H, CH3) (197 mg). 1H NMR (213 K): δ = 7.79–7.30 (m, 8 H, C6H4), 6.54
ppm. 13C{1H} NMR: δ = 21.3, 21.4 (CH3), 67.2, 69.2, 69.9 (Cp),
87.5 (CpHC=), 128.0, 128.1, 128.9, 130.1, 130.3, 130.9, 132.4,
(br. s, 1 H, Hvinyl), 4.58–3.92 (m, 9 H, Cp), 2.40 (br. s, 3 H, CH3),
2.36 (br. s, 3 H, CH3) ppm. UV/Vis (CH2Cl2): λmax (ε) = 228
132.8, 133.2, 135.8 (C6H4), 137.7 [=C(SC6H4CH3)2] ppm. UV/Vis (69500), 295 (20200), 382 (2400), 487 nm (1600 –1 cm–1).
(CH2Cl2): λmax (ε)
= 229 (64100), 257 (32200), 330 nm C26H24Cl2FePtS2 (722.43): calcd. C 43.23, H 3.35, S 8.88; found C
(9100 –1 cm–1). C26H24FeS2 (456.44): calcd. C 68.42, H 5.30, S
43.02, H 3.12, S 8.54.
14.05; found C 68.48, H 5.38, S 14.12.
[FcC(S–p-tolyl)=C(H)(S–p-tolyl)PtI2] (7b): NaI (150 mg, 10 mmol)
was added to a solution of 7a (72 mg, 0.1 mmol) in acetone (5 mL).
The reaction mixture was stirred at room temperature for 1 d and
then the solvent was evaporated under reduced pressure. Extraction
FcC(SEt)=CH(SEt) (5c): Obtained by column chromatography on
silica gel with petroleum ether as eluent (134 mg, 22%). H NMR:
δ = 6.26 (s, 1 H, Hvinyl), 4.53 (br., 2 H, Cp), 4.29 (s, 2 H, Cp), 4.11
1
(s, 5 H, Cp), 2.85 (m, 4 H, SCH2CH3), 2.77 (m, 4 H, SCH2CH3), of the crude product with CH2Cl2 (4 mL) and addition of heptane
1.29 (m, 3 H, SCH2CH3), 1.27 (m, 3 H, SCH2CH3) ppm. gave an orange powder, which was filtered off and dried under vac-
C16H20FeS2 (332.31): calcd. C 57.83, H 6.07, S 19.30; found C
57.78, H 5.93, S 19.18.
uum. Yield: 90% (76 mg). 1H NMR: δ = 7.68–7.19 (m, 8 H, C6H4),
3
6.32 (br. s, JPt,H = 73 Hz, 1 H, Hvinyl), 4.53–4.09 (m, 9 H, Cp),
2.41 (s, 3 H, CH3), 2.34 (s, 3 H, CH3) ppm. FAB+ (NBA): m/z =
906.1 [M+]. C26H24FeI2PtS2 (905.34): calcd. C 34.49, H 2.67; found
C 34.12, H 2.76.
[FcC(S–p-tolyl)=C(H)(S–p-tolyl)2Re(Br)(CO)3](6):[Re(µ-Br)(CO)3-
(thf)]2 (127 mg, 0.15 mmol) was added in several portions to a solu-
tion of 5b (136 mg, 0.3 mmol) in CH2Cl2 (5 mL). The reaction mix-
ture was stirred at room temperature for 2 h and then concentrated
to 3 mL under reduced pressure. Layering with heptane gave red
needles after several days at 5 °C. Yield: 92% (119 mg). IR (KBr):
X-ray Crystallography: Crystal data and experimental details are
given in Table 2. Data for 2 and 6 were collected with a Stoe IPDS
diffractometer at 173(2) (2) and 193(2) K (6). The intensities were
determined and corrected with the program INTEGRATE in IPDS
(Stoe & Cie, 1999). An empirical absorption correction was em-
ployed using the FACEIT program in IPDS (Stoe & Cie, 1999).
Data for 1 and 4b,c were collected with a Bruker APEX-CCD (D8
1
ν(CO) = 2031 (vs), 1958 (s), 1931 (vs) cm–1. H NMR: δ = 7.37–
7.27 (m, 8 H, C6H4), 7.07 (s, 1 H, Hvinyl), 4.83 s, (br., 2 H,
Cp), 4.45 (br. s, 2 H, Cp), 4.55 (s, 5 H, Cp), 2.40 (s, 3 H,
CH3), 2.37 (s, 3 H, CH3) ppm. UV/Vis (CH2Cl2): λmax (ε) = 231
Table 2. X-ray crystallographic and refinement data for 1, 2, 4b, 4c and 6.
1
2
4b
4c
6
Empirical formula
C12H10Br2Fe
369.87
C48H40Br2FeP2Pd
1000.81
C16H20FeS
300.23
C14H16FeS
272.18
C29H24BrFeO3ReS2
806.56
Formula mass [gmol–1
]
T [K]
173(2)
173(2)
193(2)
173(2)
193(2)
Crystal system
Space group
a [Å]
b [Å]
c [Å]
orthorhombic
Pbca
7.5029(5)
17.1025(11)
18.1892(12)
90
2334.0(3)
8
2.105
monoclinic
P21/n
monoclinic
P21/n
5.9214(12)
10.199(2)°
12.232(2)°
96.88
733.4(3)
2
1.359
monoclinic
C2/c
monoclinic
P21/c
20.385(5)
7.6128(12)
29.280(5)
109.21(3)
4035.4(14)
4
31.07(3)
10.509(6)
7.457(9)
91.42(3)
2463(4)
8
10.169(2)
25.404(5)
11.609(2)
107.25(3)
2864.2(10)
4
β [°]
V [Å3]
Z
ρcalcd. [Mgm–3
]
1.647
2.899
1.468
1.362
1.870
6.298
µ [mm–1
]
8.101
1.150
F(000)
1424
2000
316
1136
1560
Θ range [°]
Index ranges
2.24–26.43
–9ՅhՅ9
–21ՅkՅ21
–22ՅlՅ22
46927
2.39 –25.00
–10ՅhՅ10
–45ՅkՅ45
–14ՅlՅ14
24804
2.61–25.00
–7ՅhՅ7
–12ՅkՅ12
–14ՅlՅ14
6312
1.31–26.99
–39ՅhՅ39
–13ՅkՅ13
–9ՅlՅ9
16681
2.10–26.99
–12ՅhՅ12
–29ՅkՅ32
–14ՅlՅ8
12577
Collected reflections
Independent reflections
Data/restraints/parameters
2409 [R(int) = 0.0430] 7081 [R(int) = 0.0654] 2559 [R(int) = 0.0515] 2693 [R(int) = 0.0287] 6127 [R(int) = 0.0529]
2409/0/136
7081/0/487
2559/1/166
2693/0/146
6127/0/336
Largest difference peak/hole [eÅ–3
Final R indices [I Ͼ 2σ(I)]
]
0.663 and –0.377
R1 = 0.0260
wR2 = 0.0622
R1 = 0.0327
wR2 = 0.0652
1.067
1.027 and –1.036
R1 = 0.0517
wR2 = 0.1296
R1 = 0.0726
wR2 = 0.1412
1.045
0.8026 and 0.6562
R1 = 0.0551
wR2 = 0.1410
R1 = 0.0586
wR2 = 0.1445
1.023
0.7724 and 0.6119
R1 = 0.0335
wR2 = 0.0952
R1 = 0.0370
wR2 = 0.1058
1.027
1.704 and –1.816
R1 = 0.0474
wR2 = 0.1140
R1 = 0.0646
wR2 = 0.1212
1.036
R indices (all data)
GOF on F2
Eur. J. Inorg. Chem. 2007, 5052–5061
© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
5059

M. Knorr et al.
FULL PAPER
Strohmann, A. Decken, Y. Mugnier, P. D. Harvey, Inorg. Chem.
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4–6.
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129, 799–805; d) C. Strohmann, E. Wack, Z. Naturforsch. Teil
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a) M. Knorr, H. N. Peindy, F. Guyon, H. Sachdev, C.
Strohmann, Z. Anorg. Allg. Chem. 2004, 630, 1955–1961; b)
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three-circle goniometer, Bruker AXS) at 173(2) K; data collection,
cell determination and refinement: Smart version 5.622 (Bruker
AXS, 2001); integration: SaintPlus version 6.02 (Bruker AXS,
1999); empirical absorption correction: Sadabs version 2.01
(Bruker AXS, 1999). All structures were solved applying direct and
Fourier methods, using SHELXS-90 and SHELXL-97.[44] For each
structure, the non-hydrogen atoms were refined anisotropically. All
of the hydrogen atoms were placed in geometrically calculated posi-
tions and each was assigned a fixed isotropic displacement param-
eter based on a riding model. Refinement of the structures was
carried out by full-matrix least-squares methods based on Fo2 using
SHELXL-97. CCDC-644866 to -644869 (for 1, 2, 4c, 6), -646158
(for 3), and -650184 (for 4b) contain the supplementary crystallo-
graphic data for this paper. These data can be obtained free of
charge from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
Supporting Information (see footnote on the first page of this arti-
cle): Crystallographic data and view of the structure and packing
of 3 (Figure S1). Cyclic voltammograms of 2, 5b and 7a are de-
picted in Figures S2–S5. Figures S6–S10 show the thermal ellipsoid
1
[20]
plots of 1, 2, 4b, 4c and 6. The NOESY H NMR spectrum of 4a
is shown in Figure S11.
Acknowledgments
We are grateful to the French Ministère de la Recherche et Technol-
ogie for a PhD grant for S. C. Financial support from the Région of
Franche-Comté for the fluorescence spectrometer is also gratefully
acknowledged. We thank Dr. A. Khatyr for recording the emission
spectra and Dr. Harmel N. Peindy (University of Bochum, Ger-
many) for recording the FAB+ mass spectrum of 7b.
[21]
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Received: May 2, 2007
Published Online: September 14, 2007
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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