Iron(II) and iron(III) complexes containing ethynyl thiophene fragments

Article abstract of DOI:10.1016/j.jorganchem.2004.10.006

The synthesis of the new complexes Cp*(dppe)Fe-C≡C-2,5-C ₄H₂SR (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; dppe = 1,2-bis(diphenylphosphino)ethane; 2a, R = C≡CH; 2b, R = C≡C-Si(CH₃)₃; 2c, R = C≡C-Si(CH(CH ₃)₂)₃; 3a, R = C≡C-2,5-C ₄H₂S-C≡CH; 3c, R = C≡C-2,5-C₄H ₂S-C≡C-Si(CH(CH₃)₂)₃) is described. The ¹³C NMR and FTIR spectroscopic data indicate that the π-back donation from the metal to the carbon rich ligand increases with the size of the organic π-electron systems. The new complexes were also analyzed by CV and the chemical oxidation of 2a and 3c was carried out using 1 equiv of [Cp₂Fe][PF₆]. The corresponding complexes 2a[PF ₆] and 3c[PF₆] are thermally stable, but 2a[PF ₆] was too reactive to be isolated as a pure compound. The spectroscopic data revealed that the coordination of large organic π-electron systems to the iron nucleus produces only a weak increase of the carbon character of the SOMO for these new organoiron(III) derivatives.

Full text of DOI:10.1016/j.jorganchem.2004.10.006

Journal of Organometallic Chemistry 690 (2005) 594–604
www.elsevier.com/locate/jorganchem
Iron(II) and iron(III) complexes containing ethynyl
thiophene fragments
*
´ ´
Severine Roue, Claude Lapinte
´ ´ ´
Organometalliques et Catalyse: Chimie et Electrochimie Moleculaire, UMR CNRS 6509, Universite de Rennes 1, Institut de chimie de
Rennes, Campus de Beaulieu, Bat 10C, F35042 Rennes, France
Received 23 July 2004; accepted 6 October 2004
Available online 13 November 2004
Abstract
The synthesis of the new complexes Cp*(dppe)FeACBCA2,5-C4H2SR (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl;
dppe = 1,2-bis(diphenylphosphino)ethane; 2a, R = CBCH; 2b, R = CBCASi(CH3)3; 2c, R = CBCASi(CH(CH3)2)3; 3a, R =
CBCA2,5-C4H2SACBCH; 3c, R = CBCA2,5-C4H2SACBCASi(CH(CH3)2)3) is described. The 13C NMR and FTIR spectroscopic
data indicate that the p-back donation from the metal to the carbon rich ligand increases with the size of the organic p-electron
systems. The new complexes were also analyzed by CV and the chemical oxidation of 2a and 3c was carried out using 1 equiv
of [Cp2Fe][PF6]. The corresponding complexes 2a[PF6] and 3c[PF6] are thermally stable, but 2a[PF6] was too reactive to be isolated
as a pure compound. The spectroscopic data revealed that the coordination of large organic p-electron systems to the iron nucleus
produces only a weak increase of the carbon character of the SOMO for these new organoiron(III) derivatives.
ꢀ 2004 Elsevier B.V. All rights reserved.
Keywords: Organoiron; Iron(II); Iron(III); Acetylides; Ethynylthiophene; Redox-active
1. Introduction
that molecules in which an electron-rich and redox-
active Cp*(dppe)Fe unit is connected to a different metal
center through organic p-networks also possess fascinat-
ing properties [21–24]. At the same time, we also found
that replacement of a phenyl unit by a thiophene ring in
the carbon-rich bridges which link the organoiron units
significantly improved the electronic and magnetic inter-
actions between the metal centers [16,25].
The synthesis of new molecular architectures incorpo-
rating organometallic centers connected by extended p-
networks requires the development of new synthons. We
recently described the preparation and basic properties
of the pivotal building block Cp*(dppe)FeCBCA1,
4-C6H4ACBCH [26], and now our interest is focused on
the access to parent compounds containing thiophene
rings as depicted on Chart 1.
The development of organometallic molecular assem-
blies incorporating metal atoms in organic p-networks
has aroused a great deal of interest, owing to the fasci-
nating properties that these combinations exhibit [1–9].
Over the past decade, we have been engaged in the study
of redox-active organoiron compounds featuring several
electroactive Cp*(dppe)Fe units linked together, either
directly through polyynyl bridges or via a central arene
by means of ethynyl linkers [10–20]. Depending on their
structures and on the oxidation states of the iron
centers, these molecules exhibit electronic properties
potentially useful for the realization of various molecu-
lar-scale devices [1,2]. More recently, we have shown
In the electron-rich Cp*(dppe)Fe series, isolation and
purification of the mononuclear complexes are some-
times difficult and therefore the development of selective
*
Corresponding author. Tel.: 33 2 23 23 59 63; fax: 33 2 23 23 59
63.
E-mail address: claude.lapinte@univ-rennes1.fr (C. Lapinte).
0022-328X/$ - see front matter ꢀ 2004 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2004.10.006

´
S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
595
preparation of the organic precursors 8–10, (ii) the syn-
theses of the complexes 2a–c and 3a–c, (iii) their charac-
terization and redox properties, (iv) the preparation of
the parent iron(III) derivatives 2a[PF6] and 3c[PF6]
and (v) the optical properties of these new iron
compounds.
S
Fe
P
P
1
S
Fe
R
2. Results
P
P
2a, R = H
2.1. Preparation of the organic precursors 8–10
2b, R = Si(CH3)3
2c, R = Si(CHMe2)3
The non-symmetrical bis(ethynyl)thiophene 8 was
prepared by a Sonogashira coupling reaction following
procedures reported in the literature. The palladium–
copper catalysed reaction between the known
2-iodo-(5-trimethylsilylethynyl)thiophene 6, and the
(trisisopropylsilyl)acethylene 7, gave 8 in 90% yield after
chromatography on a silica column (Scheme 2). Treat-
ment of 8 with potassium carbonate in methanol at
20 ꢁC allows the facile and selective cleavage of the tri-
methylsilyl terminal group and affords 9 in 90% yield
after purification. Similarly, the palladium–copper cata-
lyzed coupling between 6 and 9 provides 10 in 58% yield
after chromatography.
S
S
Fe
P
R
P
3a, R = H
3c, R = Si(CHMe2)3
Chart 1.
reactions is highly desirable. We have previously found a
‘‘metalla-Sonogashira’’ coupling reaction [17,18], which
allowed us to specifically graft various substituted bro-
mo-aromatics onto the Cp*(dppe)FeCCH complex
[27,28]. Using such an approach, Bruce et al. [29,30] also
succeeded in functionalizing various terminal diynyl
Mo(II) or W(II) complexes. Thus, starting from the
organometallic terminal alkynyl complex Cp*(dppe)-
FeCBCH (4), various organoiron(II) derivatives con-
taining halogeno-substituted thiophene fragments
could be prepared (route A, Scheme 1). An alternative
route to the target molecules can also consist in the ini-
tial preparation of the organic fragment and then, to its
complexation to the Cp(dppe)FeCl (5) complex in a last
step (route B, Scheme 1). We now report on (i) the
2.2. Synthesis of the iron complex 2a via 2b and 2c
The complexes Cp*(dppe)FeACBCAC4H2SACB
CSiR3 (2b, 2c) were prepared by two different routes
(Scheme 3). The palladium coupling reaction in the
coordination sphere of iron was extended to the
S
H
Si(CH(CH3)2)3
+
I
Si(CH3)3
7
6
i
S
Fe
P
H +
X
R
S
P
P
P
((H3C)2HC)3Si
SiMe3
4
8, yield 90 %
ii
A
S
iii
S
((H3C)2HC)3Si
H
Fe
P
R
9, yield 90 %
B
S
((H3C)2HC)3Si
Si(CH3)3
10, yield 58 %
S
S
Fe Cl
H
+
R
P
Scheme 2. Key reagents: (i) (Ph3P)2PdCl2, CuI, ((CH3)2CH)2NH,
THF; (ii) MeOH, K2CO3; (iii) 6, THF, (Ph3P)2PdCl2, CuI,
((CH3)2CH)2NH.
5
Scheme 1.

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S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
596
preparation of iron complexes containing thiophene
rings. The terminal iron alkynyl complex 4 reacts with
6 in the presence of the Pd/Cu catalyst leading to isola-
tion of 2b in 77% yield. Alternatively, the chloro iron
derivative Cp*(dppe)FeCl 5 reacts with the terminal or-
ganic alkyne 9 to produce 2c via the corresponding viny-
lidene intermediate which is in situ deprotonated by
addition of 1 equiv. of KOBut before removal of the sol-
vent. From a synthetic standpoint, this route compares
favourably with the Sonogashira coupling reaction in
the coordination sphere giving 2c as a pure orange pow-
der in 82% yield. It can be noted in contrast, that the
‘‘metalla-Sonogashira’’ route was preferred to access
to similar compounds containing benzene cycles instead
of thiophene rings [18].
Carried out at 20 ꢁC, the cleavage of the SiR3 group
provides 2a in 85% yield either from 2b or 2c. However
different conditions must be used in these two cases. The
complex 2b was reacted in a MeOH/THF (v/v: 50/50)
mixture with potassium carbonate whereas, 2c required
a treatment with tetrabutylammonium fluoride in THF.
The complexes 2a–c were characterized by the usual
techniques (see Section 4).
uct which results from the homocoupling between two
molecules of 2a was identified by comparison to an
authentic sample independently prepared [31]. The sep-
aration of 3b and 11 present in ca. 20% in the mixture
could not be achieved.
The alternative route B (Scheme 1) was more success-
ful. The complex 3a was prepared following a one-pot
procedure involving two successive reactions. The reac-
tor was charged with the iron halide 5, sodium tetraphe-
nylborate, potassium carbonate, the organic reagent 10
dissolved in THF, and methanol. In these conditions,
the terminal alkyne HACBCA2,5-C4H2SACBCA2, 5-
C4H2SACBCASi(CH(CH3)2)3 was in situ generated by
reaction of 10 with K2CO3.
Then, the terminal organic alkyne reacts with the iron
complex 5 to give a vinylidene intermediate and the dark
green color of the solution progressively turns red. Addi-
tion of 1 equiv. of KOBut promotes the deprotonation
of the vinylidene and gives the target compound 3c.
The air sensitive complex 3c was isolated as a dark red
powder in 88% yield. Treatment of the complex 3c with
tetrabutylammonium fluoride in THF at 20 ꢁC provided
3a in 70% yield. The complexes 3a and 3c were charac-
terized by the usual techniques (see Section 4).
2.3. Synthesis of the iron complex 3a via 3c
For the series of complexes 1–3, the analysis of the 13
C
NMR chemical shifts of the Ca carbon atoms shows that
these resonances are very sensitive to the extension of the
alkynyl ligands. As the number of carbon atoms in the
p-system increases, the Ca signals are shifted downfield
from (d, ppm) 146.3 for 1 to 152.9–153.2 for 2a–c and
to 155.9–156.2 for 3a– c. This observation is in accord-
ance with the increase of the electron-withdrawing effect
of the organic carbon-rich ligand with the extension of its
p-system [32]. In organometallic complexes, as the length
of a carbon-rich ligand increases, its electron-withdraw-
ing effect on the metal increases and induces a stronger
p-back-bonding response from the metal center, the
intensity of which being also related to how electron
rich the metal is. Related effects have been observed for
the complexes Cp*(dppe)Fe–Cx–Fe(dppe)Cp* with
increasing x [33]. As a consequence, the cumulenic-type
valence bond formulation B (Scheme 5) should contrib-
ute to the description of the electronic structure of the
complexes, and as n increases, the weight of the structure
B increases. As already pointed out, this effect concerns
mainly the carbon atoms close to the metal centers
and apparently does not propagate along the p-system
[33].
The complexes containing two thiophene rings con-
nected by an ethyndiyl fragment were prepared follow-
ing a similar procedure (Scheme 4). The complex 2a
reacts with 6 in the presence of the Pd/Cu catalyst.
The reaction reaches completion after 48 h at 50 ꢁC
and provides a pink powder which contains 3b and the
complex Cp*(dppe)FeACBCA2,5-C4H2SACBCACB
CA2,5-C4H2SACBCAFe(dppe)Cp* 11. This side prod-
S
Fe
P
H +
I
Si(CH3)3
P
6
4
i
S
Fe
P
SiR3
P
2b, yield 77 %
2c, yield 82 %
The energy of the m(CBC) stretching modes corre-
sponding to the CC triple bond adjacent to iron slightly
decreases when the size of the carbon rich ligand in-
creases (Table 1). The frequencies for this CBC bond
stretch (CH2Cl2, cmꢀ1) decrease by 10 cmꢀ1 and 15
cmꢀ1 from 1 to 2c and from 1 to 3c, respectively. Such
behavior suggests a diminution of the bond order of
the CaBCb carbon–carbon triple bond as the p-electron
ii
S
Fe Cl
+
H
Si(CH(CH3)2)3
P
5
9
P
Scheme 3. Key reagents: (i) (Ph3P)2PdCl2, CuI, ((CH3)2CH)2NH; (ii)
NaBPh4, MeOH, KOBut.

´
S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
597
S
S
+
Fe
P
I
Si(CH3)3
H
i
P
6
2a
S
S
S
S
Fe
P
Si(CH3)3
+ 11
P
P
P
3b
S
S
Fe
P
H
3a, yield 70 %
iii
Fe
P
Si(CH(CH3)2)3
3c, yield 88 %
ii
S
S
+
Fe Cl
(H3C)3Si
Si(CH(CH3)2)3
P
5
P
10
Scheme 4. Key reagents: (i) (Ph3P)2PdCl2, CuI, ((CH3)2CH)2NH; (ii) NaBPh4, MeOH, THF, K2CO3, KOBut; (iii) THF, TBAF.
S
S
Fe
P
C
C
R
Fe C
P
C
R
P
P
n
n
A
B
Scheme 5.
system is extended. This is also in full agreement with a
contribution of the canonical form B (Scheme 5) in the
description of the electronic structures.
energy level of the HOMO increases with the extent of
the conjugation of the r-alkynyl ligand.
It can also be observed that the substitution of the
terminal alkyne of complex 4 by a ethynylthiophene
group decreases the FeII/FeIII redox potential by 0.13
V indicating that the presence of the thiophene ring on
the alkynyl ligand contributes to increase the energy le-
vel of the HOMO. In this respect, it can be observed that
the effect of a benzene ring at the same position is less
pronounced by 0.05 V [18]. However, the addition of
alkynyl or thiophene-alkynyl fragments on 1 has the
opposite effect, since the redox potentials of 2a–c and
3a–c are less negative than that of 1.
2.4. Cyclic voltammetry 2a–c, 3a and 3c
The cyclic voltammograms (CV) of the complexes
display a reversible one-electron wave (Table 2) in the
range 0.5/ꢀ0.5 V vs the standard calomel electrode
(SCE). This reversible process corresponds to the well-
known metal-centered Fe(II)/Fe(III) oxidation and it
indicates that the Fe(III) analogues are stable on the
Pt electrode. It appears that the nature of the terminal
i
group (H, Me3Si or Pr3Si) has almost no effect on the
redox potentials. Comparison of the redox potentials
of the complexes 2a–c and 3a–c with those of 1, shows
that the progressive extension of the p-system of the lig-
and increases the oxidation potentials indicating that the
2.5. Oxidation of 2a and 3c
As suggested by the CVs the oxidized forms of 2a–b
and 3a–c should be thermally stable. Accordingly, we

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S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
598
Table 1
FTIR data
Cmpd.
mCBC
Nujol
mCBC
CH2Cl2
mCBCAH
Nujol
mCBCAH
CH2Cl2
Ref.
1
2044
2040
[25]
2a
2090
2030b
2087
2028b
3289
3300
This work
2b
2c
3a
2132
2034b
2131
2029b
This work
This work
This work
2136
2029b
2130
2028b
2180
2100
2025b
2178
2101
2025b
3300
3300
3c
2180
2140
2030b
2179
2139
2025b
This work
4
1910b
[10]
[25]
1[PF6]
1977b
1965a
1963b
1939
2a[PF6]
3c[PF6]
1942
3277
3298
This work
This work
2182
2139
1947b
2183
2141
1947b
a
Shoulder.
CBC triple bond identified as adjacent to Fe.
b
Table 2
Electrochemical Data
Compound
E0
DEp
(ipa/ipc
)
Reference
1
ꢀ0.14
ꢀ0.08
ꢀ0.08
ꢀ0.09
ꢀ0.07
ꢀ0.07
ꢀ0.01
ꢀ0.09
0.09
0.70
0.80
0.07
0.07
0.07
0.10
0.07
1
1
[25]
2a
2b
2c
3a
3c
4
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[10]
1
1
1
0.8
1
12a
[13,18]
Potentials in CH2Cl2 (0.1 M [nBu4N][PF6], 20 ꢁC, Pt electrode, sweep rate 0.100 V sꢀ1) are given in V vs SCE; the ferrocene–ferrocenium couple
(0.460 V vs SCE) was used as an internal calibrant for the potential measurements.
a
Cp*(dppe)FeCBCAC6H5.
have reacted 2a and 3c with [(g-C5H5)2Fe][PF6] to gen-
erate the corresponding paramagnetic salts 2a[PF6] and
3c[PF6]. The complex 3c[PF6] was isolated in a pure
form as a thermally stable, dark red powder in 90%
yield. In contrast, complex 2a[PF6] was always obtained
as a mixture with a diamagnetic complex 2aH[PF6] in
the 3:2 ratio. The separation of 2a[PF6] and 2aH[PF6]
could not be achieved. In addition, the NMR character-
ization of 2aH[PF6] in the presence of the paramagnetic
compound 2a[PF6] was unsuccessful. In accordance with
the MS data, it appears that 2aH[PF6] differs from
2a[PF6] by only one hydrogen atom. As the IR spectrum
of 2aH[PF6] does not show an absorption characteristic
of vinylidene derivatives in the range 1600–1650 cmꢀ1, it
was assumed that the hydrogen atom was bound to the
carbon in the terminal position providing a complex
with a cumulene-type structure (Scheme 6). Mo¨ssbauer
H
H
S
PF-6
Fe C C
P
C C
P
2aH[PF6]
Scheme 6. Proposed structure for complex 2aH[PF6].

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S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
599
spectroscopy supports this assumption. Indeed, the
Mo¨ssbauer spectrum recorded at 80 K for the mixture
of 2a[PF6] and 2aH[PF6] displays two doublets in the
3:2 ratio. The parameters of these doublets are quite dif-
ferent (2a[PF6]: IS = 0.238 mm/s vs Fe, QS = 0.960 mm/
s; 2aH[PF6]: IS = 0.100 mm/s vs Fe, QS = 1.237 mm/s),
and consistent with the proposed structures for the
two compounds. The parameters of 2aH[PF6] are typical
of FeII complexes with an iron-carbon double bond, as
previously shown for many related compounds of the
Cp*(dppe)Fe family. The Mo¨ssbauer parameters of the
complex 2a[PF6] are typical for 17-electron low spin
FeIII derivatives and very close to those obtained for
compound 1[PF6] (IS = 0.227 mm/s vs Fe, QS = 0.974
mm/s).
A Mo¨ssbauer spectrum was also obtained at 80 K for
the complex 3c[PF6]. It shows a unique doublet
(IS = 0.236 mm/s vs Fe, QS = 0.918 mm/s) indicating
that the oxidation of 3c was quantitative. As expected,
these data are quite close to those obtained for 1[PF6]
and 2a[PF6]. For these three complexes, the IS values
are similar in the accuracy of the measurements. One
can note a small but significant and continuous de-
creases of the QS values from 1[PF6] to 2[PF6] and
3c[PF6]. This observation could be related to the varia-
tion of the metallic character of the HOMO as the size
of the electron p-system increases.
They display three features corresponding to the three
components of the g-tensor, as expected for a d5 low-
spin FeIII radical in a pseudo-octahedral geometry
(Table 3). In the case of the complex 3c[PF6] the two
low field features are split into 1:2:1 triplet by hyperfine
coupling with the two equivalent 31P nuclei. A similar
observation was previously reported for the related
compound 1[PF6]. The ESR parameters given Table 3
compare well with those of other mononuclear com-
plexes of the same series. Comparison of the data shows
that the giso and Dg tensors are significantly smaller for
the complexes containing thiophene rings (1[PF6],
2a[PF6], 3c[PF6]) than for those bearing a hydrogen
atom (4[PF6]) or a phenyl ring (12[PF6]) on the alkynyl
ligand. These experimental data suggest that one of the
effects of the thiophene rings should be to decrease the
metal character of the LUMO and the HOMO-LUMO
energy gap.
2.6. Optical spectroscopies
Solutions of the complexes 1–3 range from orange to
red as the length of the metal-alkynyl ligand increases.
As shown in Table 4, the FeII complexes, 1–3, present
two high energy absorption bands which can be attrib-
uted to intraligand (IL) p ! p* transitions of the Cp*
and dppe ligands. These bands have already been ob-
served for other complexes containing the Cp*(dppe)Fe
organometallic building block. However, in the cases of
The ESR spectra were run at 77 K in rigid glass
(CH2Cl2/C2H4Cl2) for samples of 2a[PF6] and 3c[PF6].
Table 3
ESR parameters for compounds 1[PF6], 2a[PF6] and 3c[PF6]
Cmpd
g1 (AP)
g2 (AP)
g3
giso
Dg
1[PF6]a
2a[PF6]
3c[PF6]
4[PF6]b
12[PF6]c
a
1.986 (16 G)
1.985
2.036 (14 G)
2.035
2.366
2.385
2.363
2.457
2.464
2.129
2.135
2.129
2.156
2.157
0.380
0.400
0.375
0.480
0.489
1.988 (14 G)
1.977
1.975
2.036 (13 G)
2.034
2.033
From [25].
b
c
From [10].
[Cp*(dppe)FeCBCAC6H5][PF6] (see [13]).
Table 4
UV-vis data and tentative assignment of the electronic transitions
Compound p ! p* k nm (10ꢀ3 e Mꢀ1 dm3 cmꢀ1
)
MLCT k nm (10ꢀ3 e Mꢀ1 dm3 cmꢀ1
)
LMCT k nm (10ꢀ3 e Mꢀ1 dm3 cmꢀ1
)
Reference
1
2a
233 (31.0), 273 (13.7)
242 (31.3), 300 (13.4)
248 (20.8), 300 (11.9)
274 (29.4), 250 (26.7)
230 (54.0), 350 (22.4)
230 (36.4), 348 (25.5)
273 (33.7), 402 (5.0)
362 (6.9)
432 (12.2)
439 (10.3)
440 (17.3)
490 (21.9)
491 (19.2)
434 (4.4)
502 (12.6)
[25]
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This work
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[25]
2b
2c
3a
3c
1[PF6]
3c[PF6]
736 (6.6)
584 (5.0), 884 (5.8)
230 (48.9), 262 (35.6), 388 (33.4)
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S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
600
Table 5
NIR absorption data of 1[PF6], 2a[PF6] and 3c[PF6]
Cmpd
Band
e (Mꢀ1 cmꢀ1
)
m (cmꢀ1
)
Dm
1
2
ðcmꢀ1
Þ
mA ꢀ mB (cmꢀ1
)
1[PF6]
A
B
106
10
5680
7625
2100
1620
1945
2a[PF6]
3c[PF6]
A
B
125
20
5560
7515
2400
1620
1955
A
B
210
20
6150
8090
2260
1800
1960
the complexes 1–3 their intensities are larger and depend
on the number of thienyl fragments present in the com-
pounds suggesting that p ! p* transitions of the C4H2S
ring should overlay with those of the ancillary ligands.
With reference to the electronic absorption studies of
monometallic complexes with similar structures like
Cp*(dppe)FeACBCAC6H5, [18], which show low en-
ergy absorptions in the range 340–450 nm, the low en-
ergy absorptions observed in the spectra of the
complexes 1–3 are attributed to dpFe ! p*(CBC) met-
al-to-ligand charge transfer transitions (MLCT). As
the number of alkynyl and thiophene fragments in-
creases, the MLCT transition is red shifted by ca. 80
nm from 1 to 2a–c and by ca. 50 nm from 2a–c to 3a–
c, while the intensities of the bands is increased.
The spectrum of FeIII cation 3c[PF6] displays, besides
the supposed MLCT band at 502 nm which is less intense
and slightly red-shifted with respect to 3c, two bands at
lower energies. These bands are characteristic of FeIII
complexes and may be attributed to ligand-to-metal
charge transfer (LMCT) transitions from low-lying lig-
and-based molecular orbitals (MO) to the half-filled
HOMO, which is mainly metallic in character. A similar
transition was also observed for the related complexes
[15], but, in general, only one LMCT band was observed
at a higher energy. As a result, the extension of the p-sys-
tem of the carbon rich ligand increases the number of
LMCT transitions and produces a red shift for the lower
energy band.
The spectra of FeII complexes 1–3 do not present any
absorption bands in the NIR range. In contrast, the
NIR spectra of the corresponding FeIII congeners con-
tain absorption bands of weak intensities (Table 5).
While the more intense bands are located at very similar
energies for 1[PF6] and 2a[PF6], with an extinction coef-
ficient close to 100 Mꢀ1 dmꢀ3 cmꢀ1, like all the FeIII
complexes of the Cp*(dppe)Fe series that we have previ-
ously characterized, the complex 3c[PF6] displays a
more intense (e = 210 Mꢀ1 lꢀ1 cmꢀ1), red shifted absorp-
tion at ca. 6150 cmꢀ1 [14,34]. These bands correspond to
forbidden ligand field transitions specific to the
Cp*(dppe)Fe fragment. In addition, the NIR spectra
of the three complexes 1[PF6], 2a[PF6] and 3c[PF6] show
a second, very weak absorption band at ca. 2000 cmꢀ1
lower in energy, corresponding to the resolution of the
vibronic coupling with the m(FeACBC) stretching
modes of vibration (see Tables 1 and 2).
3. Conclusions
In this contribution, we have reported efficient syn-
thetic access to new organoiron(II) containing thiophene
acetylide fragments and have fully characterized these
species. We have also prepared the relative organo-
iron(III) complexes and shown that these radicals are
thermally stable. However, when the carbon-rich ligands
are not substituted by a bulky terminal group, the spe-
cies are very reactive and could not be isolated in pure
form. Despite the presence of a ligand containing an ex-
tended p-electron system with up to fourteen sp or sp2
hybridized carbon atoms bound to the 17-electron d5
iron center, these complexes can be regarded as metal
centered radicals. The spectroscopic data revealed only
a weak increase of the carbon character of the SOMO.
4. Experimental
4.1. General data
All manipulations were carried out under an argon
atmosphere using Schlenk techniques or in a Jacomex
532 dry-box filled with nitrogen. Routine NMR spectra
were recorded using a Bruker DPX 200 spectrometer.
High field NMR spectra experiments were performed
on a multinuclear Bruker WB 300 instrument. Chemical
shifts are given in parts per million relative to tetrameth-
ylsilane (TMS) for 1H and 13C NMR spectra, and
H3PO4 for 31P NMR spectra. X-Band ESR spectra were
recorded on a Bruker ESP-300E spectrometer. An Air
Products LTD-3-110 liquid helium transfer system was
attached for the low-temperature measurements. Cyclic
voltammograms were recorded using a PAR 263 instru-
ment with a SCE reference electrode and ferrocene as
internal calibrant (0.460 V). The 57Fe Mo¨ssbauer spectra
were obtained by using a constant acceleration spec-
trometer previously described with a 50 mCi 57Co source
in a Rh matrix. The sample temperature was controlled
by a Oxford MD306 cryostat and a Oxford ITC4 tem-

´
S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
601
perature controller. Computer fitting of the Mo¨ssbauer
data to Lorenzian line shapes was carried out with a pre-
viously described computer program [35,36]. The isomer
shift values are reported with respect to iron foil at 298
K and are not corrected for the temperature-dependent
second-order Doppler shift. The Mo¨ssbauer sample cell
consists of a 2 cm diameter cylindrical plexiglass holder.
Elemental analyses were performed at CRMPO, Re-
nnes, France. LSI-MS analyses were performed at
CRMPO on a high-resolution MS/MS ZabSpec TOF
Micromass spectrometer (8 kV). The organic compound
2-iodo-5-(trimethylsilylethynyl)thiophene [37] and the
organometallic complexes Cp*(dppe)FeCl [38] and
Cp*(dppe)FeCBCH [10] were prepared as previously
described.
uid (0.977 g, 3.4 mmol, 90%). Anal. Calc. for C17H24SSi:
1
C, 70.77; H 8.38. Found: C, 70.45; H, 8.23. NMR H
(CDCl3, 200 MHz, 25 ꢁC, d, ppm) 7.12 (d, 1H,
3
3JHH = 3.8 Hz, C4H2S), 7.08 (d, 1H, JHH = 3.8 Hz,
C4H2S), 3.36 (s, 1H, CBCAH), 1.16 (s, 21H,
Si(CH(CH3)2)3). NMR 13C (CDCl3, 50 MHz, 25 ꢁC, d,
1
2
ppm) 133.1 (ddd, JCH = 171.8 Hz, JCH = 6 Hz,
4JCH = 2 Hz, C4), 132.4 (dd, JCH = 172 Hz, JCH = 6
Hz, C3), 125.7 (m, C2), 123.4 (m, C5), 98.9 (d,
3JCH = 3 Hz, CBCASi(CH(CH3)2)3), 97.4 (m,
CBCASi(CH(CH3)2)3), 82.3 (d, JCH = 255 Hz, CBC-
H), 76.8 (m, JCH = 51 Hz, JCH = 4 Hz, CBCAH),
1
2
1
2
3
1
19.1 (q, JCH = 126 Hz, Si(CH(CH3)2)3), 11.7 (d,
1JCH = 119 Hz, Si(CH(CH3)2)3). FTIR (Nujol, KBr, m,
cmꢀ1): = 3310 (s, C-H), 2144 (s, CBCASi(CH(CH3)2)3),
2104 (s, CBCAH).
4.2. ((CH3)2HC)3SiACBCA2,5-C4H2SACBCASi(CH3)3
(8)
4.4. ((CH3)2HC)3SiACBCA2,5-C4H2SACBCA2,5-C4H2SA
CBCASi(CH3)3 (10)
In a Schlenk tube, 0.520 g (1.70 mmol) I-2,5-
(C4H2S)ACBCASi(CH3)3 6, 20 mL of THF, 0.026 g
(0.136 mmol) of CuI, 0.048 g (0.068 mmol) of
(Ph3P)2PdCl2, 5 mL of diisopropylamine and 0.43 mL
(1.87 mmol) of (triisopropylsilyl)acetylene were succes-
sively added. The resulting solution was stirred for 16
h at 20 ꢁC. Then 20 mL of water were added, and the
mixture was extracted with CH2Cl2. The organic phase
was washed with a saturated solution of NaCl in water
and dried over magnesium sulphate, filtered, and evapo-
rated to provide a crude residue for purification. Col-
umn chromatography on silica gel eluted with hexane
provided 0.551 g of 8 as an orange yellow liquid (1.53
mmol, 90%). Anal. Calc. for C20H32SSi2: C, 66.60; H
In a Schlenk tube 0.935 g (3.05 mmol) of 6, 30 mL of
THF, 0.046 g (0.24 mmol) of CuI, 0.086 g (0.122 mmol)
of (PPh3)2PdCl2, 5 mL of diisopropylamine, and 0.970 g
(3.36 mmol) of 9 were successively added. The solution
was stirred for 16 h at 20 ꢁC, and 50 mL of distilled
water were added. After extraction with dichlorometh-
ane and washing with water, the organic extract was
dried over magnesium sulfate and evaporated to provide
a crude residue which was separated by column chroma-
tography on silica gel eluted with hexane. Evaporation
of the solvent under reduced pressure provide a yellow
liquid identified as 10 (0.820 g, 1.76 mmol, 58%). Anal.
Calc. for C26H34S2Si2: C, 72.25; H 8.08. Found: C,
1
1
8.94. Found: C, 66.48; H, 8.67. H NMR (CDCl3, 200
72.07; H, 8.03. H NMR (CDCl3, 200 MHz, 25 ꢁC, d,
MHz, 25 ꢁC, d, ppm) 7.07 (s, 2H, C4H2S), 1.16 (m,
21H, Si(CH(CH3)2)3), 0.29 (s, 9H, Si(CH3)3). 13C
NMR (CDCl3, 50 MHz, 25 ꢁC, d, ppm) 132.6 (dd,
1JCH = 172 Hz, 2JCH = 6 Hz, C4), 132.4 (dd,
ppm) 7.12 (s, 4H, C4H2S), 1.15 (s, 21H, Si(CH(CH3)2)3),
0.28 (s, 9H, Si(CH3)3). 13C NMR (CDCl3, 75 MHz, 25
1
2
ꢁC, d, ppm) 133.0 (dd, JCH = 173 Hz, JCH = 6 Hz,
1
C4 ), 132.8 (dd, JCH = 172 Hz, JCH = 4.8 Hz, C3),
2
0
2
1
132.5 (dd, JCH = 173 Hz, JCH = 6 Hz, C4,3 ), 126.1,
2
1JCH = 172 Hz, JCH = 6 Hz, C3), 125.4 (m, C2), 124.7
0
0 0
C2,2 ,5,5 ), 101.1 (m,
(m, C5), 100.1 (m, CBCASi(CH3)3), 99.2 (m,
125.6, 124.3, 123.9 (4m,
CBCASi(CH(CH3)2)3),
97.4
(m,
CBCASi(CH
CBCASi(CH3)3), 99.1 (m, CBCASi(CH(CH3)2)3), 98.0
(m, CBCASi(CH(CH3)2)3), 97.3 (m, CBCASi(CH3)3),
(CH3)2)3), 97.2 (m, CBCASi(CH3)3), 19.1 (q,
1JCH = 126 Hz, Si(CH(CH3)2)3), 11.7 (d, JCH = 119
87.2 (m, CBC), 86.9 (m, CBC), 19.1 (qm, JCH = 126
Hz, Si(CH(CH3)2)3), 11.7 (dm, JCH = 123 Hz,
1
1
1
Hz, Si(CH(CH3)2)3), 0.20 (q, JCH = 121 Hz, Si(CH3)3).
1
FTIR (Nujol, KBr, m, cmꢀ1) 2146 (s, CBC).
Si(CH(CH3)2)3), 0.2 (q, 1JCH = 126 Hz, Si(CH3)3). FTIR
(Nujol, KBr, m, cmꢀ1) 2144 (s, CBC).
4.3. ((CH3)2HC)3SiACBCA2,5-C4H2SACBCH (9)
4.5. Cp*(dppe)FeACBCAC4H2SACBCH (2a)
In a flask 1.39 g (3.82 mmol) of 8 were dissolved in 40
mL of methanol before 0.635 g (4.59 mmol) of K2CO3
was added. The resulting mixture was stirred for 2 h at
20 ꢁC, and the solvent was removed under reduced pres-
sure. The crude residue was washed with diethyl ether
(50 mL). The organic solution was washed with distilled
water (60 mL), dried over magnesium sulphate, filtered
and evaporated to provide 9 as a pure orange yellow liq-
(A). In a Schlenk tube, 0.632 g of [Cp*(dppe)FeACB
CA2,5-(C4H2S)ACBCASi(CH3)3] (2b, 0.80 mmol) and
0.110 g of K2CO3 (0.80 mmol) were dissolved in 50
mL of a MeOH/THF mixture (v/v = 1:1). The reaction
mixture was stirred at 20 ꢁC for 12 h and the solvents
were removed in vacuo. The solid residue was extracted
with toluene (3 · 10 mL) and the solvent removed in

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S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
602
1
(m, C2), 133.3 (dd, JCH = 167 Hz, JCH = 6 Hz, C4),
2
vacuum. The resulting orange powder was washed with
pentane (3 · 5 mL) and dried under vacuum. The com-
plex 2a was obtained as pure and thermally stable or-
ange microcrystals (0.570 g, 0.79 mmol, 99%).
1
124.2 (dd, JCH = 168 Hz, JCH = 5 Hz, C3), 116.2 (dd,
2
3
2JCH = 13 Hz, JCH = 5 Hz, C5), 112.0 (s, Cb), 100.6
3
(d, JCH = 4 Hz, Ca ), 95.8 (m, Cb ), 88.4 (s, C5(CH3)5),
0
0
1
30.9 (m, JCP = 23 Hz, CH2dppe), 10.3 (q, JCH = 126
1
(B). To a THF solution (5 mL) of 2c (1.000 g, 1.14
mmol), 0.23 mL of 1M solution of TBAF (0.23 mmol)
was added. The resulting mixture was stirred at 20 ꢁC
for 16 h before the solvent was removed under reduced
pressure. The crude residue was extracted with toluene
(3 · 10 mL) and filtered on a silica pad (5 cm). Removal
of the solvent in vacuum, washing with pentane (3 · 5
mL) and drying under vacuum yielded 0.681 g of com-
plex 2a (0.95 mmol, 83%). Anal. Calc. for C44H42FeP2S:
1
Hz, C5(CH3)5), 0.2 (q, JCH = 118 Hz, Si(CH3)3).
{1H}31P NMR(C6D6, 81 MHz, 25 ꢁC, d, ppm) 100.6
(s, dppe). FTIR (KBr/Nujol, m, cmꢀ1) 2132 (m, CBC),
2034 (s, CBC).
4.7. Cp*(dppe)FeACBCA2,5-C4H2SACBCASi(CH-
(CH3)2)3 (2c)
1
C, 73.33; H 5.87. Found: C, 73.61; H, 5.86. H NMR
(C6D6, 200 MHz, 25 ꢁC, d, ppm) 7.91–7.03 (m, 20H,
Ph), 7.07 (d, 1H, JHH = 3,8 Hz, C4H2S/H4), 6.44 (d,
In a Schlenk tube, 1.000 g of the complex
Cp*(dppe)FeCl (5, 1.60 mmol), 0.602 g of NaBPh4
3
(1.76 mmol) and 40 mL of methanol were introduced
before adding 0.507
3
1H, JHH = 3,8 Hz, C4H2S/H3), 2.9 (s, 1H, BCH),
g
of ((CH3)2CH)3SiACB
2.51–1.76 (2m, 4H, CH2dppe), 1.46 (s, 15H, C5(CH3)5).
13C NMR(C6D6, 75 MHz, 25 ꢁC, d, ppm) 152.9 (t,
2JCP = 38 Hz, Ca), 139.5–127.4 (m, Ph), 134.7 (m, C2),
CA(C4H2S)ACBCAH in THF (1.76 mmol in 10 mL
of THF). The mixture was stirred at 20 ꢁC for 16 h
and then 0.197 g of KOtBu was added (1.76 mmol).
After stirring one additional hour, the solvents were
removed in vacuum. The solid residue was extracted
with dichloromethane (3 · 20 mL), the solvent re-
moved in vacuum, the residue washed with cold pen-
tane (3 · 10 mL, ꢀ60 ꢁC). After drying in vacuum,
1.148 g of an orange powder of the compound 2c
were obtained (1.31 mmol, 82%). MS (positive LSI,
m-NBA, m/z), 876 ([Cp*(dppe)FeACBCA2,5-C4H2S
ACBCASi(CH(CH3)2)3]+, 66%), 741 ([(dppe)FeACB
1
2
133.5 (dd, JCH = 168 Hz, JCH = 6 Hz, C4), 124.1 (dd,
2
1JCH = 168 Hz, JCH = 6 Hz, C3), 115.0 (m, C5), 111.9
3
(t, JCP = 2 Hz, Cb), 88.4 (s, C5(CH3)5), 79.2 (d,
1
2
JCH = 252 Hz, Cb ), 79.0 (dd, JCH = 50 Hz, JCH = 4
3
0
1
0
Hz, Ca ), 30.9 (m, JCP = 23 Hz, CH2dppe), 10.3 (q,
1JCH = 126 Hz, C5(CH3)5). NMR {1H}31P (C6D6, 81
MHz, 25 ꢁC, d, ppm) 100.7 (s, dppe). FTIR (KBr/Nujol,
m, cmꢀ1) 3289 (m, BCAH), 2090 (w, CBC), 2030 (s,
CBC).
CA2,5-C4H2SACBCASi(CH(CH3)2)3]+,
3%),
589
4.6. Cp*(dppe)FeACBCA2,5-C4H2SACBCSi(CH3)3
(2b)
([Cp*(dppe)Fe]+, 100%). HRMS (positive LSI, m-
NBA, m/z) calc.: 876.3166, found: 876.3184. 1H
NMR (C6D6, 200 MHz, 25 ꢁC, d, ppm) 7.91–7.01
3
To a Schlenk tube containing 0.500 g of the complex
Cp*(dppe)FeACBCH (4, 0.82 mmol), 0.057 g of
(PPh3)2PdCl2 (0.08 mmol) and 0.032 mg of CuI (0.16
mmol) 40 mL of di-iso-propylamine were added. With
(m, 20H, Ph), 7.08 (d, 1H, JHH = 3.8 Hz, C4H2S/
3
H4), 6.42 (d, 1H, JHH = 3.8 Hz, C4H2S/H3), 2.51–
1.77 (2m, 4H, CH2dppe), 1.46 (s, 15H, C5(CH3)5),
1.20 (m, 21H, Si(CH(CH3)2)3). 13C NMR (50 MHz,
2
´
stirring, 0.505 g of 2-iodo-(5-trimethylsilylethynyl)thi-
ophene was added to the mixture, which was warmed
´
C6D6, 25 ꢁC, d, ppm) 153.2 (t, JCP = 38 Hz, Ca),
139.7–127.5 (m, Ph), 134.7 (m, C2), 133.4 (dd,
`
for 24 h at 70 ꢁC. After removal of the solvent under re-
duce pressure, the crude residue was extracted with tol-
uene (3 · 10 mL) filtered on a celite pad and evaporated
to dryness. Repeated washings with cold pentane (3 · 5
mL, ꢀ40 ꢁC) and drying in vacuum, yielded 2b as a pure
orange powder (0.501 g, 0.63 mmol, 77%). Anal. Calc.
for C47H50FeP2SSi: C, 71.20; H, 6.36. Found: C,
70.65; H, 6.29. MS (positive LSI, m-NBA, m/z), 792
([Cp*(dppe)FeACBCA2,5-C4H2SACBCSi(CH3)3]+,
66%), 589 ([Cp*(dppe)Fe]+, 100%). HRMS (positive
1JCH = 167 Hz, 2JCH = 6 Hz, C4), 124.2 (dd,
2
1JCH = 168 Hz, JCH = 6 Hz, C3), 116.0 (m, C5),
3
112.4 (s, Cb), 102.6 (d, JCH = 4 Hz, Ca ), 92.2 (s,
0
1
Cb ), 88.5 (s, C5(CH3)5), 31.1 (m, JCP = 23 Hz,
0
1
CH2dppe), 19.2 (q, JCH = 126 Hz, Si(CH(CH3)2)3),
1
12.0 (d, JCH = 120 Hz, Si(CH(CH3)2)3), 10.4 (q,
1JCH = 126 Hz, C5(CH3)5). {1H} 31P NMR (C6D6,
81 MHz, 25 ꢁC, d, ppm) 100.8 (s, dppe). FTIR
(KBr/Nujol, m, cmꢀ1) 2136 (m, CBC), 2029 (s, CBC).
1
LSI, m-NBA, m/z) calc.: 792.2227, found: 792.2225. H
NMR (C6D6, 200 MHz, 25 ꢁC, d, ppm) 7.90–7.01 (m,
20H, Ph), 7.13 (d, 1H, JHH = 3.8 Hz, C4H2S/C4), 6.42
4.8. Cp*(dppe)FeACBCA2,5-C4H2SACBCA20,50-C4H2SA
CBCH (3a)
3
3
(d, 1H, JHH = 3.8 Hz, C4H2S/C3), 2.50–1.74 (2m, 4H,
CH2dppe), 1.45 (s, 15H, C5(CH3)5), 0.20 (s, 9H,
In a Schlenk tube, a 0.600 g of the complex [Cp* (dppe)
FeACBCA2,5-(C4H2S)ACBCA20,50-(C4H2S)ACBC
ASi(CH(CH3)2)3] (3c, 0.61 mmol) was dissolved in 40 mL
of THF before adding 122 lL of a 1M solution of TBAF
Si(CH3)3). NMR 13C (C6D6, 75 MHz, 25 ꢁC, d, ppm)
153.2 (t, JCP = 41 Hz, Ca), 139.5–127.4 (m, Ph), 134.7
2

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S. Roue, C. Lapinte / Journal of Organometallic Chemistry 690 (2005) 594–604
603
in THF (0.12 mmol). The mixture was stirred at 20 ꢁC for
16 h and the solvent was removed. The crude residue was
extracted with toluene (3 · 10 mL) and filtered over a sil-
ica pad. Removal of the solvent under reduce pressure,
washing with cold pentane (2 · 10 mL, ꢀ40 ꢁC) and evap-
oration to dryness yielded 0.352 g of 3a isolated as a red
powder (0.43 mmol, 70%). Anal. Calc. For
C50H44FeP2S2: C, 72.63; H, 5.36; S, 7.76. Found: C,
72.84; H, 5.28; S, 7.31. MS (positive LSI, m-NBA, m/z),
CBCASi(CH(CH3)2)3]+, 96%), 847 ([(dppe)FeACB
CA2,5-C4H2SACBCA2,5-C4H2SACBCASi(CH(CH3)2)3]+,
6%), 589 ([Cp*(dppe)Fe]+, 67%). HRMS (positive LSI,
m-NBA, m/z) calc.: 982.3043, found: 982.3045. 1H
NMR (C6D6, 200 MHz, 25 ꢁC, d, ppm) 7.91-6.99 (m,
3
20H, Ph), 7.04 (d, 1H, JHH = 3.8 Hz, C4H2S/H4), 6.77
3
(d, 1H, JHH = 3.8 Hz, C4H2S/H3 ), 6.66 (d, 1H,
0
3
3JHH = 3.8 Hz, C4H2S/H4), 6.48 (d, 1H, JHH = 3.8 Hz,
C4H2S/H3), 2.49–1.75 (2m, 4H, CH2), 1.46 (s, 15H,
C5(CH3)5), 1.13 (m, 21H, Si(CH(CH3)2)3). 13C NMR
826
([Cp*(dppe)FeACBCA2,5-C4H2SACBCA2,
5-C4H2SACBCH]+, 100%), 691 ([(dppe)FeACBC
A2,5-C4H2SACBCA2,5-C4H2SACBCH]+, 7%), 589
([Cp*(dppe)Fe]+, 67%). HRMS (positive LSI, m-NBA,
(C6D6, 50 MHz, 25 ꢁC, d, ppm) 156.2 (t, JCP = 38 Hz,
Ca), 139.6–127.6 (m, Ph), 135.6 (s, C2), 133.6 (dd,
2
2
1
1JCH = 168 Hz; JCH = 6 Hz, C4), 133.1 (dd, JCH
=
171 Hz, JCH = 6 Hz, C4), 131.4 (dd, JCH = 172
1
2
1
m/z) calc.: 826.1709, found: 826.1707. H NMR (C6D6,
200 MHz, 25 ꢁC, d, ppm) 7.91–7.05 (m, 21H, Ph +
Hz,2JCH = 6 Hz, C3 ), 126.1 (m, C2 ), 124.6 (dd,
0
0
3
C4H2S/H4), 6.73 (d, 1H, JHH = 3.8 Hz, C4H2S/H3 ),
2
2
1JCH = 168 Hz, JCH = 6 Hz, C3), 124.3 (dd, JCH = 12
0
3
6.65 (d, 1H, JHH = 3.8 Hz, C4H2S/H4 ), 6.48 (d, 1H,
3
2
Hz, JCH = 6 Hz, C5 ), 114.9 (dd, JCH = 12 Hz,
0
0
3JHH = 3.8 Hz, C4H2S/H3), 2.79 (s, 1H, BCAH), 2.49–
3JCH = 6 Hz, C5), 112.6 (s, Cb), 100.3 (d, JCH = 4 Hz,
3
1.75 (2m, 4H, CH2) 1.46 (s, 15H, C5(CH3)5). 13C NMR
3
Ca ), 96.8 (s, Cb ), 90.3 (d, JCH = 4 Hz, Ca ), 88.6 (s,
00
00
0
2
3
C5(CH3)5), 84.2 (d, JCH = 4 Hz, Cb ), 31.1 (m,
0
(C6D6, 75 MHz, 25 ꢁC, d, ppm) 155.9 (t, JCP = 38 Hz,
Ca), 139.6–127.7 (m, Ph), 135.6 (s, C2), 133.6 (dd,
1JCP = 23 Hz, CH2dppe), 19.0 (q, JCH = 126 Hz,
1
1JCH = 168 Hz, JCH = 6 Hz, C4), 133.3 (dd, JCH = 171
Si(CH(CH3)2)3),
11.8
(d,
1JCH = 119
Hz,
2
1
Hz, 2JCH = 6 Hz, C4 ) 131.2 (dd, JCH = 172 Hz,2JCH = 6
Si(CH(CH3)2)3), 10.5 (q, JCH = 126 Hz, C5(CH3)5).
{1H} 31P NMR (81 MHz, C6D6, 25 ꢁC, d, ppm) 100.6
(s, dppe). FTIR (KBr/Nujol, m, cmꢀ1) 2180 (w, CBC),
2140 (m, CBC), 2030 (s, CBC).
1
1
0
1
Hz, C3 ), 126.4 (m, C2 ), 124.5 (dd, JCH = 168 Hz,
0
0
2JCH = 6 Hz, C3), 123.0 (dd, 2JCH = 12 Hz, 3JCH = 6 Hz,
2
C5 ), 114.8 (dd, JCH = 12 Hz, JCH = 6 Hz, C5), 112.6
3
0
3
(s, Cb), 90.3 (d, JCH = 4 Hz, Ca ), 88.5 (s, C5(CH3)5),
0
3
83.9 (d, JCH = 4 Hz, Cb ), 82.5 (d, JCH = 255 Hz, Cb ),
1
0
00
2
76.9 (dd, JCH = 51 Hz, JCH = 4 Hz, Ca ), 31.2 (m,
3
00
Acknowledgement
1
1JCP = 23 Hz, CH2dppe), 10.3 (q, JCH = 126 Hz,
C5(CH3)5). {1H}31P NMR (C6D6, 81 MHz, 25 ꢁC, d,
ppm) 100.6 (s, dppe). FTIR (KBr/Nujol, m, cmꢀ1) 3300
(m, BCAH), 2180 (m, CBC), 2100 (w, CBC), 2025 (s,
CBC).
We thank A. Mari (LCC, Toulouse) for Mo¨ssbauer
measurements. We are indebted to ANRT and Labora-
toires Standa (Caen) for financial support and a thesis
grant to S.R.
4.9. Cp*(dppe)FeACBCA2,5-C4H2SACBCA2,5-C4H2SA
CBCASi(CH(CH3)2)3 (3c)
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