Convenient routes to mono- and dinuclear (C5Me5)iron(II) complexes bearing acyl, alkynyl, aryl and thienyl ligands

Article abstract of DOI:10.1016/S0022-328X(99)00578-1

Treatment of the cations [Fe(C₅Me₅)(CO)₂(L)][PF₆] (1a, L=CO; 1c, L=PPh₃) with LiCCSiMe₃ gives the corresponding acyl derivatives [Fe(C₅Me₅)(CO)₂{C(O)CCSiMe<

Full text of DOI:10.1016/S0022-328X(99)00578-1

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 595 (2000) 81–86
Convenient routes to mono- and dinuclear (C5Me5)iron(II)
complexes bearing acyl, alkynyl, aryl and thienyl ligands
Jens Kiesewetter, Ge´raldine Poignant, Ve´ronique Guerchais *
UMR 6509 CNRS-Uni6ersite´ de Rennes 1: ‘Organome´talliques et Catalyse: Chimie et Electrochimie Mole´culaires’, Uni6ersite´ de Rennes 1,
Campus de Beaulieu, 35042 Rennes Cedex, France
Received 3 August 1999; accepted 30 September 1999
Abstract
Treatment of the cations [Fe(C5Me5)(CO)2(L)][PF6] (1a, L=CO; 1c, L=PPh3) with LiCꢀCSiMe3 gives the corresponding acyl
derivatives [Fe(C5Me5)(CO)2{C(O)CꢀCSiMe3}] (2) and [Fe(C5Me5)(CO)(PPh3){C(O)CꢀCSiMe3}] (4), respectively. The nucleophile
adds at the carbonyl ligand, but in the case of 1a, competitive attack occurs at the metal centre leading to the formation of the
alkynyl complex [Fe(C5Me5)(CO)2{CꢀCSiMe3}] (3). The latter species is formed as the only product from the acetonitrile complex
[Fe(C5Me5)(CO)2(CH3CN)][PF6] (1b), under the same conditions. Similarly, the dinuclear bis(acyl) complex [Fe(C5Me5)(CO)2{m-
h1,h1%-C(O)-]2(2,2%-C4H2S) (6) is obtained from 1a by using 0.5 equivalents of the dilithium salt 2,2%-Li2C4H2S/TMEDA. Complete
decarbonylation by UV irradiation of 3 or 6 in the presence of dppe affords the corresponding disubstituted complexes
[Fe(C5Me5)(dppe){CꢀCSiMe3}] (5) and [Fe(C5Me5)(dppe)]2{m-h1,h1%-2,2%-C4H2S} (7), respectively. Complexes [Fe(C5Me5)-
(CO)2{CH(OMe)C6H4-p-Br}] (9) and [Fe(C5Me5)(CO)2{CH(OMe)-2-C4H3S}] (10) are synthesised from the methoxycarbene
complex [Fe(C5Me5)(CO)2(ꢁCHOMe)][PF6] (8); the nucleophilic addition of the organolithium reagents occurs at the carbene
ligand. Dinuclear complexes such as the thiophene derivative [Fe(C5Me5)(CO)2{m-h1,h1%-CHOMe-]2(2,2%-C4H2S) (11) and the
biphenylene complex [Fe(C5Me5)(CO)2{m-h1,h1%-CHOMe-]2(p-C6H4-C6H4) (12) are obtained by using the appropriate dilithiated
nucleophiles. Protonolysis of 12 gives the bis(carbene) complex [Fe(C5Me5)(CO)2{m-h1,h1%-CH-]2(p-C6H4-C6H4) (13), which is
stable at −50°C. © 2000 Elsevier Science S.A. All rights reserved.
Keywords: Iron; Unsaturated ligand; Dinuclear; Carbene; Aromatic bridge
1. Introduction
decarbonylation
affords
the
vinyl
complexes
[Fe(C5Me5)(CO)2{CHꢁCR1R2}] [3]. However, activa-
tion of terminal alkynes is only effective for
[Fe(C5Me5)(dppe)(Cl)], since no reaction is observed in
the case of the dicarbonyl analogue [4]. This led us to
develop synthetic routes to [Fe(C5Me5)(L)2] (L=CO,
or L2=dppe) organo-iron derivatives possessing differ-
ent unsaturated ligands such as acyl, alkynyl, aryl and
thienyl groups. We report here the reactivity of the
cations [Fe(C5Me5)(CO)2(L)][PF6] (L=CO [5]; L=
PPh3 [5]; L=CH3CN [5]; L=CHOMe [6]) towards
organolithium reagents. This strategy gives access to
dinuclear complexes, and in particular complexes con-
taining a bis(carbene) and a thiophene bridge. The
electron-rich dppe-substituted analogues are then acces-
sible by photochemical decarbonylation in the presence
of dppe. These compounds are not available directly,
since the reaction of [Fe(C5Me5)(dppe)(L)]+ complexes
Complexes containing an unsaturated ligand such as
a vinyl, an alkynyl or an aromatic group constitute an
important class of compounds, especially as building
blocks for the synthesis of di- or polymetallic complexes
linked by a p-conjugated system. Unsaturated bridges
can provide a facile pathway for electron delocalisation
between metal centres, and in this context, the
[Fe(C5Me5)] fragment is very promising [1]. However,
the preparation of complexes with hydrocarbon ligands
having sp2 and sp-carbon bonded to the iron are not
straightforward [1,2]. We have previously shown that
activation of 2-alkyn-1-ols by [Fe(C5Me5)(CO)2(H2O)]+
opens a route to a,b-unsaturated acyl complexes
[Fe(C5Me5)(CO)2{C(O)CHꢁCR1R2}], and subsequent
* Corresponding author.
0022-328X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00578-1

82
J. Kiesewetter et al. / Journal of Organometallic Chemistry 595 (2000) 81–86
with organolithium reagents leads to electron-transfer
reactions [1].
(2) and the alkynyl derivative [Fe(C5Me5)(CO)2{Cꢀ
CSiMe3}] (3) in a 60:40 ratio (Scheme 1). These two
compounds are readily separated by column chro-
matography. These products can be well-differentiated
by NMR spectroscopy. The resonances of the alkynyl
substituent appear at l 106.20 (CꢀCSiMe3) and 100.00
(CꢀCSiMe3) for 2, whereas they are located at l 131.32
(CꢀCSiMe3) and 118.57 (CꢀCSiMe3) for 3 in the 13C-
NMR spectra. Moreover, the acyl group of 2 gives rise
to a characteristic low-field signal at l 252.78. The
formation of 2 and 3 results from nucleophilic attack at
the carbonyl ligand or at the metal centre of 1a, respec-
tively. Complex 3 is readily obtained as the only
product from the acetonitrile complex [Fe(C5Me5)-
(CO)2(CH3CN)][PF6] (1b) (Scheme 1). The phosphine-
substituted complex [Fe(C5Me5)(CO)(PPh3){C(O)Cꢀ
CSiMe3}] (4), formed under the same reaction condi-
tions from [Fe(C5Me5)(CO)2(PPh3)][PF6] (1c), is iso-
lated as an orange powder in 51% yield after
purification by chromatography (Scheme 1). The 13C-
NMR spectrum exhibits two signals at l 106.53 (d,
2J(C–P)=7 Hz, CꢀCSiMe3) and 96.31 (s, CꢀCSiMe3),
in agreement with the proposed structure.
2. Results and discussion
2.1. Reacti6ity of the cations [Fe(C5Me5)(CO)2(L)][PF6]
(L=CO, PPh3, CH3CN)
Treatment of complex [Fe(C5Me5)(CO)3][PF6] (1a) at
−80°C (THF) with LiCꢀCSiMe3 affords a mixture of
the acyl complex [Fe(C5Me5)(CO)2{C(O)CꢀCSiMe3}]
The dppe complex [Fe(C5Me5)(dppe){CꢀCSiMe3}]
(5) is then obtained from the dicarbonyl derivative 3,
under UV irradiation (95:5 toluene–acetonitrile) in the
presence of one equivalent of dppe (Scheme 2). The two
carbon atoms of the alkynyl ligand are located at l
2
162.89 (t, J(C–P)=37 Hz, Ca) and l 123.71 (Cb) in
the 13C-NMR spectrum. The w(CꢀC) absorption band
is observed at 1981 cm−1 in the IR spectrum (CH2Cl2).
This strategy can be extended to the preparation of
dinuclear complexes. Addition of 0.5 equivalents of
2,2%-Li2C4H2S/TMEDA to 1a leads to the formation of
the bis(acyl) derivative [Fe(C5Me5)(CO)2{m-h1,h1%-C(O)-
]2(2,2%-C4H2S) (6), which is isolated as a yellow pow-
der in 68% yield. The dppe-substituted complex
[Fe(C5Me5)(dppe)]2{m-h1,h1%-2,2%-C4H2S} (7) is then ob-
tained after decarbonylation of 6 by UV irradiation in
the presence of dppe (Scheme 3). Compound 7 is ob-
tained as a thermally stable black solid in 80% yield.
The cyclic voltammogram (Pt electrode, THF, 0.1 M
[nBu4N][PF6], 0.1 V s−1) of 7 (Fig. 1) exhibits two
Scheme 1.
Scheme 2.
reversible one-electron processes at E°= −0.592 V
1
versus SCE and E°= −0.038 V versus SCE with iap/
2
icp=1. The calculated comproportionation constant
Kc=2.36×109 (from ꢀE°−E°ꢀ=0.554) is quite large
1
2
compared with that of the octatetraynediyl derivative
[Fe(C5Me5)(dppe)]2{m-C8} (Kc=2×107) [7]. These pre-
liminary studies indicate that the mixed-valence Fe(II)–
Fe(III) complex should be isolable, and its electronic
properties deserve to be examined [8]. No such example
has been studied so far for thiophene-bridged dinuclear
complexes.
Scheme 3.

J. Kiesewetter et al. / Journal of Organometallic Chemistry 595 (2000) 81–86
83
(CO)2{CH(OMe)C6H4-p-Br}] (9) and [Fe(C5Me5)-
(CO)2{CH(OMe)-2-C4H3S}] (10) are obtained from 6
by using the appropriate nucleophiles LiC6H4-p-Br and
2-LiC4H3S (Scheme 4). Both compounds have been
fully characterised by NMR spectroscopy. The 13C-
NMR spectra clearly show two diastereotopic carbonyl
ligands, caused by the presence of the stereogenic a-car-
bon. Such derivatives are potential precursors of non-
heteroatom-stabilised carbene complexes [10]. In
addition, the presence of a bromide substituent on the
C6 ring or the lithiation of the thienyl substituent may
give access to dinuclear species. For instance, Maiorona
et al. have used this synthetic approach to prepare the
heterobimetallic complex [(CO)5Cr{m-C(OEt)-(2,2%-
C4H2S)2-C(OEt)}W(CO)5] [11].
Fig. 1. Cyclic voltammogram of [Fe(C5Me5)(dppe)]2{m-h1,h1%-2,2%-
C4H2S} (7) (Pt electrode, THF, 0.1 M [nBu4N][PF6], 0.1 V s−1).
Treatment of the methoxycarbene complex 8 with
dilithiated nucleophiles provides a route to symmetrical
dinuclear a,a%-methoxy complexes. Addition of 2,2%-
Li2C4H2S/TMEDA to two equivalents of 8 at −80°C
gives the thiophene derivative [Fe(C5Me5)(CO)2{m-
h1,h1%-CHOMe-]2(2,2%-C4H3S) (11). The biphenylene
complex [Fe(C5Me5)(CO)2{m-h1,h1%-CHOMe-]2(p-C6H4-
C6H4) (12) is obtained as a yellow powder in 75% yield
by using p-dilithiobiphenylene. Since there are two
stereogenic carbon centres (Ca) in 11 and 12, they are
formed as a mixture of meso and dl diastereoisomers.
This is clearly established by the NMR spectra, where
two sets of signals are seen. For example, the NMR
spectra of 11 exhibit two signals for the CH groups at
l(1H) 5.36 and 5.33 and l(13C) 81.8 and 81.6.
Scheme 4.
The conversion of 12 into the corresponding bis(car-
bene) complex [Fe(C5Me5)(CO)2{m-h1,h1%-CH-]2(p-
C6H4-C6H4) (13) is achieved by elimination of both
methoxide groups by using two equivalents of HBF4–
OEt2 (Scheme 5), a procedure described for analogous
mononuclear species [12]. The reaction, when carried
out in ether at −80°C, gives a dark purple solid which
is stable at temperatures below −50°C. The key spec-
troscopic feature of 13 is the carbene fragment reso-
nances located at characteristic chemical shifts l(1H)
15.63 and l(13C) 341.9 [12]. Examples of di-iron bis-
(carbene) complexes have been previously reported and
are generally formed by ligand–ligand coupling reac-
tions [13,14].
The above reactions are convenient routes to a wide
variety of [Fe(C5Me5)(CO)2] complexes and their phos-
phine derivatives, these latter species not being directly
accessible. This opens an entry to novel bimetallic
complexes. The mononuclear species can serve as build-
ing blocks for the preparation of intramolecular charge-
transfer compounds having both electron-donating and
electron-accepting organometallic fragments. We are
currently studying the synthesis of disymmetric p-conju-
gated bridged complexes.
Scheme 5.
2.2. Reacti6ity of the methoxycarbene complex
The methoxycarbene complex [Fe(C5Me5)(CO)2-
(ꢁCHOMe)][PF6] (8) cleanly reacts with organolithium
reagents [9]. For instance, complexes [Fe(C5Me5)-

84
J. Kiesewetter et al. / Journal of Organometallic Chemistry 595 (2000) 81–86
3. Experimental
3.1. General data
Anal. Calc. for C17H24O2FeSi: C, 59.30; H, 7.03.
Found: C, 59.01; H, 7.08.
3.4. [Fe(C5Me5)(CO)(PPh3){C(O)CꢀCSiMe3}] (4)
All manipulations were carried out under an argon
atmosphere with Schlenk techniques. Solvents were
dried and distilled under nitrogen before use by stan-
dard methods. Complexes [Fe(C5Me5)(CO)2(L)][PF6] (1;
a, L=CO; b, L=CH3CN; c, L=PPh3) [5] and
[Fe(C5Me5)(CO)2(ꢁCHOMe)][PF6] (8) [6] were prepared
according to the literature procedures. Photolysis exper-
iments were carried out by using an Original Hanau
150 W (Hg, high pressure) lamp. NMR spectra were
recorded on Bruker DPX-200 and Bruker AC 300 (by
S. Sinbandhit, CRMPO, Universite´ de Rennes 1) spec-
trometers. Infrared spectra were obtained with a Bruker
IFS28 FT-IR spectrometer. Mass spectra were recorded
on a Varian MAT 311 (70 eV) instrument and FAB
mass spectra on a Micromass ZABSpec TOF spectrom-
eter at the CRMPO. Cyclic voltammetry was per-
As described above, 0.5 mmol (330 mg) of 1c was
treated with LiCꢀCSiMe3 (0.65 mmol) in THF (20 ml).
Work-up gave after chromatography on silica gel (elu-
ent: 75:25 pentane–ether) orange microcrystals (155
1
mg, 50.8%). H-NMR (300 MHz, CDCl3) l 7.51 (m,
PPh3), 7.33 (m, PPh3), 1.48 (s, 15H, C5Me5), 0.19 (s,
9H, SiMe3); 31P-NMR {1H} (121.5 MHz, CDCl3) l
73.47 (s, PPh3); 13C-NMR {1H} (50.3 MHz, CDCl3) l
2
2
269.45 (d, J(C–P)=28 Hz, CꢁO), 221.72 (d, J(C–
P)=28 Hz, CO), 134.0 (v. br. s, Phortho), 133.74 (d,
1J(C–P)=20 Hz, Phipso), 129.45 (br.s, Phpara), 127.74
(d, 3J(C–P)=8 Hz, Phmeta), 106.53 (d, 2J(C–P)=7
Hz, CꢀCSiMe3), 96.31 (CꢀCSiMe3), 93.83 (C5Me5),
9.32 (C5Me5), −0.24 (SiMe3); IR (CH2Cl2, cm−1) 1915
(w(CO)), the w(CꢀC) absorption band was not observed.
Anal. Calc. for C35H39O2FeSiP: C, 69.30; H, 6.48.
Found: C, 69.56; H, 6.31.
formed on
a
PAR potentiostat model 263.
Microanalyses were performed by the ‘Centre de Mi-
croanalyse du CNRS’ at Vernaison, France.
3.5. [Fe(C5Me5)(dppe){CꢀCSiMe3}] (5)
3.2. [Fe(C5Me5)(CO)2{C(O)CꢀCSiMe3}] (2)
Complex 3 (1.2 mmol, 406 mg) and 1.77 mmol (705
mg) of dppe were dissolved in 200 ml of a mixture of
95:5 toluene–acetonitrile. The solution was irradiated
for 4 h. After evaporation to dryness, the residue was
extracted with pentane. Crystallisation gave red micro-
crystals (590 mg, 72% yield). 1H-NMR (300 MHz,
CDCl3) l 7.95 (m, 4H, Phortho), 7.28 (m, 16H, Ph), 2.76
(m, 2H, CH2), 1.99 (m, 2H, CH2), 1.38 (s, 15H, C5Me5),
−0.11 (s, 9H, SiMe3); 31P-NMR {1H} (121.5 MHz,
CDCl3) l 100.56 (s, dppe); 13C-NMR {1H} (50.3 MHz,
CDCl3) l 162.89 (t, 2J(C–P)=37 Hz, Ca), 139.07–
137.48 (2×m, Phipso), 134.42–133.95 (2×m, Phortho),
128.69–128.44 (2×m, Phpara), 127.10–126.77 (2×m,
Phmeta), 123.71 (Cb), 87.45 (C5Me5), 30.66 (CH2), 9.95
(C5Me5), 1.34 (SiMe3); IR (CH2Cl2, cm−1) 1981
(w(CꢀC). Anal. Calc. for C41H48FeSiP2: C, 71.71; H,
7.05. Found: C, 71.92; H, 7.10.
A suspension of 1 mmol (420 mg) of 1a in THF (20
ml) was treated at −80°C with a freshly prepared
solution of LiCꢀCSiMe3 (1.1 mmol) in THF (10 ml).
After stirring overnight, the solution was warmed up to
room temperature (r.t.) and evaporated to dryness. The
residue was extracted with diethylether. Chromatogra-
phy on silica gel (eluent: 50:50 pentane–ether) gave 100
mg (50%) of yellow microcrystals of 2. Elution with
75:25 pentane–ether afforded 100 mg of complex 3.
Complex 2, 1H-NMR (200 MHz, CDCl3) l 1.84 (s,
15H, C5Me5), 0.23 (s, 9H, SiMe3); 13C-NMR {1H} (50.3
MHz, CDCl3) l 252.78 (CꢁO), 215.12 (CO), 106.20
(CꢀCSiMe3), 100.00 (CꢀCSiMe3), 97.47 (C5Me5), 9.76
(C5Me5), −0.06 (SiMe3); IR (CH2Cl2, cm−1) 2003
(wCO)), 1952 (w(CO)), 1614 (w(CꢁO)). The w(CꢀC) band
was not observed, but may be masked by the strong
w(CO) absorption bands. Anal. Calc. for C18H24O3FeSi:
C, 58.07; H, 6.55. Found: C, 58.10; H, 6.55.
3.6. [Fe(C5Me5)(CO)2{v-p1,p1%-C(O)-]2(2,2%-C4H2S) (6)
3.3. [Fe(C5Me5)(CO)2(CꢀCSiMe3)] (3)
A suspension of 2 mmol (840 mg) of 1a in 20 ml of
THF was transferred by a canula at −80°C to a
The title compound was prepared by the procedure
described above, by using 3 mmol (1.3 g) of 1b and
LiCꢀCSiMe3 (3.5 mmol) in THF (30 ml). Chromatogra-
phy on silica gel (eluent: 75:25 pentane–ether) gave
freshly prepared suspension of
1 mmol of 2,2%-
Li2C4H2S–TMEDA in heptane. The reaction mixture
was allowed to warm up to r.t. overnight, and the
solvent removed in vacuo. The residue was extracted
with ether, crystallisation in a CH2Cl2–pentane mixture
1
brown yellow microcrystals (876 mg, 84.8%). H-NMR
(300 MHz, CDCl3) l 1.83 (s, 15H, C5Me5), 0.10 (s, 9H,
SiMe3); 13C-NMR {1H} (75.5 MHz, CDCl3) l 214.57
(CO), 131.32 (CꢀCSiMe3), 118.57 (CꢀCSiMe3), 96.97
(C5Me5), 9.86 (C5Me5), 1.76 (SiMe3); IR (CH2Cl2,
cm−1) 2036 (w(CꢀC)), 2007 (w(CO)), 1966 (w(CO)).
1
gave 430 mg of yellow crystals (68%). H-NMR (300
MHz, CDCl3) l 7.40 (s, 2H, H3/3%), 1.77 (s, 30H,
C5Me5); 13C-NMR {1H} (50.3 MHz, CDCl3) l 253.4
(CꢁO), 215.9 (CO), 156.2 (C2/2%), 128.4 (C3/3%), 97.4

J. Kiesewetter et al. / Journal of Organometallic Chemistry 595 (2000) 81–86
85
(C5Me5), 9.6 (C5Me5); IR (CH2Cl2, cm−1
(w(CO)), 1946 (w(CO)), 1563 (w(CꢁO)). Anal. Calc. for
C30H32O6SFe2: C, 56.98; H, 5.10. Found: C, 57.87; H,
5.05.
)
2006
C5Me5); 13C-NMR {1H} (75.5 MHz, C6D6) l 219.3
(CO), 217.3 (CO), 160.6 (C2), 126.3 (C3%), 121.6 (C2%),
118.9 (C3), 95.8 (C5Me5), 81.3 (CH), 60.2 (OMe), 9.2
(C5Me5); IR (CH2Cl2, cm−1) 1991 (w(CO)), 1934
(w(CO)). Anal. Calc. for C18H22O3SFe: C, 57.76; H,
5.92. Found: C, 57.62; H, 5.80.
3.7. [Fe(C5Me5)(dppe)]2{v-p1,p1%-2,2%-C4H2S} (7)
A solution of 0.3 mmol (220 mg) of 6 and 1 mmol
(398 mg) of dppe in 200 ml of a mixture of 95:5
toluene–acetonitrile was irradiated under UV for 2 h.
The yellow solution became black. After evaporation to
dryness, the residue was washed with pentane. Crys-
tallisation in a THF–pentane mixture gave 346 mg of a
black powder (80%). 1H-NMR (300 MHz, C6D6) l
7.69–7.02 (m, 40H, Ph), 6.43 (s, 2H, H3/3%), 1.85 (m, 8H,
CH2PPh2), 1.54 (s, 30H, C5Me5); 13C-NMR {1H} (75.5
MHz, C6D6) l 150.4 (m, C2/2%), 143.9 (C3/3%), 143.8 (m,
Ph), 140.1 (m, Ph), 135.2 (m, Ph), 128.8 (m, Ph), 87.0
(C5Me5), 30.3 (m, CH2), 11.7 (C5Me5); 31P-NMR {1H}
(121.5 MHz, C6D6) l 105.2 (dppe). HRM mass FAB
m/z 1260.3624 [M+] calc. for C76H80P4SFe2 126.3635
[M+]. Cyclic voltammetry (Pt, THF, [nBu4N][PF6] 0.1
M, 0.1 V s−1): E°(FeII/FeIII)= −0.592 V vs. SCE,
E°(FeIII/FeIII)= −0.038 V vs. SCE.
3.10. [Fe(C5Me5)(CO)2{v-p1,p1%-CHOMe-]2(2,2%-
C4H2S) (11)
A suspension of 1.7 mmol (742 mg) of 8 in 15 ml of
THF was transferred by a canula at −80°C to a
freshly prepared suspension of 0.8 mmol of 2,2%-
Li2C4H2S–TMEDA in heptane. The reaction mixture
was allowed to warm up to r.t. overnight, and the
solvent removed in vacuo. Compound 11 was extracted
with pentane (2×10 ml), a yellow powder (225 mg,
40%) precipitated by concentration of pentane. 1H-
NMR (300 MHz, C6D6) l 6.79–6.78 (2×s, 2H, H3,3%),
5.36–5.33 (2×s, 2H, CH), 3.39–3.38 (2×s, 6H, OMe),
1.49–1.48 (2×s, 30H, C5Me5), ratio of integration, 1:1;
13C-NMR {1H} (75.5 MHz, C6D6) l 219.4–219.3 (CO),
217.4–217.3 (CO), 156.43–156.37 (C2), 118.6–118.5
(C3), 95.6–95.5 (C5Me5), 81.8–81.6 (CH), 60.0 (OMe),
9.2 (C5Me5); IR (CH2Cl2, cm−1) 1989 (w(CO)), 1933.6
(w(CO)). Anal. Calc. for C32H40O6SFe2: C, 57.85; H,
6.07. Found: C, 57.67; H, 6.01.
3.8. [Fe(C5Me5)(CO)2{CH(OMe)C6H4-p-Br}] (9)
To a suspension of 0.41 mmol (179 mg) of 8 in 15 ml
of diethyl ether were added at −80°C, 1.5 equivalents
of freshly prepared LiC6H4-p-Br. The reaction mixture
was allowed to warm up to r.t., and several drops of
methanol were added to quench the excess of lithium
salt. After evaporation of the solvent at reduced pres-
sure, the residue was extracted with pentane. Crystalli-
sation gave 100 mg (55% yield) of orange microcrystals.
1H-NMR (300 MHz, CD2Cl2) l 7.24 (d, 3J(H–H)=8.2
3.11. [Fe(C5Me5)(CO)2{v-p1,p1%-CHOMe-]2(p-C6H4-
C6H4) (12)
A solution of 2 mmol (872 mg) of 8 in 25 ml of THF
was treated with 1 mmol of p-Li-C6H4-C6H4-Li (freshly
prepared from
1 mmol (312 mg) of 4,4%-dibro-
mophenylene and 2 mmol (1.25 ml) of nBuLi (1.6 M in
hexane) in THF (15 ml). After warming up to r.t., the
solution was evaporated under vacuum and the residue
extracted with toluene. Crystallisation in CH2Cl2–hex-
ane gave 555 mg (75% yield) of a yellow powder.
3
Hz, 2H, Ar), 6.95 (d, J(H–H)=8.2 Hz, 2H, Ar), 4.93
(s, 1H, CH), 3.14 (s, 3H, OMe), 1.77 (s, 15H, C5Me5);
13C-NMR {1H} (75.5 MHz, CD2Cl2) l 219.4 (CO),
217.7 (CO), 153.9 (Aripso), 131.1 (Ar), 125.6 (Ar), 116.4
(ArBr), 96.6 (C5Me5), 86.1 (CH), 60.8 (OMe), 9.6
(C5Me5); IR (pentane, cm−1) 1999.3 (w(CO)), 1948.5
(w(CO)). Anal. Calc. for C20H23O3BrFe: C, 53.72; H,
5.18. Found: C, 53.68; H, 5.03.
3
1H-NMR (300 MHz, C6D6) l 7.63–7.62 (2×d, J(H–
3
H)=8 Hz, 2H, Ar), 7.45 (d, J(H–H)=8 Hz, 2H, Ar),
5.15 (s, 1H, CH), 3.27–3.26 (2×s, 3H, OMe), 1.53 (s,
15H, C5Me5), ratio of integration, 1:1; 13C-NMR {1H}
(75.5 MHz, C6D6) l 219.5 (CꢁO), 217.5 (CO), 152.7
(Aripso), 137.7–137.6 (2×s, Arpara), 126.9 (Armeta),
124.5 (Arortho), 95.8 (C5Me5), 86.9 (CH), 60.6 (OMe),
9.3 (C5Me5); IR (CH2Cl2, cm−1) 1989 (w(CO)), 1932
(w(CO)). Anal. Calc. for C40H46O6Fe2: C, 65.41; H,
6.31. Found: C, 65.45; H, 6.11.
3.9. [Fe(C5Me5)(CO)2{CH(OMe)(2-C4H3S)}] (10)
Complex 10 was prepared according to the procedure
described for 7, starting from 2 mmol (872 mg) of 8 and
2 mmol of 2-LiC4H3S. Extraction with pentane (2×10
ml) and crystallisation gave a yellow brown oil (377 mg,
3.12. [Fe(C5Me5)(CO)2{v-p1,p1%-CH-]2(p-C6H4-C6H4)
(13)
1
3
65%). H-NMR (300 MHz, CDCl3) l 7.01 (dd, J(H–
H)=5.0 Hz, 4J(H–H)=1.2 Hz, 1H, H2%), 6.80 (dd,
3J(H–H)=3.5 Hz, J(H–H)=5.0 Hz, 1H, H3%), 6.66
A suspension of 176 mg (0.24 mmol) of 11 in 10 ml
of Et2O was treated at −80°C with 95 ml (0.5 mmol) of
HBF4–OEt2. The colour became purple. The ether was
3
3
4
(dd, J(H–H)=3.5 Hz, J(H–H)=1.2 Hz, 1H, H3),
5.27 (s, 1H, CH), 3.25 (s, 3H, OMe), 1.77 (s, 15H,

86
J. Kiesewetter et al. / Journal of Organometallic Chemistry 595 (2000) 81–86
[6] V. Guerchais, C. Lapinte, J.-Y. The´pot, L. Toupet, Organo-
metallics 7 (1988) 604.
[7] F. Coat, C. Lapinte, Organometallics 15 (1996) 477.
[8] (a) V. Guerchais, work in progress. (b) D. Astruc, in: Electron
Transfer and Radical Processes in Transition-Metal Chemistry,
VCH, Weinheim, 1995.
[9] (a) C.P. Casey, W.H. Miles, J. Organomet. Chem. 254 (1983)
333. (b) M.-A. Guillevic, P. Bre´gaint, C. Lapinte, J. Organomet.
Chem. 514 (1996) 157.
[10] (a) M. Brookhart, W.B. Studabaker, Chem. Rev. 87 (1987) 411
and references therein. (b) V. Guerchais, Bull. Soc. Chim. Fr.
131 (1994) 803.
removed by canula and the dark purple solid dried
1
under vacuum. H-NMR (300 MHz, CD2Cl2, 25°C) l
3
15.63 (s, 1H, ꢁCH), 8.16 (d, J(H–H)=8 Hz, 2H, Ar),
8.09 (d, 3J(H–H)=8 Hz, 2H, Ar), 2.02 (s, 15H,
C5Me5); 13C-NMR {1H} (75.5 MHz, CD2Cl2, −50°C)
l 341.9 (ꢁC), 210.3 (CO), 153.2 (Aripso/para), 148.6
(Aripso/para), 135.9 (Ar), 129.9 (Ar), 107.8 (C5Me5), 10.1
(C5Me5).
Acknowledgements
[11] S. Maiorona, A. Papagni, E. Licandro, A. Persoons, K. Clay, S.
Houbrechts, W. Porzio, Gazz. Chim. Ital. 125 (1995) 377.
[12] M. Brookhart, W.B. Studabaker, M.B. Humphrey, G.R. Husk,
Organometallics 8 (1989) 132.
The Socrates–Erasmus program is acknowledged for
a grant to J.K.
[13] V. Mahias, S. Cron, L. Toupet, C. Lapinte, Organometallics 15
(1996) 5399 and references therein.
[14] For different approaches to bis(carbene) complexes, see for
example: (a) A. Etzenhouser, M.D. Cavanaugh, H.N. Spurgeon,
M.B. Sponsler, J. Am. Chem. Soc. 116 (1994) 2221. (b) N. Hoa
Tran Huy, P. Le Floch, F. Robert, Y. Jeannin, J. Organomet.
Chem. 327 (1987) 211. (c) C. Roger, T.-S. Peng, J.A. Gladysz, J.
Organomet. Chem. 439 (1992) 163. (d) A. Rabier, N. Lugan, R.
Mathieu, G.L. Geoffroy, Organometallics 13 (1994) 4676. (e) O.
Briel, A. Fehn, W. Beck, J. Organomet. Chem. 578 (1999) 247.
(f) C. Hartbaum, E. Mauz, G. Roth, K. Weissenbach, H.
Fischer, Organometallics 18 (1999) 2619 and references therein.
References
[1] F. Paul, C. Lapinte, Coord. Chem. Rev. 178 (1998) 431 and
references therein.
[2] For the parent Cp complexes, see: K. Ru¨ck-Braun, M. Mikulas,
P. Amrhein, Synthesis 5 (1999) 727.
[3] G. Poignant, F. Martin, V. Guerchais, Synlett (1997) 913.
[4] N. Le Narvor, C. Lapinte, Organometallics 14 (1995) 634.
[5] D. Catheline, D. Astruc, Organometallics 3 (1984) 1094 and
references therein.
.