Selective mono- and di{(perfluoroalkyl)acylation} of ferrocene

Article abstract of DOI:10.1016/j.jfluchem.2003.08.002

The selective synthesis of mono- and 1,1′-di{(perfluoroalkyl)acylated} ferrocenes by Friedel-Crafts acylation with (perfluoroalkyl)acyl halides is described. The acyl derivatives were further converted to the corresponding (perfluoroalkyl)alkyl ferrocenes by reduction of the carbonyl group with LiAlH₄/AlCl₃. Electrochemical studies of all the obtained substituted ferrocenes were carried out to assess the influence of the perfluoroalkyl ponytails on their redox behavior.

Full text of DOI:10.1016/j.jfluchem.2003.08.002

Journal of Fluorine Chemistry 124 (2003) 177–181
Selective mono- and di{(perfluoroalkyl)acylation} of ferrocene
a,*
a
David Hazafy , Marie Sobocikova , Petr Stepnicka , Jirı Ludvık , Martin Kotora
a
b
c
ˇ
´
ˇ
ˇ
ˇ´
´
aDepartment of Organic and Nuclear Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 43 Prague, Czech Republic
bDepartment of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 43 Prague, Czech Republic
c
´ ˇ
J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 3, 182 23 Prague, Czech Republic
Received 18 July 2003; received in revised form 1 August 2003; accepted 4 August 2003
Abstract
The selective synthesis of mono- and 1,10-di{(perfluoroalkyl)acylated} ferrocenes by Friedel–Crafts acylation with (perfluoroalkyl)acyl
halides is described. The acyl derivatives were further converted to the corresponding (perfluoroalkyl)alkyl ferrocenes by reduction of the
carbonyl group with LiAlH4/AlCl3. Electrochemical studies of all the obtained substituted ferrocenes were carried out to assess the influence
of the perfluoroalkyl ponytails on their redox behavior.
# 2003 Elsevier B.V. All rights reserved.
Keywords: Perfluoroalkylation; Perfluoroacylation; Ferrocene; Perfluoroalkylated ferrocenes
1. Introduction
shield the cyclopentadienyl ring from the inductive effect of
the perfluoroalkyl chain. There has been some progress
achieved in the recent years in the development of methods
for the preparation of (perfluoroalkyl)alkylated cyclopenta-
dienes by alkylation of cyclopentadienes with RfCH2CH2I
but these procedures has been usually plagued by relatively
low yields and selectivity [3,4].
The preparation of (perfluoroalkyl)alkylcyclopentadienes
could be circumvented by a direct (perfluoroalkyl)alkylation
of cyclopentadienyl compounds. One of the possible
approaches is Friedel–Crafts acylation of metallocenes with
acyl halides followed by reduction of the acyl to an alkyl
group. Although there have been reported a number of
acylation reactions with cyclopentadienyl complexes of iron
[5], cobalt [6], manganese [6a], this approach has not yet
been applied for (perfluoroalkyl)acylation. The only excep-
tion is acylation of ferrocene with (perfluoroalkyl)acyl
chloride with a 10-carbon atom spacer [7]. Herein we would
like to report our results on selective mono and diacylation
of ferrocene with 4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorono-
nan-1-oyl chloride 1 (C6F13CH2CH2C(O)Cl).
A recent demand for environmentally benign technolo-
gies has led to the development of homogeneous catalysis in
biphasic systems with fluorous phase [1] and, consequently,
has initiated a search for catalytically active, fluorophilic
transition–metal complexes. As the latter are derived mostly
from the classical, non-fluorophilic complexes by a mod-
ification of their ligands with perfluoroalkyl substituents, a
careful choice of the parent ligand backbone and its proper
modification are vital for obtaining of efficient catalytic
systems.
Among the compounds so far tested, cyclopentadienyl
complexes are of particular importance because the cyclo-
pentadienyl ligand is usually firmly bound to the metal.
There have been reported preparation of perfluoralkylated
cyclopentadienes and the formation of some transition metal
complexes thereof. However, a directly attached perfluor-
oalkyl moiety, due to its strong electron-withdrawing nature,
dramatically changes electronic properties and reactivity of
the cyclopentadienyl ligands and their complexes [2].
Hence, it is of general interest to develop methods for the
preparation of new perfluoroalkylated cyclopentadienes and
their complexes with a spacer inserted between the cyclo-
pentadienyl ring and the perfluoroalkyl chain that would
2. Results and discussion
Although there are several synthetic routes [8] leading to
the starting (perfluoroalkyl)acyl chloride 1, we used the
procedure outlined in Scheme 1 as it allows to use a readily
accessible starting material: the reaction sequence started
* Corresponding author. Tel.: þ420-221-951-318;
fax: þ420-221-951-326.
E-mail address: kotora@natur.cuni.cz (M. Kotora).
0022-1139/$ – see front matter # 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2003.08.002

178
D. Hazafy et al. / Journal of Fluorine Chemistry 124 (2003) 177–181
Scheme 2. Mono- and diacylation of ferrocene.
product 6 was observed only in a negligible extent (ca. 1%).
Diacylation was carried out under the same conditions but
with 2.2 eq. of 1 and gave selectively 56% of bis(4,4,5,
5,6,6,7,7,8,8,9,9,9-tridecafluorononan-1-oyl)ferrocene (6).
The formation of mono(perfluoroalkyl)acylated product 5
was not observed. Interestingly, an attempt to carry out
acylation directly by using a mixture POCl3/AlCl3 and
carboxylic acid 4 did not afford any acylated ferrocenes [5d].
The next step was the reduction of the carbonyl group to a
methylene group. In both cases the reduction was achieved
with a mixture of LiAlH4/AlCl3 to give the corresponding
products 7 and 8 in 85 and 55% yields, respectively [12].
Scheme 1. Preparation of acyl chloride 1.
with copper-catalyzed radical addition of perfluorohexyl
iodide to propenol to give 2-iodo-4,4,5,5,6,6,7,7,8,8,9,9,9-
tridecafluorononan-1-ol (2) followed by reduction with tri-
butylstannane to 4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorono-
nano-1-ol (3) [9]. Alcohol 3 was easily oxidized to 4,4,5,
5,6,6,7,7,8,8,9,9,9-tridecafluorononanoic acid (4) under
mild conditions by using a RuCl3(cat.)/NaIO4 catalytic
system and biphasic conditions [10]. Finally, 4,4,5,5,6,6,7,
7,8,8,9,9,9-tridecafluorononan-1-oyl chloride 1 was pre-
pared by reaction of acid 4 with thionyl chloride [11].
Initially, monoacylation of ferrocene with 1 eq. of (per-
fluoroalkyl)acyl chloride 1 was carried out in the presence of
AlCl3 in tetrachloromethane under the same reaction con-
ditions as previously reported (Scheme 2) [7]. However, the
reaction did not proceed well, resulting in a mixture of
mono- and di(perfluoroalkyl)acylated products 5 and 6 in a
rather low yield. This could be attributed to the precipitation
of (perfluoroalkyl)acyl aluminate which formed upon the
addition of (perfluoroalkyl)acyl chloride 1 into a suspension
of AlCl3 in tetrachloromethane. Heterogeneous condition
thus influenced the distribution and the overall yield of the
products. Our assumption to change the solvent proved
correct and a replacement of tetrachloromethane with
dichloromethane enabled us to prepare a solution of (per-
fluoroalkyl)acyl aluminate and to carry out the acylation
reaction under homogenous conditions. Although the reac-
tion time was in comparison with the usual acylations rather
long (5 days), (4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorono-
nano1-oyl)ferrocene (5) was formed selectively in 48%
yield (after work-up). Unreacted ferrocene was recovered
in 37% yield and the formation of di(perfluoroalkyl)acylated
3. Electrochemistry
As revealed by voltammetric and cyclovoltammetric
measurements (Table 1), compounds 5–8 are reversible,
one-electron redox systems though the peak separations
in cyclovoltammograms (DEp) of the disubstituted ferro-
cenes are notably higher in the series. Whereas compounds 5
and 7 show DEp close to the value expected for an ideal,
reversible one-electron system (ca. 60 mV, cf. DEp ¼ 65 mV
for ferrocene under identical conditions), ferrocene-1,10-diyl
derivatives 6 and 8 exhibit significantly larger peak separa-
tions (95 and 120 mV, respectively) and, accordingly,
slightly tilted voltammetric waves. This points to some
chemical complications accompanying the electrochemical
oxidation in the latter case such as slow diffusion expectable
for large molecules [3], sorption processes or rather slow
subsequent reactions.
In accordance with the electron-withdrawing nature of
their substituents, ketones 5 and 6 are shifted to higher redox
potentials compared to ferrocene itself, the potential shift for
6 being nearly twice of that observed for 5. This points to an

D. Hazafy et al. / Journal of Fluorine Chemistry 124 (2003) 177–181
179
Table 1
Electrochemical data for 5–8a
5. Experimental
Perfluorohexyl iodide, ferrocene, aluminium chloride,
tributylstannane, thionyl chloride were purchased from
Aldrich and used as obtained. Propenol and dichloro-
methane (dried over CaH2) were distilled prior to use. 2-
Iodo-4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononan-1-ol acid
(2) [9], 4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononan-1-ol (3)
[9], 4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononan-1-oyl chlor-
ide (4) [11] were prepared according to the previously pub-
lished procedures.
NMR spectra were measured on a Varian UNITY Inova
400 spectrometer (1H, 400.0, 13C, 100.6, and 19F,
376.3 MHz). Chemical shifts (d/ppm) are given relative to
internal tetramethylsilane (1H, 13C) or to neat external
CFCl3 (19F, d ¼ 0). IR spectra were recorded on a Per-
kin-Elmer PE 640 spectrometer. High resolution, electron
impact (EI) mass spectra were measured on a ZAB SEQ
spectrometer. Positive ion FAB mass spectra were recorded
on the same instrument in a glycerol-thioglycerol matrix.
Elemental analyses were obtained on a Perkin-Elmer 2400
elemental analyzer. Melting points were determined on a
Kofler apparatus and are uncorrected. TLC was performed
on Merck Silica Gel 60 F254 aluminium sheets and column
chromatography was carried out on Merck Silica Gel 60.
Electrochemical measurements were carried out at 20 8C
with a multipurpose polarograph PA3 connected to an XY
Metallocene
E8 (V)
DEp (mV)
5
0.30
0.56
80
95
70
120
–
6
7
0.00
8
À0.01
0.03c
0.04c
Fe(CpRf)2-Ib
Fe(CpRf)2-IIb
–
E8 is the redox potential determined by cyclic voltammetry as Eꢁ
¼
ð1=2ÞðEpa þ EpcÞ while DEp denotes the separation of the cyclovoltam-
metric counter peaks, DEp ¼ Epa À Epc, Epa and are the anodic and
cathodic peak potentials, respectively. The half-wave potentials determined
from voltammetric curves are identical with E8 and, therefore, only
cyclovoltammetric date are listed in the Table. For conditions see Section 5.
a The potentials are given relative to internal ferrocene/ferrocenium.
b
Fe(CpRf)2-I ¼ [Fe{Z5-C5H4(CH2CH2C6F13)}2), Fe(CpRf)2-
II ¼ [Fe{Z5-C5H4(CH2CH2C10F21)}2].
c In THF data from ref. [3].
additivity of the electronic influences of the substituents at
the ferrocene unit with the deviation from simple additivity
attributable to an electron buffering effect of the cyclopen-
tadienyl p-electron systems. On the other hand, the ferro-
cene/ferrocenium potentials observed for 7 and 8 do not
virtually differ from that of unsubstituted ferrocene. This
implies that 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluoroct-1-yl
substituent has virtually no electronic influence on the
ferrocene core [H ꢀ (CH2)3(CF2)5CF3] and that the pro-
pane-1,3-diyl spacer is long enough to compensate effi-
ciently an electron-withdrawing effect of the perfluorohexyl
chain. A comparison of our data for trimethylene-spaced
compound 7 with its dimethylene analogue, [Fe{Z5-
C5H4(CH2CH2C6F13)}2], and the related compound
[Fe{Z5-C5H4(CH2CH2C10F21)}2] (Table 1) indicates that
the propane-1,3-diyl spacer assists in insulating the ferro-
cene unit from the perfluoroalkyl chain slightly more effi-
ciently than the shorter bridge, acting as an ‘‘electronically
neutral’’, not yet electron-donating substituent (cf. E8 for 1,10-
bis(alkylated)ferrocene,[Fe(Z5-C5H4Me)2],ofca.À0.05 Vin
MeCN [13]).
´ ˇ´
Recorder 4103 (Laboratornı prıstroje, Prague) using a three-
electrode consisting of a platinum disc working, platinum
wire auxiliary, and Ag/AgCl (1 M KCl) reference electrodes
(the reference electrode was separated from the measuring
compartment by a salt bridge filled with 1 M aqueous KCl).
The analyzed solutions contained 4 Â 10À4 M of the ana-
lyzed compounds and 0.1 M Bu4NPF6 as the base electrolyte
(Fluka, puriss. for electrochemistry) dissolved in dichloro-
methane (Merck p.a., used without any further purification).
The solutions were purged with argon and then kept under an
argon blanket. Cyclic voltammograms were recorded on the
stationary disc electrode at 100 mV sÀ1 while the voltammo-
grams were measured with rotating electrode (1000 minÀ1) at
a scan rate of 20 mV sÀ1. The potentials are given in Volts
relative to the redox potential of an internal ferrocene/
ferrocenium standard (E8(FcH/FcHþ) ¼ 0.48 V versus
Ag/AgCl).
4. Conclusion
We may conclude that the acylation of metallocenes
(ferrocenes) with (perfluoroalkyl)acyl chlorides may con-
stitute an alternative approach for the preparation of cyclo-
pentadienyl metal complexes with (perfluoroalkyl)alkyl
ponytails with and without polar carbonyl group(s). In the
case of ferrocene it is possible to control mono- and di(per-
fluoroalkyl)acylation selectively and simply by changing the
amount of (perfluoroalkyl)acyl halides and aluminium
chloride. In addition, electrochemical studies have shown
that propane-1,3-diyl spacer separates efficiently the ferro-
cene unit from an electron-withdrawing influence of the
perfluoroalkyl chain.
5.1. 4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononan-1-oic
acid (4)
A mixture of CCl4/MeCN/H2O (8/8/12 ml), tridecafluor-
ononan-1-ol 3 (1.55 g, 4 mmol), RuCl3ÁxH2O (22 mg,
0.1 mmol as trihydrate), and NaIO4 (3.42 g, 16 mmol)
was stirred at 20 8C for 24 h. Then, the reaction mixture
was extracted with Et2O (5 ml  20 ml), organic fractions
were collected and dried over MgSO4. Evaporation of the
solvent followed by distillation of the residue under reduced
pressure (115 8C/100 Pa) afforded 1 g (64%) of the title

180
D. Hazafy et al. / Journal of Fluorine Chemistry 124 (2003) 177–181
compound as a colorless solid. Its spectral characteristics
were identical with the previously published data [8a].
(apparent t, 4H, C5H4), 4.86 (apparent t, 4H, C5H4);
13C{1H} NMR (CDCl3) d 25.0 (t, 2JFC ¼ 12 Hz, CH2CF2),
30.9 (CH2C(O)), 70.7 (CH of C5H4), 73.6 (CH of C5H4),
79.6 (Cipso of C5H4), 199.7 (C¼O); 19F NMR (CDCl3) d
À126.5 (m, 4F, CF2), À123.9 (m, 4F, CF2), À123.2 (m, 4F,
CF2), À122.2 (m, 4F, CF2), À114.4 (m, 4F, CF2), À81.1 (t,
3JFF ¼ 10 Hz, 6F, CF3); IR (CHCl3) 1679 m (nC¼O), 1243 s,
1146 m, 1066 w cmÀ1; HR MS (FABþ) calcd for
C28H17F26FeO2 (M þ 1) 935.01628, found 935.01495.
Anal. calcd for C28H16F26FeO2: C, 36.00; H, 1.73; F,
52.87; Fe, 5.98; O, 3.43. Found: C, 36,18; H, 1,67.
5.2. (4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononan-
1-oyl)ferrocene (5)
To a suspension of aluminium chloride (135 mg, 1 mmol)
in dichloromethane (3 ml) was added dropwise a solution of
4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononan-1-oyl chloride
1 (411 mg, 211 ml, 1 mmol) in dichloromethane (3 ml) at
0 8C. The reaction mixture was stirred at the same tempera-
ture for 45 min, then ferrocene (188 mg, 1 mmol) was
gradually added in small portions, and the reaction mixture
was stirred for 5 days at 20 8C. The resulting solution was
treated with ice and 3 M HCl (5 ml). Organic layer was
separated, aqueous phase was extracted with hexane
(3 ml  10 ml), and the combined organic fractions were
dried over MgSO4. The solvent was removed under reduced
pressure and the residue purified by column chromatography
on silica gel (1/1 hexane/CDCl3) to afford 68 mg (37%) of
ferrocene and 228 mg (41%) of the title compound as an
orange solid: mp 96–97 8C; 1H NMR (CDCl3) d 2.48–2.66
(m, 2H, CH2C(O)), 3.10 (filled-in t, J0 ¼ 7:5 Hz, 2H,
CH2CF2), 4.23 (s, 5H, C5H5), 4.57 (apparent t, 2H,
C5H4), 4.84 (apparent t, 2H, C5H4); 13C{1H} NMR (CDCl3)
5.4. (4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononan-1-
yl)ferrocene (7)
To a stirred suspension of lithium aluminium hydride
(20 mg, 0.5 mmol) in dry diethylether (6 ml) was added
slowly aluminium chloride (67 mg, 0.5 mmol). After vigor-
ous reaction had subsided, a solution of (4,4,5,5,6,6,7,
7,8,8,9,9,9-tridecafluorononan-1-oyl)ferrocene 5 (146 mg,
0.26 mmol) in diethylether (2 ml) was added dropwise.
The reaction mixture was refluxed for 30 min, followed
by addition of ice water (2 ml) and 3 M HCl (2 ml). The
ether layer was separated, aqueous phase was extracted with
diethylether (2 ml  10 ml), organic fractions were col-
lected, washed with water, and dried over MgSO4. The
solvent was removed under reduced pressure and the residue
purified by column chromatography on silica gel (1/1 hex-
ane/CDCl3) to afford 120 mg (85%) of the title compound as
2
d 25.5 (t, JFC ¼ 12 Hz, CH2CF2), 30.2 (unresolved t,
CH2C(O)), 69.3 (CH of C5H4), 69.9 (C5H5), 72.6 (CH of
C5H4), 78.1 (Cipso of C5H4), 200.5 (C¼O); 19F NMR
(CDCl3) d À126.3 (m, 2F, CF2), À123.6 (m, 2F, CF2),
À123.2 (m, 2F, CF2), À122.1 (m, 2F, CF2), À114.3 (m,
1
an orange solid: mp 49–50 8C; H NMR (CDCl3) d 1.76–
3
2F, CF2), À81.1 (t, JFF ¼ 10 Hz, 3F, CF3); IR (CHCl3)
1.86 (m, 2H, CH2), 2.00–2.16 (m, 2H, CH2), 2.43 (t,
3JFH ¼ 7:6 Hz, 2H, CH2CF2), 4.08 (bs, 4H, C5H4), 4.12
(s, 5H, C5H5); 13C{1H} NMR (CDCl3) d 21.9 (t,
3JCF ¼ 3 Hz, CH2CH2CF2), 29.2 (FcCH2), 30.7 (t,
2JCF ¼ 12 Hz, CH2CF2), 67.9 (CH of C5H4), 68.5 (CH of
C5H4), 69.0 (C5H5), 88.0 (Cipso of C5H4); 19F NMR (CDCl3)
d À126.4 (m, 2F, CF2), À123.7 (m, 2F, CF2), À123.1 (m, 2F,
CF2), À122.2 (m, 2F, CF2), À114.4 (m, 2F, CF2), À81.0 (t,
3JFF ¼ 10 Hz, 3F, CF3); IR (CHCl3) 1242 s, 1145 m, 1121 w,
1106 w, 1003 w cmÀ1; HR MS (EI) calcd for C19H13F13FeO
546.03156, found 546.03282. Anal. calcd for C19H15F13Fe:
C, 41.78; H, 2.77; F, 45.22; Fe, 10.23. Found: C, 42.16; H,
2.66.
1674 s (nC¼O), 1458 m, 1243 s, 1146 m, 1066 w cmÀ1; HR
MS (EI) calcd for C19H13F13FeO 560.01082, found
560.01174. Anal. calcd for C19H13F13FeO: C, 40.74; H,
2.34; F, 44.09; Fe, 9.97; O, 2.86. Found: C, 41.29; H, 2.31.
5.3. bis(4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononan-
1-oyl)ferrocene (6)
To a suspension of aluminium chloride (405 mg, 3 mmol)
in dichloromethane (6 ml) was added dropwise a solution of
4,4,5,5,6,6,7,7,8,8,9,9,9-tridecafluorononan-1-oyl chloride
4 (904 mg, 532 ml, 2.2 mmol) in dichloromethane (4 ml)
at 0 8C. The reaction mixture was stirred at the same
temperature for 45 min, then ferrocene (188 mg, 1 mmol)
was gradually added in small portions. After that the reac-
tion mixture was stirred for 5 days at 20 8C. The resulting
solution was treated with ice and 3 M HCl (5 ml). Organic
layer was separated, aqueous phase was extracted with
hexane (3 ml  10 ml), and the combined organic fractions
were dried over MgSO4. The solvent was removed under
reduced pressure and the residue purified by column chro-
matography on silica gel (8/1 hexane/Et2O) to give 520 mg
(56%) of the title compound as an orange solid: mp 76–
5.5. bis(4,4,5,5,6,6,7,7,8,8,9,9,9-Tridecafluorononan-
1-yl)ferrocene (8)
To a stirred suspension of lithium aluminium hydride
(38 mg, 0.1 mmol) in diethylether (6 ml) was added slowly
aluminium chloride (135 mg, 1 mmol). After a vigorous
reaction had subsided, a solution of bis(4,4,5,5,6,6,7,
7,8,8,9,9,9-tridecafluorononan-1-oyl)ferrocene 6 (234 mg,
0.25 mmol) in diethylether (2 ml) was added dropwise.
The reaction mixture was refluxed for 30 min, followed
by addition of ice water (2 ml) and 3 M HCl (2 ml). The
ether layer was separated, aqueous phase was extracted with
1
77 8C; H NMR (CDCl3) d 2.48–2.64 (m, 4H, CH2C(O)),
2.90–2.96 (filled-in t, J0 ¼ 7:5 Hz, 4H, CH2CF2), 4.55

D. Hazafy et al. / Journal of Fluorine Chemistry 124 (2003) 177–181
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diethylether (2 ml  10 ml), organic fractions were col-
lected, washed with water, and dried over MgSO4. The
solvent was removed under reduced pressure and subsequent
column chromatography on silica gel (8/1 hexane/toluene)
afforded 125 mg (55%) of the title compound as an orange
solid: mp 40–41 8C; 1H NMR (CDCl3) d 1.76–1.86 (m, 4H,
CH2), 2.00–2.16 (m, 4H, CH2), 2.42 (t, 3JFH ¼ 7:6 Hz, 4H,
CH2CF2), 3.99 (apparent t, 4H, C5H4), 4.03 (apparent t, 4H,
C5H4); 13C{1H} NMR (CDCl3) d 22.0 (unresolved t,
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´ˇ
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(b) T. Brıza, J. Kvıcala, O. Paleta, J. Cermak, Tetrahedron 58 (2002)
ˇ´
´ˇ
´
2
CH2CH2CF2), 29.0 (FcCH2), 30.7 (t, JCF ¼ 12 Hz,
3841–3846;
ˇ
(c) J. Kvıcala, T. Brıza, O. Paleta, K. Aureova, J. Cermak,
´ˇ
ˇ´
´
´
CH2CF2), 68.2 (CH of C5H4), 68.7 (CH of C5H4), 87.5
(Cipso of C5H4); 19F NMR (CDCl3) d À126.5 (m, 4F, CF2),
À123.8 (m, 4F, CF2), À123.2 (m, 4F, CF2), À122.2 (m, 4F,
Tetrahedron 58 (2002) 3847–3854.
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´
ˇ
[5] (a) M. Salisova, S. Toma, Chem. Papers 40 (1986) 619–629;
(b) A.F. Cunningham Jr., Organometallics 13 (1994) 2480–2485;
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3
CF2), À114.4 (m, 4F, CF2), À81.1 (t, JFF ¼ 10 Hz, 6F,
CF3); IR (CHCl3) 1242 s, 1145 m, 1120 m cmÀ1; HR MS
(FABþ) calcd for C28H20F26FeO2 906.04993, found
906.05472. Anal. calcd for C28H20F26Fe: C, 37.11; H,
2.22; F, 54.51; Fe, 6.16. Found: C, 37.47; H, 2.13.
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Acknowledgements
This research was financially supported by Grant Agency,
Academy of Sciences of the Czech Republic (grant no.
IAA4072203).
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