Synthesis of ferrocenoate esters, amides and other ferrocenoyl derivatives using ferrocenoyl fluoride. A comparison of the reactions of ferrocenoyl fluoride in [bmim][BF4] with the microwave-promoted solvent-free reactions of ferrocenoyl fluoride

Article abstract of DOI:10.1016/j.jorganchem.2005.08.015

Simple, efficient and convenient routes for the synthesis of ferrocenoyl derivatives are described. They involve either the reaction of nucleophilic compounds and DMAP with ferrocenoyl fluoride in [bmim][BF₄] or the solvent-free reactions of nucleophilic compounds with ferrocenoyl fluoride promoted by microwaves.

Full text of DOI:10.1016/j.jorganchem.2005.08.015

Journal of Organometallic Chemistry 690 (2005) 4959–4966
www.elsevier.com/locate/jorganchem
Synthesis of ferrocenoate esters, amides and other ferrocenoyl
derivatives using ferrocenoyl fluoride. A comparison of the reactions
of ferrocenoyl fluoride in [bmim][BF4] with the microwave-promoted
solvent-free reactions of ferrocenoyl fluoride
*
Christopher Imrie , Elago R.T. Elago, Nadia Williams,
Cedric W. McCleland, Pieter Engelbrecht
Department of Chemistry, University of Port Elizabeth,1 P.O. Box 1600, Port Elizabeth 6000, South Africa
Received 24 May 2005; received in revised form 8 August 2005; accepted 8 August 2005
Available online 23 September 2005
Abstract
Simple, efficient and convenient routes for the synthesis of ferrocenoyl derivatives are described. They involve either the reaction of
nucleophilic compounds and DMAP with ferrocenoyl fluoride in [bmim][BF4] or the solvent-free reactions of nucleophilic compounds
with ferrocenoyl fluoride promoted by microwaves.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Ferrocenoate esters; Ferrocenoate amides; Ionic liquids; Ferrocenoyl fluoride; Solvent-free synthesis; Microwave-promoted synthesis
1. Introduction
uids [2–4], inorganic supports [5–10] or under solvent-
free conditions [11–17]. The solubility of ferrocenes has
also been investigated in supercritical fluids [18], and
some highly fluorinated ferrocenes have been synthesized
for the fluorous phase technique [19]. Scheme 1 high-
lights four recent examples involving the clean synthesis
of ferrocene derivatives. Sonification [20,21] and micro-
wave radiation [22] have also been used in the clean syn-
thesis of ferrocenes.
One of the current research goals within our group is
the discovery and development of methods for the syn-
thesis of ferrocenyl-containing molecules with the criteria
being that the methods occur under mild conditions, are
efficient providing high yields and high conversions and
are environmentally friendly. This piece of work deals
with the introduction of the ferrocenoyl group. The
ferrocenoyl group is found in molecules proposed for a
variety of applications. For example, it has been incorpo-
rated into medicinal molecules [23], liquid crystal mole-
cules [24], molecules used as electrochemical sensors
[25] and in molecules designed for anion recognition [26].
The subject of green chemistry is currently guided by
a series of 12 principles [1]. Organometallic chemistry can
be considered from two perspectives in relation to green
chemistry. Firstly, organometallic complexes and com-
pounds can take an active role in achieving a green
chemistry principle. For example, one of the principles
states that ‘‘it is better to use catalytic processes than
the stoichiometric variety.’’ Alternatively, the green
chemistry principles can be applied in the synthesis of
organometallic complexes. Several contributions have
been made for example in relation to green chemistry
and ferrocene derivatives. In many cases, ferrocene deriv-
atives have been synthesized in alternative reaction media
to volatile organic solvents. Examples include ionic liq-
1
The University of Port Elizabeth will in future form part of the Nelson
Mandela Metropolitan University, Port Elizabeth, South Africa.
*
Corresponding author. Tel.: +27415042823; fax: +27415042573.
E-mail address: Christopher.Imrie@upe.ac.za (C. Imrie).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.08.015

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C. Imrie et al. / Journal of Organometallic Chemistry 690 (2005) 4959–4966
O
O
O
DCC, DMAP
[bmim][BF4]
C
1
C
OH
+
Fe
OH
Fe
X
X
82-100%
O
H
CH
2
C
NH2
+
N
Fe
solvent-free
Fe
X
X
92-97%
CH3
OAc
CH3
NH2
conc. aq. NH3, DMF, )))), 0oC, 9h
CH
CH
3
Fe
Fe
92% (40% without sonification)
O
C
R
RCOOH, Al2O3, (CF3CO)2O
solvent-free
4
Fe
Fe
55-98%
Scheme 1.
Recently, we reported on the efficient syntheses of fer-
rocenoate esters from the reaction of ferrocenemonocarb-
oxylic acid and phenols using the DCC/DMAP protocol
in ionic liquid solvents [2]. In a follow-on paper, we re-
ported on the synthesis of ferrocenylimines under sol-
vent-free conditions [11]. From the viewpoint of green
chemistry, a major drawback in the esterification work
was the use of DCC since this gives rise to considerable
quantities of N,N-dicyclohexylurea which is undesirable
in terms of atom economy. One of the ways to avoid
the use of DCC is to use an activated form of ferrocene-
monocarboxylic acid. For this purpose, two reasonable
choices are ferrocenoyl fluoride (1) and ferrocenoyl imi-
dazolide (2). Both compounds are relatively stable solids
at room temperature.
Ferrocenoyl chloride has been widely used as a source of
the ferrocenoyl group despite the fact that it displays signif-
icant hydrolytic instability. Recently, Galow et al. [27]
showed that ferrocenoyl fluoride (1) reacts with alcohols
and amines in CH2Cl2 or THF to provide exceptionally
high yields of esters and amides, respectively. Alternatively,
Imrie et al. [28] have used ferrocenoyl imidazolide (2) as a
useful source of the ferrocenoyl group. The work described
in this paper discusses the reactions of 1 firstly in the
ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate
([bmim][BF4]) [29] secondly under solvent-free conditions
[30].
O
O
C
C
Fe
N
Fe
1
F
N
2
2. Results and discussion
Ferrocenoyl fluoride was synthesized by the reaction of
ferrocenemonocarboxylic acid and cyanuric fluoride as de-
scribed by Gallow et al. [27]. The compound was stored in
a desiccator in the dark. Whilst the compound did not ap-
pear to be prone to any significant hydrolysis, it was sus-
ceptible to some kind of slow decomposition especially if
left exposed to the atmosphere under ambient conditions.
This type of behaviour is common to many ferrocenyl-con-
taining molecules especially those in which strong electron-
withdrawing groups are situated adjacent to the ferrocenyl
group [31].
The reactions of ferrocenoyl fluoride with substituted
phenols and N,N-dimethylaminopyridine (DMAP) in

C. Imrie et al. / Journal of Organometallic Chemistry 690 (2005) 4959–4966
4961
Table 1
Yields of ferrocenyl esters from the reaction of ferrocenoyl fluoride and substituted phenols in [bmim][BF4]
O
O
O
DMAP
C
C
OH
+
[bmim][BF4], RT, 16h
Fe
F
Fe
X
X
Entry
Substituent X
Yield (%)a,b
1
2
3
4
5
6
7
a
4-OCH3
4-CH3
4-H
4-Cl
4-NO2
4-Br
99
98
94
99
100
60
4-CHO
80
Yields are isolated ones.
Esters were isolated and characterized by IR, NMR (1H, 13C) and high resolution mass spectroscopy.
b
[bmim][BF4] proceeded efficiently and provided excellent
yields of ferrocenyl esters (Table 1). The ester products
were easily extracted from [bmim][BF4] using small quan-
tities of diethyl ether. The conversions in all cases were
very high which meant that the ionic liquid could be
recovered at the end of each reaction in a reasonably
clean state. For one of the esterification reactions,
namely the reaction of ferrocenemonocarboxylic acid
and 4-methoxyphenol in [bmim][BF4], the solvent was
recovered at the end of the first reaction and was then
reused for the same reaction another four times. At the
end of each reaction, the product was extracted with
diethyl ether and the ionic liquid containing DMAP
by-products was used directly in the following reaction.
The results for the recycling reactions are shown in Table
2; the yields of the esters remained consistently high over
the five runs. At the end of the series of experiments, the
yield. The reaction of 1 with thiophenol in [bmim][BF4] pro-
vided the thioester (3).
Since one of our future aims is to study the reactivity
and properties of free radicals in [bmim][BF4] and other io-
nic liquids, we were eager to investigate the reactivity of 1
with N-hydroxy derivatives such as N-hydroxypyridine-2-
thione, 3-hydroxy-4-methyl-2(3H)-thiazolethione and ben-
zophenone oxime. Barton and co-workers [33] have utilized
acyl derivatives of the first two molecules as a source of dis-
ciplined free radicals on mild photolysis. The reactions
were conducted in the dark and all work-up procedures
were carried out in a dark environment, since it was ex-
pected that the products would be light sensitive. The
mixed anhydrides, compounds 4 and 5 were isolated in
moderate yields and the compounds were identical to those
prepared by us previously by a different route. Compounds
4 and 5 were extremely light sensitive and provided inter-
esting photochemistry on mild photolysis in solution using
a tungsten lamp. This chemistry will be published in a fu-
ture piece of work. Reaction of 1 with benzophenone
oxime in [bmim][BF4] provided an excellent yield of the
oxime ester 6. This compound is a potential source of ferr-
ocenoyloxyl free radicals (FcCOOÅ) since acyloxyl radicals
have been generated from the photolysis of benzophenone
oxime esters [34].
1
ionic liquid was analysed by H and 13C NMR spectros-
copy to investigate its integrity. This was considered to
be important in view of a recent publication by Aggar-
vaal et al. [32], which suggested that ionic liquids are
not always benign solvents in reactions. The NMR spec-
tra were identical to that of the starting material.
In order to expand the range of useful ferrocenoyl deriv-
atives made from 1 in [bmim][BF4], ferrocenoyl fluoride was
reacted with other nucleophilic reagents and a summary of
the reactions is provided in Scheme 2. The reactions of 1
with amines in [bmim][BF4] provided amides in excellent
Following on from our recent success at using solvent-
free conditions to synthesize ferrocenylimines [11], we were
eager to investigate the solvent-free reactivity of 1 with a
Table 2
Results for recycling reactions (the reactions of ferrocenoyl fluoride with 4-methoxyphenol in [bmim][BF4])
O
O
O
DMAP
C
C
CH3 O
OH
+
OCH3
[bmim][BF4], RT, 16h
Fe
F
Fe
Reaction run
1
2
3
4
5
Yield of estera
99
95
94
97
95
a
Yields are isolated ones.

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C. Imrie et al. / Journal of Organometallic Chemistry 690 (2005) 4959–4966
O
C
O
O
C
N C
Fe
N
R
R
Fe
6
64-88%
Ph
94%
OH
(R)2NH
[bmim][BF4]
C
N
[bmim][BF4]
Ph
DMAP
OH
SH
O
O
O
F
O
S
DMAP
DMAP
X
C
C
C
Fe
Fe
Fe
[bmim][BF4] or solvent-free/MW
[bmim][BF4]
X
3
60-100% : [bmim][BF4]
58-85% : SF
1
90%
HO
N
KSC(S)OCH2CH3
solvent-free
S
S
[bmim][BF4]
or solvent-free (SF)
S
N
DMAP
OH
DMAP
O
O
S
C
C
O
O
N
O
C
Fe
C
S
Fe
O
N
S
Fe
S
Fe
7
5
4
52%
45% : [bmim][BF4]
91%
52% : SF
Scheme 2.
range of nucleophilic compounds. In the initial instance, at-
tempts were made to react 1 with 4-methoxyphenol. The
two compounds were ground in an open mortar for
approximately three minutes but analysis indicated that
no significant reaction had occurred. At this stage, the mix-
ture was divided into two approximately equal parts.
DMAP was added to the first part and a further period
of grinding was carried out. Analysis of the paste indicated
that some 4-methoxyphenyl ferrocenecarboxylate had
formed but that the conversion was quite low. The second
part of the mixture was subjected to irradiation by micro-
waves (1.5 min) and this provided an excellent yield of
the ester with high conversion. A series of solvent-free
microwave-promoted esterifications using ferrocenoyl fluo-
ride and substituted phenols was then carried out and the
results are provided in Table 3. The yields of esters are gen-
erally high. A reaction time of 1 min was found to be suf-
ficient and the reaction could be run without DMAP
highlighting the significant effect of the microwave radia-
tion. Due to the sensitivity of the compounds 4 and 5,
microwave radiation was avoided in their solvent-free syn-
thesis. Ferrocenoyl fluoride, the N-hydroxy derivative and
DMAP were ground together under dark conditions and
this provided modest yields of 4 and 5. The solvent-free
reaction of 1 with potassium-O-ethylxanthate gave an
unexpected product, ferrocenoic thioanhydride (7). The ex-
pected product was FcC(O)SC(S)OCH2CH3 (8). Com-
pound 8 was a desirable product, since it should act as
_
an efficient source of ferrocenoyl free radicals (FcCO).
Zard and co-workers [35] have made widespread use of
similar compounds to provide acyl radicals. The synthesis
of 7 has been described previously by Katada et al. [36]
and on that occasion 7 was made by the reaction of ferroce-
noyl chloride and trimethylammonium ferrocenethiocarb-
oxylate (Fc(CO)SNMe3) in ether. Although there was no
evidence for the formation of 8 in the solvent-free synthe-
sis, it seems likely that 7 was formed in our work from
the interaction of 1 and 8.
There are various problems with the reactions just dis-
cussed in terms of their ‘‘green credentials.’’ Firstly, ferr-
ocenoyl fluoride is synthesized using cyanuric fluoride
and this is a potentially hazardous chemical. Secondly,
reactions take place with the liberation of hydrogen fluo-
ride. In the ionic liquid or in a solvent such as THF, most
of the hydrogen fluoride is removed by reaction with the
base DMAP. The generation of hydrogen fluoride in the
microwave-promoted solvent-free reactions poses more of
a problem. Attempts to trap the hydrogen fluoride in the

C. Imrie et al. / Journal of Organometallic Chemistry 690 (2005) 4959–4966
4963
Table 3
Yields of ferrocenyl esters from the microwave-promoted solvent-free reactions of ferrocenoyl fluoride and substituted phenols
O
O
Solvent-free, MW
1 min, RT
C
C
OH
+
O
Fe
F
Fe
X
X
Entry
Substituent X
Yield (%)a,b
1
2
3
4
5
6
7
8
9
a
4-OCH3
3-OCH3
4-CH3
4-But
4-H
4-Cl
2-Cl
4-NO2
4-Br
79
78
85
81
76
74
58
65
71
Isolated yields based on ferrocenoyl fluoride.
Esters were isolated and characterized by IR, NMR (1H, 13C) and high resolution mass spectroscopy.
b
microwave apparatus were thwarted by apparatus design
and the small scale of the reaction.
The phenols and amines were recrystallized or distilled prior
to use. N-Hydroxypyridine-2-thione was precipitated from
an aqueous solution of its sodium salt with 6 M hydrochlo-
ric acid and washed with cold water and dried. Full charac-
terization of the ferrocenyl esters and amides is provided in
the supplementary material.
3. Conclusion
Simple and convenient routes for the synthesis of ferr-
ocenoyl derivatives have been described and involved either
the reaction of nucleophilic compounds and DMAP with
ferrocenoyl fluoride in [bmim][BF4] or the solvent-free
reactions of nucleophilic compounds with ferrocenoyl fluo-
ride promoted by microwaves. The yields of the ferroce-
noyl derivatives were in most cases excellent and
purification was achieved with minimum use of solvent.
Efficient trapping of hydrogen fluoride was achieved in
[bmim][BF4] but its generation remains a problem under
solvent-free conditions.
4.2. Synthesis of ferrocenoyl fluoride (1)
Ferrocenoyl fluoride was synthesised by the method re-
ported by Galow et al. [27]. Quantity of ferrocenemono-
carboxylic acid starting material (1.152 g, 5.00 mmol).
The product was obtained as an orange crystalline solid 1
(0.974 g, 84%), M.p. 80–81 ꢁC ([27] 68–69 ꢁC); IR (KBr
cmÀ1) 1799, 1450, 1397, 1371, 1267, 1068, 995, 891, 818,
755, 698, 536, 484; 1H NMR (CDCl3) 4.88 (2H, t,
J = 1.9 Hz, C5H4), 4.60 (2H, t, J = 1.6 Hz, C5H4), 4.33
(5H, s, C5H5); 13C NMR(CDCl3) 165.7, 73.6, 71.7, 70.9,
69.8; m/z 232 (M+, 92), 167 (45), 140 (57), 92 (100), 75
(12), 64 (14), 56 (10). Anal. Calc. for C11H9FFeO: [M+]
231.99868; Found: [M+], 231.99650.
4. Experimental
4.1. Purification and characterization of the materials
Silica gel 50 was used for column chromatography. Thin-
layer preparative chromatography was carried out on plates
using Merck silica gel 60 F254 (1.5 mm) as adsorbent. Melt-
ing points were recorded on an Electrothermal IA 900 series
digital melting point apparatus and are uncorrected. Infra-
red spectra were recorded on a Perkin Elmer 1600 series
Fourier Transform IR spectrometer as KBr discs or as solu-
4.3. Reactions of ferrocenoyl fluoride with phenols in
[bmim][BF4]: general method
[Bmim][BF4] was deaerated by purging with nitrogen
and was also subjected to three cycles of the freeze–thaw
degassing technique. Ferrocenoyl fluoride (0.44 mmol),
the substituted phenol (0.44 mmol) and N,N-dimethylami-
nopyridine (0.21 mmol) (DMAP) were added to degassed
[bmim][BF4] (6 cm3) contained in a 25 cm3 round-bot-
tomed flask. Nitrogen was blown over the reaction before
it was sealed and the reaction was then stirred at room tem-
perature for 16 h. Stirring was stopped and the red-brown
mixture was then extracted with diethyl ether (9 · 5 cm3).
The ether extracts were combined, washed with water
and dried over anhydrous sodium sulfate. After removing
the diethyl ether in vacuo, the residue was passed through
1
tions in chloroform. H and 13C NMR spectra were re-
corded on a Bruker Avance 300 MHz spectrometer as
solutions in CDCl3 using tetramethylsilane (TMS) as inter-
nal standard. Mass spectra were recorded on a VG70-SEQ/
MSSMS2 spectrometer at the Cape Technikon. Recrystalli-
zations were performed at room temperature. All solvents
that required distillation were distilled directly into the reac-
tion flask to be used, under nitrogen. The synthesis of
[bmim][BF4] and [bmim] [PF6] has been described elsewhere
[37]. Ferrocenemonocarboxylic acid was purchased from
Strem (USA) and was used without further purification.

4964
C. Imrie et al. / Journal of Organometallic Chemistry 690 (2005) 4959–4966
a short silica gel column. The products were eluted with
hexane–diethyl ether (1:5) avoiding the use of undesirable
chlorinated solvents.
807; 1H NMR (CDCl3) 7.52 (2H, m, ArH), 7.48–7.44
(3H, m, ArH), 4.95 (2H, t, J = 1.8 Hz, C5H4), 4.55 (2H,
t, J = 1.8 Hz, C5H4), 4.31 (5H, s, C5H5); 13C NMR
(CDCl3) 192.1, 135.4, 129.6, 129.5, 128.3, 79.2, 72.4, 71.1,
69.6; m/z 323 (17%), 322 (M,+ 75), 230 (49), 228 (13),
214 (15), 213 (100), 211 (7), 186 (7) 185 (47), 129 (36),
121 (23); Anal. Calc. for C17H14FeOS: C, 63.4; H, 4.4%;
[M+], 322.0111. Found: C, 63.4; H, 4.3%; [M+], 322.0117.
4.4. Reaction of ferrocenoyl fluoride with 4-methoxyphenol
in [bmim][BF4]: general procedure for recycling
experiments
Ferrocenoyl fluoride (0.44 mmol), DMAP (0.21 mmol),
4-methoxyphenol (0.44 mmol) and [bmim][BF4] (6 cm3)
were placed in a 25 cm3 RB flask. The flask was sealed
and the mixture stirred at room temperature for 16 h.
The reaction mixture was then extracted using diethyl ether
(11 · 4 cm3). The ether extracts were combined and washed
twice with water and then dried over anhydrous sodium
sulfate. After removing the ether in vacuo, the residue
was passed through a short column of silica gel. Elution
with hexane–diethyl ether (1:4) provided the product, 4-
methoxyphenyl ferrocenecarboxylate. Fresh reactants were
added to the recovered ionic liquid and the reaction was re-
peated in the same manner four more times. At the end of
the fifth run, the ionic liquid (5.7 cm3) was recovered. The
4.7. Reaction of ferrocenoyl fluoride with N-hydroxy
derivatives
Ferrocenoyl fluoride (0.44 mmol), the N-hydroxy deriv-
ative (0.44 mmol) and DMAP (0.21 mmol) were added to
[bmim][BF4] (6 cm3) in a 25 cm3 round-bottomed flask.
Nitrogen was blown over the reaction before it was sealed
and the reaction was then stirred at room temperature for
16 h. Stirring was stopped and the mixture was then ex-
tracted with diethyl ether (9 · 5 cm3). The ether extracts
were combined, washed with water and dried over anhy-
drous sodium sulfate. After removing the diethyl ether in
vacuo, the residue was passed through a short silica gel col-
umn. The products were eluted with hexane–diethyl ether
avoiding the use of undesirable chlorinated solvents.
1
recovered ionic liquid was analysed by H NMR and gave
a spectrum identical to pure [bmim][BF4].
4.5. Reactions of ferrocenoyl fluoride with amines in
[bmim][BF4]: general method
4.7.1. With N-hydroxypyridine-2-thione: N-ferrocenoyloxy-
pyridine-2-thione (4)
Quantities. Ferrocenoyl fluoride (101 mg, 0.44 mmol),
N-hydroxypyridine-2-thione (57 mg, 0.44 mmol), DMAP
(21 mg, 0.172 mmol) and [bmim][BF4] (6 cm3). All opera-
tions in this reaction were carried out under dark condi-
tions since the product is extremely light sensitive. The
product was obtained as an orange solid and was identified
as N-ferrocenoyloxypyridine-2-thione (67 mg, 45%), M.p.
145–146 ꢁC; IR (KBr cmÀ1) 3011, 1754, 1606, 1526, 1450,
1411, 1372, 1351, 1266, 1232, 1176, 1135, 1107, 1064,
1027, 986, 881, 845, 813, 766, 741, 533, 497; 1H NMR
(CDCl3) 7.76 (1H, m, vinylic), 7.59 (1H, m, vinylic), 7.25
(1H, m, vinylic), 6.68 (1H, m, vinylic), 5.04 (2H, t,
J = 1.9 Hz, C5H4), 4.62 (2H, t, J = 1.9 Hz, C5H4), 4.46
(5H, s, C5H5); m/z 339 (M+, 100%), 323 (7), 248 (10),
247 (67), 230 (10), 213 (13), 199, (29), 185 (30), 166 (16),
134 (6), 130 (13), 129 (55), 121 (17), 103 (5), 92 (20), 83
(10), 78 (19), 69 (12), 56 (18), 51 (9), 39 (23); Anal. Calc.
for C16H13FeNO2S: [M+], 339.00164. Found: [M+],
339.00163.
Ferrocenoyl fluoride (0.44 mmol), the substituted amine
(0.44 mmol) and DMAP (0.21 mmol) were added to
[bmim][BF4] (6 cm3) in a 25 cm3 round-bottomed flask.
Nitrogen was blown over the reaction before it was sealed
and the reaction was then stirred at room temperature for
16 h. Stirring was stopped and the mixture was then ex-
tracted with diethyl ether until the extracts were colourless.
The ether extracts were combined, washed with water and
dried over anhydrous sodium sulfate.
4.6. Reaction of ferrocenoyl fluoride with thiophenol:
ferrocenoyl phenyl sulfide (3)
Ferrocenoyl fluoride (102 mg, 0.44 mmol), thiophenol
(57 mg, 0.517 mmol) and DMAP (26 mg, 0.21 mmol) were
added to [bmim][BF4] (6 cm3) contained in a 25 cm3 round-
bottomed flask. Nitrogen was blown over the reaction be-
fore it was sealed and the reaction was then stirred at room
temperature for 16 h. Stirring was stopped and the red-
brown mixture was then extracted with diethyl ether
(8 · 5 cm3). The ether extracts were combined, washed with
water and dried over anhydrous sodium sulfate. After
removing the diethyl ether in vacuo, the residue was passed
through a short silica gel column. The products were eluted
with hexane–diethyl ether (1:5) avoiding the use of undesir-
able chlorinated solvents. The product was obtained as a
dark red solid (0.127 g, 90%) and was identified as ferroce-
noyl phenyl sulfide (3). M.p. 108–109 ꢁC, lit. 108–109 ꢁC
[28]; IR (KBr/cmÀ1) 2950, 1664, 1614, 1438, 1239, 1044,
4.7.2. With benzophenone oxime: benzophenone O-
ferrocenylcarbonyloxime (6)
Quantities. Ferrocenoyl fluoride (102 mg, 0.44 mmol),
benzophenone oxime (88 mg, 0.446 mmol), DMAP
(25 mg, 0.205 mmol) and [bmim][BF4] (6 cm3). The product
was obtained as a yellow solid identified as benzophenone
O-ferrocenylcarbonyloxime (6) (0.169 g, 94%), M.p. 130–
131 ꢁC, (lit. [28] 130–131 ꢁC); IR (KBr cmÀ1) 3675, 3013,
2935, 2856, 1735, 1655, 1527, 1452, 1376, 1327, 1266,
1227, 1218, 1100, 1024, 985, 915; 1H NMR (CDCl3)

C. Imrie et al. / Journal of Organometallic Chemistry 690 (2005) 4959–4966
4965
7.70–7.40 (10H, m, ArH), 4.60 (2H, t, J = 1.8 Hz, C5H4),
4.36 (2H, t, J = 1.8 Hz, C5H4), 4.10 (5H, s, C5H5); 13C
NMR (CDCl3) 169.4, 164.8, 135.1, 133.3, 131.6, 129.9,
129.4, 129.1, 128.8, 128.6, 72.0, 70.5, 70.3, 69.5; m/z 409
(M+, 100), 344 (88), 300 (61), 182 (68); Anal. Calc. for
C24H19FeNO2: C, 70.4; H, 4.7%; [M+], 409.07652. Found:
C, 70.8; H, 5.0%; [M+], 409.07748.
4.10. Solvent-free reaction of ferrocenoyl fluoride with
potassium O-ethyl xanthate: ferrocenoic thioanhydride (7)
Ferrocenoyl fluoride (0.1004 g, 4.33 · 10À4 mol), potas-
sium-O-ethyl xanthate (0.0647 g, 4.54 · 10À4 mol) and
DMAP (0.0172 g, 1.41 · 10À4 mol) were mixed and ground
in the dark. The mixture turned red after 1 min, formed a
paste after 3.5 min and was ground for a further 2 min.
The reaction mixture was taken up in dichloromethane
and subjected to column chromatography. A red band
was eluted with hexane–diethyl ether (1:3). The solvent
mixture was removed under reduced pressure and this gave
ferrocenoic thioanhydride (7) as red crystals (0.0909 g,
91%), M.p. 163 ꢁC decomp. (lit. [36] 149–150 ꢁC); IR
(KBr cmÀ1) 3448, 3107, 2931, 2362, 1761, 1692, 1652,
1565, 1477, 1435, 1376, 1044, 831, 780, 659, 494; 1H
NMR (CDCl3) 4.92 (4H, t, J = 1.9 Hz, 2 · C5H4), 4.61
(4H, t, J = 1.9 Hz, 2 · C5H4), 4.36 (10H, s, 2 · C5H5);
13C NMR (CDCl3) 187.0, 80.1, 73.3, 71.1, 70.4; m/z 458
(M+, 79 %), 442 (27), 366 (10), 350 (8), 306 (12), 274
(32), 272 (20), 214 (11), 213 (100), 209 (15), 186 (19), 185
(36), 181 (10), 131 (15), 129 (42), 119 (13), 92 (21), 69
(56); Anal. Calc. for C22H18Fe2O2S: [M+], 457.97263.
Found: [M+], 457.97259. Crude ferrocenemonocarboxylic
acid (0.0249 g) was stripped off the column with methanol.
4.8. Solvent-free reaction of ferrocenoyl fluoride with
N-hydroxypyridine-2-thione
Ferrocenoyl fluoride (0.1009 g, 4.35 · 10À4 mol), N-
hydroxypyridine-2-thione (0.0558 g, 4.39 · 10À4 mol) and
DMAP (0.0209 g, 1.71 · 10À4 mol) were mixed and ground
in an open mortar for 4 min. The mixture was analysed by
FTIR and this confirmed the formation of a new product.
The reaction mixture was taken up in a minimal amount of
dichloromethane, and was then subjected to flash column
chromatography using hexane–diethyl ether (1:3) as eluant.
Blue coloured decomposition products were evident on the
column. The eluate was concentrated under reduced pres-
sure to give N-ferrocenoyloxypyridine-2-thione (4) as red-
orange crystals (0.0860 g, 58%). The product was identical
to that characterized in Section 4.7.1.
4.11. Microwave-promoted reactions of ferrocenoyl fluoride
with phenols under solvent-free conditions: general method
4.9. Solvent-free reaction of ferrocenoyl fluoride with
3-hydroxy-4-methyl-2(3H)-thiazolethione: N-ferrocenoyl-
oxy-4-methyl-2(3H)-thiazolethione (5)
Ferrocenoyl fluoride (0.4 mmol) and a substituted phe-
nol (0.4 mmol) were thoroughly mixed in a mortar. The
mixture was subjected to microwave radiation for 1 min.
The resulting melt was allowed to cool and was passed
through a column of silica gel. Elution with hexane/ether
(1:1) provided a band that upon removing the solvent
gave the ferrocenoate ester. A small amount of ferrocen-
ecarboxylic acid was removed from the column with
methanol.
Ferrocenoyl fluoride (0.1003 g, 4.32 · 10À4 mol), 3-hy-
droxy-4-methyl-2(3H)-thiazolethione (0.0661 g, 4.49 ·
10À4 mol) and DMAP (0.0169 g, 1.38 · 10À4 mol) were
mixed and ground in an open mortar for 4 min. A dark-
red paste formed. The reaction mixture was taken up in
dichloromethane and subjected to column chromatogra-
phy. Hexane–diethyl ether (2:1) eluted ferrocenoyl fluoride
(0.0408 g). A second band was eluted with hexane–diethyl
ether (1:2). A blue residue remained on the column. Re-
moval of the solvent from the second band under reduced
pressure gave N-ferrocenoyloxy-4-methyl-2(3H)-thiazol-
ethione (5) as a red powder (0.0810 g, 52%), M.p. 133 ꢁC
decomp.; IR (KBr cmÀ1) 3103, 3083, 1786, 1642, 1590,
1559, 1508, 1451, 1400, 1372, 1338, 1324, 1266, 1178,
1136, 1106, 1058, 1020, 991, 975, 871, 859, 827, 738, 724,
Acknowledgements
The authors thank the following persons for technical
assistance: Mr. H. Marchand (UPE) for general technical
assistance and Dr. P. Boshoff (formerly of the Cape Tech-
nikon, Cape Town) for the mass spectrometric analyses.
The National Research Foundation (Pretoria) and the Uni-
versity of Port Elizabeth are gratefully acknowledged for
funding the green chemistry project.
1
528; H NMR (CDCl3) 6.27 (1H, d, J = 1.1 Hz, vinylic),
5.04 (2H, t, J = 1.7 Hz, C5H4), 4.63 (2H, t, J = 1.7 Hz,
C5H4), 4.48 (5H, s, C5H5), 2.19 (3H, d, J = 1.1 Hz, CH3);
13C NMR (CDCl3) 181.4, 168.4, 137.9, 102.8, 73.2, 71.9,
71.3, 70.6, 13.9; m/z 359 (M+, 54%), 315 (9), 281 (6), 267
(21), 260 (26), 250 (26), 243 (7), 231 (23), 230 (97), 219
(17), 213 (86), 211 (6), 193 (7), 186 (17), 185 (60), 169
(16), 165 (9), 138 (46), 131 (57), 129 (64), 119 (32), 103
(7), 100 (11), 92 (13), 86 (41), 81 (9), 72 (11), 69 (100), 64
(8), 56 (26), 45 (33), 39 (21); Anal. Calc. for C15H14Fe-
NO2S2: [M+], 358.97371. Found: [M+], 358.97302.
Appendix A. Supplementary data
Supplementary data associated with this article can be
found, in the online version, at doi:10.1016/j.jorganchem.
2005.08.015.

4966
C. Imrie et al. / Journal of Organometallic Chemistry 690 (2005) 4959–4966
[21] S-J. Ji, Z-L. Shen, D-G. Gu, S-Y. Wang, J. Organomet. Chem. 689
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