An investigation of the chemistry of ferrocenoyl derivatives. The synthesis and reactions of ferrocenoyl imidazolide and its derivatives

Article abstract of DOI:10.1016/S0022-328X(01)00915-9

Ferrocenoyl imidazolide is synthesized readily from ferrocenecarboxylic acid in one step. It is a red crystalline compound that is stable at <5°C in the dark and it acts as an efficient ferrocenoyl equivalent. It reacts rapidly with alkoxides to give esters and with thiolates to give thioesters. Its reaction with Lawesson's reagent gave diferrocenoyl disulfide. Attempts to make diferrocenoyl peroxide by reacting ferrocenoyl imidazolide with hydrogen peroxide were unsuccessful. Ferrocenoyl imidazolide is converted into triferrocenylmethanol and diferrocenyl ketone in one step by reacting it with ferrocenyl-lithium. The X-ray crystal structures of ferrocenoyl phenyl sulfide and diferrocenoyl disulfide are described.

Full text of DOI:10.1016/S0022-328X(01)00915-9

Journal of Organometallic Chemistry 637–639 (2001) 266–275
www.elsevier.com/locate/jorganchem
An investigation of the chemistry of ferrocenoyl derivatives. The
synthesis and reactions of ferrocenoyl imidazolide and its
derivatives
Christopher Imrie a,*, Leanne Cook b, Demetrius C. Levendis b
a Department of Chemistry, Uni6ersity of Port Elizabeth, PO Box 1600, 6000 Port Elizabeth, South Africa
b Department of Chemistry, Centre for Molecular Design, Uni6ersity of the Witwatersrand, Johannesburg, South Africa
Received 2 January 2001; received in revised form 16 April 2001; accepted 18 April 2001
Abstract
Ferrocenoyl imidazolide is synthesized readily from ferrocenecarboxylic acid in one step. It is a red crystalline compound that
is stable at B5 °C in the dark and it acts as an efficient ferrocenoyl equivalent. It reacts rapidly with alkoxides to give esters and
with thiolates to give thioesters. Its reaction with Lawesson’s reagent gave diferrocenoyl disulfide. Attempts to make diferrocenoyl
peroxide by reacting ferrocenoyl imidazolide with hydrogen peroxide were unsuccessful. Ferrocenoyl imidazolide is converted into
triferrocenylmethanol and diferrocenyl ketone in one step by reacting it with ferrocenyl-lithium. The X-ray crystal structures of
ferrocenoyl phenyl sulfide and diferrocenoyl disulfide are described. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Ferrocenoyl imidazolide; Ferrocenoyl equivalent; Triferrocenyl derivatives
general structure 2 (R=C8H17 and C10H21) are histori-
cally important ferrocene derivatives since they repre-
sent the first examples of ferrocenyl-containing
thermotropic liquid crystals (ferrocenomesogens) [7a].
They exhibit stable nematic liquid crystal phases. Com-
pound 3 also holds a position of some importance in
the applied chemistry of ferrocene materials since it is
one of the few sandwich compounds to be used in a
pharmaceutical treatment. It was patented in the USSR
and marketed under the name of ferrocerone and has
been used in the treatment of various conditions includ-
ing iron deficiency anaemia, severe infection of the
nasopharynx and others [8]. Finally, compound 4 is a
ferrocenyl–penicillin molecule and this molecule dis-
plays antibacterial activity [9]. The ferrocenoyl unit has
been established firmly in new molecules for use as
novel electrochemical sensors [10] and Beer and co-
workers have utilized ferrocenoyl derivatives for anion
recognition [11].
1. Introduction
The discovery of ferrocene in 1951 heralded a new
era in the realm of organometallic chemistry [1]. The
discovery is not unlike some of the other ground break-
ing discoveries in chemistry because it provided a new
direction in the subject. The events leading up to and
shortly after the discovery of ferrocene make for inter-
esting reading [2].
Amongst the first well documented reactions of fer-
rocene were the Friedel–Crafts acylation [3], the aryla-
tion using aryldiazonium salts [4] and metallation using
n-butyl lithium [5]. In more recent times, there has been
a renaissance in the chemistry of ferrocenes, particu-
larly in the area of catalysis, organic synthesis and new
materials [6].
The ferrocenoyl unit (1) has been incorporated in
many ferrocenes synthesized recently for potential in-
dustrial application. Three examples are shown in Fig.
1. Compound 2 is a liquid crystal [7] whereas 3 and 4
are potential medicinal agents [8,9]. Two compounds of
The two common methods of introducing the ferro-
cenoyl unit into a molecule are either Friedel–Crafts
acylation of ferrocene with acid halides and aluminium
trichloride [3] or the reaction of ferrocenoyl chloride
with nucleophilic reagents [12].
* Corresponding author. Fax: +27-41-504-2573.
E-mail address: chacci@upe.ac.za (C. Imrie).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00915-9

C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
267
pyridine. The compound is a stable orange solid at
room temperature and provides exceptionally high
yields of esters and amides in its reactions with alcohols
and amines, respectively.
In 1962, Staab described the use of heterocyclic
amides, commonly known as azolides, in organic syn-
thesis [16]. The azolides were shown to be highly reac-
tive in nucleophilic reactions and were used for the
synthesis of a wide range of functionalities including
esters, amides, peptides, hydrazides and hydroxamic
acids. A recent monograph appeared on this subject
providing an excellent overview of azolide chemistry
[17]. The work herein describes the use of a ferrocenyl-
containing azolide, ferrocenoyl imidazolide (5), in the
synthesis of ferrocenoyl derivatives. Ferrocenoyl imida-
zolide is easy to store and handle and provides useful
yields of ferrocenoyl derivatives at room temperature.
2. Results and discussion
2.1. Reactions of ferrocenoyl imidazolide
Ferrocenoyl imidazolide (5) was prepared in one step
from the reaction of ferrocenecarboxylic acid with N,N-
dicarbonyldiimidazole in anhydrous THF. The reaction
to give 5 was reproducible and consistently provided
the imidazolide in yields greater than 60%. The imida-
zolide 5 was isolated easily as an air-stable red solid
and was stored in a vacuum desiccator below 5 °C.
Purification of 5 was achieved either by cold recrystal-
lization or by using flash chromatography on silica gel.
A summary of the reactions of 5 is shown in Scheme 1.
Reaction of 5 with alcohols such as methanol and
ethanol at room temperature led to a slow alcoholysis
reaction to give the corresponding esters. Reaction of 5
with sodium alkoxides generated by the reaction of
alcohols with sodium was spontaneous providing good
yields of esters. Similar behaviour of 5 was observed in
its reactions with thiolate ions. For example, a reaction
between sodium thiophenolate and 5 provided an excel-
lent yield of ferrocenoyl phenyl sulfide 6. The X-ray
crystal structure determination of 6 was performed. The
molecular structure and numbering scheme for 6 are
shown in Fig. 2. Selected bond distances and bond
angles are provided in Table 1.
Fig. 1. The ferrocenoyl group and ferrocenoyl derivatives for applied
chemistry.
The Friedel–Crafts acylation was one of the first well
documented reactions in ferrocene chemistry and also
one of the first to implicate the aromatic behaviour of
the ferrocene molecule. The use of ferrocenoyl halides
especially ferrocenoyl chloride as a ferrocenoyl equiva-
lent has been widespread but it presents some major
drawbacks. Firstly, ferrocenoyl chloride is moisture
sensitive and should be used immediately after prepara-
tion; it also exhibits thermal and photochemical insta-
bility and is similar in behaviour to other ferrocenes
carrying electron-withdrawing groups adjacent to the
ferrocenyl group [13].
A ferrocenoyl derivative of interest to us a number of
years ago for the generation of ferrocenoyloxyl radicals
’
(FcCOO ) was benzophenone O-ferrocenylcarbony-
The preparation of ferrocenoyl chloride has been
reported on a number of occasions using different
reagents and reaction conditions [14]. A perhaps more
useful ferrocenoyl equivalent is ferrocenoyl fluoride. Its
synthesis and use have been described recently by Ga-
low et al. [15]. It was synthesized by the reaction of
ferrocenecarboxylic acid with cyanuric fluoride and
loxime (7) [18]. During that study on the generation of
ferrocenoyloxyl radicals, 7 was prepared by the reaction
of benzophenone oxime and ferrocenoyl chloride. We
have also prepared it using the DCC/DMAP esterifica-
tion route from ferrocenecarboxylic acid and benzophe-
none oxime. In the initial reaction between 5 and
benzophenone oxime, the reaction was performed at

268
C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
Scheme 1. Summary of the reactions of ferrocenoyl imidazolide.
room temperature with equimolar amounts of 5 and
benzophenone oxime. These conditions provided unre-
acted starting material. However, on addition of alu-
minium oxide to the same reaction, a modest yield of 7
was obtained. Photolysis of 7 in benzene provided
ferrocenecarboxylic acid (presumably formed from Fc-
Another compound that was of interest to us in
terms of the free radical chemistry of ferrocenes was
diferrocenoyl peroxide (10). This should act as a source
of ferrocenoyloxyl free radicals by either thermal or
photodecomposition. Previous attempts by Lau and
Hart [23] to synthesize 10 from ferrocenoyl chloride
and sodium peroxide were unsuccessful. Staab has re-
ported previously on the synthesis of diaroyl peroxides
from imidazolides and hydrogen peroxide. However,
the reaction of 5 with hydrogen peroxide (30%) gave a
complex mixture of organic and inorganic products.
Assuming 10 had formed, it is unlikely to withstand the
oxidizing conditions. A further problem envisaged with
10 is that of autodecomposition. Peroxide decomposi-
tion is catalyzed by metal salts such as iron(II) and so
the ferrocenyl group could interact with the peroxide
linkage. The reaction of 5 with sodium peroxide in
anhydrous ether gave a quantitative yield of sodium
’
COO ) and benzophenone and there was no evidence
for the decarboxylation product, ferrocene.
The chemistry of triferrocenylmethyl-derivatives has,
so far, been investigated little and this is most likely
because of difficulties encountered in the synthesis of
the triferrocenylmethyl unit. Triferrocenylmethanol (8)
has been synthesized by Pauson and Watts [19] from
the reaction of diferrocenyl ketone (9) and ferrocenyl–
lithium. The stumbling block in this sequence is actu-
ally the availability of diferrocenyl ketone rather than
its conversion to the triferrocenylmethanol. Diferro-
cenyl ketone has been synthesized previously by a num-
ber of methods. It has been prepared by Friedel–Crafts
acylations [20], oxidation of diferrocenylcarbinol [21],
by the reaction of bromoferrocene, n-butyllithium and
N,N-dimethyl carbamylchloride [22] and perhaps the
most cheap, convenient and efficient method by the
reaction of ferrocene, triphosgene and aluminium
trichloride [14f].
The reaction of 5 with ferrocenyl–lithium gave rise
to the formation of a mixture of triferrocenylmethanol
and diferrocenylketone in one step and this reaction
presumably proceeds through the intermediacy of difer-
rocenyl ketone. The yields of 8 and 9 were very low and
further studies are required in order to optimize these.
Fig. 2. Molecular structure of ferrocenoyl phenyl sulfide 6 with
numbering scheme

C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
269
Table 1
Despite the widespread use of the thiocarbonyl func-
tional group in organic chemistry especially in free
radical chemistry, only a few ferrocenyl thiocarbonyl
derivatives have been reported [24]. An attempt was
therefore made to convert 5 into the thiocarbonylimida-
zole derivative (11) since such a compound should act
as a precursor to a whole new range of ferrocenylthio-
carbonyl compounds by nucleophilic displacement of
the imidazole group. On adding Lawesson’s reagent (a
proven reagent for the conversion of carbonyl groups
to thiocarbonyl groups) to a solution of 5 in anhydrous
benzene, there was an almost immediate colour change
of the solution from dull red to a bright red. TLC
indicated the formation of a new ferrocene compound
after only several hours and it was several days before
this product intensified on the plate. The product was
identified as diferrocenoyl disulfide (12), a compound
that has been characterized partially before by Katada
et al. [14d]. Dibenzoyl disulfide and similar compounds
are reasonably well documented in the patent literature
and have been used in rubber technology. They were
made by reacting acid chlorides with sodium sulfide.
However, the organic chemistry of the diacyl disulfide
functional group is not extensive and further investiga-
tions of the new ferrocene compound may prove
interesting.
,
Bond lengths (A) and selected bond angles (°) for 6
Bond lengths
Fe (1)–C(1)
Fe(1)–C(4)
Fe(1)–C(10)
Fe(1)–C(5)
Fe(1)–C(6)
Fe(1)–C(2)
Fe(1)–C(9)
Fe(1)–C(3)
Fe(1)–C(7)
Fe(1)–C(8)
S(1)–C(12)
S(1)–C(11)
O(1)–C(11)
C(1)–C(2)
C(1)–C(5)
2.028(5)
2.029(4)
2.030(4)
2.031(4)
2.036(4)
2.038(5)
2.041(4)
2.044(4)
2.053(4)
2.057(4)
1.771(4)
1.788(4)
1.206(4)
1.396(7)
1.402(7)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(6)–C(7)
C(6)–C(10)
C(7)–C(8)
C(8)–C(9)
C(9)–C(10)
C(10)–C(11)
C(12)–C(13)
C(12)–C(17)
C(13)–C(14)
C(14)–C(15)
C(15)–C(16)
C(16)–C(17)
1.384(6)
1.395(6)
1.387(6)
1.403(6)
1.429(5)
1.404(6)
1.410(6)
1.440(5)
1.464(6)
1.381(6)
1.388(6)
1.382(7)
1.374(7)
1.361(7)
1.378(7)
Bond angles
C(12)–S(1)–C(11) 103.59(19)
O(1)–C(11)–C(10) 124.2(4)
C(10)–C(11)–S(1)
C(13)–C(12)–S(1)
C(17)–C(12)–S(1)
112.5(3)
122.7(3)
117.7(3)
O(1)–C(11)–S(1)
123.3(3)
The X-ray crystal structure determination of 12 was
performed. The molecular structure and numbering
scheme for 12 is shown in Fig. 3 and a packing diagram
in Fig. 4. Selected bond distances and bond angles are
provided in Table 2.
The reduction of 5 with lithium aluminium hydride
provided an efficient method of reducing ferrocenecar-
boxylic acid to either ferrocenecarboxaldehyde or to
ferrocenemethanol depending on the concentration of
the reducing agent.
Fig. 3. Molecular structure of diferrocenoyl disulfide 12 with number-
ing scheme
ferrocenoate and ferrocenecarboxylic acid was recov-
ered from this after acidification.
2.2. Structural studies of the ferrocenoyl deri6ati6es 6
and 12
There is considerable interest in the role of hydrogen
bonding and non-covalent interactions in designing
supramolecular architectures [25]. This interest extends
to hydrogen bonding effects in ferrocenes [26]. For this
reason, the X-ray crystal structure of 12 will be dis-
cussed first since it exhibits some very interesting hydro-
gen bonding interactions. The unit cell of 12 is
orthorhombic and the bond lengths fall within the
expected limits (Table 2). The bond distance between
,
S(1) and S(2) [2.022(2) A] is close to that found in
related compounds. For example, the S–S bond dis-
,
tance in dibenzoyl disulfide is 2.021(2) A [27] and in
,
bis(morpholinothiocarbonyl)disulfide is 2.009(5) A [28].
,
The S–C bond distances in 12 [1.815(6) and 1.817(6) A]
are also similar to those in dibenzoyl disulfide [1.811(6)

270
C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
Fig. 4. Packing diagram for 12 with a view along the c-axis showing the intramolecular and intermolecular H···OꢀC interactions.
,
when benzoylferrocene oxime is prepared by the reac-
tion of benzoylferrocene and hydroxylamine hydrochlo-
ride, the red crystalline solid consists of a mixture of
syn- and anti-isomers [32]. In the crystal, the molecules
occur as a random distribution of syn–syn or anti–anti
hydrogen bonded dimers. In the syn-isomer, there is
evidence for an intramolecular hydrogen bonding inter-
action between the OH group and one of the cyclopen-
tadienyl hydrogen atoms. The issue of whether a C–H
group can form a hydrogen bond with an electronega-
tive atom such as oxygen has been a controversial one
[33] but was apparently settled by a landmark study
that provided good evidence for the existence of C–
and 1.827(6) A]. The two cyclopentadienyl rings in the
ferrocenyl groups are more or less eclipsed and this is
the normal behaviour of the majority of monosubsti-
tuted ferrocenyl derivatives [29]. The most interesting
aspect of the crystal structure is highlighted in Fig. 4,
which shows a packing diagram with a view down the
c-axis. Looking down the c-axis, it is apparent that the
conformation of a single molecule is such that there is
a close intramolecular hydrogen bonding interaction
between one of the cyclopentadienyl hydrogens and one
of the carbonyl groups, for example between O(2) and
C(2)–H. The intramolecular bond distance O(2)···H–
,
C(2) is 2.467 A and this is well within the range for
hydrogen bonding. There is also a further hydrogen
bonding interaction which is best observed by using the
view down the b-axis. The second hydrogen bonding
interaction is again between a cyclopentadienyl hydro-
gen atom and a carbonyl oxygen group but on this
occasion, it is an intermolecular interaction. In this
case, the intermolecular bond distance O···H–C is 2.542
Table 2
,
Selected bond lengths (A) and bond angles (°) for 12
Bond lengths
Fe(1)–C(10)
Fe(1)–C(1)
Fe(1)–C(9)
Fe(1)–C(6)
Fe(1)–C(3)
Fe(1)–C(4)
Fe(1)–C(5)
Fe(1)–C(8)
2.005(6)
2.026(8)
2.024(7)
2.028(7)
2.027(7)
2.033(8)
2.038(7)
2.052(7)
Fe(1)–C(2)
Fe(1)–C(7)
C(1)–C(5)
C(1)–C(2)
S(1)–S(2)
0(1)–C(11)
S(2)–C(12)
O(2)–C(12)
2.043(8)
2.051(7)
1.412(10)
1.409(10)
2.022(2)
1.193(6)
1.817(6)
1.204(7)
,
A. Intermolecular hydrogen bonding between the cy-
clopentadienyl protons in ferrocenyl molecules and
electronegative atoms such as oxygen and nitrogen have
been reported previously. For example, they are ob-
served in the crystal structure of 4%-formyl-4-biphenyl-
ferrocene between the cyclopentadienyl hydrogen atoms
and the aldehydic carbonyl group [30]. A similar inter-
action has been reported by Sato et al. for ferrocenecar-
boxaldehyde in an investigation of the plastic crystal
phase of that molecule by X-ray diffraction [31]. In-
tramolecular hydrogen bonding interactions have also
been observed for ferrocenyl derivatives. For example,
Bond angles
C(11)–S(1)–S(2)
C(5)–C(1)–C(2)
C(12)–S(2)–S(1)
C(3)–C(2)–C(1)
C(9)–C(10)–C(11)
C(6)–C(10)–C(11)
102.7(2)
107.3(8)
100.6(2)
107.1(8)
124.7(6)
128.1(6)
O(1)–C(11)–C(10)
O(1)–C(11)–S(1)
C(10)–C(11)–S(1)
O(2)–C(12)–C(17)
O(2)–C(12)–S(2)
C(17)–C(12)–S(2)
125.2(6)
123.0(5)
111.9(5)
124.3(6)
123.0(5)
112.7(5)
C(13)–C(17)–C(12) 128.1(6)
C(16)–C(17)–C(12) 124.1(6)

C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
271
H···O hydrogen bonding in crystals [34]. However, dis-
agreement still continues as to whether a C–H···O
interaction is a hydrogen bond or a van der Waals
interaction [35].
The unit cell of compound 6 is monoclinic. The bond
lengths for 6 fall within the expected limits (Table 1).
phate. Evaporation of the solvent in vacuo afforded a
dark red solid, identified as ferrocenoyl imidazolide
(0.39 g, 63%), m.p. 121–122 °C; wmax (KBr)/cm−1 1670,
1430, 1370, 1300, 1000, 830; lH (CDCl3) 7.15–8.45 (3H,
m, imidazole), 4.90 (2H, t, J=1.8 Hz, C5H4), 4.50 (2H,
t, J=1.8 Hz, C5H4), 4.28 (5H, s, C5H5); lc (CDCl3)/
ppm: 139.2, 132.2, 119.6, 74.9, 73.7, 72.7, 71.9; m/z 281
(18%), 280 ([M+], 100%), 230 (18%), 213 (60%), 185
(57%), 138 (16%), 129 (31%), 121 (25%). Anal. Found:
C, 59.7; H, 4.3; [M+], 280.0287. Calc. for C14H12FeN2O:
C, 60.0; H, 4.3%; [M+], 280.0295.
This reaction was repeated several times and proved
to be reproducible. The product was purified by either
cold recrystallization or was passed through a silica gel
column. The compound was eluted successfully using
diethyl ether under nitrogen without undue hydrolysis
back to ferrocenecarboxylic acid.
,
The bond distances between S(1) and C(11) [1.788(4) A]
,
and S(1) and C(12) [1.771(4) A] are similar to that
found in related compound, S-(2-nitrophenyl)-
a
,
benzenecarbothiolate [1.788(12) and 1.767(5) A] [36].
The two cyclopentadienyl rings in the ferrocenyl group
are more or less eclipsed again. There are no significant
short intermolecular bonding contacts between
molecules.
3. Experimental
3.1. Purification and characterization of the materials
3.2.2. Reaction of ferrocenoyl imidazolide with sodium
methoxide
Reactions were carried out under nitrogen or argon.
Silica gel or neutral aluminium oxide was used for
column chromatography. Infrared spectra were
recorded using a Perkin–Elmer 1600 series FT-IR spec-
trometer as KBr discs or in solution using chloroform.
NMR spectra were recorded on a Varian Gemini 200
A solution of sodium methoxide was made up by
dissolving sodium metal (0.5 g, 22 mmol) in methanol (5
cm3). This solution was added to a solution of ferro-
cenoyl imidazolide (101 mg, 0.36 mmol) in methanol (10
cm3). The colour of the reaction solution changed from
red to yellow immediately. After 3 h, diethyl ether (50
cm3) was added, the solution was filtered, washed with
water, and dried over anhydrous sodium sulphate. After
removing the solvent, the residue was passed through a
short column of silica gel. A yellow band was removed
with dichloromethane:petroleum ether (1:1). Removal
of the solvent left yellow crystals of methyl ferrocenoate
(55 mg, 63%), m.p. 64–66 °C, lit. [21], 70 °C; wmax
(KBr)/cm−1 2956, 1712, 1460, 1284, 1142, 1030, 824; lH
(CDCl3) 4.80 (2H, t, J=1.8 Hz, C5H4), 4.39 (2H, t,
J=1.8 Hz, C5H4), 4.20 (5H, s, C5H5), 3.82 (3H, s, CH3);
m/z 244 ([M+], 100%), 213 (6%), 186 (2%), 185 (2%).
Anal. Found: [M+], 244.0181. Calc. for C12H12O2Fe:
[M+], 244.0185.
1
spectrometer operating at 200 MHz for H-NMR or
50.1 MHz for 13C-NMR as solutions in CDCl3 unless
otherwise stated. Melting points were determined using
a Reichert hot stage microscope or using an Electrother-
mal IA 900 series digital melting point apparatus and
are uncorrected. Mass spectra were recorded on either
an AEI MS 902/MSS update (70 eV, direct insertion
probe) or a VG70-SEQ/MSSMS2 spectrometer at the
Cape Technikon. Microanalyses were performed using a
Carlo-Erba MOD 1160 elemental analyser by the Coun-
cil for Scientific and Industrial Research (CSIR), Preto-
ria. Crystal X-ray crystallography was performed on a
Bruker/AXS SMART-CCD diffractometer at the Cen-
tre for Molecular Design, University of the Witwater-
srand. Ferrocenecarboxylic acid and N,N-carbonyl-
diimidazole were purchased from the Aldrich Chemical
company (USA) and were used without further purifica-
tion.
3.2.3. Reaction of ferrocenoyl imidazolide with sodium
ethoxide
The experimental procedure is similar to that de-
scribed in Section 3.2.2 except that ethanol (5 cm3) was
used instead of methanol. The product was ethyl ferro-
cenoate (45 mg, 48%), m.p. 62–63 °C, lit. [23], 59–
60 °C; wmax (KBr)/cm−1 2962, 1696, 1458, 1377, 1276,
1134, 1033, 826; lH (CDCl3) 4.82 (2H, t, J=1.8 Hz,
C5H4), 4.40 (2H, t, J=1.8 Hz, C5H4), 4.28 (2H, q,
CH2), 4.21 (5H, s, C5H5), 1.36 (3H, t, CH3); lc (CDCl3)
223.9, 73.2 (Fc), 72.1 (Fc), 71.7 (Fc), 62.1 (CH2), 16.7;
m/z 259 (18%), 258 ([M+], 97%), 231 (16%), 230 (100%),
213 (20%), 186 (10%), 185 (15%), 149 (62%), 138 (43%),
136 (20%), 129 (29%), 121 (36%). Anal. Found: [M+],
258.0328. Calc. for: C13H14FeO2: [M+], 258.0339.
3.2. Synthesis
3.2.1. Preparation of ferrocenoyl imidazolide (5)
A solution of ferrocenecarboxylic acid (0.5 g, 2.2
mmol) in anhydrous THF (40 cm3) was added to a
solution of N,N-carbonyldiimidazole (0.36 g, 2.2 mmol)
in THF (10 cm3). The mixture was stirred for 1 h at
room temperature (r.t.) after which it was poured onto
ice. Ether (50 cm3) was added and the solution was
washed with sodium hydrogen carbonate solution, wa-
ter and was finally dried over anhydrous sodium sul-

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C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
3.2.4. Reaction of ferrocenoyl imidazolide with sodium
propoxide
3.2.7. Reaction of ferrocenoyl imidazolide with sodium
thiophenolate
The experimental procedure is similar to that de-
scribed in Section 3.2.2 except that propan-1-ol (5 cm3)
was used instead of methanol. The product was propyl
ferrocenoate (58 mg, 59%); lH (CDCl3) 4.82 (2H, t,
J=1.8 Hz, C5H4), 4.40 (2H, t, J=1.8 Hz, C5H4), 4.21
(5H, s, C5H5), 4.18 (2H, t, CH2), 1.75 (2H, m, CH2),
1.04 (3H, t, CH3); m/z 273 (21%), 272 ([M+], 100%),
213 (9%). Anal. Found: [M+], 272.0481. Calc. for
C14H16O2Fe: [M+], 272.0499.
Thiophenol (4 cm3) and sodium were stirred in a
round-bottomed flask for 30 min. The resulting solu-
tion containing sodium thiophenolate was added to a
solution of ferrocenoyl imidazolide (114 mg, 0.41
mmol) in methanol (5 cm3). After leaving overnight at
r.t., the solution was added to diethyl ether (50 cm3),
washed with dilute sodium hydroxide solution, water
and finally dried over anhydrous sodium sulphate. Af-
ter removal of the solvent, the residue was passed
through a short column of silica gel using petroleum
ether:dichloromethane (2:3) to elute an orange band.
Removal of the solvent left an orange solid, identified
as ferrocenoyl phenyl sulfide (75 mg, 64%), m.p. 108–
109 °C; wmax (KBr)/cm−1 2950, 1664, 1614, 1438, 1239,
1044, 807; lH (CDCl3) 7.46 (5H, m, Ar), 4.94 (2H, t,
J=1.8 Hz, C5H4), 4.54 (2H, t, J=1.8 Hz, C5H4), 4.29
(5H, s, C5H5); lc (CDCl3) 192.08, 135.43, 129.59,
129.52, 128.28, 79.21, 72.45, 71.12, 69.59; m/z 323
(17%), 322 ([M+], 75%), 230 (49%), 214 (15%), 213
(100%), 186 (7%), 185 (47%), 129 (36%), 121 (23%).
Anal. Found: C, 63.4; H, 4.3%; [M+], 322.0117. Calc.
for C17H14FeOS: C, 63.4; H, 4.4%; [M+], 322.0111.
The reaction above was repeated on a larger scale
using ferrocenoyl imidazolide (500 mg, 1.8 mmol), thio-
phenol (5 cm3) and sodium (1 g, 43.5 mmol) to give the
product ferrocenoyl phenyl sulfide (490 mg, 84%).
3.2.5. Reaction of ferrocenoyl imidazolide with sodium
phenolate
A solution of sodium phenolate was prepared by
treating phenol (38 mg, 0.40 mmol) with sodium hy-
dride (12 mg, 0.50 mmol) in anhydrous dimethylfor-
mamide. This solution was added to a solution of
ferrocenoyl imidazolide (101 mg, 0.36 mmol) in anhy-
drous DMF (5 cm3). The reaction was stirred for 5 min
at r.t. and was then poured into water. The aqueous
solution was extracted with diethyl ether (3×50 cm3),
and the extracts were combined and dried over anhy-
drous sodium sulphate. The product was ferrocenyl
benzoate (32 mg, 29%), m.p. 123 °C, lit. [37], 124–
124.5 °C; wmax (KBr)/cm−1 1700, 1637, 1618, 1457,
1374, 1273, 1126, 1020, 830; lH (CDCl3) 7.17–7.49 (5H,
m, Ar), 4.98 (2H, t, J=2.1 Hz, C5H4), 4.51 (2H, t,
J=2.1 Hz, C5H4), 4.32 (5H, s, C5H5); m/z 307 (21%),
306 ([M+], 100%), 214 (51%), 213 (100%), 186 (19%),
185 (51%) 149 (10%), 129 (32%), 121 (29%). Anal.
Found: [M+], 306.0332. Calc. for C17H14FeO2: [M+],
306.0339.
3.2.8. Reaction of ferrocenoyl imidazolide with lithium
aluminium hydride
Ferrocenoyl imidazolide (200 mg, 0.71 mmol) was
added to a solution of diethyl ether (50 cm3) containing
lithium aluminium hydride (20 mg, 0.53 mmol). The
solution was stirred for 15 min at r.t. after which it was
added to cold water containing ethyl acetate. The solu-
tion was extracted with diethyl ether (3×50 cm3) and
the combined ether extracts were dried over anhydrous
sodium sulphate. The oil remaining after removal of the
solvent was passed through a short column of alu-
minium oxide. A red band was removed from the
column with petroleum ether (40–60 °C):diethyl ether
(10:1) that on removing the solvent left a red solid,
identified as ferrocenecarboxaldehyde (80 mg, 52%),
m.p. 118 °C, lit. [38], 124–125 °C; wmax (KBr) 1650,
1440, 1405, 1240, 1020, 1000, 810; lH 9.96 (1H, s,
CHO), 4.80 (2H, t, J=1.8 Hz, C5H4), 4.61 (2H, t,
J=1.8 Hz, C5H4), 4.28 (5H, s, C5H5); m/z 215 (14%),
214 (100%), 186 (66%), 184 (10%). Anal. Found: [M+],
214.0073. Calc. for C11H10FeO: [M+], 214.0080.
3.2.6. Reaction of ferrocenoyl imidazolide with
benzophenone oxime
Ferrocenoyl imidazolide (100 mg, 0.36 mmol) and
benzophenone oxime (71 mg, 0.36 mmol) were added to
anhydrous dichloromethane (40 cm3). To this solution
neutral aluminium oxide was added and the solution
was stirred at r.t. for 12 h. The solution was then
filtered and the solvent was removed in vacuo to leave
an orange solid. This was passed through a column of
neutral aluminium oxide and the yellow band removed
from the column using dichloromethane gave the
product, benzophenone O-ferrocenylcarbonyloxime (7)
(50 mg, 34%), m.p. 130–131 °C; wmax (KBr)/cm−1
1730, 1440, 1370, 1320, 1255, 1090, 1020, 910; lH
(CDCl3) 7.40–7.70 (10H, m, Ar), 4.60 (2H, t, J=1.8
Hz, C5H4), 4.36 (2H, t, J=1.8 Hz, C5H4), 4.10 (5H, s,
C5H5); lc (CDCl3) 132.8, 131.5, 131.0, 130.7, 130.4,
130.2, 73.6 (Fc), 72.1 (Fc), 71.9 (Fc); m/z 409 ([M+],
100%), 344 (88%), 300 (61%), 182 (68%). Anal. Found:
C, 70.7; H, 5.0; [M+], 409.080. Calc. for C24H19FeNO2:
C, 70.4; H, 4.7%; [M+], 409.267.
3.2.9. Reaction of ferrocenoyl imidazolide with an
excess of lithium aluminium hydride
Ferrocenoyl imidazolide (200 mg, 0.71 mmol) was
added to a solution of diethyl ether (50 cm3) containing
lithium aluminium hydride (100 mg, 2.6 mmol). The

C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
273
3.2.11. Reaction of ferrocenoyl imidazolide with
Lawesson’s reagent
solution was stirred for 3 h at r.t. after which it was
added to cold water containing ethyl acetate. The solu-
tion was extracted with diethyl ether (3×50 cm3) and
the combined ether extracts were dried over anhydrous
sodium sulphate. The yellow oil remaining on removing
the solvent was passed through a short column of silica
gel. A yellow band was removed from the column with
diethyl ether that on removing the solvent left a yellow
solid, identified as hydroxymethylferrocene (136 mg,
89%), m.p. 80–82 °C, lit. [39], 82 °C; lH (CDCl3) 4.31
(2H, s, CH2), 4.22 (2H, t, J=1.8 Hz, C5H4), 4.16 (5H,
s, C5H5), 4.15 (2H, t, J=1.8 Hz, C5H4), 2.04 (1H, s,
OH); m/z 217 (13%), 216 ([M+], 100%), 200 (8%), 186
(8%). Anal. Found: [M+], 216.0229. Calc. for
C11H12OFe: [M+], 216.0237.
Ferrocenoyl imidazolide (200 mg, 0.71 mmol) was
added to a solution of anhydrous benzene (20 cm3) to
which was added 2,4-bis (4-methoxyphenyl)-1,3-dithia-
2,4-diphosphetane-2,4-disulfide (Lawesson’s reagent)
(287 mg, 0.71 mmol). The solution was stirred for ca.
20 days at r.t. until TLC indicated complete consump-
tion of the starting material. The solvent was evapo-
rated and the residue was extracted into ether. The
ether extract was washed with water (3×50 cm3) and
was then dried over sodium sulphate. The final residue
was passed through a column of aluminium oxide. A
red band was removed using petroleum ether (40–
60 °C)–dichloromethane which gave after removing
the solvent diferrocenoyl disulfide as a red solid (90 mg,
52%), m.p. 182–184 °C dec.; wmax (KBr)/cm−1 1680,
1433, 1237, 1042, 1024, 792; lH (CDCl3) 5.00 (4H, t,
J=1.8 Hz, 2×C5H4), 4.60 (4H, t, J=1.8 Hz, 2×
C5H4), 4.41 (10H, s, 2×C5H5); m/z 492 (2%), 491 (4%),
490 ([M+], 14%), 304 (3%), 288 (5%), 246 (27%), 214
(15%), 213 (100%), 187 (9%), 186 (6%), 185 (32%).
Anal. Found: C, 53.6; H, 3.8; [M+], 489.9440. Calc. for
C22H18Fe2O2S2: C, 53.9; H, 3.7%; [M+], 489.9445.
3.2.10. Reaction of ferrocenoyl imidazolide with
ferrocenyl-lithium
n-Butyl-lithium (5 cm3 of a 1.6 M solution) was
added over a period of 10 min to a solution of fer-
rocene (1.0 g, 5.4 mmol) in anhydrous diethyl
ether:THF (50 cm3) (1:1). The solution was stirred at
0 °C for 5 h. A solution of ferrocenoyl imidazolide (200
mg, 0.7 mmol) in dry THF (10 cm3) was added drop-
wise and the solution immediately took on a darker
colour. After stirring overnight at r.t., the solution was
added to cold water after which the layers were sepa-
rated. The organic layer was washed with water several
times and then dried over anhydrous sodium sulphate.
Removal of the solvent left an orange oil that was
placed on a column of neutral aluminium oxide. Elu-
tion with petroleum ether (40–60 °C) gave unreacted
ferrocene (0.6 g, 60%); a second yellow band was eluted
using petroleum ether:diethyl ether (9:1) followed
finally by a red band removed using petroleum
ether:diethyl ether (1:1). The second yellow band gave
after evaporation of solvent a yellow solid identified as
triferrocenylmethanol (8) (35 mg, 9%), m.p. 165–
166 °C dec., lit. [21], 160–162 °C; wmax (KBr) 3571,
3096, 2929, 2856, 1790–1570 (br), 1468, 1411, 1388,
1316, 1234, 1110, 1074, 1051, 1017, 1000, 823, 738, 647,
575, 478; lH (CDCl3) 4.07 (15H, s, 3×C5H5), 4.06 (6H,
t, J=1.8 Hz, 3×C5H4), 3.99 (6H, t, J=1.8 Hz, 3×
C5H4); lc (CDCl3) 99.73, 69.21, 67.90, 67.14; m/z 585
(18%), 584 ([M+], 45%), 568 (15%), 567 (5%), 447
(33%), 446 (100%), 444 (17%), 398 (12%), 278 (39%),
323 (22%), 260 (12%), 186 (17%). Anal. Found: [M+],
584.0177. Calc. for C31H28OFe3: [M+], 584.0180. The
red band gave diferrocenyl ketone (9) (30 mg, 11%);
wmax (KBr)/cm−1 3208, 3125, 1610, 1467, 1380, 1295,
1203, 1109, 1056, 1030, 1012, 838, 820, 808, 772, 580,
479; lH (CDCl3) 4.93 (4H, t, J=1.8 Hz, C5H4), 4.46
(4H, t, J=1.8 Hz, C5H4), 4.13 (10H, s, C5H5); lc
(CDCl3) 71.85, 71.01, 70.37; m/z 399 (27%), 398 ([M+],
100%), 214 (10%), 199 (10%), 186 (24%).
3.2.12. Reaction of ferrocenoyl imidazolide with sodium
peroxide
Ferrocenoyl imidazolide (100 mg, 0.36 mmol) was
added to anhydrous diethyl ether (20 cm3) to which was
added sodium peroxide (48 mg, 0.63 mmol). The solu-
tion was stirred at room temperature until TLC indi-
cated that all the starting material had reacted. The
reaction mixture was then quenched in water and the
aqueous solution was acidified with dilute hydrochloric
acid. This solution was then extracted with ether and
the ether extracts were washed with water and then
dried. Removal of the ether left ferrocenecarboxylic
acid (45 mg, 54%); wmax/cm−1 3500–2700, 1650, 1465,
1390, 1280, 1150, 1100, 1020, 820; lH (CDCl3) 4.80
(2H, t, J=1.8 Hz, C5H4), 4.45 (2H, t, J=1.8 Hz,
C5H4), 4.25 (5H, s, C5H5).
3.3. Preparation of benzophenone
O-ferrocenylcarbonyloxime
Ferrocenecarboxylic acid (2.17 g, 9.43 mmol) was
dissolved in anhydrous dichloromethane to which ben-
zophenone oxime (1.67 g, 8.47 mmol), 4-dimethyl-
aminopyridine (0.42 g, 3.44 mmol) and dicyclohexyl-
carbodiimide (3.16 g, 15.32 mmol) were added in suc-
cession. The solution was allowed to stir at r.t.
overnight after which the solution was filtered and then
the solvent removed under vacuum. The residue was
analysed by TLC using dichloromethane as the

274
C. Imrie et al. / Journal of Organometallic Chemistry 637–639 (2001) 266–275
developer and the alumina plate showed two spots,
Rf=0.01 and 0.51. The residue was separated using
column chromatography and dichloromethane eluted
the first fraction. After removing the solvent, an orange
solid was obtained, identified as benzophenone O-ferro-
cenylcarbonyloxime (1.07 g, 31%), m.p. 130–131 °C;
wmax (KBr)/cm−1 1730, 1440, 1370, 1320, 1255, 1090,
1020, 910; lH (CDCl3) 7.70–7.30 (10H, m, Ar), 4.60
(2H, t, J=1.8 Hz, C5H4), 4.38 (2H, t, J=1.8 Hz,
C5H4) 4.11 (5H, s, C5H5); m/z 409 ([M+], 100%), 344
(88%), 300 (61%), 182 (68%). Anal. Found: C, 70.7; H,
5.0; [M+], 409.080. Calc. for C24H19FeNO2: C, 70.4; H,
4.7%; [M+], 409.267.
Acknowledgements
C.I. gratefully acknowledges financial support from
the University of Port Elizabeth. C.I. wishes to thank
Harold Marchand (UPE), Benita Barton (formerly of
UPE), Jason van Rooyen and Dr Phil Boshoff (Cape
Technikon, Cape Town) for technical assistance. He
would also like to thank Dr Christa Loubser (Cape
Town) with whom he shared many hours discussing the
chemistry of ferrocenes during the period 1992–2000.
Finally, C.I. would like to thank Dr D.C. Nonhebel
and especially Professor P.L. Pauson (University of
Strathclyde, Glasgow) for introducing him to the chem-
istry of ferrocenes in 1985.
3.4. Crystal structure determination
3.4.1. Crystal data for 6
References
Mr=322.19 g mol−1, dark red prism, size 0.36×
0.10×0.08 mm, monoclinic, space group P21/n,
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a=12.1267(9), b=10.2687(8), c=12.5496(9) A, V=
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1434.01(19) A , T=293 K, Z=4, zcalc=1.492 g cm−3
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,
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3.4.2. Crystal data for 12
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,
a=11.5785(8), b=12.8171(9), c=13.3831(9) A, V=
3
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0.0859, R1all= 0.1203, ꢀR2all=0.0987, goodness-of-
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4. Supplementary material
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC no. 153994 for compound 6 and
CCDC no. 153995 for compound 12. Copies of this
information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2
1EZ, UK (Fax: +44-1223-336-033; e-mail: deposit@
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