Synthesis and molecular structure of a novel ferrocene-containing macrocyclic acyl thiourea derivative

Article abstract of DOI:10.1016/S0022-328X(01)00905-6

Reaction of 1,1′-bis[carbonyl isothiocyanate]ferrocene with 1,2-phenylenediamine affords both polymeric and macrocyclic products. The structure of the macrocyclic product was determined by single crystal X-ray diffraction analysis and compared with those of other ferrocene-containing acyl thiourea derivatives obtained previously.

Full text of DOI:10.1016/S0022-328X(01)00905-6

Journal of Organometallic Chemistry 637–639 (2001) 204–208
www.elsevier.com/locate/jorganchem
Synthesis and molecular structure of a novel ferrocene-containing
macrocyclic acyl thiourea derivative
Ling-yun Zhang a,*, Yao-feng Yuan a, Ai-guo Hu a, Ji-tao Wang a, Jie Sun b
a Department of Chemistry, National Key Laboratory of Elemento-Organic Chemistry, Nankai Uni6ersity, Tianjin,
300071, People’s Republic of China
b Institute of Organic Chemistry, Chinese Academy of Science, Shanghai, 200032, People’s Republic of China
Received 26 December 2000; received in revised form 3 February 2001; accepted 9 March 2001
Abstract
Reaction of 1,1%-bis[carbonyl isothiocyanate]ferrocene with 1,2-phenylenediamine affords both polymeric and macrocyclic
products. The structure of the macrocyclic product was determined by single crystal X-ray diffraction analysis and compared with
those of other ferrocene-containing acyl thiourea derivatives obtained previously. © 2001 Elsevier Science B.V. All rights reserved.
Keywords: Ferrocene derivatives; Hydrogen bonding; Acyl thiourea; Crystal structures
thesis, structural elucidation, electrochemistry, in-
tramolecular hydrogen bonding studies and
1. Introduction
The synthesis, structure, electrochemistry and coordi-
nation behaviors of ferrocenophanes have attracted
considerable attention in recent years [1–6]. Most of
the ferrocenophanes reported to date feature crown
ether or cryptand-like structures in which a ferrocenyl
group acts as a redox spectator and provides a molecu-
lar ball-bearing skeleton [6].
With the presence of several electron-donating
atoms, acyl thiourea compounds are known for their
coordination particularly with transition metals [7–12].
Koch et al. studied the crystal structure of a series of
acylthioureas and their complexes with platinum-group
metals. The nature of the intramolecular hydrogen
bond in these compounds was elucidated [8–13]. Beer
et al. reported a ferrocenyl-containing acyl thiourea
containing a strong intramolecular hydrogen bond and
proposed that the hydrogen bond prevents it from
binding H2PO−4 as a host [14].
coordination behavior towards transition metals of a
series of ferrocene-containing acyl thiourea derivatives
[16–18]. Intramolecular hydrogen bonding between
acyl and hydrogen atom on N% (ferrocene-containing
mono-substituted acyl thiourea derivatives 1 and fer-
rocene-containing disubstituted acyl thiourea deriva-
tives 2) was found to be common in this kind of
compound (Scheme 1). A planar six-membered ring
was often observed. While in the absence of hydrogen
atom on N%, another inter-side chain hydrogen bond
forms between carbonyl and hydrogen on N-(1-[N-for-
myl-N%,N%-disubstituted
thiourea]-1%-[N%,N%-disubsti-
tuted amide]ferrocene derivatives 3. In continuation of
our interest, we have synthesized the novel ferro-
cenophane which incorporates an aromatic and acyl
thiourea subunit in the bridging chain in addition to the
ferrocene moiety. In an attempt to synthesize a new
ferrocene-containing macrocyclic acyl thiourea by the
reaction of 1,1%-bis[formylisothiocyanate]ferrocene with
aromatic diamines, a contest between polymerization
and cyclization was observed in the case of 1,2-
phenylenediamine. We report herein a new synthesis,
characterization, crystal structure and intramolecular
hydrogen bonding studies of the unique ferrocene-con-
taining macrocyclic acyl thiourea derivative.
Since we reported the crystal and molecular structure
of N-(ferrocenylcarbonyl)-N%-naphthyl thiourea in 1994
[15], our research group has been engaged in the syn-
* Corresponding author. Present address: Department of Chem-
istry, University of British Columbia, 2036 Main Mall, Vancouver
BC, Canada, V6T 2G3. Fax: +1-604-8222847.
E-mail address: lyzhang@chem.ubc.ca (L.-y. Zhang).
0022-328X/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0022-328X(01)00905-6

L.-y. Zhang et al. / Journal of Organometallic Chemistry 637–639 (2001) 204–208
205
only polymer forms were isolated in the cases of 1,3-
and 1,4-pheylenediamine. In 1,2-phenylenediamine, the
distance of the two nitrogen atoms is comparable to
that of the cyclopentadiene rings in ferrocene. However,
in 1,3- and 1,4-phenylenediamines, the two nitrogen
atoms are too far away to form a cycle without destroy-
ing the intramolecular hydrogen bonds. Consequently,
the hydrogen bonding may be the driving force of the
formation of the cyclic structure.
2. Results and discussion
The reaction of 1,1%-bis[formylisothiocyanate]ferro-
cene with 1,2-phenylenediamine affords both polymeric
and cyclic products as described in Scheme 2.
Due to the poor solubility of the polymer, it precipi-
tated from the reaction mixture. It is noteworthy that
red crystals of the cyclic structure were obtained on
concentration and cooling of the filtrate. The cyclic
product appears to be the first example of the fer-
rocene-containing macrocyclic acyl thiourea to the best
of our knowledge. Under the same reaction conditions,
A strong absorption at 1655.3 cm−1 is ascribed to
the stretching vibration of the carbonyl groups. The
decrease in wavenumber in comparison with normal
carbonyl absorptions can be rationalized by both their
conjugation with cyclopentadienyl rings and the forma-
tion of intramolecular hydrogen bonds. A very strong
band at 1511.8 cm−1 is allocated as l(CNH). w(NCO)
is observed at 1278.8 cm−1. It is weaker than both
w(CO) and l(CNH), due to a mixed vibration involving
–N–CꢀO and N–H modes, which may result from the
hydrogen bonding. The medium peak at 3405 cm−1 is
attributed to the stretching vibration of NH groups
adjacent to carbonyl groups. The broad and weak
bands in the region 3010–3259 cm−1 are classified as
the stretching vibration of N%–H as the result of hydro-
gen bonding. The medium band at 1423.4 cm−1 is
supposed to be w(CꢀS) as reported before [16–18].
Like its acyclic analogs, the chemical shifts of the
protons on N% which forms hydrogen bonds appears at
11.68 ppm while that of the protons on the nitrogen
atoms adjacent to carbonyl groups is observed at 8.07
ppm. However, there exists some difference in the
cyclopentadienyl proton absorption. In 2, there are two
singlets at 4.72 and 4.92 ppm corresponding to the
Scheme 1. Intramolecular hydrogen bonding behavior in ferrocene-
containing acyl thiourea derivatives: monosubstituted (1), disubsti-
tuted (2), inter-side-chain hydrogen binding (3).
1
meta- and ortho-hydrogens, respectively. The H-NMR
spectrum of 4 consists of three singlets in this region.
The peaks appear at 4.57, 4.86 and 5.36 ppm with a
ratio of 2:1:1. This can be explained as such: in acyclic
2, the single bond between cyclopentadienyls and car-
bonyls can rotate freely. As a result, the two ortho-posi-
tions are non-differentiable in 1H-NMR. While in 4, the
formation of the cyclic structure restricted the rotation,
thus the two ortho-hydrogen atoms have different
chemical environments. Owing to the shielding effects
of the carbonyl groups, proton a should appear a little
more upfield than b. The protons at meta-positions give
signals at 4.57 ppm.
The cyclic voltammetric behavior of the macrocyclic
product 4 was studied using CH2Cl2 as solvent. Atten-
tion was essentially centered on the FeII“FeIII oxida-
tion process in the product. The scan rate varied over
the 100–200 mV.s−1 range. The anodic (Epa) and ca-
thodic (Epc) peak potentials, as well as the half wave
potential E1/2 (E1/2=0.5(Epa+Epc)) [19], were deter-
mined. For comparison, the parent compound fer-
rocene was also determined in the measurements. The
cyclic voltammograph of 4 consists of one pair of redox
Scheme 2. Contest between polymerization and cyclization.

206
L.-y. Zhang et al. / Journal of Organometallic Chemistry 637–639 (2001) 204–208
Table 1
In comparison with the molecular structure of 2, we
can find in 4 larger dihedral angles between the two
cyclopentadiene planes and the hydrogen bonding
planes. This cyclic tension may be responsible for its
poor reversibility in cyclic voltammetry.
Crystal and data collection parameters for compound 4
Empirical formula
Formula weight
Crystal color, habit
Crystal dimensions (mm)
Crystal system
C20H18O3S2N4Fe
482.35
Red, prismatic
0.2×0.3×0.3
Triclinic
The sandwich structure of ferrocene has attracted
much attention from researchers in molecular recogni-
tion [3,4,6,14]. The two coplanar cyclopentadienyl rings
may rotate with respect to each other about the iron
center. As long as there are suitable functional groups
for the substrate to bind on the substituents in the
1,1%-disubstituted ferrocene system, the side chains can
rotate to the optimal spatial arrangement selectively
and organize the correct conformation as a receptor, in
spite of steric hindrances, thus providing an element for
molecular recognition [1–4]. We determined the crystal
structure of the coordination compound of copper
chloride and 2. Copper(II) was reduced to copper(I)
during the coordination process. The two sidechains of
2, instead of enclosing copper(I) within a ball, rotate to
the inverse side of ferrocene and form an infinite chain
with copper(I). Three sulfur and one chloride coordi-
nate to copper(I) in a tetragonal configuration with a
strict C3 symmetric factor. The entire molecule is an
interlocked polymer [7]. As the two sidechains in 4 are
fixed by the macrocycle structure, we synthesized its
coordinate compounds with bivalent transition metal
ions. However, their solubility in common organic sol-
vents is very poor. This hinders further investigation.
(
Space group
Unit cell dimensions
P1 (no. 2)
,
a (A)
10.546(1)
11.098(3)
9.370(2)
114.26(2)
95.87(2)
91.38(2)
992.0(4)
2
,
b (A)
,
c (A)
h (°)
i (°)
k (°)
3
,
V (A )
Z
Dcalc (g cm−3
)
1.615
10.02
v(Mo–Ka) (cm−1
Diffractometer
Radiation
)
Rigaku AFC7R
Mo−Ka (u=0.71069 A)
29391
ꢀ–2q
(0.89+0.30tan q)
50
Total 3710, unique 3499
0.81/−0.53
2.38
,
Temperature (K)
Scan type
Scan width
2qmax (°)
Reflections measured
Dz (e−
A
)
−3
,
Goodness-of-fit
R
Rꢀ
0.054
0.071
R=ꢀꢁꢁFoꢁ−ꢁFcꢁꢁ/ꢀꢁFoꢁ, Rꢀ=[ꢀꢀ(ꢁFoꢁ−ꢁFcꢁ)2/ꢀꢀFo2)]1/2
.
3. Experimental
peaks with E1/2 at 0.980 V (vs. SCE), which is higher
than that of unsubstituted ferrocene (0.428 V), indicat-
ing that the side chains exert an electron-withdrawing
effect on the ferrocene unit and result in a decrease of
its electron density. The experimentally determined an-
odic and cathodic peak current (ipa and ipc) ratio ipc/ipa
reaches 0.24, reflecting its poor redox reversibility.
Single crystal X-ray diffraction reveals that the in-
tramolecular hydrogen bonds still exist in the two acyl
thiourea spacers between ferrocenyl and phenyl units in
the macrocyclic structure. Table 1 shows crystal and
data collection parameters. Selected bond distances and
angles are listed in Table 2. In each molecule, there
exists two independent intramolecular hydrogen bonds
between the carbonyl oxygen and the hydrogen atom
on N% in either –C(O)–NH–C(S)–N%H– moiety, form-
ing two six-membered rings. The planar rings are ap-
proximately in the same plane with the cyclo-
pentadienyl rings to which they are attached. The
phenyl ring is basically perpendicular to the ferrocenyl
unit. The molecular structure of compound 4 is de-
picted in Fig. 1. Tables 3 and 4 list the least-square
planes of relevant groups and the dihedral angles be-
tween them.
3.1. General procedures
All the reagents were of analytical grade. Elemental
analysis for C, H, N was performed on a CHN-COR-
DERM7-3 autoanalyzer. Melting points were deter-
mined on a PHMK melting point apparatus (made in
Germany) and uncorrected. 1H-NMR spectra were
recorded on a JEOLFX-90QNMR, using CDCl3 as
solvent, TMS as internal standard. IR spectra were
carried out with a Nicolet-FT-IR5-DX infrared spec-
trophotometer using KBr pellets. Cyclic voltammetric
experiments were performed on a BAS-100B electro-
chemical analyzer equipped with a three-electrode as-
sembly with 0.1 mol l−1 n-Bu4NPF6 as support
electrolyte and CH2Cl2 as solvent. The working elec-
trode was a platinum disk 1.5 mm in diameter embed-
ded in
a
cobalt glass seal and was polished
consecutively with polishing alumina and diamond sus-
pensions between runs. The reference electrode was a
KCl saturated calomel electrode. A platinum filament
was used as an auxiliary electrode. The solutions were
saturated and blanketed with N2 before the first scan.
Measurements were made at room temperature.

L.-y. Zhang et al. / Journal of Organometallic Chemistry 637–639 (2001) 204–208
207
3.2. Synthesis of 1,1%-bis( formylisothiocyanate)-
and Fc(CONCS)2 was purified on silica thin layer
ferrocene
chromatogaphy.
KSCN (0.213 g, 2.2 mmol) was dissolved in 15 ml
acetone and added dropwise to the 20 ml acetone
solution of 0.311 g (1 mmol) Fc(COCl)2 and refluxed
for 30 min. A red solution obtained on filtration of KCl
3.3. Synthesis of 4
1,2-Phenylenediamine (0.0864 g, 0.8 mmol) dissolved
in 20 ml acetone was added dropwise to the acetone
Table 2
,
Selected bond distances (A) and angles (°)
Atom
Atom
Distance
Atom
Atom
Distance
Fe
Fe
Fe
Fe
Fe
Fe
Fe
Fe
Fe
Fe
S(1)
S(2)
C(3)
C(4)
C(5)
C(6)
2.041(5)
2.055(5)
2.057(5)
2.058(6)
2.036(6)
2.042(5)
2.048(5)
2.045(6)
2.048(6)
2.035(6)
1.662(5)
1.656(6)
N(4)
N(4)
C(2)
C(15)
O(1)
O(2)
N(1)
N(1)
N(2)
N(2)
N(3)
N(3)
C(14)
C(15)
C(3)
C(16)
C(2)
C(15)
C(1)
C(2)
C(1)
C(8)
C(13)
C(14)
1.410(7)
1.378(7)
1.466(7)
1.479(7)
1.213(6)
1.228(6)
1.393(7)
1.382(7)
1.340(7)
1.445(7)
1.437(7)
1.336(7)
C(7)
C(16)
C(17)
C(18)
C(19)
C(20)
C(1)
C(14)
Atom
Atom
Atom
Angle
Atom
Atom
Atom
Angle
O(1)
O(1)
N(1)
Fe
C(2)
C(2)
N(3)
O(2)
O(2)
N(4)
Fe
C(2)
C(2)
C(2)
C(3)
C(3)
C(3)
C(14)
C(15)
C(15)
C(15)
C(16)
C(16)
C(8)
N(1)
C(3)
C(3)
C(2)
C(4)
122.6(5)
121.4(5)
116.0(5)
123.2(3)
128.3(5)
124.4(5)
116.4(5)
122.6(5)
122.0(5)
115.4(5)
124.1(3)
129.1(5)
118.4(5)
C(1)
C(1)
C(13)
C(14)
S(1)
N(1)
N(2)
N(3)
N(4)
C(1)
C(2)
C(8)
127.3(4)
120.0(4)
120.6(4)
127.2(4)
119.9(4)
125.0(4)
115.2(5)
117.4(4)
121.3(5)
125.2(4)
118.4(4)
121.8(5)
123.4(5)
C(14)
C(15)
N(1)
N(2)
N(2)
C(8)
C(12)
N(3)
N(4)
C(9)
C(7)
S(1)
C(1)
C(1)
N(4)
N(4)
C(16)
C(16)
C(15)
C(17)
C(13)
N(1)
N(3)
N(3)
S(2)
S(2)
N(2)
C(15)
C(13)
C(13)
C(14)
C(14)
C(8)
C(15)
N(2)
C(16)
C(20)
Fig. 1. Molecular structure of the title compound showing the atomic labeling scheme.

208
L.-y. Zhang et al. / Journal of Organometallic Chemistry 637–639 (2001) 204–208
Table 3
e-mail: deposit@ccdc.cam.ac.uk or www: http://
www.ccdc.cam.ac.uk).
Least-square planes between planes
Atoms of plane
Average deviation of an atom
,
from the plane (A)
Acknowledgements
1. C(8), C(9), C(10), C(11),
C(12), C(13)
2. S(2), O(2), N(3), N(4),
C(14), C(15)
3. S(1), O(1), N(1), N(2),
C(1), C(2)
4. C(3), C(4), C(5),C(6),C(7)
0.008(6)
0.045(4)
0.056(4)
0.003(5)
This work is supported by the National Natural
Science Foundation of China (Grant No. 29571020 and
29872018) and State Key Laboratory of Elemento-Or-
ganic Chemistry at Nankai University.
5. C((16), C(17), C(18), C(19), 0.003(6)
C(20)
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