Introduction of FeCp+ to o-, m-, p-terphenyl and the structures of mononuclear and dinuclear complexes

Article abstract of DOI:10.1016/j.poly.2005.07.002

FeCp⁺ complexes of o-, m-, and p-terphenyl were synthesized. Mass spectra showed the existence of mononuclear and dinuclear complexes in all isomers. Mononuclear and dinuclear complexes were separated by using the difference in solubility to CH

Full text of DOI:10.1016/j.poly.2005.07.002

Polyhedron 24 (2005) 1798–1802
www.elsevier.com/locate/poly
Introduction of FeCp+ to o-, m-, p-terphenyl and the structures
of mononuclear and dinuclear complexes
a
a
b,
a
Naoji Masuhara , Yuriko Kamigaki , Satoru Nakashima *, Tsutomu Okuda
a
Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan
Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University, Kagamiyama, Higashi-Hiroshima 739-8526, Japan
b
Received 7 September 2004; accepted 1 July 2005
Available online 10 August 2005
Abstract
FeCp+ complexes of o-, m-, and p-terphenyl were synthesized. Mass spectra showed the existence of mononuclear and dinuclear
complexes in all isomers. Mononuclear and dinuclear complexes were separated by using the difference in solubility to CH2Cl2.
X-ray structural analyses revealed that the FeCp+ was introduced to the central benzene in the mononuclear complexes, while they
were introduced to the terminal benzenes in the dinuclear complexes. 57Fe Mo¨ssbauer spectra showed arene-type FeII doublet.
Ó 2005 Elsevier Ltd. All rights reserved.
Keywords: Arene complexes; Terphenyl; X-ray structure; 57Fe Mo¨ssbauer spectroscopy
1. Introduction
not reported. The introduced number and position of
transition metal to cyclophanes are also an interesting
problem [6,9]. The introduction of FeCp+ to the carbon
hexagonal plane of the sp2-carbon has a possibility to pro-
vide a novel property to carbon materials [10]. The chem-
istry of organo-iron complexes of aromatic compounds is
interesting from the point of redox reaction [6]. Arene
complexes are also important in the synthesis of metallo-
dendrimers [11].
A great number of studies concerning metal–metal
interactions in mixed-valence biferrocene derivatives
have been carried out for a long time [1–3]. The property
of electron transfer in a molecule is greatly important in
studying superconductive materials and biological
system. By introducing an iron atom to the benzene
ring in organic compounds, it becomes possible to study
the electron transfer process in organic compounds by
using 57Fe Mo¨ssbauer spectroscopy. The mixed-valence
state for arene-type complex such as [(FeCp*)2(diphe-
nyl)]m+, [(FeCp*)2(pentalene)]m+, or [(FeCp*)2(inda-
cene)]m+ has been reported [4,5]. It is already known
that mononuclear and dinuclear derivatives are obtained
by introducing FeCp+ to p-terphenyl [6]. Although its
dinuclear complex has been assigned by 13C NMR
spectrum [7,8], the separation of mononuclear and dinu-
clear derivatives and their X-ray structural analyses are
In the present study, the introduction of FeCp+ to
o-, m-, and p-terphenyl is examined and we confirmed
the introduced number and position by using single
crystal X-ray structural analysis. The electronic state is
also discussed by using 57Fe Mo¨ssbauer spectroscopy.
2. Experimental
2.1. Preparations
24.2 g (130 mmol) of ferrocene, 17.3 g (130 mmol)
of AlCl3, 0.235 g (8 mmol) of Al powder, and 2 g
(8.7 mmol) of o-, m-, or p-terphenyl were stirred under
*
Corresponding author. Tel.: +81 82 424 6291; fax: +81 82 424
0700.
E-mail address: snaka@hiroshima-u.ac.jp (S. Nakashima).
0277-5387/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.07.002

N. Masuhara et al. / Polyhedron 24 (2005) 1798–1802
1799
nitrogen atmosphere. The mixture was heated at 80 °C
2.2. X-ray crystal structural analyses
under nitrogen atmosphere for 16 h. The reaction mix-
ture was hydrolyzed slowly with 100 ml of degassed ice
water and then concentrated NH4OH was added to
become pH 9 and to precipitate Al(OH)3. After filtra-
tion, a yellow solid was obtained by adding 20 ml of
an aqueous HPF6. The precipitation was filtered, and
dried in vacuo. The dried crude product was treated
with 50 ml of CH2Cl2. The CH2Cl2 solution was filtered
and concentrated to 5 ml by evaporation. Then a large
amount of ether was added to give yellow microcrystals
(o-complex: 0.881 g, 20.4%. m-complex: 1.02 g, 23.6%.
p-complex: 0.915 g, 21.2%.). The insoluble product to
CH2Cl2 was treated with a large amount of acetone until
all yellow residue was dissolved and then filtered.
The acetone solution was evaporated to give yellow
microcrystals (o-complex: 3.15 g, 47.6%. m-complex:
2.35 g, 35.4%. p-complex: 2.11 g, 31.8%.). Anal. mono-
Single crystals for X-ray crystallography of mononu-
clear and dinuclear o-, m-, and p-terphenyl complexes
except for mononuclear m-isomer were obtained by
the following method. The mononuclear complexes were
dissolved in dichloromethane, while the dinuclear com-
plexes were in acetone and then they were put in the
hexane atmosphere at ꢁ15 °C. After several weeks single
crystals for X-ray structural analysis were obtained as
yellow column-shape crystals. They were cut so that
the longest side was less than 0.5 mm. All measurements
were made on Mac Science DIP 2030 imaging plate area
detector using graphite-monochromated Mo Ka radia-
tion. The cell parameters and intensities for the reflec-
tion were estimated by program package of Mac
DENZO [12]. The crystal structures were solved by
direct methods and expanded using Fourier techniques.
The non-hydrogen atoms were refined anisotropically,
while hydrogen atoms were refined isotropically. All
calculations were performed with the CrystalStructure
crystallographic software packages of Rigaku and
Molecular Structure Corporation [13]. Table 1 summa-
rizes crystallographic data and experimental details.
1
nuclear o-complex: H NMR(d/ppm, CD3CN) 5.14(5H),
6.15–6.44(4H), 6.81–8.16(10H). FAB Mass 351 ([CpFe-
1
(o-terphenyl)]+). Dinuclear o-complex: H NMR(d/ppm,
CD3CN) 4.95(10H), 6.04(4H), 6.21(6H), 7.78(2H),
2þ
8.00(2H). FAB Mass 617 ð½½ðCpFeÞ2ðo-terphenylÞꢀ
-
PF6ꢁꢀþÞ. Mononuclear m-complex: 1H NMR(d/ppm,
CD3CN) 4.88(5H), 6.54–6.83(4H), 7.26–7.91(10H). FAB
Mass 351 ([CpFe(m-terphenyl)]+). Dinuclear m-com-
2.3. 57Fe Mo¨ssbauer spectroscopic measurements
1
plex: H NMR(d/ppm, CD3CN) 4.99(10H), 6.38(2H),
6.47(4H), 6.78(4H), 7.78(1H), 8.04(2H), 8.16(2H). FAB
A 57Co(Rh) source moving in a constant-acceleration
mode was used for 57Fe Mo¨ssbauer spectroscopic mea-
surements. 57Fe Mo¨ssbauer spectra at 78 K were obtained
by using a Wissel spectrometer. The 57Fe Mo¨ssbauer
parameters were obtained by least-squares fitting to
Lorentzian peaks. The isomer shift values are referred
to metallic iron.
Mass 617 ð½½ðCpFeÞ2ðm-terphenylÞꢀ2þPF6ꢁꢀþ). Mononu-
1
clear p-complex: H NMR(d/ppm, CD3CN) 5.12(5H),
6.83–7.14(4H), 7.61–7.90(10H). FAB Mass 351 ([CpFe-
1
(p-terphenyl)]+). Dinuclear p-complex: H NMR(d/ppm,
CD3CN) 4.98(10H), 6.38(2H), 6.47(4H), 6.74(4H), 8.03
(4H). FAB Mass 617 ð½½ðCpFeÞ2ðp-terphenylÞꢀ2þPF6ꢁꢀþÞ.
Table 1
Details of crystal structure determinations
Mononuclear o-complex
23H19FePF6
Dinuclear o-complex
Dinuclear m-complex
Mononuclear p-complex
Dinuclear p-complex
Formula
C
C31H30Fe2P2F12
O
C31H30Fe2P2F12
O
C23H19FePF6
496.21
monoclinic
Pn(#7)
296
9.8310(3)
10.6700(4)
10.3780(3)
105.968(3)
1046.61(6)
2
C28H24Fe2P2F12
762.12
monoclinic
P21/n(#14)
296
10.5720(3)
12.9810(4)
10.8340(4)
100.9000(10)
1459.98(7)
2
Formula weight
Crystal system
Space group
T (K)
496.21
820.2
820.2
monoclinic
P21/n(#14)
296
10.7100(4)
10.7160(3)
19.0790(9)
102.5260(10)
2187.25(12)
4
monoclinic
C2/c(#15)
296
26.6550(5)
10.4660(2)
23.0270(6)
107.9020(10)
6112.9(2)
8
monoclinic
P21/c(#14)
296
12.7670(2)
16.9570(3)
15.1310(3)
92.9480(10)
3271.38(9)
4
˚
a (A)
˚
b (A)
˚
c (A)
b (°)
3
˚
V (A )
Z
Dcalc
l
1.542
8.39
0.119
0.177
1.782
11.54
0.054
0.121
1.665
10.78
0.078
0.095
1.574
8.56
0.036
0.042
1.733
11.98
0.100
0.116
Ra
b
Rw
P
P
a
R = iFoj ꢁ jFci/ jFoj.
P
P
b
2 1/2
Rw = ( w(jFoj ꢁ jFcj)2/ wjFoj )
.

1800
N. Masuhara et al. / Polyhedron 24 (2005) 1798–1802
3. Results and discussion
3.1. Syntheses and separations
We have synthesized the present arene complexes by
ligand exchange reaction between ferrocene and terphe-
nyl [4]. The reaction products include mononuclear and
dinuclear complexes. Total yield changes depending on
isomer, which is attributable to the difference in melting
point among o-(58–59 °C), m-(86–87 °C), and p-terphe-
nyl(213–216 °C). The mononuclear and dinuclear prod-
ucts were isolated by using the difference in solubility;
mononuclear complex is soluble to dichloromethane,
while dinuclear complex is not soluble to dichlorometh-
ane but soluble to acetone. The difference in solubility is
maybe caused by the difference in charge between
monocation and dication. The molar ratio of the mono-
nuclear to the dinuclear complex was dependent on the
isomer: i.e., 3:7 for o-derivative, while 2:3 for m- and
p-derivatives. The trinuclear complex is not obtained,
maybe because of large decrease in electron density on
the third benzene ring.
Fig. 2. ORTEP drawing of mononuclear p-terphenyl complex cation
with 50% probability drawing ellipsoids.
3.2. X-ray crystallography
Fig. 3. ORTEP drawing of dinuclear o-terphenyl complex cation with
50% probability drawing ellipsoids.
Figs. 1 and 2 show ORTEP drawings for mononu-
clear o- and p-terphenyl complex cations, respectively.
It can easily be seen that the FeCp+ is introduced to
the central benzene ring in both isomers. Figs. 3–5 show
ORTEP drawings for dinuclear o-, m-, and p-terphenyl
complex cations, respectively. It can also easily be seen
that the two FeCp+ are introduced to the terminal ben-
zene rings in all isomers. Figs. 1–5 also reveal that all
benzenes are not coplanar. The Cp ring has very aniso-
Fig. 4. ORTEP drawing of dinuclear m-terphenyl complex cation with
50% probability drawing ellipsoids.
tropic thermal ellipsoids especially in dinuclear m- and
p-terphenyl complex cations. This suggests the rotation
of Cp ring around 5-fold axis.
Crystallographic data are listed in Table 1, and
selected bond distances and angles are summarized in
Table 2. The average C–C distance in the central benzene
˚
ring is longer by 0.02–0.03 A than those of terminal
benzene rings in the mononuclear o- and p-terphenyl
complexes. The average C–C distances in the terminal
˚
benzene rings are longer by 0.01–0.02 A than that of cen-
Fig. 1. ORTEP drawing of mononuclear o-terphenyl complex cation
with 50% probability drawing ellipsoids.
tral benzene ring in the dinuclear o-, m-, and p-terphenyl

N. Masuhara et al. / Polyhedron 24 (2005) 1798–1802
1801
3.3. 57Fe Mo¨ssbauer spectroscopy
57Fe Mo¨ssbauer spectroscopy was applied to know the
electronic state of the present complexes. As the dinuclear
o-, m-terphenyl complexes include solvent molecule, the
measurement was done at 78 K by using single crystals.
Typical 57Fe Mo¨ssbauer spectrum is shown in Fig. 6. A
ferrocene-like single doublet is seen. All other complexes
also showed the similar single doublet. The 57Fe Mo¨ss-
bauer parameters (isomer shift (IS) and quadrupole
splitting (QS)) are summarized in Table 3. The
Mo¨ssbauer parameters are similar to each other and to
½fBenzeneFeCpgþꢀ½PF6ꢁꢀ. The decrease in QS value
Fig. 5. ORTEP drawing of dinuclear p-terphenyl complex cation with
50% probability drawing ellipsoids.
of the present arene complexes(1.65–1.75 mm sꢁ1
)
complexes. The change in C–C distance by coordination
is more drastic in mononuclear complexes than in dinu-
clear complexes.
The dihedral angles between the neighboring benzene
rings are also summarized in Table 2. There is not
significant difference in the angle between mononuclear
and dinuclear terphenyl complexes in each isomer. The
angles for mononuclear and dinuclear o-terphenyl
complexes are apparently larger than those of the corre-
sponding mononuclear and dinuclear m- and p-com-
plexes, suggesting ortho effect. The dihedral angles are
52.61° and 52.02° for mononuclear o-complex and
51.18° and 52.51° for dinuclear o-complex. This is inter-
esting because these values approach to the average
value of those of the metal-free o-terphenyl (62.1° and
42.5°) [14]. The difference of dihedral angles in metal-
free o-terphenyl was explained by the difference in inter-
molecular interactions in the lattice [14]. We thought
that the packing effect around the present o-terphenyl
complex cations and then the interaction of the cation
with its surroundings become more symmetric.
Fig. 6. 57Fe Mo¨ssbauer spectrum of dinuclear o-terphenyl complex at
78 K.
Table 3
57Fe Mo¨ssbauer parameters at 78 K
Sample
Mononuclear o-complex 0.55
Dinuclear o-complex 0.54
Mononuclear m-complex 0.53
Dinuclear m-complex 0.53
Mononuclear p-complex 0.54
Dinuclear p-complex 0.54
IS (mm sꢁ1
)
QS (mm sꢁ1
)
C (mm sꢁ1
)
1.71
1.75
1.68
1.66
1.65
1.69
0.33
0.27
0.25
0.29
0.28
0.24
Dinuclear o- and m-complexes contain acetone mole-
cule as solvent molecule, while dinuclear p-complex does
not. As a result, two irons are not equivalent for o- and
m-complexes, while equivalent for p-complex.
Table 2
Selected bond lengths and angles
Mononuclear o-complex Dinuclear o-complex Dinuclear m-complex Mononuclear p-complex Dinuclear p-complex
˚
Fe–C(Cp) (A)
2.039(4)
2.098(3)
5.526
2.036(2)
2.057(2)
2.088(1)
2.094(1)
5.335
2.026(3)
2.053(3)
2.086(2)
2.093(2)
5.487
2.039(4)
2.093(2)
5.359
2.042(3)
2.042(3)
2.087(2)
2.087(2)
5.319
˚
Fe–C(arene) (A)
˚
Fe–F(PF6) (A)
5.429
5.582
5.319
Dihedral angle (°)
52.02
52.61
1.382(5)
51.18
52.51
32.52
30.92
35.38
32.94
1.390(4)
38.79
38.79
˚
C–C(Cp) (A)
1.405(3)
1.379(4)
1.410(2)
1.392(2)
1.410(2)
1.403(5)
1.355(7)
1.406(3)
1.394(3)
1.402(3)
1.38(1)
1.38(1)
1.405(3)
1.398(3)
1.405(3)
˚
C–C(terminal) (A)
1.378(4)
1.407(4)
1.386(4)
1.387(3)
1.416(3)
1.385(3)
˚
C–C(central) (A)
˚
C–C(terminal) (A)

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N. Masuhara et al. / Polyhedron 24 (2005) 1798–1802
compared to ferrocene (2.4 mm sꢁ1) is explained by the
interaction of the e2g d orbitals with the ring orbitals [8].
Although the X-ray crystal structural analyses showed
that the two iron sites are slightly different in the dinuclear
o- and m-terphenyl complexes, the slight difference in the
site does not appear in the Mo¨ssbauer spectra. And the
difference between the mononuclear and the dinuclear
complexes does not significantly appear in the 57Fe Mo¨ss-
bauer spectra. Close inspection, however, reveals that o-
terphenyl complexes show slightly larger QS value.
(fax: +44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk
or www: http//www.ccdc.cam.ac.uk). Supplementary
data associated with this article can be found, in the
online version, at doi:10.1016/j.poly.2005.07.002.
References
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4. Conclusion
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We succeeded to obtain mononuclear and dinuclear
arene complexes of o-, m-, and p-terphenyl and to separate
them by using the difference in solubility. We confirmed
that FeCp+ was introduced to the central benzene in the
mononuclear complexes, while they were introduced to
the terminal benzenes in the dinuclear complexes.
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Appendix A. Supplementary data
Crystallographic data for the structural analysis have
been deposited at the Cambridge Crystallographic Data
Centre, CCDC 249481–249485. Copies of this informa-
tion may be obtained free of charge from the Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK