Synthesis of cationic (arene)IronCp complexes via arene exchange

Article abstract of DOI:10.1016/j.ica.2003.11.022

Rates and regioselectivity of arene exchange reactions in cationic fused arene Fe(II)Cp complexes were investigated. Thermal exchange of pyrene, naphthalenes, and cyclooctatetraene occurs in the temperature range of 90-140°C. The most labile complex in the series studied is [(η⁶-(1-4,4a,8a)-1,4-dimethoxynaphthalene)FeCp][PF₆] having the FeCp coordinated to the substituted ring. Pyrene and other naphthalene complexes come next, followed by the cyclooctatetraene complex. Phenanthrene, veratrol, and dihydronaphthalene do not undergo exchange at temperatures up to 130°C. With Me- and OMe-substituted naphthalenes, exchange is reversible and favors the product having the metal coordinated to the non-substituted ring. The X-ray crystal structures of the two regioisomeric 1,4-dimethoxynaphthalene complexes were determined. Arene exchange in fused arene complexes is shown to be a useful synthetic method and provides new arene complexes cleanly and efficiently. The method is particularly attractive for arenes that contain functionalities that are not compatible with the Lewis acid-mediated routes. The starting materials are readily accessible via the TiCl₄-assisted Cp exchange in ferrocene.

Full text of DOI:10.1016/j.ica.2003.11.022

Inorganica Chimica Acta 357 (2004) 1909–1919
www.elsevier.com/locate/ica
Synthesis of cationic (arene)IronCp complexes via arene exchange q
*
ꢀ
E. Peter Kundig , Patrick Jeger, Gerald Bernardinelli
€
Department of Organic Chemistry, University of Geneva, 30 Quai Ernest Ansermet, Geneva 4 CH-1211, Switzerland
Received 11 November 2003; accepted 22 November 2003
This paper is dedicated to Prof. Helmut Werner in celebration of his 70th birthday
Abstract
Rates and regioselectivity of arene exchange reactions in cationic fused arene Fe(II)Cp complexes were investigated. Thermal
exchange of pyrene, naphthalenes, and cyclooctatetraene occurs in the temperature range of 90–140 °C. The most labile complex in
the series studied is [(g6-(1-4,4a,8a)-1,4-dimethoxynaphthalene)FeCp][PF6] having the FeCp coordinated to the substituted ring.
Pyrene and other naphthalene complexes come next, followed by the cyclooctatetraene complex. Phenanthrene, veratrol, and di-
hydronaphthalene do not undergo exchange at temperatures up to 130 °C. With Me- and OMe-substituted naphthalenes, exchange
is reversible and favors the product having the metal coordinated to the non-substituted ring. The X-ray crystal structures of the two
regioisomeric 1,4-dimethoxynaphthalene complexes were determined. Arene exchange in fused arene complexes is shown to be a
useful synthetic method and provides new arene complexes cleanly and efficiently. The method is particularly attractive for arenes
that contain functionalities that are not compatible with the Lewis acid-mediated routes. The starting materials are readily accessible
via the TiCl4-assisted Cp exchange in ferrocene.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Arene complexes; Arene exchange; Iron Cp complexes; Naphthalene
1. Introduction
CpFeþ complex and dehalogenation occurs with halo-
genated arenes when Al powder is present [3]. Partial
hydrogenation of fused arenes like anthracene, pyrene,
and naphthalene is a further problem [4]. These side
reactions can be avoided in some cases by carrying out
the preparation in neat arene or in a hydrocarbon
solvent at 70–100 °C. Addition of a Bronsted acid, e.g.,
in the form of 1 equiv. of water, can strongly increase
the yield in methyl arenes [5]. Despite these optimiza-
tions, yields of reactions with substituted arenes are
often below 50%. The use of microwave heating has
given good results and reaction times are much reduced
[6]. Acidic ionic liquids as reaction medium have also
been used successfully [7]. The patent literature pre-
sents another solution: addition of TiCl4 to the reac-
tion in the proportion ferrocene to TiCl4 ¼ ca. 2:1.
The titanium reagent traps the cyclopentadienyl ligands
to form titanocene dichloride and this can mark-
edly increase the yield of the cationic arene complex
[8,9].
Cationic arene cyclopentadienyl iron complexes were
first isolated from the reaction of CpFe(CO)2Cl with
arenes in the presence of AlCl3 [1]. Subsequently, Nes-
meyanov et al. [2] developed the ferrocene route
(Scheme 1) and for most arenes this is more convenient
and efficient and has become the standard synthesis for
this class of compounds.
It has drawbacks in that it requires a stoichiometric
amount of a strong Lewis acid and the method is not
suited for alkyl arenes that are susceptible to undergo
retro Friedel–Crafts rearrangements. Arenes with elec-
tron acceptor groups, e.g., acetophenone, benzonitrile,
acetanilide, indole, etc., fail to form the corresponding
q Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.ica.2003.11.022.
* Corresponding author. Tel.: +4122-3796093; fax: +4122-3793215.
E-mail address: Peter.Kundig@chiorg.unige.ch (E. Peter Ku€ndig).
0020-1693/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2003.11.022

1910
E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
1. AlCl3, Al, arene
+
readily than benzene derivatives. (Naphthalene)Cr(CO)3
is a convenient ÔCr(CO)3Õ transfer agent and thermal
arene exchange can take place at temperatures as low as
25 °C [15]. The lability results from both, a weaker arene
metal bond, and a higher propensity of the naphthalene
ligand to undergo haptotropic slippage to provide co-
ordination sites for the incoming arene ligand [15,16].
More recently, (naphthalene)Mn(CO)3][PF6] has been
used analogously [17]. In this paper, we present the
results of our studies of the synthesis, under neutral
conditions, of (arene)FeCpþ complexes via arene
exchange, on the relative aptitude to undergo exchange
and on regioselectivity in complexation of substituted
naphthalenes.
PF -
6
70 - 190 oC, 1-16h
2. aq. NH4PF6
R
Fe
Fe
ratio ferrocene/AlCl3 /Al = 1:2:1
Scheme 1.
The metal arene bond in (arene)FeCpþ complexes is
photolabile [10] and this is the basis of the use of these
complexes as photoinitiators for cationic epoxide poly-
merization reactions [11]. Under irradiation by a
medium pressure Hg-arc or by Ôbright sunlightÕ, (p-xy-
lene)FeCpþ undergoes arene exchange with hexameth-
ylbenzene, paracyclophane or thiophene under mild
conditions [10,12].
An efficient route that uses neither Lewis acids nor
light again stems from the patent-literature and involves
thermal arene exchange in complexes of condensed
aromatics (Scheme 2) [13]. This route has not been
further studied and indeed, recent review articles on the
topic of arene Fe chemistry do not mention this ap-
proach [14].
Our interest in this method was prompted by the
finding that the classic AlCl3-mediated reaction fails
when applied to the synthesis of [(5,8-dimethoxynaph-
thalene)FeCp][PF6] (1), a compound that we wished
to include in a study of the regioselectivity of nucleo-
philic addition to substituted cationic (arene)FeCp
complexes[13c].
2. Results and discussion
2.1. Preparation of (g6-arene)(g5-cyclopentadienyl)-iro-
n(II) hexafluorophosphate complexes from ferrocene
The FeCpþ complexes 1–6 were synthesized in 65–
83% yields from ferrocene by using the TiCl4-assisted
procedure described by Doggweiler and Desobry [8,9].
The methylnaphthalene complexes 3 and 4 are formed
as an inseparable 1:1 mixture of the two regioisomers.
Photolytic arene substitution of p-xylene in [(p-xy-
lene)FeCpþ by cyclooctatetraene as described by Heck
and Massa [18] afforded complex 7 in 83% yield.
Formula 1:
In (arene)Cr(CO)3 chemistry, complexes of condensed
aromatic rings undergo arene exchange much more
+ PF6
-
R
-
+ PF6
PF6-
+
+ PF6
-
+
-
PF6
PF -
+
5 equiv.
6
+
R
+
CpFe
+
CpFe
CpFe
+
Fe
Fe
CpFe
2
1
3
4
_
+
-
2, 8-14
OMe
+
1
PF6
PF6-
PF6-
+
+
OMe
OMe
OMe
+
+
+
CpFe
CpFe
CpFe
+
5
6
7
+
+
CpFe
CpFe
OMe
CpFe OMe
(120 oC, 3h)
8 (94%)
9
(130 oC, 2.5h) 10
2.2. Arene exchange reactions in (g6-arene)(g5-cyclopen-
tadienyl)-iron(II) hexafluorophosphate complexes
19
:
1 (95%)
OMe
+
OMe
OMe
+
OMe
A first set of exchange experiments was carried out
with [(pyrene)FeCp][PF6] (1) (Scheme 3). Best results
were obtained when the reactions were carried out in
neat incoming arene. Higher temperatures are required
for the transfer of the FeCpþ fragment from one arene
to another, than for the analogous reactions involving
+
+
CpFe
+
CpFe
11 (130 oC, 2 h) 12
CpFe
CpFe
13 (130 oC, 2 h) 14
10
: 1
7
:
1
Scheme 2. Arene exchange reactions in [(pyrene)FeCp][PF6] (1).

E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
1911
R'
The data show that in all cases but one (entry 7), a
mixture of starting complex and product is obtained.
Longer reaction times do not change these ratios,
suggesting that equilibria are reached. In agreement
with this state of affairs, increasing the ratio of in-
coming naphthalene to starting complex drives the re-
action to a product ratio from which the major product
can be isolated in good yield. An example is shown in
entry 2 where the 20-fold excess of dimethoxynaph-
thalene results in a 19:1 mixture of the dimethoxy-
naphthalene versus the methylnaphthalene complexes.
Equilibration is also manifest in entries 3 and 4 where
equilibria are approached from both sides. Equilibria
are also shifted by the removal of one reaction partner:
naphthalene readily sublimes at 130 °C and as shown in
entry 7, the dimethoxynaphthalene complexes are the
sole products.
PF -
+
+
-
PF6
6
R
R'
R
Fe
Fe
Scheme 3. Arene exchange reactions in naphthalene FeCp complexes.
complexes of Cr(CO)3 or Mn(CO)þ3 . In a typical ex-
periment, [(pyrene)FeCp][PF6] (1) and a 5-fold excess
of 1,2-dimethoxybenzene (veratrol) were stirred at 130
°C under a nitrogen atmosphere. The color of the re-
action mixture veered from orange to purple. The re-
action was conveniently followed by analyzing samples
by 1H NMR spectroscopy: integration of the Cp–H
singlet of 1 at 4.34 ppm versus that of the Cp–H
singlet at 5.02 of the veratrol complex 8. After 2.5 h,
the exchange was complete and work-up afforded a
94% yield of [(veratrol)FeCp][PF6] (8) [19]. Separation
of the cationic complexes from the neutral arene is
straightforward, making this synthetic route highly
attractive. We briefly investigated reactions in solution
in order to avoid the use of a large excess of arene.
The reaction of 1.5 equiv. of 1,4-dimethoxynaphtha-
lene with complex 1 in 1,1,2-trichloroethane at 130 °C/
2.5 h gave a 67% yield of complex 9. This shows that
exchange in dilute solution is feasible, albeit at the
expense of yield. Complexes 9–17 have not been pre-
viously reported.
We briefly also checked complexes 5–7 containing
the ligands phenanthrene dihydroanthracene and cy-
clooctatetraene for their ability to undergo arene ex-
change. At 120 °C, the arene bonds in 5 and 6 are inert
and no exchange was observed in the presence of a 5-
fold excess of veratrol. The cyclooctatetraene complex 7
readily underwent exchange with veratrol (10 equiv.
120 °C, 2 h) to give complex 8 as sole product. With
1,4-dimethoxynaphthalene (5 equiv.), exchange was
1
incomplete at 130 °C and H NMR analysis indicating
the presence of a 60:40 mixture of complexes 7 to 9, 10
(20:1).
The MeO-substituted naphthalenes afforded mixtures
of regioisomers in which the isomer containing the metal
in the non-substituted ring largely dominated. Com-
plexes 9–11 and 13 were obtained pure by fractional
crystallization. We note that thermolysis of Cr(CO)6 in
the presence of 1-methoxynaphthalene or 1,4-dimeth-
oxynaphthalene affords exclusively the regioisomers
containing the metal in the non-substituted ring [20].
This also applies to Cp exchange in ferrocene by 1-flu-
oro and 1-chloro-naphthalene [21].
2.2.1. Ring selectivity
Complexation of naphthalenes with a different
substitution pattern of the two rings results in the
formation of two regioisomers. With 1-methylnaph-
thalene, the proportion of the regioisomeric complexes
3 and 4 is roughly 1:1. With methoxy-substituted
naphthalenes, a major and a minor regioisomer is
formed. In all three cases studied (1-methoxynaph-
thalene, 2-methoxynaphthalene, and 1,4-methoxy-
naphthalene), the major isomer is the one having the
FeCpþ fragment in the non-substituted ring. This
We next investigated naphthalene exchange in the
complexes 2–4, 11, and 13.
Entry
Starting
complex
Incoming
naphthalene
Equiv.
Temp/time
(°C), h
130, 2
110, 8
130, 2.5
130, 3
130, 2.5
130, 3
130, 2.5
Product
complexes (ratio)
Ratioa
Yield
(%)b
1
2
3
4
5
6
7
3,4 (1:1)
3,4 (1:1)
3,4 (1:1)
13
3,4 (1:1)
11
1,4-C10H6(OMe)2
1,4-C10H6(OMe)2
1-C10H7(Ome)
1-C10H7(Me)
2-C10H7(OMe)
1-C10H7(Me)
1,4-C10H6(OMe)2
5
20
5
5
5
9,10 (15:1)
9,10 (20:1)
13,4 (7:1)
3,4 (1:1)
11,12 (11:1)
3,4 (1:1)
9,10 (20:1)
17:83
5:95
80
76
64
72
65%
89%
89
17:83
14:86
17:83
8:92c
<1:99c
5
5
2
a Ratio of starting complex to product at the end of the reaction period as determined by 1H NMR of the crude product.
b Isolated yield of product isomer mixture.
c Naphthalene and its 2-MeO derivative sublime from the reaction mixture.

1912
E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
OMe
trend mirrors that of the analogous Cr(CO)3 com-
plexes [20]. At 110–130 °C, reversibility of complexa-
tion has been firmly established and the proportions in
which the regioisomers form must therefore represent
the thermodynamic stability of the complexes. In
(naphthalene)Cr(CO)3 complexes it has been estab-
lished that in addition to intermolecular exchange, ring
exchange via an intramolecular haptotropic rear-
rangement takes place and, in the absence of coordi-
nating solvents, is faster than the arene exchange [22].
While it is probable that the isoelectronic and isolobal
FeCpþ complexes behave likewise, this remains to be
established. Arene exchange in the Cr(CO)3 complexes
is strongly accelerated by the addition of a donor
solvent (e.g., THF). In the Fe arene exchange reactions
this is not the case and additives have a negative effect
on product yields.
+
-
PF6
OMe
OMe
OMe
[(Arene)FeCp][PF6] (1-4, 9,10)
or [COTFeCp][PF6] (7)
5 equiv., 120 o
C
Fe
Scheme 4. Thermal arene exchange for veratrol in [(arene)FeCp][PF6]
complexes at 120 °C.
R
+
-
PF6
+
-
PF6
R
excess
Fe
Fe
2
8, 15-18
OMe
2.2.2. Rate of arene exchange
OMe
OMe
Removing samples during the arene exchange reac-
tions showed the rate of exchange for isomeric com-
plexes 3 and 4 as well as 9 and 10 to be different and to
result in an enrichment of one isomer. Scheme 4 shows
the results of a kinetic study of arene exchange for ve-
ratrol at 120 °C. The data are arranged in the order of
increasing rate of arene exchange. First order kinetics
were observed throughout.
OMe
+
+
+
CpFe
CpFe
CpFe
(120 oC, 1h)
16 (98%)
(120 oC, 1h)
8 (82%)
(120oC, 3h)
15 (87%)
OMe
I
MeO
CpFe
OMe
+
+
CpFe
(140oC, 2h)
18 (74%)
(120oC, 1h)
17 (95%)
Scheme 5. Arene exchange reactions in [(naphthalene)FeCp][PF6].
a
Entry Starting
complex
k (10ꢀ4 sꢀ1
)
t1=2
(min)
Krel
Formula 2:
1
2
3
4
5
6
7
3
4
1
7
2
2.8 ꢁ 0.1b
4.2 ꢁ 0.2b
5.1 ꢁ 0.3
5.7 ꢁ 0.3
6.1 ꢁ 0.3
6.1 ꢁ 0.3
ꢂ120
42
27
22
20
19
19
ꢂ1c
1.0
1.5
1.9
2.1
2.2
2.2
ꢂ43c
9
10
OMe
OMe
OMe
OMe
OMe
OMe
>>
a Calculated by the least-squares method. Every linear regression is
based on a minimum of six data points. Correlations are between 0.995
and 0.999.
>
b Starting complex was a 1:1 mixture of 3 and 4. Relative rate of
exchange determined from enrichment in isomer 3 during the reaction.
c Estimation. The rate is too rapid for accurate measurement via the
method used.
(no exchange at 130˚C)
Scheme 5 lists further examples of complexes made
via this route. The results show that the incoming arene
does play a role in the naphthalene exchange reactions.
Exchange with the methoxy substituted arenes was
complete within 1 h at 120 °C (5 equiv. of arene),
whereas benzocyclobutene (10 equiv. of arene) required
3 h to go to completion and the reaction with iodo-
benzene was sluggish at 120 °C but reacted readily at
140 °C (10 equiv. of arene). We noted that the same
The fastest arene exchange occurred in 10. Additional
experiments established that 10 exchanged its arene for
veratrol already at 90 °C with a half life of ca. 20 min.
Taken together, the data reported above give the fol-
lowing sequence for the aptitude to arene exchange
(Formula 2.2 circles indicate the coordination to the
CpFeþ fragment).

E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
1913
order was observed in exchange reactions in (py-
rene)Cr(CO)3 complexes [23].
crystallized readily upon diffusion of a toluene layer
into a CH2Cl2 solution of the mixture. We were for-
tunate that this procedure, when applied to mixtures of
complexes isolated from the mother liquor eventually
also provided crystals of the minor regioisomer. Figs. 1
and 2 show perspective views of 9 and 10, respectively.
Table 1 shows selected geometrical and ring slippage
parameters [24] for the two sandwich complexes. The
two ring systems in 9 and 10 are practically parallel.
The C(arene)–Fe distances in complexes 9 and 10 are in
A number of arenes could not be synthesized by this
direct method. They include acetophenone, acetophe-
none dimethylacetal, benzyl alcohol, benzyl chloride,
and 1-ethoxybenzocyclobutene. These reactions resulted
in decomposition of the complex.
2.3. Structural studies on complexes 9 and 10
ꢁ
The difference in the rate at which the two dimeth-
oxynaphthalene complexes 9 and 10 undergo arene
exchange and the fact that the literature contains no X-
ray crystal structure data of a (naphthalene)FeCpþ
complex, prompted us to seek to obtain these data for
the two regioisomeric complexes. The major isomer 9
the range expected (1.52–1.59 A) for cationic arene
FeCp complexes. This also holds for the C(Cp)–Fe
6
ꢁ
distances (1.62–1.69 A). Within the g -ring ligand of 9,
the C–C bond distances vary in a non-alternant fashion
ꢁ
between 1.370(7) and 1.446(7) A; the shorter observed
distances are of the C(1)–Cð10Þ and C(1)–C(2) bonds
and the longer are the C(2)–C(3) and C(3)–Cð30Þ bonds.
This also holds true for 10 albeit that this structure
does not have a mirror plane as 9. Again, the shorter
C–C distances are C(1)–C(2), C(2)–C(3), and C(3)–
C(4), and the longer ones are C(4)–C(5), C(5)–C(10),
and C(1)–C(10). The C(arene)–Fe distances to the ring
junction carbons are longer than those of the other
C(arene)–Fe. The projection of the metal on the arene
plane does not coincide with the center of gravity but is
ꢁ
displaced by 0.037 A (for 9) and by 0.048 (for 10) in the
direction of the C(1)–Cð10Þ bond in 9 and the C(2)–C(3)
bond in 10 (see values D in Table 1). This shift is a
common feature in complexes of condensed arene li-
gands with group 6 metals. The excentricity and the
variation of C–C bond lengths in the coordinated ring
are indicative of a movement of the metal in the di-
rection of a g4 coordination [25]. Although these are
ground state properties, it is interesting to note that
the Fe–arene distance and the size of the ring slippage
D are larger for the more labile complex 10 than
for 9.
Fig. 1. Perspective view of complex 9 with the atom numbering. El-
lipsoids are represented with 30% probability.
3. Conclusions
As reported in the patent literature, the substitution
of a Cp ligand in ferrocene by an arene is assisted by the
addition of a stoichiometric amount of TiCl4. The lib-
erated Cp ligand is captured by the Ti reagent to form
titanocenedichloride. Reactions are cleaner than in the
absence of TiCl4, reaction times are reduced signifi-
cantly, and yields are often higher.
(g6-Arene)(g5-cyclopentadienyl)-iron(II) complexes
are also readily accessible via arene exchange in com-
plexes containing fused aromatic ligands (pyrene,
naphthalene). Ligand exchange occurs in the tempera-
ture range 90–140 °C. The rate depends on the arene in
the precursor complex and on the incoming arene. The
method is particularly attractive for arenes that contain
functionalities that are not compatible with the Lewis
Fig. 2. Perspective view of complex 10 with the atom numbering. El-
lipsoids are represented with 30% probability.

1914
E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
Table 1
Selected geometrical and ring slippage parameters [24] for 9 and 10a
Compound
9
10
C(1)–C(2)
C(2)–C(3)
C(3)–Cð30Þ
C(1)–Cð10Þ
1.385(7)
1.423(6)
1.446(7)
1.370(7)
C(1)–C(2)
C(2)–C(3)
C(3)–C(4)
C(4)–C(5)
C(5)–C(10)
C(10)–C(1)
1.400(6)
1.406(8)
1.398(8)
1.431(6)
1.428(7)
1.441(8)
Fep–C(1)b
Fep–C(2)
Fep–C(3)
1.391
1.394
1.429
Fep–C(1)
Fep–C(2)
Fep–C(3)
Fep–C(4)
Fep–C(5)
Fep–C(10)
1.426
1.400
1.410
1.417
1.423
1.427
ꢁ
Fe–arene (A)
ꢁ
Fe–Cp (A)
1.548(1)
1.664(1)
0.8(2)
0.037
1.37
1.567(1)
1.658(1)
1.4(2)
0.048
1.74
Angle arene/cp (°)
c
ꢁ
D (A)
wd ð°Þ
reð°Þ
0.0
6.2
a See Figs. 1 and 2 for the atom numbering; symmetry operation for the primed atoms: x; y; 3=2 ꢀ z.
b Fep corresponds to the projection of the iron atom on the mean plane of the arene.
c D is the length of the shift vector S.
d w is the angle (centroid of the arene)–Fe–Fep.
e r is the angle mp–(centroid)–Fep, where mp are the midpoints C(1)–Cð10Þ and C(2)–C(3) for 9 and 10, respectively.
acid-mediated routes. The best starting materials are the
readily accessible CpFeþ complexes of pyrene, naph-
thalene, and methylnaphthalene.
4.1. Preparation of (g6-arene)(g5-cyclopentadienyl)-
iron(II) hexafluorophosphate complexes from ferrocene
4.1.1. (g6-pyrene)(g5-Cyclopentadienyl)-iron(II) hexa-
fluorophosphate (1) [4c,27]
4. Experimental part
A round bottom flask (500 ml), equipped with a re-
flux condenser and mechanical stirring, was charged
with pyrene (16.00 g, 79 mmol), ferrocene (7.30 g, 39
mmol), AlCl3 (6.70 g, 50 mmol), and Al powder (0.22 g,
8 mmol). Air was removed by applying a vacuum. The
reaction flask was placed under N2 and dry, degassed
methylcyclohexane (100 ml) was added. The stirred re-
action mixture was brought to 40 °C via an external oil
bath and TiCl4 (2.8 ml, 25 mmol) was added dropwise
via syringe over a period of 15 min. The temperature
was then raised to 100 °C (reflux) and the reaction
stirred for 1 h. After cooling to r.t., the black reaction
mixture was poured onto an ice (150 g)/conc. HCl (18
ml) mixture. The mixture was heated to 50 °C for 30
min, cooled to r.t. and filtered. 1 The aqueous phase was
separated and treated with an aq. solution of KPF6
(8.00 g, 43 mmol in 100 ml of N2 saturated H2O). After
30 min stirring at 0 °C, the yellow precipitate formed
was filtered off and dried under vacuum. The crude
product was taken up in acetone (100 ml), dried over
MgSO4, and filtered. Addition of diethyl ether precipi-
tated 1 (11.90 g, 25,4 mmol, 65%) as yellow microcrys-
Reactions were carried out under an atmosphere of
purified nitrogen using an inert gas/vacuum double
manifold and standard Schlenk techniques. All NMR
spectra (1H: 200 or 400 MHz; 13C: 50.3 or 100.5 MHz)
were recorded at RT on a Varian XL-200 MHz or
Bruker 400 MHz spectrometer as indicated. Chemical
shifts ðdÞ are reported relative to TMS. Coupling
constants J are given in hertz. Mass spectra were ob-
tained on Varian CH4 or SM1 spectrometers, relative
intensities are given in parentheses. High-resolution
mass spectra were measured on a VG analytical 7070E
instrument (data system 11250, resolution 7000). IR
spectra were recorded in NaCl cells on a Perkin–Elmer
1650 FT-IR spectrometer. Melting points were deter-
€
mined on a Buchi 510 apparatus and are not corrected.
Photolysis was carried out using pyrex glassware and a
Philips HPK 125 W high pressure Hg-arc. THF and
diethylether were dried and distilled from sodium/
benzophenone ketyl under N2 before use. Dichlorom-
ethane and methylcyclohexane were freshly distilled
from CaH2 under N2. All chemicals were purchased
from Aldrich or Fluka. Complexes 3 and 4 (1:1 mix-
ture) [26] were a gift from V. Desobry, Ciba-Geigy,
1993.
1
The red organic phase contains unreacted ferrocene and titanocene
dichloride. Although not done here, the latter can be precipitated by
addition of H2O2 [8,9].

E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
1915
talline solid. IR(CH2Cl2): 3070w, 1575w, 1414w, 1185w,
846s, 558m cmꢀ1 1H NMR (DMSO-d6, 200 MHz):
8.10–8.45 (m, 7H), 7.23 (d, J ¼ 6:4, 2H)), 6.59 (t,
J ¼ 6:4, 1H), 4.34 (s, 5H). 13C NMR (DMSO-d6, 50
MHz): 133.0, 131.4, 130.0, 128.8, 127.3, 125.5, 93.0,
88.4, 85.3, 83.0, 76.0.
was separated, filtered, and treated with an aq. solution
of KPF6 (4.0 g in 100 ml of N2 sat. H2O). After cooling
to 0 °C, the orange precipitate was filtered off and dried
under vacuum (7.51 g, 16.9 mmol, 79%). IR(CH2Cl2):
3069w, 1606w, 1480m, 1421w, 1435m, 1421m, 1330w,
.
1010w, 852s, 558s cmꢀ1 1H NMR (DMSO-d6, 200
.
MHz): 8.80–8.90 (m, 1H), 8.10 (d, J ¼ 9, 1H), 8.05–8.15
(m, 1H), 7.95–8.05 (m, 1H), 7.85–7.95 (m, 2H), 7.80 (d,
J ¼ 9, 1H), 7.15–7.25 (m, 1H), 6.50–6.60 (m, 2H), 4.61 (s,
5H). 13C NMR (DMSO-d6, 50 MHz): 133.1, 132.5,
130.3, 129.7, 129.3, 128.9, 126.4, 124.6, 93.9, 93.3, 86.7,
86.3, 85.7, 80.5, 76.2.
4.1.2. (g6-Naphthalene)(g5-cyclopentadienyl)-iron(II)
hexafluorophosphate (2) [2c,8,9,28a]
A round bottom flask (500 ml), equipped with a
reflux condenser and mechanical stirring, was charged
with naphthalene (51.3 g, 0.4 mol), ferrocene (18.6 g,
0.1 mol), AlCl3 (14.7 g, 0.11 mol), and Al powder (1.4
g, 52 mmol). Air was removed by applying a vacuum.
The reaction flask was placed under N2 and dry, de-
gassed methylcyclohexane (180 ml) was added. The
stirred reaction mixture was brought to 30 °C via an
external oil bath and TiCl4 (5.5 ml, 50 mmol) was ad-
ded dropwise via syringe over a period of 15 min. The
temperature was then raised to 90 °C and the reaction
stirred for 3 h. After cooling to 0 °C, the black reaction
mixture was treated slowly with an aq. solution of HCl
(37 ml conc. HCl in N2 sat. water (170 ml)), followed
by a solution of H2O2 (2.9 ml of a 30% aq. solution).
The dark red mixture was stirred at 50 °C for 30 min,
and then the aqueous phase was separated, filtered, and
treated with an aq. solution of KPF6 (18.4 g in 170 ml
of N2 sat. H2O). After cooling to 0 °C, the red pre-
cipitate was filtered off and dried under vacuum (31.75
g, 81%). The crude product was recrystallized from
acetone (150 ml) to give 2 as red crystals (26.23 g, 67
mmol, 67%). Melting point: 165 °C, IR(CH2Cl2):
3070m, 1625w, 1531w 1480m, 1421m, 1409m, 1374w,
4.1.4. (g6-(9,10)-Dihydroanthracene)((g5-cyclopenta-
dienyl)-iron(II) hexafluorophosphate (6) [4a,4d,6]
Starting with 9,10-dihydroanthracene (10.0 g, 55.5
mmol) and ferrocene (4.00 g, 21.5 mmol), the synthesis
followed the preparation described for 5. The reaction
afforded yellow 6 (7.94 g, 17.8 mmol, 83%). No recrys-
tallization was necessary. IR(CH2Cl2): 3071w, 1459m,
1
1422m, 1010w, 846s, 558s, cmꢀ1. H NMR (DMSO-d6,
200 MHz): 7.30–7.50 (m, 4H), 6.40–6.50 (m, 2H), 6.25–
6.35 (m, 2H), 3.99 (s, 4H), 4.54 (s, 5H). 13C NMR
(DMSO-d6, 50 MHz): 134.3, 127.4, 126.9, 102.9, 86.5,
85.8, 75.9.
4.2. Preparation of (g6-arene)(g5-cyclopentadienyl)-iro-
n(II) hexafluorophosphate complexes by arene exchange
in the pyrene complex 1
4.2.1. General procedure
In a Schlenk tube under N2, [(pyrene)FeCp][PF6] (1)
(1 mol equiv.) was added to the arene (5–10 mol equiv.)
and the solution was stirred magnetically for the time
and at the temperature indicated. At the end of the re-
action, the mixture was cooled to r.t. followed by the
addition of CH2Cl2 to double the initial volume and n-
hexanes to bring the initial volume to 10ꢃ. The sus-
pension was filtered over Celite and the raw product on
the Celite was washed with three portions of toluene.
The recipient was changed and the Celite was eluted
with CH2Cl2. Removal of the solvent afforded the
product. After determination of the isomeric ratio by
1
1106w, 1010w, 850s, 558s cmꢀ1. H NMR (DMSO-d6,
200 MHz): 8.00–8.10 (m, 2H), 7.85–7.95 (m, 2H), 7.30–
7.40 (m, 2H), 6.40–6.50 (m, 2H), 4.64 (s, 5H). 13C
NMR (DMSO-d6, 50 MHz): 131.8, 130.9, 95.4, 86.6,
84.9, 76.1.
4.1.3. (g6-Phenanthrene)(g5-cyclopentadienyl)-iron(II)
hexafluorophosphate (5) [27b,29]
A round bottom flask (500 ml), equipped with a reflux
condenser and mechanical stirring, was charged with
phenanthrene (10.2 g, 57 mmol), ferrocene (4.0 g, 22
mmol), AlCl3 (2.97 g, 22 mmol), and Al powder (151 mg,
5.6 mmol). Air was removed by applying a vacuum. The
reaction flask was placed under N2 and dry, degassed
methylcyclohexane (50 ml) was added. The stirred reac-
tion mixture was brought to 50 °C via an external oil
bath and TiCl4 (1.20 ml, 11 mmol) was added dropwise
via syringe over a period of 15 min. The temperature was
then raised to 100 °C and the reaction stirred for 1 h.
After cooling to 0 °C, the black reaction mixture was
treated slowly with an aq. solution of HCl (8 ml conc.
HCl in N2 sat. water (80 ml)). The dark red mixture was
stirred at 50 °C for 30 min, and then the aqueous phase
1
integration of the Cp signal in the H NMR spectrum,
the crude material was recrystallized from CH2Cl2 so-
lution by slow addition of toluene.
4.2.2. [(g6-Veratrol)FeCpþ] [PFꢀ6 ] (8)
Following the procedure detailed in 4.2.1, complex 1
(740 mg, 1.58 mmol) was added to veratrol (1 ml, 7.8
mmol) and stirred at 120 °C for 3 h. Work up afforded
yellow, microcrystalline 8 (602 mg, 1.48 mmol, 94%).
Melting point: 177 °C. IR(CH2Cl2), cmꢀ1: 1535w,
1522w, 1491m, 1461w, 1437w, 1418w, 1279m, 1228w,
1
1016w, 846s, 558m. H NMR (DMSO-d6, 200 MHz):

1916
E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
6.38 (AA0BB0, 2H), 5.96 (AA0BB0, 2H), 5.02 (s, 5H), 3.98
(s, 6H). 13C NMR (DMSO-d6, 50 MHz): 124.2, 80.6,
75.7, 71.3, 56.9. ES-MS, m=z: 259 (Mþ, 100); MS, m=z:
166(55), 138(87), 107(100), 95(90), 77(68), 65(63),
52(71). Anal. Calc. for C13H15O2FePF6 (404.1): C,
38.64; H, 3.74. Found: C, 38.74; H, 3.72%.
regioisomers 11 and 12 in a ratio of 7:1. Crystallization
from CH2Cl2/toluene (5:1) afforded 11 (211 mg, 0.50
mmol, 80%).
[(g6-5-Methoxynaphthalene)FeCpþ][PFꢀ6 ](11). Red
crystals. Melting point: 153 °C. IR(CH2Cl2): 3071w,
2941w, 1625m, 1547m, 1408m, 1278m, 846s, 558m cmꢀ1
.
UV–Vis (MeOH), kmax (nm) (logꢀÞ: 485 (2.5), 249 (4.2),
210 (4.3). 1H NMR (acetone-d6, 200 MHz: 7.83 (dd,
J ¼ 8:8, 7.5, 1H), 7.58 (d, J ¼ 8:8, 1H); 7.36–7.55 (m,
2H), 7.18 (d, J ¼ 7:5, 1H), 6.52–6.64 (m, 2H), 4.74 (s,
5H), 4.20 (s, 3H). 13C NMR (acetone-d6, 50 MHz: 158.7,
134.3, 121.5, 106.7, 98.5, 89.3, 88.0, 87.0, 85.6, 80.8, 77.4,
57.3. ES-MS, m=z: 279 (Mþ, 100); MS, m=z: 186(37),
158(59), 143(25), 121(21). Anal. Calc. for C16H15OFePF6
(424.1): C, 45.31; H, 3.56. Found: C, 45.15; H, 3.67%.
[(g6-1-Methoxynaphthalene)FeCpþ][PFꢀ6 ](13). Not
isolated. 1H NMR (acetone-d6, 200 MHz): 7.85–8.35
(m, 4H); 7.10–7.22 (m, 2H); 6.47 (t, J ¼ 6:5, H), 4.66 (s,
5H), 4.43 (s, 3HOMe). 13C NMR (acetone-d6, 50 MHz):
156.0, 132.5, 132.2, 131.5, 126.5, 96.4, 88.6, 84.4, 81.3,
60.8, 76.7, 58.1.
4.2.3. [(g6-5,8-Dimethoxynaphthalene)FeCpþ][ꢀ6 ] (9)
and
(10)
[(g6-1,4-dimethoxy-naphthalene)FeCpþ][PFꢀ6 ]
Following the procedure detailed in 4.2.1, complex 1
(11.60 g, 24.8 mmol) was added to liquid 1,4-dimeth-
oxynaphthalene at 130 °C and the reaction was stirred
for 2.5 h to afford, after work up, a mixture of regioi-
somers 9 and 10 in a ratio of 19:1. Crystallization from
CH2Cl2/toluene (5:1) afforded pure 9 (9.83 g, 21.7 mmol,
87%). Fractional crystallization of the mother liquor
furnished a sample of 10. Solvent removal gave a residue
that was taken up in warm hexane and filtered. Crys-
tallization recovered 1,4-dimethoxynaphthalene (17.5 g).
[(g6-5,8-Dimethoxynaphthalene)FeCp] [PF6] (9).
Red crystals. Melting point: 166 °C (dec.). IR(CH2Cl2):
3071w, 2940w, 1628m, 1529m, 1372m, 1277m, 1090m,
841s, 558m cmꢀ1. UV–Vis (MeOH), kmax (nm) (logꢀÞ:
494 (2.7), 248 (4.1), 209 (4.2). 1H NMR (DMSO-d60, 200
MHz), 7.30 (AA0BB0, 2H), 7.06 (s, 2H), 6.47 (AA BB0,
2H), 4.69 (s, 5H), 4.03 (s, 6H). 13C NMR (DMSO-d6, 50
MHz): 149.2, 106.4, 88.6, 86.5, 79.4, 76.3, 56.6. ES-MS,
m=z: 309 (Mþ, 100); MS, m=z: 438(28), 292(98), 270(37),
252(60), 188(71), 186(36), 173(100), 107(48). Anal. Calc.
for C17H17O2FePF6 (454.1): C, 44.96; H, 3.77. Found:
C, 44.87; H, 3.80%.
4.2.5. [(g6-6-Methoxynaphthalene)FeCpþ][PFꢀ6 ] (13)
and [(g6-2-methoxy-naphthalene)FeCpþ][PFꢀ6 ] (14)
Following the procedure detailed in 4.2.1, complex 1
(295 mg, 0.63 mmol) was added to 2-methoxynaphtha-
lene (0.491 mg, 3.10 mmol) at 80 °C. The reaction was
stirred at 130 °C for 2 h to afford, after work up, a
mixture of regioisomers 13 and 14 in a ratio of 10:1 (263
mg, 98%). Crystallization from CH2Cl2/toluene (5:1)
afforded 13 (239 mg, 0.54 mmol, 86%).
[(g6-6-Methoxynaphthalene)FeCpþ][PFꢀ6 ](13). Red
crystal. Solid. Melting point: 141 °C. IR(CH2Cl2):
3071w, 2944w, 1629m, 1471m, 1277m, 847s, 558m,
cmꢀ1. UV–Vis (MeOH), kmax (nm) (logꢀÞ: 482 (2.4), 257
(4.2), 209 (4.3).1H NMR (acetone-d6, 200 MHz): 8.08
(d, J ¼ 9:4, 1H), 7.52 (dd, J ¼ 9:4, 2.4, 1H), 7.26–7.34
(m, 3H), 6.39–6.54 (m, 2H), 4.74 (s, 5H), 4.02 (s, 3H).
13C NMR (acetone-d6, 50 MHz): 162.7, 134.3, 128.8,
104.0, 101.9, 90.9, 87.4, 85.9, 85.8, 84.5, 77.2, 56.5. ES-
MS, m=z: 279 (Mþ, 100). Anal. Calc. for C16H15OFePF6
(424.1): C, 45.31; H, 3.56. Found: C, 45.54; H, 3.65%.
[(g6-2-Methoxynaphthalene)FeCpþ][PFꢀ6 ](14). Not
isolated. 1H NMR (acetone-d6, 200 MHz): 7.73–7.82 m,
4H), 7.25–7.35 (m, 1H), 6.42–6.47 (m, 1H), 4.64 (s, 5H),
4.12 (s, 3H). 13C NMR (acetone-d6, 50 MHz): 158.4, 132.7,
132.0, 131.0, 129.9, 95.0, 93.7, 84.4, 77.1, 75.0, 70.5, 57.4.
[(g6-1,4-Dimethoxynaphthalene)FeCpþ][PFꢀ6 ] (10).
Red crystals. Melting point: 145 °C (dec.). IR(CH2Cl2):
3071w, 2941w, 1627w, 1528w, 1468w, 1378m, 1274m,
1092m, 846s, 558m cmꢀ1 1H NMR (DMSO-d6, 200
.
MHz) 8.20 (AA0BB0, 2H), 7.85 (AA0BB0, 2H), 6.37 (s,
2H), 4.52 (s, 5H), 4.27 (s, 6H). 13C NMR (DMSO-d6, 50
MHz): 131.1, 125.7, 125.6, 86.2, 75.6, 65.1, 57.8. ES-MS,
m=z: 309 (Mþ, 100). Anal. Calc. for C17H17O2FePF6
(454.1): C, 44.96; H, 3.77. Found: C, 44.34; H, 3.82%.
Use of trichloroethane as solvent. The pyrene complex
1 2.08 g (4.44 mmol) was added to a solution of 1,4-di-
methoxynaphthalene (1.25 g, 6.64 mmol) in 1,1,2-tri-
chloroethane (25 ml) in a pressure resistant Schlenk tube.
The reaction was magnetically stirred for 2.5 h at 130 °C
to afford, after work up, a mixture of regioisomers 9 and
10 in a ratio of 14:1. Crystallization from CH2Cl2/tolu-
ene (5:1) afforded pure 9 (1.28 g, 2.82 mmol, 63%).
4.3. Preparation of (g6-arene)(g5-cyclopentadienyl)-
iron(II) hexafluorophosphate complexes by arene ex-
change in the naphthalene complex 2
4.2.4. [(g6-5-Methoxynaphthalene)FeCpþ][PFꢀ6 ] (11)
and [(g6-1-methoxy-naphthalene)FeCpþ][ PFꢀ6 ] (12)
Following the procedure detailed in 4.2.1, complex 1
(292 mg, 0.62 mmol) was added to 1-methoxynaphtha-
lene (0.45 ml, 3.11 mmol). The reaction was stirred at
130 °C for 2 h to afford, after work up, a mixture of
4.3.1. [(g6-Benzocyclobutene)FeCpþ][PFꢀ6 ] (15)
[(g6-Naphthalene)FeCpþ][PFꢀ6 ] (2) (400 mg, 1.02
mmol) was added to a solution of benzocyclobutene

E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
1917
1
(1.00 g, 10 mmol) in 1,2-dichloropropane (0.50 ml). The
reaction was stirred at 120 °C for 3 h. Work-up as de-
scribed in 4.2.1 afforded complex 15 as yellow powder
(328 mg, 0.88 mmol, 87%).
[(g6-Benzocyclobutene)FeCpþ][PF6ꢀ] (15). IR(CH2
Cl2): 3070w, 2948w, 1422m, 1010w, 850s, 558m cmꢀ10 . 1H
NMR (DMSO-d6): 6.51 (AA0BB0, 2H), 6.02 (AA BB0,
2H), 5.09 (s, 5H), 3.34 (s, 4H). 13C NMR (DMSO-d6, 50
MHz): 110.5, 84.6, 84.2, 77.6, 30.6. MS (ES), m=z: 225
(Mþ, 100); MS, m=z: 239(6), 186(52), 104(100), 78(40).
Anal. Calc. for C13H13FePF6 (370.1): C, 42.19; H, 3.54.
Found: C, 42.54; H, 3.69%.
846s, 558m. H NMR (DMSO-d6, 200 MHz): 6.38 (t,
J ¼ 1:7, 1H), 6.05-6.25 (m, 3H), 5.04 (s, 5H); 3.93 (s,
6H). 13C NMR (DMSO-d6, 50 MHz): 133.6, 83.3, 75.8,
69.8, 63.1, 57.1. ES-MS, m=z: 259 (Mþ, 100); MS, m=z:
186(81), 138(100), 121(38), 107(81). Anal. Calc. for
C13H15O2FePF6 (404.1): C, 38.64; H, 3.74. Found: C,
37.99; H, 3.76%.
4.3.3. [(g6-1,3,5-Trimethoxybenzene)FeCpþ][PFꢀ6 ](17)
[(g6-Naphthalene)FeCpþ] PFꢀ6 ] (2) (239 mg, 0.58
mmol) and 1.3,5-trimethoxybenzene (500 mg, 2.97
mmol) were stirred at 120 °C for 1 h. Work-up as de-
scribed in 4.2.1 afforded complex 17 as yellow powder
(240 mg, 0.55 mmol, 95%).
4.3.2. [(g6-1,3-Dimethoxybenzene)FeCpþ][PFꢀ6 ] (16)
[(g6-Naphthalene)FeCpþ][PFꢀ6 ] (2) (400 mg, 1.02
mmol) and 1.3-dimethoxybenzene (0.50 ml, 3.85 mmol)
were stirred at 120 °C for 1 h. Work-up as described in
4.2.1 afforded complex 16 as yellow powder (301 mg,
0.74 mmol, 98%).
[(g6-1,3-Dimethoxybenzene)FeCpþ][PFꢀ6 ](16). Mel-
ting point: 140 °C. IR(CH2Cl2): 2927m, 2854m, 1547w,
1500w, 1463m, 1329m,, 1299m, 1212m, 1165m, 1029m,
[(g6-1,3,5-Trimethoxybenzene)FeCpþ][PFꢀ6 ] (17).
Melting point: 175 °C. IR(CH2Cl2): 3109w, 3072w,
2944w, 1548w, 1461m, 1416m, 1356m, 1206m, 1161m,
1048m, 846s, 558m cmꢀ1 1H NMR (DMSO-d6, 200
.
MHz): 6.24 (s, 3H), 5.00 (s, 5H), 3.94 (s, 9H). 13C NMR
(DMSO-d6, 50 MHz): 132.0, 75.5, 59.1, 57.3. ES-MS,
m=z: 289 (Mþ, 100). Anal. Calc. for C14H17O3FePF6
(434.1): C, 38.74; H, 3.95. Found: C, 38.67; H, 3.91%.
Table 2
Summary of crystal data, intensity measurement, and structure refinement for 9 and 10
9
10
Formula
(C12H12O2)Fe(PF6)
354.4
(C12H12O2)Fe(PF6)
354.4
triclinic
Molecular weight
Crystal system
Space group
orthorhombic
Cmcm
ꢂ
P1
ꢁ
a (A)
19.443(2)
13.2710(14)
13.8630(14)
90
7.326(2)
10.216(3)
13.033(5)
108.97(1)
94.21(1)
95.25(1)
913.2(5)
2
ꢁ
b (A)
ꢁ
c (A)
a (°)
b (°)
c (°)
90
90
3
ꢁ
V (A )
3577.0(6)
8
1.686
Z
Dcalc (g cmꢀ3
Crystal size (mm)
)
1.652
0.13 ꢃ 0.17 ꢃ 0.30
red
1.002
0.17 ꢃ 0.20 ꢃ 0.26
orange
0.981
Crystal color
l(Mo Ka) (mmꢀ1
)
T
min, Tmax
0.8447, 0.8874
0.572
3274
0.8174, 0.8827
0.572
3135
ꢀ1
ꢁ
(A
ððsin hÞ=kÞ
)
max
Number of measured reflections
Number of independent reflections
Number of observed reflections
Rint
1531
1084
2900
2031
0.065
0.031
Criterion for observed
Refinement (on F)
jFoj > 4rðFoÞ
full-matrix
170
jFoj > 4rðFoÞ
full-matrix
244
Number of parameters
Weighting scheme pa
Maximum D=r
0.0004
0.001
0.0002
0.0001
ꢀ3
ꢁ
Maximum and minimum Dq (e A
)
0.57, )0.63
1.26(3)
0.045, 0.041
0.56, )0.66
1.69(3)
0.044, 0.044
Sb (all data)
Rc, wRd
2
a w ¼ 1=½r2ðFoÞ þ pðFoÞ ꢄ.
P
P
2
1=2
b S ¼ ½ fððFo ꢀ FcÞ= ðFoÞÞ g=ðNref ꢀ NvarÞꢄ
.
P
P
c R ¼ jjFoj ꢀ jFcjj= jFoj.
P
P
2
2 1=2
d wR ¼ ½ ðwjFoj ꢀ jFcjÞ = wjFoj ꢄ
.

1918
E. Peter K€undig et al. / Inorganica Chimica Acta 357 (2004) 1909–1919
4.3.4. [(g6-Iodobenzene)FeCpþ]PFꢀ6 ] (18)
Acknowledgements
[(g6-Naphthalene)FeCpþ]PFꢀ6 ] (2) (1.00 g, 2.54
mmol) and iodobenzene (3 ml, 26.9 mmol) were stirred
at 140 °C for 2 h. Work-up as described in 4.2.1 afforded
complex 19 as yellow powder (880 mg, 1.87 mmol, 74%).
[(g6-iodobenzene)FeCpþ][PFꢀ6 ] (18). Yellow pow-
der. Melting point: 185–195 °C. IR(CH2Cl2): 3080w,
1442w, 1422w, 1404w, 1274m, 1052w, 1016w, 846s,
We thank the Swiss National Science Foundation for
financial support of this work.
References
1
558m cmꢀ1. H NMR (DMSO-d6, 200 MHz): 6.79 (d,
[1] (a) T.H. Coffield, V. Sandel, R.D. Closson, J. Am. Chem. Soc. 79
(1957) 5826;
J ¼ 6:3, 2H), 6.24–6.40 (m, 3H), 5.13 (s, 5H). 13C NMR
(DMSO-d6, 50 MHz): 95.6, 88.8, 86.8, 78.7, 60.3. ES-
MS, m=z: 325 (Mþ, 100). Anal. Calc. for C11H10IFePF6
(469.4): C, 28.12; H, 2.14. Found: C, 28.62; H, 2.22%.
(b) M.L.H. Green, L. Pratt, G. Wilkinson, J. Chem. Soc. (1960)
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