Heterobimetallic Fe-Pd and Fe-Pt NCN pincer complexes (NCN = [C6H2(CH2NMe2)2-2 ,6]-)

Article abstract of DOI:10.1016/j.ica.2006.05.045

The meta-diaminoaryl ferrocenes Fc-NCN-H (3) and Fc-C{triple bond, long}C-NCN-H (5) (Fc = (η⁵-C₅H₅)(η⁵-C₅ H₄)Fe, NCN-H = C₆H₃(CH₂NMe₂)₂-3, 5) can be used as precursors in the preparation of heterobimetallic transition metal complexes of structural type Fc-NCN-MX (NCN = [C₆H₂(CH₂NMe₂)₂-2 ,6]^-; MX = PdCl (7), PtCl (8), PtI (9)) and Fc-C{triple bond, long}C-NCN-MX (MX = PdCl (11), PdI (12), PtCl (13)), respectively. They are accessible by applying different synthesis procedures, including oxidative addition and metallation-transmetallation processes. Cyclovoltammetric studies show that the ferrocene moieties in 3, 5, 7-9 and 11-13 can reversibly be oxidised. The potential of the Fe(II)/Fe(III) redox couple decreases with increasing electron density at the NCN pincer unit. The use of 8 as a possible (electro)chemical sensor in the detection of SO₂ is discussed as well. The solid-state structures of 8 and 13 are reported. The crystals of 8 contain two molecules of 8 in the asymmetric unit. The plane of the C₆H₂ moiety is with 27.2(3)° and 38.2(3)° tilted towards the C₅H₄ entity, while in 13 an angle of 45.9(3)° can be found. The d⁸-electron configured platinum atoms possess a somewhat distorted square-planar surrounding, setup by two Me₂NCH₂ ortho-substituents, the NCN C_ipso carbon atom and the chloride ligand.

Full text of DOI:10.1016/j.ica.2006.05.045

Inorganica Chimica Acta 359 (2006) 4454–4462
www.elsevier.com/locate/ica
Heterobimetallic Fe–Pd and Fe–Pt NCN pincer
complexes (NCN = [C6H2(CH2NMe2)2-2,6]ꢀ)
a
b
c
Stefan Ko¨cher , Martin Lutz , Anthony L. Spek b,1, Rajendra Prasad ,
d
d
a,
*
Gerard P.M. van Klink , Gerard van Koten , Heinrich Lang
a
Technische Universita¨t Chemnitz, Fakulta¨t fu¨r Naturwissenschaften, Institut fu¨r Chemie, Lehrstuhl fu¨r Anorganische Chemie, Straße der Nationen 62,
09111 Chemnitz, Germany
b
Bijvoet Center for Biomolecular Research, Crystal and Structural Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
c
Indian Institute of Technology Roorkee, Roorkee, 247 667 Uttaranchal, India
Debye Institute, Organic Chemistry and Catalysis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
d
Received 18 April 2006; accepted 2 May 2006
Available online 25 July 2006
Abstract
The meta-diaminoaryl ferrocenes Fc–NCN–H (3) and Fc–C„C–NCN–H (5) (Fc = (g5-C5H5)(g5-C5H4)Fe, NCN–H =
C6H3(CH2NMe2)2-3,5) can be used as precursors in the preparation of heterobimetallic transition metal complexes of structural type
Fc–NCN–MX (NCN = [C6H2(CH2NMe2)2-2,6]ꢀ; MX = PdCl (7), PtCl (8), PtI (9)) and Fc–C„C–NCN–MX (MX = PdCl (11), PdI
(12), PtCl (13)), respectively. They are accessible by applying different synthesis procedures, including oxidative addition and metalla-
tion–transmetallation processes.
Cyclovoltammetric studies show that the ferrocene moieties in 3, 5, 7–9 and 11-13 can reversibly be oxidised. The potential of the
Fe(II)/Fe(III) redox couple decreases with increasing electron density at the NCN pincer unit. The use of 8 as a possible (electro)chemical
sensor in the detection of SO2 is discussed as well.
The solid-state structures of 8 and 13 are reported. The crystals of 8 contain two molecules of 8 in the asymmetric unit. The plane of
the C6H2 moiety is with 27.2(3)ꢀ and 38.2(3)ꢀ tilted towards the C5H4 entity, while in 13 an angle of 45.9(3)ꢀ can be found. The d8-elec-
tron configured platinum atoms possess a somewhat distorted square-planar surrounding, setup by two Me2NCH2 ortho-substituents,
the NCN Cipso carbon atom and the chloride ligand.
ꢁ 2006 Elsevier B.V. All rights reserved.
Keywords: NCN pincer; Ferrocene; Palladium; Platinum; Halide; Sensor; Cyclicvoltammetry; X-ray crystal structure
1. Introduction
r-bonds are present, due to the chelating effect of, i.e.
the two Me2NCH2 ortho-substituents [3]. The synthesis
of para-functionalised Y–NCN–MX complexes (M = Ni,
Pd, Pt; X = halide; Y = alkynyl, halide,. . .) opens the
possibility to prepare larger molecules with specific phys-
ical and chemical properties [4]. Such species are of
particular interest, since they can be used as building
blocks in, for example, the synthesis of one-dimensional
molecular wires with electronic conduction along a linear
p-conjugated organometallic chain [5]. They also provide
an entry into liquid crystalline materials [6], homogeneous
catalysis or molecular electronics, i.e. optical and physical
sensors [7]. Among them, redox-active organic and/or
Over the last years, the manifold coordination chemis-
try of diphosphino- and disulfido-aryl anions and the
related diaminoaryl pincers NCN (NCN = [C6H3-
(CH2NMe2)2-2,6]ꢀ) towards different transition metal ions
has been intensively investigated [1,2]. In this accessible
transition metal pincer complexes, stable metal–carbon
*
Corresponding author. Tel.: +49 3715311673.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
Author, to whom correspondence pertaining crystal structure analysis
1
should be addressed.
0020-1693/$ - see front matter ꢁ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.ica.2006.05.045

S. Ko¨cher et al. / Inorganica Chimica Acta 359 (2006) 4454–4462
4455
organometallic species with reversibly switchable electron
density and electronic properties are attractive building
blocks. The one-electron reservoir ferrocene is, due to
its robustness, a most promising unit to be incorporated
in such multimetallic assemblies.
The oxidation of ferrocene-based compounds is possi-
ble by using electrochemical methods such as cyclicvol-
tammetry to determine the Fe2+/Fe3+ redox potential
and with that the electron density at the ferrocene
moiety. This gives rise to the possibility to use such sys-
tems as sensory materials which can electrochemically be
read out.
We report here on the synthesis of NCN pincer-substi-
tuted ferrocenes of type Fc–NCN–H and Fc–C„C–
NCN–H (NCN–H = C6H3(CH2NMe2)2-3,5) and on their
subsequent metallation to heterobimetallic Fc–NCN–MX
and Fc–C„C–NCN–MX complexes (NCN = [C6H2(CH2-
NMe2)2-2,6]ꢀ; M = Pd, Pt; X = Cl, I), respectively. Their
electrochemical behaviour and reversible absorption ability
towards SO2 is discussed as well.
In 3 the NCN pincer moiety is connected to the ferro-
cene core via a single carbon–carbon bond. This might lead
to repulsive interactions between the ortho-hydrogen atoms
of the C5H4 and C6H3 rings and hence, these two planes
will be twisted towards each other. This may prevent an
effective electronic communication between the iron atom
and the metallated NCN pincer unit. Thus, the insertion
of a suitable p-conjugated –C„C– or –C@C– spacer is a
promising alternative, although the electronically interact-
ing parts will be more separated from each other. There-
fore, Fc–C„C–NCN–H (5) was prepared in
a
Sonogashira reaction [8d] by reacting Fc–C„CH (4) with
2 in the presence of catalytic amounts of [(Ph3P)2PdCl2]/
[CuI] in diisopropyl amine as solvent (Eq. (2)). After
appropriate work-up, 5 could be isolated as an orange–
red oil in 75% yield.
NMe2
NMe2
H
Fe
+
I
2. Results and discussion
2.1. Synthesis and spectroscopy
2
4
NMe2
NMe2
Carbon–carbon cross-coupling catalysed by transition
metals can successfully be used to prepare rigid-rod struc-
tured p-conjugated organic and organometallic NCN
pincer-functionalised ferrocenes [8,9].
[Pd / Cu]
iPr2NH, 5 h reflux
Fe
Treatment of Fc–B(OH)2 (1) (Fc = (g5-C5H5)-
(g5-C5H4)Fe) with I-1-C6H3(CH2NMe2)2-3,5 (2) following
the Suzuki cross-coupling protocol [8e] in presence of
catalytic amounts of [(dppf)PdCl2] (dppf = 1,10-bis-
(diphenylphosphino)ferrocene) gives Fc–NCN–H (3)
(NCN–H = C6H3-(CH2NMe2)2-3,5) (Eq. (1)) which after
appropriate work-up, can be isolated as a red oil in 27%
yield.
5
Compounds 3 and 5 are soluble in common organic sol-
vents, such as n-hexane, toluene, diethyl ether and
dichloromethane.
Treatment of n-hexane solutions containing 3 or 5 with
nBuLi gave Li-3 and Li-5 which further react with an excess
of iodine to produce the iodo-functionalised sandwich
complexes Fc–NCN–I (6) and Fc–C„C–NCN-I (10) as
orange oils in 82% and 80% yield, respectively (Schemes
1 and 2).
On reacting either 6 with equimolar amounts of
[Pt(tol)2(SEt2)]2 (tol = 4-tolyl) in refluxing toluene for
5 min, or 10 with stoichiometric amounts of the Pd source
[Pd2(dba)3 Æ CHCl3] (dba = dibenzylideneacetone) in ben-
zene at 25 ꢀC, an oxidative addition of the C–I bond in 6
and 10 to M (M = Pd, Pt) occurs. After appropriate
work-up, the respective orange coloured heterobimetallic
complexes Fe–NCN–PtI (9) and Fc–C„C–NCN–PdI
(12) can be isolated in 71% and 73% yield, respectively
(Schemes 1 and 2).
NMe2
NMe2
B(OH)2
Fe
+
I
2
1
NMe2
NMe2
[(dppf)PdCl2]
Fe
DME/NaOH, 6 d reflux
A possibility to synthesise 7, 8, 11 and 13 is given by a
two-step metallation–transmetallation procedure: lithiation
n
of 3 and 5 by the addition of BuLi (vide supra) and sub-
sequent treatment of Li-3 and Li-5 with [(Et2S)2PdCl2] or
3

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S. Ko¨cher et al. / Inorganica Chimica Acta 359 (2006) 4454–4462
NMe2
I
3). In addition, the FePt complexes 8, 9 and 13 show typi-
cal 195Pt satellites with coupling constants of 36–38 Hz
(3JPtH(Me)) and ca. 46 Hz (3JPtH(CH )).
2
Fe
NMe2
In the 13C{1H} NMR spectra of 7–9 and 11–13 the
downfield shift of the CH2 and NMe2 carbon atoms upon
complexation to the group-10 transition metals is observed
as well (i.e. 3: 64.4, 45.4 ppm; 9: 76.8, 56.3 ppm). The ferro-
cene ipso-carbon atoms for 3 and 6–9, where the C6H2
group is directly bonded to the cyclopentadienyl ring,
appears between 84 and 87 ppm. For 5 and 10–13 the pres-
ence of a C„C spacer unit between the sandwich and the
NCN pincer moieties shifts the resonance signal of this car-
bon atom to ca. 65 ppm.
NMe2
NMe2
6
2. I2
½ [Pt(tol)2(SEt2)]2
1. nBuLi
Fe
NMe2
2. (SEt2)2MCl2
M
X
3
Fe
NMe2
7: MX = PdCl
8: MX = PtCl
9: MX = PtI
All other resonances for the ferrocene entity in 3 and 5–
1
13 in both the H and 13C{1H} NMR spectra are not sig-
Scheme 1. Synthesis of 6–9.
nificantly influenced by the differently substituted NCN
units and appear in the region typical for ferrocene-based
complexes.
The C„C stretching frequencies in 5 and 10–13 are not
affected by the introduction of iodine, palladium or plati-
num and are found at ca. 2210 cmꢀ1 in the IR spectra of
these species.
2.2. Electrochemical studies
Cyclovoltammetric studies were carried out for 2, 3, 7
and 8, in acetonitrile and for 5, 8 and 11–13 in tetrahydro-
furan solutions. As examples, the cyclic voltammograms of
2 and 7 are depicted in Figs. 1 and 2, respectively.
The cyclicvoltammogram of 2 shows an irreversible oxi-
dation at +0.76 V, which also has been found at similar
potentials for complexes 3, 5, 7, 8 and 11–13 (Table 1). It
most likely arises from the oxidation of the NCN pincer
unit [9,11]. An analogous behaviour has been reported
for benzyl amine [12]. The second wave at +2.13 V can
be assigned to the Iꢀ/I2 oxidation.
The redox potentials of monometallic 3 and 5 are, when
compared to the Cp2Fe/Cp2Fe+ redox-couple (Cp2Fe =
(g5-C5H5)2Fe), shifted to a somewhat more positive value
(Table 1). This change can be explained by the presence
of electron withdrawing groups (the NCN pincer and the
C„C moieties) in 3 and 5 compared to ferrocene, taken
as standard [13].
Scheme 2. Synthesis of 10–13.
[(Et2S)2PtCl2] in a 1:1 molar ratio produces heterobimetal-
lic Fc–NCN–MCl (7: M = Pd; 8: M = Pt) or Fc–C„C–
NCN–MCl (11: M = Pd; 13: M = Pt) in yields between
30% and 75% (Schemes 1 and 2). Nevertheless, the presence
of a C„C triple bond as given in 11 and 13 decreases the
yield of these compounds significantly. A similar trend
was found for NCN pincer-functionalised ferrocenes with
two C„C moieties, where the metallation–transmetalla-
tion procedure failed [9,10]. In comparison, the iodine-oxi-
dative addition route (synthesis of 12) doubles the yield
(58%), when compared with the lithium-transmetallation
protocol (11: 29%).
The 1H NMR spectra of 3, 5, 6 and 10 show the
expected resonance signals typical for non-metallated
NCN-pincer complexes [2,3]. The Me2N and CH2 protons
appear as singlets at 2.26 and 3.43 ppm for 3 and 2.23 and
3.37 ppm for 5. The appropriate resonances for 6 and 10
are observed at 2.35 and 3.54 ppm (6) and 2.34 and
3.51 ppm (10). Coordination of the ortho-Me2NCH2 sub-
stituents to palladium (7, 11 and 12) or platinum (8, 9
and 13) results in a significant low-field shift of the Me2N
(2.9–3.2 ppm) and CH2 (ca. 4.0 ppm) protons. The signals
for the C6H2 entity also confirm the binding of this group
to Pd and Pt. Thus, due to the increased electron density at
the benzene ring a high-field shift from 7.31 3 or 7.33 ppm 5
to, for example, 6.90 ppm for 7 and 11 is observed (Section
35
30
25
20
15
10
5
0
-5
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
[
]
V
E
Fig. 1. Cyclic voltammogram of 2 in acetonitrile in the presence of [n-
Bu4N][PF6] (c = 0.10 M, 25 ꢀC, argon, scan rate = 200 mV sꢀ1). Potentials
are referenced to the Cp2Fe/Cp2Fe+ redox couple as internal standard
(Cp2Fe = (g5-C5H5)2Fe, E1/2 = 0.00 V).

S. Ko¨cher et al. / Inorganica Chimica Acta 359 (2006) 4454–4462
4457
2.0
hydrogen atoms and on the other hand by the extended dis-
tance between the interacting entities by the C„C triple
bond.
1.5
1.0
0.5
The influence of the Fe(II)/Fe(III) redox couple towards
the presence of either palladium or platinum can also be
used to monitor modifications in the electron density at
the NCN building block by cyclicvoltammetry. It is known
that platinum-NCN pincer complexes possess the ability to
reversibly bind SO2 [14]. For example, colourless HO–
NCN–PtCl absorbs gaseous SO2 to form orange HO–
NCN–Pt(Cl)(SO2). This colour change is combined with
a change of the electron density at the NCN pincer unit
[14]. With this in mind, we treated a tetrahydrofuran solu-
tion containing 8 with SO2 directly in the CV cell (Eq. (3)).
0.0
-0.5
-1.0
-0.8 -0.6
-0.4 -0.2
0.0
0.2
E [v]
0.4
0.6
0.8
1.0
1.2
Fig. 2. Cyclic voltammogram of 7 in acetonitrile in the presence of [n-
Bu4N][PF6] (c = 0.10 M, 25 ꢀC, argon, scan rate = 200 mV sꢀ1). Potentials
are referenced to the Cp2Fe/Cp2Fe+ redox couple as internal standard
(Cp2Fe = (g5-C5H5)2Fe, E1/2 = 0.00 V).
NMe2
Pt Cl
NMe2
NMe2
Pt
SO2
Cl
+ SO2
- SO2
Fe
Fe
NMe2
Table 1
Electrochemical data of 2, 3, 5, 7, 8 and 11–13a
8
14
Compound
E1/2 (V)
DEp (mV)
Eox (V)
I–NCNH (2)b
+0.76, +2.13
+0.72
+0.83
+0.70
+0.68
CpFe(C5H4NCNH) (3)b
CpFe(C5H4C2NCNH) (5)c
CpFe(C5H4NCNPdCl) (7)b
CpFe(C5H4NCNPtCl) (8)b
CpFe(C5H4NCNPtCl) (8)c
CpFe(C5H4C2NCNPdCl) (11)c
CpFe(C5H4C2NCNPdI) (12)c
CpFe(C5H4C2NCNPtCl) (13)c
a
+0.02
+0.10
+0.01
ꢀ0.02
ꢀ0.05
+0.08
+0.06
ꢀ0.03
80
192
85
The potential for the Fe2+/Fe3+ couple for 8 is found at
ꢀ0.05 V. Upon bubbling SO2 through this solution this
wave is shifted by 20 mV to ꢀ0.03 V upon formation of
Fc–NCN–Pt(Cl)(SO2) (14). Although the shift is relative
small we address the change to the presence of coordinated
SO2, since the measurements were performed directly after
each other. This finding indicates that the iron centre
becomes somewhat more difficult to oxidise, which can
explained by a reduced electron density at 14, when com-
pared with 8, due to the g1-S coordination of SO2 to plat-
inum (via interaction of the filled Pt-dz2 orbital with the
empty r* of SO2). This denotes that these heterobimetallic
ferrocene–platinum complexes may be used as chemical
sensors for SO2. We are currently investigating this topic
in further detail.
70
146
150
105
133
+0.69
d
+0.76
+0.73
E1/2 is the potential of the Fe2+/Fe3+ redox couple, DEp is the peak-to-
peak separation between the reduction and oxidation wave maxima, Eox is
the potential of the irreversible oxidation.
b
In acetonitrile.
In tetrahydrofuran.
Broad oxidation wave which could not be assigned, due to the electro-
c
d
chemical window of the solvent used.
The NCN complexation to either palladium or platinum
in 7, 8 and 11–13 leads to a small shift of the Fe2+/Fe3+
potentials to negative values (Table 1). For example, the
cyclicvoltammogram of 7 reveals the ferrocene-based wave
at +0.01 V, showing a small influence of the presence of the
palladium(II) ion on the redox potential of the iron atom.
As compared with 3, a somewhat more pronounced shift
(ꢀ40 mV) for 8 is found, where a platinum(II) ion is pres-
ent. A similar dependence of the ferrocene redox couple
towards different metal ions was found for bis-NCN pin-
cer-substituted ferrocenes [9]. This confirms that the Fe(II)
ion is easier to oxidise, which is most likely caused by the
ortho-metallation of the NCN pincer moiety (neutral versus
anionic NCN; Pd(II), Pt(II)). For 11–13, where the ferro-
cene and the pincer entities are connected by an acetylenic
unit, an analogous dependence of the ferrocene redox-cou-
ple towards the presence of either Pd(II) or Pt(II) is
observed (Table 1). The degree of interaction is thereof
similar for aryl-ferrocenes with a slightly distorted overlap
of the p-orbitals. This distortion overlap can be explained
by on the one hand the repulsive interaction of the ortho-
2.3. Solid state structures of 8 and 13
Single crystals of 8 and 13 suitable for X-ray structure
analysis could be obtained by slow evaporation of a solu-
tion of either 8 or 13 in a dichloromethane–acetone mixture
(ratio 20:1) at ꢀ30 ꢀC. The molecular structures of 8 and 13
are shown in Figs. 3 and 4. Geometric details are listed in
Table 2 and the experimental crystal data are summarised
in Section 3.
Complexes 8 and 13 both crystallise in the monoclinic
space group P21/c. The main molecular features of 8 and
13 resemble the structural data, characteristic for ferrocene
and NCN pincer complexes [2,15]. The asymmetric unit of
crystals of 8 contains two molecules of 8, having similar
bond distances and bond angles. Therefore, only the data
for the residue depicted in Fig. 3 is discussed. As character-
istic for other ferrocene complexes the Fe1–D1 and Fe1–
D2 separations (D1, D2 = centroids of the cyclopentadie-

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S. Ko¨cher et al. / Inorganica Chimica Acta 359 (2006) 4454–4462
C1, N1, N2 and Cl1 (Figs. 3 and 4). The C1–Pt1–Cl1 bond
C18
C19
C21
C9
angles are with 177.57(11)ꢀ 8 and 178.91(19)ꢀ 13 almost lin-
ear, whereas the N1–Pt1–N2 angles with 164.65(12)ꢀ 8 and
163.09(19)ꢀ 13 deviate from linearity. The coordination
plane around Pt1 is almost coplanar with the plane of
the C6H2 ring (8: 8.9ꢀ, 13: 12.7ꢀ). As expected, the C„C
functionality in 13 is linear with angels of 177.0(7)ꢀ (C4–
C13–C14) and 177.3(7)ꢀ (C13–C14–C15), respectively.
A further noticeable feature of 8 and 13 is the angle of
the planes between the C6H2 unit and the g5-coordinated
C5H4 rings. For 8 tilting angles of 27.2(3)ꢀ and 38.2(3)ꢀ
and for 13 a value of 45.9(3)ꢀ are found. This orientation
averts an optimal overlap between the p-orbitals of the
cyclopentadienyl and NCN–PtCl pincer fragments [16].
However, the interplannar angle seems mainly to depend
on crystal packing effects, since for 8 two different angels
were found and for 13, with less repulsive interactions
between the ortho-hydrogen atoms of the C5H4 and C6H2
rings, due to the C„C spacer, a lager value has been
observed.
C7
N1
C22
Fe1
C20
C2
C3
C8
C14
C15
C4
C1
Pt1
Cl1
C13
C11
C16
C17
C5
C6
N2
C10
C12
Fig. 3. Displacement ellipsoid plot of the molecular structure of 8 in the
crystal, drawn at the 50% probability level. The second independent
molecule is omitted for clarity.
C21
C22
C20
C9
C24
C23
C8
C7
N1
Fe1
C16
C2
C3
C17
C14
C1
C4
C13
Pt1
3. Experimental part
C15
Cl1
C18
C19
3.1. General methods
C6
C5
N2
C10
All reactions were carried out under an atmosphere of
purified nitrogen using standard Schlenk techniques. Tetra-
hydrofuran, diethyl ether, benzene, toluene and n-hexane
were purified by distillation from sodium/benzophenone
C12
C11
Fig. 4. Displacement ellipsoid plot of the molecular structure of 13 in the
i
crystal, drawn at the 50% probability level.
ketyl. Pr2NH was dried by distillation from KOH. Infra-
red spectra were recorded with a Perkin–Elmer FT-IR
1000 spectrometer. NMR spectra were recorded with a
Bruker Avance 250 spectrometer (1H NMR: 250.12 MHz,
13C{1H} NMR: 62.86 MHz) or with a Varian Inova 300
spectrometer (1H NMR: 300.10 MHz, 13C{1H} NMR:
75.47 MHz) in the Fourier transform mode. Chemical
shifts are reported in d units (parts per million) downfield
nyl ligands C5H4 and C5H5, respectively) are found with
˚
˚
1.641(2) and 1.639(3) A for 8 and 1.634(3) A for 13 [15].
The two cyclopentadienyl ligands are thereby rotated by
ꢀ12.2(4)ꢀ 8 or 2.5(5)ꢀ 13 with respect to each other, which
verifies an almost eclipsed conformation. The metals Pt1 (8
and 13) adopt a distorted square-planar geometry set-up by
Table 2
a
˚
Selected bond distances (A), angles (ꢀ), and torsion angels (ꢀ) for 8 and13
Bond distances
Bond angles
Torsion angles
Complex 8c
Pt1–Cl1
Pt1–C1
2.4452(9)
1.925(4)
2.092(3)
2.092(3)
1.641(2)
1.639(3)
Cl1–Pt1–C1
N1–Pt1–N2
Cl1–Pt1–N1
Cl1–Pt1–N2
D1–Fe1–D2b
177.57(11)
164.65(12)
96.19(9)
99.15(9)
178.77(15)
C1–C2–C7–N1
C1–C6–C10–N2
Pt1–N1–C7–C2
Pt1–N2–C10–C6
20.9(5)
22.4(5)
Pt1–N1
ꢀ25.6(4)
Pt1–N2
ꢀ27.8(4)
D1–Fe1b
D2–Fe1b
Complex 13
Pt1–Cl1
Pt1–C1
Pt1–N1
Pt1–N2
C13–C14
Fe1–D1b
Fe1–D2b
a
2.4304(15)
1.914(6)
2.102(5)
2.091(5)
1.169(9)
1.634(3)
1.634(3)
Cl1–Pt1–C1
N1–Pt1–N2
Cl1–Pt1–N1
Cl1–Pt1–N2
C4–C13–C14
C13–C14–C15
D1–Fe1–D2b
178.91(19)
163.09(19)
99.43(14)
97.46(14)
177.0(7)
C1–C2–C7–N1
C1–C6–C10–N2
Pt1–N1–C7–C2
Pt1–N2–C10–C6
25.0(7)
23.8(7)
ꢀ32.4(5)
ꢀ32.6(6)
177.3(7)
177.75(17)
Standard uncertainties are given in the last significant figure(s) in parenthesis.
D1, D2: centroids of the cyclopentadienyl ligands.
b
c
Only one of the two independent molecules is considered.

S. Ko¨cher et al. / Inorganica Chimica Acta 359 (2006) 4454–4462
4459
from tetramethylsilane (d = 0.00 ppm) with the solvent as
C5H4), 69.5 (CH/C5H5), 85.3 (iC/C5H4), 125.6 (CH/
C6H3), 127.7 (CH/C6H3), 138.7 (iC/C6H3), 139.0 (iC/
C6H3). Anal. Calc. for C22H28FeN2 (376.31): C, 70.18; H,
7.50; N, 7.45. Found: C, 69.69; H, 7.57; N, 7.53%.
1
the reference signal (CDCl3: H NMR, d = 7.26; 13C{1H}
NMR, d = 77.0). Cyclicvoltammograms were recorded in
a dried cell purged with purified nitrogen at 25 ꢀC. Plati-
num wires served as working and as counter electrode. A
Ag/AgCl or a saturated calomel electrode served as refer-
ence electrode. For ease of comparison, all electrode poten-
tials are converted using the redox potential of the
ferrocene–ferrocenium couple Cp2Fe/Cp2Fe+ (Cp2Fe =
(g5-C5H5)2Fe) as the reference (E1/2 = 0.00 V) [17]. Elec-
trolyte solutions were prepared from freshly distilled aceto-
nitrile or tetrahydrofuran and [n-Bu4N]PF6 (dried in
oil-pump vacuum at 120 ꢀC, c = 0.1 M). The appropriate
organometallic compounds were added at c = 1.0 mM.
The cyclicvoltammograms were recorded at a scan rate of
200 mV sꢀ1 using a Princeton Applied Research EG&G
263A Analyser or a Radiometer Copenhagen DEA 101
Digital Electrochemical Analyser with an IMT 102 electro-
chemical interface. Melting points were determined using
sealed nitrogen purged capillaries on a Gallenkamp MFB
595010 M melting point apparatus. Microanalyses were
performed by the Dornis und Kolbe, Mikroanalytisches
3.4. Synthesis of 5
Compound 4 (294 mg, 1.4 mmol), 318 mg (1.0 mmol) of
2, 35 mg (0.05 mmol, 5.0 mol%) of [(Ph3P)2PdCl2] and 10
mg (0.05 mmol, 5.0 mol%) of [CuI] were dissolved in
i
20 mL of Pr2NH. The reaction mixture was heated for 5
h to reflux and was then evaporated in oil-pump vacuum.
Chromatography on neutral alumina (5 · 15 cm) with
diethyl ether yielded 20 mg (0.10 mmol, 7% based on 2)
of recovered 4. By changing the solvent to tetrahydrofuran
compound 5 could be isolated as orange-red oil. Yield:
300 mg (0.75 mmol, 75% based on 2).
1
IR (NaCl): [cmꢀ1] 2212 (s) [mC„C]. H NMR (CDCl3):
[d] 2.23 (s, 12H, NMe2), 3.37 (s, 4H, CH2N), 4.20 (pt,
JHH = 1.5 Hz, 2H, C5H4), 4.21 (s, 5H, C5H5), 4.45 (pt,
JHH = 1.5 Hz, 2H, C5H4), 7.18 (s, 1H, C6H3), 7.33 (s, 2H,
C6H3). 13C{1H} NMR (CDCl3): [d] 45.3 (NCH3), 63.9
(NCH2), 65.3 (iC/C5H4), 68.7 (CH/C5H4), 69.9 (CH/
C5H5), 71.3 (CH/C5H4), 85.7 (FcC„C), 88.1 (FcC„C),
123.8 (iC/C6H3), 129.1 (CH/C6H3), 130.7 (CH/C6H3),
138.9 (iC/C6H3). Anal. Calc. for C24H28FeN2 (400.33): C,
72.00; H, 7.05; N, 7.00. Found: C, 71.84; H, 6.92; N, 6.90%.
Laboratorium, Mulheim a. d. Ruhr and by the Department
¨
of Organic Chemistry at Chemnitz, Technical University.
3.2. General remarks
Fc–B(OH)2 (1) [18], I-1-C6H3(CH2NMe2)2-3,5 (2) [19],
Fc–C„CH (4) [20], [PdCl2(SEt2)2] [21], [PtCl2(SEt2)2]
[21,22], [Pd2(dba)3 Æ CHCl3] [23], and [Pt(4-tol)2(SEt2)]2
[24] were prepared the following published procedures.
All other chemicals were commercially available and were
used as received.
3.5. Synthesis of 6
Complex 3 (160 mg, 0.43 mmol) was dissolved in 30 mL
of n-hexane and 0.35 mL (0.56 mmol, 1.6 M solution in n-
n
hexane) of BuLi were added at 25 ꢀC. After stirring the
reaction mixture for 16 h at this temperature all volatiles
were removed (oil-pump vacuum). The orange residue was
dissolved in 30 mL of diethyl ether, treated with 200 mg
(0.79 mmol) of I2 and stirred for 6 h at 25 ꢀC. A solution
of 1.0 g Na2S2O3 in 50 mL of water was then added. The
organic phase was separated, extracted with 50 mL of
water, dried over MgSO4, filtered and evaporated in oil-
pump vacuum to gave 175 mg (0.35 mmol, 82% based on
3) of 6 as an orange oil.
3.3. Synthesis of 3
Compound 1 (1.60 g, 6.96 mmol) and 2.22 g (6.96 mmol)
of 2 were dissolved in 50 mL of dimethoxymethane and
15 mL of 3 M NaOH were added. Afterward 50 mg
(0.07 mmol, 1.0 mol%) of [(dppf)PdCl2] were added at
25 ꢀC. After keeping the reaction mixture for 6 days at
reflux it was cooled to 25 ꢀC, dissolved in 100 mL of chloro-
form followed by addition of 100 mL of water. The aqueous
phase was extracted three times with 100 mL of diethyl
ether. The combined organic phases were dried over
MgSO4, filtered and then all volatiles were evaporated from
the filtrate (oil-pump vacuum). Chromatography on neutral
alumina (5 · 15 cm) with diethyl ether gave 120 mg
(0.65 mmol, 9% based on 1) of recovered Fc–B(OH)2. By
changing the solvent to diethyl ether–tetrahydrofuran (ratio
1:2) 3 has been obtained as a red oil. Yield: 710 mg
(1.89 mmol, 27% based on 1).
1H NMR (CDCl3): [d] 2.35 (s, 12H, NMe2), 3.54 (s, 4H,
CH2N), 4.03 (s, 5H, C5H5), 4.32 (pt, JHH = 1.8 Hz, 2H,
C5H4), 4.71 (pt, JHH = 1.8 Hz, 2H, C5H4), 7.40 (s, 2H,
C6H2). 13C{1H} NMR (CDCl3): [d] 45.5 (NCH3), 66.6
(CH/C5H4), 69.0 (NCH2), 69.0 (CH/C5H4), 69.5 (CH/
C5H5), 84.1 (iC/C5H4), 103.9 (iCI/C6H2), 126.6 (CH/
C6H2), 138.7 (iC/C6H2), 141.5 (iC/C6H2). Anal. Calc. for
C22H27FeIN2 (502.21): C, 52.61; H, 5.42; N, 5.58. Found:
C, 52.01; H, 5.29; N, 5.76%.
1H NMR (CDCl3): [d] 2.26 (s, 12H, NMe2), 3.43 (s, 4H,
CH2N), 4.02 (s, 5H, C5H5), 4.29 (pt, JHH = 1.8 Hz, 2H,
C5H4), 4.67 (pt, JHH = 1.8 Hz, 2H, C5H4), 7.07 (s, 1H,
C6H3), 7.31 (s, 2H, C6H3). 13C{1H} NMR (CDCl3): [d]
45.4 (NCH3), 64.4 (NCH2), 66.6 (CH/C5H4), 68.8 (CH/
3.6. Synthesis of 7
Complex 3 (100 mg, 0.28 mmol) was dissolved in 30 mL
of n-hexane and 0.18 mL (0.28 mmol, 1.6 M solution in
n
n-hexane) of BuLi were drop-wise added at 25 ꢀC. After-

4460
S. Ko¨cher et al. / Inorganica Chimica Acta 359 (2006) 4454–4462
wards, the reaction mixture was stirred for 18 h at this tem-
perature and then all volatiles were removed (oil-pump vac-
uum). The orange residue was dissolved in 30 mL of diethyl
ether, treated with 100 mg (0.28 mmol) of [(Et2S)2PdCl2]
and stirred for 18 h at room temperature. During this time
a precipitate formed which was collected and dried in oil-
pump vacuum. The orange solid was dissolved in 30 mL
of dichloromethane, filtered through a pad of Celite and
dried (oil-pump vacuum) to gave 110 mg (0.21 mmol, 76%
based on [(Et2S)2PdCl2)] of 7 as an orange solid.
M.p.: [ꢀC] 92 (dec). 1H NMR (CDCl3): [d] 3.20 (s,
3
3JPtH = 38.9 Hz, 12H, NMe2), 4.03 (s, JPtH = 46.4 Hz,
4H, CH2N), 4.03 (s, 5H, C5H5), 4.25 (pt, JHH = 1.7 Hz,
2H, C5H4), 4.52 (pt, JHH = 1.7 Hz, 2H, C5H4), 6.93 (s,
2H, C6H2). 13C{1H} NMR (CDCl3): [d] 56.3 (NCH3),
66.0 (CH/C5H4), 68.4 (CH/C5H4), 69.4 (CH/C5H5), 76.8
(NCH2), 87.1 (iC/C5H4), 117.3 (CH/C6H2), 134.4 (iC/
C6H2), 143.4 (iC/C6H3), 147.5 (iCPt/C6H2). Anal. Calc.
for C22H27FeIN2Pt (697.29): C, 37.89; H, 3.90; N, 4.02.
Found: C, 36.81; H, 4.58; N, 4.53%.
M.p.: [ꢀC] 93 (dec.). 1H NMR (CDCl3): [d] 2.97 (s, 12H,
NMe2), 4.02 (s, 4H, CH2N), 4.04 (s, 5H, C5H5), 4.26 (pt,
JHH = 1.8 Hz, 2H, C5H4), 4.50 (pt, JHH = 1.8 Hz, 2H,
C5H4), 6.90 (s, 2H, C6H2). 13C{1H} NMR (CDCl3): [d]
53.1 (NCH3), 66.2 (CH/C5H4), 68.6 (CH/C5H4), 69.5
(CH/C5H5), 74.7 (NCH2), 86.4 (iC/C5H4), 117.7 (CH/
C6H2), 135.7 (iC/C6H2), 144.9 (iC/C6H2), 154.2 (iC/
C6H2). Anal. Calc. for C22H27ClFeN2Pd (517.18): C,
51.09; H, 5.26; N, 5.42. Found: C, 51.19; H, 5.26; N, 5.82%.
3.9. Synthesis of 10
Complex 10 was prepared according to the procedure
described for 6 by using 62 mg (0.15 mmol) of 5, 0.15 mL
(0.24 mmol, 1.6 M in n-hexane) of nBuLi and 70 mg
(0.28 mmol) of I2. Yield: 65 mg (0.12 mmol, 80% based
on 5).
IR (NaCl): [cmꢀ1] 2211 (s) [mC„C]. H NMR (CDCl3):
1
[d] 2.34 (s, 12H, NMe2), 3.51 (s, 4H, CH2N), 4.23 (bs,
7H, C5H4, C5H5), 4.48 (pt, JHH = 1.8 Hz, 2H, C5H4),
7.40 (s, 2H, C6H2). 13C{1H} NMR (CDCl3): [d] 45.6
(NCH3), 65.1 (iC/C5H4), 68.8 (NCH2), 68.8 (CH/C5H4),
69.9 (CH/C5H5), 71.3 (CH/C5H4), 85.1 (FcC„C), 89.4
(FcC„C), 106.3 (iCI/C6H2), 123.5 (iC/C6H2), 131.3 (CH/
C6H2), 141.9 (iC/C6H2). Anal. Calc. for C24H27FeIN2
(526.23): C, 54.78; H, 5.17; N, 5.32. Found: C, 57.30; H,
6.57; N, 3.34%.
3.7. Synthesis of 8
Complex 3 (110 mg, 0.29 mmol) was dissolved in 20 mL
of n-hexane and 0.19 mL (0.30 mmol, 1.6 M solution in n-
hexane) of nBuLi were drop-wise added at 25 ꢀC. The reac-
tion mixture was stirred for 18 h at room temperature.
Afterward, all volatiles were removed in oil-pump vacuum.
The orange residue was dissolved in 20 mL of diethyl ether,
treated with 130 mg (0.29 mmol) of [(Et2S)2PtCl2] and stir-
red for 5 h at 25 ꢀC. During this time a precipitate formed
which was collected and dried (oil-pump vacuum). The
orange solid was dissolved in dichloromethane, filtered
through a pad of Celite and dried in oil-pump vacuum to
gave 130 mg (0.21 mmol, 74% based on [(Et2S)2PtCl2]) of
8 as an orange solid.
3.10. Synthesis of 11
Heterobimetallic 11 was prepared according to the pro-
cedure described for 7. In this respect, 100 mg (0.25 mmol)
of 5, 0.15 mL (0.38 mmol, 2.5 M in n-hexane) of nBuLi and
90 mg (0.25 mmol) of [(Et2S)2PdCl2] were reacted. Yield:
40 mg (0.07 mmol, 29% based on 5).
M.p.: [ꢀC] 95 (dec.). 1H NMR (CDCl3): [d] 3.11 (s,
3JPtH = 38.4 Hz, 12H, NMe2), 4.05 (s, JPtH = 46.6 Hz,
M.p.: [ꢀC] 102 (dec.). (KBr): [cmꢀ1] 2211 (w) [mC„C]. 1H
NMR (CDCl3): [d] 2.92 (s, 12H, NMe2), 3.96 (s, 4H,
CH2N), 4.20 (s, 5H, C5H5), 4.22 (pt, JHH = 1.8 Hz, 2H,
C5H4), 4.44 (pt, JHH = 1.8 Hz, 2H, C5H4), 6.90 (s, 2H,
C6H2). 13C{1H} NMR (CDCl3): [d] 53.0 (NCH3), 66.2
(CH/C5H4), 68.7 (CH/C5H4), 69.8 (CH/C5H5), 74.7
(NCH2), 86.4 (iC/C5H4), 122.6 (CH/C6H2), 135.7 (iC/
C6H2), 144.9 (iC/C6H2), 154.2 (iC/C6H2). Anal. Calc. for
C24H27ClFeN2Pd (541.20): C, 53.26; H, 5.03; N, 5.18.
Found: C, 53.38; H, 5.28; N, 5.67%.
3
4H, CH2N), 4.05 (s, 5H, C5H5), 4.25 (pt, JHH = 1.8 Hz,
2H, C5H4), 4.51 (pt, JHH = 1.8 Hz, 2H, C5H4), 6.94 (s,
2H, C6H2). 13C{1H} NMR (CDCl3): [d] 54.4 (NCH3),
66.0 (CH/C5H4), 68.3 (CH/C5H4), 69.4 (CH/C5H5), 77.7
(NCH2), 87.5 (iC/C5H4), 117.4 (CH/C6H2), 134.1 (iC/
C6H2), 143.1 (iCPt/C6H2), 143.2 (iC/C6H3). Anal. Calc.
for C22H27ClFeN2Pt (605.84): C, 43.61; H, 4.46; N, 4.62.
Found: C, 43.81; H, 4.58; N, 4.53%.
3.8. Synthesis of 9
3.11. Synthesis of 12
Compound
6
(100 mg, 0.20 mmol) and 90 mg
(0.10 mmol) of [Pt(tol)2(SEt2)]2 were dissolved in 20 mL
of toluene and were heated to reflux for 5 min. The
obtained orange solution was then cooled to 25 ꢀC and
concentrated in oil-pump vacuum to 5 mL. Upon addition
of 20 mL of n-hexane an orange precipitate formed which
was collected, washed twice with 10 mL of hexane and
10 mL of diethyl ether and dried in oil-pump vacuum. Yield:
95 mg (0.14 mmol, 71% based on [Pt(tol)2(SEt2)]2).
Complex 10 (50 mg, 0.095 mmol) and 45 mg
(0.043 mmol) of [Pd2(dba)3 Æ CHCl3] were dissolved in
15 mL of benzene. This reaction mixture was stirred for
18 h at 25 ꢀC. Afterwards, 20 mL of tetrahydrofuran were
added and stirring was continued for 2 h. All volatiles were
evaporated in oil-pump vacuum and the residual greenish-
black solid was dissolved in 20 mL of chloroform. The
solution was filtered through a pad of Celite and concen-

S. Ko¨cher et al. / Inorganica Chimica Acta 359 (2006) 4454–4462
4461
3
˚
trated in oil-pump vacuum to 2 mL. n-Hexane (50 mL) was
added, whereby an orange solid precipitated. This precipi-
tate was collected and washed several times with 10 mL of
n-hexane and 10 mL of diethyl ether to gave 12 as an
orange solid. Yield: 40 mg (0.063 mmol, 73% based on
[Pd2(dba)3 Æ CHCl3]).
V = 4181.60(9) A , Z = 8, Dx = 1.925 g cmꢀ3
.
65541
Reflections were measured. An analytical absorption cor-
rection was applied (PLATON [28], routine ABST, l =
7.51 mmꢀ1, 0.14–0.78 correction range). Nine thousand
five hundred and thirty-three reflections were unique
(Rint = 0.059). One cyclopentadienyl ring was refined with
a disorder model using split positions. 540 Parameters
were refined with 154 restraints. R1/wR2 [I P 2r(I)]:
0.0260/0.0583. R1/wR2 [all reflection]: 0.0398/0.0631.
S = 1.062. Residual electron density between ꢀ1.38 and
M.p.: [ꢀC] 106 (dec.). IR (KBr): [cmꢀ1] 2210 (w) [mC„C].
1H NMR (CDCl3): [d] 3.02 (s, 12H, NMe2), 3.96 (s, 4H,
CH2N), 4.22 (bs, 2H, C5H4), 4.22 (bs, 5H, C5H5), 4.46
(pt, JHH = 1.8 Hz, 2H, C5H4), 6.92 (s, 2H, C6H2).
13C{1H} NMR (CDCl3): [d] 54.9 (NCH3), 65.4 (iC/
C5H4), 68.8 (CH/C5H4), 69.9 (CH/C5H5), 71.3 (CH/
C5H4), 77.3 (NCH2), 73.8 (FcC„C), 86.0 (FcC„C),
120.0 (iC/C6H2), 122.7 (CH/C6H2), 128.3 (iC/C6H2),
145.2 (iC/C6H2). Anal. Calc. for C24H27IFeN2Pd (632.65):
C, 45.56; H, 4.30; N, 4.43. Found: C, 45.71; H, 4.38; N,
4.41%.
3
˚
1.40 e/A .
3.15. Compound 13
C24H27ClFeN2Pt, Fw = 629.87, red needle, 0.42 · 0.18 ·
0.04 mm3, monoclinic, P21/c (no. 14), a = 12.223(3),
˚
b = 15.568(2), c = 11.9352(12) A, b = 107.610(11)ꢀ, V =
2164.7(7) A , Z = 4, Dx = 1.933 g cmꢀ3. 22713 Reflections
3
˚
3.12. Synthesis of 13
were measured. An analytical absorption correction was
applied (PLATON [28], routine ABST, l = 7.26 mmꢀ1
,
Compound 13 was prepared according to the procedure
described for 8 by using 100 mg (0.25 mmol) of 5, 0.16 mL
(0.26 mmol, 1.6 M in n-hexane) of nBuLi and 100 mg
(0.22 mmol) of [(Et2S)2PtCl2]. Yield: 75 mg (0.12 mmol,
53% based on 5).
0.34–0.85 correction range). 4943 Reflections were unique
(Rint = 0.06). The crystal appeared to be non-merohedrally
twinned with a twofold rotation about the a-axis as twin
operation. This twin relationship was taken into account
during intensity evaluation [28], data reduction and refine-
ment as HKLF5 twin [29]. 267 Parameters were refined
with no restraints. R1/wR2 [I P 2r(I)]: 0.0362/0.0904. R1/
wR2 [all reflection]: 0.0462/0.0962. S = 1.073. Residual
M.p.: [ꢀC] 105 (dec.). IR (KBr): [cmꢀ1] 2206 (w) [mC„C].
3
1H NMR (CDCl3): [d] 3.08 (s, JPtH = 36.9 Hz, 12H,
3
NMe2), 4.00 (s, JPtH = 46.5 Hz, 4H, CH2N), 4.21 (pt,
3
˚
JHH = 1.8 Hz, 2H, C5H4), 4.22 (s, 5H, C5H5), 4.46 (pt,
JHH = 1.8 Hz, 2H, C5H4), 6.96 (s, 2H, C6H2). 13C{1H}
NMR (CDCl3): [d] 45.3 (NCH3), 63.9 (NCH2), 65.3 (iC/
C5H4), 68.7 (CH/C5H4), 69.9 (CH/C5H5), 71.3 (CH/
C5H4), 85.7 (FcC„C), 88.1 (FcC„C), 123.8 (iC/C6H3),
129.1 (CH/C6H3), 130.7 (CH/C6H3), 138.9 (iC/C6H3).
Anal. Calc. for C24H27ClFeN2Pt (629.86): C, 45.76; H,
4.32; N, 4.45. Found: C, 45.71; H, 4.38; N, 4.41%.
electron density between ꢀ2.51 and 2.20 e/A .
4. Supplementary material
CCDC 284746 (complex 8) and 284747 (13) contain the
supplementary crystallographic data for this paper. These
data can be obtained free of charge from The Cambridge
Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
3.13. X-ray crystal structure determinations
Acknowledgements
X-ray intensities up to a resolution of (sinH/k)max
=
ꢀ1
˚
0.65 A were measured on a Nonius Kappa CCD diffrac-
tometer with a rotating anode and a graphite monochro-
We are grateful to the Deutsche Forschungsgemeins-
chaft (DFG) for financial support. The work of M.L.
and A.L.S. was supported by the Council for Chemical Sci-
ences of the Netherlands Organization for Scientific Rese-
rach (CW-NWO).
˚
mator (k = 0.71073 A) at a temperature of 150(2) K. The
structures were solved with automated Patterson methods
[25] and refined with SHELXL-97 [26] on F2 of all reflections.
Non-hydrogen atoms were refined freely with anisotropic
displacement parameters. Hydrogen atoms were intro-
duced in geometrically idealised positions and refined with
a riding model. Geometry calculations, drawings and
checking for higher symmetry were performed with the
PLATON package [27].
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3.14. Compound 8
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˚
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