Trimetallic FePd2 and FePt2 4-ferrocenyl-NCN pincer complexes

Article abstract of DOI:10.1016/j.jorganchem.2006.05.052

Ferrocene-bridged NCN pincer complexes of structural type Fe(η⁵-C₅H₄-4-NCN-1-MX)₂ (X = I: 6, M = Pd; 7, M = Pt; X = Cl: 8, M = Pt; NCN = [4-C₆H₂(CH₂NMe₂)₂ -2,6]^-) are accessible by the subsequent reaction of Fe(η⁵-C₅H₄-4-NCNH)₂ (4) with ⁿBuLi and [PtCl₂(SEt₂)₂] (synthesis of 8) or treatment of Fe(η⁵-C₅H₄-4-NCN-1-I)₂ (5) with [Pd₂(dba)₃] (synthesis of 6) or [Pt(tol)₂(SEt₂)]₂ (synthesis of 7) (dba = dibenzylidene acetone, tol = 4-tolyl). In addition, the Sonogashira cross-coupling of Fe(η⁵-C₅H₄I)₂ (1) with HC{triple bond, long}C-4-NCNH (2) gives Fe(η⁵-C₅H₄-C{triple bond, long}C-4-NCNH)₂ (3). The reaction behavior of 3 towards ^tBuLi is reported as well. Cyclovoltammetric studies show that the ferrocene entity can be oxidized reversibly. The Fe(II)/Fe(III) potential decreases with increasing electron density at the NCN pincer units due to the presence of the M-halide moiety (M = Pd, Pt). The solid state structure of Fe(η⁵-C₅H₄-4-NCN-1-PdI)₂ (6) is presented. In 6 the Fe(η⁵-C₅H₄)₂ unit connects two NCN-PdI pincer entities with palladium in a square-planar environment. The cyclopentadienyl ligands show a staggered conformation. The C₆H₂ rings are tilted by 23.5(3)° towards the C₅H₄ entities and the C₆H₂ plane is almost coplanar with the PdN₂^ipso CI coordination plane (10.3(3)°).

Full text of DOI:10.1016/j.jorganchem.2006.05.052

Journal of Organometallic Chemistry 691 (2006) 3955–3961
www.elsevier.com/locate/jorganchem
Trimetallic FePd2 and FePt2 4-ferrocenyl-NCN pincer complexes
a
a
a,b
Stefan Kocher , Bernhard Walfort , Gerard P.M. van Klink
¨
,
Gerard van Koten a,b, Heinrich Lang
a,
*
a
Technische Universita¨t Chemnitz, Fakulta¨t fu¨r Naturwissenschaften, Institut fu¨r Chemie, Lehrstuhl Anorganische Chemie,
Straße der Nationen 62, 09111 Chemnitz, Germany
b
Debye Institute, Organic Synthesis and Catalysis, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
Received 14 March 2006; received in revised form 18 May 2006; accepted 24 May 2006
Available online 10 June 2006
Abstract
Ferrocene-bridged NCN pincer complexes of structural type Fe(g5-C5H4-4-NCN-1-MX)2 (X = I: 6, M = Pd; 7, M = Pt; X = Cl: 8,
n
M = Pt; NCN = [4-C6H2(CH2NMe2)2-2,6]ꢀ) are accessible by the subsequent reaction of Fe(g5-C5H4-4-NCNH)2 (4) with BuLi and
[PtCl2(SEt2)2] (synthesis of 8) or treatment of Fe(g5-C5H4-4-NCN-1-I)2 (5) with [Pd2(dba)3] (synthesis of 6) or [Pt(tol)2(SEt2)]2 (synthesis
of 7) (dba = dibenzylidene acetone, tol = 4-tolyl). In addition, the Sonogashira cross-coupling of Fe(g5-C5H4I)2 (1) with HC„C-4-
t
NCNH (2) gives Fe(g5-C5H4-C„C-4-NCNH)2 (3). The reaction behavior of 3 towards BuLi is reported as well.
Cyclovoltammetric studies show that the ferrocene entity can be oxidized reversibly. The Fe(II)/Fe(III) potential decreases with
increasing electron density at the NCN pincer units due to the presence of the M-halide moiety (M = Pd, Pt).
The solid state structure of Fe(g5-C5H4-4-NCN-1-PdI)2 (6) is presented. In 6 the Fe(g5-C5H4)2 unit connects two NCN-PdI pincer
entities with palladium in a square-planar environment. The cyclopentadienyl ligands show a staggered conformation. The C6H2 rings
are tilted by 23.5(3)ꢀ towards the C5H4 entities and the C6H2 plane is almost coplanar with the PdN2ipsoCI coordination plane (10.3(3)ꢀ).
ꢁ 2006 Elsevier B.V. All rights reserved.
Keywords: NCN Pincer; Ferrocene; Palladium; Platinum; Cyclicvoltammetry; Solid state structure
1. Introduction
blies, since it can act as an one-electron reservoir and at
the same time is a very robust compound [4,5].
Recently, the synthesis and reaction chemistry of multi-
metallic transition metal complexes in which different met-
als are connected by inorganic and/or organic p-conjugated
bridging units have been reported [1–6]. Such species are of
special interest, due to their potential use as, for example,
one-dimensional molecular wires [6]. Moreover, they are
promising candidates to be used as catalysts or as optical
and physical sensors. Among them, transition metal com-
plexes featuring redox-active metals are most attractive,
because both their electron density and electronic proper-
ties are easily switchable. Ferrocene is a most promising
candidate to be incorporated in such multimetallic assem-
Recently, the synthesis and reaction chemistry of 1,10-
bis-NCN pincer-functionalized ferrocenes of general type
Fe(g5-C5H4-4-NCN-1-X)2
(NCN = [C6H2(CH2NMe2)2-
2,6]ꢀ; X = H, PdCl) were preliminary reported [4,5]. We
here report on the preparation, structural features and elec-
trochemical behavior of trimetallic FePd2 and FePt2 com-
plexes of type Fe(g5-C5H4-4-NCN-1-MX)2 (MX = PdI,
PtCl, PtI).
2. Results and discussion
2.1. Synthesis and spectroscopy
Palladium-catalyzed cross-coupling is an efficient syn-
thetic method to prepare organic and organometallic com-
pounds with p-conjugated bridging units [7]. In this
*
Corresponding author. Tel.: +49 371 531 1673; fax: +49 371 531 1833.
E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang).
0022-328X/$ - see front matter ꢁ 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2006.05.052

3956
S. Ko¨cher et al. / Journal of Organometallic Chemistry 691 (2006) 3955–3961
respect, the synthesis of the 1,1’-bis-NCNH pincer-func-
tionalized ferrocenes Fe(g5-C5H4C„C-NCNH)2 (3) and
Fe(g5-C5H4-NCNH)2 (4) (NCNH = 1-C6H3(CH2NMe2)2-
3,5), respectively, is discussed (for details in the preparation
of 4 see Ref. [5]). Following the Sonogashira cross-coupling
protocol [2d], 3 is accessible by heating Fe(g5-C5H4I)2 (1)
with two equivalents of HC„C-1-C6H3(CH2NMe2)2-3,5
(2) in presence of catalytic amounts of [(Ph3P)2PdCl2/
CuI] and diisopropylamine as solvent (Eq. (1)). After
appropriate work-up, complex 3 could be isolated in 9%
yield as a red–brown oil.
18 h at 25 ꢀC. After appropriate work-up, orange colored
Fe(g5-C5H4-4-NCN-1-PdI)2 (6) was isolated in 68% yield
(Eq. (3)). Isostructural Fe(g5-C5H4-4-NCN-1-PtI)2 (7) is
accessible by refluxing 5 with stoichiometric amounts of
[Pt(tol)2(SEt2)]2 (tol = 4-tolyl) in toluene for 5 min (Eq.
(3)). On addition of n-hexane to the reaction mixture, com-
plex 7 precipitates as an orange solid.
NMe2
I
Me2N
Fe
NMe2
NMe2
I
I
Fe
H
2
+
Me2N
5
I
NMe2
ð3Þ
NMe2
1
2
M
I
NMe2
NMe2
[Pd2dba3•CHCl3] or
[Pt(tol)2(SEt2)]2
ð1Þ
Me2N
Fe
NMe2
[Pd / Cu]
I
M
Me2N
Me2N
Fe
iPr2NH, 6 h reflux
Me2N
6: M = Pd
7: M = Pt
3
Trimetallics 6 and 7 can also be obtained, when 4 is sub-
sequently reacted with BuLi, I2 and either [Pd2(dba)3] or
n
The standard procedure involving lithiation-transmetal-
lation for the synthesis of palladium- and platinum-NCN
pincers [8], however, could not be applied for the prepara-
tion of Fe(g5-C5H4-C„C-4-NCN-1-MX)2 (M = Pd, Pt;
X = Cl, Br), since lithiation of 3 by either BuLi or BuLi
appears not possible. A similar behavior has been observed
for the metallation of the biferrocene [Fe(g5-C5H4)(g5-
C5H4-C„C-NCNH)]2 [3,9]. This shows that other, com-
petitive reactions occur.
[Pt(tol)2(SEt2)2] (6: 58%, 7: 48%).
Attempts to prepare FePd and FePt complexes or even
heterotrimetallic FePdPt species by the stepwise insertion
of the appropriate transition metals into the Caryl–I bond(s)
in 5, however, did always result in the formation of 1:1
mixtures of 5 and 6, and 5 and 7, respectively. This clearly
shows that the presence of a palladium or platinum atom in
Fe(g5-C5H4-NCN-I)(g5-C5H4-NCN-MI) (M = Pd, Pt) sig-
nificantly activates the C–I bond towards the second oxida-
tive addition.
n
t
In contrast, lithiation of Fe(g5-C5H4-NCNH)2 (4) is
n
possible by addition of two equivalents of BuLi to this
compound. Dilithiated Fe(g5-C5H4-4-NCN-1-Li)2 (4 Æ Li)
reacts with diiodine to form the orange colored sandwich
complex Fe(g5-C5H4-4-NCN-1-I)2 (5) which was isolated
in 86% yield (Eq. (2)).
As reported previously, trimetallic Fe(g5-C5H4-4-NCN-
1-PdCl)2 can be prepared from 4 by a lithiation-transmetal-
lation sequence [1]. In a similar manner, orange–brown
colored Fe(g5-C5H4-4-NCN-1-PtCl)2 (8) appeared accessible
bythe subsequent reaction of 4 with nBuLi and [PtCl2(SEt2)2]
and was isolated in an overall yield of 15% (Eq. (4)).
NMe2
NMe2
Me2N
Me2N
Fe
NMe2
Me2N
Me2N
Fe
NMe2
4
ð2Þ
NMe2
I
4
ð4Þ
NMe2
Pt Cl
NMe2
1. 2 nBuLi
2. 2 I2
Me2N
Fe
NMe2
1. 2 nBuLi
Me2N
Fe
I
2. 2 [PtCl2(SEt2)2]
Cl Pt
Me2N
Me2N
5
8
Oxidative addition of the C–I bond in 5 to palladium(0)
is possible by reacting 5 with [Pd2(dba)3 Æ CHCl3] (dba =
dibenzylidene acetone) in a 1:1 molar ratio in benzene for
Complexes 3 and 5–8 were characterized by elemental
1
analysis, H and 13C{1H} NMR spectroscopy.

S. Ko¨cher et al. / Journal of Organometallic Chemistry 691 (2006) 3955–3961
3957
1
Table 1
The H NMR spectra of 3 and 5 reveal the resonance
pattern typical for non-metallated pincer complexes
[5,8b,10]. The CH2 and NMe2 protons appear as singlets
at 3.45 and 2.28 ppm for 3 and at 3.26 and 2.12 ppm for
5. The coordination of the Me2NCH2 nitrogen atoms to
either a Pd(II) (6) or Pt(II) ion (7, 8) results in a significant
low-field shift of the CH2 (6: 4.03, 7: 4.08, and 8: 4.05 ppm)
and NMe2 signals (6: 3.08, 7: 3.25, and 8: 3.13 ppm). Due
to the increased electron density at the benzene ring a
high-field shift of the aromatic protons from 7.01 (5) to
ca. 6.8 ppm (6–8) is observed. For 7 and 8 typical 195Pt sat-
ellites were found with coupling constants of ca. 36
(3JPtH(Me)) and 42 Hz (3JPtH(CH2)), respectively.
Electrochemical data of 4–8
Compound
E1/2 (V)
DE (mV)
Eox (V)
Fe(C5H4-NCN-H)2 (4)a
Fe(C5H4-NCNH)2 (4)b
Fe(C5H4-NCN-I)2 (5)b
Fe(C5H4-NCN-PdI)2 (6)b
Fe(C5H4-NCN-PtI)2 (7)b
Fe(C5H4-NCN-PtCl)2 (8)a
+0.03
+0.01
+0.04
ꢀ0.09
ꢀ0.16
ꢀ0.06
80
80
131
96
106
180
+0.76
+0.73
+0.75
+0.30
n. obs.c
+0.70
a
In acetonitrile.
In tetrahydrofuran.
n. obs. = not observed.
b
c
Complexes 4–8 show reversible waves for the Fe(II)/
Fe(III) redox couples (Fig. 1, Table 1).
Upon complexation of the Me2NCH2 unit to M a char-
acteristic downfield shift is observed in the 13C{1H} NMR
spectra (i.e. 5: 68.9 (NCH2), 45.4 ppm (NCH3) vs. 6: 74.1
and 55.0 ppm, respectively) (Experimental part).
The Fe(II)/Fe(III) potentials in monometallic 4 and 5
are as compared to the Cp2Fe/Cp2Fe+ redox couple
(FeCp2 = Fe(g5-C5H5)2), shifted to a more positive value,
which can be explained by the presence of the somewhat
stronger electron withdrawing NCN groups in 4 and 5
rather then in ferrocene which has been taken as standard
[5,11].
2.2. Electrochemical studies
Cyclovoltammetric studies were carried out for 8 in ace-
tonitrile and for 6 and 7 in tetrahydrofuran solutions at
25 ꢀC. For comparison, also 4 and 5 were subjected to
cyclovoltammetric measurements. Exemplary, the cyclic
voltammograms of 5 and 6 are depicted in Fig. 1.
Upon complexation of the NCN pincer unit to either
palladium or platinum (6–8) the energy of the Fe(II)/
Fe(III) couple is shifted to a more negative value (Table
1). In this respect, complex 6 shows a reversible wave at
ꢀ0.09 V (DE = 96 mV) which is shifted by ꢀ130 mV as
compared to 5 (Table 1). This confirms that the Fe(II)
ion in 6 is somewhat easier to oxidize which is most likely
caused by the ortho-metallation of the NCN pincer moiety
(neutral vs. anionic NCN). An even more negative poten-
tial is found for 7 (E1/2 = ꢀ 0.16 V, DE = 106 mV) (Table
1). Although, these studies were performed in tetrahydro-
furan solutions, a similar behavior is found, when the mea-
surements were carried out in acetonitrile (Table 1). The
difference in the redox potentials for 4 and 8 is with
ꢀ90 mV somewhat smaller as compared to measurements
done in tetrahydrofuran (vide supra). The irreversible ani-
odic wave results from the oxidation of the NCN pincer
units [5]. An analogues behavior has been reported for ben-
zyl amine [12].
60
50
40
30
20
10
0
-10
-20
1
-0.6
-0.4
-0.2
0
0.2
E[V]
0.4
0.6
0.8
1.2
12
10
8
2.3. Solid state structure of 6
6
Single crystals of 6 suitable for X-ray structure analysis
could be obtained by slow distillation of n-hexane into a
dichloromethane–chloroform mixture (ratio 1:1) contain-
ing 6 at ꢀ30 ꢀC. The molecular structure of 6 is shown in
Fig. 2. Geometric details are listed in Table 2 and experi-
mental crystal data in Table 3 (Experimental part).
Complex 6 crystallizes in the monoclinic space group
P21/c. The asymmetric unit contains half of the molecule
with the second part generated by ꢀx + 1, ꢀy + 1, and
ꢀz + 1. The main geometric features of 6 resemble the
structural data characteristic for ferrocene and NCN pin-
cer complexes [8,10]. The Fe1 atom is located at an inver-
sion center in crystals of 6 and gives rise to a rotation of
4
2
0
-2
-4
-6
-8
-1
-0.8
-0.6
-0.4
-0.2
E[V]
0
0.2
0.4
0.6
0.8
Fig. 1. Cyclicvoltammogramms of 5 (top) and 6 (bottom) in tetrahydro-
furan in the presence of [n-Bu4N][PF6] (c = 0.10 M), 25 ꢀC, argon, scan
rate = 200 mV sꢀ1. All potentials are referenced to the Cp2Fe/Cp2Fe+
redox couple as standard (Cp2Fe = (g5-C5H5)2Fe, E1/2 = 0.00 V).

3958
S. Ko¨cher et al. / Journal of Organometallic Chemistry 691 (2006) 3955–3961
Fig. 2. POV-Ray plot (50% probability level) of 6 with the molecular geometry and atom numbering scheme. The hydrogen atoms, the chloroform and
dichloromethane molecules have been omitted for clarity.
Table 2
a
˚
Selected bond distances (A), angles (ꢀ), and torsion angels (ꢀ) for 6
Bond lengths
Bond angles
Torsion angles
Pd1–I1
Pd1–C9
Pd1–N1
Pd1–N2
Fe1–D1b
a
2.733(1)
1.929(6)
2.117(5)
2.126(5)
1.661(1)
I1–Pd1–C9
N1–Pd1–N2
N1–Pd1–I1
N2–Pd1–I1
C1–C13–N3
117.0(2)
162.5(2)
98.2(1)
99.3(1)
178.4(6)
C9–C8–C12–N1
C9–C10–C15–N2
Pd1–N1–C12–C8
Pd1–N2–C15–C10
21.1(7)
22.8(8)
ꢀ26.3(6)
ꢀ28.1(6)
Standard deviations are given as the last significant figure(s) in parenthesis.
D1: centroid of the cyclopentadienyl ligands.
b
the two cyclopentadienyl ligands of the ferrocene moiety by
180 ꢀ resulting in a staggered conformation. With the two
NCN-PdI moieties pointing in opposite directions, no
(p-)stacking of the C6H2 rings (C6–C11) was found either
intra- or intermolecular as it has been observed for other
1,10-bis-aryl- or 1,10-bis-ethynylaryl-substituted ferrocenes
[13]. A possible intermolecular interaction of the p-systems
is further restricted, because of solvent molecules (dichloro-
methane and chloroform) incorporated in the crystal, sep-
arating single molecules of 6.
3. Experimental section
3.1. General methods
All reactions were carried out under an atmosphere of
purified nitrogen using standard Schlenk techniques. Tet-
rahydrofuran, diethyl ether, benzene, toluene, and n-hex-
ane were purified by distillation from sodium/
benzophenone ketyl. Diisopropylamine was dried by dis-
tillation from KOH. Infrared spectra were recorded with
a Perkin Elmer FT-IR 1000 spectrometer. NMR spectra
were recorded with a Bruker Avance 250 spectrometer
(1H NMR at 250.12 MHz and 13C{1H} NMR at
62.86 MHz) and a Varian Inova 300 spectrometer (1H
NMR at 300.10 MHz and 13C{1H} NMR at 75.47 MHz)
in the Fourier transform mode. Chemical shifts are
reported in d units (parts per million) downfield from tet-
ramethylsilane (d = 0.00 ppm) with the solvent as the ref-
The plane spanned by the C6H2 entity is tilted by
23.5(3)ꢀ towards the g5-coordinated C5H4 group. In the
solid state structure this orientation averts an optimal over-
lap between the p-orbitals of the cyclopentadienyl and the
NCN-PdI pincer fragments [14]. However, in solution the
NCN pincer and cyclopentadienyl rings are free to rotate
(vide supra).
Furthermore, the d8-configurated Pd(II) ions are, as
expected, coordinated in a slightly distorted square-planar
fashion by the two nitrogen atoms N1 and N2, the NCN
1
erence signal (CDCl3: H NMR, d = 7.26; 13C{1H} NMR,
d = 77.0). Cyclicvoltammograms were recorded in a dried
cell purged with purified argon at 25 ꢀC. Platinum wires
served as working electrode and as counter electrode. A
Ag/AgCl (or saturated calomel) electrode served as refer-
ence electrode. For ease of comparison, all potentials are
converted using the redox potential of the ferrocene–ferr-
Cipso carbon atom C9 and the iodine ligand I1. The coordi-
nation plane around Pd1 is almost coplanar with the plane
of the C6H2 ring (10.3(3)ꢀ). The C9–Pd1–I1 bond angle is
with 177.0(2)ꢀ linear, while N1–Pd1–N2 is with 162.5(2)ꢀ
deformed from linearity.

S. Ko¨cher et al. / Journal of Organometallic Chemistry 691 (2006) 3955–3961
3959
Table 3
Crystal and intensity collection data for 6
3.2. General remarks
Fe(g5-C5H4I)2 (1) [17], HC„C-1-C6H3(CH2NMe2)2-3,5
(2) [18], Fe(g5-C5H4-NCNH)2 (4) [5], [PtCl2(SEt2)2] [19],
[Pd2(dba)3 Æ CHCl3] [20], and [Pt(4-tol)2(SEt2)]2 [21] were
prepared following published procedures. All other chemi-
cals are commercially available and were used as received.
Empirical formula
Chemical formula
Formula weight
Crystal system
Space group
C37.5H49Cl9FeI2N4Pd2
C34H44FeI2N4Pd2
1397.31
Monoclinic
P21/c
6.0803(3)
32.5876(15)
12.5281(6)
2431.9(2)
101.574(1)
1.908
1358
˚
a (A)
˚
b (A)
˚
c (A)
3.2.1. Synthesis of 3
3
˚
V (A )
Compound
(4.44 mmol) of 2 were dissolved in 30 mL of diisopropyl-
amine and 124 mg (0.18 mmol, 4.0 mol%) of
1
(920 mg, 2.10 mmol) and 960 mg
b (ꢀ)
qcalc (g cmꢀ3
)
F(000)
Z
2
[PdCl2(Ph3P)2] and 33 mg (0.18 mmol, 4 mol%) of [Cu(OA-
c)2 Æ H2O] were added. After heating the reaction mixture
for 6 h to reflux all volatiles were removed (oil-pump
vacuum). The reddish-brown solid was dissolved in
100 mL of diethyl ether and filtered through a pad of Silica
gel (7 · 5 cm). With diethyl ether as eluent, 320 mg (0.73
mmol, 35% based on 1) of 1 could be recovered. With tet-
rahydrofuran complex 3 was obtained as a red–brown oil.
For further purification, 3 was dissolved in 100 mL of
diethyl ether and this solution was extracted with 100 mL
of water containing 5 mL of 4 M HCl. The aqueous phase
was then separated, treated with 30 mL of 1 M NaOH and
extracted twice with 100 mL of diethyl ether. The combined
organic phases were dried over MgSO4, filtered and all vol-
atiles were evaporated in oil-pump vacuum. Yield: 120 mg
(0.20 mmol, 9% based on 1).
Crystal dimensions (mm)
Radiation (k, A)
Absorption correction
Maximum, minimum transmission
Absorption coefficient (l, mmꢀ1
Temperature (K)
Scan range (ꢀ)
Index ranges
Total reflections
Unique reflections
Observed reflections [I P 2r(I)]
Refinement method
Refined parameters
Restraints
Completeness to hmax
R1, wR2 [I P 2r(I)]
R1, wR2 (all data)
Rint, S
0.2 · 0.1 · 0.1
Mo-Ka (0.71073)
Semi-empirical from equivalents
0.99999, 0.65934
2.822
193(2)
˚
)
1.77 6 H 6 26.43
ꢀ7 6 h 6 7, 0 6 k 6 40, 0 6 l 6 15
20,931
5102
4990
Full-matrix, least-squares (F2)
263
16
99.7%
0.0479, 0.1173a
0.0590, 0.1222b
0.0395, 1.046
1
IR (NaCl): (cmꢀ1) 2221 (s) (mC„C). H NMR (CDCl3):
Maximum, minimum peaks in final 1.554, ꢀ1.199
ꢀ3
˚
Fourier map (e A
)
[d] 2.28 (s, 24H, NMe2), 3.45 (s, 8H, CH2N), 4.24 (pt,
JHH = 1.8 Hz, 4H, C5H4), 4.45 (pt, JHH = 1.8 Hz, 4H,
C5H4), 7.25 (s, 2H, C6H3), 7.39 (s, 4H, C6H3). 13C{1H}
NMR (CDCl3): [d] 45.3 (NCH3), 63.9 (NCH2), 67.5 (iC/
C5H4), 70.9 (CH/C5H4), 72.1 (CH/C5H4), 86.7 (FcC„C),
86.9 (FcC„C), 123.3 (iC/C6H3), 129.1 (CH/C6H3), 130.5
(CH/C6H3), 138.9 (iC/C6H3). Anal. Calc. for C38H46FeN4
(614.63): C, 74.23; H, 7.55; N, 9.12. found: C, 73.95; H,
7.65; N, 8.98.
P
jjF ojꢀjF cjj
a
P
R1 ¼
.
jF o
j
rffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
P
2
wðF 2oꢀF 2c
Þ
ðmaxðF 2o;0Þþ2F 2c
Þ
.
b
1
P
wR2 ¼
with w ¼
; P ¼
2
2
wðF 2o
Þ
r2ðF 2oÞþðg1PÞ þg2P
3
ocenium couple Cp2Fe/Cp2Fe+ (Cp2Fe = (g5-C5H5)2Fe)
as the reference (E1/2 = 0.00 V) [15]. A conversion of the
given data to the standard normal hydrogen electrode is
possible following the suggestion made by Strehlow
et al. [16]. Electrolyte solutions were prepared from freshly
distilled acetonitrile or tetrahydrofuran solutions and [n-
Bu4N]PF6 (dried in oil-pump vacuum at 120 ꢀC,
c = 0.1 M). The appropriate organometallic complexes
were added at c = 1 mM. Cyclicvoltammograms were
recorded at a scan rate of 200 mV sꢀ1 using a Princeton
Applied Research EG&G 263A analyzer or a Radiometer
Copenhagen DEA 101 Digital Electrochemical analyzer
with an IMT 102 Electrochemical Interface. Melting
points were determined using sealed nitrogen purged cap-
illaries on a Gallenkamp MFB 595 010 M melting point
apparatus. Microanalyses were performed by the Dornis
3.2.2. Synthesis of 5
Complex 4 (170 mg, 0.21 mmol) was dissolved in 50 mL
n
of n-hexane and 0.5 mL (0.8 mmol) of BuLi (1.6 M in n-
hexane) were added at 25 ꢀC. After stirring for 16 h at this
temperature all volatiles were removed in oil-pump vacuum.
The orange residue was dissolved in 50 mL of diethyl ether
and 300 mg (1.18 mmol) of I2 were added at 0 ꢀC. The reac-
tion mixture was stirred upon warming to 25 ꢀC for 8 h and
quenched with 1.0 g of Na2S2O3 dissolved in 50 mL of
water. The organic phase was separated, extracted with
50 mL of water, dried over MgSO4, filtered and evaporated
in oil-pump vacuum to gave 5 as an orange solid. Yield:
220 mg (0.27 mmol, 86% based on 4).
M.p.: [ꢀC] 139. 1H NMR (CDCl3): [d] 2.12 (s, 24H,
NMe2), 3.26 (s, 8H, CH2N), 3.82 (pt, JHH = 1.8 Hz, 4H,
C5H4), 4.35 (pt, JHH = 1.8 Hz, 4H, C5H4), 7.01 (s, 4H,
C6H2). 13C{1H} NMR (CDCl3): [d] 45.4 (NCH3), 67.8
(CH/C5H4), 68.9 (NCH2), 70.7 (CH/C5H4), 84.8 (iC/
und Kolbe, Mikroanalytisches Laboratorium, Mulheim
¨
a.d. Ruhr and by the Department of Organic Chemistry
at Chemnitz, University of Technology.

3960
S. Ko¨cher et al. / Journal of Organometallic Chemistry 691 (2006) 3955–3961
C5H4), 104.0 (iC-I/C6H2), 126.3 (CH/C6H2), 137.4 (iC/
C6H2), 141.3 (iC/C6H2). Anal. Calc. for C34H44FeI2N4
(818.39): C, 49.90; H, 5.42; N, 6.85. found: C, 50.26; H,
5.71; N, 6.36.
solved in 30 mL of diethyl ether and 170 mg (0.38 mmol)
of [PtCl2(Et2S)2] were added at 0 ꢀC. The reaction mixture
was stirred upon warming to 25 ꢀC over night. All volatiles
were removed in oil-pump vacuum. The dark brown residue
was dissolved in 20 mL of dichloromethane and filtered
through a pad of Celite. All volatiles were removed in
oil-pump vacuum to gave 8 as an orange–brown solid
(30 mg, 0.03 mmol, 15% based on [PtCl2(Et2S)2]).
3.2.3. Synthesis of 6
Compound
5 (100 mg, 0.122 mmol) and 125 mg
(0.121 mmol) of [Pd2(dba)3 Æ CHCl3] were dissolved in
15 mL of benzene and were stirred for 18 h at 25 ꢀC. After-
wards, 20 mL of tetrahydrofuran were added and the reac-
tion mixture was stirred for 4 h. All volatiles were removed
(oil-pump vacuum) and the remaining greenish-black solid
was dissolved in 30 mL of chloroform. The solution was fil-
tered through a pad of Celite and concentrated to 3 mL
(oil-pump vacuum). n-Hexane (30 mL) was then added,
whereby an orange solid precipitated. The precipitate was
collected and washed three times with n-hexane (10 mL)
and diethyl ether (10 mL) to gave 6 as an orange solid
(85 mg, 0.082 mmol, 68% based on [Pd2dba3 Æ CHCl3]).
M.p.: [ꢀC] 168 (dec). 1H NMR (CDCl3): [d] 3.08 (s, 24H,
NMe2), 4.03 (s, 8H, CH2N), 4.12 (pt, JHH = 1.8 Hz, 4H,
C5H4), 4.41 (pt, JHH = 1.8 Hz, 4H, C5H4), 6.78 (s, 4H,
C6H2). 13C{1H} NMR (CDCl3): [d] 55.0 (NCH3), 67.3
(CH/C5H4), 70.9 (CH/C5H4), 74.1 (NCH2), 86.7 (iC/
C5H4), 117.7 (CH/C6H2), 135.2 (iC/C6H2), 145.0 (iC/
C6H2), 149.5 (iC/C6H2). Anal. Calc. for C34H44FeI2N4Pd2
(1031.23): C, 39.60; H, 4.30; N, 5.43. Found: C, 39.68; H,
4.67; N, 5.50.
M.p.: [ꢀC] 175. 1H NMR (CDCl3): [d] 3.13 (s,
3
3JPtH = 34.4 Hz, 24H, NMe2), 4.05 (s, JPtH = 41.0 Hz,
8H, CH2N), 4.12 (pt, JHH = 1.8 Hz, 4H, C5H4), 4.41 (pt,
JHH = 1.8 Hz, 4H, C5H4), 6.80 (s, 4H, C6H2). 13C{1H}
NMR (CDCl3): [d] 55.0 (NCH3), 67.3 (CH/C5H4), 70.9
(CH/C5H4), 74.1 (NCH2), 86.7 (iC/C5H4), 117.7 (CH/
C6H2), 135.2 (iC/C6H2), 145.0 (iC/C6H2), 149.5 (iC/
C6H2). Anal. Calc. for C34H44Cl2FeN4Pt2 (1025.65): C,
39.81; H, 4.32; N, 5.46. Found: C, 40.25; H, 4.51; N, 5.18.
4. X-ray structure determination of 6
X-ray structure analysis measurements were performed
with a BRUKER SMART CCD 1 k diffractometer at
193 K using oil-coated shock-cooled crystals [22]. Reflec-
tions were collected in the x-scan mode in 0.4ꢀ steps and
an exposion time of 40 s per frame. The structure was
solved by direct methods using SHELXS-97 [23] and refined
by full-matrix least-square procedures on F2 using
SHELXL-97 [24]. All non-hydrogen atoms were refined aniso-
tropically. All hydrogen atom positions were refined using
a riding model. The dichloromethane molecule nearby the
inversion centre is not fully present and has been refined to
an occupancy of 0.77, while fixed to 0.75 at the end of the
refinement. The structure plot was performed with POV-
Ray [25]. The figures in parenthesis after each calculated
value represent the standard deviation in units of the last
significant digit(s).
3.2.4. Synthesis of 7
5
Compound
(50 mg, 0.061 mmol) and 55 mg
(0.059 mmol) of [Pt(tol)2(SEt2)]2 were refluxed in 15 mL
of toluene for 5 min. The orange solution was cooled to
25 ꢀC, filtered through a pad of Celite and concentrated
in oil-pump vacuum to 5 mL. Upon addition of 20 mL of
n-hexane an orange precipitate formed, which was col-
lected, washed twice with n-hexane (10 mL) and diethyl
ether (10 mL) and dried in oil-pump vacuum to afford
40 mg (0.033 mmol, 56% based on [Pt(tol)2(SEt2)]2) of 7
as an orange solid.
5. Supplementary material
The crystallographic data for 6 have been deposited with
the Cambridge Crystallographic Data Centre as supple-
mentary publication no. CCDC-612578. Copies of this
information can be obtained free of charge on application
to CCDC, 12 Union Road, Cambridge CB2 1ET, UK.
[Fax: +44 1223 336033, e-mail: deposit@ccdc.cam.ac.uk].
M.p.: [ꢀC] 181. 1H NMR (CDCl3): [d] 3.25 (s,
3
3JPtH = 36.4 Hz, 24H, NMe2), 4.08 (s, JPtH = 41.7 Hz,
8H, CH2N), 4.14 (pt, JHH = 1.8 Hz, 4H, C5H4), 4.43 (pt,
JHH = 1.8 Hz, 4H, C5H4), 6.76 (s, 4H, C6H2). 13C{1H}
NMR (CDCl3): [d] 56.5 (NCH3), 66.9 (CH/C5H4), 70.3
(CH/C5H4), 76.9 (NCH2), 87.7 (iC/C5H4), 117.3 (CH/
C6H2), 133.4 (iC/C6H2), 143.3 (iC/C6H2), 147.7 (iC/
C6H2). Anal. Calc. for C34H44Fe2I2N4Pt2 Æ 2tol (1448.67):
C, 39.80; H, 4.17; N, 3.87. Found: C, 40.40; H, 3.91; N,
3.39.
Acknowledgement
We are grateful to the Deutsche Forschungsgemeins-
chaft (DFG) for financial support.
3.2.5. Synthesis of 8
Complex 4 (110 mg, 0.19 mmol) was dissolved in 30 mL
of n-hexane and 0.24 mL (0.38 mmol) of nBuLi (1.6 M in n-
hexane) were added at 25 ꢀC. After this reaction mixture
was stirred for 18 h at this temperature all volatiles were
removed (oil-pump vacuum). The orange residue was dis-
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