Iron complexes of terdentate nitrogen ligands: Formation and X-ray structure of three new dicationic complexes

Article abstract of DOI:10.1016/j.poly.2004.10.001

The synthesis and X-ray structure of the iron complexes (L1)2Fe2+(FeCl4-)2,(L2)2Fe2+FeCl42-and(L2)2Fe2+(FeCl4-)2(THF)4 (L¹ = 6,6″-di(p-tolyl)-2,2′:6′,2″-terpyridine and L ² = 2,6-bis-(3-mesitylpyrazol-1-yl)pyridine) are presented. (L

Full text of DOI:10.1016/j.poly.2004.10.001

Polyhedron 23 (2004) 3193–3199
www.elsevier.com/locate/poly
Iron complexes of terdentate nitrogen ligands: formation and
X-ray structure of three new dicationic complexes
a,
b
c
c
F. Pelascini a,b, Manuel Wesolek *, F. Peruch , A. De Cian , N. Kyritsakas ,
b
P.J. Lutz , J. Kress
a,z
a
´ ´
Laboratoire de Chimie des Metaux de Transition et de Catalyse (UMR CNRS 7513), Institut Le Bel, Universite Louis Pasteur,
4, rue Blaise Pascal, 67070 Strasbourg Cedex, France
b
Institut Charles Sadron (UPR CNRS 22), 6, rue Boussingault, BP 40016, 67083 Strasbourg Cedex, France
´
Laboratoire de Cristallochimie et de Chimie Structurale (UMR CNRS 7513), Institut Le Bel, Universite Louis Pasteur,
c
4, rue Blaise Pascal, 67070 Strasbourg Cedex, France
Received 14 November 2003; accepted 11 October 2004
Available online 6 November 2004
This work, carried out with Dr. Jacky Kress, Director of Research at the CNRS, who passed away on January 12th, 2003, is dedicated to his memory.
We deeply regret our friend and a scientist of great value
Abstract
Dicationic iron complexes were obtained upon complexation of the ligands 6,600-di(p-tolyl)-2,20:60,200-terpyridine (L1) or 2,6-bis-
(3-mesitylpyrazol-1-yl)pyridine (L2) with iron dichloride or iron trichloride. They were characterized by X-ray diffraction and FT-IR
2
spectroscopy. Single crystal structure determinations of ðL1Þ Fe2þðFeCl4ꢀÞ , ðL Þ Fe2þFeCl4 and ðL2Þ Fe2þðFeCl4ꢀÞ ðTHFÞ all
2ꢀ
2
2
2
2
2
4
show six-coordinate metal center. These complexes were obtained from L1FeCl2 and L2FeCl2 during recrystallization attempts.
(L1)2Fe2+ was shown to be a high-spin complex, whereas (L2)2Fe2+ was shown to be low-spin. For ðL2Þ Fe2þFeCl42ꢀ, two independ-
2
ent dications of very similar geometry but with distinctive distortion were observed by X-ray analysis.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Keywords: Terpyridine; Pyridyl bispyrazolyl; Iron; Complexation; Rearrangement; X-ray structures
1. Introduction
context, we describe here our studies on the coordina-
tion of two N3 donor ligands to iron.
It has been shown recently that binding 2,6-bis(imi-
no)-pyridyl ligands to iron chlorides leads to five-coordi-
nate complexes that behave as highly efficient catalysts
for the polymerization and oligomerization of ethylene,
in the presence of a suitable activator [1]. However, sub-
sequent searches for further terdentate ligands inducing
similar properties revealed much less positive [2]. In this
2. Results and discussion
The ligand 6,600-di(p-tolyl)-2,20:60,200-terpyridine (L1,
Scheme 1) was best synthesized by a variation of the
Kro¨hnke methodology [3]. Instead of the classical Man-
ich salt, the neutral diamine 2,6-bis(3-dimethylamino-1-
oxopropyl-2-ene)pyridine was first obtained in good
yield from the reaction of 2,6-diacetylpyridine with
two equiv. of N,N-dimethylformamide dimethyl acetal
in DMF [4]. It was then reacted with two equiv. of the
*
Corresponding author. Tel.: +33390241339; fax: +33390241329.
E-mail address: wesolek@chimie.u-strasbg.fr (M. Wesolek).
z
Deceased.
0277-5387/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.10.001

3194
F. Pelascini et al. / Polyhedron 23 (2004) 3193–3199
(mFe–Cl = 304 cmꢀ1) are consistent with the formulation
L1FeCl2. Attempts to recrystallize this powder from
warm THF under an inert atmosphere did lead to violet
crystals with the same infrared spectrum than the start-
ing material (mFe–Cl = 304 cmꢀ1) formed just over the
solution and an orange microcrystalline complex in the
solution. The two different crystals were however unsuit-
able for X-ray analysis. The orange microcrystalline
complex seems to result in fact from the conversion of
the violet one, and its formation looks reversible. It gives
rise to two mFe–Cl absorptions at 326 and 307 cmꢀ1, as
well as additional bands assignable to bound THF
(mC–O = 1028 cmꢀ1), and corresponds probably to the
THF adduct L1FeCl2(THF). In an attempt to obtain
better crystals for an X-ray investigation, we heated
the orange microcrystalline complex in THF over a
longer period of time and at higher temperatures. Thus
bigger orange crystals were obtained with other prod-
ucts. The strong IR absorption at 378 cmꢀ1, character-
N
N
N
N
N
N
N
N
L1
L2
Scheme 1. Ligands examined in this study.
potassium salt of p-Me-acetophenone in THF, before
addition of ammonium acetate and acetic acid, suitable
work-up and recrystallisation from dichloromethane/
hexane afforded the product as an off-white powder
(Scheme 2).
Reaction of L1 with FeCl2 in THF at room tempera-
ture yielded an almost insoluble grey-purple powder
whose elemental analysis and infrared spectrum
OCH3
Me
N
N
+ 2 HC
N
N
N
OCH3 Me
O
O
O
O
O
C
O
C
CH2 K+
-
+
tBu-OK
+
+
tBu-OH
CH3
N
N
O
O
O
O
CH2 K+
-
O
+
O
N
2
O
N
AcOH
NH4OAc
N
N
N
Scheme 2. Synthesis of L1.

F. Pelascini et al. / Polyhedron 23 (2004) 3193–3199
3195
ꢀ
istic of the iron (III) anion FeCl4 [5], indicated that we
308 cmꢀ1 for the yellow complex obtained, for which
formula L2FeCl2 can hence be assigned with some con-
fidence. Again, however, dissolution in MeCN (r.t.) or
in THF (70 ꢁC) leads to conversion of this neutral com-
were in the presence of a third complex. An X-ray dif-
fraction study allowed us to confirm this conclusion
and to identify this complex as ðL1Þ Fe2þðFeCl4ꢀÞ .
2
2
The highly distorted and compressed molecular struc-
ture of the iron (II) cation (Fig. 1) is close to that of
the analogous complex containing ligands 6,600-diphe-
nyl-2,20:60,200-terpyridine [6]. Most notably, the long
iron–nitrogen bonds are indicative of a high-spin com-
plex and the observation of two even longer distances
plex into its ionic form ðL2Þ Fe2þFeCl42ꢀ. No important
2
colour change is observed in this case, but the IR
absorption assigned to iron–chlorine stretching is shifted
to 282 cmꢀ1 (the approximate position of the FeCl4
2ꢀ
anion [5]) for the yellow crystalline solid obtained from
these solutions.
The precise nature of complex ðL2Þ Fe2þFeCl4 was
2ꢀ
˚
of 2.422 A between iron and the nitrogen atom of one
2
of the two lateral pyridyl units of each terpyridine ligand
suggests that these two ligands may be considered as
only bidentate. Extensive intramolecular p-stacking of
the phenyl and pyridyl rings is also remarkable [6].
established by X-ray crystallography at room tempera-
ture because a lower temperature destroys the crystal.
We could not find a greater symmetry for this crystal
so we are in presence of the not centered Pn group not
either chiral these explains the rather bad xflack value
obtained. The unit cell contains two independent dica-
tions whose octahedral coordination geometry and over-
all structural parameters (Fig. 2) are similar to those of
the corresponding cobalt (II) [8a], nickel (II) [8a] and
copper (II) [8b] complexes and recently the iron ana-
logue has been described with PF6ꢀ as the counter anion
[8c]. In particular, the two mesityl rings of each ligand
are p-stacked with the pyridine ring of the other ligand.
ꢀ
The structure of the FeCl4 anions is unexceptional
[5]. The oxidizing agent at the origin of their formation
could not be identified. In our case, partial oxidation by
accidental air introduction could be favoured by the
longer heating period. The presence of the paramagnetic
ꢀ
FeCl4 counter anion obviously only little modifies the
1H NMR spectrum of the paramagnetic cationic com-
plex, which remains close to that of the previously re-
ported analogous species that had diamagnetic
perchlorate counteranions [6].
Ligand 2,6-bis(3-Mes-N-pyrazolyl)pyridine (L2) [7]
was synthesized following the methods reported previ-
ously and coordinated to iron (II) chloride by the proce-
dure described for L1. This afforded a yellow precipitate.
The iron-chlorine stretching vibration is found at
Fig. 2. Ortep view and numbering scheme of one of the two
independent dications in the crystal of ðL2Þ Fe2þFeCl4 at 293 K
2ꢀ
2
(50% probability thermal ellipsoids). Hydrogen atoms are omitted
˚
Fig. 1. Ortep view and numbering scheme of the C2-symmetric
cationic part of compound ðL1Þ Fe2þðFeCl4ꢀÞ at 173
for clarity. Selected bond lengths (A) and bond angles (ꢁ):
K
(50%
probability thermal ellipsoids). Hydrogen atoms are omitted for
Fe3–N1 = 1.987(8), Fe3–N3 = 1.874(7), Fe3–N5 = 1.999(8), Fe3–
N6 = 2.015(6), Fe3–N8 = 1.883(7), Fe3–N10 = 1.962(6), N1–Fe3–
N3 = 81.2(4), N1–Fe3–N5 = 161.7(3), N1–Fe3–N6 = 91.7(3), N1–
Fe3–N8 = 98.0(3), N1–Fe3–N10 = 91.3(3), N3–Fe3–N5 = 80.6(4),
2
2
˚
clarity. Selected bond lengths (A) and bond angles (ꢁ): Fe1–
N1 = 2.227(3),
Fe1–N1 = 89.0(2), N1–Fe1–N2 = 75.1(1), N1–Fe1–N2 = 124.2(1),
N1–Fe1–N3 = 147.3(1), N1–Fe1–N3 = 103.3(1), N2–Fe1–N2 =
Fe1–N2 = 2.100(3),
Fe1–N3 = 2.422(3),
N1–
N3–Fe3–N6 = 99.2(3),
N3–Fe3–N8 = 178.7(3),
N3–Fe3–N10 =
99.9(3), N5–Fe3–N6 = 90.0(3), N5–Fe3–N8 = 100.2(3), N5–Fe3–
N10 = 93.0(3), N6–Fe3–N8 = 79.8(3), N6–Fe3–N10 = 160.9(3), N8–
Fe3–N10 = 81.1(3).
155.3(2), N2–Fe1–N3 = 73.0(1), N2–Fe1–N3 = 88.4(1), N3–Fe1–
N3 = 82.6(1).

3196
F. Pelascini et al. / Polyhedron 23 (2004) 3193–3199
Much shorter Fe–N bond distances than in (L1)2Fe2+
(Fig. 1) indicate however that this complex is low-spin
[9], while the cobalt complex is high-spin over a wide
temperature range. Furthermore, the parent iron (II)
complex containing two non-substituted ligands 2,6-
bis(N-pyrazolyl)pyridine is low-spin only at low temper-
ature and if the counteranion is BF4ꢀ, and becomes
high-spin at room temperature [10]. The low-spin nature
of complex (L2)2Fe2+ is hence rather unexpected since
incorporation of sterically demanding substituents adja-
cent to the ligand donor atoms, as well as higher temper-
atures, are known to favour high-spin states [5,11]. The
rings of a given ligand are twisted towards each side of
the adjacent pyridine plane. The average dihedral angle
between the pyrazolyl planes and the pyridine ones is
5.1ꢁ. This causes the corresponding mesityl substituents
and the pyridine ring with which they are p-stacked to
become significantly staggered (Fig. 3). Finally, the
2ꢀ
FeCl4 high-spin dianion [12] exists as well as two inde-
˚
pendent molecules that show ca.ꢀ0.11 A longer Fe–Cl
bond distances than the FeCl4 anions of complex
ðL1Þ Fe2þðFeCl4ꢀÞ . One of them is also more dissym-
2
2
metric than the other.
Reacting ligand L2 with iron (III) chloride (1 equiv)
in MeCN is followed by partial reduction of the metal
centers and formation of the same dicationic iron (II)
complex in combination with the iron (III) counteran-
ions FeCl4ꢀ. No neutral precursor could be detected,
and a fraction (ꢁ1/3) of the initial ligand L2 remains
uncomplexed in the reaction mixture. We obtained this
result when the reaction was carried out at 70 ꢁC and
we verified that the same result is obtained when the
reaction was done at room temperature. Brown-red
crystals of the solvated complex ðL1Þ Fe2þðFeCl4ꢀÞ
2ꢀ
paramagnetic counteranions FeCl4 play possibly an
important role in this behaviour. By comparison with
the crystal structure of the low-spin parent complex
[10a], it can be concluded that the introduction of the
mesityl substituents on the pyrazolyl rings only slightly
˚
lengthens the Fe–Npz bonds (+0.011 A average) and
˚
shortens the Fe–Npy bonds (ꢀ0.014 A average).
Although of very similar geometry, the two independ-
ent dications show distinctive distortions that are visual-
ized in Fig. 3. In the one already presented in Fig. 2, the
two bispyrazolylpyridine ring systems are nearly planar,
the three p-stacked aryl rings are almost perfectly
eclipsed, and one ligand is coordinated much more
2
2
ðTHFÞ were obtained when the crude product is dis-
4
solved in THF at room temperature, nice crystals were
produced, and were analyzed by infrared spectroscopy
(mFe–Cl = 380 cmꢀ1) and X-ray crystallography.
All these complexes (mono or bis ligands) were tested
for the polymerization of ethylene in the presence of
methylaluminoxane. Although for the bis ligand com-
plexes the results were in some way expected [13], none
of them produced polymers.
˚
asymmetrically than the other (Fe3–N6 = 2.015(6) A,
˚
Fe3–N10 = 1.962(6) A, Fig. 2). This latter difference is
less pronounced in the second molecule, in which a
slight deviation from planarity is indeed observed for
both bispyrazolylpyridine ring systems. The individual
aromatic rings remain planar, but the two pyrazolyl
Fig. 3. Ortep view of the two independent dications in the crystal of ðL2Þ Fe2þFeCl4 at 293 K (50% probability thermal ellipsoids). Hydrogen
2ꢀ
2
˚
atoms are omitted for clarity. The left hand molecule is the one already shown in Fig. 2. Selected bond lengths (A) for the right hand molecule: Fe4–
N11 = 1.998(7), Fe4–N13 = 1.893(7), Fe4–N15 = 1.983(7), Fe4–N16 = 1.988(6), Fe4–N18 = 1.889(6), Fe4–N20 = 1.967(6).

F. Pelascini et al. / Polyhedron 23 (2004) 3193–3199
3197
3. Experimental
3.2.3. Synthesis of FeCl2[L1][THF]
FeCl2 [L1] (50 mg, 9.25.10ꢀ2 mmol) of a dark powder
very sparingly soluble with 10 mL of THF were heated
at 90 ꢁC in an oil bath in a 50 mL closed screw cap bottle
and PTFE-faced rubber liner. Two kinds of crystals
were produced by this way, none of them were suitable
for an X-ray study. Ones were very small orange crystals
attributed to FeCl2[L1][THF], with mFe–Cl: 307 and 326
cmꢀ1 and mC–O(THF): 1028 cmꢀ1. The other ones were
violet crystals produced at the interface of the liquid
and were identical to the starting product.
3.1. General
As the inorganic compounds described herein are air-
sensitive, all experiments were performed in a glove box
under controlled nitrogen atmosphere. THF, diethyl
ether, pentane were dried over Na-benzophenone and
acetonitrile over CaH2 before distillation under nitro-
gen. Anhydrous FeCl2 (Strem) and FeCl3 were used as
purchased. Ligand L2 was synthesized according to pro-
cedures described previously in the literature [8]. 1H
NMR spectra were recorded on Bruker AC-200 or
Avance-300 spectrometers at ambient temperature,
chemical shifts are reported in parts per million versus
SiMe4 and were determined by reference to the residual
solvent peaks. The infrared spectra were recorded on a
Perkin–Elmer 1650 FT instrument. Mass spectrum was
3.2.4. Synthesis of Fe[L1]22þ[FeCl4]2ꢀ
In order to obtain crystals suitable for an X-ray
investigation, five tightly closed flasks containing each
10 mg of the complex FeCl2[L1][THF] with 2 mL of
THF were heated at 120 ꢁC over a long period of time
(several days). At this temperature, only a little part of
the complex was in solution which was only very slightly
colored. By this way, big enough orange crystꢀals were
´
performed by the Service de Spectrometrie de Masse
de lÕInstitut Le Bel (Strasbourg) and elemental analysis
by the Service de Microanalyse de lÕInstitut Charles Sa-
dron (Strasbourg).
obtained that revealed to be Fe½L1ꢂ ½FeCl4ꢂ of the
2þ
2
2
same color than the starting complex that was still pre-
sent in some amount (confirmed by infrared), as well as
other compounds that could not be characterized.
1H NMR (CDCl3, 300 MHz): d: 77.45 (2H, s, H3/
3.2. Synthesis
3.2.1. Synthesis of ligand L1
H ), 67.62 (2H, s, H ), 58.19 (2H, s, H /H ), 14.42
5
3
3
5
0
tert-BuOK (2 g, 17.8 mmol) and p-methylacetophe-
none (1 g, 7.4 mmol) were dissolved in 40 mL of THF
at room temperature. After 2 h, 2,6-bis(3-chlorodimeth-
ylaminium-1-oxopropyl)pyridine (1 g, 3.7 mmol) was
added. After 8 h, 10 g of ammonium acetate, and 14 mL
of acetic acid were added to the red solution to yield a yel-
low solution. The solution was refluxed for 24 h. The sol-
vent was evaporated under vacuum and the acid was
neutralized by addition of an aqueous saturated solution
of sodium hydrogenocarbonate. The product was
extracted with dichloromethane (three times 100 mL)
and filtered over a neutral alumina column. After evapo-
ration of the solvent, the solid residue was recrystallized
from CH2Cl2/hexane to afford a greyish powder. Yield
(2H, s, H4), 1.87 (6H, s, Me), 0.78 (8H, large, Artol),
0
ꢀ19.21 (1H, s, H4 ). IR (CsI, Nujol) mFe–Cl: 378 cmꢀ1
.
ES+MS in CHCl3: gives the isotopic pattern with the
corresponding intensities for the dicationic fragment in
good agreement with the simulation: [FeN6C58H46]2+
m/z: 440.15, 440.65, 441.15, 441.65, 442.15, and 442.65.
:
3.2.5. Synthesis of FeCl2[L2]
FeCl2 (32mg, 0.25 mmol)and oneequivalent ofL2 (112
mg, 0.25 mmol) were maintained under magnetic stirring
in 12 mL of THF at room temperature for 12 h. The amor-
phous yellow complex in suspension were then isolated
and washed with 2 mL of THF affording 125 mg
(87%, yield) of a yellow powder. IR mFe–Cl: 308 cmꢀ1
.
1
600 mg (40%). H NMR (CDCl3, 300 MHz): d 8.70
0
(2H, d, J 8 Hz, H3), 8.59 (2H, d, J 8 Hz, H3 ), 8.09 (4H,
3.2.6. Synthesis of Fe[L2]22þ[FeCl4]2ꢀ
d, J 8 Hz, H0), 8.01 (1H, t, J 8 H0z, H4), 7.92 (2H, t, J 8
About 100 mg of the yellow powder FeCl2[L2] was
heated up in 10 mL of THF at 80 ꢁC for 4 h.The solution
is only slightlycolored and analmostquantitative amount
0
Hz, H4 ), 7.78 (2H, d, J 8 Hz, H5 ), 7.33 (4H, d, J 8 Hz,
Hm) 2.44 (6H, s, Me). IR (CsI, Nujol) m (cmꢀ1): 1567.5,
1461.8, 1377.0, 794.7. MS (FAB) m/z: 414.2.
of orange crystals are formed. IR mFe–Cl: 282 cmꢀ1
.
3.2.2. Synthesis of FeCl2[L1]
3.2.7. Synthesis of Fe[L2]22þ[FeCl4]2ꢀ ꢃ 4THF
FeCl2 (32 mg, 0.25 mmol) and one equivalent of L1
(103 mg, 0.25 mmol) were maintained under magnetic
stirring in 12 mL of THF at room temperature for 24
h. The dark suspension was then isolated and washed
with 2 mL of THF affording 107 mg (80%, yield) of a
dark powder. IR mFe–Cl: 304 cmꢀ1. Anal. Calc. for
C29N3H23FeCl2: C, 64.47; H, 4.29; N, 7.78. Found: C,
64.44; H, 4.31; N, 7.65%.
FeCl3 (40 mg, 0.25 mmol) was poured into 20 mL of
acetonitrile, then one equivalent of L2 (112 mg, 0.25
mmol) was added and the mixture was maintained un-
der magnetic stirring for 2 h. Some product remained
insoluble. Heating at 80 ꢁC completed the dissolution.
After cooling, a product crystallized, the IR revealed
the unreacted ligand L2. After separation of excess L2
and evaporation of the solvent under vacuum a yellow

3198
F. Pelascini et al. / Polyhedron 23 (2004) 3193–3199
Table 1
2
X-ray experimental data for compounnds ðL1Þ Fe2þðFeCl4ꢀÞ ; ðL Þ Fe2þFeCl4 and ðL2Þ Fe2þðFeCl4ꢀÞ ꢃ 4ðTHFÞ
2ꢀ
2
2
2
2
2
ðL1Þ2Fe2þðFeCl4ꢀÞ2
ðL2Þ2Fe2þFeCl4
ðL2Þ2Fe2þðFeCl4ꢀÞ2 ꢃ 4ðTHFÞ
C74H90Cl8Fe3N10O4:
2ꢀ
Empirical formula
C
58H46Fe3N6Cl8:
C58H58Fe2N10Cl4:
C58H58FeN10FeCl4
1148.68
C58H46FeN62FeCl4
1278.22
173
C58H58FeN102FeCl44C4H8O
1634.77
173
Formula weight
Temperature (K)
Crystal system
Space group
293
monoclinic
P1n1
monoclinic
C12/c1
monoclinic
C1c1
˚
a (A)
26.5117(4)
14.1544(2)
15.9627(3)
110.183(5)
5622.3(2)
4
11.3497(2)
23.8420(4)
21.0341(5)
99.606(5)
5612.0(2)
4
14.9889(3)
23.9306(5)
21.7798(4)
94.106(5)
7792.2(3)
4
˚
b (A)
˚
c (A)
b (ꢁ)
3
˚
V (A )
Z
Color
Crystal size (mm)
orange
orange
brown
0.20 · 0.15 · 0.08
1.51
2600
0.16 · 0.12 · 0.10
1.36
2384
0.16 · 0.12 · 0.09
1.39
3400
Dcalc.(g cmꢀ3
F(000)
)
Absorption coefficient (mmꢀ1
Index ranges
)
1.189
0.755
0.879
ꢀ36 6 h 6 36, ꢀ17 6 k 6 19,
ꢀ13 6 h 6 13, ꢀ30 6 k 6 28,
0 6 h 6 20, 0 6 k 6 32,
ꢀ29 6 l 6 29
2.5–29.08
10620
ꢀ21 6 l 6 21
2.5–29.12
13617
ꢀ27 6 l 6 27
2.5–27.46
21543
h Range (ꢁ)
Reflections collected
Reflections observed [I > 3r(I)]
Number of variables
Trans. min and max
R
4793
339
4725
1331
6318
890
0.9613/1.1570
0.050
0.087
0.884/0.927
0.034
0.035
0.8950/1.0000
0.046
0.067
Rw
Goodness-of-fit on F2
1.531
0.502
1.007
0.191
1.261
0.200
Largesꢀt 3difference peak and hole
˚
(e A
)
brown compound was obtained. The IR revealed mFe–Cl
:
Data Centre, CCDC Nos. 203433, 203434, 203435 for
(C58H58Cl4Fe2N10) fðL2Þ Fe2þFeCl42ꢀg, (C58H46Cl8Fe3-
N6) fðL1Þ Fe2þðFeCl4ꢀÞ2g and (C74H90Cl8Fe3N10O4)
386 cmꢀ1. The crude product was then dissolved in a
minimum of THF (2 mL) and after a while nice brown
2
2
crystals were formed. The IR revealed the same mFe–Cl
:
fðL2Þ Fe2þðFeCl4ꢀÞ ðTHFÞ g, respectively. These data
2
2
4
386 cmꢀ1 and supplementary bands at 1052 and 897
cmꢀ1 attributed to THF. The crystals are suitable for
an X-ray analysis. ES + MS in CHCl3: gives the isotopic
pattern with the corresponding intensities for the dicat-
ionic fragment in good agreement with the simulation:
[FeN10C58H58]2+: m/z: 474.21, 474.71, 475.21, 457.71,
476.21, and 476.71.
can be obtained free of charge via www.ccdc.cam.ac.
uk/data_request/cif, by emailing data_request@ccdc.
cam.ac.uk, or by contacting The Cambridge Crystallo-
graphic Data Centre, 12, Union Road, Cambridge
CB2 1EZ, UK; fax: +44 1223 336033.
Acknowledgements
3.3. X-ray crystallography
We are grateful to Mrs. Michelle Martigneaux from
the Service Commun NMR and Caroline Dietrich-Schn-
´
eider from the Service de Spectrometrie de Masse at the
University Louis Pasteur Strasbourg.
Data were collected on a Nonius Kappa CCD diffrac-
˚
tometer (graphite Mo Ka radiation, 0.71073 A). The
structure was solved using the Nonius OpenMoleN
package and refined by full matrix least-squares with
anisotropic thermal parameters for all non-hydrogen
atoms. Data collection parameters, solution and refine-
ments results are given in Table 1.
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