Synthesis and reactivity of 1,8-bis(imino)carbazolide complexes of iron, cobalt and manganese

Article abstract of DOI:10.1039/b301902k

The synthesis and characterisation of a new family of monoanionic, tridentate bis(imino)carbazolide ligands (L) and their cobalt, iron and manganese complexes are described. The solid state structure of the five coordinate Fe^III complex LFeCl₂ (9c) reveals a trigonal bipyramidal geometry with a short Fe-N(carbazolide) bond (1.959(3) A), indicative of π-donation from the carbazole nitrogen to the metal centre. The cationic derivatives LFeCl(MeCN)⁺ (11), LFe(acac)⁺ (12) and LCo(MeCN)⁺ (14) have been prepared by chloride abstraction from the neutral precursors using AgSbF₆ or Ag(acac). Treatment of LMCl_n (M = Fe, Co) complexes with MeLi affords metal-methyl species, tentatively formulated as LFeMe₂ (13), LFeMe (16a) and LCoMe (16b). All of the Mn, Fe and Co compounds are paramagnetic and generally exhibit magnetic moments consistent with high spin configurations. In certain cases, however, low spin as well as intermediate spin configurations are found, depending on the nature of the co-ligands around the metal centre. The LFeCl₂ 9c complex exhibits a room temperature magnetic moment of 4.8 μ_B and is a rare example of a trigonal bipyramidal Fe^III complex in which a spin admixture between a high spin and an intermediate spin state is present. None of the divalent or trivalent bis(imino)carbazolide metal complexes, using a variety of activators, showed activity for ethylene oligomerisation or polymerisation.

Full text of DOI:10.1039/b301902k

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Synthesis and reactivity of 1,8-bis(imino)carbazolide complexes of
iron, cobalt and manganese
Vernon C. Gibson,* Stefan K. Spitzmesser, Andrew J. P. White and David J. Williams
Department of Chemistry, Imperial College London, South Kensington Campus, London,
UK SW7 2AZ
Received 18th February 2003, Accepted 1st May 2003
First published as an Advance Article on the web 30th May 2003
The synthesis and characterisation of a new family of monoanionic, tridentate bis(imino)carbazolide ligands (L)
and their cobalt, iron and manganese complexes are described. The solid state structure of the five coordinate FeIII
complex LFeCl2 (9c) reveals a trigonal bipyramidal geometry with a short Fe–N(carbazolide) bond (1.959(3) Å),
indicative of π-donation from the carbazole nitrogen to the metal centre. The cationic derivatives LFeCl(MeCN)ϩ
(11), LFe(acac)ϩ (12) and LCo(MeCN)ϩ (14) have been prepared by chloride abstraction from the neutral precursors
using AgSbF6 or Ag(acac). Treatment of LMCln (M = Fe, Co) complexes with MeLi affords metal–methyl species,
tentatively formulated as LFeMe2 (13), LFeMe (16a) and LCoMe (16b). All of the Mn, Fe and Co compounds are
paramagnetic and generally exhibit magnetic moments consistent with high spin configurations. In certain cases,
however, low spin as well as intermediate spin configurations are found, depending on the nature of the co-ligands
around the metal centre. The LFeCl2 9c complex exhibits a room temperature magnetic moment of 4.8 µB and
is a rare example of a trigonal bipyramidal FeIII complex in which a spin admixture between a high spin and an
intermediate spin state is present. None of the divalent or trivalent bis(imino)carbazolide metal complexes, using
a variety of activators, showed activity for ethylene oligomerisation or polymerisation.
Introduction
Results and discussion
Compared to the plethora of transition metal amide complexes
based on pyrrolide ligands, the number of complexes supported
by carbazolides is rather small, though a few examples can be
found across the transition metal series.1 Reports in the patent
literature also claim moderate to high ethylene polymerisation
activity for simple titanium and zirconium carbazolide
complexes of the type (carbazolide)nM(X)4Ϫn (X = Cl, benzyl,
n = 1–4) but little characterisation data are given.2 In all cases,
unsubstituted carbazole is employed as an anionic, mono-
dentate amide ligand. In our ongoing research on non-metallo-
cene olefin polymerisation catalysts we have recently described
the synthesis of bis(imino)carbazolide Co and Fe complexes 1a
and 1b (Fig. 1).3 The tridentate coordination mode of the carb-
azolide ligand was confirmed by X-ray analysis of 1a. It also
revealed a distorted tetrahedral coordination mode around the
Co centre. Both complexes, when activated with MAO, showed
no activity towards the polymerisation of ethylene, which is in
stark contrast to the high polymerisation activity of related
bis(imino)pyridine complexes of Co and Fe.4 In order to probe
the influence of steric and electronic factors in bis(imino)carb-
azolide complexes a range of ligands with a variety of imino
substituents have been prepared. In this paper we describe in
detail the synthesis of divalent and trivalent late transition
metal complexes bearing bis(imino)carbazolide ligands and of
their cationic and alkyl derivatives, as well as their evaluation as
ethylene polymerisation catalysts.
Complex synthesis
The required carbazole ligand precursor, 1,8-diformylcarb-
azole, can be prepared in high overall yield from carbazole via
the previously reported pathway A (Scheme 1), resulting in the
formation of the methyl substituted derivative 6a.3 tBu-groups
can be introduced into the carbazole moiety through reaction
of carbazole with
tBuCl under modified Friedel–Crafts condi-
tions using AlCl3 catalyst in dichloromethane solution (path-
way B). The resulting di-tBu-carbazole 4b5 can be converted to
the dibromo derivative 5b by bromination with bromine, which
is then converted to the 1,8-diformylcarbazole 6b using CO2 as
the N-protection group during the initial lithiation reaction.
Schiff-base condensation of the dialdehydes 6a and 6b with
different aryl and alkyl amines affords the bis(imino)carbazole
ligand precursors 7a–d which can be isolated as bright yellow
crystalline solids (Scheme 1).
1
In the H NMR spectra of 7a–d the carbazole N–H proton
gives rise to a broad signal between 12.06 and 12.70 ppm, its
considerable downfield shift from unsubstituted carbazole
being indicative of hydrogen bonding to the imino nitrogens.6
This implies an E-configuration of the imino C᎐N double
᎐
bond; no E/Z-isomerism is observed in solution at room tem-
perature. The E-isomer also prevails in the solid state as shown
by the molecular structure of 7a (Fig. 2).
The molecule has approximate Cs symmetry about a plane
that passes through N(1) and the middle of both the C(7)–C(8)
bond and the N(14) ؒ ؒ ؒ N(26) vector, and lies orthogonal to
the bis(imino)carbazole unit which, excluding the two pendant
2,4,6-trimethylphenyl rings, is planar to within 0.069 Å. Rather
than being oriented approximately orthogonal to the plane of
the bis(imino)carbazole moiety, the two terminal aryl rings are
noticeably inclined [by ca. 67Њ for the C(15)-based ring, and by
ca. 71Њ for the C(27)-based ring] in opposite senses such that the
C(21) and C(33) methyl groups are brought towards each other
whilst the C(23) and C(35) methyl groups are moved further
apart [the C(21) ؒ ؒ ؒ C(33) and C(23) ؒ ؒ ؒ C(35) separations are
3.94 and 7.30 Å respectively]. In contrast to the solution state
1H NMR studies, in the solid state there is no evidence that the
Fig. 1 Bis(imino)carbazolide complexes of CoII and FeII.
D a l t o n T r a n s . , 2 0 0 3 , 2 7 1 8 – 2 7 2 7
T h i s j o u r n a l i s © T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 3
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N(1)–H proton (which was clearly located from a difference
electron density map as being bound to N(1) at a conventional
N–H distance) is involved in strong hydrogen bonding to the
imino nitrogens N(14) and N(26), the H(1) ؒ ؒ ؒ N(14) and
H(1) ؒ ؒ ؒ N(26) separations being 2.44 and 2.43 Å respectively.
The carbazole ring systems of centrosymmetrically related
pairs of molecules π-stack with a mean interplanar separation
of 3.52 Å, the centroids of the respective two central five-
membered C4N rings being ca. 3.99 Å apart.
Deprotonation of 7a–d can be achieved in thf solution using
nBuLi at room temperature or NaH at 65 ЊC (Scheme 2). The
deprotonated ligands were generally used in situ, only the
mesityl substituted derivatives 8a and 8b were isolated and
characterised. They are obtained as air and moisture sensitive
amorphous solids, the Li salt 8a showing considerable solubility
in pentane, which accounts for its lower isolated yield. In both
complexes one thf molecule is coordinated to the metal centre
as confirmed by NMR spectroscopy and elemental analyses.
Surprisingly, deprotonation of 7b with NaH to form 8b does
not take place at ambient temperature, even after prolonged
reaction times. Forcing conditions with reaction temperatures
above 60 ЊC and reaction times > 8 h are required for complete
deprotonation. Steric constraints arising from the bulky aryl-
iminosubstituentsmightberesponsibleforhinderedaccessofthe
NaH base.
Scheme 1 Synthesis of the bis(imino)carbazoles 7a–d.
Scheme 2 Synthesis of bis(imino)carbazolide complexes 8–10.
Divalent and trivalent transition metal complexes were
formed by analogous procedures to those employed for the
synthesis of bis(imino)carbazolide CoII and FeII complexes
described previously,3 via salt metathesis reactions with either
the isolated or in situ generated sodium or lithium salts derived
from 7a–d (Scheme 2). Conveniently, all ligand Na and Li salts
Fig. 2 The molecular structure of 7a. Selected bond lengths (Å);
C(14)–N(14) 1.273(3), C(26)–N(26) 1.270(3).
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Table 1 Selected bond lengths (Å) and angles (Њ) for 9c
2.72 and 2.69 Å and the associated C–H ؒ ؒ ؒ Cl angles are 131
and 134Њ, respectively.
Fe–Cl(1)
Fe–N(1)
Fe–N(23)
C(23)–N(23)
2.2366(11)
1.959(3)
2.223(3)
1.277(5)
Fe–Cl(2)
Fe–N(14)
C(14)–N(14)
2.2318(11)
2.179(3)
1.295(5)
Centrosymmetrically related pairs of molecules are involved
in π–π stacking interactions between their carbazole ring
systems, and between their C(20)-containing phenyl rings.
These interactions are supplemented further by pairs of short
C–H ؒ ؒ ؒ π contacts between C(16)–H of one molecule and the
pyrrole ring of the next, and vice versa (Fig. 4). The π–π stacking
interactions have respective centroid ؒ ؒ ؒ centroid and mean
interplanar separations (Å) of (a) 3.76, 3.47; (b) 4.00, 3.44. The
C–H ؒ ؒ ؒ π contacts (c) have H ؒ ؒ ؒ ring–centroid distances of
2.68 Å and C–H ؒ ؒ ؒ π angles of 144Њ.
N(1)–Fe–N(14)
N(14)–Fe–N(23)
N(14)–Fe–Cl(2)
N(1)–Fe–Cl(1)
N(23)–Fe–Cl(1)
89.40(12)
174.66(12)
92.95(9)
120.01(9)
87.48(9)
N(1)–Fe–N(23)
N(1)–Fe–Cl(2)
N(23)–Fe–Cl(2)
N(14)–Fe–Cl(1)
Cl(2)–Fe–Cl(1)
88.13(12)
114.38(9)
92.38(9)
89.66(9)
125.57(4)
show a bright green fluorescence in thf solution that disappears
upon complexation to transition metals, providing a useful
indicator for completion of the reaction. The FeIII complexes 9c
and 9d as well as complexes 10a–c are reasonably air stable,
whereas complexes 9a and 9b bearing bulky mesitylimino sub-
stituents decompose in air; they are also less stable in solution
under an inert atmosphere. This could be due to unfavour-
able steric interactions of the chloride ligands with the ortho-
methyl groups on the mesityl substituents, possibly leading to
dissociation of the imino donor group.
All complexes were characterised by means of 1H NMR and
IR spectroscopies, FAB mass spectrometry, magnetic suscepti-
bility measurements and microanalysis. Crystals of 9c suitable
for X-ray analysis were grown from a concentrated solution in
dichloromethane layered with pentane. The molecular structure
of 9c, depicted in Fig. 3, shows the complex to have approximate
molecular Cs symmetry about a plane containing the metal
centre and the two chloride ligands. The geometry at iron is
slightly distorted trigonal bipyramidal with equatorial bond
angles in the range 114.38(9)–125.57(4)Њ and with the axial
nitrogen substituents subtending an angle of 174.66(12)Њ at the
metal (Table 1). The bond to the amido nitrogen, [Fe–N(1)
1.959(3) Å] is significantly shorter than the bonds to the imino
nitrogens N(14), [2.179(3) Å] and N(23), [2.223(3) Å], suggest-
ing some degree of π-donation from the sp2-hybridized carb-
azole nitrogen to the metal centre. Similar bond distances are
observed in a related trigonal bipyramidal FeIII complex bear-
ing a 1,3-bis(2-pyridyilimino)isoindoline ligand, where the
Fe–amido distance is 1.963 Å.7
Fig. 4 The intermolecular π–π and C–H ؒ ؒ ؒ π interactions present in
the crystals of 9c. The centroid ؒ ؒ ؒ centroid and mean interplanar
separations (Å) for the π–π stacking interactions are (a) 3.76, 3.47;
(b) 4.00, 3.44. The C–H ؒ ؒ ؒ π contacts (c) have H ؒ ؒ ؒ ring–centroid
distances of 2.68 Å and C–H ؒ ؒ ؒ π angles of 144Њ.
Reactivity of bis(imino)carbazolide complexes
In our work on bis(imino)pyridine iron complexes we found
that the synthesis of cationic derivatives allowed the use of
co-catalysts other than MAO in ethylene polymerisation experi-
ments and influenced the properties of the polymer produced.8
Thus the analogous cationic complexes were prepared for
bis(imino)carbazolide FeIII complex 9c. Scheme 3 shows the
synthesis of the cationic complexes 11 and 12 via sequential
abstraction of the chloride ligands with AgSbF6 and Ag(acac).
Fig. 3 The molecular structure of 9c.
Excluding the two phenyl rings the bis(imino)carbazolide
moiety is planar to within 0.081 Å (cf. 0.069 Å in the structure
of the related ligand 7a) with the iron atom lying 0.130 Å
‘below’ this plane, in the direction of Cl(2); Cl(1) lies 1.737 Å
‘above’, and Cl(2) 2.213 Å ‘below’ the ligand plane. The two
phenyl rings are each inclined by ca. 67Њ to the ligand plane
(a conformation also seen in 7a), the ortho-hydrogens C(19)–H
and C(24)–H being directed towards Cl(2) suggesting a possible
pair of C–H ؒ ؒ ؒ Cl interactions; the H ؒ ؒ ؒ Cl distances are
Scheme 3 Synthesis of bis(imino)carbazolide FeIII derivatives.
Alkylation reactions on 9c, directed towards the synthesis of
a bis(imino)carbazolide FeIII dialkyl complex were also carried
out. Addition of two equivalents MeLi to a solution of 9c in
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Et2O leads to the formation of a dark brown solution from
which an air sensitive, microcrystalline solid can be isolated in
microanalytical purity. This product is tentatively formulated as
the FeIIIMe2 complex 13. FAB-MS analysis shows signals for
the molecular ion of 13 minus one and two methyl groups; no
signals corresponding to species containing halide ligands are
observed. Several attempts to obtain single crystals for X-ray
analysis were unsuccessful.
A survey in the Cambridge Crystallographic Database
(version 5.20) shows no structurally characterised FeIII dialkyl
complexes, indeed no stable FeIII dialkyl complexes have been
isolated.9 However, a few FeIII mono-alkyl and aryl complexes
have been synthesised and structurally characterised. They are
generally stabilised by dianionic tetraaza-annulene,10 salen11
and porphyrin12 ligands. Unlike the corresponding high spin
halide complexes, their magnetic and spectroscopic properties
indicate the presence of a five-coordinate, square pyramidal low
spin (S = 1/2) metal centre, with the exception of the salen-
based FeIII and some perfluorinated aryl FeIII porphyrin13 com-
plexes, which are high spin. The magnetic moment for the FeIII
dimethyl complex 13 of 1.8 µB also suggests the presence of a
low spin configuration.
Cationic derivatives can also be prepared from the divalent
bis(imino)carbazolide complexes as shown by the synthesis of
the Co complex 14 via chloride abstraction with AgSbF6
(Scheme 4). Oxidation of CoII to CoIII can be achieved by reac-
tion of 10a with excess benzyl chloride over a period of 48 h
and the corresponding CoIII complex 15 can be isolated in low
yield and microanalytical purity. A similar reaction with benzyl
halides was observed by Fryzuk and co-workers for the tetra-
hedral [(PPh2CH2SiMe2)2N]CoII chloride and bromide com-
plexes and trigonal bipyramidal CoIII dihalide complexes were
obtained.14 In this case the reaction proceeds via radical benzyl
intermediates, which recombine to form the dibenzyl side prod-
uct. A similar radical mechanism is believed to be operative in
the one electron oxidation of 10a to 15. A magnetic moment of
4.9 µB is observed for 15, indicating the presence of a high spin
CoIII centre.
formulated as the FeII and CoII methyl complexes. FAB-MS
analysis of both methyl complexes shows signals for the
molecular ions and signals for a fragment obtained by the
loss of the methyl group. No signals corresponding to species
containing halide ligands are observed.
NMR spectroscopy
1
Paramagnetic contact shifted H NMR spectra were recorded
for all CoII and FeII complexes bearing bis(imino)carbazolide
ligands. The MnII complex 10a gave only very broad signals,
which is generally observed for MnII complexes.15 In the case of
the FeII and CoII methyl complexes 16a and 16b, highly compli-
cated 1H NMR spectra were obtained with signals in the
chemical shift range Ϫ80 to 80 ppm. In many cases not all
1
the expected signals are observed, but the H NMR spectrum
can serve as a characteristic fingerprint for the complex.
Infrared spectroscopy
The carbazole based ligand precursors and complexes were
studied by IR spectroscopy as thin sample films on NaCl plates
or as KBr discs. The uncoordinated bis(imino)carbazoles 7a–d
generally exhibit a weak to medium absorption at ca. 1638
cmϪ1, which can be assigned to the C᎐N stretching mode.16
᎐
Upon coordination of a metal centre (complexes 9–16) only
a small shift to lower wavenumber, typically 7–12 cmϪ1, is
observed. This lies in contrast to observations on bis(imino)-
pyridine Fe and Co complexes where generally a shift by
20–30 cmϪ1 to lower wavenumbers was observed for the C᎐N
᎐
stretching mode compared to the free ligand.8 The acac com-
plex 12 also shows two absorption bands at 1557 and 1527
cmϪ1, indicative of a symmetrical coordination of the acac
ligand to the Fe centre.17 The coordinated MeCN donor in 14
18
shows a weak absorption at 2285 cmϪ1 for ν(C᎐N). For the
᎐
᎐
cationic complexes 11, 12 and 14 the typical absorption band
for the Sb–F stretching mode of the SbF6 counterion is
observed at ca. 659 cmϪ1 19
.
Magnetic susceptibility measurements
Complexes 9–16 are paramagnetic, with magnetic moments for
complexes 9a (6.0 µB), 10a (4.5 µB), 10b (5.1 µB), 11 (6.3 µB) and
15 (4.9 µB) indicative of high spin configurations for these d5, d6
and d7 ions.20 By contrast, low spin configurations are found for
the CoII complex 14 (2.2 µB), as well as for the alkyl derivatives
13 (1.8 µB), 16a (2.9 µB) and 16b (3.0 µB). A similar change in
spin state upon alkylation is found for FeII complexes stabilised
by bipyridine (bipy) ligands. For example, (bipy)2FeCl2 is
paramagnetic with a magnetic moment of 5.72 µB,21 whereas
the alkyl derivative (bipy)2FeEt2 possesses a low spin (S = 0)
ground state and is therefore diamagnetic.22
The magnetic moments for complexes 9b (4.1 µB), 9c (4.8 µB),
9d (5.5 µB) and 12 (4.2 µB) are inconsistent with either high spin
or low spin configurations. There are a number of possible
explanations for this unusual magnetic behaviour. In the case of
9c, the molecular structure reveals a monomeric formulation
which rules out any close contact of two Fe centres that could
result in Fe–Fe exchange interactions. Its magnetic moment is,
therefore, likely to result from an intermediate S = 3/2 spin state
that contains some high spin S = 5/2 character. A possible
explanation is that the room temperature magnetic moment
reflects a thermal equilibrium between different spin state tran-
sitions. There are numerous examples for such spin-crossover
phenomena for high spin (S = 5/2) to low spin (S = 1/2) transi-
tions in FeIII complexes, but these are less common for transi-
tions involving the intermediate spin state S = 3/2.23 An example
is trigonal bipyramidal FeCl3(PMe3)2, which displays a room
temperature magnetic moment of 5.2 µB, falling to 4.2 at 233 K,
thus indicating a transition from a high spin S = 5/2 to an
intermediate S = 3/2 state.24 Typical for a thermal equilibrium
Scheme 4 Synthesis of bis(imino)carbazolide FeII and CoII derivatives
(RЈ = 2,4,6-Me3C6H2).
Alkylation reactions of 10a and 10b with a view to synthesis-
ing mono-alkyl FeII and CoII complexes were also investigated.
Addition of MeLi to a solution of the chloride precursors in
Et2O leads to the formation of a dark brown solution from
which air sensitive, microcrystalline solids can be isolated in
microanalytical purity. The products 16a and 16b are tentatively
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of two spin systems are a large temperature dependence of the
magnetic moment and a sigmoidal-type curve of the moment
versus temperature. Alternatively, instead of observing a spin
equilibrium, a quantum mechanical mixing of the two states
can occur to create a new, discrete spin-admixed ground state,
that has elements of both S = 5/2 and S = 3/2 states.25,26 Such
admixed states have been studied intensively for square pyram-
idal and octahedral porphyrin-27 and phthalocyanin-based28
FeIII complexes, giving rise to room temperature magnetic
moments that lie between the intermediate and high spin
extremes of 3.9 and 5.9 µB, the extent of spin-state mixing
depending on the ligand set. The temperature dependence of
the magnetic moment of such a spin-admixed system follows
essentially the Curie law. In practice, however, a slight reduction
of the magnetic moment over a wide temperature range for
spin-admixed complexes is observed. Fryzuk and co-workers
recently reported an example of a trigonal bipyramidal
FeIII complex, [(PPh2CH2SiMe2)2N]FeBr2, exhibiting such
behaviour.25 Variable temperature SQUID magnetometer
measurements revealed a slow and smooth lowering of the
magnetic moment from 4.70 µB at 300 K to 4.45 µB at 20 K,
ruling out a spin-crossover situation and indicating the likely
presence of spin-admixture in this complex. Very similar
behaviour is observed for 9c (Fig. 5). The magnetic moment
decreases from 4.62 µB at 295 K to 4.35 µB at 30 K and no sharp
spin crossover transition is observed. At 5 K the observed
moment is 3.51 µB, which is very close to the value obtained for
the spin-admixed [(PPh2CH2SiMe2)2N]FeBr2 complex (3.49 µB
at 2K).25 The solid state magnetic moment at room temperature
of 4.62 µB for 9c is also in good agreement with the solution
value of 4.8 µB obtained by Evans’ NMR method. From these
data it can be concluded that complex 9c is a rare example of a
trigonal bipyramidal FeIII system, in which spin-admixture
between S = 5/2 and S = 3/2 states has occurred, giving rise to an
intermediate magnetic moment at room temperature.
Fig. 6 The powder EPR spectrum of 9c at rt, microwave frequency
9.57 GHz, microwave power 21 mW, field sweep 0–583.8 mT.
[2,6-bis{(dimethylamino)methyl}phenyl]FeCl2.31 Interestingly,
[(PPh2CH2SiMe2)2N]FeBr2 is EPR silent despite its magnetic
properties also indicating a S = 3/2 ground state.25
Olefin polymerisation
Ethylene polymerisation tests were carried out with complexes
9–12, 14 and 15 in a Radley’s GreenHouse parallel synthesis
reactor and the following co-catalysts: (a) 640 eq MAO (rt and
80 ЊC in toluene solution), (b) 400 eq Me2AlCl (rt in hexane
solution) and (c) 10 eq Me3Al (rt in toluene solution). In all
cases no ethylene polymerisation activity was observed. This
was confirmed by carrying out separate polymerisation tests
under typical Schlenk-line conditions at 1 bar ethylene pressure
and 100 eq. MAO co-catalyst with the FeIII complexes 9a–d.
Addition of MAO to the FeIII complexes 9a–d results in an
immediate colour change from green to yellow, indicating the
formation of a new species, which is inactive. In a separate
experiment, the yellow solution obtained from complex 9d was
hydrolysed by the addition of dilute aqueous HCl. From the
resulting yellow toluene solution the free ligand 7d was isolated
as the only organic material. This excludes attack of the MAO
co-catalyst on the ligand framework as a cause for the form-
ation of a catalytically inactive species. In all Schlenk-line tests
the reaction mixture at the end of the polymerisation run was
also analysed by GC-MS. No oligomeric reaction products
were detected. The ethylene polymerisation activity of the FeIII
dialkyl derivative 13 was tested under Schlenk-line conditions
with a variety of co-catalysts such as MAO, as well as borane-
based Lewis and Brønsted acids such as B(C6F5)3, [CPh3]-
[B(C6F5)4] and [H(OEt2)2][B{3,5-(CF3)2C6H3}4]. However, no
oligomeric or polymeric products were obtained.
The absence of any ethylene polymerisation activity is most
likely a consequence of steric crowding around the metal centre.
By comparison with the bis(imino)pyridine ligand system,4 the
two additional carbon atoms in the backbone of the carb-
azolide ligand allow an extended reach of the imine donors to
the front side of the complex, closing down the space available
to coordinate olefin. It is known from extensive studies on the
bis(imino)pyridine systems that the active site is already rather
hindered, one consequence of which is an exceptional selectiv-
ity towards ethylene over higher α-olefins.32 It would appear
that changing the imino-substituents from mesityl to phenyl in
the carbazolide system is insufficient to make the metal site
accessible. However, an alternative influence on ethylene poly-
merisation activity that cannot be ruled out is the presence
of the highly nucleophilic charged central donor atom in the
carbazolide ligand.
Fig. 5 Plot of magnetic moment (µeff) versus temperature for 9c.
Diamagnetic corrections were neglected.
EPR spectroscopy
Further evidence for an intermediate S = 3/2 ground state in 9c
was obtained from EPR spectroscopy on powdered samples.
For a high spin FeIII complex with five unpaired electrons in a
ligand field with high symmetry a very strong EPR absorption
without hyperfine splitting, and with a g value close to 2.00, is
expected.29 At lower symmetries, zero field splitting increases
and, in the case of axial symmetry, two absorptions with g
values close to 2 and 6 are observed.30
From the EPR spectrum of 9c (Fig. 6), two weak and
very broad absorptions with g values of 4.7 and 2.0 are
observed at room temperature, excluding the presence of
a high spin S = 5/2 ground state. These g values are typical for a
S = 3/2 ground state,26 and similar EPR spectra have been
reported for a spin-admixed FeIII porphyrin complex27 and for
Conclusion
A family of bis(imino)carbazoles has been synthesised and
complexed as monoanionic, tridentate ligands to cobalt, iron
and manganese. All of the products are paramagnetic, with
some showing unusual magnetic behaviour. Cationic derivatives
and metal–methyl species have also been synthesised. Ethylene
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polymerisation tests using high throughput screening method-
ology, supported by conventional Schlenk-line tests, afford
no oligomeric or polymeric products. The absence of reactivity
of the bis(imino)carbazolide complexes towards ethylene is
believed to be a consequence of steric congestion, though an
electronic influence arising from the highly nucleophilic central
donor group cannot be ruled out.
1,8-Dibromo-3,6-di-tert-butyl-9H-carbazole (5b)
4b (152 mg, 0.54 mmol) was dissolved in glacial acetic acid
(15 cm3). At room temperature and with exclusion of light,
bromine (62 µl, 1.20 mmol) was added dropwise via syringe.
After stirring for 60 min, the volatile components were removed
on a rotary evaporator. The residue was dissolved in EtOAc
(100 cm3) and washed with 1 M aqueous NaOH (3 × 30 cm3)
and 1M NaHCO3 (1 × 50 cm3) solutions. The organic phase was
then dried over MgSO4, filtered, and the solvent was removed
on a rotary evaporator to afford a yellow solid. Yield: 445 mg
(99%). Mp 171–172 ЊC. RF (SiO2, hexane/EtOAc 5 : 1) 0.63. 1H
NMR (250 MHz, CDCl3, rt): δ (ppm) 1.42 (s, 18H, C(CH3)3),
7.62 (s, 2H, Ar–H ), 7.95 (s, 2H, Ar–H ), 8.11 (br, 1H, NH ).
13C{1H} NMR (100 MHz, CDCl3, rt): δ (ppm) 31.9 (C(CH3)3),
34.9 (C(CH3)3), 104.0, 115.9, 124.8, 126.6, 136.3, 144.7 (all
Ar–C). EI mass spectrum (m/z): 437 (Mϩ), 422 ([M Ϫ CH3]ϩ).
Anal. calcd. for C20H23Br2N: C, 54.94; H, 5.30; N, 3.20; found:
C, 54.76; H, 5.41; N, 3.09%.
Experimental
General considerations
All manipulations of air and/or moisture sensitive compounds
were performed using standard Schlenk and cannula tech-
niques. Air sensitive compounds were transferred in a nitrogen
filled glove-box and, unless stated otherwise, stored at room
temperature. Crystal data were collected on Siemens P4/PC dif-
fractometers. NMR spectra were recorded on Bruker AC-250
MHz or DRX-400 MHz spectrometers. Infrared spectra were
obtained using thin sample films between NaCl plates or as
KBr discs on a Perkin Elmer 1760X FT-IR spectrometer. Mass
spectra were recorded on either a VG Autospec or a VG Plat-
form II spectrometer. Elemental analyses were performed by
the microanalytical services of the Chemistry Departments of
Imperial College and the University of North London. Mag-
netic susceptibilities were determined by Evans’ NMR method8
in CD2Cl2/cyclohexane (95 : 5 v/v) solution or on a SQUID
magnetometer (MPMS7, Quantum Design) over the temper-
ature range 5–300 K using an applied field of 10 mT.
EPR spectra were recorded on a Bruker 200D spectrometer
operating at X-band frequency (ca. 9.5 Ghz) with 100 kHz
modulation at Queen Mary and Westfield College, University
of London.
1,8-Diformyl-3,6-di-tert-butyl-9H-carbazole (6b)
nBuLi (1.1 cm3, 2.5 M in hexane, 2.8 mmol) was added to a
solution of 5b (1.13 g) in degassed thf (60 cm3) at 0 ЊC. After
stirring at this temperature for 1 h, the reaction mixture was
allowed to warm to rt while CO2 gas (dried by passing through
a CaCl2 filled wash bottle) was bubbled through the solution
for 15 min. The solvent was then removed in vacuo and the
residue was redissolved in degassed thf (60 cm3). At Ϫ78 ЊC,
tBuLi (7.5 cm3, 1.5 M in pentane, 11.3 mmol) was added slowly
and the reaction mixture was stirred at 0 ЊC for 3 h. At Ϫ78 ЊC,
anhydrous DMF (1.0 cm3, 12.9 mmol) was added and the
reaction mixture was allowed to warm to room temperature
overnight. The mixture was hydrolysed at 0 ЊC by addition of
1 M aqueous HCl (10 cm3) and then diluted with EtOAc
(100 cm3). The organic phase was washed with 1 M aqueous
NaOH (2 × 50 cm3) and 1M NaHCO3 (2 × 50 cm3) solutions,
dried over MgSO4, filtered, and the solvent removed on a
rotary evaporator. The crude product was purified by recrystal-
lisation from hot hexane to afford a yellow solid. Yield: 0.50 g
(59%). Mp 190–191 ЊC. RF (SiO2, hexane/EtOAc 5 : 1) 0.32. 1H
NMR (250 MHz, CDCl3, rt): δ (ppm) 1.49 (s, 18H, C(CH3)3),
Solvents and reagents
Solvents were dried by standard procedures. Ethylene was pur-
chased from BOC Gases and used without further purification.
Dimethylformamide (DMF) was dried over calcium hydride
and vacuum-transferred prior to use. Benzyl chloride and
methyl iodide (MeI) were dried over 4 Å molecular sieves
and vacuum-transferred into an ampoule sealed with a Young’s
7.93 (s, 2H, Ar–H ), 8.38 (s, 2H, Ar–H ), 10.22 (s, 2H, O᎐CH ),
tap, degassed by repeated freeze–pump–thaw cycles and stored
᎐
11.44 (br, 1H, NH ). 13C{1H} NMR (100 MHz, CD3CN,
rt): δ (ppm) 32.2 (C(CH3)3), 35.6 (C(CH3)3), 120.9, 124.3,
33
in a refrigerator. B(C6F5)3
C6H3}4]
and [H(OEt2)2][B{3,5-(CF3)2-
34
were prepared according to published procedures.
125.2, 130.8, 137.6, 144.5 (all Ar–C), 194.9 (O᎐CH). IR (KBr):
2,6-Diisopropylaniline was purchased from Aldrich Chemicals
and distilled over zinc powder prior to use. All other reagents
are commercially available and were used without further
purification.
᎐
3430 (s, ν(N–H)), 1682 (s, ν(C᎐O)) cmϪ1. EI mass spectrum
᎐
(m/z): 335 (Mϩ), 320 ([M Ϫ CH3]ϩ). Anal. calcd. for C22H25-
NO2: C, 78.77; H, 7.51; N, 4.18; found: C, 78.89; H, 7.61;
N, 3.97%.
3,6-Di-tert-butyl-9H-carbazole (4b)
1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethyl-9H-carbazole
AlCl3 (8.8 g, 66 mmol) and carbazole 2 (10.0 g, 60 mmol)
were suspended in dichloromethane (100 cm3). Over a period of
90 min, 2-chloro-2-methylpropane (13 cm3, 120 mmol) was
added by syringe pump at 0 ЊC. After the addition was com-
plete, the dark brown solution was stirred at room temperature
for 16 h. The solution was then diluted with dichloromethane
(400 cm3) and washed with 1 M aqueous HCl solution (2 ×
100 cm3) and 3 M aqueous NaCl solution (1 × 100 cm3). After
drying over MgSO4, the solution was isolated by filtration,
and the solvent then removed on a rotary evaporator. The
product was purified by crystallisation from hot hexane to
afford an off-white, amorphous solid. Yield: 7.8 g (47%). RF
(7a)3
6a (470 mg, 1.87 mmol) and 2,4,6-trimethylaniline (530 µl,
3.77 mmol) were dissolved in chloroform (100 cm3). After addi-
tion of 5 drops of glacial acetic acid and 4 Å molecular sieves,
the reaction mixture was refluxed for 3 days and then filtered
while hot. The volatile components were removed on a rotary
evaporator to afford a yellow solid which was then recrystal-
lised from hot ethanol/hexane. Yield: 640 mg (70%). Crystals
suitable for X-ray analysis were grown by slow cooling of a hot,
concentrated solution in hexane to ambient temperature. Mp
1
226–227 ЊC. H NMR (250 MHz, CDCl3, rt): δ (ppm) 2.09 (s,
1
(SiO2, hexane/EtOAc 2 : 1) 0.55. H NMR (250 MHz, CDCl3,
12H, o-CH3), 2.25 (s, 6H, p-CH3), 2.58 (s, 6H, CH3), 6.82 (s, 4H,
Ph-Hm), 7.39 (s, 2H, Ar–H ), 8.03 (s, 2H, Ar–H ), 8.41 (s, 2H,
3
rt): δ (ppm) 1.44 (s, 18H, C(CH3)3), 7.31 (d, 2H, J(HH) = 8.4
3
4
Hz, Ar–H ), 7.45 (dd, 2H, J(HH) = 8.4 Hz, J(HH) = 1.7 Hz,
N᎐CH ), 12.27 (br, 1H, NH ). 13C{1H} NMR (100 MHz, CDCl3,
᎐
4
Ar–H )) 7.82 (br, 1H, NH ), 8.07 (d, 2H, J(HH) = 1.7 Hz,
rt): δ (ppm) 18.3 (o-CH3), 20.7 (p-CH3), 21.3 (CH3), 119.2,
123.4, 123.4, 127.6, 128.2, 128.7, 130.8, 132.8, 136.5, 149.1 (all
Ar–H ). EI mass spectrum (m/z): 279 (Mϩ), 264 ([M Ϫ CH3]ϩ).
The spectroscopic data are consistent with previously published
values for 4b.5
Ar–C), 163.5 (N᎐CH). IR (thin film): 3385 (m, ν(N–H)), 1638
᎐
(m, ν(C᎐N)) cmϪ1. EI mass spectrum (m/z): 485 (Mϩ), 470
᎐
D a l t o n T r a n s . , 2 0 0 3 , 2 7 1 8 – 2 7 2 7
2723

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([M Ϫ CH3]ϩ). Anal. calcd. for C34H35N3: C, 84.08; H, 7.26; N,
8.65; found: C, 84.16; H, 7.17; N, 8.77%.
afford the product as a yellow microcrystalline solid in an
isolated yield of 8%. H NMR (250 MHz, C6D6, rt): δ (ppm)
1
1.21 (m, 4H, OCH2CH2), 2.05 (s, 12H, o-CH3), 2.08 (s, 6H,
p-CH3), 2.60 (s, 6H, CH3), 3.27 (m, 4H, OCH2CH2), 6.68 (s, 4H,
1,8-Bis(2,4,6-trimethylphenylimino)-3,6-di-tert-butyl-9H-
carbazole (7b)
Ph-H ), 7.32 (s, 2H, Ar–H ), 8.26 (br, 4H, Ar–H and N᎐CH).
᎐
m
13C{1H} NMR (63 MHz, CDCl3, rt): δ (ppm) 18.6 (o-CH3),
20.7 (p-CH3), 21.4 (CH3), 25.5 (OCH2CH2), 67.9 (OCH2CH2),
119.0, 123.4, 124.1, 125.7, 128.4, 129.3, 131.9, 133.8, 148.5,
6b (457 mg, 1.36 mmol) and 2,4,6-trimethylaniline (400 µl, 2.85
mmol) were dissolved in ethanol (30 cm3) and 5 drops of glacial
acetic acid were added. After refluxing for 16 h, all volatiles
were removed on a rotary evaporator. The crude product was
purified by crystallisation from hot hexane to afford a dark
149.7 (all Ar–C), 169.4 (N᎐CH). IR (thin film): 1628 (w,
᎐
ν(C᎐N)) cmϪ1. Anal. calcd. for C38H42LiN3O): C, 80.97; H, 7.51;
᎐
N, 7.45; found: C, 81.07; H, 7.41; N, 7.48%.
1
yellow solid. Yield: 360 mg (46%). Mp 230–231 ЊC. H NMR
(250 MHz, CDCl3, rt): δ (ppm) 1.46 (s, 18H, C(CH3)3), 2.10 (s,
12H, o-CH3), 2.25 (s, 6H, p-CH3), 6.82 (s, 4H, Ph-Hm), 7.60 (s,
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethylcarbazolide)-
Na(thf ) (8b)
2H, Ar–H ), 8.28 (s, 2H, Ar–H ), 8.45 (s, 2H, N᎐CH ), 12.26 (br,
᎐
A solution of 7a (2.30 g, 4.7 mmol) in thf (80 cm3) was added to
a suspension of NaH (1.11 g, 46.2 mmol) in thf (20 cm3) at
room temperature. After stirring at 65 ЊC for 16 h, the resulting
deep orange solution was isolated by filtration and the solvent
was removed in vacuo. The oily red residue was co-evaporated
with pentane (2 × 20 cm3) to afford the product as a dark
orange solid. Yield: 2.45 g (99%). 1H NMR (250 MHz, CD2Cl2,
rt): δ (ppm) 1.62 (m, 4H, OCH2CH2), 2.14 (s, 12H, o-CH3), 2.25
(s, 6H, p-CH3), 2.58 (s, 6H, CH3), 3.40 (m, 4H, OCH2CH2), 6.90
(s, 4H, Ph-Hm), 7.31 (s, 2H, Ar–H ), 8.11 (s, 2H, Ar–H ), 8.33 (s,
1H, NH ). 13C{1H} NMR (100 MHz, CDCl3, rt): δ (ppm) 18.4
(o-CH3), 20.8 (p-CH3), 32.0 (C(CH3)3), 34.7 (C(CH3)3), 119.0,
119.6, 123.4, 127.4, 127.6, 128.7, 132.7, 136.6, 142.1, 149.1 (all
Ar–C), 163.7 (N᎐CH). IR (thin film): 3387 (m, ν(N–H)), 1639
᎐
(m, ν(C᎐N)) cmϪ1. EI mass spectrum (m/z): 569 (Mϩ). Anal.
᎐
calcd. for C40H47N3: C, 84.46; H, 8.15; N, 7.39; found: C, 84.61;
H, 8.26; N, 6.98%.
1,8-Diphenylimino-3,6-dimethyl-9H-carbazole (7c)
6a3 (1.02 g, 4.1 mmol) and aniline (820 µl, 9.0 mmol) were
dissolved in toluene (100 cm3). After addition of 4 Å molecular
sieves, the reaction mixture was refluxed for 16 h and then fil-
tered hot. The volatile components were removed on a rotary
evaporator to afford a yellow solid. The crude product was
purified by crystallisation from hot MeCN. Yield: 1.58 g (96%).
Mp 192–194 ЊC. 1H NMR (250 MHz, CDCl3, rt): δ (ppm) 2.59
(s, 6H, CH3), 7.26 (m, 2H, Ph-H ), 7.38 (m, 8H, Ph-H ), 7.48 (s,
2H, N᎐CH). 13C{1H} NMR (63 MHz, CD2Cl2, rt): δ (ppm)
᎐
18.6 (o-CH3), 20.8 (p-CH3), 21.2 (CH3), 25.7 (OCH2CH2), 68.0
(OCH2CH2), 120.5, 123.1, 124.7, 127.0, 129.0, 129.2, 133.4,
134.1, 149.8, 150.6 (all Ar–C), 170.0 (N᎐CH). IR (thin film):
᎐
1627 (m, ν(C᎐N)) cmϪ1. Anal. calcd. for C38H42NaN3O): C,
᎐
78.73; H, 7.30; N, 7.25; found: C, 78.86; H, 7.37; N, 7.09%.
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethylcarbazolide)-
FeCl2 (9a)
2H, Ar–H ), 8.00 (s, 2H, Ar–H ), 8.78 (s, 2H, N᎐CH ), 12.70 (br,
᎐
1H, NH ). 13C{1H} NMR (63 MHz, DMSO-d6, rt): δ (ppm)
21.0 (CH3), 118.9, 121.4, 122.8, 124.1, 126.8, 128.3, 129.2,
A solution of 8b (200 mg, 0.34 mmol) in thf (40 cm3) was added
to a solution of FeCl3 (63 mg, 0.39 mmol) in thf (20 cm3) at
room temperature and stirred for 2 h. The solvent was then
removed under reduced pressure and the residue was extracted
with dichloromethane. The resulting green solution was con-
centrated to 5 cm3 and the product was precipitated by the
addition of pentane (50 cm3). The solid was isolated by fil-
tration and dried in vacuo to give the product as an olive
131.4, 135.8, 150.9 (all Ar–C), 161.1 (N᎐CH). IR (thin film):
᎐
3372 (w, ν(N–H)), 1635 (w, ν(C᎐N)) cmϪ1. UV/VIS (CH2Cl2):
᎐
λmax [nm] (εmax [dm3 molϪ1 cmϪ1]) = 396 (15000), 321 (22000),
241 (33000). EI mass spectrum (m/z): 401 (Mϩ), 324 ([M Ϫ
Ph]ϩ). Anal. calcd. for C28H23N3: C, 83.76; H, 5.77; N, 10.47;
found: C, 83.69; H, 5.84; N, 10.54%.
1
green, microcrystalline solid. Yield: 131 mg (63%). H NMR
1,8-Diisopropylimino-3,6-dimethyl-9H-carbazole (7d)
(250 MHz, CD2Cl2, rt, all peaks appear as broad singlets):
6a3 (1.0 g, 4.0 mmol) and isopropylamine (3.2 cm3, 37.5 mmol)
were dissolved in dichloromethane (100 cm3). After addition of
4 Å molecular sieves and 5 drops of glacial acetic acid, the
reaction mixture was refluxed for 16 h. The solution was then
filtered hot and the solvent was removed on a rotary evaporator
to afford a yellow solid. Yield: 1.21 g (91%). Mp 114–116 ЊC. 1H
δ (ppm) 28.1 (12H), 73.5 (2H), 96.51 (4H). IR (KBr): 1631 (w,
ν(C᎐N)) cmϪ1. FAB mass spectrum (m/z): 575 ([M Ϫ Cl]ϩ), 540
᎐
([M Ϫ 2Cl]ϩ). Anal. calcd. for C34H34Cl2FeN3ؒCH2Cl2: C, 60.37;
H, 5.21; N, 6.03; found: C, 60.60; H, 4.90; N, 5.86%. µeff (Evans’
NMR method) = 6.0 µB.
3
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-di-tert-
butylcarbazolide)FeCl2 (9b)
NMR (250 MHz, CDCl3, rt): δ (ppm) 1.44 (d, 12H, J(HH) =
i
3
6.5 Hz, Pr–CH3), 2.59 (s, 6H, CH3), 3.61 (sept, 2H, J(HH) =
6.5 Hz, iPr–CH ), 7.28 (s, 2H, Ar–H ), 7.90 (s, 2H, Ar–H ), 8.53
To a solution of 7b (150 mg, 0.25 mmol) in thf (20 cm3) was
(s, 2H, N᎐CH ), 12.06 (br, 1H, NH ). 13C{1H} NMR (63 MHz,
n
᎐
added BuLi (100 µl, 2.5 M in hexane, 0.25 mmol) at Ϫ78 ЊC.
CDCl3, rt): δ (ppm) 21.3 (CH3), 24.9 (iPr–CH), 62.6 (iPr–CH3),
The resulting deep orange solution was allowed to warm to
ambient temperature over a period of 1 h. A solution of FeCl3
(45 mg, 0.28 mmol) in thf (20 cm3) was then added dropwise
over a period of 45 min. After stirring for 5 h at rt the solvent
was removed under reduced pressure and the residue was
extracted with toluene. The solution was then pumped to dry-
ness and the crude product recrystallised from hot toluene/
119.2, 122.2, 123.2, 127.6, 129.6, 136.6 (all Ar–C), 158.8 (N᎐
᎐
.
CH). IR (thin film): 3372 (m, ν(N–H)), 1643 (m, ν(C᎐N)) cmϪ1
᎐
EI mass spectrum (m/z): 333 (Mϩ), 290 ([M Ϫ Pr]ϩ). Anal.
calcd. for C22H27N3: C, 79.24; H, 8.16; N, 12.60; found: C,
79.14; H, 8.12; N, 12.62%.
i
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethylcarbazolide)-
Li(thf ) (8a)
hexane. Yield: 90 mg (50%). IR (thin film: 1631 (m, ν(C᎐N))
᎐
cmϪ1. FAB mass spectrum (m/z): 659 ([M Ϫ Cl]ϩ), 624
([M Ϫ 2Cl]ϩ). Anal. calcd. for C40H46Cl2FeN3: C, 69.07; H,
6.67; N, 6.04; found: C, 69.11; H, 6.57; N, 6.19%. µeff (Evans’
NMR method) = 4.1 µB.
Thf (25 cm3) was added to 7a (0.35 g, 0.72 mmol) and the
n
mixture cooled to 0oC. BuLi (0.43 cm3, 2.5 M in hexane, 0.73
mmol) was then added at 0 ЊC, and the reaction mixture was
brought to rt and strirred for 1 h. The solvent was removed in
vacuo and the resulting yellow solid was suspended in pentane
(10 cm3) and stored at Ϫ78 ЊC for 5 h. The supernatant solution
was isolated by filtration and the residue was dried in vacuo to
(1,8-Diphenylimino-3,6-dimethylcarbazolide)FeCl2 (9c)
Sodium hydride (940 mg, 39.0 mmol) and 7c (1.63 g) were
placed in a Schlenk flask, thf (40 cm3) added and the reaction
D a l t o n T r a n s . , 2 0 0 3 , 2 7 1 8 – 2 7 2 7
2724

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mixture stirred at 65 ЊC for 16 h. After cooling to rt the result-
ing deep orange solution was isolated by filtration and added
to a solution of FeCl3 (659 mg, 4.1 mmol) in thf (20 cm3).
The reaction mixture was stirred at rt for 16 h. The solvent
was then removed under reduced pressure and the residue was
extracted with dichloromethane. The resultant solution was
concentrated to 10 cm3 and the product was precipitated by
addition of pentane (60 cm3). The residue was isolated by
filtration, washed with diethyl ether (2 × 30 cm3) and dried
in vacuo to give the product as a brown, microcrystalline solid.
Yield: 1.83 g (85%). Crystals suitable for X-ray analysis were
grown from a concentrated dichloromethane solution layered
with pentane. 1H NMR (250 MHz, CD2Cl2, rt, all peaks appear
as broad singlets): δ (ppm) Ϫ19.0 (2H), 29.7 (10H), 31.2
(1,8-Diphenylimino-3,6-dimethylcarbazolide)FeCl(MeCN)-
SbF6 (11)
Silver hexafluoroantimonate (124 mg, 0.36 mmol) and 9c
(190 mg, 0.36 mmol) were dissolved in MeCN (30 cm3). After
stirring at rt for 16 h, the solvent was removed under reduced
pressure and the residue was extracted with dichloromethane.
After evaporation of the solvent, the residue was washed with
diethyl ether (2 × 30 cm3) and dried in vacuo to give the product
as a dark brown, microcrystalline solid. Yield: 140 mg (51%).
1H NMR (250 MHz, CD2Cl2, rt, all peaks appear as broad
singlets): δ (ppm) Ϫ7.2 (2H), 19.9 (10H), 21.3 (2H), 55.0 (2H),
93.1 (6H). IR (thin film): 1626 (w, ν(C᎐N), 658 (s, ν(SbF ) cmϪ1
.
᎐
6
UV/VIS (CH2Cl2): λmax [nm] (εmax [dm3 molϪ1 cmϪ1]) = 411
(12000), 345 (16000), 299 (20000), 240 (46000). FAB mass spec-
trum (m/z): 491 ([M Ϫ SbF6]ϩ–MeCN), 456 ([M Ϫ SbF6]ϩ–
MeCN–Cl). Anal. calcd. for C30H25ClF6FeN4Sb: C, 46.88; H,
3.28; N, 7.29; found: C, 47.00; H, 3.15; N, 7.15%. µeff (Evans’
NMR method) = 6.3 µB.
(2H), 91.1 (2H), 105.4 (6H). IR (KBr): 1628 (w, ν(C᎐N))
᎐
cmϪ1. UV/VIS (CH2Cl2): λmax [nm] (εmax [dm3 molϪ1 cmϪ1]) =
621 (1700), 378 (13300), 300 (22500), 234 (50000). FAB mass
spectrum (m/z): 527 (Mϩ), 491 ([M Ϫ Cl]ϩ, 456 ([M Ϫ 2Cl]ϩ).
Anal. calcd. for C28H22Cl2FeN3: C, 63.78; H, 4.21; N, 7.97;
found: C, 63.82; H, 4.17; N, 7.88%. µeff (Evans’ NMR method)
= 4.8 µB.
(1,8-Diphenylimino-3,6-dimethylcarbazolide)Fe(acac)SbF6 (12)
Silver hexafluoroantimonate (127 mg, 0.37 mmol) and 9c
(195 mg, 0.37 mmol) were dissolved in MeCN (40 cm3) and
stirred at rt for 6 h. The reaction mixture was then added to a
suspension of silver acetylacetonate (76 mg, 0.37 mmol) in
MeCN (10 cm3). After stirring at rt for 16 h the solution was
isolated by filtration and the solvent was removed under
reduced pressure. The residue was then washed with 4 × 30 cm3
diethyl ether, and dried in vacuo to give the product as a
dark green, microcrystalline solid. Yield: 220 mg (75%). IR
(1,8-Diisopropylimino-3,6-dimethylcarbazolide)FeCl2 (9d)
An analogous procedure to that employed for 9c, but using
ligand precursor 7d, gave 9d as a green, microcrystalline solid in
1
57% yield. H NMR (250 MHz, CD2Cl2, rt, all peaks appear
as broad singlets): δ (ppm) 27.6 (2H), 31.9 (12H), 83.6 (4H),
101.2 (6H). IR (thin film): 1633 (w, ν(C᎐N)) cmϪ1. FAB mass
᎐
spectrum (m/z): 458 (Mϩ), 423 ([M Ϫ Cl]ϩ, 388 ([M Ϫ 2Cl]ϩ).
Anal. calcd. for C22H26Cl2FeN3: C, 57.54; H, 5.71; N, 9.15;
found: C, 57.53; H, 5.72; N, 8.97%. µeff (Evans’ NMR method)
= 5.5 µB.
(thin film): 1628 (w, ν(C᎐N)), 1557 (m, ν(C᎐C) ϩ ν(C᎐O)),
᎐
᎐
᎐
᎐
1527 (m, ν(C᎐C) ϩ ν(C᎐O)), 658 (s, ν(SbF )) cmϪ1. UV/VIS
᎐
6
(CH2Cl2): λmax [nm] (εmax [dm3 molϪ1 cmϪ1]) = 670 (1900), 394
(12000), 328 (16000), 281 (24500), 232 (48000). FAB mass
spectrum (m/z): 555 ([M Ϫ SbF6]ϩ), 456 ([M Ϫ SbF6]ϩ–acac).
Anal. calcd. for C30H25ClF6FeN4Sb: C, 50.10; H, 3.69; N,
5.31; found: C, 50.21; H, 3.70; N, 5.26%. µeff (Evans’ NMR
method) = 4.2 µB.
(1,8-Diphenylimino-3,6-dimethylcarbazolide)CoCl (10a)
An analogous procedure to that employed for 9c, but using
ligand precursor 7c and CoCl2, gave 10a as a red, micro-
1
crystalline solid in 31% yield. H NMR (250 MHz, CD2Cl2,
rt, all peaks appear as broad singlets): δ (ppm) Ϫ28.7
(4H), Ϫ8.58 (2H), 10.7 (4H), 20.8 (2H), 42.3 (6H), 47.0 (2H).
(1,8-Diphenylimino-3,6-dimethylcarbazolide)FeMe2 (13)
IR (KBr): 1632 (w, ν(C᎐N)) cmϪ1. UV/VIS (CH2Cl2): λmax
᎐
To a solution of 9c (205 mg, 0.39 mmol) in thf (30 cm3) was
added dropwise methyl lithium (490 µl, 1.6 M in Et2O, 0.78
mmol) at Ϫ78 ЊC. Upon completion of the addition, the reac-
tion mixture was allowed to warm to ambient temperature and
was stirred for a further 1 h. The solvent was then removed
under reduced pressure and the residue was extracted with tolu-
ene. The resulting toluene solution was pumped to dryness and
the residue washed with pentane (10 cm3). After drying in vacuo
the product was obtained as a dark brown solid. Yield: 80 mg
[nm] (εmax [dm3 molϪ1 cmϪ1]) = 438 (10500), 329 (20000), 289
(21000), 236 (40500). FAB mass spectrum (m/z): 494 (Mϩ), 459
([M Ϫ Cl]ϩ). Anal. calcd. for C28H22ClCoN3: C, 67.96; H, 4.48;
N, 8.49; found: C, 67.76; H, 4.32; N, 8.71%. µeff (Evans’ NMR
method) = 4.5 µB.
(1,8-Diphenylimino-3,6-dimethylcarbazolide)FeCl (10b)
An analogous procedure to that employed for 9c, but using
ligand precursor 7c and FeCl2, gave 10b as a green, micro-
crystalline solid in 45% yield. 1H NMR (250 MHz, CD2Cl2, rt,
all peaks appear as broad singlets): δ (ppm) Ϫ6.5 (2H), 16.5
(10H), 25.4 (2H), 28.9 (6H), 51.6 (2H). IR (KBr): 1628 (w,
(42%). IR (thin film) 1632 (w, ν(C᎐N)) cmϪ1. FAB mass spec-
᎐
trum (m/z): 472 ([M Ϫ Me]ϩ), 456 ([M Ϫ 2Me]ϩ). Anal. calcd.
for C30H28FeN3: C, 74.08; H, 5.80; N, 8.64; found: C, 73.96; H,
5.73; N, 8.72%. µeff (Evans’ NMR method) = 1.8 µB.
ν(C᎐N)) cmϪ1. UV/VIS (CH2Cl2): λmax [nm] (εmax [dm3 molϪ1
᎐
cmϪ1]) = 646 (630), 570 (1000), 423 (10500), 362 (10000), 299
(12500), 231 (40000). FAB mass spectrum (m/z): 456 ([M Ϫ
Cl]ϩ). Anal. calcd. for C28H22ClFeN3: C, 68.38; H, 4.51; N, 8.54;
found: C, 68.42; H, 4.58; N, 8.54%. µeff (Evans’ NMR method)
= 5.1 µB.
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethylcarbazolide)-
Co(MeCN)SbF6 (14)
Silver hexafluoroantimonate (107 mg, 0.31 mmol) and 10a
(180 mg, 0.31 mmol) were dissolved in MeCN (30 cm3). After
stirring at rt for 16 h the solvent was removed under
reduced pressure and the residue extracted with dichloro-
methane. The resultant solution was then concentrated to 5 cm3
and the product precipitated by the addition of pentane
(50 cm3). The solid was isolated by filtration and dried in vacuo
to give the product as a dark red, microcrystalline solid. Yield:
120 mg (43%). 1H NMR (250 MHz, CD2Cl2, rt, all peaks
appear as broad singlets): δ (ppm) Ϫ6.2 (12H), Ϫ2.6 (2H), 3.0
(1,8-Diphenylimino-3,6-dimethylcarbazolide)MnCl (10c)
An analogous procedure to that employed for 9c, but using
ligand precursor 7c and MnCl2, gave 10c as an orange, micro-
crystalline solid in 48% yield. IR (KBr): 1629 (w, ν(C᎐N)) cmϪ1
.
᎐
UV/VIS (CH2Cl2): λmax [nm] (εmax [dm3 molϪ1 cmϪ1]) = 455
(12500), 353 (13500), 302 (15000), 239 (48000). FAB mass spec-
trum (m/z): 455 ([M Ϫ Cl]ϩ). Anal. calcd. for C28H22ClMnN3:
C, 68.51; H, 4.52; N, 8.56; found: C, 68.69; H, 4.42; N, 8.69%.
µeff (Evans’ NMR method) = 4.6 µB.
(12H), 7.9 (4H), 9.9 (2H). IR (KBr): 1631 (m, ν(C᎐N)), 660 (s,
᎐
ν(Sb–F)) cmϪ1. FAB mass spectrum (m/z): 543 ([M Ϫ SbF6]ϩ–
MeCN). Anal. calcd. for C36H37CoF6N4Sb: C, 52.71; H, 4.55;
D a l t o n T r a n s . , 2 0 0 3 , 2 7 1 8 – 2 7 2 7
2725

View Article Online
N, 6.83; found: C, 52.49; H, 4.40; N, 6.73%. µeff (Evans’ NMR
method) = 2.2 µB.
with ethylene, and the contents were magnetically stirred
and maintained under ethylene (1 bar) throughout the poly-
merisation run. Releasing the ethylene pressure and adding
aqueous HCl and methanol terminated the runs.
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethylcarbazolide)-
CoCl2 (15)
Benzyl chloride (360 µl, 3.2 mmol) was added dropwise to a
solution of 10a (185 mg, 0.32 mmol) in toluene (20 cm3). After
stirring at rt for 48 h the solution was isolated by filtration and
concentrated to 10 cm3. This solution was then layered with
pentane (30 cm3) and stored at Ϫ20 ЊC, upon which the product
crystallised as dark red crystals. Yield: 25 mg (13%). 1H NMR
(250 MHz, CD2Cl2, rt, all peaks appear as broad singlets):
δ (ppm) Ϫ16.1 (12H), 10.9 (4H), 18.5 (6H), 21.8 (2H), 42.3
X-ray crystallography
Crystal data for 7a
¯
C34H35N3, M = 485.7, triclinic, P1 (no. 2), a = 8.538(1),
b = 11.096(1), c = 15.042(1) Å, α = 86.82(1), β = 75.43(1),
γ = 81.57(1)Њ, V = 1364.1(1) Å3, Z = 2, Dc = 1.182 g cmϪ3
,
µ(Cu-Kα) = 0.53 mmϪ1, T = 293 K, pale yellow prisms; 4056
independent measured reflections, F 2 refinement, R1 = 0.055,
wR2 = 0.144, 3197 independent observed reflections [|Fo| >
4σ(|Fo|), 2θmax = 120Њ], 339 parameters.
(6H), 49.4 (2H). IR (thin film): 1626 (m, ν(C᎐N)) cmϪ1. FAB
᎐
mass spectrum (m/z): 578 ([M Ϫ Cl]ϩ), 543 ([M Ϫ 2Cl]ϩ). Anal.
calcd. for C34H34Cl2CoN3: C, 66.46; H, 5.58; N, 6.84; found: C,
66.60; H, 5.38; N, 6.85%. µeff (Evans’ NMR method) = 4.9 µB.
Crystal data for 9c
¯
C28H22N3Cl2Fe, M = 527.2, triclinic, P1 (no. 2), a = 9.477(1),
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethylcarbazolide)-
CoMe (16a)
b = 11.460(1), c = 11.741(1) Å, α = 94.90(1), β = 101.51(1),
γ = 97.38(1)Њ, V = 1231.1(1) Å3, Z = 2, Dc = 1.422 g cmϪ3
,
To a solution of 10a (211 mg, 0.36 mmol) in thf (30 cm3) was
added dropwise methyl lithium (230 µl, 1.6 M in Et2O, 0.36
mmol) at Ϫ78 ЊC. Upon completion of the addition, the reac-
tion mixture was allowed to warm to ambient temperature and
was stirred for a further hour. The solvent was then removed
under reduced pressure and the residue was extracted with tolu-
ene. The resulting toluene solution was concentrated to 5 cm3
and layered with pentane (30 cm3). After storage at Ϫ20 ЊC the
µ(Cu-Kα) = 7.07 mmϪ1, T = 293 K, deep red prisms; 3649
independent measured reflections, F 2 refinement, R1 = 0.045,
wR2 = 0.103, 2962 independent observed absorption corrected
reflections [|Fo| > 4σ(|Fo|), 2θmax = 120Њ], 284 parameters.
CCDC reference numbers 204103–204104.
See http://www.rsc.org/suppdata/dt/b3/b301902k/ for crystal-
lographic data in CIF or other electronic format.
1
product crystallised as brown crystals. Yield: 80 mg (40%). H
Acknowledgements
NMR (250 MHz, CD2Cl2, rt, all peaks appear as broad sing-
lets): δ (ppm) Ϫ13.7 (12H), 17.5 (6H), 40.3 (6H). IR (thin film):
The authors are grateful to BP Chemicals Ltd. for financial
support and Crompton Corp. for the donation of MAO.
Dr. S. Carling at the Royal Institution of Great Britian,
London, and Dr. A. Oduwole at Queen Mary and Westfield,
University of London, are thanked for the SQUID magnet-
ometry and EPR measurements, respectively.
1630 (w, ν(C᎐N)) cmϪ1. FAB mass spectrum (m/z): 557 (Mϩ),
᎐
543 ([M Ϫ CH3]ϩ). Anal. calcd. for C35H37CoN3: C, 75.25; H,
6.68; N, 7.52; found: C, 75.06; H, 6.79; N, 7.64%. µeff (Evans’
NMR method) = 2.9 µB.
(1,8-Bis(2,4,6-trimethylphenylimino)-3,6-dimethylcarbazolide)-
FeMe (16b)
References
Employing an analogous procedure to that described above, but
using 10b, gave 16b as a red–brown, microcrystalline solid in
1 P. N. Riley, J. R. Parker, P. E. Fanwick and I. P. Rothwell,
Organometallics, 1999, 18, 3579; J. J. Garcia, A. L. Casado,
A. Iretskii, H. Adams and P. M. Maitlis, J. Organomet. Chem., 1998,
558, 189; R. Uson, L. A. Oro and J. A. Cabeza, Polyhedron, 1984, 3,
497; P. L. Pauson and A. R. Qazi, J. Organomet. Chem., 1967, 7, 321;
P. Longi and U. Nordio, Chim. Ind. (Milan), 1965, 47, 593;
P. N. Riley, R. D. Profilet, M. M. Salberg, P. E. Fanwick
and I. P. Rothwell, Polyhedron, 1998, 17, 773; M. A. Beswick,
C. N. Harmer, P. R. Raithby, A. Steiner, K. L. Verhorevoort and
D. S. Wright, J. Chem. Soc., Dalton Trans., 1997, 2029; P. N. Riley,
P. E. Fanwick and I. P. Rothwell, Chem. Commun., 1997, 1109;
P. N. Riley, R. D. Profilet, P. E. Fanwick and I. P. Rothwell,
Organometallics, 1996, 15, 5502; R. D. Profilet, P. E. Fanwick and I.
P. Rothwell, Polyhedron, 1992, 11, 1559; R. D. Profilet, P. E. Fanwick
and I. P. Rothwell, Angew. Chem., Int. Ed. Engl., 1992, 31, 1261;
P. N. Riley, P. E. Fanwick and I. P. Rothwell, J. Chem. Soc.,
Dalton Trans., 2001, 181; W. D. Jones, L. Z. Dong and A. W. Myers,
Organometallics, 1995, 14, 855.
2 U. Giannini, P. Longi, D. Deluca and B. Pivotto, (Montecatini
Edison S.p.A.), German Patent, DE2030753, 1971 [Chem. Abstr.
74:112626]; J.-C. Liu, (Equistar Chemicals, L.P., USA), PCT Int.
Appl. WO0242314, 2002 [Chem. Abstr. 137:6586]; B. P. Etherton and
S. Nagy (Occidental Chemical Corporation, USA), PCT Int. Appl.
WO9620223, 1996 [Chem. Abstr. 125:168924].
3 G. J. P. Britovsek, V. C. Gibson, O. D. Hoarau, S. K. Spitzmesser,
A. J. P. White and D. J. Williams, Inorg. Chem., 2003, in press.
4 G. J. P. Britovsek, M. Bruce, V. C. Gibson, B. S. Kimberley,
P. J. Maddox, S. Mastroianni, S. J. McTavish, C. Redshaw,
G. A. Solan, S. Strömberg, A. J. P. White and D. J. Williams,
J. Am. Chem. Soc., 1999, 121, 8728.
68% yield. IR (thin film): 1633 (m, ν(C᎐N)) cmϪ1. FAB mass
᎐
spectrum (m/z): 556 (Mϩ), 540 ([M Ϫ CH3]ϩ). Anal. calcd. for
C35H37FeN3: C, 75.67; H, 6.71; N, 7.56; found: C, 75.53; H,
6.81; N, 7.52%. µeff (Evans’ NMR method) = 3.0 µB.
High-throughput polymerisation screening at atmospheric
ethylene pressure
In a nitrogen atmosphere glove box, 5 µmol of pre-catalyst was
weighed into an 8 cm3 sample vial and 2 cm3 of the co-catalyst
solution was added (MAO, 10 wt% in toluene, Me2AlCl, 1.0 M
in hexane or Me3Al, 0.025 M in toluene). After weighing the
filled sample vials they were placed into a rack holding 24 such
vials in a Radleys Greenhouse reactor. The reactor was closed
and purged with ethylene outside the glove box. A mercury
bubbler was used to maintain one atmosphere pressure of
ethylene throughout the 30 min run time. When the poly-
merisation reaction was carried out at 80 ЊC, the Greenhouse
reactor was heated to the desired temperature over a period of
10 min prior to the addition of ethylene. Replacing the ethylene
atmosphere in the reactor by nitrogen using several pump–refill
cycles terminated the runs. The reactor was then transferred
back into the glove box and the sample vials were re-weighed to
determine the polymer yield.
Schlenk-line 1 bar ethylene tests
The pre-catalyst was dissolved in toluene (120 cm3) and a solu-
tion of the co-catalyst was added. The Schlenk tube was purged
5 N. G. Buu-Hoi and P. Cagniant, Chem. Ber., 1944, 77, 121;
F. A. Neugebauer and H. Fischer, Chem. Ber., 1972, 105, 2686.
6 J. Dabrowski, Z. Swistun and U. Dabrowska, Tetrahedron, 1973, 29,
2257.
D a l t o n T r a n s . , 2 0 0 3 , 2 7 1 8 – 2 7 2 7
2726

View Article Online
7 E. Balogh-Hergovich, G. Speier, B. Tapodi, M. Reglier and
M. Giorgi, Z. Kristallogr.-New Cryst. Struct., 1999, 214, 579.
8 G. J. P. Britovsek, V. C. Gibson, S. K. Spitzmesser, K. P. Tellmann,
A. J. P. White and D. J. Williams, J. Chem. Soc., Dalton Trans., 2002,
1159.
9 R. C. Kerber, in Comprehensive Organometallic Chemistry, ed. E. H.
Abel, F. G. Stone and G. Wilkinson, Pergamon Press, Oxford, 2nd
edn., 1995, vol. 7, p. 101.
23 R. L. Carlin and A. J. van Duyneveldt, Magnetic Properties of
Transition Metal Complexes, Springer-Verlag, New York, 1st edn.,
1977.
24 J. D. Walker and R. Poli, Inorg. Chem., 1989, 28, 1793.
25 M. D. Fryzuk, D. B. Leznoff, E. S. F. Ma, S. J. Rettig and V. G.
Young, Organometallics, 1998, 17, 2313.
26 C. A. Reed and F. Guiset, J. Am. Chem. Soc., 1996, 118, 3281;
E. L. Bominaar and R. Block, J. Chem. Phys., 1991, 95,
6712; M. M. Maltempo, J. Chem. Phys., 1974, 61, 2540; S. Mitra,
V. R. Marathe and R. Birdy, Chem. Phys. Lett., 1983, 96, 103.
27 D. Mansuy, I. Morgensternbadarau, M. Lange and P. Gans,
Inorg. Chem., 1982, 21, 1427; G. E. Toney, L. W. Terhaar,
J. E. Savrin, A. Gold, W. E. Hatfield and R. Sangaiah,
Inorg. Chem., 1984, 23, 2561; H. Ogoshi, H. Sugimoto, E. Watanabe,
Z. Yoshida, Y. Maeda and H. Sakai, Bull. Chem. Soc. Jpn., 1981, 54,
3414.
28 B. J. Kennedy, K. S. Murray, P. R. Zwack, H. Homborg and W. Kalz,
Inorg. Chem., 1986, 25, 2539; H. Goff and H. Shimomura,
J. Am. Chem. Soc., 1980, 102, 31; R. J. Cheng, P. Y. Chen, P. R. Gau,
C. C. Chen and S. M. Peng, J. Am. Chem. Soc., 1997, 119, 2563;
A. D. Boersma and H. M. Goff, Inorg. Chem., 1982, 21, 581;
H. Masuda, T. Taga, K. Osaki, H. Sugimoto, Z. Yoshida and
H. Ogoshi, Inorg. Chem., 1980, 19, 950.
29 A. Abragam and B. Bleaney, Electron Paramagnetic Resonance of
Transition Ions, Clarendon Press, Oxford, 1st edn., 1970.
30 R. V. Parish, NMR, NQR, EPR and Mossbauer Spectroscopy in
Inorganic Chemistry, Ellis Harwood, London, 1st edn., 1990.
31 A. de Koster, J. A. Kanters, A. L. Spek, A. A. H. Vanderzeijden,
G. van Koten and K. Vrieze, Acta Crystallogr., Sect. C, 1985, 41,
893.
10 V. L. Goedken, S. Peng and Y. Park, J. Am. Chem. Soc., 1974, 96,
284.
11 F. Calderazzo and C. Floriani, Chem. Commun., 1968, 417;
C. Floriani and F. Calderazzo, J. Chem. Soc. A, 1971, 3665.
12 D. A. Clarke, R. Grigg and A. W. Johnson, Chem. Commun., 1966,
208; D. A. Clarke, D. Dolphin, R. Grigg, A. W. Johnson and
H. A. Pinnock, J. Chem. Soc. C, 1968, 881; C. A. Reed, T. Mashiko,
S. P. Bentley, M. E. Kastner, W. R. Scheidt, K. Spartalian and
G. Lang, J. Am. Chem. Soc., 1979, 101, 2948; P. Battioni, J. P. Mahy,
G. Gillet and D. Mansuy, J. Am. Chem. Soc., 1983, 105, 1399;
P. Doppelt, Inorg. Chem., 1984, 23, 4009.
13 A. Tabard, P. Cocolios, G. Lagrange, R. Gerardin, J. Hubsch,
C. Lecomte, J. Zarembowitch and R. Guilard, Inorg. Chem., 1988,
27, 110; R. Guilard, B. Boisselier-Cocolios, A. Tabard, P. Cocolios,
B. Simonet and K. M. Kadish, Inorg. Chem., 1985, 24, 2509.
14 M. D. Fryzuk, D. B. Leznoff, R. C. Thompson and S. J. Rettig,
J. Am. Chem. Soc., 1998, 120, 10126.
15 I. Bertini and C. Luchinat, NMR of Paramagnetic Molecules in
Biological Systems, The Benjamin Cummings Publishing Company,
Inc., Menlo Park, CA, 1st edn., 1986.
16 J. Fabian, M. Legrand and P. Poirer, Bull. Soc. Chim. Fr., 1956, 23,
1499.
17 K. Nakamoto, Infrared and Raman Spectra of Inorganic
Coordination Compounds, Wiley, New York, 4th edn., 1989.
18 J. Reedijk, A. P. Zuur and W. Groeneveld, Recl. Trav. Chim. Pays-
Bas, 1967, 86, 1127; R. A. Walton, Spectrochim. Acta, 1965, 21,
1795.
19 A. I. Popov, A. V. Scharabarin, V. F. Sukhoverkhov and N. A.
Tchumaevsky, Z. Anorg. Allg. Chem., 1989, 576, 242.
20 R. R. Gagne, W. A. Marritt, D. N. Marks and W. O. Siegl,
Inorg. Chem., 1981, 20, 3260.
21 J. A. Broomhead and F. P. Dwyer, Aust. J. Chem., 1961, 250.
22 A. Yamamoto, K. Morifuji, S. Ikeda, T. Saito, Y. Uchida and
A. Misono, J. Am. Chem. Soc., 1968, 90, 1878; W. Lau, J. C.
Huffman and J. K. Kochi, Organometallics, 1982, 1, 155.
32 R. Souane, F. Isel, F. Peruch and P. J. Lutz, C. R. Chim., 2002, 5, 43;
R. Schmidt, M. B. Welch, S. J. Palackal and H. G. Alt, J. Mol. Catal.
A: Chem., 2002, 179, 155; C. Amort, M. Malaun, A. Krajete,
H. Kopacka, K. Wurst, M. Christ, D. Lilge, M. O. Kristen and
B. Bildstein, Appl. Organomet. Chem., 2002, 16, 506; J. Ramos,
V. Cruz, A. Munoz-Escalona and J. Martinez-Salazar, Polymer,
2002, 43, 3635.
33 A. G. Massay and A. J. Park, J. Organomet. Chem., 1964, 2, 245;
A. N. Chernega, A. J. Graham, M. L. H. Green, J. Haggitt,
J. Lloyd, C. P. Mehnert, N. Metzler and J. Souter, J. Chem. Soc.,
Dalton Trans., 1997, 2293.
34 M. Brookhart, B. Grant and A. F. Volpe, Organometallics, 1992, 11,
3920.
D a l t o n T r a n s . , 2 0 0 3 , 2 7 1 8 – 2 7 2 7
2727