Iron and cobalt ethylene polymerization catalysts: Variations on the central donor

Article abstract of DOI:10.1021/ic034040q

Three classes of ligands, designed to explore the effect of variations on the central pyridine donor core in bis(imino)pyridine iron and cobalt ethylene polymerization catalysts of the general formula [LMCl₂] (M = Fe or Co), have been prepared.

Full text of DOI:10.1021/ic034040q

Inorg. Chem. 2003, 42, 3454−3465
Iron and Cobalt Ethylene Polymerization Catalysts: Variations on the
Central Donor
George J. P. Britovsek, Vernon C. Gibson,* Olivier D. Hoarau, Stefan K. Spitzmesser,
Andrew J. P. White, and David J. Williams
Department of Chemistry, Imperial College, South Kensington, London SW7 2AY, U.K.
Received January 15, 2003
Three classes of ligands, designed to explore the effect of variations on the central pyridine donor core in bis-
(imino)pyridine iron and cobalt ethylene polymerization catalysts of the general formula [LMCl2] (M ) Fe or Co),
have been prepared. The first class comprises six-membered N-heterocycles (pyrimidine and triazine) and the
second class five-membered heterocycles (furan and thiophene) as the central donor core. In the third class of
ligands, the imine donor arm has been extended by one carbon to give anionic tridentate ligands based on carbazole
and neutral analogues based on dibenzofuran and dibenzothiophene. The coordination behavior of these ligands
upon reaction with FeCl2 or CoCl2 has been investigated, whereby only in the case of the neutral pyrimidine or the
anionic carbazolide unit as the central donor core have stable complexes been obtained. Ethylene polymerization
results are compared with the parent bis(imino)pyridine iron and cobalt catalyst systems.
Introduction
The search for well-defined transition-metal-based cata-
lysts for the polymerization of ethylene and R-olefins is an
area of intense current interest, both in academic and
industrial research laboratories. Compared to relatively ill-
defined Ziegler-Natta systems, a key advantage of well-
defined or single-site catalysts is the possibility for rational
ligand-oriented catalyst design, allowing better control over
polymer parameters such as molecular weight, polydispersity,
and tacticity.1 While many of the catalysts developed over
the last 40 years are based on early transition metals, recent
developments have resulted in highly active late transition
metal catalysts.2-5 Key milestones have been the develop-
ment of Ni(II) and Pd(II) catalysts containing R-diimine
ligands6 and the bis(imino)pyridine Fe(II) and Co(II) cata-
lysts,7,8 both of which, upon activation with a cocatalyst such
Figure 1. Schematic overview of different ligand types.
as methyl aluminoxane (MAO), give highly active catalysts
for the polymerization of ethylene. Depending on the ligand
structure, polyethylene materials ranging from linear R-ole-
fins to high molecular weight polymers can be produced.
For the iron and cobalt systems of type I (Figure 1), we have
shown in a series of reports that ligand modifications result
in changes to the productivity of the catalysts and to the
molecular weight of the resultant polyolefins.9-13 As part of
our ongoing studies into structure-activity relationships
* Author to whom correspondence should be addressed. E-mail:
v.gibson@imperial.ac.uk.
(8) Britovsek, G. J. P.; Gibson, V. C.; Kimberley, B. S.; Maddox, P. J.;
McTavish, S. J.; Solan, G. A.; White, A. J. P.; Williams, D. J. Chem.
Commun. 1998, 849-850.
(9) Britovsek, G. J. P.; Bruce, M.; Gibson, V. C.; Kimberley, B. S.;
Maddox, P. J.; Mastroianni, S.; McTavish, S. J.; Redshaw, C.; Solan,
G. A.; Stro¨mberg, S.; White, A. J. P.; Williams, D. J. J. Am. Chem.
Soc. 1999, 121, 8728-8740.
(10) Britovsek, G. J. P.; Mastroianni, S.; Solan, G. A.; Baugh, S. P. D.;
Redshaw, C.; Gibson, V. C.; White, A. J. P.; Williams, D. J.; Elsegood,
M. R. J. Chem. Eur. J. 2000, 6, 2221-2231.
(11) Britovsek, G. J. P.; Gibson, V. C.; Mastroianni, S.; Oakes, D. C. H.;
Redshaw, C.; Solan, G. A.; White, A. J. P.; Williams, D. J. Eur. J.
Inorg. Chem. 2001, 431-437.
(1) Montagna, A. A.; Burkhart, R. M.; Dekmezian, A. H. CHEMTECH
1997, 26-31.
(2) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003, 103, 283-316.
(3) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int.
Ed. 1999, 38, 428-447.
(4) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. ReV. 2000, 100,
1169-1203.
(5) Mecking, S. Angew. Chem., Int. Ed. 2001, 40, 534-540.
(6) Johnson, L. K.; Killian, C. M.; Brookhart, M. J. Am. Chem. Soc. 1995,
117, 6414-6415.
(7) Small, B. L.; Brookhart, M.; Bennett, A. M. A. J. Am. Chem. Soc.
1998, 120, 4049-4050.
3454 Inorganic Chemistry, Vol. 42, No. 11, 2003
10.1021/ic034040q CCC: $25.00 © 2003 American Chemical Society
Published on Web 05/02/2003

Fe and Co Ethylene Polymerization Catalysts
Figure 2. Overview of ligands used in this study.
within this family of polymerization catalysts, we describe
here the effect of variations at the central donor core of the
ligand.
We have developed synthetic entries into three classes of
ligands (II-IV, Figure 1) based on various central donors.
These contain the heterocyclic cores pyrimidine, triazine,
carbazole, furan, and thiophene, as well as ether and thioether
central donors. Type II ligands contain a six-membered
heterocyclic core while ligands of type III involve a five-
membered heterocyclic donor core. Both are tridentate
ligands that form two five-membered chelate rings upon
coordination to a metal center. The third group, IV, contains
ligands that form two six-membered chelate rings when
coordinated to a metal center. The coordination behavior of
these ligands with FeCl2 and CoCl2 has been investigated,
and the catalytic properties of the complexes for the
polymerization of ethylene have been evaluated and com-
pared to those of the parent bis(imino)pyridine complexes
of type I.
Figure 3. Molecular structure of 1c.
Results and Discussion
by a known procedure from freshly prepared benzoylformyl
chloride15 and 6-methyl-2,4-bis(trimethylstannyl)pyrimidine
(eq 1, Scheme 1).16 The condensation of the diketone with
various anilines to give the bis(imino)pyrimidine ligands
1a-d proceeded smoothly using Si(OEt)4 as a dehydrating
agent in the presence of a catalytic amount of concentrated
H2SO4.17 Compounds 1a-d have been analyzed by NMR,
IR, and mass spectrometry, and in addition, the molecular
structure of ligand 1c was determined by X-ray crystal-
lography (Figure 3). In all examples known to date, bis-
(imino)pyridine compounds adopt an E,E configuration, both
in the solid state and in solution.18-21 By contrast, the bis-
Synthesis of Ligands and Complexes of Type II. A
series of ligands of type II (Figure 1) containing the
N-heterocycles pyrimidine (1a-d) and triazine (2a and 2b)
were targeted (see Figure 2). A key difference between these
ligands and their well-established pyridine analogues is the
lower basicities of the pyrimidine and triazine nitrogen
donors. For example, the pKa’s of protonated pyrimidine and
triazine are 1.1 and 1.0, respectively, whereas protonated
pyridine has a pKa of 5.2. This would be expected to lead to
a significant difference in donor strength and electron density
at the metal center.14
The bis(imino)pyrimidine ligands 1a-d were prepared
from 2,4-dibenzoyl-6-methylpyrimidine, which was obtained
(15) Ottenheijm, H. C. J.; De Man, J. H. M. Synthesis 1975, 163.
(16) Yamamoto, Y.; Ouchi, H.; Tanaka, T.; Morita, M. Heterocycles 1995,
41, 1275-1290.
(12) Britovsek, G. J. P.; Gibson, V. C.; Kimberley, B. S.; Mastroianni, S.;
Redshaw, C.; Solan, G. A.; White, A. J. P.; Williams, D. J. J. Chem.
Soc., Dalton Trans. 2001, 1639-1644.
(17) Love, B.; Ren, J. J. Org. Chem. 1993, 58, 5556-5557.
(18) Small, B. L.; Brookhart, M. Macromolecules 1999, 32, 2120-2130.
(19) Meehan, P. R.; Alyea, E. C.; Ferguson, G. Acta Crystallogr. 1997,
C53, 888-890.
(13) Britovsek, G. J. P.; Baugh, S. P. D.; Hoarau, O.; Gibson, V. C.; Wass,
D. F.; White, A. J. P.; Williams, D. J. Inorg. Chim. Acta 2003, 345,
279-291.
(14) Katritzky, A. R.; Pozharskii, A. F. Handbook of Heterocyclic
Chemistry; Pergamon: Amsterdam, 2000.
(20) Vance, A. L.; Alcock, N. W.; Heppert, J. A.; Busch, D. H. Inorg.
Chem. 1998, 37, 6912-6920.
Inorganic Chemistry, Vol. 42, No. 11, 2003 3455

Britovsek et al.
Scheme 1
(imino)pyrimidine derivative 1c is seen here to exist in the
solid state as the Z,Z isomer, a configuration that is clearly
not preorganized for coordination to a metal center in a
tridentate fashion. The molecule has pseudo C2 symmetry
about the N(1)‚‚‚C(4) vector of the pyrimidine ring: indeed,
in the crystal structure, there is 65:35 disorder observed for
the positions of N(3)/C(5) within this ring. The torsional
twists about the C(2)sC(7) and C(6)sC(8) bonds are ca.
61° and 83°, respectively, and those about N(7)sC(16) and
N(8)sC(34) are ca. 74° and 89°. The two CdN linkages
[C(7)sN(7) 1.287(3) Å, C(8)sN(8) 1.270(3) Å] are similar
to those seen in bis(imino)pyridine compounds.18-20 The only
intermolecular packing interaction of note is an edge-to-face
stacking of the C(33) and C(34) containing phenyl rings of
Ci related pairs of molecules; the centroid‚‚‚centroid separa-
tion is 4.99 Å.
Proton NMR spectra of 1a-d indicate the presence of a
mixture of interconverting isomers in solution. A set of
crystals of 1c, taken from the same batch as the single crystal
used for X-ray analysis, was dissolved in C6D6. The 1H NMR
spectrum at 25 °C shows the presence of two isomers in a
ratio of 6:1 (Figure S1a). The major species displays two
equally intense septets at 3.08 and 3.47 ppm, corresponding
to the two inequivalent methine protons of the isopropyl
substituents, and a singlet at 1.84 ppm for the 6-CH3
substituent. The same pattern, two smaller septets at 2.98
and 3.37 ppm and a singlet at 2.01 ppm, is observed for the
minor isomer. In addition, very weak signals at 1.80-1.90
ppm are observed, possibly due to other isomers. At 70 °C,
these separate sets of signals coalesce to three broad
(21) Orrell, K. G.; Osborne, A. G.; Sik, V.; Webba da Silva, M. J.
Organomet. Chem. 1997, 530, 235-246.
3456 Inorganic Chemistry, Vol. 42, No. 11, 2003

Fe and Co Ethylene Polymerization Catalysts
resonances (Figure S1b) indicating a fast interconversion
between the isomers at higher temperatures. This process is
reversible and suggests an E/Z isomerization via inversion
at the imine nitrogen(s).21,22
(imino)pyrrolide ligands, have been reported previously.24,25
Iron(II) and cobalt(II) complexes were prepared and char-
acterized, but for both metals, the bis(imino)pyrrolide acted
as a bidentate ligand through the pyrrolyl nitrogen and one
of the imine arms, most probably due to an insufficient
“reach” of the second imine arm. It is only for relatively
large metal ions that the bis(imino)pyrrolide ligand has been
found to bind in a tridentate fashion.26 We have explored
the possibility of introducing other neutral central donors
such as oxygen and sulfur. The bis(imino)furan and bis-
(imino)thiophene derivatives 3 and 4 (see Figure 2) can be
readily prepared from furan-2,5-dicarboxaldehyde27 or
thiophene-2,5-dicarboxaldehyde and 2,6-diispropylaniline (eq
4 in Scheme 1). The ligands were prepared in good yield
and fully characterized. However, no reaction between 3 or
4 with FeCl2 was observed in n-butanol or THF, at room
temperature or at elevated temperatures. Addition of a THF
solution of ligand 3 or 4 to a suspension of CoCl2 in THF
resulted in the formation of an intensely colored dark green
solution, from which in both cases a dark green product was
isolated. However, FAB-MS, IR, and 1H NMR spectra
showed no indication of the formation of a cobalt complex,
and only peaks attributable to the free ligand were observed.
Complexes of this type have been previously claimed but
were not fully characterized.28-31
The poor ligating properties of these two ligands are not
surprising. A substantial number of metal complexes with
ligands containing bis(imino)furan and bis(imino)thiophene
units have been reported, but these units have always been
part of a macrocyclic or multidentate ligand and in none of
the examples does the oxygen or sulfur atom coordinate to
the metal center.32-34 These observations are consistent with
the oxygen and sulfur atoms of the furan and thiophene core
of these ligands being rather poor donors. In addition, tri-
dentate ligation of these ligands containing a five-membered
central donor core will be disfavored due to insufficient
“reach” as already outlined for the bis(imino)pyrrolide
system.
Notwithstanding, the mixture of isomers observed for the
free ligands in solution does not prevent the formation of
bis(imino)pyrimidine iron(II) and cobalt(II) complexes. Iron
complexes [(ligand)FeCl2] of all ligands 1a-d were obtained
in good yield by mixing the appropriate bis(imino)pyrimidine
ligand with FeCl2 in hot n-butanol at 80 °C. For the ligands
1b and 1d, the cobalt complexes [(ligand)CoCl2] were
prepared via a similar procedure. However, unlike the iron
case, no reaction occurred between the bis(imino)pyrimidine
derivative 1c, containing 2,6-diisopropylphenyl substituents,
and CoCl2 in n-butanol at 80 °C. Since at this temperature
there is no significant barrier to E/Z isomerization, the
inability of 1c to coordinate to cobalt is likely to be a
consequence of the increased steric bulk of the isopropyl
groups, in combination with an intrinsically weaker metal-
ligand interaction compared to iron. All complexes were
analyzed by 1H NMR spectroscopy, elemental analysis, mass
spectrometry, and magnetic susceptibility measurements.
In order to introduce a different N-heterocyclic central unit,
two derivatives 2a and 2b containing a triazine core were
prepared (Figure 2). The dibenzoyl-triazine precursor for 2a
was prepared by the ruthenium catalyzed oxidation of bis-
(enamino)triazine with sodium periodate (see Scheme 1, eq
2).23 Condensation of dibenzoyl-triazine with 2 equiv of
2,4,6-trimethylaniline proceeded smoothly with the use of a
catalytic amount of TiCl4. In contrast to the bis(imino)-
1
pyrimidine ligands 1a-d, the H NMR spectrum of 2a
showed only a single isomer in solution. By analogy to the
conformational isomerism seen in the bis(imino)pyrimidine
ligands, it is likely that this bis(imino)triazine ligand exists
only as the Z,Z conformer.
Tris(imino)triazine compound 2b was prepared from the
reaction of the morpholino protected triazine with the
anilinium salt as depicted in eq 3 (Scheme 1). Also for
compound 2b, only a single isomer was observed by NMR.
In this case, because of the smaller hydrogen substituents in
this aldimine ligand compared to the phenyl groups in the
previous cases, this ligand most likely exists as the E,E,E
isomer. Whatever the exact geometry of these ligands, their
reactions with either FeCl2 or CoCl2 in n-butanol at 80 °C
did not yield [(ligand)MCl2] complexes, and only unreacted
ligand and metal chloride were recovered after workup. High
isomerization barriers to the conformer suited to coordination,
as well as the reduced basicities of these triazine ligands,
likely prevent the formation of metal complexes. Increasing
the reaction temperature to 120 °C resulted in decomposition
of the ligand.
Synthesis of Ligands and Complexes of Type IV. It was
envisaged that the problems encountered in coordinating
(24) Dawson, D. M.; Walker, D. A.; Thornton-Pett, M.; Bochmann, M. J.
Chem. Soc., Dalton Trans. 2000, 459-466.
(25) Tohi, Y.; Matsui, S.; Fujita, T. (Mitsui Chemicals, Inc.). EP 1004599,
2000.
(26) Matsuo, Y.; Mashima, K.; Tani, K. Organometallics 2001, 20, 3510-
3518.
(27) Chmielewski, P. J.; Latos-Grazynski, L.; Olmstead, M. M.; Balch, A.
L. Chem. Eur. J. 1997, 3, 268-278.
(28) Kristen, M. O.; Gonioukh, A.; Lilge, D.; Lehmann, S.; Bildstein, B.;
Amort, C.; Malaun, M. (BASF). WO 01/14391, 2001.
(29) Xu, W.; Wang, Q.; Wurz, R. P. (Nova Chemicals). EP 1046647, 2000.
(30) Tohi, Y.; Matsui, S.; Fujita, T. (Mitsui Chemicals, Inc.). EP 1004600,
2000.
(31) Amort, C.; Malaun, M.; Krajete, A.; Kopacka, H.; Wurst, K.; Christ,
M.; Lilge, D.; Kristen, M. O.; Bildstein, B. Appl. Organomet. Chem.
2002, 16, 506-516.
(32) Bailey, N. A.; Eddy, M. M.; Fenton, D. E.; Moss, S.; Mukhopadhyay,
A.; Jones, G. J. Chem. Soc., Dalton Trans. 1984, 2281.
(33) Yates, P. C.; Drew, M. G. B.; Trocha-Grimshaw, J.; McKillop, K. P.;
Nelson, S. M.; Ndifon, P. T.; McAuliffe, C. A.; Nelson, J. J. Chem.
Soc., Dalton Trans. 1991, 1973.
Synthesis of Ligands and Complexes of Type III. Metal
complexes containing ligands of type III (Figure 1) with a
five-membered N-heterocyclic core, i.e., monoanionic bis-
(22) van Asselt, R.; Elsevier, C. J.; Smeets, W. J. J.; Spek, A. L.; Benedix,
R. Recl. TraV. Chim. Pays-Bas 1994, 113, 88.
(23) Schulz, H.-J.; Liebscher, J.; Luger, P.; Quian, M.; Mulzer, J. J.
Heterocycl. Chem. 1992, 29, 1125.
(34) van Stein, G.; van Koten, G.; Blank, F.; Taylor, L. C.; Vrieze, K.;
Spek, A. L.; Duisenberg, A. J. M.; Schreurs, A. M. M.; Kojic-Prodic,
B. Inorg. Chim. Acta 1985, 98, 107-120.
Inorganic Chemistry, Vol. 42, No. 11, 2003 3457

Britovsek et al.
Scheme 2
ligands of type III in a tridentate manner may be overcome
by introducing an extra carbon atom linker between the imine
moiety and the central heterocyclic core. Thus, a series of
complexes with the general framework IV (Figure 1)
containing nitrogen, oxygen, and sulfur atoms as the central
donor (5-8, Figure 2) were synthesized. These can form
two six-membered chelate rings on coordination to a metal
center. In order to introduce a central nitrogen donor, the
bis(imino)carbazole 5 was synthesized as depicted in eqs 1-3
(Scheme 2). The starting material for the reaction sequence,
3,6-dibromocarbazole, is commercially available but can also
be prepared in quantitative yield by bromination of carbazole
with N-bromosuccinimide (NBS).35 Trimethylsilane was
chosen as the N-H protective group during the dilithiation
of 3,6-dibromocarbazole since it is readily removed during
the acidic workup. After quenching the dilithiated intermedi-
ate with methyliodide, 3,6-dimethylcarbazole can be obtained
in good yield as a white amorphous solid (eq 1). The
spectroscopic data and melting point (218-219 °C) cor-
respond well with previously published values.36,37 1,8-
Dibrominated carbazole can be synthesized by bromination
(35) Smith, K.; James, D. M.; Mistry, A. G.; Bye, M. R.; Faulkner, D. J.
Tetrahedron 1992, 48, 7479-7488.
(36) Wentrup, C.; Gaugaz, M. HelV. Chim. Acta 1971, 54, 2108-2111.
3458 Inorganic Chemistry, Vol. 42, No. 11, 2003

Fe and Co Ethylene Polymerization Catalysts
significantly shorter than those to N(14) and N(26) reflecting
the constraints of the tridentate ligand, and the formally
negatively charged nature of the central donor atom. The
3,6-dimethylcarbazole moiety has a slightly folded geometry,
its two phenyl rings being inclined by ca. 6°; the cobalt atom
is displaced by 0.35 Å out of the pyrrole ring plane. One of
the mesityl rings [that containing C(27)] is oriented es-
sentially orthogonally (ca. 80°) to its associated CoNC2 plane
whereas the other is rotated by only ca. 64° out of plane.
The two six-membered chelate rings both have folded
geometries with out of plane fold angles about N(1)‚‚‚N(14)
and N(1)‚‚‚N(26) of 18° and 25°, respectively. Centrosym-
metrically related pairs of molecules have their carbazole
ring systems in a π-stacking relationship, the centroid‚‚‚
centroid and mean interplanar separations between their
pyrrole rings being 3.85 and 3.35 Å, respectively. There are
no interactions involving the mesityl rings, the space between
their “jaws” being occupied by the included (disordered)
solvent toluene molecule.
Figure 4. Molecular structure of [(5)CoCl]. Selected bond lengths (Å)
and angles (deg): Co-Cl 2.226(2), Co-N(1) 1.912(4), Co-N(14) 2.067(4),
Co-N(26) 2.073(4), C(14)-N(14) 1.309(6), C(26)-N(26) 1.295(6),
N(1)-Co-N(14) 90.7(2), N(1)-Co-N(26) 89.3(2), N(14)-Co-N(26)
140.7(2), N(1)-Co-Cl 124.96(14), N(14)-Co-Cl 100.44(13), N(26)-
Co-Cl 111.47(12).
Oxygen and sulfur donors in the central part of ligand type
IV have been investigated in three types of ligands, the
dibenzofuran derivative 6 and the diphenyl ether and
thioether ligands 7 and 8 (Figure 2). A nitrogen analogue of
these latter ligand types, a bis(imino)diphenylamine ligand
and its corresponding iron(III) complex, has been reported
previously.38 The bis(imino)dibenzofuran derivative 6 was
synthesized from dibenzofuran dicarboxaldehyde39 and 2
equiv of the appropriate aniline under standard condensation
conditions. Addition of the ligand to an FeCl2 solution in
nBuOH at 80 °C did not result in the formation of a complex.
Removal of the solvent left the starting materials unreacted.
Reactions in other solvents such as THF and dichloromethane
were equally unsuccessful. This result was surprising con-
sidering the greater flexibility of this ligand compared to the
furan derivative 3 and a recent report of the reaction of a
similar bis(oxazoline)dibenzofuran ligand with Ni(II), which
did result in the formation of a stable Ni(II) complex.40 In
order to allow even more flexibility in the ligand framework,
we also synthesized the diphenyl ether and thioether deriva-
tives 7 and 8. A bis(oxazoline)diphenylthioether ligand
similar to 8 was recently reported,41 but no metal complexes
of either 7 or 8 have been reported. All attempts to form
metal complexes of 7 and 8 with FeCl2 or CoCl2 were
unsuccessful.
of 3,6-dimethylcarbazole with NBS with exclusion of light
in near quantitative yield (eq 2). Formylation of the 1,8-
dibromocarbazole can be achieved by quenching the 1,8-
dilithiated intermediate with excess anhydrous DMF. The
carbazole N-H proton is again protected with a trimethylsilyl
group prior to lithiation, and 1,8-diformyl-3,6-dimethylcar-
bazole is obtained in quantitative yield. Schiff-base conden-
sation of the dialdehyde with 2,4,6-trimethylaniline in
chloroform leads to the formation of the bis(imino)carbazole
5 in good yield (eq 3).
Deprotonation of the ligand can be achieved with NaH in
THF solution at 65 °C. The resulting sodium salt fluoresces
bright green in THF solution, but the fluorescence disappears
upon complexation to transition metals; this optical behavior
is a useful indicator for successful coordination of the ligand
to a transition metal center. After addition of a THF solution
of the sodium salt of 5 to FeCl2(THF)1.5 or CoCl2, the green
fluorescence disappears completely over 1-2 h. The isolated
iron and cobalt complexes [(5)FeCl] and [(5)CoCl] have been
analyzed by FAB-MS, 1H NMR and IR spectroscopy,
magnetic moment measurements, and elemental analysis. As
expected, these complexes are paramagnetic, with magnetic
moments corresponding to high spin configurations. Both
complexes show distinct resonances in the 1H NMR spectrum
comparable to the ones observed for bis(imino)pyridine iron-
(II) and cobalt(II) complexes.9 Crystals suitable for X-ray
analysis of cobalt complex [(5)CoCl] could be obtained from
a concentrated toluene solution. The crystal structure is
shown in Figure 4. The geometry around the cobalt center
is severely distorted and flattened tetrahedral, the N(1)-Co-
Cl and N(14)-Co-C(26) angles, for example, being
124.96(14)° and 140.7(2)°, respectively. Coordination is, as
expected, to all three nitrogen centers, the Co-N bond
lengths being unexceptional. The Co-N(1) distance is
Polymerization Results
The catalytic activity of the iron(II) and cobalt(II) com-
plexes of the ligands 1a-d and 5 for the polymerization of
ethylene has been evaluated under two sets of conditions.
Low-pressure Schlenk line tests were performed using 100
equiv of cocatalyst MAO, and high-pressure tests (4 bar)
(38) Matsui, S.; Nitabaru, M.; Tsuru, K.; Fujita, T.; Suzuki, Y.; Takagi,
Y.; Tanaka, H. (Mitsui Chemicals, Inc.). WO 99/54364, 1999.
(39) Skar, M. L.; Svendsen, J. S. Tetrahedron 1997, 53, 17425-17440.
(40) Kanemasa, S.; Oderaotoshi, Y.; Yamamoto, H.; Tanaka, J.; Wada,
E.; Curran, D. P. J. Org. Chem. 1997, 62, 6454-6455.
(41) Mugesh, G.; Singh, H. B.; Butcher, R. J. J. Chem. Res., Synop. 1999,
472-473.
(37) Kuroki, M.; Tsunashima, Y. J. Heterocycl. Chem. 1981, 18, 709-
714.
Inorganic Chemistry, Vol. 42, No. 11, 2003 3459

Britovsek et al.
Table 1. Results of Ethylene Polymerization Runs with Iron and Cobalt Precatalysts
activity
(g/mmol‚
bar‚h)
MAO,b
Mpk
sat. ends/ vinyl ends/ sat. ends/
run
1c [(1a)FeCl2]
[(1b)FeCl2]
3c [(1c)FeCl2]
complex
equiv P (bar) T (°C) yield (g)
R
Mn
Mw
peak1/peak2
PDI
1000C
1000C
vinyl ends
100
100
100
100
1
1
1
1
25
25
25
25
23.4
2340
2180
930
1300 14 000
1200 16 000
3800 130 000
900
900
10.3
12.9
11.60
12.76
6.38
8.90
10.44
1.45
1.30
1.22
4.40
2
21.80
4.65
2000/427 000 34.5
4
[(1d)FeCl2]
0.13d
4.78e
7.10
491
0.69
5
6
7
8
9
[(1a)FeCl2]
[(1b)FeCl2]
[(1b)FeCl2]
[(1b)FeCl2]
[(9)FeCl2]
1000
1000
1000
1000
1000
1000
1000
100
4
4
4
4
4
4
4
1
10
1
50
50
30
15
50
50
30
25
50
25
25
3550
3850
6200
5250
9600
490
1480
720
1340
1140
242
1600 50 000
1200 39 000
1400 66 000
1000 80 000
2900 38 000
5400 141 000
15000 182 000 153 000
9900 26 000 20 000
12000 30 000 22 000
16000 40 000 27 000
1000
1000
900
31.4
33.1
48.1
5.47
10.54
9.6
10.7
6.96
1.60
1.08
1.54
1.86
1.1
5.35
7.55
7.2
1.02
1.40
1.3
7.70
12.40
10.50
19.2
7.30
22.20
3.60
700/89 000 70.5
3300
2400/126 000 26.5
9.2
1.2
13.1
2.97
1.08
0.20
1.20
1.50
1.0
2.34
1.48
5.40
1.28
1.24
1.1
10 [(1c)FeCl2]
11 [(1c)FeCl2]
12c [(1b)CoCl2]
13 [(1b)CoCl2] 1000
14 [(9)CoCl2]
15 [(1d)CoCl2]
12.5
2.7
2.5
2.6
8.30
100
100
11.44
0.07d
2.35e
1
0.83
-
a General conditions, Schlenk tests at 1 bar: 100 mL of toluene, 100 equiv of MAO, 10 µmol of precatalyst, 1 h run. General conditions, reactor test:
isobutane solvent, 0.5 µmol of Fe catalyst or 0.6 µmol of Co catalyst, 1000 equiv of MAO, 1 h run. b Cocatalyst. c 30 min run. d Solid. e Liquid.
Figure 5. Ethylene uptake versus time for complexes [(1b)FeCl2] and [(9)FeCl2].
were carried out in a 1 L stainless steel reactor using 1000
equiv MAO. The results are summarized in Table 1.
decays much faster in the case of [(1b)FeCl2] compared to
[(9)FeCl2]. A similar trend is seen for the analogous cobalt
complexes [(1b)CoCl2] and [(9)CoCl2] (runs 12 and 14)
where the activity of the latter is almost double compared
to the pyrimidine derivative. It is also clear from runs 6
versus 7, and 10 versus 11, that reducing the temperature
leads to higher activities. We believe that this reduced
stability is a result of the weaker donor strength of pyrimidine
versus pyridine ligands. Activation of carbazolide complexes
[(5)FeCl] and [(5)CoCl] with MAO did not result in any
measurable ethylene polymerization activity under the above
Schlenk line conditions. In the case of bis(imino)carbazolide
complexes, neutral, rather than cationic, active species would
be expected which may lead to a much lower activity. It is
also possible that the extra “reach” of the imine donor arms
in 5 leads to greater steric hindrance at the potential active
site.
The first set of experiments (runs 1-4) shows the different
behavior of the bis(imino)pyrimidine iron catalysts under
Schlenk line conditions. The activities and polymer properties
of the 2,6-dimethyl and the 2,4,6-trimethyl derivatives ([(1a)-
FeCl2] and [(1b)FeCl2], respectively) are comparable, whereas
the 2,6-diisopropyl derivative [(1c)FeCl2] shows a lower
activity and yields higher molecular weight polymer, thereby
following the same trend as seen for bis(imino)pyridine iron
catalysts.9 This trend is also observed at higher pressure (4
bar) as can be seen from runs 5, 6, and 10. For comparison,
we have also prepared [(9)FeCl2], the bis(imino)pyridine
analogue of precatalyst [(1b)FeCl2] (see Figure 5 and run
9). Under the same conditions, the activity of this pyridine
derivative is almost three times higher compared to the
pyrimidine derivative [(1b)FeCl2] (runs 6 and 9). This lower
activity is believed to be due to the catalyst decomposing
under the conditions employed, as can be seen from the
activity profiles for runs 6 and 9 (ethylene uptake over time),
shown in Figure 5. The initial rapid ethylene consumption
The polymer data show that the iron catalysts afford
products with a bimodal distribution, the lower molecular
weight fraction arising from chain transfer to aluminum. By
contrast, the cobalt products show a unimodal product with
3460 Inorganic Chemistry, Vol. 42, No. 11, 2003

Fe and Co Ethylene Polymerization Catalysts
analysis was carried out in p-xylene-d10 at 110 °C and 13C NMR
analysis in C2D2Cl4/1,2,4-trichlorobenzene at 130 °C using a JEOL
GSX270 spectrometer. GPC analyses were carried out on a Waters
150CV (columns supplied by Shodex (807, 806 and 804)) using
polyethylene standard reference material NBS1484a.
a low polydispersity (Mw/Mn). This behavior is similar to
that observed for the bis(imino)pyridine analogues.9 End-
group analyses provide further confirmation of the similarities
between the pyridine and pyrimidine systems. For example,
more saturated end-groups than vinyl end-groups are found
in the case of iron due to chain transfer to aluminum, whereas
an approximate 1:1 ratio is observed in the case of cobalt,
indicating â-H transfer is the sole chain termination pathway.9
Reducing the steric bulk on the imine aryl substituents as in
the 2-methylphenyl derivatives [(1d)FeCl2] and [(1d)CoCl2]
results in the formation of low molecular weight oligomers,
consistent with observations made for bis(imino)pyridine
oligomerization systems.10
In conclusion, we have prepared three types of variation
on the central pyridine donor core in bis(imino)pyridine iron
and cobalt catalyst systems. The coordination behavior of
these new ligands with respect to iron(II) and cobalt(II) has
been investigated along with the polymerization behavior of
the resulting metal catalysts. In the case of six-membered
N-heterocyclic cores, only pyrimidine-based ligands afforded
complexes with FeCl2 or CoCl2. Ligands containing triazine
or five-membered heterocyclic cores (furan or thiophene) did
not react with FeCl2 or CoCl2, which has been attributed to
(i) the weaker donor strength of the central donor in these
ligands and (ii) in the case of the five-membered heterocycles
(furan and thiophene) the larger bite angle. The addition of
an extra carbon atom to each chelating arm was investigated
with a view to decreasing the bite angle and increasing the
overall donor strength of the ligand. However, only in the
case of an anionic nitrogen atom (carbazolide) as the central
donor were stable Fe(II) and Co(II) complexes obtained,
whereas sulfur- and oxygen-based ligands did not yield
isolable complexes. Pyrimidine-based complexes afforded
active polymerization catalysts upon activation with MAO,
although the activity was substantially reduced compared to
the pyridine analogues, probably due to reduced catalyst
stability under polymerization conditions.
Compounds 6-methyl-2,4-dichloropyrimidine, trimethyltin
chloride, benzoylformyl acid, tetraethyl orthosilicate, 2,5-thiophene-
dicarboxaldehyde, all anilines, cobalt(II) chloride, and iron(II)
chloride were purchased from Aldrich Chemical Co. Benzoylformyl
chloride was prepared according to a literature procedure,15 distilled,
and degassed prior to use. 6-Methyl-2,4-bis(trimethylstannyl)py-
rimidine and 2,4-dibenzoyl-6-methylpyrimidine were synthesized
following an established procedure.16 2,4-Bis(1-phenyl-2-morpholi-
noethen-1-yl)-6-benzyl-1,3,5-triazine,23 2,4,6-tris(dimorpholino-
methyl)-1,3,5-triazine,44 3,6-dibromo-9H-carbazole,35 2,5-furan-
dicarboxaldehyde,27 4,6-dibenzofuran-dicarboxaldehyde,39 bis(o-
46
formylphenyl)ether45 and FeCl2(THF)1.5 were prepared.
2,4-Bis[(2,6-dimethylphenylimino)benzyl]-6-methylpyrimi-
dine (1a). 2,4-Dibenzoyl-6-methylpyrimidine (262 mg, 0.86 mmol)
and 2,6-dimethylaniline (230 mg, 1.90 mmol) were combined and
treated with one drop of concentrated H2SO4. Si(OEt)4 (398 mg,
1.90 mmol) was added and the mixture placed in a flask equipped
with a still head. The solution was heated at 140 °C for 4 h. The
distillate (EtOH) was then discarded and the residue dissolved in
dichloromethane and washed with a saturated solution of NaHCO3,
followed by water. The dichloromethane solution was dried
(MgSO4), and the volatile components were removed under reduced
pressure. The crude product was triturated with cold ethanol and
further purified by flash chromatography on silica gel (ethyl acetate/
petroleum ether 2:8, Rf ) 0.55) and by recrystallization from Et2O
to yield yellow prisms (275 mg, 62%). Mp 129 °C. 1H NMR (250
MHz, C6D6, rt): δ (ppm) minor isomer 1.95 (s, 6H, o-CH3), 2.03
(s, 3H, CH3), 2.18 (s, 6H; o-CH3), 6.81-8.05 (m broad, 17H, Ar-
H); major isomer 1.62 (s, 3H, CH3), 2.08 (s, 6H, o-CH3), 2.33 (s,
6H, o-CH3), 6.19 (s, 1H, Pyr-H), 6.81-8.05 (m broad, 16H, Ar-
H). 13C NMR (63 MHz, CDCl3, rt): δ (ppm) 18.20, 18.35, 18.50,
24.05, 24.23, 162.46, 162.98, 163.37, 163.61, 164.07, 164.18,
167.01, 167.69. IR (KBr): 1635 (ν(CdN)), 1577 cm-1. MS (EI)
m/z: 508 (M+, 100%), 208 (80%). Anal. Calcd for C35H32N4: C,
82.64; H, 6.34; N, 11.01. Found: C, 82.71; H, 6.40; N, 11.08.
2,4-Bis[(2,4,6-trimethylphenylimino)benzyl]-6-methylpyrimi-
dine (1b). The same procedure as for 1a, using 2,4,6-trimethyl-
aniline and 2,4-dibenzoyl-6-methylpyrimidine, yielded compound
1b as yellow needles. Yield: 73%. Mp 200-202 °C. 1H NMR (250
MHz, CDCl3, rt): δ (ppm) minor isomer 1.87 (s, 6H, o-CH3), 1.91
(s, 6H, o-CH3), 2.19 (s, 3H, p-CH3), 2.20 (s, 3H, p-CH3), 2.58 (s,
3H, CH3), 6.58-7.78 (m, 15H, Ar-H); major isomer 2.01 (s, 6H,
o-CH3), 2.03 (s, 6H, o-CH3), 2.22 (s, 6H, p-CH3), 2.30 (s, 3H, CH3),
6.58-7.78 (m, 15H, Ar-H). 13C NMR (63 MHz, CDCl3, rt): δ
(ppm) 17.59, 18.16, 18.33, 18.51, 18.48, 18.51, 20.37, 20.73, 20.79,
20.83, 24.19, 24.29, 24.53, 24.66, 162.67, 163.54, 163.78, 163.45,
164.45, 164.59, 166.97, 167.62. IR (KBr): 1633 (ν(CdN)), 1577
cm-1. MS (EI) m/z: 536 (M+, 100%), 222 (46%). Anal. Calcd for
C37H36N4: C, 82.80; H, 6.76; N, 10.44. Found: C, 82.91; H, 6.73;
N, 10.45.
Experimental Section
General. All manipulations were carried out under an atmosphere
of nitrogen using standard Schlenk and cannula techniques or in a
conventional nitrogen-filled glovebox. Solvents were refluxed over
an appropriate drying agent, and distilled and degassed prior to
use. Elemental analyses were performed by the microanalytical
services of the Department of Chemistry at Imperial College, Medac
Ltd., or SACS at the University of North London. NMR spectra
were recorded on a Bruker spectrometer at 250 MHz (1H) and 62.9
MHz (13C) at 293 K; chemical shifts are referenced to the residual
protio impurity of the deuterated solvent. Mass spectra were
obtained using either fast atom bombardment (FAB), electron
impact (EI), or chemical ionization (CI). IR spectra were recorded
on a Perkin-Elmer Spectrum GX1 system. In some cases, thin
sample films were prepared by evaporating CH2Cl2 solutions of
the ligands or complexes on NaCl plates. Magnetic susceptibility
studies were performed using an Evans balance42 or the Evans NMR
method (solvent, CH2Cl2; reference, cyclohexane).43 Polymer NMR
and GPC analyses were performed at BP Chemicals Ltd. 1H NMR
(43) Britovsek, G. J. P.; Gibson, V. C.; Spitzmesser, S. K.; Tellmann, K.
P.; White, A. J. P.; Williams, D. J. J. Chem. Soc., Dalton Trans. 2002,
1159-1171.
(44) Sumera, F.; Le Rouzic, A.; Raphalen, D.; Kerfanto, M. J. Heterocycl.
Chem. 1987, 24, 793.
(45) Osuka, A.; Kobayashi, F.; Maruyama, K. Bull. Chem. Soc. Jpn. 1991,
64, 1213-1225.
(46) Calderazzo, F.; Englert, U.; Pampaloni, G.; Vanni, E. Comptes Rendus
Acad. Sci., Ser. II C 1999, 2, 311-319.
(42) Woolcock, J.; Zafar, A. J. Chem. Educ. 1992, 69, A176-A179.
Inorganic Chemistry, Vol. 42, No. 11, 2003 3461

Britovsek et al.
2,4-Bis[(2,6-diisopropylphenylimino)benzyl]-6-methylpyrimi-
dine (1c). The same procedure as for 1a, using 2,6-diisopropyl-
aniline and 2,4-dibenzoyl-6-methylpyrimidine, gave 1c as yellow
for C24H17N3O2: C, 75.98; H, 4.52; N, 11.07. Found: C, 75.86;
H, 4.61; N, 11.15.
2,6-Bis[(2,4,6-trimethylphenylimino)benzyl]-4-benzyl-1,3,5-
triazine (2a). In a Schlenk tube filled with nitrogen, a solution of
titanium tetrachloride (4.0 mL, 4 mmol, 1 M in toluene) was added
over 4 h to a mixture of 2,4,6-trimethylaniline (1.66 g, 12.30 mmol)
and bis(ketone) 11 in toluene/ether (15 mL/15 mL). Another portion
of trimethylaniline (0.5 g, 3.70 mmol) was added after 16 h,
followed by a slow addition (4 h) of TiCl4 (2.5 mL, 2.5 mmol, 1
M in toluene). After 48 h, the mixture was diluted with a saturated
solution of NaHCO3 (50 mL) and filtered on a Celite layer which
was washed copiously with toluene. The organic phase was
separated, dried over Na2SO4, and evaporated. The purification of
the crude product by flash chromatography on silica gel (ethyl
acetate/ petroleum ether: 15:85, Rf ) 0.40) gave a hygroscopic
yellow mousse. Yield 0.27 g (28%.). 1H NMR (250 MHz, CDCl3,
rt): δ (ppm) 1.96 (s, 12H, o-CH3), 2.22 (s, 6H, p-CH3), 3.96 (s,
2H, CH2), 6.58 (s, 4H, Ar-H), 6.93 (m, 2H, Ar-H), 7.22-7.52
(m broad, 13H, Ar-H). 13C NMR (63 MHz, CDCl3, rt): δ (ppm)
18.3 (CH3 ortho), 20.78 (CH3 para), 45.11 (CH2), 126.25, 126.77,
127.98, 128.34, 129.01, 131.381, 132.20, 135.10, 136.04, 140.11,
140.93, 145.40, 162.67 (CdN), 171.67 (NCCN), 177.89 (NCN).
IR (KBr): 1635 (ν(CdN)), 1523 cm-1. MS EI (m/z): 613 (M+,
100%), 222 (57%). Anal. Calcd for C42H39N5: C, 82.19; H, 6.40;
N, 11.41. Found: C, 82.29; H, 6.42; N, 11.50.
1
needles. Yield: 82%. H NMR (250 MHz, CDCl3, rt): δ (ppm)
minor isomer 0.86 (d, 3H, J ) 6.5 Hz, CHMe2), 0.91 (d, 3H, J )
6.5 Hz, CHMe2), 2.34 (s, 3H, CH3), 2.73 (septet, 1H, J ) 6.5 Hz,
CHMe2), 3.04 (septet, 1H, J ) 6.5 Hz, CHMe2), 6.85-7.51 (broad,
13H), 7.69 (s, 1H, Pyr-H), 7.89 (m, 2H, Ar-H); major isomer
0.98 (d, 3H, J ) 6.7 Hz, CHMe2), 1.00 (d, 3H, J ) 6.7 Hz, CHMe2),
1.09 (d, 3H, J ) 6.7 Hz, CHMe2), 1.10 (d, 3H, J ) 6.7 Hz, CHMe2),
2.54 (s, 3H, CH3 pyr), 2.95 (septet, 1H, J ) 6.7 Hz, CHMe2), 3.13
(septet, 1H, J ) 6.7 Hz, CHMe2), 6.68 (s, 1H, Pyr-H), 6.85-7.51
(broad m, 16H, Ar-H). 13C NMR (63 MHz, CDCl3, rt): δ (ppm)
21.03, 21.29, 21.74, 22.11, 23.37, 23.47, 23.57, 23.87, 24.15, 24.33,
28.28, 28.52, 162.47, 162.54, 162.58, 163.16, 164.25, 164.35,
166.45, 167.67. IR (KBr): 1626 (ν(CdN)), 1578 cm-1. MS (EI)
m/z: 620 (100%, M+), 359 (48%), 264 (72%). Anal. Calcd for
C43H48N4‚H2O: C, 80.84; H, 7.89; N, 8.77. Found: C, 80.16; H,
7.82; N, 9.13.
2,4-Bis[(2-methylphenylimino)benzyl]-6-methylpyrimidine (1d).
The same procedure as for 1a, using 2-methylaniline and 2,4-
dibenzoyl-6-methylpyrimidine, gave 1d as yellow needles. Yield:
72%. 1H NMR (250 MHz, CDCl3, rt): δ (ppm) minor isomer 2.07
(s, 3H, o-CH3), 2.17 (s, 3H, o-CH3), 2.33 (s, 3H, CH3), 6.30-7.80
(m broad, 18 Ar-H), 7.95 (s, 1H, Pyr-H); major isomer 2.21 (s,
3H, o-CH3), 2.23 (s, 3H, o-CH3), 2.33 (s, 3H, CH3), 6.30-7.80
(broad, 18 Ar-H), 6.62 (s, 1H, Pyr-H). 13C NMR (63 MHz,
CDCl3, rt): δ (ppm) 18.12, 18.26, 24.26, 24.46, 162.54, 163.04,
163.47, 163.70, 163.90, 167.33, 167.64. IR (KBr): 1626 (ν(Cd
N)), 1576 cm-1. MS (EI) m/z: 480 (67%, M+), 194 (62%), 106
(57%), 91 (100%). Anal. Calcd for C33H28N4: C, 82.47; H, 5.87;
N, 11.66. Found: C, 82.40; H, 5.87; N, 11.64.
2,4,6-Tris[(2,6-diisopropylphenylimino)methyl]-1,3,5-triaz-
ine (2b). To a solution of 2,6-diisopropylaniline hydrochloride (2.83
g, 13.2 mmol) in water/ethanol 32 mL/16 mL heated at 60 °C was
added in small portions 2,4,6-tris(dimorpholinomethyl)-1,3,5-tri-
azine (1.20 g, 1.88 mmol). The mixture was stirred rapidly for 20
min at this temperature and then cooled to room temperature.
Ethanol was removed by rotary evaporation, and the pH of the
aqueous phase was adjusted to 13. The aqueous phase was extracted
three times with dichloromethane. The combined organic layers
were washed with brine, dried over MgSO4, and evaporated. The
crude mixture was purified by column chromatography on deac-
tivated alumina (ethyl acetate/petroleum ether, 5/95) and dried under
high vacuum to yield an orange powder. Yield: 0.54 g (45%). Mp
212-213 °C. 1H NMR (250 MHz, CDCl3, rt): δ (ppm) 1.18 (d, J
) 6.8 Hz, 36H, CH(CH3)2), 2.99 (septet, J ) 6.8 Hz, 6H,
CH(CH3)2), 7.19 (m, 9H, ArsH), 8.62 (s, 3H, CHN). 13C NMR
(63 MHz, CDCl3, rt): δ (ppm) 23.66 (CH3), 28.01 (CH(CH3)2),
123.2, 125.6, 136.7, 147.7, 160.1 (CdN), 170.1 (NCN). EI mass
spectrum (m/z): 642 [(M)+, 100], 187 [(ArNdC)+, 59]. Anal. Calcd
for C42H54N6: C, 78.46; H, 8.47; N, 13.07. Found: C, 78.53; H,
2,6-Bis[(2,4,6-trimethylphenylimino)benzyl]-pyridine (9). The
same procedure as for 1a, using 2,4,6-trimethylaniline and 2,6-
dibenzoylpyridine gave a yellow powder. A sample was purified
by flash chromatography on silica gel (ethyl acetate/hexane 1:9,
Rf ) 0.45) to afford analytically pure material. Yield: 2.3 g (88%).
1
Mp 188-190 °C. H NMR (250 MHz, CDCl3, rt): δ (ppm) 1.98
(s, 12H, CH3), 2.21 (s, 6H, CH3), 6.5-7.5 (ArH and pyrH). 13C
NMR (63 MHz, CDCl3, rt): δ (ppm) 18.47, 20.65, 145.64, 146.13,
154.18, 155.19, 155.78, 157.12, 165.21, 165.89, 166.10, 166.58.
IR (KBr): 1627 (ν(CdN)) cm-1. Anal. Calcd for C37H35N3: C,
85.18; H, 6.76; N, 8.05. Found: C, 85.26; H, 6.83; N, 7.98.
2,6-Dibenzoyl-4-benzyl-1,3,5-triazine. To a solution of 2,4-Bis-
(1-phenyl-2-morpholinoethen-1-yl)-6-benzyl-1,3,5-triazine (2.73 g,
5 mmol) in CCl4/CH3CN (20 mL/20 mL) was first added an
aqueous solution of sodium periodate (8.94 g, 42 mmol in 30 mL
of water) and then 250 mg of RuCl3‚(H2O)x in one portion. The
black mixture was vigorously stirred for 1 h at room temperature,
diluted with water, transferred to a separating funnel, and extracted
twice with dichloromethane. The combined organic phases were
dried over magnesium sulfate and filtered, and the solvent was
evaporated in vacuo. The crude product was purified by flash
chromatography on silica gel using ethyl acetate/petroleum ether
2/8 as eluent to give a yellow crystalline material. Yield: 0.64 g
(34%). Mp 118 °C. 1H NMR (250 MHz, CDCl3, rt): δ (ppm) 4.43
(s, 2H, CH2), 7.28-7.37 (m, 3H, Ar-H), 7.42-7.51 (m, 6H, Ar-
H), 7.61-7.68 (m, 2H, Ar-H), 7.97-8.00 (m, 4H, Ar-H). 13C
NMR (63 MHz, CDCl3, rt): δ (ppm) 45.54 (CH2), 127.34, 128.62,
128.75, 129.44, 130.80, 133.51, 134.54, 135.49, 170.51 (NCN),
8.38; N, 12.98. IR (KBr): 1646, 1528 cm-1
.
2,5-Bis[(2,6-diisopropylphenylimino)methyl]furan (3). A mix-
ture of furan-2,5-dialdehyde (0.28 g, 2.26 mmol) and 2,6-diiso-
propylaniline (0.8 g, 2 equiv) were dissolved in 20 mL of
dichloromethane. After the addition of a drop of formic acid and
two spatulas of MgSO4, the mixture was stirred at room temperature
overnight. After filtration, the solvent was evaporated, and the crude
product was recrystallized from hot petroleum ether. Yield: 0.78
1
g (78%). H NMR (250 MHz, CDCl3, rt): δ (ppm) 1.19 (d, 24H,
CH3), 3.01 (sept, 4H,CH(CH3)2), 7.18 (m, 6H, ArsH), 7.22 (s, 2H,
CHsCH), 8.14 (s, 2H, NdCH). 13C NMR (63 MHz, CDCl3, rt):
δ (ppm) 23.63 (CH3), 27.90 (CH(CH3)2), 115.54 (CdCH) 123.11,
124.66, 137.63, 148.48 (ArC), 150.77 (CdN), 153.81 (ArC). IR
(KBr): 1635 (ν(CdN)) cm-1. MS (EI) m/z: 442 (M+, 100%), 427
([M - CH3]+, 20%), 254 ([MsArNdCH]+, 43%)], 188 [(ArNd
CH)+, 45]. Anal. Calcd for C30H38N2O: C, 81.40; H, 8.65; N, 6.33.
Found: C, 81.34; H, 8.73; N, 6.26%.
180.10 (NCCO), 188.99 (CO). IR (KBr): 1679 (ν(CdO)) cm-1
.
MS (CI) m/z: 397 (MNH4+, 100%), 380 (MH+, 53%). Anal. Calcd
3462 Inorganic Chemistry, Vol. 42, No. 11, 2003

Fe and Co Ethylene Polymerization Catalysts
2,5-Bis[(2,6-diisopropylphenylimino)methyl]thiophene (4). A
mixture of thiophene dialdehyde (0.25 g; 1.78 mmol) and 2,6-
diisopropylaniline was dissolved in 20 mL of dichloromethane.
After the addition of a drop of formic acid and two spatulas of
MgSO4, the mixture was stirred at room temperature overnight.
After filtration, the solvent was evaporated, and the crude product
was recrystallized from hot petroleum ether. Yield: 0.63 g (77%).
1H NMR (250 MHz, CDCl3, rt): δ (ppm) 1.22 (d, 24H, CH3), 3.03
(sept, 4H,CH(CH3)2), 7.17 (m, 6H, ArsH), 7.50 (s, 2H, CHsCH),
8.32 (s, 2H, NdCH). 13C NMR (63 MHz, CDCl3, rt): δ (ppm)
23.51 (CH3), 28.05 (CH(CH3)2), 123.04, 124.51, 131.42, 137.71,
1,8-Diformyl-3,6-dimethyl-9H-carbazole. n-BuLi [3.0 mL (7.5
mmol), 2.5 M in hexane] was added to a solution of 2.48 g (7.0
mmol) of 1,8-dibromo-3,6-dimethyl-9H-carbazole in 100 mL of
diethyl ether at 0 °C. After stirring for 1 h, 0.98 mL (7.7 mmol) of
trimethylsilyl chloride was added, and the reaction mixture was
allowed to warm to ambient temperature. The suspension briefly
became a clear solution followed by the formation of a white
precipitate. After stirring for 1 h at rt, the suspension was cooled
to -78 °C, and 20 mL (30 mmol) of t-BuLi (1.5 M in pentane)
was added. After completed addition, the reaction mixture was
stirred at 0 °C for 3 h. At -78 °C, 3.8 mL (38.7 mmol) of anhydrous
dimethylformamide was added, and the reaction mixture was
allowed to warm to room temperature overnight. Hydrolysis was
performed at 0 °C by the addition of 50 mL of 1 M aqueous HCl.
The organic phase was washed with 2 × 50 mL of 1 M aqueous
NaOH and 2 × 50 mL of 3 M aqueous NaCl solutions, dried over
MgSO4, and filtered, and the solvent was removed on a rotary
evaporator to afford the product as a yellow solid. Yield: 1.73 g
145.94, 148.42, 154.83 (ArC). IR (KBr): 1623 (ν(CdN)) cm-1
.
MS (EI) m/z: 458 (M+, 100%), 443 ([M - CH3]+, 20%). Anal.
Calcd for C30H38N2S: C, 78.55; H, 8.35; N, 6.11. Found: C, 78.48;
H, 8.31; N, 6.04%.
3,6-Dimethyl-9H-carbazole. 3,6-Dibromo-9H-carbazole (5.3 g,
16.3 mmol) was dissolved in 200 mL of diethyl ether, and 7.0 mL
(17.5 mmol) of n-BuLi (2.5 M in hexane) was added dropwise at
0 °C. After stirring for 1 h at this temperature, 2.2 mL (17.3 mmol)
of trimethylsilyl chloride was added, and the reaction mixture was
allowed to warm to room temperature. The suspension briefly
became a clear solution followed by the formation of a white
precipitate. After stirring at rt for 1 h, the suspension was cooled
to -78 °C, and 45 mL (67.5 mmol) of t-BuLi (1.5 M in pentane)
was added. The thick, white suspension was then stirred at 0 °C
for 3 h after which it was cooled to -78 °C. At this temperature,
5.0 mL (82 mmol) of methyliodide was added, and the reaction
mixture was allowed to warm to rt overnight. The reaction mixture
was hydrolyzed by the addition of 50 mL of 1 M aqueous HCl.
The layers were separated, and the organic phase was washed with
2 × 50 mL of 1 M aqueous HCl solution and 50 mL of H2O, dried
over MgSO4, and filtered, and all volatiles were removed on a rotary
evaporator. The crude product was recrystallized from hot hexane/
ethanol to afford an off-white, amorphous solid. Yield: 3.0 g (94%).
1
(98%). Mp. 241-242 °C. Rf (SiO2, hexane/EtOAc 5:1) 0.13. H
NMR (250 MHz, CDCl3, rt): δ (ppm) 2.60 (s, 6H, CH3), 7.68 (s,
2H, ArsH), 8.11 (s, 2H, ArsH), 10.17 (s, 2H, OdCH), 11.44 (br,
1H, NH). 13C NMR (63 MHz, CDCl3, rt): δ (ppm) 21.2 (CH3),
120.1 (ArsC), 123.4 (ArsC), 127.1 (ArsC), 129.3 (ArsC), 132.8
(ArsC), 136.9 (ArsC), 192.7 (OdCH). IR (thin film): 3449 (m,
ν(NsH)), 3013 (w), 2956 (w), 2916 (w), 2838 (w), 2800 (w), 2737
(w), 1675 (s, ν(CdO)), 1622 (m), 1593 (s) 1487 (m), 1316 (m),
1218 (m), 1156 (w), 1114 (m), 1071 (m), 997 (w), 967 (m), 860
(m), 825 (w), 779 (w), 719 (m), 685 (w), 617 (m) cm-1. MS (EI)
m/z: 251 (M+), 222 ([M - CHdO]+). Anal. Calcd for C16H13-
NO2: C, 76.48; H, 5.21; N, 5.57. Found: C, 76.51; H, 5.12; N,
5.40%.
1,8-Bis[(2,4,6-trimethylphenylimino)methyl]-3,6-dimethyl-9H-
carbazole (5). 1,8-Diformyl-3,6-dimethyl-9H-carbazole [470 mg
(1.87 mmol)] and 530 µL (3.77 mmol) of 2,4,6-trimethylaniline
were dissolved in 100 mL of chloroform. After addition of 5 drops
of glacial acetic acid and 4 Å molecular sieves, the reaction mixture
was refluxed for 3 days and then filtered hot. All volatiles were
removed on a rotary evaporator to afford a yellow solid. The crude
product was purified by crystallization from hot ethanol/hexane.
1
Mp 218-219 °C. Rf (SiO2, hexane/EtOAc 10:1) 0.19. H NMR
(250 MHz, C6D6, rt): δ (ppm) 2.44 (s, 6H, CH3), 6.46 (br, 1H,
3
3
NH), 7.00 (d, 2H, J(HH) ) 8.2 Hz, Ar-H), 7.21 (d, 2H, J(HH)
) 8.2 Hz, Ar-H), 7.81 (s, 2H, Ar-H). 13C NMR (63 MHz, CDCl3,
rt): δ 21.4 (CH3), 110.2 (Ar-C), 120.2 (Ar-C), 123.38 (Ar-C),
127.0 (Ar-C), 128.5 (Ar-C), 138.0 (Ar-C). MS (EI) m/z: 195
(M+, 100%). The spectroscopic data are consistent with previously
published values for 3,6-dimethyl-9H-carbazole, obtained via
different synthetic routes.36,37
1
Yield: 640 mg (70%). Mp 226-227 °C. H NMR (250 MHz,
CDCl3, rt): δ (ppm) 2.09 (s, 12H, o-CH3), 2.25 (s, 6H, p-CH3),
2.58 (s, 6H, CH3), 6.82 (s, 4H, PhsHm), 7.39 (s, 2H, ArsH), 8.03
(s, 2H, ArsH), 8.41 (s, 2H, NdCH), 12.27 (br, 1H, NH). 13C NMR
(63 MHz, CDCl3, rt): δ (ppm) 18.3 (o-CH3), 20.7 (p-CH3), 21.3
(CH3), 119.2 (ArsC), 123.4 (ArsC), 123.4 (ArsC), 127.6 (Ars
C), 128.2 (ArsC), 128.7 (ArsC), 130.8 (ArsC), 132.8 (ArsC),
136.5 (ArsC), 149.1 (ArsC), 163.5 (NdCH). IR (thin film): 3385
(m, ν(N-H)), 3006 (w), 2970 (w), 2946 (m), 2916 (m), 2860 (w),
1638 (m), 1612 (s), 1589 (s), 1480 (s), 1444 (m), 1380 (w), 1316
(s), 1221 (s), 1203 (s), 1108 (w), 1080 (w), 978 (m), 855 (s), 739
(w), 674 (w), 661 (w) cm-1. EI mass spectrum m/z: 485 (M+),
470 ([M - CH3]+). Anal. Calcd for C34H35N3: C, 84.08; H, 7.26;
N, 8.65. Found: C, 84.16; H, 7.17; N, 8.77%.
1,8-Dibromo-3,6-dimethyl-9H-carbazole. 3,6-Dimethyl-9H-car-
bazole (4.78 g, 24.5 mmol) was dissolved in 400 mL of dichloro-
methane. After addition of 50g of silica gel, the reaction flask was
immersed in an ice bath. N-Bromosuccinimide, 8.68 g (49.0 mmol),
dissolved in 400 mL of dichloromethane, was added over a period
of 2 h at 0 °C under the exclusion of light. After the addition was
completed, the reaction mixture was stirred at rt for another 30
min. The solution was filtered, and the filtrate was washed with
3 × 50 mL of 1 M aqueous NaOH and 1 × 50 mL of 3 M aqueous
NaCl solutions, dried over MgSO4, and filtered. The solvent was
removed on a rotary evaporator to afford an off-white solid.
Yield: 8.25 g (95%). Mp 142-143 °C. Rf (SiO2, hexane/EtOAc
10:1) 0.53. 1H NMR (250 MHz, CDCl3, rt): δ (ppm) 2.48 (s, 6H,
CH3), 7.41 (s, 2H, Ar-H), 7.71 (s, 2H, Ar-H), 8.10 (br, 1H, NH).
13C NMR (63 MHz, CDCl3, rt): δ (ppm) 21.2 (CH3), 103.9 (Ar-
C), 119.7 (Ar-C), 124.7 (Ar-C), 129.7 (Ar-C), 130.8 (Ar-C),
136.9 (Ar-C). MS (EI) m/z: 353 (M+), 272 ([M - Br]+). Anal.
Calcd for C14H11Br2N: C, 47.63; H, 3.14; N, 3.97. Found: C, 47.83;
H, 3.23; N, 3.67%.
4,6-Bis[(2,4,6-trimethylphenylimino)methyl]dibenzofuran (6a).
4,6-Dibenzofuran-dicarbaldehyde (448 mg, 2 mmol) and 2,4,6-
trimethylaniline (0.57 mL, 4 mmol) were dissolved in 10 mL of
ethanol, to which was added 1 drop of glacial acetic acid and 4 Å
molecular sieves. The mixture was refluxed overnight. The yellow
precipitate was filtered, washed with cold ethanol, and dried in
1
vacuo. Yield: 0.83 g (90%). H NMR (250 MHz, CDCl3, rt): δ
(ppm) 8.87 (s, 2H, CHdN), 8.32 (d, 2H, J ) 7.7 Hz, ArH), 8.12
(d, 2H, J ) 7.7 Hz, ArH), 7.52 (t, 2H, J ) 7.7 Hz, ArH), 6.90 (s,
4H, ArHm), 2.29 (s, 6H, ArMep), 2.16 (s, 12H, ArMeo). 13C NMR
Inorganic Chemistry, Vol. 42, No. 11, 2003 3463

Britovsek et al.
(63 MHz, CDCl3, rt): δ (ppm) 156.92 (CHdN), 155.74, 148.93,
133.21, 128.77, 126.99, 124.94, 124.59, 123.53, 123.42, 120.94
(ArC), 20.73 (p-CH3), 18.27 (o-CH3). MS (EI) m/z: 459 ([M]+,
40%).
(Ar-H), 14.2, 15.6, 75.8 (Pyr-H). IR (KBr): 1616 (ν(CdN)), 1578
cm-1. FAB mass spectrum (m/z): 634 (M+, 45%), 599 ([M - Cl]+,
100%). Anal. Calcd for C35H32N4FeCl2: C, 66.16; H, 5.43; N, 8.81.
Found: C, 65.85; H, 5.26; N, 8.73. µeff (Evans NMR method) )
4.9 µB.
4,6-Bis[(2,6-diisopropylphenylimino)methyl]dibenzofuran (6b).
4,6-Dibenzofuran-dicarbaldehyde (448 mg, 2 mmol) and 2,6-
diisopropylaniline (0.75 mL, 4 mmol) were dissolved in a mixture
of 5 mL of ethanol and 5 mL of 2-propanol, to which was added
1 drop of glacial acetic acid and 4 Å molecular sieves. The mixture
was refluxed overnight. The yellow precipitate was filtered, washed
2,4-Bis[(2,4,6-trimethylphenylimino)benzyl]-6-methylpyrimi-
dine Iron(II) Dichloride, [(1b)FeCl2]. The described procedure
using 1b and FeCl2 gave [(1b)FeCl2] as a green powder in 69%
1
yield. H NMR (250 MHz, CD2Cl2, rt, all peaks appear as broad
singlets): δ (ppm) -28.1 (CH3 pyr), 6.5, 7.4, 7.9, 8.1, 10.1 (Ar-
H), 11.5 (Ar-H), 13.9, 15.2, 20.3, 21.2, 75.5 (Pyr-H). IR (KBr):
1635, 1624, 1616 (ν(CdN)), 1578 cm-1. FAB mass spectrum (m/
z): 662 [(M)+, 46], 627 [(M - Cl)+, 100]. Anal. Calcd for
C37H36N4FeCl2: C, 66.98; H, 5.47; N, 8.44. Found: C, 66.63; H,
5.27; N, 8.32. µeff (Evans NMR method) ) 4.4 µB.
1
with cold ethanol, and dried in vacuo. Yield: 0.94 g (87%). H
NMR (250 MHz, CDCl3, rt): δ (ppm) 8.82 (s, 2H, CHdN), 8.32
(d, 2H, J ) 7.7 Hz, ArH), 8.15 (d, 2H, J ) 7.7 Hz, ArH), 7.54 (t,
2H, J ) 7.7 Hz, ArH), 7.26-7.06 (m, 6H, ArH), 2.99 (sept, 4H, J
) 6.8 Hz, CHMe2), 1.15 (d, 24H, J ) 6.8 Hz, CH3). 13C NMR (63
MHz, CDCl3, rt): δ (ppm) 156.10 (CHdN), 149.50, 137.47, 125.02,
124.31, 123.62, 123.49, 123.00, 120.82 (ArC), 27.94 (CH(CH3)2),
23.46 (CH(CH3)2). MS (EI) m/z: 543 ([M]+, 50%).
Bis[o-((2,6-diisopropylphenylimino)methyl)phenyl]ether (7).
Standard condensation of bis(o-formylphenyl)ether with 2 equiv
of 2,6-diisopropylaniline in ethanol afforded the product in 95%
yield. 1H NMR (250 MHz, CDCl3, rt): δ (ppm) 8.60 (s, 2H, CHd
N), 8.31 (dd, 2H, J ) 1.6, 7.7 Hz, ArH), 7.46 (m, 2H, ArH), 7.29
(m, 2H, ArH), 7.14-7.07 (m, 6H, ArH), 6.87 (d, 2H, J ) 7.4 Hz,
ArH), 2.88 (sept, 4H, J ) 6.8 Hz, CHMe2), 1.06 (d, 24H, J ) 6.8
Hz, CH3). 13C NMR (63 MHz, CDCl3, rt): δ (ppm) 157.29 (CHd
N), 157.08, 149.44, 137.52, 132.79, 127.97, 127.19, 124.35, 124.15,
122.95, 118.71 (ArC), 27.89 (CH(CH3)2), 23.36 (CH3). MS (EI)
m/z: 544 (M+, 65%), 368 ([M - ArN]+, 100%). Anal. Calcd for
C38H44N2O: C, 83.78; H, 8.14; N, 5.14. Found: C, 83.79; H, 8.05;
N, 5.12%.
2,4-Bis[(2,6-diisopropylphenylimino)benzyl]-6-methylpyrimi-
dine Iron(II) Dichloride, [(1c)FeCl2]. The described procedure
using 1c and FeCl2 gave [(1c)FeCl2] as a green powder in 59%
1
yield. Mp 176 °C dec. H NMR (250 MHz, CD2Cl2, rt, all peaks
appear as broad singlets): δ (ppm) -42.5 (CH3 pyr), -10.4 (Ar-
H), -9.8 (Ar-H), -9.4, -8.9, -8.6, 0.0, 0.2, 1.1, 2.1, 2.2, 2.6,
3.5, 4.7, 6.0, 6.7, 7.2, 7.6, 8.3, 9.3, 9.5, 9.8, 9.9, 12.5, 12.9, 15.1,
82.9 (Pyr-H). IR (KBr): 1635, 1623, 1617 (ν(CdN)), 1577 cm-1
.
MS (FAB) m/z: 746 (M+, 25%), 711 ([M - Cl]+, 40%), 621 ([M
- FeCl2]+, 100). Anal. Calcd for C43H48N4FeCl2: C, 69.08; H,
6.47; N, 7.49. Found: C, 69.15; H, 5.77; N, 7.25. µeff (Evans NMR
method) ) 4.4 µB.
2,4-Bis[(2-methylphenylimino)benzyl]-6-methylpyrimidine Iron-
(II) Dichloride, [(1d)FeCl2]. The described procedure using 1d
and FeCl2 gave [(1d)FeCl2] as a green powder in 71% yield. Mp
133 °C dec. The solubility of complex [(1d)FeCl2] in dichloro-
methane was insufficient for NMR analysis. IR (KBr): 1581 (ν-
(CdN)) cm-1. MS (FAB) m/z: 606 (M+, 24%), 571 ([M - Cl]+,
84%). Anal. Calcd for C33H28N4FeCl2: C, 65.26; H, 4.65; N, 9.22.
Found: C, 65.15; H, 4.55; N, 9.09. µeff (Evans balance) ) 4.8 µB.
2,4-Bis[(2,4,6-dimethylphenylimino)benzyl]-6-methylpyrimi-
dine Cobalt(II) Dichloride, [(1b)CoCl2]. The described procedure
using 1b and CoCl2 gave [(1b)CoCl2] as a brown powder in 73%
Bis(o-formylphenyl)thioether. Bis(o-formylphenyl)thioether was
prepared according to the same procedure as described for bis(o-
1
formylphenyl)ether.45 Yield: 91%. H NMR (250 MHz, CDCl3,
rt): δ (ppm) 10.36 (s, 2H, CHdO), 7.96 (m, 2H, ArH), 7.47 (m,
4H, ArH), 7.17 (m, 2H, ArH). 13C NMR (63 MHz, CDCl3, rt): δ
(ppm) 191.52 (CHdO), 138.60, 135.03, 134.68, 132.58, 131.81,
127.89 (ArC). MS (EI) m/z: 242 (M+, 30%), 213 ([M - CHO]+,
100%). Anal. Calcd for C14H10O2S: C, 69.40; H, 4.16. Found: C,
69.33; H, 4.28%.
Bis[o-((2,6-diisopropylphenylimino)methyl)phenyl]thio-
ether (8). Condensation of bis(o-formylphenyl)thioether with 2
equiv of 2,6-diisiopropylaniline in ethanol afforded the product in
95% yield. 1H NMR (250 MHz, CDCl3, rt): δ (ppm) 8.71 (s, 2H,
CHdN), 8.23 (m, 2H, ArH), 7.43 (m, 4H, ArH), 7.22 (m, 2H, ArH),
7.15-7.10 (m, 6H, ArH), 2.92 (sept, 4H, J ) 6.8 Hz, CHMe2),
1.11 (d, 24H, J ) 6.8 Hz, CH3). 13C NMR (63 MHz, CDCl3, rt):
δ (ppm) 160.33 (CHdN), 149.01, 137.55, 136.70, 135.93, 132.36,
131.84, 129.05, 127.89, 124.25, 122.99 (ArC), 27.94 (CH(CH3)2),
23.47 (CH3). MS (EI) m/z: 560 (M+, 100%), 384 ([M - ArN+,
25%). Anal. Calcd for C38H44N2S: C, 81.38; H, 7.91; N, 4.99.
Found: C, 81.28; H, 7.86; N, 4.89%.
2,4-Bis[(2,6-dimethylphenylimino)benzyl]-6-methylpyrimi-
dine Iron(II) Dichloride, [(1a)FeCl2]. A suspension of 1a (80 mg,
0.15 mmol) in n-butanol was added dropwise at 80 °C to a solution
of FeCl2 (20 mg, 0.15 mmol) in n-butanol (10 mL) to yield a dark
green solution. After being stirred at 80 °C for 30 min, the reaction
volume was concentrated, and diethyl ether (10 mL) was added to
precipitate the product as a green powder, which was subsequently
washed with diethyl ether (2 × 10 mL), filtered, and dried to afford
65 mg (62%) of [(1a)FeCl2]. Mp 238 °C dec. 1H NMR (250 MHz,
CD2Cl2, rt, all peaks appear as broad singlets): δ (ppm) -26.2
(CH3 pyr), -10.8, -9.4, 6.5, 7.2, 7.8, 8.0, 8.2, 9.9 (Ar-H), 10.8
1
yield. Mp > 300 °C. H NMR (250 MHz, CD2Cl2, rt, all peaks
appear as broad singlets): δ (ppm) -28.0 (Ar-H), -25.9 (Ar-
H), -1.5, -1.0, 2.1, 2.7, 3.5, 4.7, 12.8, 14.1, 27.0 (CH3 pyr), 98.4
(Pyr-H). IR (KBr): 1583 (ν(CdN)) cm-1. MS (FAB) m/z: 630
([M - Cl]+, 100%). Anal. Calcd for C37H36N4CoCl2: C, 66.68; H,
5.44; N, 8.41. Found: C, 66.44; H, 5.60; N, 8.56. µeff (Evans NMR
method) ) 4.5 µB.
2,4-Bis[(2-methylphenylimino)benzyl]-6-methylpyrimidine Co-
balt(II) Dichloride, [(1d)CoCl2]. The described procedure using
1d and CoCl2 gave [(1d)CoCl2] as a brown powder in 80% yield.
Mp 175 °C dec. 1H NMR (250 MHz, CD2Cl2, rt, all peaks appear
as broad singlets): δ (ppm) -21.8, -21.1, -17.7, -17.4, -14.4,
-12.1, -10.7, -10.2, -8.2, -5.1, -4.1, -2.9, -2.5, -1.6, -0.7,
0.0, 0.4, 0.7, 0.9, 1.1, 1.6, 2.5, 2.9, 42.2 (3H, CH3), 85.3 (1H, Pyr-
H). IR (KBr): 1609 (ν(CdN)), 1578 cm-1. MS (FAB) m/z: 574
([M - Cl]+, 100%). Anal. Calcd for C33H28N4CoCl2: C, 64.93; H,
4.62; N, 9.18. Found: C, 64.79; H, 4.59; N, 8.98. µeff (Evans NMR
method) ) 4.1 µB.
2,6-Bis[(2,4,6-trimethylphenylimino)benzyl]-pyridine Iron(II)
Dichloride, [(9)FeCl2]. The described procedure using 2,6-bis-
[(2,4,6-trimethylphenylimino)phenyl]pyridine and FeCl2 gave
[(9)FeCl2] as a green powder in 71% yield. Mp > 300 °C. 1H NMR
(250 MHz, CD2Cl2, rt, all peaks appear as broad singlets): δ (ppm)
1.6, 7.4, 7.7 (4H, Ar-H), 11.9 (10H, Ar-H), 14.8, 22.8 (12H,
o-CH3), 63.0 (1H, Pyr-Hp), 78.1 (2H, Pyr-Hm). IR (KBr): 1653,
3464 Inorganic Chemistry, Vol. 42, No. 11, 2003

Fe and Co Ethylene Polymerization Catalysts
1635, 1576 (ν(CdN)) cm-1. MS (FAB) m/z: 648 ([M]+, 50%),
613 ([M - Cl]+, 100%). Anal. Calcd for C37H35N3FeCl2: C, 68.53;
H, 5.44; N, 6.48. Found: C, 68.63; H, 5.54; N, 6.59. µeff (Evans
NMR method) ) 4.7 µB.
Table 2. Crystallographic Data for Compounds 1c and [(5)CoCl]a
1c
[(5)CoCl]
chemical formula
solvent
fw
space group
a (Å)
b (Å)
c (Å)
C43H48N4
C34H34N3ClCo
C7H8
2,6-Bis[(2,4,6-trimethylphenylimino)benzyl]-pyridine Cobalt-
(II) Dichloride, [(9)CoCl2]. The described procedure using 2,6-
bis[(2,4,6-trimethylphenylimino)phenyl]pyridine and CoCl2 gave
620.9
671.2
I2/a (No. 15)
21.109(2)
8.849(2)
41.185(6)
102.09(2)
7522(2)
8
Pbca (No. 61)
11.629(2)
15.875(2)
37.944(4)
1
[(9)CoCl2] as a brown powder in 80% yield. Mp > 300 °C. H
â (deg)
V (Å3)
Z
NMR (250 MHz, CD2Cl2, rt, all peaks appear as broad singlets):
δ (ppm) -26.1 (10H, Ar-H), -0.7 (4H, Ar-H), 3.5, 6.0 (6H,
CH3), 16.5 (12H, CH3), 37.8 (1H, Pyr-Hp), 103.1 (2H, Pyr-Hm).
IR (KBr): 1609 (ν(CdN)), 1578 cm-1. MS (FAB) m/z: 615 ([M
- Cl]+, 100%), 580 ([M - 2Cl]+, 20%). Anal. Calcd for C37H35N3-
CoCl2: C, 68.21; H, 5.41; N, 6.45. Found: C, 66.96; H, 5.62; N,
6.24. µeff (Evans NMR method) ) 4.3 µB.
7005(1)
8
1.273
0.60
0.066
0.148
F
calcd (g cm-3
)
1.096
µ (mm-1
R1b
)
0.06
0.054
wR2c
0.129
a Details in common: Bruker P4 diffractometer, graphite monochromated
Mo KR radiation (λ ) 0.71073 Å), T ) 20 °C, refinement based on F2.
1,8-Bis[(2,4,6-trimethylphenylimino)methyl]-3,6-dimethylcar-
bazolide Iron(II) Chloride, [(5)FeCl]. Sodium hydride (465 mg,
19.3 mmol) and 940 mg (1.94 mmol) of 1,8-bis(2,4,6-trimethyl-
phenylimino)-3,6-dimethyl-9H-carbazole (5) were placed in a
Schlenk flask, and 60 mL of THF was added. The reaction mixture
was stirred at 65 °C for 16 h. After cooling to ambient temperature,
the deep orange solution was removed by filtration, added to a
suspension of 456 mg (1.94 mmol) of FeCl2(THF)1.5 in 40 mL THF,
and stirred at rt for 16 h. The solvent was then removed in vacuo,
and the residue was extracted with dichloromethane. This solution
was concentrated to 5 mL, and the product was precipitated by the
addition of pentane (50 mL). After washing with diethyl ether (3
× 30 mL) and drying in vacuo, the product was obtained as an
orange-red, microcrystalline solid. Yield: 934 mg (84%). 1H NMR
(250 MHz, CD2Cl2, rt, all peaks appear as broad singlets): δ (ppm)
-33.6 (12H, o-CH3), 8.6 (4H, Ph-Hm), 11.9 (2H, Ar-H), 18.8
(6H, CH3 or p-CH3), 33.3 (6H, CH3 or p-CH3), 59.3 (2H, Ar-H).
IR (KBr): 3010 (w), 2948 (w), 2918 (w), 2860 (w), 1631 (w, ν-
(CdN)), 1610 (w), 1576 (s), 1470 (m), 1373 (m), 1343 (w), 1306
(w), 1281 (w), 1242 (w), 1206 (s), 1196 (s), 1138 (m), 991 (w),
853 (m), 764 (w), 735 (w), 674 (w), 659 (w) cm-1. MS (FAB)
m/z: 575 (M+), 540 ([M - Cl]+). Anal. Calcd for C34H34-
ClFeN3‚1.4CH2Cl2: C, 61.19; H, 5.34; N, 6.05. Found: C, 61.46;
H, 5.18; N, 5.67%. µeff (Evans NMR method) ) 5.2 µB.
2
2
2
b R1 ) ∑||Fo| - |Fc||/∑|Fo|. c wR2 ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2
;
w-1 ) σ2(Fo ) + (aP)2 + bP.
2
X-Ray Crystallography. Table 2 provides a summary of the
crystallographic data for compounds 1c and [(5)CoCl]. CCDC
207084 and 207085.
General Polymerization Procedures. (a) High-Pressure Reac-
tor Tests. A 1 L stainless steel reactor was baked out under a
nitrogen flow for at least 1 h at >85 °C and subsequently cooled
to the temperature of polymerization. Isobutane (0.5 L) and MAO
(10 wt% in toluene) were introduced into the reactor and stirred at
reaction temperature for at least 1 h. Ethylene was introduced by
overpressure, and the difference between the total pressure and the
initial pressure (isobutane and nitrogen: ca. 10 bar) is the pressure
quoted in Table 1. The catalyst solution in toluene was then injected
under nitrogen. The reactor pressure was maintained constantly
throughout the polymerization run by computer controlled addition
of ethylene. The polymerization time was 60 min. Runs were
terminated by venting off all volatiles, and the reactor contents were
isolated, washed with aqueous HCl and methanol, and dried in a
vacuum oven at 50 °C.
(b) Schlenk-Flask Ethylene Polymerization Tests. The pre-
catalyst was dissolved in toluene (100 mL), and MAO (10 wt % in
toluene) was added via syringe. The Schlenk flask was placed in a
water bath and purged with ethylene, and the contents magnetically
stirred and maintained under ethylene (1 bar) for the duration of
the polymerization (60 min). The polymerization was terminated
by the addition of aqueous hydrogen chloride. The solid PE was
recovered by filtration, washed with methanol (50 mL), and dried
(vacuum oven at 50 °C).
1,8-Bis[(2,4,6-trimethylphenylimino)methyl]-3,6-dimethylcar-
bazolide Cobalt(II) Chloride [(5)CoCl]. The described procedure
using 5, NaH, and CoCl2 gave [(5)CoCl2] as a deep red powder in
81% yield. Crystals suitable for X-ray analysis were grown by slow
cooling of a hot, concentrated solution in toluene to ambient
1
temperature. H NMR (250 MHz, CD2Cl2, rt, all peaks appear as
Acknowledgment. The authors are grateful to BP Chemi-
cals Ltd. for financial support and to Crompton Corp. for
the donation of MAO. Dr. J. Boyle and Dr. G. Audley are
thanked for GPC and NMR measurements.
broad singlets): δ (ppm) -15.6 (12H, o-CH3), 11.0 (4H, Ph-Hm),
18.6 (6H, p-CH3), 22.2 (2H, Ar-H), 42.5 (6H, CH3), 48.9 (2H,
Ar-H). IR (KBr): 3005 (w), 2948 (w), 2915 (w), 2857 (w), 1627
(w, ν(CdN)), 1603 (m), 1573 (m), 1544 (s), 1477 (m), 1446 (m),
1364 (m), 1313 (m), 1242 (m), 1208 (s), 1197 (s), 1141 (s), 984
(m), 857 (m), 768 (w), 731 (m), 674 (w) cm-1. MS (FAB) m/z:
578 (M+), 543 ([M - Cl]+). Anal. Calcd for C34H34ClCoN3‚C7H8:
C, 73.37; H, 6.31; N, 6.26. Found: C, 73.35; H, 6.40; N, 6.22%.
µeff (Evans NMR method) ) 4.4 µB.
Supporting Information Available: Additional figures and
X-ray Crystallographic data in CIF format. This material is available
free of charge via the Internet at http://pubs.acs.org.
IC034040Q
Inorganic Chemistry, Vol. 42, No. 11, 2003 3465