High-temperature catalysts for the production of a-olefins based on iron(II) and cobalt(II) tridentate bis(imino)pyridine complexes with a double pattern of substitution: O-methyl plus o-fluorine in the same imino arm

Article abstract of DOI:10.1021/om701204w

The new series of bis(imino)pyridine ligands [2-F-6-MePhN=C(Me)PyC(Me)=NPh- 2-F-6-Me] (14), [2-F-6-MePhN=C(Me)PyC(Me)=NPh-2-Me] (19), and [2-F-6-MePhN=C(Me)PyC(Me)=N-Ph-2,4-Me₂] (20) and their corresponding Fe(II) complexes [{2-F-6-Me-PhN=C(Me)PyC(Me)=NPh-2-F-6-Me}FeCl₂] (4), [{2-F-6-MePhN=C(Me)PyC(Me)=NPh-2-Me}FeCl₂] (5), and {[2-F-6-MePhN=C(Me)PyC(Me)=NPh-2,4-Me₂]FeCl₂} (6) and Co(II) complex [{2-F-6-MePhN=C(Me)PyC(Me)=NPh-2-Me}CoI₂] (7) with a double pattern of substitution, o-methyl plus o-fluorine in the same imino arm, were synthesized and fully characterized. According to X-ray analysis 4, 5, and 7 exist mostly in the unexpected up-up conformers in the solid state. The Co-N bonds in 7 are shorter than the corresponding Fe-N bonds in the analogous complex 5 by 0.003-0.025 A. This shortening of metal-N bonds going from iron(II) to cobalt(II) complexes can be explained by the smaller van der Waals radius of Co vs. that of Fe. The Fe complexes 4-6 afforded very productive catalysts for the production of α-olefins with a more linear Schultz-Flory distribution of a-olefins and with higher K values than the parent methyl-substituted Fe(II) complex [{2-MePhN=C(Me)PyC(Me)=NPh-2-Me}FeCl ₂] (1). The cobalt complex 7 was found to have very low activity in α-olefin oligomerization experiments within the tested range of temperatures (60-130°C).

Full text of DOI:10.1021/om701204w

Organometallics 2008, 27, 1147–1156
1147
High-Temperature Catalysts for the Production of r-Olefins Based
on Iron(II) and Cobalt(II) Tridentate Bis(imino)pyridine Complexes
with a Double Pattern of Substitution: o-Methyl plus o-Fluorine in
the Same Imino Arm†
Alex S. Ionkin,* William J. Marshall, Douglas J. Adelman, Barbara Bobik Fones,
Brian M. Fish, and Matthew F. Schiffhauer
DuPont Central Research & DeVelopment, Experimental Station, Wilmington, Delaware 19880-0328
Rupert E. Spence and Tuyu Xie
E. I. du Pont Canada Company, Research and DeVelopment Center, Kingston, Ontario, Canada K7L 5A5
ReceiVed NoVember 30, 2007
The new series of bis(imino)pyridine ligands [2-F-6-MePhNdC(Me)PyC(Me)dNPh-2-F-6-Me] (14),
[2-F-6-MePhNdC(Me)PyC(Me)dNPh-2-Me] (19), and [2-F-6-MePhNdC(Me)PyC(Me)dN-Ph-2,4-Me2]
(20) and their corresponding Fe(II) complexes [{2-F-6-Me-PhNdC(Me)PyC(Me)dNPh-2-F-6-Me}FeCl2]
(4), [{2-F-6-MePhNdC(Me)PyC(Me)dNPh-2-Me}FeCl2] (5), and {[2-F-6-MePhNdC(Me)PyC(Me)dNPh-
2,4-Me2]FeCl2} (6) and Co(II) complex [{2-F-6-MePhNdC(Me)PyC(Me)dNPh-2-Me}CoI2] (7) with a
double pattern of substitution, o-methyl plus o-fluorine in the same imino arm, were synthesized and
fully characterized. According to X-ray analysis 4, 5, and 7 exist mostly in the unexpected “up-up”
conformers in the solid state. The Co-N bonds in 7 are shorter than the corresponding Fe-N bonds in
the analogous complex 5 by 0.003-0.025 Å. This shortening of metal-N bonds going from iron(II) to
cobalt(II) complexes can be explained by the smaller van der Waals radius of Co vs. that of Fe. The Fe
complexes 4–6 afforded very productive catalysts for the production of R-olefins with a more linear
Schultz-Flory distribution of R-olefins and with higher K values than the parent methyl-substituted Fe(II)
complex [{2-MePhNdC(Me)PyC(Me)dNPh-2-Me}FeCl2] (1). The cobalt complex 7 was found to have
very low activity in R-olefin oligomerization experiments within the tested range of temperatures (60–130
°C).
productivities.1a The results exceed the values reported for
catalysts used in the current commercial processes, including
the original Ziegler process and Shell’s SHOP technology.2 The
presence of sterically small substituents in the ortho positions
of the imino aryl group, such as only one methyl group in the
ortho positions in complex 1 or the fluorides in the ortho
positions in complex 2 (Scheme 1), are crucial catalyst structural
featuresneededtoproducejustR-olefinsinsteadofpolyethylene.1,3
The combination of o-fluorine and o-trifluoromethyl substituents,
for example in complex 3, was found to enhance the catalytic
performance.4a
The FeII complex 1 with a tridentate bis(imino)pyridine
ligand, bearing only one methyl group in the ortho positions of
the imino aryl group, was initially determined to be the best
for R-olefin production.1c,e However, thorough analysis of
complex 1 as a precatalyst for R-olefin oligomerization at the
commercially desirable temperature of 120 °C revealed some
Introduction
FeII catalysts with tridentate bis(imino)pyridine ligands were
reported to make R-olefin oligomers with perfect Schultz-Flory
distributions, in exceptional purities (97–99%), and with high
* To whom correspondence should be addressed. E-mail: alex.s.ionkin@
usa.dupont.com.
† This is DuPont Contribution No. 8701.
(1) For initial publications, see: (a) Bennett, A. M. A. (DuPont). PCT
Int. Appl. WO9827124 A1, 1998. (b) 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. (c) Small, B. L.;
Brookhart, M. J. Am. Chem. Soc. 1998, 120, 7143. For recent reviews and
papers, see: (d) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. ReV. 2000,
100, 1169. (e) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428. (f) Mecking, S. Coord. Chem. ReV. 2000, 203, 325.
(g) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003, 103, 283. (h)
Britovsek, G. J. P.; Cohen, S. A.; Gibson, V. C.; van Meurs, M. J. Am.
Chem. Soc. 2004, 126, 10701. (i) Barbaro, P.; Bianchini, C.; Giambastiani,
G.; Rios, I. G.; Meli, A.; Oberhauser, W.; Segarra, A. M.; Sorace, L.; Toti,
A. Organometallics 2007, 26, 4639. (j) Bart, S. C.; Lobkovsky, E.; Bill,
E.; Wieghardt, K.; Chirik, P. J. Inorg. Chem. 2007, 46, 7055. (k) Abu-
Surrah, A. S.; Qaroush, A. K. Eur. Polym. J. 2007, 43, 2967. (l) Zhang, S.;
Vystorop, I.; Tang, Z.; Sun, W.-H. Organometallics 2007, 26, 2456. (m)
Small, B. L.; Rios, R.; Fernandez, E. R.; Carney, M. J. Organometallics
2007, 26, 1744. (n) McTavish, S.; Britovsek, G. J. P.; Smit, T. M.; Gibson,
V. C.; White, A. J. P.; Williams, D. J. J. Mol. Catal. A: Chem. 2007, 261,
293. (o) Seitz, M.; Milius, W.; Alt, H. G. J. Mol. Catal. A: Chem. 2007,
261, 246. (p) Kaul, F. A. R.; Puchta, G. T.; Frey, G. D.; Herdtweck, E.;
Herrmann, W. A. Organometallics 2007, 26, 988. (q) Mahdavi, H.; Badiei,
A.; Zohuri, G. H.; Rezaee, A.; Jamjah, R.; Ahmadjo, S. J. Appl. Polym.
Sci. 2007, 103, 1517.
(2) Vogt, D. In Applied Homogeneous Catalysis with Organometallic
Compounds; Cornils, B., Herrmann, W., Eds.; VCH: Weinheim, Germany,
1996; Vol. 1, p 245.
(3) (a) Schmid, M.; Eberhardt, R.; Klinga, M.; Leskela, M.; Rieger, B.
Organometallics 2001, 20, 2321. (b) Moody, L. S.; MacKenzie, P. B.;
Killian, C. M.; Lavoie, G. G.; Ponasik, J. A.; Smith, T. W.; Pearson, J. C.;
Barrett, A. G. M. U.S. Pat. Appl., U. S. 2002/0049135 A1, 2002. (c) Ionkin,
A. S.; Marshall, W. J. Organometallics 2004, 23, 3276. (d) Alt, H. G.;
Licht, E. H.; Licht, A. I.; Schneider, K. J. Coord. Chem. ReV. 2006, 250,
2. (e) Kaul, F. A. R.; Puchta, G. T.; Frey, G. D.; Herdtweck, E.; Herrmann,
W. A. Organometallics 2007, 26, 988.
10.1021/om701204w CCC: $40.75
2008 American Chemical Society
Publication on Web 02/20/2008

1148 Organometallics, Vol. 27, No. 6, 2008
Ionkin et al.
Scheme 1
equiv of methyl iodide, which was followed by hydrolysis,
afforded tert-butyl 2-fluoro-6-methylphenyl carbamate (11). The
deprotection of the BOC group was achieved by treating 11
with trifluoroacetic acid to get the formation of target 2-fluoro-
6-methylphenylamine (12).7
The condensation reaction between 2-fluoro-6-methylphenyl-
amine (12) and commercially available 1-(6-acetylpyridin-2-
yl)ethanone (13) led to a symmetrical bis(imino)pyridine (14)
with the combination of o-fluorine and o-methyl substituents
in one aryl imino moiety. The reaction between iron(II) chloride
and ligand 14 led to the complex 4 (Scheme 4).
Scheme 2
The structure of complex 4 was determined by X-ray analysis.
A crystal of 4 suitable for X-ray analysis was grown from
methylene chloride (Figure 1). It should be noted that o-fluorine
and o-methyl substituents adopt an up–up or mutually syn
conformation.4
Nonsymmetrical complexes of types 5–7 were prepared by
the following methods. Two sets of selective condensations were
used to prepare the ligands for 5–7. The first condensation
reactions between commercially available 1-(6-acetylpyridin-
2-yl)ethanone (13) and o-tolylamine (15) and 2,4-dimethylphe-
nylamine (16) led to the nonsymmetrical (imino)(keto)pyridines
17 and 18, respectively. The second set of selective condensa-
tions between precursors 17 and 18 from one side and the aniline
12 from the other side led to the formation of the target ligands
19 and 20 (Scheme 5).
The reactions between the nonsymmetrical ligands 19 and
20 and iron(II) chloride in THF afforded the final Fe(II)
complexes of 5 and 6. The reaction between cobalt(II) iodide
and the ligand 19 afforded the cobalt analogue 7 (Scheme 6).
According to X-ray analysis, complex 6 exists also as an
up–up or mutually syn conformer (Figure 2).
Solid-State Structures of Fe Precatalysts. Complexes 4 and
5 have a distorted-bipyramidal geometry, which is typical for
iron(II) complexes with tridentate bis(imino)pyridine ligands in
a 1:1 ratio.1 The planes of aryl-substituted arylimino groups of
complexes 4 and 5 are oriented orthogonally to the plane formed
by iron and the three nitrogen atoms. All structures show the
disorder in the aryl groups due to “up-up” or “up-down”
conformations of o-methyl and o-fluorine substituents.4 Detailed
descriptions of these conformers for each structure are shown
in the captions for Figures 1-4. An interesting structural feature
of 4 and 5 is that they exist mostly as “up-up” conformers in
the solid state. There are no short contacts between fluoride
and iron atoms in complexes 4 and 5. The selected bond lengths
of 1, 4, 5, and 7 are presented in Table 1.
important shortcomings. Complex 1 is extremely productive,
but the lifetime of the catalyst is about 3 min at 120 °C. The
resulting exothermic effect is difficult to control. Also, the
Schulz-Flory distribution is not linear. The distribution was
curved, with the light R-olefin fractions (C-4 and C-6) and
heavier fractions (C-14 and up) above the theoretical numbers.
These challenges needed to be addressed through catalyst
modifications.
In this study, we report FeII and CoII complexes with
tridentate bis(imino)pyridine ligands functionalized by the
novel combination of o-fluorine and o-methyl substituents
(Scheme 2), which afford high-temperature catalysts for the
production of R-olefins. Several patterns of the substitutions
were envisioned to make these kinds of complexes that
produce just R-olefins. The complex 4 has a symmetrical
pattern of substitution in both aryl imino groups. The
nonsymmetrical patterns5 in complexes 5–7 have one imino
arm with o-fluorine and o-methyl substituents and in the
second imino aryl group have only one o-methyl or one
o-methyl and a p-methyl (Scheme 2).
Results and Discussion
The axial Fe-N bonds in 4 and 5 are slightly longer than
the corresponding bonds in the methyl-substituted analogue 1.
This bond elongation can be explained by the o-fluorine
substituents being slightly larger than the o-hydrogens. A
comparison of the bond lengths of the imino groups in 4 and 5
with those of 1 shows the same trends. The CdN bonds in 4
and 5 are slightly shorter than in 1. It should be kept in mind,
that due to the disorder, accuracies of the bond lengths are
decreased. Thus, only trends are discussed here briefly.
The structure of cobalt complex 7 is generally similar to that
of its iron(II) analogue 5, except in one feature. The Co-N
bonds in 7 are shorter than the corresponding Fe-N bonds in
the analogous complex 5 by 0.003-0.025 Å. This shortening
of metal-N bonds on going from iron(II) to cobalt(II) com-
plexes has been described in the literature4,8,9 and could be a
reflection of the smaller van der Waals radius of Co vs. Fe.10,11
Synthesis. The direct ortho-metalation methodology with
subsequent functionalization was used to assemble combinations
of o-fluorine and o-methyl substituents in one aryl imino
moiety.6 Thus, commercially available 2-fluorophenylamine (8)
was protected with a tert-butoxycarbonyl (BOC) group to form
the corresponding tert-butyl 2-fluorophenyl carbamate (9)
(Scheme 3). Dilithiation of compound 9 by slightly more than
2 equiv of tert-butyllithium at low temperature yielded the
yellow dianionic species 10. The reaction between 10 and 1
(4) (a) Tellmann, K. P.; Gibson, V. C.; White, A. J. P.; Williams, D. J.
Organometallics 2005, 24, 280. (b) Ionkin, A. S.; Marshall, W. J.; Adelman,
D. J.; Bobik Fones, B.; Fish, B. M.; Schiffhauer, M. F. Organometallics
2006, 25, 2978.
(5) (a) Small, B. L.; Brookhart, M. Macromolecules 1999, 32, 2120.
(b) De Boer, E.; Johannes, M.; Deuling, H. H.; Van Der Heijden, H.;
Meijboom, N.; Van Oort, A. B.; Van Zon, A. PCT Int. Appl. WO
2001058874 A1, 2001.
(6) (a) Mucowski, J. M.; Venuti, M. C. J. Org. Chem. 1980, 45, 4798.
(b) Clark, R. D.; Mucowski, J. M.; Souchet, M.; Repke, D. B. Synlett 1990,
207.
(7) Meng, D.; Parker, D. L., Jr.; Ratcliffe, R. W.; Wilkening, R. R. PCT
Int. Appl. WO 2003015761 A1, 2003.

Fe(II) and Co(II) Tridentate Bis(imino)pyridine Complexes
Organometallics, Vol. 27, No. 6, 2008 1149
Scheme 3
Scheme 4
Scheme 5
Scheme 6
It is possible to observe 19F NMR spectra of complexes 4–6,
however, with very broad lines associated with the paramagnetic
complexes,1 which preclude investigation of the conformeric
behavior in the solution. For example, the half-width of the line
of complex 4 at 30 °C in tetrachloroethane-d2 is 1961 Hz at
-89.66 ppm, and the half-width of the line of complex 4 at
110 °C is still broad at 251 Hz.
Oligomerization of Ethylene to r-Olefins by the Fe(II)
Dichloride Complexes 1 and 4-6. Oligomerzations were done
according to the procedures given in the Experimental Section
under General Conditions of the Oligomerizations. One measure
of catalyst performance is its lifetime. Catalyst lifetimes were
measured as the period from the beginning of ethylene uptake
until flow was no longer detected by the ethylene mass
flowmeter. Due to the use of this method, the lifetime of a
catalyst depends on the amount of precatalyst added because
Figure 1. ORTEP drawing of {2,6-bis[1-(2-fluoro-6-methylphenyl-
imino)ethyl]pyridine}iron(II) chloride (4). The crystal structure is
drawn with thermal ellipsoids at the 30% probability level. The
structure is displayed showing the methyl up–up disorder. The
up–down or trans conformer is also present, on the basis of the
occupancy refinement of the fluorine and methyl carbons and weak
residual electron density peaks that could not be fully modeled.
The dichloromethane solvent molecule is omitted for clarity.
(8) Bianchini, C.; Mantovani, G.; Meli, A.; Migliacci, F.; Zanobini, F.;
Laschi, F.; Sommazzi, A. Eur. J. Inorg. Chem. 2003, 1620.
(9) Kooistra, T. M.; Hekking, K. F. W.; Knijnenburg, Q.; de Bruin, B.;
Budzelaar, P. H.; de Gelder, R.; Smits, J. M. M.; Gal, A. W. Eur. J. Inorg.
Chem. 2003, 648.
(10) Long, G. J.; Clarke, P. J. Inorg. Chem. 1978, 17, 1394.
(11) Batsanov, S. S. THEOCHEM 1999, 468, 151.

1150 Organometallics, Vol. 27, No. 6, 2008
Ionkin et al.
of a precatalyst does not necessarily lead to an increase in
lifetime, because a higher load of precatalyst can create a large
exothermic effect, which greatly accelerates catalyst decomposi-
tion. This is illustrated in Figure 5, where precatalyst 1 is used
at two concentrations: 0.06 and 0.43 µmol. Both runs gave
similar lifetimes of about 3 min, but the productivities (kg/g)
were 458 for the former and only 94 for the latter. The initial
dramatic drop of ethylene pressure from 700 to 500 psig,
recorded for the higher loading, shows that the oligomerization
was limited by the ethylene supply. For these control reasons,
the amount of precatalyst used in an experiment depended on
the activity of the catalyst. Oligomerizations were repeated for
a given precatalyst until the amount added did not result in an
initial exothermic effect of >2 °C. Equally important, enough
precatalyst was added to make an amount of R-olefins readily
quantified by the analytical methods. The production of similar
amounts of R-olefins in all runs gave the best possible basis for
comparisons.
Figure 2. ORTEP drawing of {(2-fluoro-6-methylphenyl)[1-[6-(1-
(o-tolylimino)ethyl)pyridin-2-yl]ethylidene]amine}iron(II) chloride
(5). The crystal structure is drawn with thermal ellipsoids at the
30% probability level. The structure is always the methyl up–up
conformer, on the basis of the occupancy refinement for fluorine
positions and methyl carbons. The fluorine atom is disordered left
to right, with F1 being as shown or near H19a in a 58/42 ratio.
The dichloromethane solvent molecule is omitted for clarity.
Ethylene uptake curves for precatalysts 1 and 4–6 are shown
in Figure 6. Catalysts 1 and 4 have comparable lifetimes, as do
5 and 6. The only clear distinguishing structural difference
between the two groupings is that the former has a symmetric
pattern of substitutions and the latter does not.
The results and conditions of oligomerization runs in a 1.0 L
autoclave are presented in Table 2. The cobalt-based complex
7 was found to have very low activity in R-olefin oligomeriza-
tion experiments within the tested temperature range of 60–130
°C and so did not make enough amounts of product for
evaluation. Entries 3 and 4 in Table 2 are duplicates for
precatalyst 4. There is close agreement for all reported values
across the table.
The most significant value involves the Schultz-Flory distri-
bution constant, K. It is a measure of the molecular weight
distribution of the olefins obtained and is defined as12 K )
n(Cn+2 olefin)/n(Cn olefin), wherein n(Cn olefin) is the number
of moles of olefin containing n carbon atoms and n(Cn+2 olefin)
is the number of moles of olefin containing n + 2 carbon atoms,
or in other words the next higher oligomer of Cn olefin. The K
factor is usually preferred to be in the range of about 0.6 to
about 0.8 to make R-olefins of the most commercial interest. It
is also desirable to be able to vary this factor to make a range
of products.
Figure 3. {(2-Fluoro-6-methylphenyl)[1-[6-(1-(o-tolylimino)eth-
yl)pyridin-2-yl]ethylidene]amine}cobalt(II) iodide (7). The crystal
structure is drawn with thermal ellipsoids at the 30% probability
level. The structure is displayed showing well resolved up–down
disorder with a 53/47 ratio in favor of the up–up conformation (solid
bonds). The up–down or trans conformation is shown with dashed
bonds. Residual electron density near H11a suggests additional
disorder that could not be fully modeled. The dichloromethane
solvent molecule is omitted for clarity.
As seen in Table 2, precatalysts 4–6 gave R-olefins with K
values above 0.6, which make them attractive from a commercial
point of view. The R-olefins with K values below 0.6 are richer
in butenes, which have minimal commercial value. The value
of K changes significantly as a function of precatalyst structure.
A possible explanation could involve the different number
of fluorines present in the precatalysts. The K value drops with
the number of fluorines in the structures. For the 120 °C runs,
precatalyst 4 has two fluorines and a K value of 0.72 and
precatalyst 1 has no fluorines and the lowest K value of 0.59.
This would suggest that more steric hindrance around the active
catalytic center increases the ratio of propagation to termination/
transfer rates to raise K values. This is the normal dependency
for the Versipol family of catalysts.1 An increase of the steric
bulk around iron usually leads to an increase in the K value.8,13
Referring again to Table 2, the percent solids of total LAO
are the percentages of R-olefins with >C28 chain lengths. Since
some of these will precipitate from the carrier solvent, o-xylene,
it is desirable to run oligomerizations at temperatures as high
Figure 4. ORTEP drawing of {2,6-bis[1-(2-methylphenylimino)-
ethyl]pyridine}iron(II) chloride (1). The crystal structure of 1 is
drawn with thermal ellipsoids at the 50% probability level. The
structure is displayed showing well resolved up–down disorder with
a 72/28 ratio in favor of the up–up conformation (solid bonds).
The up–down or trans conformation is shown with dashed bonds.
The dichloromethane solvent molecule is omitted for clarity.
of the fixed lower detection limit of the ethylene mass flowmeter.
The ethylene uptake for the remaining 10% of an initial large
charge of precatalyst will still be seen, but not if the initial
charge was much smaller. However, the use of a large excess
(12) Elvers, B., et al., Ed. Ullmann’s Encyclopedia of Industrial
Chemistry; VCH: Weinheim, Germany, 1989; Vol. A13, pp 243–247 and
275-276.

Fe(II) and Co(II) Tridentate Bis(imino)pyridine Complexes
Organometallics, Vol. 27, No. 6, 2008 1151
Table 1. Selected Bond Lengths (Å) for 1, 4, 5, and 7
1
4
5
7
axial (imino) N-M
axial (imino) N-M
basal (central) N-M
CdN
2.2303(16) (Fe-N1)
2.2424(17) (Fe-N3)
2.0943(16) (Fe-N2)
1.281(2) (N1-C1)
1.287(3) (N3-C7)
2.247(3) (Fe-N1)
2.244(3) (Fe-N3)
2.108(3) (Fe-N2)
1.274(5) (N1-C1)
1.281(5) (N3-C7)
2.235(2) (Fe-N1, aryl-F side)
2.230(2) (Fe-N3)
2.232(3) (Co-N3, aryl-F side)
2.205(3) (Co-N1)
2.106(2) (Fe-N2)
2.031(3) (Co-N2)
1.279(4) (N1-C1, aryl-F side)
1.280(4) (N3-C7)
1.278(5) (N3-C7, aryl-F side)
1.276(5) (N1-C1)
CdN
as 120 °C to keep more of these in solution to delay system
plugging and to use a catalyst, which minimizes their formation
for a given product distribution. A catalyst which makes a
distribution with a high-molecular-weight tail on an otherwise
normally distributed product would be undesirable. Looking at
the solids’ data in Table 2, there is no clear trend for solids vs.
any of the variables listed for the 120 °C oligomerizations or
as a function of structural differences.
The productivities of the precatalysts are also given in Table
2. At 120 °C, precatalysts 4–6 have productivities that are less
than the average value for 1. While the relative differences are
not as great here as they were for the argument above concerning
K values and the effect of steric hindrance at the active center,
the same trend is seen here. The highest productivity is seen
for 1, which has only two ortho substituents, and the lowest is
seen for 4, which has four. The productivities for precatalysts
5 and 6 with three substituents are nearly comparable to each
other but fall between those of 1 and 4. This indicates that an
increase in steric hindrance in the ortho positions slows access
of ethylene to the metal center of the catalyst.
In Table 2 is a list of productivities for precatalyst 4 as a
function of temperature. There is a clear trend of a decrease in
productivity with increasing temperature. Provided the diffusion
of ethylene to the active centers was not limiting, this suggests
that catalyst decomposition is a much stronger function of
temperature than is propagation. Interestingly, the constant K
value over this temperature interval suggests that the ratio of
propagation to termination rates did not change.
The right-hand column of Table 2 is a list of the correlation
coefficients (SFD R2) for the goodness of fit of the Schultz-Flory
distribution equation to the experimental data. Ideally, a catalyst
will make R-olefins which fit the Schultz-Flory distribution
equation. One measure of the approach to ideality comes from
plotting ln(mp/Dp) vs. Dp - 2 according to the equation ln(mp/
Dp) ) ln((1 - K)2/(2 - K)) + (Dp - 2) ln K, where mp is the
Figure 5. Effect of the concentrations of parent precatalyst 1 on the temperature and ethylene flow.
Figure 6. Graph of ethylene uptake of complexes 1 and 4-6 in the catalytic oligomerization of ethylene.

1152 Organometallics, Vol. 27, No. 6, 2008
Ionkin et al.
Table 2. r-Olefins from Ethylene Oligomerizations by Iron(II) Complexes 1 and 4-6a
precat.
(amt, µmol)
amt of cocat.
MMAO, mmol
K value Schultz-Flory
kg of LAO/g
of cat.
solids of
entry
temp, °C
distribnb
total LAO, %c
SFD R2
1
2
3
4
5
6
7
4 (0.10)
4 (0.20)
4 (0.16)
4 (0.10)
5 (0.21)
6 (0.20)
1 (0.06)
2.26
2.26
2.26
2.26
2.26
2.26
1.13
135
125
120
120
120
120
120
0.71
0.72
0.72
0.72
0.61
0.62
0.59
19
155
247
246
263
278
458
9.72
4.76
6.05
5.44
3.43
7.71
3.44
0.9831
0.9976
0.9934
0.9963
0.9974
0.9973
0.9862
a Conditions: solvent o-xylene, 600 mL; pressure, 700 psig. b Determined from GC, using extrapolated values for C-10 and C-12. c Xylene-insoluble
fraction of R-olefins.
Table 3. Summary of Crystal Data, Data Collection, and Structural Refinement Parameters for 1, 4, 5, and 7
1
4
5
7
empirical formula
fw
C24H25Cl4FeN3
553.12
C24H23Cl4F2FeN3
589.1
C24H24Cl4FeN3F
571.11
C24H24Cl2CoI2N3F
757.09
cryst color, form
cryst syst
space group
a (Å)
blue, needle
monoclinic
P21/c
10.4140(5)
blue, rect. plate
monoclinic
I2/a
15.867(5)
black, needle
monoclinic
C2/c
25.6657(10)
red, prism
monoclinic
P21/n
13.3251(11)
b (Å)
15.2465(8)
15.220(5)
15.2699(6)
14.5228(12)
c (Å)
15.8488(8)
21.709(7)
15.7230(6)
14.7832(12)
R (deg)
90
90
93.565(6)
90
5232(3)
90
90
ꢀ (deg)
92.3650(10)
90
2514.3(2)
122.9210(10
90
5172.5(3)
107.9410(10
90
2721.7(4)
γ (deg)
V (Å3)
Z
4
8
8
4
density (g/cm3)
1.461
1.042
1136
1.496
1.017
2400
1.467
1.021
2336
1.848
3.12
1460
abs µ (mm-1
F(000)
)
cryst size (mm)
temp (°C)
scan mode
0.320 × 0.060 × 0.020
0.500 × 0.120 × 0.020
0.400 × 0.050 × 0.010
0.250 × 0.130 × 0.130
-100
-100
-100
-100
ω
ω
ω
ω
detector
Bruker-CCD
Bruker-CCD
Bruker-CCD
Bruker-CCD
θmax (deg)
27.96
37 670
6038
0.055
27.27
22 010
5845
0.065
28.43
22 038
6456
0.049
30.44
52 377
8056
0.047
no. of obsd rflns
no. of unique rflns
Rmerge
no. params
358
1.02
315
1.04
313
1.06
298
1.06
Sb
R indices (I > 2σ(I))a
R indices (all data)a
max diff peak, hole (e/Å3)
wR2 ) 0.075, R1 ) 0.036
wR2 ) 0.084, R1 ) 0.060
0.288, -0.325
wR2 ) 0.142, R1 ) 0.059
wR2 ) 0.166, R1 ) 0.097
1.189, -0.824
wR2 ) 0.123, R1 ) 0.051
wR2 ) 0.140, R1 ) 0.086
0.888, -0.647
wR2 ) 0.095, R1 ) 0.038
wR2 ) 0.104, R1 ) 0.059
1.931, -0.899
2
2 2
2
2 2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|; wR2 ) {∑[w(Fo - Fc ) ]/∑[w(Fo2)2]}1/2 (sometimes denoted as Rw2). b GOF ) S ) {∑[w(Fo - Fc ) ]/(n - p)}1/2
,
where n is the number of reflections and p is the total number of refined parameters.
weight fraction of the R-olefin, Dp is the degree of polymeri-
zation of the R-olefin, and K is the Schultz-Flory distribution
factor.
functionalized with double patterns of substitutions, o-methyl
plus o-fluorine in the same imino arm, were synthesized and
fully characterized. The Fe-based bis(imino)pyridine com-
plexes 4–6 afforded very active catalysts for the production
of R-olefins with more ideal Schultz-Flory distributions of
R-olefins and with higher K values than the parent methyl-
substituted Fe(II) complex 1. The cobalt complex 7 was found
to have very low activity in the oligomerization experiments,
which is in agreement with the low activity of such cobalt
complexes.1 On the basis of limited observations, it appears
the nonsymmetric precatalysts 5 and 6 had longer lifetimes
than the symmetric precatalysts 1 and 4. Steric hindrance
around the active center, in terms of the number of ortho
substituents, appears to affect the product distributions and
catalyst productivities. More steric hindrance seems to shift
the distributions to longer chain R-olefins but reduces the
productivities.
The R2 values for plots of experimental data according to
the above equation are given in Table 3. There are no obvious
trends. Possibly a clearer way to see that there are differences
in deviations from ideality, especially at the low-molecular-
weight end of the distribution, is achieved by plotting ideal
distributions with the experimental data. Several such plots are
shown in Figures 7-9. The solid lines are the ideal Schultz-Flory
product distributions predicted for the specified K factor, and
the symbols are the experimental data points. The magnitudes
of the deviations of the data points from their respective solid
lines are an indication of the ideality of the catalyst performance.
Precatalyst 1 generally shows a larger deviation at the low
carbon number end in Figures 7-9 than do the other precata-
lysts. This means catalyst 1 makes more C6 and C8 products
than do the other catalysts and so has a less ideal product
distribution.
Judging from all of these criteria, the complex 5 was found
to be the best catalyst for high temperature production of
R-olefins in this study.
To summarize, the new Fe-based bis(imino)pyridine com-
plexes 4–6 and Co-based bis(imino)pyridine complex 7,

Fe(II) and Co(II) Tridentate Bis(imino)pyridine Complexes
Organometallics, Vol. 27, No. 6, 2008 1153
Figure 7. Distribution of R-olefins from C-2 to C-28 for precatalysts 1 and 4 and ideal Schultz-Flory distributions with K factors at 0.59
and 0.72.
Figure 8. Distribution of R-olefins from C-2 to C-28 for precatalysts 1 and 5 and ideal Schultz-Flory distribution with K factors at 0.59
and 0.61.
tert-Butyl 2-Fluorophenyl Carbamate (9). A 50 g (0.450 mol)
amount of 2-fluorophenylamine (8) was mixed in 500 mL of dry
THF. To this was added 100 g (0.458 mol) of di-tert-butyl
dicarbonate. This mixture was then stirred under a nitrogen
atmosphere and heated in a water bath to 60 °C for 3 days. The
solution was extracted with ethyl acetate, and the organic fraction
was then washed three times with 1 M citric acid and left overnight
to dry over magnesium sulfate. The solvent was then removed and
the crude product was dissolved in hexane. This solution was then
filtered over Celite to remove the solids and the solvent removed
to leave a yellow liquid. Further purification was achieved through
distillation; the cleanest fractions came off as a 54–57 °C vapor at
20 × 10-3 mm Hg to form a viscous clear liquid. The yield of 9
Experimental Section
All air-sensitive compounds were prepared and handled under a
N2/Ar atmosphere using standard Schlenk and inert-atmosphere box
techniques. Anhydrous solvents were used in the reactions. Solvents
were distilled from drying agents or passed through columns under
an argon or nitrogen atmosphere. Anhydrous iron(II) chloride, 1-(6-
acetylpyridin-2-yl)ethanone, 2-fluorophenylamine, di-tert-butyl di-
carbonate, 1.7 M tert-butyllithium in pentane, iodomethane, 2,4-
dimethylphenylamine, o-tolylamine, and n-butanol were purchased
from Aldrich. MMAO was purchased from Akzo-Nobel. Complex
1 was prepared according to the literature.14
(13) 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, 2, 431.
(14) Small, B. L.; Brookhart, M.; Bennett, A. M. A. J. Am. Chem. Soc.
1998, 120, 4049.

1154 Organometallics, Vol. 27, No. 6, 2008
Ionkin et al.
Figure 9. Distribution of R-olefins from C-2 to C-28 for precatalysts 1 and 6 and ideal Schultz-Flory distribution with K factors at 0.59
and 0.63.
was 74.1 g (78%). 1H NMR (500 MHz, C6D6, TMS): δ 1.40 (s, 9
H, Me), 6.65–6.80 (m, 4H, arom H), 8.40 (br, 1H, N-H). 19F NMR
(500 MHz, C6D6): δ -136.5 (br, 1F).
2.05 (s, 6 H, Me), 2.36 (s, 6 H, Me), 6.60–6.90 (m, 6H, arom H),
7.20 (t, 3JHH ) 7.8 Hz, 1H, Py H), 8.40 (d, 3JHH ) 7.8 Hz, 2H, Py
H). 19F NMR (500 MHz, C6D6): δ -127.7 (br, 2F). 13C NMR (500
MHz, C6D6 (selected signals)): δ 169.6 (CdN). Anal. Calcd for
C23H21F2N3 (mol wt 377.43): C, 73.19; H, 5.61; N, 11.13. Found:
C, 73.42; H, 5.68; N, 11.38.
{2,6-Bis[1-((2-fluoro-6-methylphenyl)imino)ethyl]pyridine}-
iron(II) Chloride (4). 0.94 g (0.0025 mol) of 2,6-Bis(1-(2-fluoro-
6-methylphenylimino)ethyl)pyridine (14) was dissolved in 30
mL of THF. 0.30 g (0.0024 mol) of Iron(II) chloride was added
in the reaction mixture by one portion. The resultant blue
precipitate was filtered after 12 h of stirring, washed twice by
20 mL of pentane, and dried at 1-mm vacuum. Yield of 2,6-
bis(1-(2-fluoro-6-methylphenylimino)ethyl)pyridineiron(II) chlo-
ride (4) was 3.19 g (48%). Anal. Calculated for C23H21Cl2F2FeN3
(Mol. Wt.: 504.18): C, 54.79; H, 4.20; N, 8.33. Found: C, 55.03;
H, 4.37; N, 8.40. The structure was determined by X-ray analysis.
A crystal suitable for X-ray analysis was grown from methylene
chloride.
tert-Butyl 2-Fluoro-6-methylphenyl Carbamate (11). A 20 g
(0.095 mol) amount of tert-butyl 2-fluorophenyl carbamate (9) was
dissolved in 200 mL of dry THF and cooled to -78 °C. Once the
mixture was cooled, 139 mL of 1.7 M tert-butyllithium in pentane
solution was added. The mixture was then warmed to -15 °C over
a 2 h period. At that point it was cooled back down to -78 °C and
6.47 mL of iodomethane was added slowly. The mixture was then
warmed to 0 °C, and 20 mL of saturated ammonium chloride
solution was added slowly. The mixture was then extracted with
ethyl acetate and washed with water three times. The solution was
dried over magnesium sulfate overnight. It was then filtered, and
the solvent was removed by vacuum. The precipitate from the
residue was filtered off and washed with petroleum ether to leave
a white powder. The yield of 11 was 14.60 g (68%). 1H NMR
(500 MHz, C6D6, TMS): δ 1.45 (s, 9 H, Me), 2.35 (s, 3H, Me),
6.10 (br, 1H, N-H), 6.80 (m, 1H, arom H), 6.90 (m, 1H, arom H),
7.00 (m, 1H, arom H). 19F NMR (500 MHz, C6D6): δ - 128.0 (br,
1F).
1-{6-[1-(o-Tolylimino)ethyl]pyridin-2-yl}ethanone (17). A 57.11
g amount (0.35 mol) of 1-(6-acetylpyridin-2-yl)ethanone (13), 25.0 g
(0.23 mol) of o-tolylamine (15), 200 mL of methanol, and a few
crystals of p-toluenesulfonic acid were stirred at room temperature
for 36 h in 1.0 L flask under a flow of nitrogen. The resultant yellow
precipitate was filtered and washed with 20 mL of methanol. It
was then dried under 1 mm vacuum overnight. The yield of 1-{6-
[1-(o-tolylimino)ethyl]pyridin-2-yl}ethanone (17) was 8.13 g (14%)
2-Fluoro-6-methylphenylamine (12). A solution of 7 g (0.031
mol) of tert-butyl 2-fluoro-6-methylphenyl carbamate (11) in 30
mL of trifluoroacetic acid was stirred for 1 h. The excess
trifluoroacetic acid was removed under vacuum, and the residue
was diluted with methylene chloride. This was then poured into a
slurry of sodium carbonate and methylene chloride, additional
sodium carbonate was added as needed, and the mixture was stirred
for 1 h. This solution was filtered and the solvent removed. The
residue was then distilled, and the desired fraction came off as a
63 °C vapor at 15 mbar and crystallized as an off-white solid. The
1
as a yellow solid. H NMR (500 MHz, CD2Cl2, TMS): δ 2.00 (s,
3 H, Me), 2.20 (s, 3 H, Me), 2.65 (s, 3 H, Me), 6.55 (m, 1H, arom
3
H), 6.90 (m, 1H, arom H), 7.10 (m, 2H, arom H), 7.70 (t, JHH
)
3
8.0 Hz, 1H, Py H), 7.90 (d, JHH ) 8.0 Hz, 1H, Py H), 8.45 (d,
3JHH ) 8.0 Hz, 1H, Py H). 13C NMR (500 MHz, CD2Cl2, TMS
(selected signals)): δ 166.6 (CdN), 200.1 (CdO). Anal. Calcd for
C16H16N2O (mol wt 252.31): C, 76.16; H, 6.39; N, 11.10. Found:
C, 76.24; H, 6.46; N, 11.36.
1
yield of 12 was 2.47 g (64%). H NMR (500 MHz, C6D6, TMS):
δ 1.60 (s, 3 H, Me), 3.00 (br, 2H, N-H), 6.40 (m, 1H, arom H),
6.60 (m, 1H, arom H), 6.80 (m, 1H, arom H). 19F NMR (500 MHz,
C6D6): δ -137.1 (s, 1F).
2,6-Bis{1-[(2-fluoro-6-methylphenyl)imino]ethyl}pyridine (14).
A 1.1 g amount (0.0068 mol) of 1-(6-acetylpyridin-2-yl)ethanone
(13), 1.7 g (0.0136 mol) of 2-fluoro-6-methylphenylamine (12), 100
mL of toluene, and 100 g of fresh molecular sieves were kept at
100 °C for 3 days. The molecular sieves were removed by filtration.
The solvent was removed in a rotary evaporator, and the residue
was recrystallized from 20 mL of ethanol. The yield of 2,6-bis{1-
[(2-fluoro-6-methylphenyl)imino]ethyl}pyridine (14) was 1.78 g
(70%) as a pale yellow solid. 1H NMR (500 MHz, C6D6, TMS): δ
(2-Fluoro-6-methylphenyl){1-[6-(1-(o-tolylimino)ethyl)pyridin-
2-yl]ethylidene}amine (19). A 6.05 g amount (0.024 mol) of 1-{6-
[1-(o-tolylimino)ethyl]pyridin-2-yl}ethanone (17), 2.5 g (0.01997
mol) of 2-fluoro-6-methylphenylamine (12), 100 mL of toluene,
and 100 g of fresh molecular sieves were kept at 100 °C for 3
days. The molecular sieves were removed by filtration. The
solvent was removed in a rotary evaporator, and the residue was
recrystallized from 20 mL of ethanol. The yield of (2-fluoro-
6-methylphenyl){1-[6-(1-(o-tolylimino)ethyl)pyridin-2-yl]ethyl-

Fe(II) and Co(II) Tridentate Bis(imino)pyridine Complexes
Organometallics, Vol. 27, No. 6, 2008 1155
1
idene}amine (19) was 6.98 g (81%) as a pale yellow solid. H
NMR (500 MHz, CD2Cl2, TMS): δ 2.10 (s, 3 H, Me), 2.15 (s,
3 H, Me), 2.30 (s, 3 H, Me), 2.35 (s, 3 H, Me), 6.60 (m, 1H,
arom H), 6.90–7.15 (m, 6H, arom H), 7.90 (m, 1H, Py H), 8.40
(m, 2H, Py H). 19F NMR (500 MHz, C6D6): δ -128.7 (br, 1F).
13C NMR (500 MHz, C6D6 (selected signals)): δ 170.2 (CdN),
167.3 (CdN). Anal. Calcd for C23H22FN3 (mol wt 359.44):
C, 76.85; H, 6.17; N, 11.69. Found: C, 77.02; H, 6.31; N,
11.83.
of stirring, washed twice with 20 mL of pentane, and dried under
1 mm vacuum. The yield of {[1-[6-[1-((2-fluoro-6-methylphenyl)-
imino)ethyl]pyridin-2-yl]ethylidene](2,4-dimethylphenyl)amine}-
iron(II) chloride (6) was 2.48 g (91%). Anal. Calcd for
C24H24Cl2FFeN3 (mol wt 500.22): C, 57.63; H, 4.84; N, 8.40.
Found: C, 57.73; H, 5.01; N, 8.52. The structure was determined
by X-ray analysis. A crystal suitable for X-ray analysis was grown
from methylene chloride.
{(2-Fluoro-6-methylphenyl)[1-[6-(1-(o-tolylimino)ethyl)pyri-
din-2-yl]ethylidene]amine}cobalt(II) Iodide (7). A 1.00 g amount
(0.00278 mol) of (2-fluoro-6-methylphenyl){1-[6-(1-(o-tolylimi-
no)ethyl)pyridin-2-yl]ethylidene}amine (19) was dissolved in 30
mL of THF. A 0.78 g amount (0.0025 mol) of cobalt(II) iodide
was added to the reaction mixture in one portion. The resultant
brown precipitate was filtered after 12 h of stirring, washed twice
with 20 mL of pentane, and dried under 1 mm vacuum. The yield
of {(2-fluoro-6-methylphenyl)[1-[6-(1-(o-tolylimino)ethyl)pyridin-
2-yl]ethylidene]amine}cobalt(II) iodide (7) was 1.19 g (71%). Anal.
Calcd for C23H22CoFI2N3 (mol wt 672.18): C, 41.10; H, 3.30; N,
6.25. Found: C, 41.29; H, 3.42; N, 6.37. The structure was
determined by X-ray analysis. A crystal suitable for X-ray analysis
was grown from methylene chloride.
{(2-Fluoro-6-methylphenyl)[1-[6-(1-(o-tolylimino)ethyl)pyri-
din-2-yl]ethylidene]amine}iron(II) Chloride (5). A 2.00 g amount
(0.00556 mol) of (2-fluoro-6-methylphenyl){1-[6-(1-(o-tolylimi-
no)ethyl)pyridin-2-yl]ethylidene}amine (19) was dissolved in 30
mL of THF. A 0.63 g amount (0.0050 mol) of iron(II) chloride
was added to the reaction mixture in one portion. The resultant
blue precipitate was filtered after 12 h of stirring, washed twice
with 20 mL of pentane, and dried under 1 mm vacuum. The
yield of {(2-fluoro-6-methylphenyl)[1-[6-(1-(o-tolylimino)eth-
yl)pyridin-2-yl]ethylidene]amine}iron(II) chloride (5) was 2.13 g
(88%). Anal. Calcd for C23H22Cl2FFeN3 (mol wt 486.19): C,
56.82; H, 4.56; N, 8.64. Found: C, 56.94; H, 4.63; N, 8.69. The
structure was determined by X-ray analysis. A crystal suitable
for X-ray analysis was grown from methylene chloride.
General Conditions of the Oligomerizations. Ethylene oligo-
merizations were done in a 1 L 316 stainless steel Autoclave
Engineers Zipperclave. The catalyst and cocatalyst were charged
separately using stainless steel injection tubes. The complexes
1 and 4-7 were activated by modified methylaluminoxane
(MMAO). The steps for a typical oligomerization are as follows.
The injectors were charged in a glovebox. The cocatalyst was
obtained as a 7 wt % solution in o-xylene and was charged as
such into the injector assembly along with a 10 mL chase of
o-xylene. The catalysts were prepared as suspensions in o-xylene
(10 mg/100 mL). A sample was pulled from a well-stirred
suspension and was added to a 10 mL charge of o-xylene. The
injectors were attached to autoclave ports equipped with dip
tubes. Nitrogen was sparged through the loose fittings at the
attachment points prior to making them tight. The desired charge
of o-xylene (600 mL was the usual amount) was then pressured
into the autoclave. The agitator (1000 rpm) and heater were
turned on. When the desired temperature was reached, the
cocatalyst was charged into the clave by blowing ethylene down
through the cocatalyst injector. After a significant pressure rise
was seen in the autoclave to indicate the cocatalyst and chase
solvent had entered, the injector was isolated from the process
using its valves. The pressure controller was then set to 5 psig
below the desired ethylene operating pressure and was put in
the automatic mode to allow it to control the operation of the
ethylene addition valve. When the pressure was 5 psig below
the desired operating pressure, the controller was put into manual
mode and the valve was set to 0% output. When the batch
temperature was stable at the desired value, the catalyst was
injected using enough nitrogen such that the reactor pressure
was boosted to the desired pressure. At the same time as the
catalyst injection, the pressure controller was put in the automatic
mode and the oligomerization was underway. The 5 psi boost
was obtained routinely by having a small reservoir between the
nitrogen source and the catalyst injector. A valve was closed
between the nitrogen source and the reservoir prior to injecting
the catalyst so that the same volume of nitrogen was used each
time to inject the catalyst suspension. To stop the oligomeriza-
tion, the pressure controller was put into manual, the ethylene
valve was closed, and the reactor was cooled. The reaction time
was 1 h.
1-{6-[1-((2,4-Dimethylphenyl)imino)ethyl]pyridin-2-yl}etha-
none (18). A 37.0 g amount (0.23 mol) of 1-(6-acetylpyridin-
2-yl)ethanone (13), 25.0 g (0.21 mol) of 2,4-dimethylpheny-
lamine (16), 300 mL of n-propanol, and a few crystals of
p-toluenesulfonic acid were stirred at room temperature for 36 h
in a 1.0 L flask under a flow of nitrogen. The resultant yellow
precipitate was filtered and washed with 20 mL of methanol. It
was then dried under 1 mm vacuum overnight. The yield of 1-{6-
[1-((2,4-dimethylphenyl)imino)ethyl]pyridin-2-yl}ethanone (18)
1
was 11.20 g (21%) as a yellow solid. H NMR (500 MHz, Tol-
d8, TMS): δ 2.10 (s, 6 H, Me), 2.20 (s, 3 H, Me), 2.25 (s, 3 H,
Me), 2.56 (s, 3 H, Me), 6.50 (m, 1H, arom H), 6.90 (m, 2H,
arom H), 7.40 (t, 3JHH ) 8.0 Hz, 1H, Py H), 7.90 (d, 3JHH ) 8.0
3
Hz, 1H, Py H), 8.45 (d, JHH ) 8.0 Hz, 1H, Py H). 13C NMR
(500 MHz, CD2Cl2, TMS (selected signals)): δ 162.2 (CdN),
198.7 (CdO). Anal. Calcd for C17H18N2O (mol wt 266.34):
C, 76.66; H, 6.81; N, 10.52. Found: C, 76.73; H, 7.03; N,
10.70.
{1-[6-[1-((2-Fluoro-6-methylphenyl)imino)ethyl]pyridin-2-yl]-
ethylidene}(2,4-dimethylphenyl)amine (20). A 5.00 g amount
(0.0187 mol) of 1-{6-[1-((2,4-dimethylphenyl)imino)ethyl]py-
ridin-2-yl}ethanone (18), 2.82 g (0.023 mol) of 2-fluoro-6-
methylphenylamine (12), 100 mL of toluene, and 100 g of fresh
molecular sieves were kept at 100 °C for 3 days. The molecular
sieves were removed by filtration. The solvent was removed in
a rotary evaporator, and the residue was recrystallized from 20
mL of ethanol. The yield of {1-[6-[1-((2-fluoro-6-methylphe-
nyl)imino)ethyl]pyridin-2-yl]ethylidene}(2,4-dimethylphenyl)-
1
amine (20) was 5.47 g (78%) as a pale yellow solid. H NMR
(500 MHz, C6D6, TMS): δ 1.90 (s, 3 H, Me), 1.95 (s, 3 H, Me),
2.10 (s, 3 H, Me), 2.20 (s, 3 H, Me), 2.30 (s, 3 H, Me), 6.45 (m,
1H, arom H), 6.60–6.90 (m, 5H, arom H), 7.10 (m, 1H, Py H),
8.30 (m, 2H, Py H). 19F NMR (500 MHz, C6D6): δ -127.6 (br,
1F). 13C NMR (500 MHz, C6D6 (selected signals)): δ 169.4
(CdN), 166.5 (CdN). Anal. Calcd for C24H24FN3 (mol wt
373.47): C, 77.18; H, 6.48; N, 11.25. Found: C, 77.19; H, 6.53;
N, 11.28.
{[1-[6-[1-((2-Fluoro-6-methylphenyl)imino)ethyl]pyridin-2-yl]-
ethylidene](2,4-dimethylphenyl)amine}iron(II) Chloride (6). A
2.14 g amount (0.00573 mol) of {1-[6-[1-((2-fluoro-6-methyl-
phenyl)imino)ethyl]pyridin-2-yl]ethylidene}(2,4-dimethylphenyl)-
amine (20) was dissolved in 40 mL of THF. A 0.69 g amount
(0.0054 mol) of iron(II) chloride was added to the reaction mixture
in one portion. The resultant blue precipitate was filtered after 12 h
X-ray Diffraction Studies. Data for all structures were col-
lected using a Bruker CCD system at -100 °C. Structure solution

1156 Organometallics, Vol. 27, No. 6, 2008
Ionkin et al.
and refinement were performed using the Shelxtl15 set of
programs. The Platon-Squeeze16 program was used to correct
the data where the solvent molecules could not be correctly
modeled. A summary of crystal data and data collection and
structural refinement parameters for 1, 4, 5, and 7 is given in
Table 3.
Acknowledgment. We wish to thank Kurt Adams for
funding X-ray research.
Supporting Information Available: CIF files for compounds
1, 4, 5, and 7. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM701204W
(15) Sheldrick, G. Shelxtl Software Suite, Version 5.1; Bruker AXS
Corp., Madison, WI.
(16) Spek, A. L. PLATON, A Multipurpose Crystallographic Tool;
Utrecht University, Utrecht, The Netherlands, 2005.