Iminopyridine complexes of 3d metals for ethylene polymerization: Comparative structural studies and ligand size controlled chain termination

Article abstract of DOI:10.1021/om060857q

A variety of iron complexes bearing tridentate pyridine based ligands are presented as highly active precatalysts for the oligomerization and polymerization of ethene and propene. The ligands comprise two classes: the first class, where both ketone groups of the 2,6-diacetylpyridine are converted to imines to give symmetrical or unsymmetrical bis(imino)pyridines (NNN ligands; 1-4, 8, and 9), and the second class, where only one keto function of the 2,6-diacetylpyridine is substituted by an imine to give monoiminoacetylpyridines (NNO or MIAP ligands; 5-7). The NNN ligands have been reacted with FeCl ₂·₄H₂O to afford the corresponding metal complexes (12-17). These complexes have been activated by modified methylaluminoxane (MMAO) and tested in the oligomerization and polymerization reaction of ethene and propene. Depending on the steric bulk of the ortho substituents at the aryl group of the imines, tunable polymerization products are observed, with molecular weights (M_w) of 10²-10 ⁶. Using the MIAP ligands, complexes of Co(II), Cr(II), Fe(II), Mn(II), and Ni(II) (18-24) have been prepared. The solid-state X-ray structures of the square-pyramidal {2-acetyl-6-[1-((2,6-diisopropylphenyl)imino)-ethyl] pyridine}metal halide complexes 18, 21, and 22b (M = Co(II), Fe(II), Ni(II)) have been compared. Additionally, the solid-state structure of {2,6-bis[1-(1-biphenylimino)ethyl]pyridine}iron(II) chloride (15) is presented. All ligands and complexes have been characterized by spectroscopic methods, mass spectra, and elemental analysis.

Full text of DOI:10.1021/om060857q

988
Organometallics 2007, 26, 988-999
Iminopyridine Complexes of 3d Metals for Ethylene
Polymerization: Comparative Structural Studies and Ligand Size
Controlled Chain Termination
Franz A. R. Kaul,† Gerd T. Puchta,‡ Guido D. Frey,§ Eberhardt Herdtweck, and
Wolfgang A. Herrmann*
Department Chemie, Lehrstuhl fu¨r Anorganische Chemie, Technische UniVersita¨t Mu¨nchen,
Lichtenbergstrasse 4, D-85747 Garching, Germany
ReceiVed September 19, 2006
A variety of iron complexes bearing tridentate pyridine based ligands are presented as highly active
precatalysts for the oligomerization and polymerization of ethene and propene. The ligands comprise
two classes: the first class, where both ketone groups of the 2,6-diacetylpyridine are converted to imines
to give symmetrical or unsymmetrical bis(imino)pyridines (NNN ligands; 1-4, 8, and 9), and the second
class, where only one keto function of the 2,6-diacetylpyridine is substituted by an imine to give
monoiminoacetylpyridines (NNO or MIAP ligands; 5-7). The NNN ligands have been reacted with
FeCl2‚4H2O to afford the corresponding metal complexes (12-17). These complexes have been activated
by modified methylaluminoxane (MMAO) and tested in the oligomerization and polymerization reaction
of ethene and propene. Depending on the steric bulk of the ortho substituents at the aryl group of the
imines, tunable polymerization products are observed, with molecular weights (Mw) of 102-106. Using
the MIAP ligands, complexes of Co(II), Cr(II), Fe(II), Mn(II), and Ni(II) (18-24) have been prepared.
The solid-state X-ray structures of the square-pyramidal {2-acetyl-6-[1-((2,6-diisopropylphenyl)imino)-
ethyl]pyridine}metal halide complexes 18, 21, and 22b (M ) Co(II), Fe(II), Ni(II)) have been compared.
Additionally, the solid-state structure of {2,6-bis[1-(1-biphenylimino)ethyl]pyridine}iron(II) chloride (15)
is presented. All ligands and complexes have been characterized by spectroscopic methods, mass spectra,
and elemental analysis.
(SHOP) was developed after screening new catalysts5 and
showed the potential of late-transition-metal catalysts for
polymerization.6 A revolutionary system was reported by
Brookhart and co-workers, in which nickel(II) and palladium-
(II) complexes containing bulky R-diimine ligands were capable
of polymerizing ethylene to give high-molecular-weight poly-
mers. These catalysts showed the important role of the synergy
between stereo and electronic effects of the ligands and the
catalytic activity of the metal center. Since the discovery in 1998
by Brookhart7,8 and Gibson9,10 that complexes of late transition
metals, such as iron and cobalt, with bulky 2,6-bis(imino)-
pyridine ligands11,12 (NNN ligands) and their derivatives13 were
highly catalytically active for polyolefination,14 the interest in
polymerization catalysts other than metallocenes has greatly
increased.15-27
Introduction
Over the past 60 years few research areas have had as
tremendous an impact on human civilization than tailor-made
polyolefins. Initially discovered in the 1950s by Ziegler and
Natta1,2 and driven by the desire to improve the properties of
polyolefinic materials, the design and the modification of useful
organometallic or coordinate catalysts have been in sharp focus
ever since. Introduced by traditional Ziegler-Natta catalysts
which had the early transition metal titanium as the catalytically
active center, much effort was involved using early transition
metals when searching for new types of catalysts, of which
metallocene and coordinate chromium-based catalysts have been
intensely studied.3 However, there was always great interest in
the application of late transition metals as catalysts for the
polyolefination of alkenes.4 The Shell Higher Olefins Process
* To whom correspondence should be addressed. E-mail: lit@
arthur.anorg.chemie.tu-muenchen.de.
† Present address: EPCOS AG, Anzingerstrasse 13, D-81617 Mu¨nchen,
Germany.
‡ Present address: Rehau AG & Co., Otto-Hahn-Strasse 2, 95111 Rehau,
Germany.
§ Present address: UCR-CNRS Joint Research Chemistry Laboratory
(UMI 2957), Department of Chemistry, University of California, Riverside,
CA 92521-0403.
(1) Ziegler, K.; Holzkamp, E.; Breil, H.; Martin, H. Angew. Chem. 1955,
67, 541.
Because of their lower oxophilicity,28 these “post-metallocene
catalysts” are well-suited for applications in the copolymeriza-
tion of R-olefins with polar monomers such as alkyl acry-
(2) Natta, G. Angew. Chem. 1956, 68, 393.
(3) (a) Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem. 1995, 107, 1255; Angew. Chem., Int. Ed.
Engl. 1995, 34, 1143. (b) White, P. A.; Calabrese, J.; Theopold, K. H.
Organometallics 1996, 15, 5473. (c) McKnight, A. L.; Waymouth, R. M.
Chem. ReV. 1998, 98, 2587.
(5) (a) Nieuwenhuis, R. A. Pet. Tech. 1980, 268, 46. (b) Spitzer, E. L.
T. M. Seifen, Oele, Fette, Wachse 1981, 107, 141.
(6) (a) Ittle, S. D.; Johnson, L. K.; Brookhart, M. Chem. ReV. 2000, 100,
1169. (b) Britovsek, G. J. P.; Gibson, V. C.; Wass D. F. Angew. Chem.
1999, 111, 448; Angew. Chem., Int. Ed. 1999, 38, 428.
(4) Hartley, F. R. Chem. ReV. 1969, 69, 799.
10.1021/om060857q CCC: $37.00 © 2007 American Chemical Society
Publication on Web 01/11/2007

Iminopyridine Complexes of 3d Metals
Organometallics, Vol. 26, No. 4, 2007 989
lates.28,29 Due to problems (e.g., reactor fouling and an extremely
exothermic polymerization process) arising from the homoge-
neous nature of the polymerization catalysts, the application of
these polymerization catalysts in gas-phase or slurry reactions
still is comparatively problematic.
(7) (a) Small, B. L.; Brookhart, M.; Bennet, A. M. A. J. Am. Chem.
Soc. 1998, 120, 4049. (b) Small, B. L.; Brookhart, M. Macromolecules
1999, 32, 2120.
(8) Small, B. L.; Brookhart, M. J. Am. Chem. Soc. 1998, 120, 7143.
(9) (a) 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. (b) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F.
Angew. Chem. 1999, 111, 448; Angew. Chem., Int. Ed. 1999, 38, 428.
(10) 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.
(11) (a) Steffen, W.; Blo¨mker, T.; Kleigrewe, N.; Kehr, G.; Fro¨hlich,
R.; Erker, G. Chem. Commun. 2004, 1188. (b) Lappalainen, K.; Yliheikkila,
K.; Abu-Surrah, A. S.; Polamo, M.; Leskela¨, M.; Repo, T. Z. Anorg. Allg.
Chem. 2005, 631, 763. (c) Britovsek, G. J. P.; England, J.; Spitzmesser, S.
K.; White, A. J. P.; Williams, D. J. Dalton Trans. 2005, 945. (d) Bouwkamp,
M. W.; Bart, S. C.; Hawrelak, E. J.; Trovitch, R. J.; Lobkovsky, E.; Chirik,
P. J. Chem. Commun. 2005, 3406. (e) Kleigrewe, N.; Steffen, W.; Blo¨mker,
T.; Kehr, G.; Fro¨hlich, R.; Wibbeling, B.; Erker, G.; Wasilke, J.-C.; Wu,
G.; Bazan, G. C. J. Am. Chem. Soc. 2005, 127, 13955. (f) Scott, J.;
Gambarotta, S.; Korobkov, I.; Knijnenburg, Q.; de Bruin, B.; Budzelaar,
P. H. M. J. Am. Chem. Soc. 2005, 127, 17204. (g) Champouret, Y. D. M.;
Marechal, J.-D.; Dadhiwala, I.; Fawcett, J.; Palmer, D.; Singh, K.; Solan,
G. A. Dalton Trans. 2006, 2350.
Figure 1. Synthesized iminopyridine compounds.
In this article, we report the synthesis of a series of bis(imino)-
pyridine 3d metal complexes and their catalytic behavior for a
chain-controlled ethylene and propylene polymerization accord-
ing to the ligand size and steric effects. Reaction parameters,
such as temperature and cocatalyst concentration, have also been
investigated for their effect on polymerization activity.
Results and Discussion
The symmetrical NNN compounds 1-4 were synthesized
from the reaction of 2,6-diacetylpyridine with the appropriate
amines, similar to the procedure by Alt et al. (see Figure 1).30
These compounds have already been described elsewhere (see
refs 7, 9, 15, 30-32 and references therein).
(12) Suhr, D.; Lo¨tscher, D.; Stoeckli-Evans, H.; von Zelewsky, A. Inorg.
Chim. Acta 2002, 341, 17.
(13) Britovsek, G. J. P.; Gibson, V. C.; Hoarau, O. D.; Spitzmesser, S.
K.; White, A. J. P.; Williams, D. J. Inorg. Chem. 2003, 42, 3454.
(14) 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.
(15) Benvenuti, F.; Francois, P. (Solvay Polyolefins Europe-Belgium)
US 6670434 B2; US 2003/0018147 A1; BE 1014196 A3, 2003.
(16) Ma, Z.; Sun, W.-H.; Li, Z.-L.; Shao, C.-X.; Hu, Y.-L.; Li, X.-H.
Polym. Int. 2002, 51, 994.
(17) Bianchini, C.; Giambastiani, G.; Guerrero, I. R.; Meli, A.; Passaglia,
E.; Gragnoli, T. Organometallics 2004, 23, 6087.
(18) Liu, J.-Y.; Zheng, Y.; Li, Y.-G.; Pan, L.; Li, Y.-S.; Hu, N.-H. J.
Organomet. Chem. 2005, 690, 1233.
The synthesis of monoiminoacetylpyridines (MIAP ligands)
was carried out according to a known method.30 In this case,
the aniline derivatives were used in only 0.98 equiv amount in
a protic solvent. Compound 5 could be recrystallized in 85%
yield from a methanol solution at room temperature. Much lower
temperatures (-30 °C) were necessary for compound 7. Only
compound 6 could not be obtained in high yields, because of
its excellent solubility in methanol during recrystallization; for
this reason, the compound was recrystallized from the less polar
solvent ethanol in 53% yield. Another problem occurs during
the preparation of compound 6, where a high amount of the
disubstituted byproduct 3 was obtained.
(19) Scott, J.; Gambarotta, S.; Korobkov, I.; Budzelaar, P. H. M. J. Am.
Chem. Soc. 2005, 127, 13019.
(20) (a) Souane, R.; Isel, F.; Peruch, F.; Lutz, P. J. C. R. Chim. 2002, 5,
43. (b) Chen, Y.-F.; Qian, C.-T.; Sun, J. Organometallics 2003, 22, 1231.
(c) Chen, Y.-F.; Chen, R.-F.; Qian, C.-T.; Dong, X.-C.; Sun, J. Organo-
metallics 2003, 22, 4312. (d) Castro, P. M.; Lappalainen, K.; Ahlgren, M.;
Leskela, M.; Repo, T. J. Polym. Sci., Part A: Polym. Chem. 2003, 41,
1380. (e) 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. (f) Paulino, I. S.; Schuchardt, U. J. Mol. Catal. A: Chem. 2004, 211,
55. (g) Zhang, Z.-C.; Chen, S.-T.; Zhang, X.-F.; Li, H.; Ke, Y.; Lu, Y.-Y.;
Hu, Y.-L. J. Mol. Catal. A: Chem. 2005, 230, 1. (h) Pelascini, F.; Peruch,
F.; Lutz, P. J.; Wesolek, M.; Kress, J. Eur. Polym. J. 2005, 41, 1288. (i)
Calderazzo, F.; Englert, U.; Pampaloni, G.; Santi, R.; Sommazzi, A.; Zinna,
M. Dalton Trans. 2005, 914. (j) Yliheikkila, K.; Lappalainen, K.; Castro,
P. M.; Ibrahim, K.; Abu-Surrah, A.; Leskela¨, M.; Repo, T. Eur. Polym. J.
2006, 42, 92. (k) Ionkin, A. S.; Marshall, W. J.; Adelman, D. J.; Bobik-
Fones, B.; Fish, B. M.; Schiffhauer, M. F. Organometallics 2006, 25, 2978.
(l) Ionkin, A. S.; Marshall, W. J.; Adelman, D. J.; Shoe, A. L.; Spence, R.
E.; Xie, T. J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 2615. (m) Archer,
A. M.; Bouwkamp, M. W.; Cortez, M.-P.; Lobkovsky, E.; Chirik, P. J.
Organometallics 2006, 25, 4269.
For the synthesis of unsymmetrical 2,6-bis(imino)pyridine
compounds the compound 5 was used as the starting material.
It is recommended to use an excess of the precursor 5, if it is
not possible to remove the aniline compound from the reaction
mixture, as is the case for compound 8. The excess of
2-isopropylaniline used for the preparation of compound 9 can
be removed very easily by distillation.16
Syntheses of an Alkene-Functionalized Compound (10).
With the 2,6-bis{1-[2,6-(diisopropylphenyl)imino]ethyl}pyridine
compound 1 reported by Brookhart and Gibson as the starting
(26) Esteruelas, M. A.; Lopez, A. M.; Mendez, L.; Olivan, M.; Onate,
E. Organometallics 2003, 22, 395.
(27) (a) Babik, S. T.; Fink, G. J. Mol. Catal. A: Chem. 2002, 188, 245.
(b) Bryliakov, K. P.; Semikolenova, N. V.; Zakharov, V. A.; Talsi, E. P.
Organometallics 2004, 23, 5375. (c) Humphries, M. J.; Tellmann, K. P.;
Gibson, V. C.; White, A. J. P.; Williams, D. J. Organometallics 2005, 24,
2039.
(21) (a) Gibson, V. C.; McTavish, S.; Redshaw, C.; Solan, G. A.; White,
A. J. P.; Williams, D. J. Dalton Trans. 2003, 221. (b) Gibson, V. C.; Long,
N. J.; Oxford, P. J.; White, A. J. P.; Williams, D. J. Organometallics 2006,
25, 1932.
(28) Johnson, L. K.; Mecking, S.; Brookhart, M. J. Am. Chem. Soc. 1996,
118, 267.
(22) (a) Liu, J.-Y.; Li, Y.-S.; Liu, J.-Y.; Li, Z.-H. Macromolecules 2005,
38, 2559. (b) Overett, M. J.; Meijboom, R.; Moss, J. R. Dalton Trans. 2005,
551.
(23) Abu-Surrah, A. S.; Lappalainen, K.; Piironen, U.; Lehmus, P.; Repo,
T.; Leskela¨, M. J. Organomet. Chem. 2002, 648, 55.
(24) O’Reilly, R. K.; Gibson, V. C.; White, A. J. P.; Williams, D. J.
Polyhedron 2004, 23, 2921.
(25) (a) Qiu, J.-M.; Li, Y.-F.; Hu, Y.-L. Polym. Int. 2000, 49, 5. (b) Ma,
Z.; Wang, H.; Qiu, J.-M.; Xu, D.; Hu, Y.-L. Macromol. Rapid Commun.
2001, 22, 1280.
(29) Younkin, T. R.; Connor, E. F.; Henderson, J. I.; Friedrich, S. K.;
Grubbs, R. H.; Bansleben, D. A. Science 2000, 287, 460.
(30) (a) Schmidt, R.; Welch, M. B.; Palackal, S. J.; Alt, H. G. J. Mol.
Catal. A: Chem. 2002, 179, 155. (b) Schmidt, R.; Welch, M. B.; Knudsen,
R. D.; Gottfried, S.; Alt, H. G. J. Mol. Catal. A: Chem. 2004, 222, 9.
(31) Bennett, A. M. A. (E.I. DuPont De Nemours and Conpany) WO
98/27124, 1998; U.S. Patent 6063881, 2000; Eur. Patent EP 0946609 B1,
2002; Eur. Patent EP 1066229 B1, 2004.
(32) Hiya, K.; Nakayama, Y.; Yasuda, H. Macromolecules 2003, 36,
7916.

990 Organometallics, Vol. 26, No. 4, 2007
Kaul et al.
Scheme 1. Preparation of Unsymmetrical
Bis(imino)pyridine Compounds
Scheme 3. Preparation of Bis(imino)pyridine-Substituted
Iron(II) Complexes 12-17
Scheme 2. Preparation of the Styrene-Substituted Complex
11
The unsymmetrical [bis(imino)pyridine]iron(II) complexes 16
and 17 can be perceived as hybrids of complexes 12-14
(Scheme 3). They were characterized, as were all other
previously mentioned complexes, by MS, IR, and elemental
analysis. We were not able to obtain crystals suitable for X-ray
analysis from the complexes 16 and 17. An explanation for the
reluctance of complex 16 to crystallize could be its high
solubility in many solvents, the unsymmetrical character of the
complex, and probably the high rotation liberty of the isopropyl
groups.
The styrene-substituted complex 11 was obtained from a THF/
n-pentane solution in 66% yield, in the same way as for all
other [bis(imino)pyridine]iron complexes (Scheme 2). This
complex has the potential to be immobilized via the ligand’s
styrene moiety onto a polystyrene carrier.33
A series of [mono(imino)pyridine]metal(II) dihalide com-
plexes, bearing hydrocarbon ligands (5-7), were prepared by
using hydrated or dehydrated transition-metal salts such as
FeCl2‚4H2O and CoCl2 in DCM (Scheme 4).34 Using transition-
metal complexes with a coordinated solvent such as (DME)-
NiBr2 increases the solubility in organic solvents and is of
advantage during the synthesis.35 The strong colors of the iron
complex 18 (purple) and the cobalt complex 21 (green) can be
explained by ligand field theory effects, such as those shown
recently for [bis(imino)pyridine]metal complexes.19,36 In con-
trast, complexes 20 and 22-24 are brown or ocher.
The complexes 18-24 were characterized by their elemental
analysis, mass spectra, and infrared spectra. A comparison of
the IR data for the CdO and CdN stretching frequencies shows
a significant shift during the change from early to late transition
metals in their oxidation state +II (Table 1). The strong shift
to smaller wavenumbers of the Cr(II) complex 19 is striking.
This can be explained by the highly oxophilic character of
chromium, as a consequence of the increased Lewis acidity:
in the HSAB concept, chromium(II) is a harder Lewis acid than
the following periodic neighbors.37 The CdO double-bond
character is increased by the donor effect of the free electron
pairs of the oxygen to the metal; consequently, a lower
material,7,9 the functionalization was achieved by deprotonation
of the bis(imino)pyridine compound with lithium diisopropyl-
amide. The yellow solution of compound 1 immediately turned
dark green, almost black. After the mixture was kept under
reflux for 12 h, 4-vinylbenzyl chloride was added and the
mixture stirred for 5 days, affording 10 (Scheme 1). The reaction
was finished when the solution turned red.
Complex Synthesis. [Bis(imino)pyridine]iron(II) complexes
were synthesized according to published methods7,9 by addition
of FeCl2‚4H2O to a stirred solution of the compounds 1-4 and
8-10 in n-BuOH or THF.26 The resulting deep blue iron
complexes 11, 12,7,9 and 13-17 are depicted in Schemes 2 and
3. Blue crystals of complex 15 suitable for a single-crystal X-ray
diffraction study were obtained by slow diffusion of diethyl ether
into a saturated dichloromethane solution. The solid-state
structure of the iron complex 15 is shown in Figure 2. Details
of the data collection and refinement of the analysis are
summarized in Table 3, and selected bond lengths and angles
are presented in Table 2.
In comparison to the previously reported complex 12 by
Gibson et al., where the 2,6-diisopropylphenyl groups are
substituted at the bis(imino)pyridine complex (Fe-N )
2.238(4) and 2.250(4) Å),9,14 complex 15 shows shorter
Fe-N(2) and Fe-N(3) bond lengths (Fe-N ) 2.195(1) and
2.182(1) Å). This is attributed to the decreased steric bulk of
the substituents ortho to the imino groups. The slightly wider
N(2)-Fe-N(3) angle (by 4°) is caused from the longer Fe-N
bond length obtained in this complex. A square-pyramidal
geometry was also found for complex 15 as well as for the
2,6-diisopropylphenyl-substituted complex 12.
(33) (a) Zheng, Z.-J.; Chen, J.; Li, Y.-S. J. Organomet. Chem. 2004,
689, 3040. (b) Zheng, Z.-J.; Liu, J.-Y.; Li, Y.-S. J. Catal. 2005, 234, 101.
(c) Han, W.; Mu¨ller, C.; Vogt, D.; Niemantsverdriet, H. J. W.; Thu¨ne, P.
C. Macromol. Rapid Commun. 2006, 27, 279.
(34) For example: Fernandes, S.; Bellabarba, R. M.; Ribeiro, A. F. G.;
Gomes, P. T.; Ascenso, J. R.; Mano, J. F.; Dias, A. R.; Marques, M. M.
Polym. Int. 2002, 51, 1301.
(35) Bluhm, M. E.; Folli, C.; Do¨ring, M. J. Mol. Catal. A: Chem. 2004,
212, 13.
(36) Small, B. L.; Carney, M. J.; Holman, D. M.; O’Rourke, C. E.;
Halfen, J. A. Macromolecules 2004, 37, 4375.
(37) Muelhaupt, R. Nachr. Chem. Tech. Lab. 1993, 41, 1341.

Iminopyridine Complexes of 3d Metals
Organometallics, Vol. 26, No. 4, 2007 991
Figure 2. ORTEP style plot of complex 15 in the solid state. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms
are omitted for clarity. Selected bond lengths (Å) and bond angles (deg) are given in Table 2.
Scheme 4. Preparation of [Mono(imino)pyridine]metal(II) Complexes
Table 1. Comparison of the ν(CO) and ν(CN) Absorption Frequencies (cm-1) of Different 3d Metal Complexes
5
19 (Cr(II)) 20 (Mn(II)) 18 (Fe(II)) 21 (Co(II)) 22a (NiCl2) 22b (NiBr2)
6
24 (NiBr2)
7
23 (NiBr2)
CdO 1698.6
CdN 1647.9
1633.9
1577.9
1676.6
1588.6
1689.4
1588.4
1675.9
1588.6
1668.2
1588.6
1673.3
1591.9
1695.6
1647.6
1666.5
1586.7
1697.5
1586.7
1667.6
1590.3
wavenumber (1633.9 cm-1) is obtained (Table 1). For the CdN
stretching frequency this effect is much more intense, because
the free electron pair of the nitrogen is a much stronger donor
(harder base) than oxygen. For this reason, a shift of nearly 70
cm-1 occurs compared to the free compound. For the follow-
ing periodic neighbors, a shift for the CdN stretching fre-
quency of around 60 cm-1 was obtained. The variation of the
CdO stretching frequency might also be influenced by some
geometric effects. Because of the restricted geometric arrange-
ment of the three donor atoms of the chelating ligand, the bond
strength of each donor atom and the geometry of the complex
will differ with increasing metal size. In the row from
manganese to nickel only a small variation in the CdN
wavelength (∼1588 cm-1) was detected. Only complex 22b

992 Organometallics, Vol. 26, No. 4, 2007
Kaul et al.
Figure 3. ORTEP style plot of complex 18 in the solid state. Thermal ellipsoids are drawn at the 50% probability level. Hydrogen atoms
are omitted for clarity. Selected bond lengths (Å) and bond angles (deg) are given in Table 2.
Table 2. Selected Bond Distances (Å) and Angles (deg) for
tion. Details of the data collection and refinement of the analysis
are summarized in Table 3.
Complexes 15, 18‚CH2Cl2, 21‚CH2Cl2, and 22b
15
(M ) Fe,
X ) Cl)
18‚CH2Cl2
(M ) Fe,
X ) Cl)
21‚CH2Cl2
(M ) Co,
X ) Cl)
22b
(M ) Ni,
X ) Br)
The square-pyramidal structure of 18 is reminiscent of certain
five-coordinate iron(II) and cobalt(II) NNN derivatives reported
by several research groups.10,12,21,24 For complex 18 the basal
plane consists of the two nitrogens and the oxygen atoms from
the ligand and one equatorial chloride, with the remaining
chloride (C11) occupying the apical position. In this geometry,
the iron atom is raised 0.64 Å above the basal plane. In a
comparison of complex 18 with 21, a significant decrease in
the metal-nitrogen bond length and also a significant decrease
in the metal-chloro bond length were obtained. In contrast,
the metal-oxygen bond length is increased from 2.243(6) Å
(18) to 2.327(1) Å (21) (Table 2). The C(2)-O bond length is
in both complexes equal within the esd’s, in contrast to the
C(8)-N(2) bond length (1.307(9) Å for 18; 1.283(2) Å for 21).
In comparison to the case for the [bis(imino)pyridine]iron(II)
complexes 12 and 15, the two metal-chloro bond distances in
complexes 18 and 21 vary only slightly (2.285(2) and 2.274(2)
Å for 18; 2.2505(5) and 2.2381(5) Å for 21), in contrast to
2.266(2) and 2.311(2) Å for 127a and 2.2732(5) and 2.3224(6)
Å for 15. Complex 22b has, as does complex 15, a regular
square-pyramidal structure.38
M-N1
M-N2
M-N3
M-O
2.097(1)
2.195(1)
2.182(1)
2.102(5)
2.191(6)
2.042(1)
2.161(1)
1.981(2)
2.087(2)
2.243(6)
2.285(2)
2.274(2)
1.307(9)
1.224(10)
2.327(1)
2.2505(5)
2.2381(5)
1.283(2)
1.221(2)
2.334(2)
2.4009(4)
2.3403(4)
1.278(3)
1.213(4)
M-X1
M-X2
C6/C8-N2
C2-O
2.3224(6)
2.2732(5)
1.287(2)
C8-N3
1.290(2)
X1-M-X2
N1-M-N2
N1-M-O
N1-M-N3
N2-M-O
N2-M-N3
N1-M-X1
N2-M-X1
N1-M-X2
N2-M-X2
O-M-X1
N3-M-X1
O-M-X2
N3-M-X2
116.68(2)
73.29(5)
107.95(8)
73.8(2)
71.7(2)
111.31(2)
77.06(5)
72.63(5)
117.76(2)
78.69(8)
73.45(8)
73.21(5)
145.1(2)
149.29(5)
148.56(8)
144.06(5)
99.38(4)
100.28(4)
143.94(4)
99.29(4)
119.5(2)
106.5(2)
131.1(2)
105.0(2)
94.8(2)
117.58(4)
107.13(4)
128.30(4)
104.21(3)
91.37(3)
94.47(6)
104.42(6)
146.12(6)
101.33(6)
92.15(5)
97.63(4)
93.9(2)
90.95(3)
93.95(5)
Polymerization. It is now well established that [bis(imino)-
pyridine]iron(II) complexes can be activated by MAO and
MMAO for the polymerization of ethene.7-10 In the following
discussion, a variety of different reaction temperatures and
different cocatalyst/catalyst ratios are investigated for five bis-
(imino)pyridine catalysts.
After activation with MMAO, complex 15 showed only very
little activity in the polymerization of ethene or propene. At a
temperature of 0 °C, insufficient activities of around 1400 kg
of PE ((mol of Fe) h bar)-1 were obtained for polymerization
of ethene; when the temperature was increased to 40 °C,
no polymerization was noted. Polymerization or oligomeri-
zation of propene was not successful with this catalyst
100.07(4)
shows, at 1591 cm-1, a slightly increased wavenumber, in accord
with a higher number of electrons for the bromo substituent
(lower electronegativity of bromine) and, for this reason, a lower
Lewis acidity of the nickel(II) system. For the nickel complexes
23 and 24 the same results were obtained in the IR spectra.
Slow cooling of saturated dichloromethane (DCM) solutions
of 18 and 21 deposited single crystals of purple and green
crystals, respectively, which were suitable for X-ray diffraction.
Red X-ray-quality crystals of complex 22b were obtained by
slow diffusion of n-pentane into a saturated DCM solution.
Figure 3 illustrates the molecular structure of 18, and Table 2
summarizes the selected bond distances and angles of complexes
18, 21, and 22b. The structures of 21 and 22b are similar to
the structure of 18 and are depicted in the Supporting Informa-
(38) Addison, A. W.; Rao, T. N.; Reedijk, J.; van Rijn, J.; Verschorr, G.
C. J. Chem. Soc., Dalton Trans. 1984, 1349.

Iminopyridine Complexes of 3d Metals
Organometallics, Vol. 26, No. 4, 2007 993
Table 3. Crystallographic Data for Complexes 15, 18‚CH2Cl2, 21‚CH2Cl2, and 22b
15
18‚CH2Cl2
21‚CH2Cl2
22b
formula
fw
C33H27Cl2FeN3
592.33
C22H28Cl4FeN2O
534.11
C22H28Cl4CoN2O
537.19
C21H26Br2N2NiO
540.93
color/habit
blue/plate
0.04 × 0.18 × 0.41
monoclinic
P21/n (No. 14)
12.6461(3)
16.1220(2)
15.8418(3)
104.136(1)
3132.0(1)
4
purple/needle
0.03 × 0.08 × 0.64
monoclinic
P21/c (No. 14)
8.9356(8)
15.1674(11)
19.541(2)
101.885(11)
2591.6(4)
4
green/needle
0.20 × 0.20 × 1.01
monoclinic
P21/c (No. 14)
8.8222(1)
15.2586(2)
19.5824(2)
101.004(1)
2587.61(5)
4
red/fragment
0.10 × 0.13 × 0.51
monoclinic
Cc (No. 9)
10.4153(2)
16.0983(4)
13.4869(2)
92.393(1)
2259.36(8)
4
cryst dimens (mm3)
cryst syst
space group
a, Å
b, Å
c, Å
â, deg
V, Å3
Z
T, K
143
1.256
0.677
1224
173
1.369
1.010
1104
153
1.379
1.092
1108
153
1.590
4.408
1088
D
calcd, g cm-3
µ, mm-1
F(000)
θ range, deg
1.83-26.20
(15, (20, (19
12 033
6247/0.020
5303
6247/0/460
0.0320/0.0712
0.0401/0.0738
1.027
2.81-25.60
-7 to +8, -17 to +14, (23
4300
2234/0.103
1450
2234/0 /271
0.0528/0.1295
0.0870/0.1551
0.953
1.70-25.36
(10, (18, (23
9292
4744/0.010
4450
4744/0 /383
0.0246/0.0591
0.0268/0.0601
1.042
2.33-25.38
(12, (19, (16
8080
4148/0.027
4028
4148/2 /348
0.0191/0.0434
0.0202/0.0439
1.042
index ranges (h, k, l)
no. of rflns collected
no. of indep rflns/Rint
no. of obsd rflns (I > 2σ(I))
no. of data/restraints/params
R1/wR2 (I > 2σ(I))a
R1/wR2 (all data)a
GOF (on F2)a
largest diff peak/hole (e Å-3
)
+0.28/-0.41
+0.35/-0.45
+0.65/-0.48
+0.29/-0.23
2
2
2
2
2
a R1 ) ∑(||Fo| - |Fc||)/∑|Fo|; wR2 ) {∑[w(Fo - Fc )2]/∑[w(Fo )2]}1/2; GOF ) {∑[w(Fo - Fc )2]/(n - p)}1/2
.
Table 4. Ethene and Propene Polymerization Activity of the
Symmetrical [Bis(imino)pyridine]iron(II) Complex 13 after
Activation with MMAOa
activityb
after
after
c
c
c
monomer T (°C) 5 min 45 min
av
Mw
Mn
Mw/Mn
ethene
0
20
40
60
80
0
20
40
60
80
79.8
99.7
93.2
31.8
15.4
29.7
3.57
21.2
40.9
18.1
1170 390
1130 370
930 300
790 240
670 200
550 270
400 200
330 160
3.00
3.05
3.10
3.29
3.35
2.04
2.00
2.06
-
1.54
7.04
8.52
2.12
1.11
0.82
0.38
-
-
Figure 4. Possible conformations of complex 13.
propene
3.15
2.02
1.12
-
-
0.42
0.22
0.20
-
-
be 3, resulting from higher R-olefins being formed simulta-
neously with short-chain R-olefins. The two different groups
of R-olefins presumably result from the large steric bulk of the
N-aryl groups.
At higher temperatures the average activity for polymerization
decreased and lower molecular weights of the products were
observed, along with a concomitant decrease in selectivity and
higher polydispersity.
-
-
-
-
-
a Reaction conditions: 2 bar of alkene pressure, toluene as solvent,
cocatalyst MMAO (Al:Fe ) 1000); reaction time 1 h. b In units of 103 kg
of PE/PP ((mol of Fe) h bar)-1 c Determined by GPC.
.
under any conditions. It is tempting to attribute the low activity
of complex 15 to the distorted catalyst geometry introduced by
the sterically bulky biphenyl groups.
Complex 13 can be found in two different conformations
(with a Cs or a C2V symmetry) (Figure 4). We propose for the
poly- and oligomerization of propene a mechanism analogous
to the polymerization of propene with activated ansa-metal-
locene complexes; thus, the two different conformers should
yield a variety of poly- and oligopropylenes. In accordance with
the well-known, related ansa-metallocene complexes, a conver-
sion of the active center should occur during the chain-growing
process, and the Cs-symmetric cisoid form should give pre-
dominantly atactic poly- or oligopropylene such as the sym-
metric meso form of ansa-bis(indenyl)metallocene derivatives.39
According to this, the C2V-symmetric transoid form should give
isotactic poly- or oligopropylene, corresponding to the rac form
of ansa-bis(indenyl)metallocene derivatives. Because of the
hindered rotation flexibility of the N-aryl ring around the
N-Caryl bond, it should be possible at low temperatures to form
either atactic or isotactic polymers.
In contrast, complex 13 shows, after activation with
MMAO, high activities of 104 kg of PE ((mol of Fe) h bar)-1
for the polymerization of ethene, but the activity for the
oligomerization of propene is much lower (see Table 4). We
also found a temperature dependency for the polymerization of
ethene. In contrast to the case for all other catalysts, the highest
activity was obtained not at 0 °C but at 20 °C. The catalyst
lifetime under the chosen reaction conditions has a large
influence on the average polymerization activity. For this reason,
at high reaction temperatures high starting activities and high
maximum activities were observed; however, the average
activities decreased rapidly at high temperatures. At 80 °C
complete deactivation of the catalyst occurred after a short time
(20 min). For all reactions no polymer was obtained, only
oligomers with an average molecular weight of Mw ) 700-
1100. According to analytical GC-MS, short R-olefins such as
1-hexene and 1-octene were also obtained (Table 4). The
polydispersity (Mw/Mn) for the formed oligomers was found to
(39) Wang, B. Coord. Chem. ReV. 2006, 250, 242 and references therein.

994 Organometallics, Vol. 26, No. 4, 2007
Kaul et al.
Figure 6. Ethene polymerization activity after activation of catalyst
17 with MMAO, dependent on the reaction temperature and
cocatalyst/catalyst ratio.
Figure 5. Ethene polymerization activity after activation of catalyst
14 with MMAO, dependent on the reaction temperature and
cocatalyst/catalyst ratio.
We found with catalyst 14 a bimodal molecular weight
distribution for all polymerization experiments. The polydis-
persity of the high-molecular-weight product decreases by
changing the reaction temperature from 0 to 40 °C but increases
if the temperature is changed to 60 or 80 °C. In contrast, such
a tendency was not observed for the low-molecular-weight
fraction; when the temperature was increased, a decrease in
polydispersity was obtained (Supporting Information).
The polymerization properties and polymers of symmetric
[bis(imino)pyridine]iron(II) chlorides have been well character-
ized in the literature;7a,9,40 in this work catalyst 14 shows high-
molecular-weight products and varying quantities of oligomers
in the product spectra, whereas complex 12 forms nearly
exclusively high-molecular-weight polymers.7,10,30 For this
reason it is of interest to use complex 17, which could be thought
of as a hybrid of complexes 12 and 14, in polymerization
reactions.
Similarly to the symmetric [bis(imino)pyridine]iron(II) com-
plexes (12, 14) an increase of the cocatalyst/catalyst ratio had
only an insignificant effect on the polymerization activity of
17; only for very high Al/Fe ratios (>5000) was there an
increase in activity at low temperatures (10 °C). This catalyst
also shows a high-temperature dependence for the polymeri-
zation activity; the best results were obtained at 0 °C (ap-
proximately 1 × 105 kg of PE ((mol of Fe) h bar)-1). The
activity maximum at this lower temperature is in agreement with
the increase in steric bulk for the increasing number of isopropyl
groups, in comparison with complex 14. We were able to show
for the hybrid complex 17 that an optimum temperature (0 °C)
for catalysis should be chosen, which is between the optimal
temperatures for complexes 12 (below 0 °C) and 14 (20 °C). If
the temperature is increased to 20 °C, only 20% of the maximum
activity at 0 °C was obtained. A further increase in temperature
(up to 80 °C) gives only activities of around 5 × 103 kg of PE
((mol of Fe) h bar)-1. For complex 17, as for all previously
discussed complexes (12-14), a very fast deactivation was
recognized at high temperatures (Figure 6).
During this work we were unable to obtain high isotactic
oligomers with catalyst 13. Only an enrichment of isotactic
oligomer products was obtained, which can be explained by
steric induction of the catalyst geometry, while no separation
of the two catalyst modifications was successful during prepara-
tion (Figure 4). The formation of the transoid form should be
favored during the preparation; for this reason an enrichment
of isotactic oligomers was expected.
Also for complex 14 two conformers are possible, analogous
to complex 13. In spite of the Cs and C2V symmetries of the
catalyst, we were unable to obtain isotactic oligopropylene under
any conditions. The {2,6-bis[((2-isopropylphenyl)imino)ethyl]-
pyridine}iron complex 14 provides, with regard to propene
polymerization, only a low polymerization activity of ap-
proximately 200 kg of PP ((mol of Fe) h bar)-1, yielding atactic
oligomers with a molecular weight of 300 and a polydispersity
of 2.2.
In contrast, for ethene polymerization much higher activities
were obtained, up to 73 × 103 kg of PE ((mol of Fe) h bar)-1
,
but still polymers of lower molecular weight compared to those
for complex 12 were obtained. This can be explained by the
decreased steric hindrance imparted by the chelating ligand,
where one ortho substituent at the N-aryl ring is missing
compared to 12. These aryl rings are less fixed orthogonal to
the Fe-N3 plane, and it follows that less blockage at the axial
position of the catalyst increases the rate of the chain-transfer
reaction and the formation of low-molecular-weight products.
Catalyst 14 seems relatively insensitive toward changes in
cocatalyst/catalyst ratio, as shown in Figure 5. In contrast, the
polymerization activity is highly temperature dependent. The
starting activity for catalyst 14 is relatively static at different
temperatures up to 60 °C (see the Supporting Information), but
the catalyst is deactivated more quickly with increasing tem-
peratures. For this reason the average activity is calculated for
all catalytic experiments after a reaction time of 60 min (Figure
5). The best results were obtained at a temperature of 20 °C.
An increase or decrease of the reaction temperature resulted in
severe suppression of catalytic activities. For example, an
increase to 40 °C depressed the average activity to 60% of that
obtained at 20 °C; further increases to 60 and 80 °C decreased
the activity to 30% and 15%, respectively. The main reason
for the rapid decrease in activity at high temperatures is the
fast deactivation of the catalyst. At low temperatures (0 and 20
°C) the catalyst is still active after hours, while the catalytic
activity at 60 °C stops after 40 min and that at 80 °C already
after 30 min.
At low temperatures the produced polymers show only a small
bimodality in the molecular weight distribution. Increasing the
temperature to 20 °C results in a monomodal molecular weight
distribution with polydispersities of up to 10. An increase in
yield for the high-molecular-weight fraction was detected by
the introduction of a third isopropyl group, such as for the
unsymmetrical catalyst 17. This introduction at the ortho position
of the N-aryl ring results in a constant ethene polymerization
(40) (a) Britovsek, G. J. P.; Dorer, B. A.; Gibson, V.; Kimberley, B. S.;
Solan, G. A. WO 9912981, 1997. (b) Small, B. L.; Brookhart, M. Polym.
Prepr. (Am. Chem. Soc., DiV. Polym. Chem.) 1998, 39, 213.

Iminopyridine Complexes of 3d Metals
Organometallics, Vol. 26, No. 4, 2007 995
Figure 8. Ethene polymerization activity after activation of catalyst
16 with MMAO, dependent on the reaction temperature and
cocatalyst/catalyst ratio.
Figure 7. Molecular weight of the produced polymers obtained
from ethene polymerization using catalyst 17, dependent on the
polymerization temperature and cocatalyst/catalyst ratio.
activity. Because of the additional sterically bulky groups above
or below the Fe-N3 plane, the shielding of the axial positions
at the N-aryl rings is optimized by an orthogonal fixation to
the Fe-N3 plane, yielding polymers with a high molecular
weight of approximately 6 × 105 and small quantities of a low-
molecular-weight fraction, with weights between 1 × 103 and
3 × 104; low-molecular-weight oligomers were not detected.
The molecular weight for the high-molecular-weight polymers
is still lower than those for the polymers obtained with catalyst
12, where the axial positions are shielded by four isopropyl
groups.
Changing the cocatalyst/catalyst ratio results only in small
changes in the distribution; for an Al/Fe ratio of 1000, 4% of
high-molecular-weight products was obtained, whereas at an
Al/Fe ratio of 200 only 8% of high-molecular-weight products
was recognized. As for the complexes above, the polymer
distribution for catalyst 17 is highly sensitive toward changes
in polymerization temperature. For this reason the highest
molecular weights for polymers were obtained at 20 °C with
an Al/Fe ratio of 10 000 (Figure 7).
Figure 9. Molecular weight of the produced polymers obtained
from ethene polymerization using catalyst 16, dependent on the
polymerization temperature and cocatalyst/catalyst ratio.
The tendency to obtain high molecular weights with a high
Al/Fe ratio is inverted at high temperatures. According to this
behavior, it is necessary to use small Al/Fe ratios when using
conditions above 40 °C. In this case no dependence of the
molecular weight on the Al/Fe ratio could be determined (Figure
7).
The results of these experiments support the notion that
complex 17 acts as a hybrid of the two symmetric complexes
12 and 14. The polymerization activities are nearly the same
for all of these catalysts; the catalytic properties of complex 17
lie between the data observed for the two symmetric complexes
(12, 14), as expected. With complex 17 we were unable to obtain
molecular weights as high as those for complex 12, but they
are much higher than these obtained from catalyst 14, which
produces mainly low-molecular-weight products.
A comparison of the two symmetric catalysts 13 and 14 show
that with the {2,6-bis[((isopropylphenyl)imino)ethyl]pyridine}-
iron(II) complex 14 huge quantities of oligomers were obtained
and also varying quantities of high-molecular-weight polymers.
With catalyst 13 only oligomers were produced and never
polymers. This is presumably because the 2,6-bis[(1-anthrace-
nylimino)ethyl]pyridine ligand (2) has no bulky groups in the
ortho position of the N-aryl rings, where an orthogonal
orientation of the N-aryl rings to the Fe-N3 plane is not
restricted. Because of the lesser degree of hindrance at the axial
position the chain transformation reaction is more favored, which
results in low-molecular-weight polymers or oligomers.
At this point, our interests now lay in the level of activity
and the type of polymers that are obtained by using two
isopropyl groups in positions ortho to an N-aryl ring and
introducing on the other side one anthracenyl substituent; thus,
we prepared complex 16.
The polymerization activity of the unsymmetrical catalyst 16
was found to be equivalent to the symmetric catalysts 13 and
14, but its activity maximum lay not at 0 or 20 °C but at a
temperature of 40 °C, with activities of up to 8 × 104 kg of PE
((mol of Fe) h bar)-1. When the temperature was either
decreased or increased, a decrease in activity was obtained
(Figure 8). The dependence of activity upon the cocatalyst/
catalyst ratio is similar to that of the above catalysts and only
plays a minor role in our experiments. The molecular weights
of the formed products were slightly higher for catalyst 16 than
for the symmetric catalyst 13.
Analogous to the case for complex 13, we could under no
conditions obtain high-molecular-weight polymers with catalyst
16; only oligomers with a molecular weight of 300-600 were
produced. A slight cocatalyst/catalyst dependency was recog-
nized for the produced polymers, as was true for all [bis-
(iminoethyl)pyridine]iron(II) complexes (12-14). The temper-
ature dependence of the produced polymers is much less
significant than for all previously discussed complexes (Figure
9). The highest molecular weights are obtained at the lowest
temperature (0 °C). All experiments showed a polydispersity
of approximately 3.

996 Organometallics, Vol. 26, No. 4, 2007
Kaul et al.
Table 5. Comparison of the Polymerization Activities and
the Molecular Weight of the Produced Polymers Using
Complexes 12-14, 16, and 17
no stabilization of the orthogonal FeN3 plane is favored, and
low-molecular-weight oligomers occur by chain transfer reaction
(Table 5).
mol wt
av polymerization
complex
activitya
main product
minor product
103-104
Experimental Section
12
17
14
103-105
103-105
103-105
105
104
105-106
General Considerations. All experiments were carried out under
an atmosphere of dry, purified nitrogen or argon using glovebox
or standard Schlenk techniques. All solvents were dried and
deoxygenated and kept under argon and molecular sieves (4 Å).
NMR spectra were recorded on JEOL JNM GX-400 and Bruker
DPX-400 instruments. The solvent signals were used for internal
calibration. All spectra were obtained at room temperature unless
otherwise stated. The infrared spectra of the homogeneous com-
pounds were recorded on a Perkin-Elmer FT-IR 1650 instrument
as KBr pellets. The supported precatalyst samples were prepared
under an inert atmosphere as self-supporting pellets and analyzed
using NaCl windows. Elemental analyses were carried out by the
Microanalytical Laboratory at the TU Mu¨nchen. Mass spectra were
performed at the TU Mu¨nchen Mass Spectrometry Laboratory on
a Finnigan MAT 90 spectrometer using the CI or FAB technique.
Melting points were measured with a Bu¨chi melting point apparatus
system (Dr. Tottoli). Polymer samples were dissolved in a mixture
of d3-1,2,4-trichlorobenzene and C2D2Cl4 and analyzed via NMR
spectroscopy at a temperature of 120 °C. The obtained polymers
were analyzed using a combination of a Waters 150 CV high-
temperature GPC at 135 °C with 1,2,4-trichlorobenzene as solvent
and a modified Whyatt Minidawn light-scattering instrument. The
calibration was performed with polystyrene standards and conver-
sion into PE and PP calibration curves using Mark-Houwink para-
meters. Modified methylaluminoxane (Witco, 10% in n-heptane)
was used as cocatalyst. Ethene (AGA Gas GmbH, grade 3.5) and
propene (Linde AG, grade 2.8) were purified by passing them
through two purification columns containing activated BTS catalyst
and molecular sieves (4 Å) before feeding the reactor. The reactor
pressure (2 bar ( 0.02) was maintained constant throughout the
polymerization run by a press flow gas controller (Bu¨chi bpc 1202).
2,6-Bis{1-[(2,6-diisopropylphenyl)imino]ethyl}pyridine (1),10,41 2,6-
bis[1-(anthracenylimino)ethyl]pyridine (2),42,43 2,6-bis{1-[(2-isopro-
pylphenyl)imino]ethyl}pyridine (3),8,30,32,44 2,6-bis[1-(1-biphenylim-
ino)ethyl]pyridine (4),42,45 2-acetyl-6-{1-[(2,6-diisopropylphenyl)-
imino]ethyl}pyridine (5),46,47 2-acetyl-6-{1-[(2,6-dimethylphenyl)-
imino]ethyl}pyridine (7),36,47,48 2-{1-[(2-isopropylphenyl)imino]ethyl}-
6-{1-[(2,6-diisopropylphenyl)imino]ethyl}pyridine (9),44 {2,6-bis-
[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine}iron(II) chloride
(12),7a,10,30a {2,6-bis[1-(anthracenylimino)ethyl]pyridine}iron(II) chlo-
ride (13),49 {2,6-bis[1-((2-isopropylphenyl)imino)ethyl]pyridine}-
iron(II) chloride (14),30,50 {2-[1-((2-isopropylphenyl)imino)ethyl]-
6-[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine}iron(II) chloride
(17),16 {2-acetyl-6-[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine}-
iron(II) chloride (18),34 and {2-acetyl-6-[1-((2,6-diisopropylphenyl)-
imino)ethyl]pyridine}chromium(II) chloride (19)36 were prepared
according to published methods.
102-103 (T < 40 °C) 104 (T < 40 °C)
104-105 (T > 40 °C) 102-103 (T > 40 °C)
16
13
103-105
103-105
103
102-103
a Dependent on the reaction temperature; in units of kg of PE ((mol of
Fe) h bar)-1
.
For propene polymerization only small activity was noted
for complex 16, in comparison to the results for the ethene
polymerization. The average activity at 0 °C was 1500 kg of
PP ((mol of Fe) h bar)-1, which decreases rapidly at higher
temperatures (60 °C). The oligomers obtained by reaction at
0 °C have a molecular weight of around 200; thus, in this case
the temperature has only a very small influence on the molecular
weight.
Conclusion
We were able to show a systematic dependence of the
molecular weights of the polymers on the steric bulk of the
substituents coordinated at the ortho position of the N-aryl
groups. Using {2,6-bis[1-((2,6-diisopropylphenyl)imino)ethyl]-
pyridine}iron(II) chloride (12), high-molecular-weight polyeth-
ylene was obtained;7,10,30 however, if one isopropyl group is
removed, such as in complex 17, at low temperatures small
quantities of high-molecular-weight polyethylene (6 × 105) were
formed. The main product has a molecular weight of 104. If
two isopropyl groups are removed, such as for the symmetric
complex 14, the molecular weight of the produced polymer is
even lower than that of complex 12. With complex 14 polymers
of molecular weight 104-105, and large quantities of low-
molecular-weight oligomers (Mw ) 102-103) were obtained.
These observations correlate very well with the steric hindrance
of the ortho substituents of the N-aryl rings and results from
the blockage of the axial position. With this blockage of the
axial positions chain transfer reactions are disfavored, which
results in higher molecular weight polymers. Similar trends were
obtained for the reaction temperature dependence. For the less
sterically bulky complex 14, the best results were obtained at
20 °C; when the steric hindrance of the complex was increased,
as in complex 17, the maximum activity was obtained at lower
temperatures (0 °C).
For polymerization activities of the homologous row of
complexes nearly equal or identical values were obtained;
changes at the ortho substituents result only in an increase or
decrease in molecular weight of the product polymers, not in
the activity of the catalyst (Table 5).
Similar trends were obtained by replacing the (2,6-diisopro-
pylphenyl)imino group of the {2,6-bis[1-((2,6-diisopropylphenyl)-
imino)ethyl]pyridine}iron(II) chloride complex 12 by an an-
thracenylimino group. The steric bulk of the resulting complex
16 is decreased dramatically, such that only oligomers with
molecular weights of 500-1000 were observed. When both (2,6-
diisopropylphenyl)imino groups were substituted by anthracenyl
groups (as in complex 13), even smaller molecular weight
oligomers were obtained in insignificant concentrations. These
observations correlate very well with the decreased steric
hindrance of the ortho substituents of the N-aryl rings, where
(41) Brookhart, M. S.; Small, B. L. WO 9830612 A1, 1998.
(42) Schmidt, R.; Hammon, U.; Welch, M. B.; Alt, H. G.; Hauger, B.
E.; Knudsen, R. D. U.S. Patent 6458905 B1, 2002.
(43) Benvenuti, F.; Francois, P. Eur. Patent EP 1260515 A1, 2002.
(44) Ma, Z.; Sun, W.-H.; Li, Z.-L.; Shao, C.-X.; Hu, Y.-L. Chin. J. Polym.
Sci. 2002, 20, 205.
(45) Bennett, A. M. A. WO 9951550 A1, 1999.
(46) Gibson, V. C.; Kimberley, B. S.; Solan, G. A. WO 2000020427
A1, 2000.
(47) Bianchini, C.; Mantovani, G.; Meli, A.; Migliacci, F.; Zanobini,
F.; Laschi, F.; Sommazzi, A. Eur. J. Inorg. Chem. 2003, 1620.
(48) Mestroni, G.; Bianchini, C.; Sommazzi, A.; Milani, B.; Mantovani,
G.; Masi, F.; Meli, A.; Santi, R. WO 2002010133 A1, 2002.
(49) Benvenuti, F.; Francois, P., Razavi, A.; Marin, V.; Lopez, M. U.S.
Patent 2005090631 A1, 2005.
(50) Gibson, V. C. WO 9830612, 1998; WO 9902472 A1, 1999.

Iminopyridine Complexes of 3d Metals
Organometallics, Vol. 26, No. 4, 2007 997
2,6-Bis[1-(anthracenylimino)ethyl]pyridine (2). This compound
was prepared according to the method given in the literature.42,43
Yield: 77%. Mp: 220 °C dec. Anal. Calcd for C37H27N3 (513.63):
C, 86.52; H, 5.30; N, 8.18. Found: C, 86.18; H, 5.47; N, 7.86. 1H
NMR (CDCl3): δ 2.47 (s, 6H, CH3CdN), 6.82 (d, 2H, 3JHH ) 6.7
Hz), 7.42-7.51 (m, 6H), 7.82 (d, 2H, 3JHH ) 8.2 Hz), 7.97 (d, 2H,
After 5 days under reflux conditions the reaction suspension was
filtered and the residue was washed with toluene. The reddish
toluene solution was removed in vacuo, and the red-brown solid
was washed twice with methanol (10 mL). The yellow product 8
was isolated by filtration and dried in vacuo. Yield: 1.25 g (62%).
Mp: 180 °C dec. Anal. Calcd for C35H35N3 (497.67): C, 84.47;
3
3
1
3JHH ) 8.2 Hz), 8.01 (d, 2H, JHH ) 8.2 Hz), 8.09 (t, 1H, JHH
)
H, 7.09; N, 8.44. Found: C, 83.93; H, 7.45; N, 8.06. H NMR
3
7.5 Hz), 8.39 (s, 2H), 8.48 (s, 2H), 8.73 (d, 2H, JHH ) 7.5 Hz,
py). 13C{1H} NMR (CDCl3): δ 16.5 (NdCMe), 111.6, 122.3, 122.8,
124.0, 125.2 (Cquat), 125.3, 125.3, 125.6, 126.3, 128.0, 128.6, 131.4
(Cquat), 131.9 (Cquat), 132.3 (Cquat), 137.2, 147.5 (Cquat), 155.5 (Cquat),
168.5 (CdN). IR (KBr): ν 3045.8 m, 2923.1 m, 1633.0 s (2 Cd
N), 1566.7 m, 1556.6 m, 1536.0 m, 1453.4 m, 1360.0 m, 1311.4
m, 1240.3 m, 1193.7 m, 1119.8 m, 957.1 w, 875.2 s, 821.7 m,
803.2 m, 730.0 s, 471.1 m cm-1. MS (CI): m/z 513.4 [M+]; 498.3
[M+ - Me]; 321.2 [M+ - NHC14H9].
(-40 °C, toluene-d8): δ 0.90 (s, 3H, CHMe2, rotamer I), 0.99 (d,
3
3H, JHH ) 8.0 Hz, CHMe2, rotamer I), 1.15 (br, 12H, CHMe2,
rotamer II), 1.23 (br, 6H, CHMe2, rotamer I), 2.35 (s, 3H, MeCd
N), 2.43 (s, 3H, MeCdN), 2.59 (m, 1H, CHMe2, rotamer I), 2.85
(m, 1H, CHMe2, rotamer I), 2.97 (m, 2H, CHMe2, rotamer II), 6.15
(s, 1H, aryl), 6.37 (s, 1H, aryl), 7.18-7.23 (m, 5H, aryl), 7.40 (s,
1H, aryl), 7.51 (m, 1H, aryl), 7.71-7.76 (m, 2H, aryl), 8.06 (s,
1H, aryl), 8.21 (s, 1H, aryl), 8.42 (s, 1H, aryl), 8.58 (s, 1H, aryl).
13C{1H} NMR (CD2Cl2): δ 16.6 (NdCMe), 17.4 (NdCMe), 22.6
(CHMe), 22.9 (CHMe), 23.2 (CHMe), 23.4 (CHMe), 28.4 (CHMe),
28.6 (CHMe), 117.1, 119.5, 119.6, 120.2, 121.2, 123.2, 123.3, 123.8,
124.6, 125.0, 125.7, 126.1, 126.9, 128.2, 128.6, 131.5, 132.2, 132.5,
136.1, 136.2, 137.4, 137.5, 137.9, 139.6, 146.8, 147.0, 155.9 (aryl),
165.5 (CdN), 167.4 (CdN). IR (KBr): ν 3062.1 m, 2961.1 s,
2923.1 m, 2861.5 m, 1646.6 s, 1569.0 s, 1456.0 s, 1400.0 w, 1363.2
m, 1300.0 w, 1260.4 m, 1111.6 m, 1015.4 m, 814.3 s, 738.5 w,
668.4 m cm-1. MS (CI): m/z 496.8 [M+], 480.9 [M+ - Me], 465.9
[M+ - 2 Me].
2,6-Bis[1-(1-biphenylimino)ethyl]pyridine (4). This compound
was prepared according to the method given in the literature.42,45
Yield 88%. Mp: 145 °C. Anal. Calcd for C33H27N3 (465.59): C,
1
85.13; H, 5.85; N, 9.03. Found: C, 85.04; H, 5.81; N, 9.00. H
NMR (CDCl3): δ 2.13 (s, 6H, MeCdN), 6.79 (d, 2H, JHH ) 7.5
Hz, aryl), 7.19 (t, 4H, JHH ) 7.5 Hz, aryl), 7.27 (t, 4H, JHH ) 7.5
Hz, aryl), 7.33 (dt, 2H, JHH ) 8.0 Hz, aryl), 7.40 (d, 6H, JHH ) 8.0
Hz, aryl), 7.75 (t, 1H, JHH ) 7.7 Hz, Hp py), 8.09 (d, 2H, JHH
)
8.0 Hz, Hm py). 13C{1H} NMR (CDCl3): δ 17.1 (MeCdN), 119.8,
122.5, 124.4, 126.2 (Cquat), 126.9, 128.2, 129.5, 130.7, 132.1 (Cquat),
137.1, 140.2 (Cquat), 149.1 (Cquat), 155.4 (Cquat), 167.4 (CdN). IR
(KBr): ν 3046.7 m, 1649.4 s, 1575.9 m, 1566.8 m, 1472.7 s, 1432.4
m, 1363.6 s, 1249.2 m, 1209.9 s, 1111.6 m, 1008.5 w, 825.3 m,
771.4 m, 741.5 s, 698.8 s, 645.8 w, 615.0 w, 500.3 w cm-1. MS
(CI): m/z 465.1 [M+], 449.9 [M+ - Me], 312.0 [M+ - C6H8+],
152.1 [C6H8+].
2-{1-(2-Isopropylphenyl)imino]ethyl}-6-{1-[(2,6-diisopropyl-
phenyl)imino]ethyl}pyridine (9). A 0.4 mL portion (2.80 mmol,
2 equiv) of 2-isopropylaniline was added to a stirred solution of 5
(0.45 g, 1.40 mmol) in toluene (30 mL). Molecular sieves (4 Å)
and 10 mg of p-toluenesulfonic acid were used as drying agent
and catalyst. After 24 h under reflux conditions the reaction
suspension was filtered and the residue was washed with toluene.
The toluene solution was removed by filtration, and the solid was
washed twice with methanol (10 mL) and dried in vacuo. Yield:
350 mg (57%). Mp: 158 °C. Anal. Calcd for C30H37N3 (439.64):
C, 81.96; H, 8.48; N, 9.56. Found: C, 81.45; H, 8.64; N, 9.33. 1H
NMR (CDCl3): δ 1.15 (d, 12H, 3JHH ) 6.9 Hz, CHMe2), 1.19 (d,
2-Acetyl-6-{1-[(2-isopropylphenyl)imino]ethyl}pyridine (6). A
2.00 g portion (12.2 mmol) of 2,6-diacetylpyridine was dissolved
in 50 mL of EtOH and reacted with 0.98 equiv (11.9 mmol, 1.65
mL) of 2-isopropylaniline, acetic acid (100%; 0.1 mL) and
molecular sieves (4 Å). The reaction mixture was refluxed for 24
h, and afterward the solution was filtered and washed twice with
20 mL of EtOH. The yellow solution was stored at -30 °C
overnight to precipitate the side product. The mother liquor was
reduced to half of the original volume and stored at -30 °C to
precipitate the second fraction. The second fraction was dried in
vacuo to give the desired product as a yellow powder in 53% yield
(6.3 mmol, 1.76 g). Mp: 76 °C. Anal. Calcd for C18H20N2O
(280.36): C, 77.11; H, 7.19; N, 9.99. Found: C, 76.88; H, 7.02;
N, 10.09. 1H NMR (CDCl3): δ 1.17 (d, 6H, JHH ) 7.1 Hz, CHMe2),
2.37 (s, 3H, MeCdN), 2.77 (s, 3H, MeCdO), 2.93-3.00 (q, 1H,
JHH ) 7.0 Hz, CHMe2), 6.61 (d, 1H, JHH ) 7.5 Hz, aryl), 7.02 (t,
1H, JHH ) 7.6 Hz, aryl), 7.17 (t, 1H, JHH ) 7.5 Hz, aryl), 7.31 (d,
1H, JHH ) 7.5 Hz, aryl), 7.91 (t, 1H, JHH ) 7.6 Hz, Hp py), 8.10
(d, 1H, JHH ) 7.4 Hz, Hm py), 8.50 (d, 1H, JHH ) 7.2 Hz, Hm py).
13C{1H} NMR (CDCl3): δ 16.2 (MeCdN), 22.8 (CHMe2), 25.6
(MeCdO), 28.4 (CHMe2), 118.2, 122.4, 124.2, 124.6, 125.7, 126.1,
137.2, 138.1 (Cquat), 148.4 (Cquat), 152.4 (Cquat), 155.9 (Cquat), 165.9
(CdN), 200.1 (CdO). IR (KBr): ν 3059.8 m, 2960.4 s, 2925.1 m,
2871.6 w, 1695.6 s, 1647.6 s, 1592.3 m, 1578.0 m, 1481.8 s, 1443.6
s, 1406.8 m, 1361.8 s, 1311.9 m, 1243.9 s, 1221.5 s, 1145.6 w,
1114.4 s, 1075.7 m, 1033.9 m, 994.1 m, 947.4 m, 821.8 s, 804.0
m, 768.0 m, 748.6 s, 724.6 m, 690.6 w, 646.4 w, 596.3 m, 494.2
w, 420.3 w cm-1. MS (CI): m/z 280.2 (M+), 265.1 (M+ - Me).
GC-MS: Rt ) 22.13 min; m/z 280 [M+], 265 [M+ - Me], 250
[M+ - Me], 160 [M+ - C9H12], 144 [M+ - NC8H10].
3
6H, JHH ) 6.8 Hz, CHMe2), 2.27 (s, 3H, NdCMe), 2.39 (s, 3H,
NdCMe), 2.77 (sept., 2H, 3JHH ) 6.9 Hz, CHMe2), 3.02 (sept, 1H,
3JHH ) 6.8 Hz, CHMe2), 6.64 (d, 1H;3JHH ) 8.0 Hz, aryl), 7.08-
3
7.13 (m, 2H, aryl), 7.17-7.21 (m, 3H, aryl), 7.32 (d, 1H, JHH
)
3
7.8 Hz, aryl), 7.91 (t, 1H, JHH ) 7.6 Hz, Hp py), 8.40-8.55 (m,
2H, Hm py). 13C{1H} NMR (CDCl3): δ 16.4 (NdCMe), 17.1 (Nd
CMe), 22.8 (CHMe2), 22.9 (CHMe2), 23.2 (CHMe2), 28.3 (CHMe2),
28.5 (CHMe2), 118.4, 122.1, 122.3, 123.0, 123.6, 124.0, 125.7,
126.1, 135.8, 136.8, 138.1, 146.5, 148.7, 155.1, 155.6 (aryl), 166.5
(CdN), 166.9 (CdN). IR (KBr): ν 3065.5 m, 2959.7 s, 2925.1 m,
2866.2 m, 1637.6 s (CdN), 1594.5 m, 1567.6 m, 1480.1 m, 1455.1
m, 1381.7 m, 1364.2 s, 1222.9 m, 1191.8 m, 1122.6 m, 1075.9 w,
829.5 m, 777.6 m, 762.2 m, 750.8 m cm-1. MS (CI): m/z 439
[M+], 424 [M+ - Me], 397 [M+ - C(Me)2], 382 [M+ - (C(Me)2
+ Me)].
Styrol-Functionalized, 4-Vinylbenzyl-Functionalized 2,6-Bis-
{1-[(2,6-diisopropylphenyl)imino]ethyl}pyridine (10). A 2.00 g
(4.15 mmol) portion of compound 1 was dissolved in 70 mL of
THF, and with vigorous stirring 1.03 equiv (4.27 mmol, 2.14 mL)
of LDA was added to the reaction solution. After 14 h 1 equiv
(4.15 mmol, 0.58 mL) of 4-vinylbenzyl chloride was added to the
dark green solution. The combined reaction mixture was stirred
for 5 days under reflux. Afterward, the solvent was evaporated,
the reddish precipitate was extracted three times with 20 mL of
n-pentane, and the extracts were filtered. The filtrate was dried in
vacuo. The red solid was washed with ethanol and dried to give
complex 10 in 40% yield (1.00 g). Anal. Calcd for C42H51N3
(597.87): C, 84.37; H, 8.60; N, 7.03. Found: C, 83.96; H, 8.31;
N, 6.59. MS (CI): m/z 597.4 [M+], 582.4 [M+ - Me], 554.4 [M+
- (Me + vinyl)]. Two stereoisomers were obtained in a 3:1 ratio.
2-[1-(Anthracenylimino)ethyl]-6-{1-[(2,6-(diisopropylphenyl)-
imino]ethyl}pyridine (8). A 0.37 g portion of 1-aminoanthracene
(1.92 mmol, 0.98 equiv) was added to a stirred solution of 5 (0.63
g, 1.96 mmol) in toluene (40 mL). Molecular sieves (4 Å) and 10
mg of p-toluenesulfonic acid were used as drying agent and catalyst.

998 Organometallics, Vol. 26, No. 4, 2007
Kaul et al.
Main isomer: 1H NMR (CDCl3) δ 1.14-1.25 (m, 24H, HCMe2),
2.31 (s, 3H, Me2CdN), 2.74-2.84 (m, 6H, HCMe2 & 1CH2), 2.96-
3.01 (m, 2H, 2CH2), 5.14 (d, 1H, JHH ) 10.9 Hz, CHdCH2), 5.62
(d, 1H, JHH ) 17.6 Hz, CHdCH2), 6.57 (dd, 1H, JHH ) 17.5, 10.9
Hz, CHdCH2), 6.95 (d, 2H, JHH ) 7.9 Hz, styrene), 7.08-7.12
(m, 2H, aryl), 7.17-7.19 (m, 4H, aryl), 7.21 (d, JHH ) 7.9 Hz,
styrene), 7.96 (t, 1H, JHH ) 7.9 Hz, Hp py), 8.48 (pseudo-t, 2H,
Hm py); 13C{1H} NMR (CDCl3) δ 17.4 (MeCdN), 22.2 (CHMe2),
22.9 (CHMe2), 23.2 (CHMe2), 23.6 (CHMe2), 28.3 (CHMe2), 28.4
(CHMe2), 28.4 (CHMe2), 32.5 (C2), 32.6 (C1), 113.2 (CHdCH2),
122.2 (Cm py), 123.0 (aryl), 123.0 (aryl), 123.1 (Cm py), 123.6
(styrene), 126.3 (aryl), 126.6 (Cquat), 128.2 (styrene), 135.3 (Cquat),
135.5 (Cquat), 136.4 (CHdCH2), 137.1 (Cp py), 141.3 (Cquat), 146.0
(Cquat), 146.5 (Cquat), 145.5 (Cquat), 155.3 (Cquat), 166.8 (CdN), 168.4
(CdN); IR (KBr) ν 3060.5 w, 2960.3 s, 2925.6 m, 2866.3 m, 1634.0
s, 1568.1 w, 1510.9 w, 1457.0 m, 1362.6 s, 1323.0 w, 1237.0 m,
1192.5 m, 1109.8 m, 988.0 w, 904.7 w, 825.8 m, 759.9 m, 690.9
solvent was removed by filtration, and the precipitate was dried in
vacuo. Yield: 0.30 g (92%). Mp: 230 °C dec. Anal. Calcd for
C30H37N3Cl2Fe (566.39): C, 63.62; H, 6.58; N, 7.42. Found: C,
63.45; H, 6.82; N, 7.12. IR (KBr): ν 3069.9 m, 2962.1 s, 2923.1
m, 2867.7 m, 1622.1 m, 1584.5 s, 1484.2 m, 1443.7 m, 1371.5 s,
1264.3 s, 1225.1 m, 1205.0 m, 1103.4 w, 1059.2 w, 1031.6 w,
813.3 m, 781.6 m, 753.7 m cm-1. MS (FAB): m/z 565.2 [M+],
530.4 [M+ - Cl], 514.4 [M+ - (Cl, Me)], 495.5 [M+ - 2Cl].
Styrol-Functionalized [Bis(imino)pyridine]iron(II) Complex
11. To 200 mg of ligand 10 (0.34 mmol) dissolved in 15 mL of
THF was added 0.98 equiv of FeCl2·4H2O (65 mg). The solution
was stirred for 14 h and the product precipitated after the addition
of 20 mL of n-pentane at -2 °C. After filtration and drying in
vacuo complex 11 was obtained in 66% yield (157 mg). Mp: >250
°C. Anal. Calcd for C42H51N3Cl2Fe (724.62): C, 69.62; H, 7.09;
N, 5.80. Found: C, 69.12; H, 7.28; N, 5.65. IR (KBr): ν 3061.0
m, 2962.7 s, 2926.0 m, 2866.9 m, 1625.5 m, 1577.1 s, 1511.8 w,
1464.5 s, 1383.8 m, 1371.1 m, 1325.4 w, 1269.8 m, 1203.7 w,
1186.3 w, 1103.7 m, 1057.0 m, 988.7 w, 936.5 w, 823.4 w, 815.3
m, 797.9 m, 777.3 m, 715.3 w cm-1. MS (FAB): m/z 723.8 [M+],
688.7 [M+ - Cl], 653.6 [M+ - 2Cl], 597.9 [M+ - FeCl2].
{2-Acetyl-6-[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine}-
manganese(II) Chloride (20). To 200 mg (0.62 mmol) of ligand
5 was added 0.98 equiv of MnCl2·4H2O (119 mg) in a Schlenk
tube. After addition of 15 mL of THF a yellow suspension was
formed, and after 15 min the solution became cloudy. The solution
was stirred at 50 °C for 14 h to give a beige suspension. The residue
was obtained by filtration and was washed twice with 10 mL of
DCM. After drying in vacuo complex 20 was obtained in 67% (177
mg) yield. Anal. Calcd for C21H26N2Cl2MnO (448.29): C, 56.26;
H, 5.85; N, 6.25. Found: C, 56.97; H, 6.31; N, 6.11. IR (KBr): ν
3063.0 m, 2923.8 w, 2877.6 w, 1676.6 s, 1621.4 s, 1588.6 s, 1464.0
m, 1366.9 s, 1307.3 w, 1245.8 s, 1201.8 m, 1104.4 w, 1019.5 m,
814.4 m, 767.8 w, 690.6 w, 615.3 w, 436.4 w cm-1. MS (FAB):
m/z 412.5 [M+ - Cl], 322.8 [M+ - MnCl2].
{2-Acetyl-6-[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine}-
cobalt(II) Chloride (21). A 400 mg portion (1.24 mmol) of ligand
5 and 0.95 equiv of CoCl2·6H2O (280.6 mg) were dissolved in 10
mL of THF to give a green suspension, which was stirred for 14 h
at room temperature. After addition of 20 mL of diethyl ether a
precipitate was formed and was washed twice with 10 mL of diethyl
ether. After drying in vacuo complex 21 was obtained in 400 mg
(75%) yield. Crystals suitable for an X-ray analysis were obtained
from a dichloromethane solution. Anal. Calcd for C21H26N2Cl2CoO
(452.28): C, 55.77; H, 5.79; N, 6.19. Found: C, 55.97; H, 5.85;
N, 5.92. IR (KBr): ν 3081.3 m, 2956.9 s, 2924.4 m, 2867.4 m,
1675.9 s, 1588.6 s, 1462.1 s, 1442.3 m, 1366.5 s, 1310.2 m, 1248.1
s, 1094.3 m, 1056.1 m, 1025.0 s, 936.7 w, 818.1 s, 772.4 m, 691.9
w, 613.3 s, 440.0 w cm-1. MS (FAB): m/z 415.9 [M+ - Cl], 378.9
[M+ - 2Cl], 323.0 [M+ - CoCl2], 306.9 [M+ - (CoCl2, Me)].
w cm-1
.
{2,6-Bis[1-(anthracenylimino)ethyl]pyridine}iron(II) Chloride
(13). To a solution of 179 mg of FeIICl2·4H2O (0.9 mmol) in 10
mL of n-BuOH was slowly added a solution of 500 mg of ligand
2 (0.97 mmol) in 20 mL of n-BuOH. The color changed rapidly to
dark green. The suspension was heated for 30 min at 90 °C and
cooled over a period of 14 h to room temperature. The solvent
was removed in vacuo, and the dark green residue was washed
with 10 mL of diethyl ether and 10 mL of n-pentane. Yield: 0.57
g (98%). Mp: 255 °C dec. Anal. Calcd for C37H27N3Cl2Fe
(640.38): C, 69.40; H, 4.25; N, 6.56. Found: C, 68.98; H, 4.51;
N, 6.14. IR (KBr): ν 3049.9 s, 1618.5 s, 1584.1 s, 1593.5 m, 1455.4
m, 1426.6 m, 1371.2 s, 1311.6 m, 1267.3 s, 1208.0 m, 1132.3 w,
1030.9 w, 881.8 s, 810.2 m, 743.1 s, 732.2 s, 473.5 m cm-1. MS
(FAB): m/z 638.7 [M+ - H], 603.7 [M+ - ClH].
{2,6-Bis[1-(1-biphenylimino)ethyl]pyridine}iron(II) Chloride
(15). A 860 mg (1.85 mmol) portion of ligand 4 was added to 0.95
equiv (340 mg) of FeCl2·4H2O. After addition of 10 mL n-BuOH
the suspension changed color to dark green. The suspension was
stirred for 14 h at room temperature and was filtered afterward.
The residue was washed twice with 10 mL of toluene to give 0.93
g (90%) of complex 15. Suitable crystals were obtained by slow
diffusion of diethyl ether into a concentrated DCM solution of
complex 15. Anal. Calcd for C33H27N3Cl2Fe (592.34): C, 66.91;
H, 4.59; N, 7.09. Found: C, 66.52; H, 4.82; N, 6.84. IR (KBr): ν
3053.8 m, 2961.5 m, 1621.6 m, 1589.7 m, 1475.9 m, 1431.7 m,
1374.1 m, 1262.2 s, 1176.6 vs, 1046.4 m, 877.8 s, 812.1 m, 782.6
m, 745.6 s, 704.2 s, 573.8 s, 537.9 m cm-1. MS (FAB): m/z 592.8
[M+], 557.6 [M+ - Cl], 521.7 [M+ - 2Cl], 465.9 [M+ - (2Cl,
Fe)].
{2-[1-(Anthracenylimino)ethyl]-6-[1-((2,6-diisopropylphenyl)-
imino)ethyl]pyridine}iron(II) Chloride (16). To a solution of 217
mg of FeIICl2·4H2O (1.09 mmol) in 10 mL of n-BuOH was added
570 mg of ligand 8 (suspended in 20 mL of n-BuOH). The
suspension was heated for 30 min at 90 °C, and afterward the dark
green suspension was stirred overnight at room temperature. The
solvent was removed in vacuo, and the green-bronze residue was
washed with 10 mL of diethyl ether and 10 mL of n-pentane.
Yield: 0.44 g (64%). Mp: 235 °C dec. Anal. Calcd for C35H35N3-
Cl2Fe (624.42): C, 67.32; H, 5.65; N, 6.73. Found: C, 67.65; H,
5.18; N, 6.40. IR (KBr): ν 3046.2 m, 2953.8 m, 1618.0 w, 1584.5
m, 1540.0 w, 1456.0 w, 1369.3 m, 1311.9 w, 1260.3 m, 1205.3 w,
1100.0 w, 876.0 s, 808.3 s, 730.9 s, 470.5 m cm-1. MS (FAB):
m/z 623.8 [M+], 608.8 [M+ - Me], 588.1 [M+ - Cl], 396.8 [M+
- (Cl, NHC14H9)].
{2-Acetyl-6-[1-(2,6-(diisopropylphenyl)imino)ethyl]pyridine}-
nickel(II) Chloride (22a). A 200 mg portion (0.62 mmol) of ligand
5 and 0.98 equiv of NiCl2·6H2O (281 mg) were dissolved in 10
mL of THF to give a clear solution. After 10 min the mixture
became cloudy. The solution was stirred for 14 h at 50 °C and was
filtered afterward. The residue was extracted twice with 10 mL of
DCM and dried in vacuo. Yield: 147 mg (54%). Anal. Calcd for
C21H26N2Cl2NiO (452.04): C, 55.80; H, 5.80; N, 6.20. Found: C,
55.22; H, 6.15; N, 5.88. IR (KBr): ν 3081.3 m, 2956.8 s, 2924.4
m, 2867.4 m, 1668.2 s, 1588.6 s, 1463.5 m, 1366.4 s, 1315.6 w,
1251.8 s, 1204.3 w, 1101.8 w, 1031.8 w, 818.3 s, 616.0 m cm-1
.
MS (FAB): m/z 414.5 [M+ - Cl], 379.7 [M+ - 2Cl], 363.7 [M+
- (2Cl, Me)].
{2-[1-((2-Isopropylphenyl)imino)ethyl]-6-[1-((2,6-diisopropyl-
phenyl)imino)ethyl]pyridine}iron(II) Chloride (17). To a solution
of 117 mg of FeIICl2·4H2O (0.95 mmol) in 10 mL of THF was
added 260 mg of ligand 9. The color rapidly changed to dark blue.
The suspension was stirred for 14 h at room temperature. The
{2-Acetyl-6-[1-((2,6-diisopropylphenyl)imino)ethyl]pyridine}-
nickel(II) Bromide (22b). The procedure was the same as for
complex 22a, except that (DME)NiBr2 and as the solvent dichlo-
romethane (20 mL) were used. The precipitate was washed twice

Iminopyridine Complexes of 3d Metals
Organometallics, Vol. 26, No. 4, 2007 999
with 10 mL of toluene. Crystals suitable for an X-ray analysis were
obtained from a saturated dichloromethane solution overlayered with
n-pentane. Yield: 400 mg (96%). Anal. Calcd for C21H26N2Br2-
NiO (540.95): C, 46.63; H, 4.84; N, 5.18. Found: C, 46.18; H,
4.73; N, 4.58. IR (KBr): ν 3065.7 m, 2969.7 s, 2919.8 m, 2860.1
m, 1673.3 s, 1616.7 w, 1591.9 s, 1458.8 m, 1370.0 m, 1312.6 w,
1250.4 m, 1057.7 m, 1029.9 m, 998.4 m, 811.8 s, 772.2 m, 742.5
m, 694.6 m, 612.5 m, 443.7 m cm-1. MS (FAB): m/z 540.1 [M+],
460.1 [M+ - Br], 380.0 [M+ - 2Br], 365 [M+ - (2Br, Me)].
{2-Acetyl-6-[1-((2,6-dimethylphenyl)imino)ethyl]pyridine}-
nickel(II) Bromide (23). In a glovebox 225 mg (DME)NiBr2 (0.73
mmol, 0.98 equiv) was dissolved in 10 mL of DCM and the
suspension was stirred at room temperature. A 200 mg portion (0.75
mmol) of ligand 7 in 5 mL of DCM was added via canula. In the
first 30 min the color changed to brown. The reaction mixture was
stirred for 14 h at room temperature. The solvent was removed in
vacuo, and the residue was washed twice with toluene (10 mL)
and dried in vacuo. Yield: 325 mg (92%). Anal. Calcd for
C17H18N2Br2NiO (484.84): C, 42.11; H, 3.74; N, 5.78. Found: C,
41.78; H, 3.55; N, 5.70. IR (KBr): ν 3061.5 m, 2961.5 w, 2915.4
m, 2846.2 w, 1667.6 s, 1590.3 s, 1470.4 m, 1369.4 m, 1252.4 s,
1215.5 s, 1101.8 w, 1036.0 w, 810.7 w, 784.0 w, 741.9 w, 698.1
w, 618.5 w cm-1. MS (FAB): m/z 484.5 [M+], 404.6 [M+ - Br],
324.7 [M+ - 2Br], 309.7 [M+ - (2Br, Me)].
{2-Acetyl-6-[1-((2-isopropylphenyl)imino)ethyl]pyridine}-
nickel(II) Bromide (24). The procedure was the same as for
complex 23. Complex 24 was obtained using 200 mg (0.71 mmol)
of ligand 6 and 0.98 equiv of (DME)NiBr2 (214.8 mg) in 88%
yield (303 mg). Anal. Calcd for C18H20N2Br2NiO (498.87): C,
43.34; H, 4.04; N, 5.62. Found: C, 43.78; H, 4.25; N, 6.00. IR
(KBr): ν 3076.4 m, 2969.8 s, 2920.3 m, 1666.5 s, 1586.7 s, 1484.9
m, 1442.3 m, 1375.6 m, 1360.6 m, 1310.1 w, 1252.2 s, 1225.9 w,
1202.0 w, 1098.6 m, 1032.5 w, 815.7 m, 787.0 m, 668.4 m, 612.3
w, 496.3 w cm-1. MS (FAB): m/z 498.6 [M+], 418.7 [M+ - Br],
338.8 [M+ - 2Br], 323.8 [M+ - (2Br, Me)].
Single-Crystal X-ray Structure Determination of Compounds
15, 18‚CH2Cl2, 21‚CH2Cl2, and 22b. Crystal data and details of
the structure determination are presented in Table 3. Single crystals
suitable for the X-ray diffraction study were grown by diffusion of
n-pentane in saturated solutions of 15, 18, 21, and 22b in
dichloromethane. A clear blue plate (purple needle, green needle,
red fragment) was stored under perfluorinated ether, transferred to
a Lindemann capillary, fixed, and sealed. Preliminary examination
and data collection were carried out on area detecting systems (Stoe
IPDS or Nonius Mach3, κ-CCD) at the window of a rotating anode
(Nonius FR591) with graphite-monochromated Mo KR radiation
(λ ) 0.710 73 Å). The unit cell parameters were obtained by full-
matrix least-squares refinement of 43 241 (3909, 55 692, 58 666)
reflections. Data collections were performed at 143 (173, 153, 153)
K (Oxford Cryosystems) within a θ range of 1.83° < θ < 26.20°
(2.81° < θ < 25.60°, 1.70° < θ < 25.36°, 2.33° < θ < 25.38°).
A total number of 12 033 (4300, 9292, 8080) intensities were
integrated. Raw data were corrected for Lorentz and polarization
and, arising from the scaling procedure, for latent decay and
absorption effects. After merging (Rint ) 0.020 (0.103, 0.010,
0.027)) sums of 6247 (2234, 4744, 4148) (all data) and 5303 (1450,
4450, 4028) (I > 2σ(I)) respectively remained and all data were
used. The structures were solved by a combination of direct methods
and difference Fourier syntheses. All non-hydrogen atoms were
refined with anisotropic displacement parameters. For 15, 21‚CH2-
Cl2, and 22b, all hydrogen atoms were found and refined with
individual isotropic displacement parameters. For 18‚CH2Cl2, all
hydrogen atoms were placed in calculated positions and refined
using a riding model, with methylene and aromatic C-H distances
of 1.00, 0.98, and 0.95 Å, respectively, and Uiso(H) ) 1.2[Ueq(C)]
or 1.5[Ueq(C)]. Full-matrix least-squares refinements with 460 (271,
2
383, 348) parameters were carried out by minimizing ∑w(Fo
-
Fc2)2 with the Shelxl-97 weighting scheme and stopped at shift/
error < 0.001. The final residual electron density maps showed no
remarkable features. Neutral atom scattering factors for all atoms
and anomalous dispersion corrections for the non-hydrogen atoms
were taken from the International Tables for Crystallography. All
calculations were performed on an Intel Pentium 4 PC, including
the programs Platon, Sir92, and Shelxl-97.51 For 15, a problem with
unresolvable solvent molecules in the unit cell was cured with the
Platon calc squeeze procedure. For 18‚CH2Cl2, the relatively high
R values and the low reflection count are the result of a very tiny
crystal and severe twinning problems. 18‚CH2Cl2 is isostructural
with 21‚CH2Cl2. For 22b, the correct enantiomer is proved by
Flack’s parameter ꢀ ) 0.004(6). Crystallographic data (excluding
structure factors) for the structures reported in this paper have been
deposited with the Cambridge Crystallographic Data Center as
Supplementary Publication Nos. CCDC-627692 (15), CCDC-
627693 [18‚(CH2Cl2)], CCDC-627694 [21‚(CH2Cl2)], and CCDC-
627695 (22b). Copies of the data can be obtained free of charge
on application to the CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (fax, (+44)1223-336-033; e-mail, deposit@ccdc.cam.ac.uk).
Acknowledgment. This work was generously supported by
the Deutsche Forschungsgemeinschaft and the Bayerische
Forschungsverbund Katalyse FORKAT and by NanoCat, an
International Graduate Program within the Elitenetzwerk Bayern
(postdoctoral fellowship to G.D.F.).
Supporting Information Available: CIF files, additional
figures, and tables of crystallographic data, atomic coordinates,
atomic displacement parameters, bond distances, and bond angles
for complexes 15, 18‚CH2Cl2, 21‚CH2Cl2, and 22b and tables giving
details of the oligomerization/polymerization results. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM060857Q
(51) (a) IPDS Operating System, Version 2.8; Stoe&Cie GmbH, Darm-
stadt, Germany, 1997. (b) Data Collection Software for Nonius k-CCD
devices; Enraf-Nonius, Delft, The Netherlands, 2001. (c) Otwinowski, Z.;
Minor, W. Methods Enzymol. 1997, 276, 307ff. (d) Altomare, A.; Cascarano,
G.; Giacovazzo, C.; Guagliardi, A.; Burla, M. C.; Polidori, G.; Camalli,
M. SIR92. J. Appl. Crystallogr. 1994, 27, 435. (e) International Tables for
Crystallography; Wilson, A. J. C., Ed.; Kluwer Academic: Dordrecht, The
Netherlands, 1992; Vol. C, Tables 6 .1.1.4, 4.2.6.8, and 4.2.4.2. (f) Spek,
A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht University,
Utrecht, The Netherlands, 2005. (g) Sheldrick, G. M. SHELXL-97;
Universita¨t Go¨ttingen, Go¨ttingen, Germany, 1998.