Bis(iminoethyl)pyridine systems with a pendant alkenyl group. Part A: Cobalt and iron complexes and their catalytic behavior

Article abstract of DOI:10.1021/om800726y

The acid-catalyzed reaction of 2,6-diacetylpyridine with 2,6-diisopropylaniline yielded the monoimi-noethylpyridine derivative 3. Its condensation reactions with allylamine or ω-aminobutene, -pentene, and -hexene furnished the unsymmetrically substituted

Full text of DOI:10.1021/om800726y

Organometallics 2008, 27, 6547–6556
6547
Bis(iminoethyl)pyridine Systems with a Pendant Alkenyl Group.
Part A: Cobalt and Iron Complexes and Their Catalytic Behavior†
Carolin Wallenhorst, Gerald Kehr, Heinrich Luftmann,§ Roland Fro¨hlich,‡ and
Gerhard Erker*
Organisch-Chemisches Institut der UniVersita¨t Mu¨nster, Corrensstrasse 40, 48149 Mu¨nster, Germany
ReceiVed July 30, 2008
The acid-catalyzed reaction of 2,6-diacetylpyridine with 2,6-diisopropylaniline yielded the monoimi-
noethylpyridine derivative 3. Its condensation reactions with allylamine or ω-aminobutene, -pentene,
and -hexene furnished the unsymmetrically substituted 6-(N-(n-alkenyl)iminoethyl)-2-(N-(2,6-diisopro-
pylphenyl)iminoethyl)pyridines 5a-d (5a-c were characterized by X-ray diffraction). Treatment of the
chelate ligands 5a-d with CoCl2 or FeCl2 gave the respective cobalt (7a-d) and iron complexes (8a-d)
in good yields (all cobalt complexes and 8b,c were characterized by X-ray crystal structure analyses).
The reaction of the cobalt(II) complex 7a with 3 molar equiv of methyllithium gave the corresponding
tridentate chelate ligand Co(I) methyl complex 11a (also characterized by X-ray diffraction). The complexes
7a-d, 8a-d, and 11a were activated with methylalumoxane (Al:M ) 300). The resulting cobalt-complex-
derived homogeneous Ziegler-Natta catalysts produced polyethylene, albeit with a rather low activity.
The iron-complex-derived catalysts were more active and gave mixtures of linear polyethylene and low-
molecular-weight oligoethylenes.
and showed substantially hindered rotation around the N-C(aryl)
vector) gave rise to very active catalyst systems for the
production of linear, relatively high molecular weight polyeth-
ylene.3 Introduction of smaller substituents at the aryl groups
led to ethylene oligomerization catalysts.4 Bianchini et al.5,6 have
described unsymmetrical systems (such as 2, see Scheme 1)
where one of the bulky 2,6-diisopropylphenyl groups was
replaced by an alkyl or aryl substituent. The catalysts derived
from such Fe complexes still were very active but typically gave
ethylene oligomers (in the C10 to C20 range) instead of
polyethylene.5
Introduction
The advent of homogeneous Ziegler-Natta catalysts has
brought substantial progress into the field of catalytic olefin
polymerization. Subsequent to the group 4 metallocenes and
related complexes1 the late-transition-metal “post-metallocene”
catalysts have received increased attention.2 Among them the
2,6-bis(iminoalkyl)pyridine ligands were found to be especially
useful. Their iron (and to a lesser extent cobalt) complexes often
gave very active olefin polymerization catalysts when activated
with methylalumoxane (MAO).3 The nature of the groups
attached at the imino nitrogen atoms was found to be critical.
Bulky 2,6-disubstituted aryl groups (e.g., 2,6-diisopropylphenyl
as in 1, which were oriented normal to the central ligand plane
Scheme 1
* To whom correspondence should be addressed. E-mail: erker@
uni-muenster.de.
† Dedicated to Professor Helmut Schwarz on the occasion of his 65th
birthday.
‡ X-ray crystal structure analyses.
§ Mass spectrometry.
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Brintzinger, H. H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.; Waymouth, R. M.
Angew. Chem. 1995, 107, 1255-1283; Angew. Chem., Int. Ed. 1995, 34,
1143-1170. (c) McKnight, A. L.; Waymouth, R. M. Chem. ReV. 1998, 98,
2587–2598. (d) Okuda, J.; Eberle, T. Half-Sandwich Complexes as
Metallocene Analogues In Metallocenes-Synthesis, ReactiVity, Applications;
Togni, A., Haltermann, R. L., Eds.; Wiley-VCH: Weinheim, Germany, 1998;
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100, 1391–1434. (f) Erker, G. Chem. Commun. 2003, 1469–147. (g) Erker,
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1999, 111, 448-468; Angew. Chem., Int. Ed. 1999, 38, 3842-8447. (b)
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7144.
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Peruch, F.; Lutz, P. J. Eur. J. Inorg. Chem. 2006, 4309–4316. (d) Bianchini,
C.; Gatteschi, D.; Giambastiani, G.; Rios, I. G.; Ienco, A.; Laschi, F.; Mealli,
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2720–2734. (g) Barbaro, P.; Bianchini, C.; Giambastiani, G.; Rios, I. G.;
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metallics 2007, 26, 4639–4651. (h) Bianchini, C.; Giambastiani, G.; Rios,
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10.1021/om800726y CCC: $40.75
2008 American Chemical Society
Publication on Web 11/20/2008

6548 Organometallics, Vol. 27, No. 24, 2008
Wallenhorst et al.
Figure 1. 1H NMR spectrum (D2-dichloromethane, 600 MHz, 298K) of the hexenyl-substituted chelate ligand 5d; aryl ) 2,6-diisopropylphenyl.
We have now prepared a series of similar bis(iminoethyl)py-
ridine ligands bearing terminal alkenyl groups at one nitrogen
and the usual 2,6-diisopropylphenyl substituent at the other. We
synthesized their cobalt and iron complexes and found that some
of the catalysts derived thereof showed some unexpected
properties.
Results and Discussion
Synthesis and Characterization of the Ligands. The
stepwise synthesis of the ligand systems 5a-d is straightfor-
ward. The first condensation reaction to yield the monoimine
system 3 was carried out by treatment of 2,6-diacetylpyridine
with 2,6-diisopropylaniline in methanol at 0 °C with the aid of
Figure 2. Molecular geometry of 5b.
substituent, the typical resonances of the terminal vinyl group,
and four multiplets corresponding to the tetramethylene tether.
a small amount of formic acid as catalyst, analogous to the
method described by Bianchini et al.5,7 A slight excess of the
There are two singlets resulting from the iminoethyl methyl
groups and one septet of 2H intensity corresponding to the
carbonyl component was used to diminish the amount of
isopropyl methine groups. The isopropyl methyl groups give
the unwanted bis-ketimine product formed. A small amount of
rise to a pair of doublets (each of 6H intensity). This indicates
the respective bis(iminoethyl)pyridine side product could be
an orthogonal orientation of the diisopropylphenyl substituent
removed by treatment with an ethanol/THF (2:1) mixture at
at nitrogen relative to the central bis(iminoethyl)pyridine plane.
The resulting element of axial prochirality renders the isopropyl
reflux temperatures. Subsequently, 3 was then reacted with the
alkenylamines 4a-d8 in methanol at 60 °C (16 h) to give the
methyl group pairwise diastereotopic.9 Systems 5a-c feature
unsymmetrical chelate ligands 5a-d in good yield (64-82%,
similar NMR spectra (for details see the Experimental Section
see Scheme 2). The products crystallized readily from solution
and the Supporting Information).
All chelate ligand systems 5a-c were characterized by X-ray
at 0 °C.
diffraction. These X-ray crystal structure analyses confirmed
the axially prochiral geometries that were assumed from the
NMR analysis. The structures of all three compounds are very
similar. Therefore, it will suffice to present and discuss the solid
state structure of the butenyl-substituted compound 5b as a
typical example. Details of the remaining compounds 5a,c are
found in the Experimental Section and the Supporting Informa-
tion.
Scheme 2
In the crystal state compound 5b features a planar core that
extends through both CdN units. The overall conformation is
of an extended W shape (see Figure 2). Both imino CdN bonds
are oriented coplanar with the central pyridine ring. They feature
dihedral angles of 179.6(1)° for N1-C2-C7-N9 and 172.9(1)°
for N1-C6-C22-N24. Both imino groups are in the E
configuration (dihedral angles C2-C7-N9-C10 ) 178.8(1)°,
C6-C22-N24-C25 ) 178.3(1)°). The plane of the 2,6-
diisopropylphenyl substituent at N9 is oriented in an orthogonal
position relative to the bis(iminoethyl)pyridine ligand core
(dihedral angle C7-N9-C10-C11 ) 90.8(2)°). Both of the
imino CdN bonds are short (C7-C9 ) 1.280(2) Å, C22-N24
) 1.278(2) Å).10
The ligand systems show very typical NMR data. Figure 1
shows the H NMR spectrum of 5d. It features three separate
pyridine resonances, a pair of aromatic CH signals of the N-aryl
1
For comparison we have also synthesized the saturated n-butyl
analogue of 5b: namely, compound 6b (see Scheme 3). This
(7) Layer, R. W. Chem. ReV. 1963, 63, 489–510.

Bis(iminoethyl)pyridine Systems
Organometallics, Vol. 27, No. 24, 2008 6549
Table 1. Selected Structural Data of the Complexes 7a-d (Co), 8c (Fe), and 11a (Co)a
7a 7b 7c 7d 8c
Co/1 Co/2 Co/3 Co/4 Fe/3
11a
Co/1
M/n
M-Cl1
2.305(2)
2.272(1)
119.3(1)
2.043(4)
2.215(4)
2.163(5)
1.274(7)
1.290(7)
93.4(1)
147.3(1)
74.2(2)
74.8(2)
98.3(1)
97.6(1)
2.302(1)
2.281(1)
119.3(1)
2.050(2)
2.229(2)
2.164(2)
1.283(2)
1.281(3)
96.9(1)
143.8(1)
74.3(1)
74.8(1)
98.1(1)
97.1(1)
2.268(1)
2.270(1)
120.3(1)
2.043(2)
2.253(2)
2.140(3)
1.273(4)
1.286(4)
98.8(1)
2.279(1)
2.274(1)
118.9(1)
2.047(3)
2.245(3)
2.161(3)
1.282(5)
1.283(5)
94.5(1)
146.6(1)
74.1(1)
75.2(1)
96.7(1)
98.7(1)
2.299(2)
2.281(2)
120.3(1)
2.072(5)
2.256(5)
2.166(6)
1.279(8)
1.292(8)
98.7(2)
M-Cl2
1.949(2)b
Cl1-M-Cl2
M-N1
1.818(2)
1.900(2)
1.899(2)
1.324(3)
1.316(3)
M-N9
M-N24
C7-N9
C22-N24
N1-M-Cl1
N1-M-Cl2
N1-M-N9
N1-M-N24
N9-M-Cl2
N24-M-Cl2
N24-M-N9
C2-C7-N9-C10
C7-N9-C10-C11
C7-N9-C10-C15
140.9(1)
74.0(1)
75.9(1)
141.1(1)
73.2(2)
74.2(2)
172.4(1)c
81.0(1)
81.1(1)
96.8(1)
98.1(1)
100.4(1)c
97.8(1)c
161.7(1)
178.1(2)
86.0(3)
100.1(1)
148.2(1)
-171.6(3)
-85.2(4)
95.6(3)
101.4(2)
146.1(2)
171.2(5)
86.6(8)
143.6(2)
178.5(4)
-96.1(6)
85.6(6)
144.9(1)
175.3(2)
88.6(2)
144.0(1)
173.4(3)
83.1(5)
-92.6(2)
-97.8(4)
-94.4(7)
-97.1(2)
a Bond lengths are given in Å and bond angles and dihedral angles in deg. b Co-CH3. c N-Co-CH3.
was obtained from the reaction of compound 3 with n-
butylamine under conditions analogous to those described above.
It was isolated in 90% yield. Compound 6b was also character-
ized by an X-ray crystal structure analysis. It shows features
similar to those found for the unsaturated analogues 5a-d (for
details see the Experimental Section and the Supporting Infor-
mation).
Scheme 3
Synthesis and Characterization of the Bis(iminoethyl)pyri-
dine Cobalt and Iron Complexes. We reacted each of the new
ligand systems 5a-d with anhydrous CoCl2 and with FeCl2,
Figure 3. Molecular geometry of the Fe complex 8c.
respectively. The corresponding chelate MCl2 complexes (M
) Co, 7a-d; M ) Fe, 8a-d) were obtained as green (Co(II))
or blue (Fe(II)) paramagnetic solids in yields ranging between
60% (8d) and 99% (7b). All four cobalt complexes 7a-d and
the iron complex 8c were characterized by X-ray diffraction.
We have also carried out an X-ray crystal structure analysis of
the iron complex 8b, which confirmed the proposed structure
(see the Supporting Information), but due to its rather large R
factor of 9%, details of this structure will not be discussed here.
We have also prepared the cobalt and iron complexes 9b and
10b, derived from the “saturated” ligand 6b, for comparison
(ca. 99% yield, see Scheme 4).
2,6-diisopropylphenyl substituent at N9 is rotated perpendicular
to the central chelate ligand plane (see Table 1 and Figure 3).11
Figure 4 shows the molecular structure of the cobalt complex
7b as a typical example of the 7a-d series. The overall
structural arrangement is analogous to that of the iron complex
8c (see Table 1). The Cl1-Co-Cl2 angle here amounts to
119.3(1)°, and the pyridine N1-Co-Cl1 angle is close to
normal (96.9(1)°). Again, the 2,6-diisopropylphenyl group at
N9 is rotated to stand perpendicular to the central chelate ligand
plane. The allyl end group of the butenyl substituent at the other
imino group is also rotated markedly. The structural features
The iron complex 8c features a structure that is located
somewhere between a distorted square pyramidal and a strongly
distorted trigonal bipyramidal coordination geometry of the
metal. The Fe-Cl1 bond is slightly longer than the Fe-Cl2
bond (∆d ≈ 0.02 Å). Both of the imine CdN bonds in 8c are
rather short (1.279(8) and 1.292(8) Å). The Fe-imine nitrogen
bonds are markedly larger than the central Fe-pyridine nitrogen
bond (2.256(5)/2.166(6) Å vs 2.072(5) Å). The central N3Fe
unit is very close to coplanar (dihedral angles N1-C6-C22-N24
) 0.7(9)°, N1-C2-C7-N9 ) 2.0(8)°). The pentenyl substitu-
ent at N24 is found in a fully extended conformation. The bulky
(8) The alkenylamine synthesis is analogous to those in: (a) Ettlinger,
M. G.; Hodgkins, J. E J. Am. Chem. Soc. 1955, 77, 1831–1836 (N-(4-
pentenyl)phthalimide). (b) Sato, T.; Nakamura, N.; Ikeda, K.; Okada, M.;
Ishibashi, H.; Ikeda, M J. Chem. Soc., Perkin Trans. 1 1992, 2399–2407(3-
butenylamine). (c) Gagne´, M. R.; Stern, C. L.; Marks, T. J. J. Am. Chem.
Soc. 1992, 114, 275–294(4-pentenylamine).
(9) Eliel, E. L.; Wilen, S. H.; Mander, L. N. Stereochemistry of Organic
Compounds; Wiley-VCH: New York, 1994; Chapter 14.
(10) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J. Chem. Soc., Perkin Trans. 2 1987, S1–S19.
(11) See, for a comparison: (a) Ca´mpora, J.; Naz, A. N.; Palma, P.;
´
Rodr´ıguez-Delgado, A.; Alvarez, E.; Tritto, I.; Boggioni, L. Eur. J. Inorg.
Chem. 2008, 1871–1879.

6550 Organometallics, Vol. 27, No. 24, 2008
Wallenhorst et al.
Scheme 4
Scheme 5
Figure 4. View of the molecular structure of the cobalt complex
7b.
of the remaining three examples (7a,c,d) in this series are very
similar (see Table 1 and the Supporting Information for further
details).12,13
Treatment of the paramagnetic cobalt dichloride complex 7a
with an excess of methyllithium (3 equiv) yielded the diamag-
netic cobalt(I) methyl complex 11a (89% isolated; Scheme
moiety are markedly different from those of the pentacoordi-
nated Co(II) systems (7a-d; see Table 1). In 11a the bonds of
cobalt to all three nitrogen atoms are much shorter than in 7.
The shortest is the Co-pyridine linkage at 1.818(2) Å (Co-N1),
but the Co-N(imine) bonds are also very short (Co-N9 )
1.900(2) Å, Co-N24 ) 1.899(2) Å). In 11a the imine
ligand-cobalt donor bonds are stronger than in 7, but at the
same time there seems to be substantially increased metal to
ligand back-bonding. Consequently, the imine CdN bond
lengths are substantially increased (C7-N9 ) 1.324(3) Å,
C22-N24 ) 1.316(3) Å) relative to 7 (∆d ≈ 0.04 Å) and the
adjacent C2-C7 (1.428(3) Å) and C6-C22 (1.440(3) Å) imine
connections to the pyridine ring decreased (∆d ≈ 0.05 Å). As
expected, the bulky 2,6-diisopropylphenyl substituent at N9 is
found in an orthogonal conformation. The vinyl end group of
the allyl substituent at the other imine nitrogen center (N24) is
also rotated normal to the central chelate ligand plane
(C22-N24-C25-C26 ) 90.8(3)°).
5).14,15 The H NMR spectrum of 11a (Figure 5) shows some
1
rather extraordinary features, such as the signal of the central
pyridine hydrogen 4-H at very a high δ value of 10.10 and the
pair of ketimine CH3 signals at negative δ values (-0.64,
-1.51). This may indicate an electronic structure of 11a similar
to those discussed by Budzelaar et al.16 for related systems
comprised of a low-spin cobalt(II) state antiferromagnetically
coupled with the radical anion of the ligand. The redox reaction
would in this interpretation have involved the noninnocent
ligand. The Co-CH3 1H NMR resonance of complex 11a was
located at δ 0.54.
Complex 11a was also characterized by an X-ray crystal
structure analysis (see Figure 6 and Table 1). The cobalt center
in complex 11a exhibits a distorted-square-planar coordination
geometry (N1-Co-C1 ) 172.4(1)°, N24-Co-N9 ) 161.7(1)°).
It features a Co-CH3 group (1.949(2) Å) trans to the pyridine
nitrogen atom. The bonding features of the chelate ligand-Co
(12) (a) Britovsek, G. J. P.; Gibson, V. C.; Hoarau, O. D.; Spitzmesser,
S. K.; White, A. J. P.; Williams, D. J. Inorg. Chem. 2003, 42, 3454–3465.
(b) Britovsek, G. J. P.; Mastroianni, S.; Solan, G. A.; Baugh, S. P. D.;
Redshaw, C.; Gibson, V. C.; White, A. J. P.; Williams, D. J.; Elsegood,
M. R. J. Chem. Eur. J. 2000, 6, 2221–2231. (c) Britovsek, G. J. P.; Gibson,
V. C.; Kimberley, B. S.; Mastroianni, S.; Redshaw, C.; Solan, G. A.; White,
A. J. P.; Williams, D. J. Dalton Trans. 2001, 1639–1644. (d) Gibson, V. C.;
Tellmann, K. P.; Humphries, M. J.; Wass, D. F. Chem. Commun. 2002,
2316–2317.
(13) (a) Reardon, D.; Conan, F.; Gambarotta, S.; Yap, G.; Wang, Q.
J. Am. Chem. Soc. 1999, 121, 9318–9325. (b) Dias, E. L.; Brookhart, M.;
White, P. S. Chem. Commun. 2001, 423–424. (c) Esteruelas, M. A.; Lopez,
A. M.; Mendez, L.; Olivan, M.; Onate, E. Organometallics 2003, 22, 395–
406. (d) Calderazzo, F.; Englert, U.; Pampaloni, G.; Santi, R.; Sommazzi,
A.; Zinna, M. Dalton Trans. 2005, 914–922.
Ethene Oligomerization and Polymerization. The metal
complexes described above in this study were briefly tested for
their ethene polymerization activities. Activation was carried
out by treatment with methylalumoxane, employing an Al:M
ratio of 300:1.17 The catalytic reactions were carried out in
toluene solution at room temperature in a Bu¨chi autoclave
system using a pressure of 2 bar of ethene. In several
experiments it was found that preactivation of the metal
complexes with MAO gave increased activities. All of the cobalt
complexes gave relatively low catalyst activities (for details see
the Supporting Information). The highest activities were found
with the systems 7a/MAO (activity ∼60 g of polyethylene/
((mmol of cat.) (bar of ethene) h)) and 11a/MAO (activity
(14) (a) Kooistra, T. M.; Knijnenburg, Q.; Smits, J. M. M.; Horton, A. D.;
Budzelaar, P. H. M.; Gal, A. W. Angew. Chem. 2001, 113, 4855-4858;
Angew. Chem., Int. Ed. 2001, 40, 4719-4722. (b) Gibson, V. C.; Humphries,
M. J.; Tellmann, K. P.; Wass, D. F.; White, A. J. P.; Williams, D. J. Chem.
Commun. 2001, 2252–2253.
(15) 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, 13955–13968.
(16) Knijnenburg, Q.; Hetterscheid, D.; Kooistra, T. M.; Budzelaar,
P. H. M. Eur. J. Inorg. Chem. 2004, 1204–1211.
(17) This seems to be an optimal ratio for such systems; see, e.g.:
Britovsek, G. J. P.; Bruce, M.; Gibson, V. C.; Kimberley, B. S.; Maddox,
P. J.; Mastroianni, S.; McTavish, S. J.; Redshaw, C.; Solan, G. A.;
Stro¨mberg, S.; White, A. J. P.; Williams, D. J J. Am. Chem. Soc. 1999,
121, 8728–8740.

Bis(iminoethyl)pyridine Systems
Organometallics, Vol. 27, No. 24, 2008 6551
1
Figure 5. H NMR spectrum of complex 11a (d8-toluene (*), 400 MHz, 298 K; aryl ) 2,6-diisopropylphenyl).
Table 2. Ethene Polymerization and Oligomerization at the Iron
Catalyst Systems 8/MAOa
amt of
amt of
c
compd t (min) PE (g) mp (°C) olig (g) Mn
PDI activityd
8a
30
30
60
60
60
60
17.8
15.3
1.7
0.5
5.9
125
124
121
120
124
119
5.5
5.7
4.8
6.4
2.4
288 1.28
310 1.15
256 1.23
236 1.27
231 1.23
247 1.31
466
419
65
69
83
8ab
8b
8c
8d
10b
0.9
12.8
137
a Conditions: 2 bar of ethene, 25 °C, 200 mL of toluene, Al:Fe )
300, 0.05 mmol of Fe complex, preactivated catalysts used.- b Without
preactivation. c Molecular weight of the oligomer fraction. d Total
activity (PE + oligomers), in units of g of PE + olig./((mmol of Fe) h
(bar of ethene)).
activation in the Bu¨chi autoclave gave only a slightly less active
catalyst (activity ∼420). The reaction produced a mixture of
polyethylene (shown to be linear PE by NMR and DSC) and a
substantial oligomeric fraction. The low-molecular-weight oli-
gomers were separated from the high-molecular-weight poly-
ethylene by extraction. They were analyzed by GPC and shown
to comprise a mixture of ca. 10- to 15-mers with a relatively
narrow molecular weight distribution (PDI ≈ 1.2-1.3).
Figure 6. Projection of the molecular geometry of the cobalt
complex 11a.
∼90).18 In all cases for the cobalt-derived catalyst systems
7/MAO or 11/MAO linear polyethylene was obtained.
The situation with the iron catalysts is somewhat different.
Treatment of the N-allyl iron complex 8a with MAO gave a
rather active catalyst system, as expected.19 With the preacti-
vated catalyst an overall activity of ∼470 was observed; direct
As expected, this is in stark contrast to the behavior of the
catalyst derived from the saturated N-(n-butyl) iron complex
10b. Its treatment with MAO gave a slightly less active catalyst
(activity ∼130) that produced mostly oligoethylenes (12.8 g
isolated after 60 min of reaction time) and only a very minor
amount of polyethylene (0.9 g) (cf. 8a/MAO: 5.5 g of oligomers
and 17.8 g of polyethylene after 30 min reaction time). The
remaining catalyst systems 8b-d/MAO fall between these
extremes: they all produce mixtures of the C10-C15 oligoeth-
ylenes with mostly substantial amounts of polyethylene (see
Table 2).
We actually expected that the catalysts derived from the
unsymmetrical Fe chelate complexes 8, featuring a rather small
linear alkenyl substituent at one of the imine nitrogen atoms,
would behave similar to the “Bianchini catalysts” (e.g., 2/MAO)5
and produce only low-molecular-weight linear ethene oligomers.
Our saturated example (10b/MAO) behaves just like that, but
some of the unsaturated systems 8/MAO show a strongly
(18) The [Co]-CH3 system apparently requires a special activation
mechanism; see, e.g. Jin, J.; Wilson, D. R.; Chen, E. Y.-X. Chem. Commun.
2002, 708–709.
(19) There is a controversial discussion about the actual active species
formed in the (N,N,N-chelate ligand)FeCl2 + MAO catalyst system; see
e.g.: (a) De Bruin, B.; Bill, E.; Bothe, E.; Weyhermu¨ller, T.; Wieghardt, K.
Inorg. Chem. 2000, 39, 2936–2947. (b) Britovsek, G. P. J.; Clentsmith,
G. K. B.; Gibson, V. C.; Goodgame, D. M. L; McTavish, S. J.; Pankhurst,
Q. A. Catal. Commun. 2002, 3, 207–211. (c) Britovsek, G. J. P.; Gibson,
V. C.; Spitzmesser, S. K.; Tellmann, K. P.; White, A. J. P.; Williams, D. J.
Dalton Trans. 2002, 1159–1171. (d) Enright, D.; Gambarotta, S.; Yap,
G. P. A.; Budzelaar, P. H. M. Angew. Chem. 2002, 114, 3309-3312; Angew.
Chem., Int. Ed. 2002, 41, 4029-4032. (e) Bryliakov, K. P.; Semikolenova,
N. V.; Zudin, V. N.; Zakharov, V. A.; Talsi, E. P. Cat. Commun. 2004, 5,
45–48. (f) Bryliakov, K. P.; Semikolenova, N. V.; Zakharov, V. A.; Talsi,
E. P. Organometallics 2004, 23, 5375–5378. (g) Ca´mpora, J.; Naz, A. M.;
´
Palma, P.; Alvarez, E.; Reyes, M. L. Organometallics 2005, 24, 4878–
(20) For remotely related examples, see e.g.: (a) Peifer, B.; Milius, W.;
Alt, H. G. J. Organomet. Chem. 1998, 553, 205–220. (b) Kaul, F. A. R.;
Puchta, G. T.; Schneider, H.; Bielert, F.; Mihalios, D.; Herrmann, W. A.
Organometallics 2002, 21, 74–82. (c) Licht, A. I.; Alt, H. G. J. Organomet.
Chem. 2002, 648, 134–148. (d) Zhu, H.; Jin, G.-X.; Hu, N. J. Organomet.
Chem. 2002, 655, 167–171. (e) Licht, A. I.; Alt, H. G. J. Organomet. Chem.
2003, 687, 142–152. (f) Go´mez-Ruiz, S.; Polo-Cero´n, D.; Prashar, S.;
Fajardo, M.; Ant˜ınolo, A.; Otero, A. Eur. J. Inorg. Chem. 2007, 4445–
4455.
4871. (h) Scott, J.; Gambarotta, S.; Korobkov, I.; Budzelaar, P. H. M.
Organometallics 2005, 24, 6298–6300. (i) Bouwkamp, M. W.; Lobkovsky,
E.; Chirik, P. J. J. Am. Chem. Soc. 2005, 6298–6300. (j) Scott, J.;
Gambarotta, S.; Korobkov, I.; Budzelaar, P. H. M. J. Am. Chem. Soc. 2005,
13019–13029. (k) Bart, S. C.; Chlopek, K.; Bill, E.; Bouwkamp, M. W.;
Lobkovsky, E.; Neese, F.; Wieghardt, K.; Chirik, P. J. J. Am. Chem. Soc.
2006, 128, 13901–13912. (l) Ferna´ndez, I.; Trovitch, R. J.; Lobkovsky, E.;
Chirik, P. J. Organometallics 2008, 27, 109–118.

6552 Organometallics, Vol. 27, No. 24, 2008
Wallenhorst et al.
Figure 7. ESI+ MS spectrum of the free ligands obtained after CH3OH quenching of an ethylene polymerization reaction mixture at the
8b/MAO catalyst.
Scheme 6
deviating behavior. At present it is far from being clear as to
what this special catalytic behavior of the systems 8 might have
caused. Since the steric bulk of the unsaturated groups at the
imine nitrogen is practically the same as for their saturated
analogues, we are tempted to speculate that a secondary reaction
of the pendant alkenyl group during the oligomerization reaction
might have caused the observed unusual behavior. An alkenyl-
specific reaction could potentially be the involvement of the
pendant alkenyl functionality in the actual oligomerization
reaction sequence.20,21 A noninnocent behavior of the pendant
alkenyl moieties could possibly lead to a conversion of these
substituents to a much larger and much more bulky oligoeth-
ylene substituent at that imine nitrogen center, thereby poten-
tially altering the chain termination and chain transfer properties
of the catalyst during the actual olefin oligomerization process
toward the direction of polyethylene formation.
One can devise a variety of experiments to study the question
of the active involvement of the pendant alkenyl group. At this
time we have only started to investigate the potential “nonin-
nocent” behavior of an alkenyl substituent at the imine nitrogen
and carried out the following experiments: the systems 8 were
reacted with ethene (1 bar) in THF in a Schlenk flask upon
treatment with 250 equiv of MAO. After 30 min the mixture
procedure or obtained in situ by chain transfer to/from alumi-
was quenched by the addition of methanol. This procedure
num) could account for the (MH+ + 14) series.
destroyed the Fe complexes and liberated the free ligands. These
The formation of possible structures (14-H+, 15-H+) can be
were then analyzed by ESI MS.22 In the case of the reaction of
formulated using the ”rules” of R-olefin insertion at the
8b (R ) n-butenyl) we recorded the mass spectrum depicted in
bis(iminoalkyl)pyridine iron catalysts as they were deduced by
Figure 7.
Brookhart et al.23 (see Scheme 6; a detailed scheme is provided
In this ESI+ MS spectrum (see Figure 7) we observe the
with the Supporting Information).20,24
protonated ligand system 5b + H+ (MH+: m/z 376) and the
corresponding 5b + Na+ (MNa+: m/z 398) feature. Then we
Some Conclusions
monitor two systematic series of signals. The first begins at m/z
432 (MH+ + 56) (i.e., ligand plus two ethene units). We see a
The cobalt and iron chelate complexes 7 and 8 are readily
sequence of signals derived from this by the addition of the
third ethene monomer (gives m/z 460), the fourth (m/z 488),
and so forth. It is conceivable that this series of compounds
(14-H+) might be derived from the involvement of the pendent
olefinic unit at the active catalyst stage in the polymerization
process.
The second systematic series of features in the ESI+ MS
spectrum of this specific experiment is offset from the signals
of the first by 14 mass units. A competing sequence starting,
for example, from 13 (either generated in the initial activation
obtained by treatment of the neutral ligand systems 5 with CoCl2
and FeCl2, respectively. The structures of these paramagnetic
complexes are rather unexceptional. Both series (Co and Fe)
feature typical strongly distorted square pyramidal/trigonal
(23) Small, B. L.; Brookhart, M. Macromolecules 1999, 32, 2120–2130.
(24) There is principally the possibility of ligand methylation by, for
example, trimethylaluminum in such systems; see, e.g.: (a) Bruce, M.;
Gibson, V. C.; Redshaw, C.; Solan, G. A.; White, A. J. P.; Williams, D. J.
Chem. Commun. 1998, 2523–2524. (b) Knijnenburg, Q.; Smits, J. M. M.;
Budzelaar, P. H. M. Organometallics 2006, 25, 1036–1046. See also: (c)
Clentsmith, G. K. B.; Gibson, V. C.; Hitchcock, P. B.; Kimberley, B. S.;
Rees, C. W. Chem. Commun. 2002, 1498–1499. (d) Sugiyama, H.;
Aharonian, G.; Gambarotta, S.; Yap, G. P. A.; Budzelaar, P. H. M. J. Am.
Chem. Soc. 2002, 124, 12268–12274. (e) Tsurugi, H.; Matsuo, A.;
Yamagata, T.; Mashima, K. Organometallics 2004, 23, 2797–2805. (f)
Sugiyama, H.; Gambarotta, S.; Yap, G. P. A.; Wilson, D. R.; Thiele, S. K.-
H. Organometallics 2004, 23, 5053–5061. (g) Blackmore, I. J.; Gibson,
V. C.; Hitchcock, P. B.; Rees, C. W.; Williams, D. J.; White, A. J. P. J. Am.
Chem. Soc. 2005, 6012–6020.
(21) The oligomers feature vinyl groups in their 13C NMR spectra.
Therefore, we assume that chain transfer to aluminum probably has not
played a dominating role in these experiments.
(22) For some remotely related MS studies of active Ziegler-Natta
catalyst systems: (a) Chen, P. Angew. Chem. 2003, 115, 2938-2954; Angew.
Chem., Int. Ed. 2003, 42, 2832-2847. (b) Di Lena, F.; Quintanilla, E.;
Chen, P. Chem. Commun. 2005, 5757–5759, and references cited therein.

Bis(iminoethyl)pyridine Systems
Organometallics, Vol. 27, No. 24, 2008 6553
used: data collection EXPRESS (Nonius BV, 1994) and COLLECT
(Nonius BV, 1998), data reduction MolEN (K. Fair, Enraf-Nonius
BV, 1990) and Denzo-SMN (Otwinowski, Z.; Minor, W.Methods
Enzymol. 1997, 276, 307-326), absorption correction for CCD data
SORTAV (Blessing, R. H. Acta Crystallogr. 1995, A51, 33-37;
Blessing, R. H. J. Appl. Crystallogr. 1997, 30, 421-426) and Denzo
(Otwinowski, Z.; Borek, D; Majewski, W.; Minor, W. Acta
Crystallogr. 2003, A59, 228-234), structure solution SHELXS-97
(Sheldrick, G. M. Acta Crystallogr. 1990, A46, 467-473), structure
refinement SHELXL-97 (Sheldrick, G. M. Acta Crystallogr. 2008,
A64, 112-122), graphics XP (BrukerAXS, 2000).
bipyramidal geometries. The pendant alkenyl substituents do
not show any direct interaction with the metal at the [M]Cl2
complex state. Also, the formation of the cobalt(I) methyl
complex 11a is typical. Several other examples of this reaction
type were previously described in the literature.14,15 These
apparently quite normal and unexceptional systems behave rather
exceptionally at their active homogeneous Ziegler-Natta cata-
lyst stage. For both series we would have expected just ethylene
oligomer formation,5 but not polyethylene production, if the
pendant olefinic group at the ligand framework would have been
just a nonparticipating bystander. We would have expected a
catalyst behavior similar to that of the related previously
described “Bianchini systems” (2 and its congeners).5 In
contrast, we observe polyethylene formation to take place at
most of the N-alkenyl chelate cobalt complexes 7/MAO and a
very interesting competition between polyethylene and oligo-
ethylene product formation at the 8/MAO-derived catalyst
systems. In these cases the molecular weight and the molecular
weight distribution of the oligoethylene product fraction are
similar to those for the oligomers described as being formed at
the reference systems (2/MAO, 10b/MAO). This indicates that
the olefinic substituents attached at the imine nitrogen atoms
of our new ligand systems are not inertsthey seem to be
“noninnocent” substituents that show a tendency of becoming
involved in the oligomerization process and thereby of control-
ling it. The very nature of this interaction and involvement is,
however, not completely clear at this time. One might envisage
that the vinyl end group might, for example, just reversibly
coordinate to the metal center at the active catalyst stage and
thereby alter the chain termination and transfer probabilities and
behavior. In view of our 8b/MAO experiment and the corre-
sponding ESI+ MS analysis (see Figure 7 and the text) there
might be a good chance that the vinyl end group of the ligand
substituent can actually actively take part in the polymerization
process as an internal comonomer20,22 and thereby alter the
overall features of the catalyst during the oligomerization/
polymerization process. In either case it seems that the pendant
alkenyl moieties at the chelate ligand framework of these
interesting new complex systems are able to exert an internal
dynamic control on the characteristic chemical features of these
active olefin oligomerization and polymerization catalysts.
General Procedure for the Preparation of the Unsymmetrical
Ligand Systems 5a-d and 6b. In a flame-dried Schlenk flask a
mixture of compound 3 in methanol and the appropriate alkeny-
lamine was heated at 60 °C under stirring for 20 h. The hot yellow
solution was filtered under an argon atmosphere to remove the
insoluble symmetrical side product 2,6-bis(N-(2,6-diisopropylphe-
nyl)iminoethyl)pyridine. After half of the solvent was removed,
the resulting solution was kept at 0 °C for 24 h. The desired product
precipitated as yellow crystals, which were separated by filtration.
A second crop of product was obtained from the mother liquor
after reducing the solvent volume and cooling to 0 °C for 24 h. In
the solid state the ligand systems are air-stable; to protect them
against moisture they were stored in a glovebox.
Preparation of Ligand 5a. A sample of 3 (3.47 g, 10.8 mmol)
in 50 mL of methanol was treated with allylamine (4a; 8.08 mL,
6.14 g, 107.6 mmol, 10 equiv) to yield a light yellow solid (79%,
3.10 g, 8.60 mmol). Mp (DSC): 111 °C. MS-ESI (MeOH, ES+):
m/z 384.2 (M + Na]+), 362.2 ([M + H]+). Anal. Calcd for C24H31N3
(361.52): C, 79.73; H, 8.64; N, 11.62. Found: C, 79.71; H, 8.61;
N, 11.57. 1H NMR (d2-dichloromethane, 600 MHz, 298 K): δ(1H)
8.37 (dd, 3J ) 7.8 Hz, 4J ) 1.0 Hz, 1H, 3-Hpy), 8.25 (dd, 3J ) 7.8
Hz, 4J ) 1.0 Hz, 1H, 5-Hpy), 7.84 (t, 3J ) 7.8 Hz, 1H, 4-Hpy), 7.16
(m, 2H, 3-Haryl), 7.08 (m, 1H, 4-Haryl), 6.16 (ddt, 3J ) 17.3 Hz, 3J
3
3
4
) 10.3 Hz, J ) 5.2 Hz, 1H, -CHd), 5.32 (dq, J ) 17.3 Hz, J
) 2J ) 1.8 Hz, 1H, dCH2 ), 5.17 (dq, 3J ) 10.3 Hz, 4J ) 2J ) 1.8
Z
E
3
Hz, 1H, dCH2 ), 4.23 (m, 2H, dNCH2-), 2.75 (sept, J ) 6.9
Hz, 2H, -CH(CH3)2), 2.42 (s, 3H, -CH3alkyl), 2.23 (s, 3H,
3
B
-CH3aryl), 1.15 (d, J ) 6.9 Hz, 6H, -CH(CH3ACH3 )), 1.13 (d,
3J ) 6.9 Hz, 6H, -CH(CH3ACH3 )). 13C{1H} NMR (d2-dichlo-
B
romethane, 150 MHz, 298 K): δ(13C) 167.5 (NdCaryl), 167.4
(NdCalkyl), 156.8 (C-6py), 155.2 (C-2py), 147.0 (C-1aryl), 137.0 (C-
4py), 136.7 (-CHd), 136.2 (C-2aryl), 123.8 (C-4aryl), 123.3 (C-3aryl),
122.1 (C-5py), 121.8 (C-3py), 115.1 (dCH2), 55.2 (dNCH2-), 28.6
(-CH(CH3)2), 23.3 (-CH(CH3ACH3 ), 22.9 (-CH(CH3ACH3 )),
B
B
Experimental Section
17.3 (-CH3aryl), 13.8 (-CH3alkyl).
General Procedures. Reactions with air- and water-sensitive
compounds were carried out under argon using Schlenk-type
glassware or in a glovebox. Solid compounds were collected on
sintered-glass frits and washed with appropriate solvents before
being dried under vacuum. Solvents were dried and distilled under
argon prior to use. Compound 35 and the alkenylamines 4b-d8
were prepared analogously as described in the literature. 2,6-
Diacetylpyridine, 2,6-diisopropylaniline, and allylamine 4a were
used as purchased from commercial suppliers. The following
instruments were used for physical characterization of the com-
pounds. Melting points: DSC 2010 TA instruments. Elemental
analyses: Foss-Heraeus CHNO-Rapid. ESI-MS analysis: Quattro
LCZ (Waters Micromass, Manchester, U.K.) equipped with a nano
spray inlet. IR: FT-IR spectrometer Excalibur 3100 (Varian)
equipped with a Specac Golden Gate ATR MK II unit. NMR:
Bruker AC 200 P (1H, 200.1 MHz; 13C, 50.3 MHz), AMX 400
(1H, 400.1 MHz; 13C, 100.6 MHz), Varian UNITY plus NMR
spectrometer (1H, 599.1 MHz; 13C, 150.7 MHz). Assignments of
the resonances were supported by 2D experiments.
X-ray crystal structure analysis of 5a: formula C24H31N3, Mr )
361.52, light yellow crystal, 0.25 × 0.10 × 0.05 mm, a ) 8.420(3)
Å, b ) 11.852(1) Å, c ) 12.291(2) Å, R ) 109.84(1)°, ꢀ )
108.27(2)°, γ ) 90.96(2)°, V ) 1085.1(4) Å3, Fcalcd ) 1.106 g cm-3
,
µ) 0.497 mm-1, empirical absorption correction (0.886 e T e
j
0.976), Z ) 2, triclinic, space group P1 (No. 2), λ ) 1.541 78 Å,
T ) 223 K, ω/2θ scans, 4738 reflections collected ((h, ( k, ( l),
(sin θ)/λ ) 0.62 Å-1, 4424 independent (Rint ) 0.063) and 2504
observed reflections (I g 2σ(I)), 251 refined parameters, R1 )
0.056, wR2 ) 0.162, maximum (minimum) residual electron density
0.22 (-0.21) e Å-3, hydrogen atoms calculated and refined as riding
atoms.
Preparation of Ligand 5b. A sample of 3 (10.0 g, 31.0 mmol)
in 150 mL of methanol was treated with 3-butenylamine (4b; 4.30
mL, 3.31 g, 46.5 mmol, 1.5 equiv) to yield a yellow solid (78%,
9.10 g, 24.2 mmol). Mp (DSC): 100 °C. MS-ESI (MeOH, ES+):
m/z 398.3 ([M + Na]+), 376.3 ([M + H]+). Anal. Calcd for
C25H33N3 (375.55): C, 79.95; H, 8.86; N, 11.19. Found: C, 79.83;
1
X-ray Crystal Structure Analyses. Data sets were collected
with Enraf-Nonius CAD4 and Nonius KappaCCD diffractometers,
in case of Mo radiation with a rotating anode generator. Programs
H, 8.73; N, 11.03. H NMR (d2-dichloromethane, 600 MHz, 298
3
4
K): δ(1H) 8.35 (dd, J ) 7.9 Hz, J ) 1.0 Hz, 1H, 3-Hpy), 8.20
(dd, J ) 7.9 Hz, J ) 1.0 Hz, 1H, 5-Hpy), 7.83 (t, J ) 7.9 Hz,
3
4
3

6554 Organometallics, Vol. 27, No. 24, 2008
Wallenhorst et al.
1H, 4-Hpy), 7.16 (m, 2H, 3-Haryl), 7.08 (m, 1H, 4-Haryl), 5.99 (ddt,
m/z 426.3 ([M + Na]+), 404.3 ([M + H]+). Anal. Calcd for
3J ) 17.2 Hz, 3J ) 10.3 Hz, 3J ) 6.8 Hz, 1H, -CHd), 5.15 (ddt,3J
C27H37N3 (403.60): C, 80.35; H, 9.24; N, 10.41. Found: C, 80.24;
2
4
Z
3
1
) 17.2 Hz, J ) 2.0 Hz, J ) 1.6 Hz, 2H, dCH2 ), 5.05 (ddt, J
H, 9.19; N, 10.35. H NMR (d2-dichloromethane, 600 MHz, 298
2
4
E
3
3
3
K): δ(1H) 8.37 (d, J ) 7.6 Hz, 1H, 3-Hpy), 8.22 (d, J ) 7.6 Hz,
1H, 5-Hpy), 7.84 (t, 3J ) 7.6 Hz, 1H, 4-Hpy), 7.18 (m, 2H, 3-Haryl),
7.09 (m, 1H, 4-Haryl), 5.90 (ddt, 3J ) 17.3 Hz, 3J ) 10.1 Hz, 3J )
) 10.3 Hz, J ) 2.0 Hz, J ) 1.2 Hz, 1H, dCH2 ), 3.62 (d, J )
7.2 Hz, 1H, dNCH2-), 2.75 (sept, 3J ) 6.9 Hz, 2H, -CH(CH3)2),
2.53 (m, 2H, dNCH2CH2-), 2.41 (t, 5J ) 0.7 Hz, 3H, -CH3alkyl),
2.24 (s, 3H, -CH3aryl), 1.15 (d, 3J ) 6.9 Hz, 6H, -CH(CH3 CH3 )),
A
B
6.8 Hz, 1H, -CHd), 5.06 (d, 3J ) 17.3 Hz, 1H, dCH2 ), 4.98 (d,
Z
1.13 (d, J ) 6.9 Hz, 6H, -CH(CH3ACH3 )). 13C{1H} NMR (d2-
dichloromethane, 150 MHz, 298 K): δ(13C) 167.5 (NdCaryl), 166.6
(NdCalkyl), 156.9 (C-6py), 155.1 (C-2py), 147.0 (C-1aryl), 137.6
(-CHd), 136.9 (C-4py), 136.2 (C-2aryl), 123.8 (C-4aryl), 123.3 (C-
3aryl), 122.0 (C-5py), 121.6 (C-3py), 115.7 (dCH2), 52.4 (dNCH2-),
3
B
3J ) 10.1 Hz, 1H, dCH2 ), 3.57 (t, J ) 7.3 Hz, 2H, dNCH2-),
2.77 (sept, 3J ) 7.0 Hz, 2H, -CH(CH3)2), 2.43 (s, 3H, -CH3alkyl),
E
3
2.26 (s, 3H, -CH3aryl), 2.17 (q, 3J
dNCH2CH2CH2CH2-), 1.80 (quint, 3J
)
)
7.3 Hz, 2H,
7.3 Hz, 2H,
dNCH2CH2-), 1.59 (quint, 3J ) 7.3 Hz, 2H, dNCH2CH2CH2-),
35.6 (dNCH2CH2-), 28.6 (CH(CH3)2), 23.3 (-CH(CH3ACH3 )),
B
1.17 (d, 3J ) 7.0 Hz, 6H, -CH(CH3ACH3 )), 1.15 (d, 3J ) 7.0 Hz,
B
22.9 (-CH(CH3ACH3 )), 17.3 (-CH3aryl), 13.8 (-CH3alkyl).
B
6H, -CH(CH3ACH3 )). 13C{1H} NMR (d2-dichloromethane, 150
B
MHz, 298 K): δ(13C) 167.5 (NdCaryl), 166.2 (NdCalkyl), 157.1 (C-
6py), 155.2 (C-2py), 147.0 (C-1aryl), 139.5 (-CHd), 136.9 (C-4py),
136.2 (C-2aryl), 123.9 (C-4aryl), 123.3 (C-3aryl), 122.0 (C-5py), 121.6
X-ray crystal structure analysis of 5b: formula C25H33N3, Mr )
375.54, light yellow crystal, 0.40 × 0.20 × 0.10 mm, a ) 8.459(1)
Å, b ) 11.490(1) Å, c ) 12.480(1) Å, R ) 100.34(1)°, ꢀ )
(C-3py),
114.5
(dCH2),
52.7
(dNCH2-),
34.1
107.97(1)°, γ ) 95.02(1)°, V ) 1121.8(2) Å3, Fcalcd ) 1.112 g cm-3
,
µ ) 0.497 mm-1, empirical absorption correction (0.826 e T e
(dNCH2CH2CH2CH2-), 30.8 (dNCH2CH2-), 28.6 (-CH(CH3)2),
B
0.952), Z ) 2, triclinic, space group P1 (No. 2), λ ) 1.541 78 Å,
27.4 (dNCH2CH2CH2-), 23.4 (-CH(CH3ACH3 )), 23.0
j
B
(-CH(CH3ACH3 )), 17.3 (-CH3aryl), 13.7 (-CH3alkyl).
T ) 223 K, ω and ꢁ scans, 14 463 reflections collected ((h, ( k,
( l), (sin θ)/λ ) 0.60 Å-1, 3834 independent (Rint ) 0.032) and
3499 observed reflections (I g 2σ(I)), 259 refined parameters, R1
) 0.051, wR2 ) 0.142, maximum (minimum) residual electron
density 0.20 (-0.16) e Å-3, hydrogen atoms calculated and refined
as riding atoms.
Preparation of Ligand 6b. A sample of 3 (1.00 g, 3.10 mmol)
in 60 mL of methanol was treated with n-butylamine (3.06 mL,
2.27 g, 31.0 mmol, 10 equiv) to yield a light yellow solid (90%,
1.05 g, 2.78 mmol). Mp (DSC): 93 °C. MS-ESI (MeOH, ES+):
m/z 400.3 ([M + Na]+), 378.3 ([M + H]+). Anal. Calcd for
C25H35N3 (377.57): C, 79.53; H, 9.34; N, 11.13. Found: C, 79.34;
Preparation of Ligand 5c. A sample of 3 (2.40 g, 7.44 mmol)
in 60 mL of methanol was treated with 4-pentenylamine (4c; 2.47
mL, 1.90 g, 22.3 mmol, 3 equiv) to yield a yellow solid (81%,
2.35 g, 6.03 mmol). Mp (DSC): 85 °C. MS-ESI (MeOH, ES+):
m/z 412.3 ([M + Na]+), 390.3 ([M + H]+). Anal. Calcd for
C26H35N3 (389.58): C, 80.16; H, 9.06; N, 10.79. Found: C, 79.91;
1
H, 9.32; N, 10.94. H NMR (d2-dichloromethane, 600 MHz, 298
3
3
K): δ(1H) 8.34 (d, J ) 7.8 Hz, 1H, 3-Hpy), 8.20 (d, J ) 7.8 Hz,
1H, 5-Hpy), 7.83 (t, 3J ) 7.8 Hz, 1H, 4-Hpy), 7.16 (m, 2H, 3-Haryl),
7.08 (m, 1H, 4-Haryl), 3.55 (t, J ) 7.4 Hz, 2H, dNCH2-), 2.75
3
(sept, 3J ) 6.9 Hz, 2H, -CH(CH3)2), 2.41 (s, 3H, -CH3alkyl), 2.24
1
3
(s, 3H, -CH3aryl), 1.74 (quint, J ) 7.4 Hz, 2H, dNCH2CH2-),
H, 9.02; N, 10.67. H NMR (d2-dichloromethane, 500 MHz, 298
3
4
K): δ(1H) 8.36 (dd, J ) 7.9 Hz, J ) 1.0 Hz, 1H, 3-Hpy), 8.22
1.49 (sext, 3J ) 7.4 Hz, 2H, dNCH2CH2CH2-), 1.15 (d, 3J ) 6.9
(dd, J ) 7.9 Hz, J ) 1.0 Hz, 1H, 5-Hpy), 7.84 (t, J ) 7.9 Hz,
1H, 4-Hpy), 7.17 (m, 2H, 3-Haryl), 7.08 (m, 1H, 4-Haryl), 5.93 (ddt,
3J ) 17.2 Hz, 3J ) 10.3 Hz, 3J ) 6.7 Hz, 1H, -CHd), 5.08 (ddt,
3
4
3
Hz, 6H, -CH(CH3ACH3 ), 1.13 (d, 3J
) 6.9 Hz, 6H,
B
-CH(CH3 CH3 ), 0.99 (t, 3J ) 7.4 Hz, 3H, -CH3). 13C{1H} NMR
(d2-dichloromethane, 150 MHz, 298 K): δ(13C) 167.6 (NdCaryl),
166.1 (NdCalkyl), 157.1 (C-6py), 155.1 (C-2py), 147.0 (C-1aryl), 136.9
(C-4py), 136.2 (C-2aryl), 123.8 (C-4aryl), 123.3 (C-3aryl), 122.0 (C-
5py), 121.5 (C-3py), 52.6 (dNCH2-), 33.5 (dNCH2CH2-), 28.6
A
B
3J ) 17.2 Hz, J ) 2.1 Hz, J ) 1.6 Hz, 1H, dCH2 ), 5.00 (ddt,
2
4
Z
3J ) 10.3 Hz, J ) 2.1 Hz, J ) 1.2 Hz, 1H, dCH2 ), 3.56 (t, J
2
4
E
3
) 7.2 Hz, 2H, dNCH2-), 2.78 (sept, 3J ) 7.0 Hz, 2H,
5
-CH(CH3)2), 2.41 (t, J ) 0.8 Hz, 3H, -CH3alkyl), 2.25 (s, 3H,
A
B
A
B
(-CH(CH3)2), 23.3 (-CH(CH3 CH3 ), 22.9 (-CH(CH3 CH3 ), 21.2
(dNCH2CH2CH2-), 17.3 (-CH3aryl), 14.2 (-CH3), 13.6
(-CH3alkyl).
3
-CH3aryl), 2.24 (m, 2H, dNCH2CH2CH2-), 1.88 (quint, J ) 7.2
Hz, 2H, dNCH2CH2-), 1.16 (d, 3J
) 7.0 Hz, 6H,
B
3
B
-CH(CH3ACH3 )), 1.14 (d, J ) 7.0 Hz, 6H, -CH(CH3ACH3 )).
13C{1H} NMR (d2-dichloromethane, 125 MHz, 298 K): δ(13C) 167.5
(NdCaryl), 166.3 (NdCalkyl), 157.1 (C-6py), 155.2 (C-2py), 147.0 (C-
1aryl), 139.2 (-CHd), 136.9 (C-4py), 136.2 (C-2aryl), 123.8 (C-4aryl),
123.3 (C-3aryl), 122.0 (C-5py), 121.6 (C-3py), 114.7 (dCH2), 52.1
(dNCH2-), 32.2 (dNCH2CH2CH2-), 30.6 (dNCH2CH2-), 28.6
X-ray crystal structure analysis of 6b: formula C25H35N3, Mr )
377.56, colorless crystal, 0.40 × 0.30 × 0.30 mm, a ) 12.387(1)
Å, b ) 16.007(1) Å, c ) 12.911(1) Å, ꢀ ) 115.16(1)°, V )
2317.1(3) Å3, Fcalcd ) 1.082 g cm-3, µ ) 0.064 mm-1, empirical
absorption correction (0.975 e T e 0.981), Z ) 4, monoclinic,
space group P21/n (No. 14), λ ) 0.710 73 Å, T ) 198 K, ω and ꢁ
scans, 16 813 reflections collected ((h, ( k, ( l), (sin θ)/λ ) 0.67
Å-1, 5554 independent (Rint ) 0.051) and 3258 observed reflections
(I g 2σ(I)), 260 refined parameters, R1 ) 0.065, wR2 ) 0.184,
(-CH(CH3)2), 23.4 (-CH(CH3ACH3 )), 23.0 (-CH(CH3ACH3 )),
B
B
17.3 (-CH3aryl), 13.7 (-CH3alkyl).
X-ray crystal structure analysis of 5c: formula C26H35N3, Mr )
389.57, colorless crystal, 0.30 × 0.15 × 0.10 mm, a ) 9.247(1)
Å, b ) 20.691(1) Å, c ) 12.481(1) Å, ꢀ ) 94.74(1)°, V ) 2379.8(3)
Å3, Fcalcd ) 1.087 g cm-3, µ ) 0.484 mm-1, empirical absorption
correction (0.868 e T e 0.953), Z ) 4, monoclinic, space group
P21/c (No. 14), λ ) 1.541 78 Å, T ) 223 K, ω and ꢁ scans, 16 747
reflections collected ((h, ( k, ( l), (sin θ)/λ ) 0.60 Å-1, 4225
independent (Rint ) 0.045) and 3369 observed reflections (I g
2σ(I)), 296 refined parameters, R1 ) 0.054, wR2 ) 0.151, group
C26-C29 refined with split positions, maximum (minimum)
residual electron density 0.37 (-0.22) e Å-3, hydrogen atoms
calculated and refined as riding atoms.
maximum (minimum) residual electron density 0.36 (-0.23) e Å-3
hydrogen atoms calculated and refined as riding atoms.
,
General Procedure for the Preparation of the Metal
Complexes 7a-d, 8a-d, 9b, and 10b. A flame-dried Schlenk flask
was charged under argon with the metal halide and n-butanol. To
another Schlenk flask were added the corresponding Schiff base
ligand (1.1 equiv) and n-butanol under inert conditions. Both
Schlenk flasks were heated to 80 °C for 1 h, and then the ligand
solution was transferred to the reaction vessel under argon, which
contained the dissolved metal halide. The reaction mixture was
heated further for 1 h and then stirred for 12 h at room temperature.
Subsequently the volume of the solvent was reduced in vacuo. The
precipitation was completed by addition of pentane (80 mL), and
the solid was collected by filtration, washed with pentane until the
Preparation of Ligand 5d. A sample of 3 (1.00 g, 3.10 mmol)
in 60 mL of methanol was treated with 5-hexenylamine (4d; 1.70
mL, 1.23 g, 12.4 mmol, 4 equiv) to yield a deep yellow solid (60%,
0.75 g, 1.86 mmol). Mp (DSC): 60 °C. MS-ESI (MeOH, ES+):

Bis(iminoethyl)pyridine Systems
Organometallics, Vol. 27, No. 24, 2008 6555
solvent was colorless, and dried in vacuo to give green solids in
the case of the cobalt complexes 7a-d and blue solids in the case
of the iron complexes 8a-d.
Preparation of Complex 7d. A sample of ligand 5d (500
mg, 1.24 mmol) was treated with cobalt(II) chloride (160 mg, 1.23
mmol) in 40 mL of n-butanol to yield the green product (82%,
538 mg, 1.01 mmol). Slow crystallization from a saturated
dichloromethane solution gave single crystals of 7d for the crystal
structure analysis. Mp (DSC): 301 °C. MS-ESI (CH3CN, ES+): m/z
497.5 ([M - Cl]+). Anal. Calcd for C27H37Cl2CoN3 (533.44): C,
60.79; H, 6.99; N, 7.88. Found: C, 60.58; H, 7.00; N, 7.77. IR
(ATR): ν˜ (cm-1) 2962, 2929, 2867, 1624, 1582, 1462, 1441, 1364,
1318, 1262, 1203, 1179, 1102, 996, 908, 816, 806, 773, 744, 696,
641.
Preparation of Complex 7a. A sample of ligand 5a (1.10 g,
3.05 mmol) was treated with cobalt(II) chloride (0.36 g, 2.77 mmol)
in 40 mL of n-butanol to yield the green product (96%, 1.31 g,
2.67 mmol). Slow crystallization from a saturated dichloromethane
solution gave single crystals of 7a for the crystal structure analysis.
Mp (DSC): 260 °C. MS-ESI (CH3CN, ES+): m/z 455.2 ([M - Cl]+).
Anal. Calcd for C24H31Cl2CoN3 (491.36): C, 58.66; H, 6.36; N,
8.55. Found: C, 58.67; H, 6.34; N, 8.25. IR (ATR): ν˜ (cm-1) 2962,
2925, 2868, 1623, 1581, 1463, 1379, 1370, 1319, 1268, 1246, 1203,
1059, 1027, 981, 912, 773, 744, 703, 607, 546.
X-ray crystal structure analysis of 7d: formula C27H37Cl2CoN3,
Mr ) 533.43, yellow crystal, 0.45 × 0.10 × 0.03 mm, a )
9.5883(3) Å, b ) 12.9838(2) Å, c ) 10.8393(4) Å, ꢀ ) 92.006(2)°,
X-ray crystal structure analysis of 7a: formula C24H31Cl2CoN3,
Mr ) 491.35, yellow crystal, 0.40 × 0.20 × 0.05 mm, a )
17.433(1) Å, b ) 9.802(1) Å, c ) 15.579(1) Å, ꢀ ) 115.26(1)°, V
) 2407.6(3) Å3, Fcalcd ) 1.356 g cm-3, µ ) 0.950 mm-1, empirical
absorption correction (0.702 e T e 0.954), Z ) 4, monoclinic,
space group P21/c (No. 14), λ ) 0.710 73 Å, T ) 198 K, ω and ꢁ
scans, 14 065 reflections collected ((h, ( k, ( l), (sin θ)/λ ) 0.67
Å-1, 5827 independent (Rint ) 0.057) and 4689 observed reflections
(I g 2σ(I)), 278 refined parameters, R1 ) 0.082, wR2 ) 0.216,
maximum (minimum) residual electron density 3.22 (-0.86) e Å-3
close to Co and Cl, hydrogen atoms calculated and refined as riding
atoms, due to crystal twinning the analysis is of poor quality.
Preparation of Complex 7b. A sample of ligand 5b (337 mg,
0.90 mmol) was treated with cobalt(II) chloride (106 mg, 0.82
mmol) in 20 mL of n-butanol to yield the green product (99%,
409 mg, 0.81 mmol). Slow crystallization from a saturated
dichloromethane solution gave single crystals of 7b for the crystal
structure analysis. Mp (DSC): 288 °C. MS-ESI (CH3CN, ES+): m/z
469.4 ([M - Cl]+). Anal. Calcd for C25H33Cl2CoN3 (505.39): C,
59.41; H, 6.58; N, 8.31. Found: C, 59.27; H, 6.65; N, 8.13. IR
(ATR): ν˜ (cm-1) 2963, 2923, 2871, 1587, 1467, 1370, 1264, 1203,
1105, 1010, 918, 810, 773, 741, 634, 545.
V ) 1348.59(7) Å3, Fcalcd ) 1.314 g cm-3, µ ) 0.854 mm-1
,
empirical absorption correction (0.700 e T e 0.975), Z ) 2,
monoclinic, space group P21 (No. 4), λ ) 0.710 73 Å, T ) 198 K,
ω and ꢁ scans, 9205 reflections collected ((h, ( k, ( l), (sin θ)/λ
) 0.66 Å-1, 5774 independent (Rint ) 0.057) and 4552 observed
reflections (I g 2σ(I)), 323 refined parameters, R1 ) 0.051, wR2
) 0.103, Flack parameter -0.02(2), group C29 to C30 refined with
split positions, maximum (minimum) residual electron density 0.36
(-0.51) e Å-3, hydrogen atoms calculated and refined as riding
atoms.
Preparation of Complex 8a. A sample of ligand 5a (1.07 g,
2.95 mmol) was treated with iron(II) chloride (340 mg, 2.68 mmol)
in 75 mL of n-butanol to yield the blue product (98%, 1.28 g, 2.62
mmol). Mp (DSC): 267 °C. MS-ESI (CH3CN, ES+): m/z 511.2 ([M
+ Na]+), 452.2 ([M - Cl]+). Anal. Calcd for C24H31Cl2FeN3
(488.27): C, 60.79; H, 6.99; N, 7.88. Found: C, 60.58; H, 7.00; N,
7.77. IR (ATR): ν˜ (cm-1) 2963, 2926, 2868, 1581, 1461, 1444,
1370, 1323, 1272, 1247, 1203, 1179, 1104, 1059, 981, 912, 812,
773, 740.
Preparation of Complex 8b. A sample of ligand 5b (250 mg,
0.67 mmol) was treated with iron(II) chloride (77.3 mg, 0.61 mmol)
in 40 mL of n-butanol to yield the blue product (97%, 295 mg,
0.59 mmol). Mp (DSC): 292 °C. MS-ESI (CH3CN, ES+): m/z 466.4
([M - Cl]+). Anal. Calcd for C25H33Cl2FeN3 (502.30): C, 59.78;
H, 6.62; N, 8.37. Found: C, 59.74; H, 6.65; N, 8.25. IR (ATR): ν˜
(cm-1) 2962, 2923, 2870, 1585, 1466, 1445, 1370, 1329, 1268,
1202, 1179, 1105, 1008, 918, 810, 773, 738, 673.
X-ray crystal structure analysis of 7b: formula C25H33Cl2CoN3,
Mr ) 505.37, yellow crystal, 0.35 × 0.10 × 0.03 mm, a )
17.509(1) Å, b ) 9.837(1) Å, c ) 15.598(1) Å, ꢀ ) 114.40(1)°, V
) 2446.6(3) Å3, Fcalcd ) 1.372 g cm-3, µ ) 0.937 mm-1, empirical
absorption correction (0.735 e T e 0.972), Z ) 4, monoclinic,
space group P21/c (No. 14), λ ) 0.710 73 Å, T ) 198 K, ω and ꢁ
scans, 14 485 reflections collected ((h, ( k, ( l), (sin θ)/λ ) 0.67
Å-1, 5853 independent (Rint ) 0.048) and 4213 observed reflections
(I g 2σ(I)), 286 refined parameters, R1 ) 0.042, wR2 ) 0.080,
X-ray crystal structure analysis of 8b: formula C25H33Cl2FeN3,
Mr ) 502.29, blue crystal, 0.30 × 0.15 × 0.02 mm, a ) 17.316(5)
Å, b ) 9.809(4) Å, c ) 15.391(3) Å, ꢀ ) 114.315(9)°, V )
2382.3(13) Å3, Fcalcd ) 1.400 g cm-3, µ ) 0.875 mm-1, empirical
absorption correction (0.779 e T e 0.983), Z ) 4, monoclinic,
space group P21/c (No. 14), λ ) 0.710 73 Å, T ) 198 K, ω and ꢁ
scans, 6713 reflections collected ((h, ( k, ( l), (sin θ)/λ ) 0.60
Å-1, 3924 independent (Rint ) 0.073) and 2351 observed reflections
(I g 2σ(I)), 286 refined parameters, R1 ) 0.090, wR2 ) 0.250,
maximum (minimum) residual electron density 0.33 (-0.41) e Å-3
hydrogen atoms calculated and refined as riding atoms.
,
Preparation of Complex 7c. A sample of ligand 5c (300 mg,
0.77 mmol) was treated with cobalt(II) chloride (90.9 mg, 0.70
mmol) in 20 mL of n-butanol to yield the green product (96%,
350 mg, 0.67 mmol). Slow crystallization from a saturated
dichloromethane solution gave single crystals of 7c for the crystal
structure analysis. Mp (DSC): 308 °C. Anal. Calcd for
C26H35Cl2CoN3 (519.42): C, 60.12; H, 6.79; N, 8.09; Found: C,
60.03; H, 6.81; N, 7.96. IR (ATR): ν˜ (cm-1) 2961, 2928, 2866,
1583, 1461, 1441, 1364, 1259, 1203, 1103, 1057, 1203, 1103, 1057,
1025, 996, 925, 817, 773, 745, 653.
maximum (minimum) residual electron density 0.53 (-0.89) e Å-3
,
hydrogen atoms calculated and refined as riding atoms, due to
crystal quality the analysis is of poor quality.
Preparation of Complex 8c. A sample of ligand 5c (500 mg,
1.28 mmol) was treated with iron(II) chloride (148 mg, 1.17 mmol)
in 40 mL of n-butanol to yield the blue product (83%, 500 mg,
0.97 mmol). Crystals suitable for X-ray diffraction were obtained
from a warm concentrated solution of 8c in tetrahydrofuran by
slowly cooling to room temperature. Mp (DSC): 299 °C. MS-ESI
(CH3CN, ES+): m/z 538.0 ([M + Na]+), 480.1 ([M - Cl]+). Anal.
Calcd for C26H35Cl2FeN3 (516.33): C, 60.48; H, 6.83; N, 8.14.
Found: C, 59.79; H, 6.89; N, 8.01. IR (ATR): ν˜ (cm-1) 2961, 2927,
2870, 1580, 1442, 1365, 1327, 1265, 1201, 1177, 1104, 1056, 996,
924, 804, 773, 741, 698, 656.
X-ray crystal structure analysis of 7c: formula C26H35Cl2CoN3,
Mr ) 519.40, yellow crystal, 0.50 × 0.40 × 0.03 mm, a ) 9.451(1)
Å, b ) 13.486(1) Å, c ) 10.434(1) Å, ꢀ ) 95.63(1)°, V ) 1323.5(2)
Å3, Fcalcd ) 1.303 g cm-3, µ ) 0.868 mm-1, empirical absorption
correction (0.671 e T e 0.974), Z ) 2, monoclinic, space group P21
(No. 4), λ ) 0.710 73 Å, T ) 198 K, ω and ꢁ scans, 8798 reflections
collected ((h, ( k, ( l), (sin θ)/λ ) 0.67 Å-1, 5403 independent (Rint
) 0.040) and 4798 observed reflections (I g 2σ(I)), 295 refined
parameters, R1 ) 0.039, wR2 ) 0.096, Flack parameter 0.00(2),
X-ray crystal structure analysis of 8c: formula C26H35Cl2FeN3,
Mr ) 516.32, blue crystal, 0.30 × 0.15 × 0.05 mm, a ) 9.4994(2)
Å, b ) 13.5202(4) Å, c ) 10.4090(3) Å, ꢀ ) 95.779(1)°, V )
maximum (minimum) residual electron density 0.87 (-0.34) e Å-3
hydrogen atoms calculated and refined as riding atoms.
,

6556 Organometallics, Vol. 27, No. 24, 2008
Wallenhorst et al.
1330.07(6) Å3, Fcalcd ) 1.289 g cm-3, µ ) 0.786 mm-1, empirical
absorption correction (0.798 e T e 0.962), Z ) 2, monoclinic,
space group P21 (No. 4), λ) 0.710 73 Å, T ) 198 K, ω and ꢁ
scans, 9064 reflections collected ((h, ( k, ( l), (sin θ)/λ ) 0.60
Å-1, 4230 independent (Rint ) 0.054) and 3447 observed reflections
(I g 2σ(I)), 295 refined parameters, R1 ) 0.066, wR2 ) 0.177,
Flack parameter -0.01(3), maximum (minimum) residual electron
density 0.92 (-0.68) e Å-3, hydrogen atoms calculated and refined
as riding atoms.
Preparation of Complex 8d. A sample of ligand 5d (500 mg,
1.24 mmol) was treated with iron(II) chloride (156 mg, 1.23 mmol)
in 40 mL of n-butanol to yield the blue product (60%, 393 mg,
0.74 mmol). Mp (DSC): 295 °C. MS-ESI (CH3CN, ES+): m/z 494.5
([M - Cl]+). Anal. Calcd for C27H37Cl2FeN3 (530.35): C, 61.15;
H, 7.03; N, 7.92. Found: C, 61.07; H, 7.06; N, 7.87. IR (ATR): ν˜
(cm-1) 2963, 2927, 2872, 1639, 1588, 1463, 1443, 1368, 1268,
1255, 1212, 1109, 1058, 1021, 985, 904, 817, 800, 770, 745, 698,
622.
Preparation of Complex 9b. A sample of ligand 6b (500 mg,
1.32 mmol) was treated with cobalt(II) chloride (163 mg, 1.26
mmol) in 40 mL of n-butanol to yield the green product (99%,
630 mg, 1.24 mmol). Mp (DSC): 308 °C. MS-ESI (CH3CN, ES+):
m/z 471.1 ([M - Cl]+). Anal. Calcd for C25H35Cl2CoN3 (507.40):
C, 59.18; H, 6.95; N, 8.28. Found: C, 58.62; H, 7.04; N, 8.25. IR
(ATR): ν˜ (cm-1) 2963, 2926, 2870, 1583, 1462, 1371, 1263, 1203,
1179, 1104, 1059, 1027, 939, 811, 775, 743, 696, 632.
Preparation of Complex 10b. A sample of ligand 6b (500 mg,
1.32 mmol) was treated with iron(II) chloride (157 mg, 1.24 mmol)
in 40 mL of n-butanol to yield the blue product (99%, 625 mg,
1.24 mmol). Mp (DSC): 307 °C. MS-ESI (CH3CN, ES+): m/z 468.3
([M - Cl]+). Anal. Calcd for C25H35Cl2FeN3 (504.32): C, 59.54;
H, 7.00; N, 8.33. Found: C, 58.96; H, 6.99; N, 8.21. IR (ATR): ν˜
(cm-1) 2962, 2927, 2870, 1582, 1460, 1444, 1371, 1326, 1266,
1202, 1179, 1104, 1058, 1024, 939, 812, 772, 741, 699.
(-CH(CH3)2), 25.5 (-CH3aryl), 23.9 (-CH(CH3ACH3 )), 23.4
B
B
(-CH(CH3ACH3 )), 22.0 (-CH3alkyl), n.o. (Co-CH3).
X-ray crystal structure analysis of 11a: formula C25H34CoN3, Mr
) 435.48, black crystal, 0.30 × 0.10 × 0.07 mm, a ) 12.706(1)
Å, b ) 11.551(1) Å, c ) 15.914(1) Å, ꢀ ) 98.78(1)°, V ) 2308.3(3)
Å3, Fcalcd ) 1.253 g cm-3, µ ) 0.759 mm-1, empirical absorption
correction (0.804 e T e 0.949), Z ) 4, monoclinic, space group
P21/c (No. 14), λ ) 0.710 73 Å, T ) 198 K, ω and ꢁ scans, 19 588
reflections collected ((h, ( k, ( l), (sin θ)/λ ) 0.66 Å-1, 5499
independent (Rint ) 0.070) and 3818 observed reflections (I g
2σ(I)), 269 refined parameters, R1 ) 0.046, wR2 ) 0.106,
maximum (minimum) residual electron density 0.25 (-0.25) e Å-3
,
hydrogen atoms calculated and refined as riding atoms.
Catalytic Ethylene Polymerization. A 1 L Bu¨chi glass autoclave
with a catalyst reservoir and stirrer was evacuated and filled with
argon three times before it was charged with 200 mL of toluene
and 6.8 mL of 10% methylalumoxane in toluene. A precise amount
of respective complex (0.05 mmol) was dissolved in 10 mL of
toluene and then loaded into the catalyst reservoir. The stirrer was
started (600 rpm), and the autoclave was thermostated at room
temperature while the solution was saturated with ethylene at 2
bar, which was controlled by bpc 1202 (Bu¨chi pressflow gas
controller with program “bls2”). After the solution was saturated
with ethylene (the line of consumption volume went flat), the
catalyst solution in the reservoir was introduced directly into the
autoclave. In the case of preactivation of the metal, 200 mL of
toluene and 5 mL of 10% methylalumoxane in toluene was added
to the Bu¨chi autoclave and 1.8 mL was added to the catalyst solution
before it was loaded into the catalyst reservoir. The polymerization
reaction was stopped by terminating the transfer of ethylene with
the bpc controller and quenching with 10 mL of aqueous HCl in
methanol (1/1 v/v). The precipitated polyethylene was collected
by filtration, washed subsequently with HCl, water, and acetone,
and dried at 80 °C under vacuum overnight to constant weight.
The polymer was characterized by DSC and 13C NMR. The obtained
polymer is linear polyethylene. The oligomers were extracted from
the water phase with diethyl ether, and the resulting organic solvent
was removed in vacuo. The oligomers were charactericed by GPC
Preparation of Complex 11a. In a flame-dried Schlenk flask
the [bis(imino)pyridine]CoCl2 complex 7a (200 mg, 0.41 mmol)
and solid methyllithium (26.8 mg, 1.22 mmol, 3 equiv) were mixed
with 20 mL of precooled diethyl ether at -78 °C. The mixture
was then slowly warmed to 10 °C within 20 h with stirring. The
solution was filtered under argon through Celite, and the separated
lithium chloride was not washed further; instead, the solvent was
rapidly removed in vacuo to yield the purple product 11a (89%,
159 mg, 0.36 mmol). The product is stable for some weeks on
storage in a glovebox. Crystals suitable for X-ray diffraction were
obtained during the preparation in diethyl ether at 10 °C. Mp (DSC):
149 °C. Anal. Calcd for C25H34CoN3 (435.49): C, 68.95; H, 7.87;
1
and H NMR.
Ethene Polymerization for ESI-MS Mechanistic Studies.
Under an inert atmosphere the respective complex (0.05 mmol)
was reacted with 8 mL of 10% methylalumoxane in toluene in 30
mL of tetrahydrofuran in a 100 mL Schlenk flask. The flask was
evacuated and purged with ethene (2 bar) at room temperature. The
reaction mixture was stirred under a constant pressure of 1 bar of
ethene for 0.5 h at room temperature. Then the ethene pressure
was released, and the reaction was quenched with 2 mL of methanol.
A sample from the supernatant was analyzed by mass spectrometry
with a nano spray inlet.
1
N, 9.65. Found: C, 68.44; H, 7.93; N, 9.29. H NMR (d8-toluene,
3
400 MHz, 298 K): δ (1H) 10.10 (t, J ) 7.5 Hz, 1H, 4-Hpy), 7.68
(d, 3J ) 7.5 Hz, 1H, 3-Hpy), 7.53 (d, 3J ) 7.5 Hz, 1H, 5-Hpy), 7.49
Acknowledgment. Financial support from the Fonds der
Chemischen Industrie and the Deutsche Forschungsgemein-
schaft are gratefully acknowledged. We thank the BASF for
a gift of solvents.
(m, 1H, 4-Haryl), 7.39 (m, 2H, 3-Haryl), 6.40 (m, 1H, -CHd), 5.60
3
Z
(br, 2H, dNCH2-), 5.16 (d, J ) 17.4 Hz, 1H, dCH2 ), 4.96 (d,
3J ) 10.8 Hz, 1H, dCH2 ), 3.08 (sept, 3J ) 6.7 Hz, 2H,
E
3
B
-CH(CH3)2), 1.12 (d, J ) 6.7 Hz, 6H, -CH(CH3ACH3 )), 0.61
3
B
(d, J ) 6.7 Hz, 6H, -CH(CH3ACH3 )), 0.54 (s, 3H, Co-CH3),
-0.64 (s, 3H, -CH3alkyl), -1.51 (s, 3H, -CH3aryl). 13C{1H} NMR
(d8-toluene, 100 MHz, 298 K): δ 167.4 (NdCalkyl), 163.7 (NdCaryl),
157.4 (C-6py), 155.9 (C-2py), 155.3 (C-1aryl), 137.5 (C-2aryl), 132.6
(-CHd), 126.5 (C-4aryl), 123.9 (C-3aryl), 122.6 (C-5py), 121.9 (C-
3py), 116.6 (C-4py), 115.4 (dCH2), 61.3 (dNCH2-), 28.5
Supporting Information Available: Text, figures, and tables
giving further experimental and spectroscopic details and CIF files
giving crystallographic data. This material is available free of charge
via the Internet at http://pubs.acs.org.
OM800726Y