Oligomerisation of ethylene to linear α-olefins by tetrahedral cobalt(II) precursors stabilised by benzo[b]thiophen-2-yl-substituted (imino)pyridine ligands

Article abstract of DOI:10.1016/j.jorganchem.2003.10.034

On activation by MAO, 2-(imino)pyridine cobalt dichlorides bearing a benzo[ b ]thiophen-2-yl substituent in the 6-position of the pyridine ring oligomerise ethylene to α-olefins with turn-over-frequencies as high as 1.5 × 10⁶ mol of C₂H₄ converted (mol of Co × h)^-1 and productivities as high as 3769 kg of oligomers (mol of Co × h × bar)^-1. Aldimine precursors are more active than ketimine analogues, yet ketimines give higher molecular weight oligomers.

Full text of DOI:10.1016/j.jorganchem.2003.10.034

Journal of Organometallic Chemistry 689 (2004) 1356–1361
www.elsevier.com/locate/jorganchem
Oligomerisation of ethylene to linear a-olefins by
tetrahedral cobalt(II) precursors stabilised by
benzo[b]thiophen-2-yl-substituted (imino)pyridine ligands q
*
Claudio Bianchini , Giuliano Giambastiani, Giuseppe Mantovani,
Andrea Meli, David Mimeau
ICCOM-CNR, via Madonna del Piano, Sesto Fiorentino 50019, Italy
Received 24 October 2003; accepted 28 October 2003
Abstract
On activation by MAO, 2-(imino)pyridine cobalt dichlorides bearing a benzo[b]thiophen-2-yl substituent in the 6-position of the
pyridine ring oligomerise ethylene to a-olefins with turn-over-frequencies as high as 1.5 ꢀ 106 mol of C2H4 converted (mol of
Co ꢀ h)ꢁ1 and productivities as high as 3769 kg of oligomers (mol of Co ꢀ h ꢀ bar)ꢁ1. Aldimine precursors are more active than
ketimine analogues, yet ketimines give higher molecular weight oligomers.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Oligomerisation; Ethylene; a-Olefins; Cobalt; (Imino)pyridine
1. Introduction
thiophenyl-substituted catalysts, whereas the sulphur
atom was suggested to have a role in increasing both the
In a recent paper, we reported that tetrahedral bis-
chloride CoII complexes stabilised by thiophen-2-yl-
substituted (imino)pyridine ligands (NT2 h and N2ThE in
Chart 1) and activated by methylaluminoxane (MAO)
catalyse in toluene the oligomerisation of ethylene to
short chain a-olefins with turn-over-frequencies (TOF)
as high as 106 mol of C2H4 converted (mol of Co ꢀ h)ꢁ1
[1]. These results were quite surprising as all previous
CoII catalysts with either imino(pyridine) or bis(im-
ino)pyridine ligands provided very low productivities
(TOFs 6 104) [2]. Under analogous conditions to those
of the N2Th and N2ThE catalysts, CoII precursors with
furanyl- and phenyl-substituted ligands (NF2 u, N2Ph in
Chart 1) were five times less active and also selective for
ethylene dimerisation. Steric reasons were considered
irrelevant in accounting for the superior activity of the
activity and the Schulz–Flory parameter a (mol Cnþ2
mol Cn) [1,3].
/
In order to rule out the occurrence of a fortuitous
combination of factors enabling the superior activity of
the N2Th and N2ThE based catalysts and eventually gain
insight into this surprising heteroatom effect, we decided
to study the ethylene oligomerisation performance of
(aldimino)pyridyl and (ketimino)pyridyl CoII bis-
chloride precursors featured by the presence of a
benzo[b]thiophenyl substituent in the 6-position of the
pyridine ring (Scheme 1). A CoII precursor with a
(ketimino)pyridyl ligand bearing a naphthyl substituent,
sterically similar to benzothiophenyl, was also prepared
for comparative purposes (Scheme 2). Preliminary re-
sults of this study are reported here.
2. Results and discussion
q Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.jorganchem.2003.10.034.
* Corresponding author. Tel.: +39-055-5225-280; fax: +39-055-5225-
203.
The introduction of a benzo[b]thiophenyl group into
the 6-position of the iminopyridyl structure was
achieved by Stille coupling between benzothiophen-2-yl
E-mail address: claudio.bianchini@iccom.cnr.it (C. Bianchini).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.10.034

C. Bianchini et al. / Journal of Organometallic Chemistry 689 (2004) 1356–1361
1357
Chart 1.
Scheme 1.
Scheme 2.
stannane and the desired 6-bromo-2-arylimino pyridine.
The latter substrates were prepared from 2,6-dibromo
pyridine via the two-step process illustrated in Scheme 1.
The 6-naphthyl pyridinimine ligand NN2 aph was pre-
pared by a Suzuki reaction between 6-bromo-2-acetyl
ketone and 2-naphthylboronic acid, followed by con-
densation of the resultant 6-naphthyl-2-acetyl ketone
with 2,6-diisopropylaniline.
The CoII complexes CoCl2(NB2 TH) (1), CoCl2(NB2 TMe
)
(2), CoCl2(NB2 TEt) (3) and CoCl2(NN2 aph) (4) were

1358
C. Bianchini et al. / Journal of Organometallic Chemistry 689 (2004) 1356–1361
obtained as green crystals in high yield by reacting one
equivalent of the appropriate N2 ligand with a THF
solution of anhydrous CoCl2 at room temperature.
Like the previously reported derivatives with N2Th
and NP2h [1], 1–4 are high-spin in the solid state with
leff at 20 °C ranging from 4.7 to 4.9 BM, which is
typical for a d7 metal ion in a tetrahedral coordination
geometry independent of the donor atom set [4]. For
all complexes, the electronic spectra in CH2Cl2 solu-
tion and the reflectance spectra were similar to each
other and with the expected bands for a d7 metal ion
in a tetrahedral coordination geometry [1]. None of the
present pyridinimine CoII compounds was studied by
X-ray diffraction analysis due to the difficulty in
getting suitable crystals. However, on the basis of the
Flory distributions of low molecular weight a-olefins.
Selected data are reported in Table 1.
The aldimine complex 1 gave rise to the most active
catalyst, yielding predominantly butenes (entry 1), while
the methyl-ketimine precursor 2 (entry 2) was signifi-
cantly more active than the ethyl-ketimine derivative 3
(entry 3). Both 2 and 3 produced Schulz–Flory distri-
butions of C4–C14 oligomers with prevalence of butenes
(82% and 85%, respectively) and hexenes (15% and 12%,
respectively). The naphthyl-substituted precursor 4 was
much less active than any benzothiophenyl-substituted
catalyst and produced almost exclusively butenes (entry
4). Under comparable conditions, the ketimine-thi-
ophenyl precursor CoCl2(NT2 h) was as active as the
benzothiophenyl analogue 2, yet with a lower a value
(0.060 vs. 0.179) (entry 8) [1]. It is worth noting that the
TOF (1.75 ꢀ 106) displayed by precursor 2 at 13 bar of
C2H4, corresponding to about 3769 kg of oligomers
(mol of Co ꢀ h ꢀ bar)ꢁ1 (entry 6), is remarkably high for
CoII catalysts [2c,6,11].
Experiments with precursor 2 in the C2H4 pressure
range from 4 to 13 bar (entries 2, 5 and 6) showed a
linear dependence of activity with the pressure, while the
a factor was independent of the pressure, indicating that
the propagation and chain-transfer rates are first order
in ethylene [1,2c,6]. In all reactions, the selectivity in a-
olefins was ca. 90% in the first 30 min; with time the
selectivity decreased due to isomerisation to internal
olefins (entry 7), preferentially with E conformation
(determined by GC–MS), while the a factor increased
due to the re-incorporation of a-olefin products into
oligomers made later in the reaction. The occurrence of
both olefin isomerisation and re-incorporation was
confirmed by independent experiments in which the ol-
igomerisation of ethylene with 2 was carried out in the
presence of an excess of 1-undecene. Odd carbon olig-
omers (C13–C15) were formed together with various
X-ray structure analysis of the related CoCl2(N2ThE
)
derivative [1], a structure can be assigned to 1–3 where
the benzothiophenyl sulphur atom does not bind co-
balt and is actually oriented away from the cobalt
centre which is tetrahedrally coordinated by two ni-
trogen and two chlorine atoms. Since the spectroscopic
characteristics of the naphthyl derivative 4 are fully
comparable to those of 1–3, one may safely conclude
that all the cobalt complexes described in this work
exhibit a tetrahedral coordination prior to activation
with MAO. Due to the presence of three unpaired
electrons, all complexes were EPR silent at room
temperature in both the solid state and solution [5].
Upon treatment with MAO in toluene, 1–4 became
EPR active in X-band showing broad signals with giso
values in the range 2.01(5)–2.04(5). Analogous behav-
iour had been previously observed for the NT2 h, N2ThE
,
NF2 u and N2Ph CoII derivatives and attributed to the
formation of low-spin square-planar CoII species upon
MAO activation [1].
The three CoII complexes 1–3 were all active catalysts
on treatment with MAO for the production of Schulz–
Table 1
Ethylene oligomerisation with cobalt(II) catalystsa
Entry
Pre-catalyst
Pressure (bar)
TOFb (ꢀ10ꢁ5
)
ac
bc
Selectivity in a-olefins (%)
1
1
2
3
4
2
2
2
4
4
5.60
4.32
2.30
0.90d
8.32
17.5
2.54
4.62
0.084
0.179
0.146
10.9
4.6
88
91
91
2
3
4
5.8
4
4
5
8
0.174
0.183
0.214
0.060
4.7
4.5
93
93
82
90
6
13
4
7e
8f
3.7
15.6
CoCl2(NT2 h
)
4
a Reaction conditions: pre-catalyst 0.8 lmol, toluene 100 ml, MAO 250 equiv., 30 min., 25 °C.
b Mol of C2H4 converted (mol of Co ꢀ h)ꢁ1; average value over three runs.
c Schulz–Flory parameters, a ¼ mol of Cnþ2 (mol of Cn)ꢁ1; b ¼ ð1 ꢁ aÞ=a.
d The amount of butenes was determined as the sum of the product in the liquid and gaseous phases by GC at low temperature. A C8/C6 ratio of
0.02 was calculated by GC.
e 1 h.
f Taken from [1].

C. Bianchini et al. / Journal of Organometallic Chemistry 689 (2004) 1356–1361
1359
undecenes, in fact. No saturated hydrocarbon was pro-
duced, which indicates the absence of chain transfer to
aluminium [2c,6].
Higher concentrations of CoII precursors (up to 12
lmol) gave the same activity trend, yet with lower pro-
ductivities as is generally observed for very active oli-
gomerisation catalysts [2c,6a].
The study reported in this work confirms that the
presence of a sulphur atom in aromatic substituents on
the 6-position of the pyridine ring does have a beneficial
effect on the catalytic performance of 2-imino-6-(orga-
nyl)pyridine CoII bis-chloride/MAO systems.
135 technique and quoted as: CH3, CH2, CH and C for
primary, secondary, tertiary and quaternary carbon at-
oms, respectively. X-band EPR spectra were obtained
with a Varian ESR9 spectrometer equipped with a
4
continuous flow He cryostat. Absorption (CH2Cl2 so-
lution) and reflectance (powdered sample) spectra were
recorded on a Perkin–Elmer Lambda 9 spectropho-
tometer. Infrared spectra were recorded on a Perkin–
Elmer 1600 Series FT-IR spectrophotometer using
samples mulled in Nujol between KBr plates. Molar
susceptibilities were measured on solid samples using a
Sherwood Scientific MSB AUTO balance. Elemental
analyses were performed using a Carlo Erba Model 1106
elemental analyser. The melting points are uncorrected.
GC analyses were performed on a Shimadzu GC-14 A
gas chromatograph equipped with a flame ionisation
detector and a 30 m (0.25 mm i.d., 0.25 lm film thick-
ness) SPB-1 Supelco fused silica capillary column. The
GC/MS analyses were performed on a Shimadzu QP
5000 apparatus equipped with a column identical with
that used for GC analysis.
Notably, the chain length of the oligomers has been
found to increase with the size of the sulphur-containing
group (entries 2 and 8), which strengthens the impor-
tance of steric effects in controlling the ethylene oligo-
merisation activity of late transition metal catalysts with
planar nitrogen ligands such as a-diimines [7,8],
(imino)pyridines [7,9,10] and 2-bis(imino)pyridines
[2c,6,11]. For these ligands, it is believed that alkyl
substituents in the 2,6-positions of the imino phenyl
group, in conjunction with a methyl group on the C
atom, force the aryl rings to lie perpendicular to the
metal coordination plane on the polymerisation time-
scale [9,12]. As a consequence, the axial positions would
become sterically congested, thus disfavouring chain
termination by b–H transfer to metal, which does occur
in the present systems as shown by the occurrence of
olefin isomerisation. NMR spectroscopy shows free ro-
tation about the N–Caryl bond in the aldimine NB2 TH and
hindered rotation in the ketimines NB2 TMe and N2BTEt [1].
Consistently, we have observed that the Schulz–Flory
parameter a increases in the order aldimine < ketimine.
On the other hand, we have found that the TOF in-
creases in the order ethyl-ketimine < methyl-ketimine <
aldimine, which is surprising as the contrary is observed
for 2,6-bis(imino)pyridyl iron precursors [2c,6]. It is
possible that 2,6-substituted aryl rings perpendicular to
the coordination plane may disfavour the coordination/
insertion of the monomer in (imino)pyridyl metal com-
plexes, yet no conclusion can be forwarded in the ab-
sence of further studies.
3.2. Synthesis of the ligands
3.2.1. (6-Benzo[b]thiophen-2-yl-pyridin-2-yl-methylene)-
(2,6-diisopropyl-phenyl)-amine (N2BTH
)
A deaerated solution of (6-bromo-pyridin-2-yl-meth-
ylene)-(2,6-diisopropyl-phenyl)-amine (0.32 g, 0.93
mmol) and benzo[b]thiophen-2-yl-trimethyl-stannane
(0.30 g, 1.02 mmol) in 10 ml of toluene was treated with
Pd(PPh3)4 (0.055 g, 0.047 mmol) and refluxed for 24 h.
The reaction mixture was allowed to cool to room
temperature and the solvent was removed under reduced
pressure. Crystallization of the yellow-orange oily resi-
due from the minimum amount of CH2Cl2 and MeOH
gave the product as yellow crystals (0.32 g, 0.80 mmol,
yield 86%). m.p. 212–213 °C. IR m(C@N) 1640 cmꢁ1. 1H
NMR (CDCl3) d 1.22 (d, J ¼ 6:9 Hz, 12H, CH(CH3)2),
2.80 (sept, J ¼ 6:9 Hz, 2H, CH (CH3)2), 7.11–7.24 (m,
3H, CH), 7.34–7.43 (m, 2H, CH), 7.83–7.93 (m, 5H,
CH), 8.19–8.28 (m, 1H, CH), 8.40 (s, 1H, N@CH).
13C{1H} NMR (CDCl3) d 24.10 (4C, CH(CH3)2), 28.66
(2C, CH(CH3)2), 120.44 (1C, CH), 121.74 (1C, CH),
122.35 (1C, CH), 123.25 (1C, CH), 123.70 (2C, CH),
124.89 (1C, CH), 125.14 (1C, CH), 125.25 (1C, CH),
125.85 (1C, CH), 137.87 (1C, C), 138.00 (1C, CH),
141.08 (1C, C), 141.48 (1C, C), 144.91 (1C, C), 149.10
(1C, C), 153.20 (1C, C), 155.09 (1C, C), 167.79 (1C,
N@CH). Anal. calc. C26H26N2S requires: C, 78.35; H,
6.58; N, 7.03%. Found: C, 78.46; H, 6.63; N, 7.11.
3. Experimental
3.1. General
All reactions were carried out under N2 using stan-
dard Schlenck techniques. 1H and 13C{1H} NMR
spectra were obtained on a Bruker ACP 200 (200.13 and
50.32 MHz, respectively). All chemical shifts are re-
ported in ppm (d) relative to tetramethylsilane, refer-
enced to the chemical shifts of residual solvent
resonances (1H and 13C). The multiplicity of the
13C{1H} NMR spectra were determined with the DEPT
3.2.2. [1-(6-Benzo[b]thiophen-2-yl-pyridin-2-yl)-ethyli-
dene]-(2,6-diisopropyl-phenyl)-amine (N2BTMe
)
This ligand was prepared like NB2 TH except for using
[1-(6-bromo-pyridin-2-yl)-ethylidene]-(2,6-diisopropyl-
phenyl)-amine (0.45 g, 1.06 mmol); yield 86%. m.p.

1360
C. Bianchini et al. / Journal of Organometallic Chemistry 689 (2004) 1356–1361
171–172 °C. IR m(C@N) 1643 cmꢁ1. 1H NMR (CDCl3) d
1.19 (d, J ¼ 6:7 Hz, 6H, CH(CH3)(CH3)), 1.20 (d, J ¼ 7:0
Hz, 6H, CH(CH3)(CH3)), 2.35 (s, 3H, N@C(CH3)), 2.80
(m, 2H, CH(CH3)(CH3)), 7.10–7.25 (m, 3H, CH), 7.37–
7.41 (m, 2H, CH), 7.83–7.93 (m, 5H, CH), 8.33 (dd,
J ¼ 6:5; 2:4 Hz, 1H, CH). 13C{1H} NMR (CDCl3) d
17.94 (1C, N@C(CH3)), 23.71 (2C, CH(CH3)(CH3)),
24.02 (2C, CH(CH3)(CH3)), 29.07 (2C, CH(CH3)
(CH3)), 120.73 (1C, CH), 121.01 (1C, CH), 121.86 (1C,
CH), 123.29 (1C, CH), 123.79 (2C, CH), 124.42 (1C,
CH), 124.91 (1C, CH), 125.27 (1C, CH), 125.84 (1C,
CH), 136.54 (1C, C), 137.85 (1C, CH), 141.30 (1C, C),
141.55 (1C, C), 145.81 (1C, C), 147.25 (1C, C), 152.09
(1C, C), 156.72 (1C, C), 167.64 (1C, N@C(CH3)). Anal.
calc. C27H28N2S requires: C, 78.60; H, 6.84; N, 6.79%.
Found: C, 78.48; H, 6.77; N, 6.85.
1H, CH). 13C{1H} NMR (CDCl3) d 18.05 (1C,
N@C(CH3)), 23.64 (2C, CH(CH3)(CH3)), 23.93 (2C,
CH(CH3)(CH3)), 28.97 (2C, C H(CH3)(CH3)), 120.28
(1C, CH), 122.13 (1C, CH), 123.68 (1C, CH), 124.21
(1C, CH), 125.28 (1C, CH), 126.91 (1C, CH), 127.03
(1C, CH), 127.03 (1C, CH), 127.27(1C, CH), 128.41 (1C,
CH), 129.18 (1C, CH), 129.40 (1C, CH), 134.18 (1C, C),
134.43 (1C, C), 136.53 (2C, C), 137.11(1C, C), 137.97
(1C, CH), 147.25 (1C, C), 156.54 (1C, C), 156.84 (1C,
C), 168.06 (1C, N@C(CH3)). Anal. calc. C29H30N2 re-
quires: C, 85.67; H, 7.44; N, 6.89%. Found: C, 85.60; H,
7.36; N, 6.95.
3.3. General procedure for the synthesis of the CoII
complexes
To a solution of anhydrous CoCl2 (0.5 mmol) in THF
(30 ml) was added the appropriate bidentate ligand (0.5
mmol) under a nitrogen atmosphere and the resulting
mixture was stirred for 24 h at room temperature. Re-
moval of the solvent under reduced pressure gave a solid
which was filtered on a sintered-glass frit, washed with
Et2O and dried in a stream of nitrogen.
3.2.3. [1-(6-Benzo[b]thiophen-2-yl-pyridin-2-yl)-propy-
lidene]-(2,6-diisopropyl-phenyl)-amine (N2BTEt
)
This ligand was prepared like NB2 TH except for
using [1-(6-bromo-pyridin-2-yl)-propylidene]-(2,6-diiso-
propyl-phenyl)-amine (0.24 g, 0.64 mmol); yield
66%. m.p. 167–168 °C. IR m(C@N) 1641 cmꢁ1. 1H NMR
(CDCl3)d 1.17–1.28(m, 15H,CH(CH3)(CH3) + CH(CH3)
(CH3) + CH2CH3), 2.80 (m, 4H, CH(CH3) (CH3) +
CH2CH3), 7.10–7.27 (m, 3H, CH), 7.37–7.42 (m, 2H,
CH), 7.84–7.92 (m, 5H, CH), 8.26 (dd, 1H, J ¼ 5:9; 2:9
Hz, CH). 13C{1H} NMR (CDCl3) d 11.80 (1C,
CH2CH3), 23.04 (2C, CH(CH3)(CH3)), 24.21 (2C,
CH(CH3)(CH3)), 24.52 (1C, CH2CH3), 28.96 (2C,
CH(CH3)(CH3)), 120.65 (1C, CH), 121.58 (1C, CH),
121.64 (1C, CH), 123.23 (1C, CH), 123.54 (2C, CH),
124.14 (1C, CH), 124.83 (1C, CH),125.19 (1C, CH),
125.75 (1C, CH), 136.31 (1C, C), 137.88 (1C,
CH),141.26 (1C, C), 141.53 (1C, C), 146.00 (1C, C),
146.84 (1C, C), 151.95 (1C, C), 156.10 (1C, C), 171.16
(1C, N@C(CH2CH3)). Anal. calc. C28H30N2S requires:
C, 78.83; H, 7.09; N, 6.57%. Found: C, 78.60; H, 7.01;
N, 6.65.
3.3.1. (6-Benzo[b]thiophen-2-yl-pyridin-2-yl-methylene)-
(2,6- diisopropyl-phenyl)-amine cobalt(II) dichloride (1)
Green microcrystals, yield 89%. IR: m(C@N) 1590
cmꢁ1. leff ¼ 4:77 BM (25 °C). Electronic spectra: diffuse
reflectance (40,000–5550 cmꢁ1): 26,000, 22,350 sh,
18,000, 16,400 sh, 14,500, 9600, 7350, 6100; CH2Cl2
solution (28,500–6250 cmꢁ1): 26,200 (e 9000), 17,200 (e
1100), 14,600 (e 2000), 9900 (e 120), 7100 (e 380). Anal.
calc. C26H26Cl2CoN2S requires: C, 59.10; H, 4.96; N,
5.30%. Found: C, 58.89; H, 4.85; N, 5.31.
3.3.2. [1-(6-Benzo[b]thiophen-2-yl-pyridin-2-yl)-ethyli-
dene]-(2,6-diisopropyl-phenyl)-amine cobalt(II) dichlo-
ride (2)
Green powder, yield 71%. IR: m(C@N) 1592 cmꢁ1
.
leff ¼ 4:80 BM (25°C). Electronic spectra: diffuse re-
flectance (40,000–5550 cmꢁ1): 26,000, 22,350 sh, 18,100,
16,000 sh, 14,700, 9700, 7400, 6100; CH2Cl2 solution
(28,500–6250 cmꢁ1): 26,000 (e 9000), 17,400 (e 1100),
14,700 (e 2100), 9900 (e 125), 7200 (e 380). Anal. calc.
C27H28Cl2CoN2S requires: C, 59.78; H, 5.20; N, 5.16%.
Found: C, 59.75; H, 5.33; N, 5.21.
3.2.4. (2,6-Diisopropyl-phenyl)-[1-(6-naphthalen-2-yl-py-
ridin-2-yl)-ethylidene]-amine (N2Naph
)
1-[6-(2-naphthyl)-pyridin-2-yl]Ethanone (0.25 g, 1.0
mmol) and 2,6-diisopropylaniline (0.89 g, 5.0 mmol)
were dissolved in 10 ml of EtOH containing two drops
of formic acid and the resulting mixture was refluxed for
24 h. Cooling the resulting yellow-orange solution to
room temperature led to the precipitation of the product
as yellow microcrystals (0.24 g, 0.62 mmol, yield 64%)
within 2 h. From the mother liquor a further 0.080 g
(0.20 mmol) was obtained after 24 h. Overall yield 82%.
3.3.3. [1-(6-Benzo[b]thiophen-2-yl-pyridin-2-yl)-propy-
lidene]-(2,6-diisopropyl-phenyl)-amine cobalt(II) dichlo-
ride (3)
Green microcrystals, yield 91%. IR: m(C@N) 1595
cmꢁ1. leff ¼ 4:75 BM (25 °C). Electronic spectra: diffuse
reflectance (40,000–5550 cmꢁ1): 26,000, 22,250 sh,
18,100, 15,900 sh, 14,500, 9600, 7200, 6100; CH2Cl2
solution (28,500–6250 cmꢁ1): 2450 (e 8500), 17,200 (e
1000), 14,350 (e 2000), 9700 (e 120), 7100 (e 350). Anal.
m.p. 170–171 °C. IR m(C@N) 1651 cmꢁ1
.
1H NMR
(CDCl3) d 1.19 (d, J ¼ 6:8, 12H, CH(CH3)2), 2.40 (s,
3H, N@C(CH3)), 2.83 (sept, J ¼ 6:8 Hz, 2H, CH
(CH3)2), 7.09–7.24 (m, 3H, CH), 7.50–7.59 (m, 2H, CH),
7.87–8.06 (m, 5H, CH), 8.30–8.39 (m, 2H, CH), 8.60 (m,

C. Bianchini et al. / Journal of Organometallic Chemistry 689 (2004) 1356–1361
1361
calc. C28H30Cl2CoN2S requires: C, 60.44; H, 5.43; N,
5.03%. Found: C, 60.29; H, 5.31; N, 5.10.
4. Supplementary material
Text giving the synthesis and characterization of the
pyridinimine ligand intermediates.
3.3.4. (2,6-Diisopropyl-phenyl)-[1-(6-naphthalen-2-yl-
pyridin-2-yl)-ethylidene]-amine cobalt(II) dichloride (4)
Pale green powder, yield 85%. IR: m(C@N) 1594
cmꢁ1. leff ¼ 4:84 BM (25 °C). Electronic spectra: diffuse
reflectance (40,000–5550 cmꢁ1): 25,900 sh, 16,500,
15,100, 9450, 7100, 5600; CH2Cl2 solution (28,500–6250
cmꢁ1): 25,000 sh, 16,900 (e 1220), 15,100 sh, 14,850 (e
2780), 9500 (e 130), 7000 (e 390). Anal. calc.
C29H30Cl2CoN2 requires: C, 64.93; H, 5.64; N, 5.22%.
Found: C, 64.79; H, 5.50; N, 4.98.
Acknowledgements
Polimeri Europa and the European Commission
(contract no. HPRN-CT-2000-00010) are thanked for
financial support.
References
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