Synthesis, characterisation and solid state structures of α-diimine cobalt(II) complexes: Ethylene polymerisation tests

Article abstract of DOI:10.1016/j.jorganchem.2007.12.007

A series of cobalt(II) compounds of the type [CoX₂(α-diimine)] were synthesised by direct reaction of anhydrous CoCl₂ or CoI₂ and the corresponding α-diimine ligand, in CH₂Cl₂: [CoI₂(o,o′,p-Me₃C₆H₂-D AB)] (1), [CoI₂(o,o′-ⁱPr₂C₆ H₃-DAB)] (2), (where Ar-DAB = 1,4-bis(aryl)-2,3-dimethyl-1,4-diaza-1,3-butadiene), and [CoCl₂(o,o′,p-Me₃C₆H₂- BIAN)] (3), [CoCl₂(o,o′-ⁱPr₂C₆ H₃-BIAN)] (4), and [CoI₂(o,o′-ⁱPr₂C₆ H₃-BIAN)] (5) (where Ar-BIAN = bis(aryl)acenaphthenequinonediimine). All compounds were characterised by elemental analyses, IR, mass spectrometry, and X-ray diffraction whenever possible. The crystal structures of compounds 2-4 showed, in all cases, distorted tetrahedral geometries about the Co, built by two halogen atoms and two nitrogen atoms of the α-diimine ligand. Compounds 3 and 4, as well as [CoCl₂(o,o′,p-Me₃C₆H₂- DAB)] (1a), and [CoCl₂(o,o′-ⁱPr₂C₆ H₃-DAB)] (2a), were activated by methylaluminoxane (MAO) and tested as catalysts for ethylene polymerisation, showing low catalytic activities. Selected polyethylene (PE) samples were characterised by ¹H and ¹³C NMR and FT-IR spectroscopies, and by differential scanning calorimetry (DSC), revealing branching microstructures (2.5-5.5%).

Full text of DOI:10.1016/j.jorganchem.2007.12.007

Available online at www.sciencedirect.com
Journal of Organometallic Chemistry 693 (2008) 769–775
www.elsevier.com/locate/jorganchem
Synthesis, characterisation and solid state structures of
a-diimine cobalt(II) complexes: Ethylene polymerisation tests
a
b
a,
b,
c
*
Vitor Rosa , Sonia A. Carabineiro , Teresa Aviles , Pedro T. Gomes *, Richard Welter ,
´
´
d
d
´
Joao M. Campos , M. Rosario Ribeiro
˜
a
ˆ
REQUIMTE/CQFB, Departamento de Quı´mica, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516, Caparica, Portugal
b Centro de Quı´mica Estrutural, Departamento de Engenharia Quı´mica e Biolo´gica, Instituto Superior Te´cnico, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
c Laboratoire DECOMET, Institut de Chimie UMR-CNRS 7177, Universite´ Louis Pasteur 4, rue Blaise Pascal 67000 Strasbourg, France
ˆ
´ ´ ´
Instituto de Ciencia e Engenharia de Materiais e Superfıcies – ICEMS, Departamento de Engenharia Quımica e Biologica, Instituto Superior Tecnico,
d
´
Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal
Received 2 November 2007; received in revised form 5 December 2007; accepted 6 December 2007
Available online 15 December 2007
Abstract
A series of cobalt(II) compounds of the type [CoX2(a-diimine)] were synthesised by direct reaction of anhydrous CoCl2 or CoI2 and
the corresponding a-diimine ligand, in CH2Cl2: [CoI2(o,o0,p-Me3C6H2-DAB)] (1), [CoI2(o,o0-iPr2C6H3-DAB)] (2), (where Ar-DAB = 1,4-
bis(aryl)-2,3-dimethyl-1,4-diaza-1,3-butadiene), and [CoCl2(o,o0,p-Me3C6H2-BIAN)] (3), [CoCl2(o,o0-iPr2C6H3-BIAN)] (4), and
[CoI2(o,o0-iPr2C6H3-BIAN)] (5) (where Ar-BIAN = bis(aryl)acenaphthenequinonediimine). All compounds were characterised by ele-
mental analyses, IR, mass spectrometry, and X-ray diffraction whenever possible. The crystal structures of compounds 2–4 showed,
in all cases, distorted tetrahedral geometries about the Co, built by two halogen atoms and two nitrogen atoms of the a-diimine ligand.
Compounds 3 and 4, as well as [CoCl2(o,o0,p-Me3C6H2-DAB)] (1a), and [CoCl2(o,o0-iPr2C6H3-DAB)] (2a), were activated by methylalu-
minoxane (MAO) and tested as catalysts for ethylene polymerisation, showing low catalytic activities. Selected polyethylene (PE) samples
were characterised by 1H and 13C NMR and FT-IR spectroscopies, and by differential scanning calorimetry (DSC), revealing branching
microstructures (2.5–5.5%).
Ó 2007 Elsevier B.V. All rights reserved.
Keywords: Cobalt(II) complexes; a-Diimine ligands; X-ray diffraction; Ethylene; Polymerisation
1. Introduction
microstructures [2,3]. Among these ligands are the steri-
cally demanding a-diimines [4]. These bidentate ligands
are very rigid and it is possible to change easily their back-
bone and N-substituents, allowing the control of the steric
and electronic effects at the metal centre. A great number of
group 10 transition metal complexes bearing a-diimine
ligands have been synthesised and characterised since then,
and their employ as catalysts for the oligomerisation and
polymerisation of a-olefins have been extensively studied
[3a]. However, reports on cobalt complexes containing this
type of ligands are scarce [5]. Recently, some results in the
insertion polymerisation of ethylene have been reported
using tetrahedral Co(II) complexes with related ligands
[5e,6]. The a-diimine ligands have also been object of
The commercial production of polyolefins from ethylene
and propylene had an enormous development with the use
of Ziegler–Natta type catalysts. This field has been remark-
ably renewed with the use of catalysts based on early-tran-
sition metallocenes [1]. In the mid-1990s, a new type of
catalysts have been discovered, based on late transition
metals and quite simple ligands, leading to novel polymer
*
Corresponding authors. Tel.: +351 218419612; fax: +351 218419612.
´
E-mail addresses: tap@dq.fct.unl.pt (T. Aviles), pedro.t.gomes@
ist.utl.pt (P.T. Gomes).
0022-328X/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2007.12.007

770
V. Rosa et al. / Journal of Organometallic Chemistry 693 (2008) 769–775
yses, FT-IR and 1H NMR spectroscopies and mass
spectrometry (MALDI-TOF-MS) (see Experimental and
Table S1 supporting information).
X
X
R
R
R
R
R
R
R
R
X
X
Co
Co
R'
N
N
R´
R'
N
N
R'
1
The H NMR spectra of compounds 1–5, in CD2Cl2, at
room temperature, exhibit paramagnetic contact shifts [10],
showing resonances spread from ca. d 107 to ꢀ25. These
contact shifts are due to the paramagnetic character of
the Co(II) complexes that exhibit high spin S = 3/2 in the
solid state [9], although in solution they may be involved
in equilibria with their S = 1/2 square planar conformers.
A MALDI-TOF-MS study in dichloromethane was per-
formed for all the synthesised complexes. The samples were
dissolved in dichloromethane (1 lg/lL), and no matrix was
added to obtain the mass spectra. All the complexes
showed peaks attributed to the corresponding species
[CoXL]+, and to [L + H+], (where X = Cl or I, and
L = diimine ligand). These species were formed by the dis-
sociation of one halide or by protonation of the dissociated
neutral a-diimine ligand, to give cationic species in all
cases. In compound 4, the peak attributed to the parent
ion [CoCl2L4-H+] was detected in the negative ionisation
mode (see Experimental and Table S1 supporting informa-
tion, footnote d). These results agree very well with the pro-
posed structures for the synthesised compounds.
R = R' = Me, X = I, 1
R = Pr, R' =H, X = I, 2
i
R = R' = Me, X = Cl, 3
R = R' = Me, X = Cl, 1a
i
R = Pr, R' = H, X = Cl, 4
i
R = Pr, R' =H, X = Cl, 2a
i
R = Pr, R' = H, X = I, 5
Scheme 1.
different studies regarding the relative binding strengths [7]
as well as their reactivity with main group metals [8].
We have been interested in the synthesis and character-
isation by X-ray diffraction and EPR spectroscopy of
cobalt(II) complexes of the general formula [CoX2(a-dii-
mine)], where X = Cl, or I and a-diimines such as
bis(aryl)acenaphthenequinonediimine (Ar-BIAN) and 1,4-
bis(aryl)-2,3-dimethyl-1,4-diaza-1,3-butadiene (Ar-DAB)
[9]. The present paper reports on the synthesis and charac-
terisation of further a-diimine Co(II) halide complexes
(Scheme 1), namely, [CoI2(o,o0,p-Me3C6H2-DAB)] (1);
[CoI2(o,o0-iPr2C6H3-DAB)] (2); [CoCl2(o,o0,p-Me3C6H2-
BIAN)]
(3);
[CoCl2(o,o0-iPr2C6H3-BIAN)]
(4);
[CoI2(o,o0-iPr2C6H3-BIAN)] (5). Complexes 3 and 4, and
also the previously described BIAN analogues 1a and 2a
(similar to 1 and 2, respectively, but with X = Cl instead)
[9] were activated by methylaluminoxane and tested as cat-
alysts for ethylene polymerisation.
The FT-IR spectra of the cobalt(II) complexes, recorded
as Nujol mulls, display medium absorption bands in the
range m ¼ 1652–1615 cmꢀ1, which is the absorption region
ꢀ
ꢀ
for mðC@ NÞ. Bands assigned to the free ligand C@N
stretching vibrations were observed in the range
m ¼ 1674–1637 cmꢀ1. In general, the bands in the com-
ꢀ
plexes are shifted to lower wavenumbers which is a crite-
rion of the coordination of both diimine nitrogen atoms
of the a-diimine ligands to the cobalt(II) ion (see Table
S2 supporting information).
2. Results and discussion
2.1. Synthesis and characterisation of compounds
Crystals were obtained for complexes 2–4 enabling the
determination of their crystal structures. Table 1 lists
selected bond distances and angles.
The reaction of equimolar quantities of anhydrous
CoX2 (X = Cl or I) and a-diimine ligands, in deoxygenated
and dehydrated CH2Cl2, at room temperature, yielded red–
brown crystalline solids 1–5, with general formula
[CoX2(a-diimine)] (Fig. 1), in ca. 75–94% yields. All syn-
thesised compounds were characterised by elemental anal-
The molecular structure of compound 2 shows an asym-
metric unit formed by a half molecule of [CoI2(o,o0-iPr2C6
H3-DAB)] (where Ar-DAB = 1,4-bis(aryl)-2,3-dimethyl-
1,4-diaza-1,3-butadiene) with the Co atom occupying a
special position (0,0,0). The corresponding molecular
structure is generated by symmetry, giving rise to a dis-
torted tetrahedral geometry around the Co atom, which
is built up of two iodine atoms and two nitrogen atoms
of the ligand (Fig. 1). In fact, due to the symmetry exhib-
ited, the dihedral angle formed by planes defined by I1–
Co1–I2 and N1–Co1–N1_1 is exactly 90°. The I1–Co1–I2
angle is 111.68(3)° which is very close to ideal tetrahedral
(109.47°), however the other two bonds to N atoms intro-
duce some distortion since the bite angle N1–Co1–N1_1 is
80.15(16)°. The distances Co–I are 2.5200(7) and 2.5425(8)
˚
˚
A, while the Co–N is 2.045(3) A. The planes formed by the
aryl rings C5–C6–C7–C8–C9–C10 are nearly perpendicular
to the plane defined by Co1–N1–C1–C1_1–N1_1 (89.63°).
However, the aryl rings themselves are not exactly parallel
to each other, making a dihedral angle of 16.79°. These
Fig. 1. ORTEP view of the complex 2. The ellipsoids enclose 50% of the
electronic density. Hydrogen atoms are omitted for clarity.

V. Rosa et al. / Journal of Organometallic Chemistry 693 (2008) 769–775
771
Table 1
They are nearly perpendicular to the plane defined by
Co1–N1–C1–C2–N2 (83.39 and 87.87°).
Selected bond distances and angles for complexes 2–4
2
3
4
The molecular structure of compound 4 consists of an
asymmetric unit containing two independent molecules,
also having distorted tetrahedral geometries (Fig. 3). The
planes defined by Cl1–Co1–Cl2 and N1–Co1–N2 form
angles of 89.11 and 87.83°, for molecules A and B, respec-
tively. The Cl1–Co1–Cl2 angles are 115.15(9) and
117.27(8)°, while the N1–Co1–N2 bite angles are 81.5(2)
and 82.2(2)°, for molecules A and B, respectively. The dis-
tances Co–Cl and Co–N are similar to the ones found in
complexes 2 and 3. As for the latter structures, the aryl
rings are almost parallel to each other, being nearly perpen-
dicular to the plane defined by Co1–N1–C1–C2–N2.
The coordinated imine C@N bond distances (1.232(8)–
Molecule A
Molecule B
˚
Distances (A)
Co1–Cl1
Co1–Cl2
Co1–I1
Co1–I2
Co1–N1
Co1–N2
C1–N1
C2–N2
C2–C4
C1–C3
C1–C2
N1–C5
N2–C14
C4–C30
C3–C30
–
–
2.2037(5)
2.2105(5)
–
2.192(2)
2.227(2)
–
2.208(2)
2.195(2)
–
2.5425(8)
2.5200(7)
2.045(3)
–
1.279(4)
–
–
1.490(5)
–
1.448(5)
–
–
–
–
–
–
2.0753(12)
2.0678(12)
1.2795(19)
1.2773(19)
1.460(2)
1.459(2)
1.520(2)
1.4345(17)
1.4436(17)
1.416(2)
1.425(2)
2.084(6)
2.067(6)
1.232(8)
1.283(8)
1.473(9)
1.464(9)
1.563(9)
1.450(9)
1.428(9)
1.419(9)
1.430(10)
2.092(5)
2.085(6)
1.278(8)
1.257(8)
1.489(8)
1.480(9)
1.504(9)
1.454(8)
1.442(9)
1.416(9)
1.407(9)
˚
1.283(8) A), as most of the other structural features of com-
plexes 2–4, are similar to those found for the other
[CoX2(a-diimine)] described in the literature [5e,9,11], and
are slightly shorter than the C@N bond distances found
Angles (°)
˚
Cl2–Co1–Cl1
I2–Co1–I1
N1–Co1–N2
N2–C2–C1
N1–C1–C2
C5–N1–C1
C14–N2–C2
–
112.51(2)
–
115.15(9)
–
117.27(8)
–
in the free ligands (e.g. ligand L4: 1.250(6)–1.295(6) A [12]).
111.68(3)
80.15(16)
–
115.7(2)
121.9(3)
–
82.17(5)
118.07(12)
118.03(12)
119.38(12)
119.76(12)
81.5(2)
117.1(6)
117.0(6)
115.8(6)
119.1(6)
82.2(2)
121.1(6)
117.6(6)
117.9(5)
121.3(6)
2.2. Ethylene polymerisation tests
Complexes 3 and 4 (BIAN derivatives), were tested as
catalysts for ethylene polymerisation in the presence of
cocatalyst methylaluminoxane (MAO). In order to com-
pare the influence of the ligand framework (DAB vs.
BIAN), studies were also carried out for compounds 1a
and 2a, described in a previous paper [9], which only differ
from 1 and 2 in the halide atom (having Cl instead of I). An
experimental matrix encompassing temperature and cocat-
alyst/catalyst ratio was applied to determine critical factors
and characteristics of polymerisation reactions. According
to the rating of effectiveness of catalysts, based on its activ-
ities, provided by Gibson et al. [3b], the results obtained
(Table 2) are characteristic of very low to low activities.
The higher activities were observed at 20 °C, for all cat-
alysts studied. Except for 1a/MAO system, an increase in
the [Al]/[Co] ratio from 500 to 1000 led to improvements
in the catalytic activities. Increasing the [Al]/[Co] ratio to
features are similar to the ones found in previous a-diimine
complexes synthesised by our group, namely 1a and 2a [9].
The molecular structure of compound 3 also shows a
distorted tetrahedral geometry, just like in the case above,
formed by two chloride atoms and two nitrogen atoms of
the chelating ligand (Fig. 2). The dihedral angle formed
by planes defined by Cl1–Co1–Cl2 and N1–Co1–N2 is
89.25°. The Cl1–Co1–Cl2 angle is 112.51(2)° while the
N1–Co1–N2 bite angle is 82.17(5). The distances Co–Cl
˚
are 2.2037(5) and 2.2105(5) A, and the Co–N bond dis-
tances are similar to the ones found in complex 2. The aryl
rings C5–C6–C7–C8–C9–C10 and C14–C15–C16–C17–
C18–C19 are almost parallel, forming an angle of 7.25°.
Fig. 2. ORTEP view of the complex 3. The ellipsoids enclose 50% of the
Fig. 3. ORTEP view the complex 4 (molecule A). The ellipsoids enclose
electronic density. Hydrogen atoms are omitted for clarity.
50% of the electronic density. Hydrogen atoms are omitted for clarity.

772
V. Rosa et al. / Journal of Organometallic Chemistry 693 (2008) 769–775
Table 2
Table 3
Ethylene polymerisation catalysed by 1a, 2a, 3 and 4/MAO systemsa
Number of branches per 1000 C and thermal analyses of selected
polyethylene samples
Entries
Complex
[Al]/
[Co]
Temp.
(°C)
m PE
(mg)
Activity
(g/(mmol-cat.h.bar))
,d
Entry Reaction
conditionsa
No. branches/
1000 Cb
DHm
Tconset
Tcmax
(J gꢀ1 c
)
(°C)
(°C)
1
2
3
4
5
6
7
8
9
1a
1a
1a
1a
1a
1a
2a
2a
2a
2a
2a
2a
3
500
500
500
0
20
40
60
20
20
0
20
40
60
20
20
0
20
40
60
20
20
0
20
40
60
20
20
33
43
b
0.83
1.08
2
5
11
17
23
a
1a/500
1a/1000
2a/1000
3/1000
4/1000
25
25
55
25
46
90.8
89.4
90.0
73.0
47.4
84.5
85.7
85.2
98.7
51.0
103.7
103.6
103.5
109.8
76.6
500
0
32
1
4
5
b
1000
2000
500
500
500
0.80
0.03
0.10
0.13
Complex/(Al/Co ratio); T = 20 °C.
Estimated by H NMR [15].
Determined by DSC.
The peak value of the melting endotherm (ideally taken as the tem-
b
1
c
b
10
11
12
13
14
15
16
17
18
19
20
21
22
23
26
a
500
d
1000
2000
500
500
500
9
4
b
0.23
0.10
perature at which the largest and most perfect crystals are melting) is
frequently assigned as the melting temperature, i.e. Tm ꢁ Tmax
.
b
b
3
tain diimine ligands with mesityl substituents, give rise to
branching degrees of 25/1000 C, whereas 2a and 4 (entries
11 and 23), containing the bulkier o,o0-iPr2Ph substituents,
produce PE twice as branched as the others. This effect is
also observed in the analogous nickel catalyst systems
[14]. The fact that system 2a/MAO (entry 11) produces
PE with thermal features similar to those of 1a/MAO
(entries 2 and 5), but with a higher branching, may be
explained by a variation of the PE molecular weight
induced by the o,o0-iPr2Ph diimine substituents of 2a. On
the other hand, comparison of the thermal parameters of
the PEs produced by 3 and 4/MAO shows that the latter
catalyst system presents a lower melting temperature and
a lower crystallinity in agreement with the higher number
of branches shown by this sample.
3
3
500
0
4
2
16
16
b
3
1000
2000
500
500
500
500
1000
2000
0.10
0.05
0.40
0.41
3
4
4
4
b
4
4
26
9
0.65
0.23
4
Conditions: Pethylene = 2 bar (relative); Vtoluene = 50 mL; ncat = 10 l-
mol; t = 2 h.
b
Traces.
2000 caused a decrease in the activity. Catalyst system 3/
MAO, containing the mesityl-BIAN ligand showed the
lowest activity, much lower than its o,o0-iPr2Ph-BIAN ana-
logue 4/MAO. On the contrary, the o,o0-iPr2Ph-DAB based
catalyst system 2a/MAO, containing the bulkier iPr substit-
uents on the phenyl groups, showed lower activity in com-
parison with its mesityl analogue 1a/MAO, the latter being
the most active of all the catalysts studied. All these sys-
tems are less active than those reported by Laine et al.
[5e], for the similar [CoBr2(a-diimine)]/MAO system,
where the a-diimine used was 1,4-(bis-2,6-diisopropyl-
phenyl)-1,4-diaza-1,3-butadiene, in which the chelating
ligand has a less hindered framework than those used in
the present work. However, the activities obtained by these
authors were measured at higher ethylene pressures (3–
5.5 bar), and the products obtained were mainly oily
branched ethylene oligomers.
3. Conclusions
A series of paramagnetic cobalt(II) complexes of general
formula [CoX2(a-diimine)]: [CoI2(o,o0,p-Me3C6H2-DAB)]
(1),
[CoI2(o,o0-iPr2C6H3-DAB)]
(2),
[CoCl2(o,o0,p-
Me3C6H2-BIAN)] (3), [CoCl2(o,o0-iPr2C6H3-BIAN)] (4)
and [CoI2(o,o0-iPr2C6H3-BIAN)] (5), were synthesised by
direct reaction of equimolar amounts of the corresponding
cobalt dihalide and a-diimine ligand, in CH2Cl2, in c.a. 75–
94% yields. Single crystal X-ray structural data for com-
pounds 2–4 show, in all cases, the cobalt atom in a dis-
torted tetrahedral coordination generated by two halide
atoms and two nitrogen atoms of the a-diimine ligand.
Compounds 3 and 4, as well as [CoCl2(o,o0,p-Me3C6H2-
DAB)] (1a), and [CoCl2(o,o0-iPr2C6H3-DAB)] (2a),
revealed low activities in ethylene polymerisation when
activated with MAO. The resulting branched (2.5–5.5%)
low molecular weight polyethylenes are solid samples, with
melting points in the range 77–110 °C.
Selected polyethylene (PE) samples (runs no. 2, 5, 11, 17
and 23) were characterised (Table 3) as white solids with
branching degrees typical of low density polyethylene
(LDPE), varying from 25–55 branches per 1000 carbon
1
atoms, as determined by H NMR spectroscopy. The cor-
responding FT-IR spectra (see Fig. S1 supporting informa-
tion) showed in all samples the presence of a band at ca.
ꢀm ¼ 1378 cmꢀ1, in agreement with the presence of methyl
groups associated with branching [13]. Their melting tem-
peratures were determined by DSC (see Fig. S2 supporting
information), and lie in the range 77–110 °C. The catalyst
systems based on 1a and 3 (entries 2, 5 and 17), which con-
4. Experimental
4.1. General
All reactions and manipulations of solutions were per-
formed under nitrogen or argon atmospheres using stan-

V. Rosa et al. / Journal of Organometallic Chemistry 693 (2008) 769–775
773
dard Schlenk techniques. Reagent grade solvents were
4.2. Synthesis of complexes
deoxygenated and dehydrated before use according to liter-
ature methods. CoCl2 and CoI2 were purchased from
Aldrich and the a-diimine ligands were synthesised as
described in the literature [16].
Elemental analyses were obtained from REQUIMTE,
Chemistry Department, New University of Lisbon Service
using a Thermo Finnigan-CE Flash-EA 1112-CHNS
Instrument.
4.2.1. Synthesis of [CoI2(o,o0,p-Me3C6H2-DAB)] (1)
A green suspension of CoI2 (0.2 g, 0.62 mmol) in
CH2Cl2 (20 mL) was treated with a yellow solution of
o,o0,p-Me3C6H2-DAB, (0.2 g, 0.64 mmol) in CH2Cl2
(30 mL). An almost immediate colour change was observed
from green to red–brown. The mixture was stirred over-
night, at room temperature, until complete dissolution.
The solution was filtered, and concentrated by vacuum
removal of the solvent. A brown crystalline solid precipi-
tated which was separated by filtration, washed with
diethyl ether (2 ꢂ 10 mL) and petroleum ether
(2 ꢂ 10 mL). After recrystallisation from CH2Cl2/petro-
leum ether 0.36 g of 1 were obtained (yield: 94%).
Infrared spectra of complexes were recorded as Nujol
mulls on NaCl plates using a Mattson Satellite FTIR
spectrometer.
MALDI-TOF-MS analysis were obtained from REQ-
UIMTE, MALDI-TOF-MS Service Laboratory, and
have been performed in a MALDI-TOF-MS model voy-
ager DE-PRO Biospectrometry Workstation equipped
with a nitrogen laser radiating at 337 nm from Applied
Biosystems (Foster City, United States). MALDI mass
spectra were acquired and treated with Data Explorer
software version 4 series. The MALDI-TOF-MS study
in dichloromethane was carried out for complexes 1–5.
Samples were dissolved in dichloromethane (1 lg/lL),
and 1–2 lL of the corresponding solution was spotted
on a well of a MALDI-TOF-MS sample plate and
allowed to dry. No matrix was added. Measurements
were performed in the reflector positive ion mode, with
a 20 kV accelerating voltage, 80% grid voltage, 0.005%
guide wire, and a delay time of 200 ns, for complexes
1–5 and in the negative ion mode for complex 4. Mass
spectral analysis for each sample was based on the aver-
age of 500 laser shots.
1H NMR (CD2Cl2, 400 MHz): d 107.11, 18.44, 15.22,
0.50. IR (nujol mull/NaCl plates), cmꢀ1: 1631 ðmC@NÞ.
ꢀ
MS (MALDI-TOF); m/z: 506.7 [CoIL]+ (54.25%), 321.8
[L + H+] (100%) (L = diimine ligand). Anal. Calc. for
C22H28CoI2N2 (MW = 633.21): C, 41.73; H, 4.46; N,
4.42. Found: C, 41.67; H, 4.44; N, 4.71%.
4.2.2. Synthesis of [CoI2(o,o0-iPr2C6H3-DAB)] (2)
Compound
2 was obtained using the procedure
described for 1. Yield: 77%. Crystals suitable for X-ray dif-
fraction were obtained.
1H NMR (CD2Cl2, 400 MHz): d 95.22, 17.11, 7.59, 0.35,
ꢀ3.00, ꢀ24.59. IR (nujol mull/NaCl plates), cmꢀ1: 1639
ðmC@NÞ. MS (MALDI-TOF); m/z: 590.76 [CoIL]+
ꢀ
(16.38%), 405.9 [L + H+] (67.65%) (L = diimine ligand).
Anal. Calc. for C28H40CoI2N2 (MW = 717.37): C, 46.88;
H, 5.62; N, 3.90. Found: C, 46.55; H, 5.47; N, 4.04%.
1H NMR of complexes 1–5 were recorded in a Bruker
Avance III 400 spectrometer (at 400.13 MHz), in CD2Cl2,
at room temperature. 1H and 13C NMR spectra of polyeth-
ylene samples were recorded in Bruker Avance III 400 (at
400.13 MHz) and Bruker Avance III 300 (at 75.47 MHz)
spectrometers, at 110°C. Polymer samples were previously
dissolved in a boiling mixture of 3:1 trichloroben-
zene:C6D6. All spectra taken in both devices were refer-
enced internally to residual protio solvent (1H) or solvent
(13C) resonances and reported relative to tetramethylsilane
(d 0). Deuterated solvents were dried with molecular sieves
and freeze-pump-thaw-degassed prior to use.
Polyethylene thermal analyses were performed with a
TA Instruments DSC2920 with MDSCÒ option, connected
to a liquid N2 cooling system and calibrated with stan-
dards. The sample weights were ca. 4–10 mg in all the
experiments. A temperature range from 0 to 150 °C has
been studied and the heating and cooling rates used were
10 °C minꢀ1. The second heating cycle was recorded.
Infrared spectra were collected on polymer films using a
Thermo-Nicolet NEXUS FT-IR spectrophotometer. The
spectra were normalised in relation to the intensity of the
absorption band centred at 720 cmꢀ1 (main polyethylene
backbone). Films were prepared in a SpecAc press
equipped with heating plates and a SpecAc 20160 temper-
ature controller.
4.2.3. Synthesis of [CoCl2(o,o0,p-Me3C6H2-BIAN)] (3)
A blue suspension of CoCl2 (0.16 g, 1.2 mmol) in
CH2Cl2 (20 mL) was treated with a red solution of o,o0,p-
Me3C6H2-BIAN (0.5 g, 1.2 mmol) in CH2Cl2 (30 mL).
The mixture turned quickly to dark red, and was further
stirred for 2 h, until complete dissolution. After filtration,
the solvent was partially removed leaving a red–brown
solid, which was separated by filtration, washed with petro-
leum ether (2 ꢂ 10 mL). Recrystallisation from CH2Cl2/
petroleum ether afforded 0.49 g of 3 (yield: 75%). Crystals
suitable for X-ray diffraction were obtained.
1H NMR (CD2Cl2, 400 MHz): d 24.73, 16.13, 7.76, 2.16,
1.29, 0.87, ꢀ1.40. IR (nujol mull/NaCl plates), cmꢀ1: 1652,
1628 ðꢀmC@NÞ. MS (MALDI-TOF); m/z: [CoClL]+ 510.59
(100%), 417.7 [L + H+] (4.49%) (L = diimine ligand). Anal.
Calc. for C30H28CoCl2N2 ꢃ 1/2 CH2Cl2 (MW = 588.86): C,
62.21; H, 4.96; N, 4.76. Found: C, 62.86; H, 5.80; N, 4.18%.
4.2.4. Synthesis of [CoCl2(o,o0-iPr2C6H3-BIAN)] (4)
Compound
4 was obtained using the procedure
described for 3. Yield: 83%. Crystals suitable for X-ray dif-
fraction were obtained.
1H NMR (CD2Cl2, 400 MHz): d 24.89, 7.83, 4.00, 3.49,
3.44, ꢀ0.09, ꢀ19.94. IR (nujol mull/NaCl plates), cmꢀ1
:

774
V. Rosa et al. / Journal of Organometallic Chemistry 693 (2008) 769–775
Table 4
ꢀ
1649, 1619 ðmC@NÞ. MS (MALDI-TOF); m/z: 594.78 [CoC-
lL]+ (23.73%), 501.9 [L + H+] (38.23%) (L = diimine
ligand). MS (MALDI-TOF, negative ionisation mode);
m/z: 629.77 [CoCl2L-H+] (68%) (L = diimine ligand). Anal.
Calc. for C36H40CoCl2N2 (MW = 630.56): C, 68.57; H,
6.39; N, 4.44. Found: C, 68.14; H, 6.29; N, 4.40%.
Crystal data and structure refinement for compounds 2–4
Compound
2
3
4
Formula
M
C28H40CoI2N2 C30H28CoCl2N2 C36H40CoCl2N2
717.3
0.71073
173(2)
546.37
0.71073
173(2)
630.53
0.71073
173(2)
˚
k (A)
T (K)
Crystal system
Space group
a (A)
Orthorhombic Orthorhombic
Monoclinic
P21/a
22.4880(5)
11.8010(4)
27.1090(6)
90.00
111.450(2)
90.00
6695.9(3)
8
1.251
0.698
30.034
161895
19531
4.2.5. Synthesis of [CoI2(o,o0-iPr2C6H3-BIAN)] (5)
A green suspension of CoI2 (0.16 g, 0.5 mmol) in
CH2Cl2 (20 mL) was treated with a red solution of o,o0-iPr2-
C6H3-BIAN (0.25 g, 0.5 mmol) in CH2Cl2 (20 mL). The
mixture turned quickly to dark red and was stirred
overnight, until complete dissolution. After filtration, the
solvent was removed to 1/4 of the volume, and petroleum
ether (40–60 °C) (5 mL) was added. A dark red solid, was
formed by storage at ꢀ20 °C. After filtration and washing
with petroleum ether (2 ꢂ 10 mL), it was recrystallised
from CH2Cl2/petroleum ether, yielding 0.37 g of complex
5 (yield: 91%).
Pnma
Pnab
˚
13.6130(2)
21.1000(2)
10.4930(5)
90.00
16.6540(3)
17.1900(2)
22.6670(4)
90.00
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
90.00
90.00
90.00
90.00
3
˚
V (A )
3013.95(15)
4
6489.16(18)
8
Z
qcalc (g cmꢀ3
)
1.581
1.119
l (mmꢀ1
hmax (°)
)
2.635
0.711
30.034
4826
4519
34.972
103035
14242
Total data
Unique data
Rint
1H NMR (CD2Cl2, 400 MHz): d 15.17, 11.35, 5.53, 4.99,
3.29, 2.63, ꢀ2.44, ꢀ22.14. IR (nujol mull/NaCl plates),
0.0520
4519
0.0000
14242
0.0000
19531
Reflections (R
[I > 3r(I)])
wR
cmꢀ1: 1640, 1615 ðmC@NÞ. MS (MALDI-TOF); m/z:
ꢀ
0.1075
1.004
0.1768
1.015
0.3434
1.049
686.73 [CoIL]+ (100%), 501.9 [L + H+] (71.99%) (L = dii-
Goodness-of-fit
mine
ligand).
Anal.
Calc.
for
C36H40CoI2N2
qmin, qmax
ꢀ1.273
ꢀ0.551
ꢀ0.839
1.160
0.079
1.387
(MW = 813.46): C, 53.15; H, 4.96; N, 3.40. Found: C,
53.28; H, 4.96; N, 3.44%.
the proper Al/Co ratio via a glass syringe. Solutions were
then brought to the desired temperatures and allowed to
equilibrate for 15 min. After this, the corresponding
amount of a toluene solution (1 mL) of the desired complex
was added to the polymerisation reactors with a glass syr-
inge. The polymerisations were terminated after 2 h by
quenching the mixture with 150 mL of an acidic methanol
(1% HCl) solution. The absence of ethylene oligomers C4–
C24 was confirmed by GC chromatography, injecting ali-
quots of the gas and liquid phases of the polymerisation
reaction samples in a Perkin–Elmer Clarus 500 gas chro-
matograph, equipped with a capillary column Tracer/Tek-
norma TRB-5MS, 30 m ꢂ 0.25 mm ID ꢂ 0.25 lm (film),
using a temperature program from 60 to 240 °C, and from
240 to 280 °C, at ramp rates of 5 and 10 °C/min, respec-
tively. The obtained polymers were then filtered, washed
several times with methanol and dried in a vacuum oven
at 60 °C for 3 days. The filtrates were evaporated until all
the methanol was removed, and the residual toluene frac-
tions were extracted with distilled water (3 ꢂ 50 mL). After
separation, the organic phases were evaporated to dryness
and no organic materials were observed.
4.3. Crystallographic details
Crystallographic and experimental details of crystal
structure determinations are given in Table 4. Single crys-
tals of complexes 2, 3, and 4 were mounted on a Nonius
Kappa-CCD area detector diffractometer (Mo Ka
˚
k = 0.71073 A). The complete conditions of data collection
(DENZO software) and structure refinements are given
below. The cell parameters were determined from reflec-
tions taken from one set of 10 frames (1.0° steps in phi
angle), each at 20 s exposure. The structures were solved
by direct methods (SHELXS-97) and refined against F2 using
the SHELXL-97 software [17]. The absorption was not cor-
rected. All non-hydrogen atoms were refined anisotropi-
cally. Hydrogen atoms were generated according to
stereochemistry and refined using a riding model in SHEL-
XL-97. Figures were generated using ORTEP3 [18].
4.4. Polymerisation details
Ethylene polymerisation tests were carried out in 200 mL
crown capped pressure bottles sealed with neoprene septum
and pump filled with nitrogen atmosphere (the bottles were
previously dried in the oven at 150 °C for several days and
degassed with three cycles of vacuum/nitrogen). Freshly
distilled toluene, dried over Na/K alloy, was added
(50 mL) to each polymerisation bottle and the resulting sol-
vent was then saturated at an ethylene relative pressure of
2 bar, which was maintained throughout the polymerisa-
tion reactions. Then the cocatalyst (MAO) was added in
Acknowledgements
We thank Fundaßcao para a Cieˆncia e Tecnologia, Portu-
˜
gal, for funding (Projects PTDC/QUI/66440/2006 and
POCI/QUI/59025/2004, co-financed by FEDER) and for
doctoral and post-doctoral fellowships to V.R. (SFRH/
BD/13777/2003) and S.A.C. (SFRH/BPD/34974/2007),

V. Rosa et al. / Journal of Organometallic Chemistry 693 (2008) 769–775
775
(f) M. Sieger, K. Hubler, T. Scheiring, T. Sixt, S. Zalis, W. Kaim, Z.
¨
Anorg. Allg. Chem. 628 (2002) 2360–2364;
(g) M. Sieger, M. Wanner, W.G. Kaim, D.J. Stufkens, T.L. Snoeck, S.
Zalis, Inorg. Chem. 42 (2003) 3340–3346.
respectively. We also thank CPU (France) and CRUP
(Portugal) for the Portuguese-French Integrated Action-
2006, No. F-27/07.
[6] (a) T.V. Laine, K. Lappalainen, J. Liimatta, E. Aitola, B. Lo¨fgren,
M. Leskela¨, Macromol. Rapid Commun. 20 (1999) 487–491;
(b) M. Qian, M. Wang, B. Zhou, R. He, Appl. Catal. A – Gen. 209
(2001) 11;
(c) C. Bianchini, G. Mantovani, A. Meli, F. Migliacci, Organome-
tallics 22 (2003) 2545–2547.
[7] (a) M. Gasperini, F. Ragaini, Organometallics 23 (2004) 995–1001;
(b) M. Gasperini, F. Ragaini, E. Gazzola, A. Caselli, P. Macchi,
Dalton Trans. (2004) 3376–3382;
Appendix A. Supplementary material
CCDC 665822, 665823 and 665824 contain the supple-
mentary crystallographic data for 3, 2 and 4, respectively.
These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: (+44) 1223-336-033; or
e-mail: deposit@ccdc.cam.ac.uk. Supplementary data asso-
ciated with this article can be found, in the online version,
at doi:10.1016/j.jorganchem.2007.12.007.
(c) M. Gasperini, F. Ragaini, S. Cenini, Organometallics 21 (2002)
2950–2957.
[8] (a) I.L. Fedushkin, N.M. Khvoinova, A.Y. Baurin, G.K. Fukin,
V.K. Cherkasov, M.P. Bubnov, Inorg. Chem. 43 (2004) 7807–7815;
(b) I.L. Fedushkin, V.A. Chudakova, A.A. Skatova, N.M. Khvoino-
va, Y.A. Kurskii, T.A. Glukhova, G.K. Fukin, S. Dechert, M.
Hummert, H. Shumann, Z. Anorg. Allg. Chem. 630 (2004) 501–507.
References
´
[9] V. Rosa, P.J. Gonzalez, T. Aviles, P.T. Gomes, R. Welter, A.C.
Rizzi, M.C.G. Passeggi, C.D. Brondino, Eur. J. Inorg. Chem. (2006)
4761–4769.
[10] See, for example: P. Cremer, P. Burger, J. Am. Chem. Soc. 125 (2003)
7664–7677.
[11] M. Tanabiki, K. Tsuchiya, Y. Motoyama, H. Nagashima, Chem.
Commun. (2005) 3409–3411.
[12] U. El-Ayaan, A. Paulovicova, Y. Fukuda, J. Mol. Struct. 645 (2003)
205–212.
[13] (a) F.J.B. Calleja, A. Hidalgo, Colloid Polym. Sci. 229 (1969) 21–23;
(b)James E. Mark (Ed.), Polymer Data Handbook, Oxford University
Press, New York, USA, 1999.
[14] L.K. Johnson, C.M. Killian, M. Brookhart, J. Am. Chem. Soc. 117
(1995) 6414–6415.
[15] Branching in polyethylene determined by 1H NMR, according to:
A.C. Gottfried, M. Brookhart, Macromolecules 36 (2003) 3085–3100.
[16] (a) R. van Asselt, C.J. Elsevier, W.J.J. Smets, A.L. Spek, R. Benedix,
Recl. Trav. Chim. Pays-Bas 113 (1994) 88–98;
(b) H. tom Dieck, M. Svoboda, T. Grieser, Z. Naturforsch. 36b
(1981) 823–832;
[1] See, for example: W. Kaminsky (Ed.), Metalorganic Catalysts for
Synthesis and Polymerization, Springer-Verlag, Hxeidelberg, 1999.
[2] See, for example: B. Rieger, L. Saunders Baugh, S. Kacker, S.
Striegler (Eds.), Late Transition Metal Polymerization Catalysis,
Wiley-VCH, Weinheim, 2003.
[3] For reviews on late transition metal catalysed olefin polymerisation
see, for example: (a) S.D. Ittel, L.K. Johnson, M. Brookhart, Chem.
Rev. 100 (2000) 1169–1204;
(b) G.J.P. Britovsek, V.C. Gibson, D.F. Wass, Angew. Chem., Int.
Ed. 38 (1999) 429–447;
(c) V.C. Gibson, S.K. Spitzmesser, Chem. Rev. 103 (2003) 283–315.
[4] G. van Koten, K. Vrieze, Adv. Organomet. Chem. 21 (1982) 151–239,
and references cited therein.
[5] (a) M.C. Barral, E. Delgado, E. Gutierrez-Puebla, R. Jimenez-
Aparicio, A. Monge, C. Delpino, A. Santos, Inorg. Chim. Acta 74
(1983) 101–107;
(b) H. tom Dieck, M. Haarich, J. Organomet. Chem. 291 (1985) 71–87;
(c) C.J. Camazon, A. Alvarez-Valdes, J.R. Masaguer, M.C. Navarro-
Ranninger, Trans. Met. Chem. 11 (1986) 334–336;
(d) Y. Doi, T. Fujita, JP Patent 10298225 (Mitsui Chemicals Inc.,
Japan) priority date April 25, 1997;
(c) M. Svoboda, H. tom Dieck, J. Organomet. Chem. 191 (1980) 321–
328.
[17] G.M. Sheldrick, SHELXL-97, University of Go¨ttingen, Germany, 1997.
[18] ORTEP3 for Windows: L.J. Farrugia, J. Appl. Crystallogr. 30 (1997)
565.
(e) T.V. Laine, M. Klinga, A. Maaninen, E. Aitola, M. Leskela¨, Acta
Chem. Scand. 53 (1999) 968–973;