Cationic η3-benzyl nickel compounds with diphosphine ligands as catalyst precursors for ethylene oligomerization/ polymerization: Influence of the diphosphine bite angle

Article abstract of DOI:10.1016/j.jorganchem.2003.12.007

The oligomerization and/or polymerization of ethylene catalyzed by the cationic η³-benzylcomplexes [Ni(η ³-CH₂C₆H₄-p-CF ₃)(P-P)]⁺ BPh₄^- (P-P=ⁱPr₂P(CH₂)_n PⁱPr₂, n=1-3) have been studied. The activity of these single component catalysts depends on the length of the (CH₂)_n bridge of the diphosphine ligand. Thus, the dippm derivative (n=1) displays higher activity than compounds of the dippe (n=2) or dippp (n=3) ligands. The molecular weight of the products is also a function of n, and varies in the order dippm > dippe > dippp, with the former two catalysts giving rise to low molecular weight polyethylenes and the latter to oligomers.

Full text of DOI:10.1016/j.jorganchem.2003.12.007

Journal of Organometallic Chemistry 689 (2004) 833–839
www.elsevier.com/locate/jorganchem
Cationic g3-benzyl nickel compounds with diphosphine
ligands as catalyst precursors for ethylene
oligomerization/polymerization: influence of the
diphosphine bite angle q
a
a
a,
a
a
Isabel Albers , Eleuterio Alvarez , Juan Campora *, Celia M. Maya , Pilar Palma ,
ꢀ
ꢀ
a
Luis J. Sanchez , Elisa Passaglia
b
ꢀ
a
Instituto de Investigaciones Quꢀımicas, Consejo Superior de Investigaciones Cientꢀıficas-Universidad de Sevilla. Avda.
Amꢀerico Vespucio s/n, 41092 Sevilla, Spain
Department of Chemistry and Industrial Chemistry, University of Pisa, via Risorgimento, 3556126 Pisa, Italy
b
Received 22 October 2003; accepted 8 December 2003
Abstract
The oligomerization and/or polymerization of ethylene catalyzed by the cationic g3-benzylcomplexes [Ni(g3-CH2C6H4-p-
CF3)(P–P)]þ BPh4ꢀ (P–P ¼ iPr2P(CH2)nPiPr2, n ¼ 1–3) have been studied. The activity of these single component catalysts depends
on the length of the (CH2)n bridge of the diphosphine ligand. Thus, the dippm derivative (n ¼ 1) displays higher activity than
compounds of the dippe (n ¼ 2) or dippp (n ¼ 3) ligands. The molecular weight of the products is also a function of n, and varies in
the order dippm > dippe > dippp, with the former two catalysts giving rise to low molecular weight polyethylenes and the latter to
oligomers.
Ó 2003 Elsevier B.V. All rights reserved.
Keywords: Nickel; Olefin polymerization; Oligomerization; Benzyl complex
1. Introduction
factors could also be used to modify the catalyst activity
from olefin oligomerization to polymerization. Thus,
Spencer prepared a series of agostic ethyl complexes of
the type [M(Et)(P–P)]þ (M ¼ Ni, Pd, Pt), and showed
that the barrier for b-elimination (which is related to
polymerization termination by chain-transfer processes)
is influenced by the nature of the metal center and the
length of the P–P ligand backbone [6]. More recently,
Brookhart has reported that in the dimerization of
ethylene catalyzed by the palladium complexes
[PdMe(OEt2)(P–P)]þ, the structure of the catalyst rest-
ing state is a function of the length of the polymethylene
bridge of the diphosphine [7]. In the present contribu-
tion, we report the synthesis of cationic complexes of
the type [Ni(g3-CH2C6H4-p-CF3)(P–P)]þ BPhꢀ4 (P–P ¼
bis(diisopropylphosphino)methane (dippm), 4; 1,2-bis-
(diisopropylphosphino)ethane (dippe), 5, and 1,3-
bis(diisopropylphosphino)propane (dippp), 6), along
with their behaviour as moderately active single
During the past decades, considerable advances have
been achieved in the design and application of late metal
complexes as catalysts for olefin polymerization [1].
While most of these catalysts contain ligands based on
hard-donor atoms (N–N, N–O) [2], or mixed hard-soft
donors (P–O, P–N) [3], reports on diphosphine-based Ni
polymerization catalysts are scarce despite the crucial
role that the latter ligands play in homogeneous catal-
ysis [4]. It has been demonstrated that in CO/olefin co-
polymerization, both the steric properties and the bite
angle [5] of the associated diphosphine ligands exert a
profound influence on the catalytic activity [4]. These
q Supplementary data associated with this article can be found, in the
online version, at doi:10.1016/j.jorganchem.2003.12.007.
* Corresponding author. Tel.: +34-954489555; fax: +34-954460565.
ꢀ
E-mail address: campora@iiq.csic.es (J. Campora).
0022-328X/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2003.12.007

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I. Albers et al. / Journal of Organometallic Chemistry 689 (2004) 833–839
component catalysts for the polymerization or the
oligomerization of ethylene. We describe some of the
main features of this system, focusing on the influence of
the diphosphine bite angle on the catalyst performance.
Allyl ligands have found important uses in Ni-cata-
lyzed olefin oligomerization and polymerization reac-
tions, due to their capability of modifying their
coordination mode from g3 to g1, providing in this way
both a precursor M-alkyl unit and an empty site avail-
able for monomer coordination [8]. Although the well-
known [9] pseudoallylic benzyl ligands display this
feature to a higher degree than conventional allyl groups,
it is only recently that Bazan [10a–10c] and others [10d]
have taken advantage of this feature, and employed g3-
benzylnickel complexes as catalyst precursors in olefin
polymerization reactions. We have followed a similar
approach, introducing an electron withdrawing group
(CF3) in the aromatic ring of the benzyl ligand in order to
further destabilize its g3 binding mode.
toward low field as compared with that of the neutral
1
precursor, and the corresponding JCH coupling con-
stant increases to ca 155–160 Hz. Like other g3-benzyl
complexes, the aromatic signals in the 1H and the
13C{1H} spectra of 4–6 suggest higher symmetry than
expected, as a consequence of a fast suprafacial shift of
the Ni(P–P) fragment between the two possible g3-
benzylic coordination sites [9c,11].
The pseudoallylic coordination of the benzyl ligand
has been confirmed by an X-ray diffraction study of
compound 4. Fig. 1 shows an ORTEP view of the cat-
ionic moiety of this compound. The main feature of this
structure is the distortion of the square planar geometry
of the Ni atom, illustrated by the small values of the P1–
Ni–P2 (77.59(2)°) and C(1)–Ni–C(3) (71.13(9)°) angles,
2. Results and discussion
The synthesis of the cationic complexes 4–6 has been
carried out as outlined on Scheme 1. The oxidative ad-
dition of p-(trifluoromethyl)benzyl chloride to the Ni
(cod)(P–P) complexes afford the corresponding neutral
g1-benzyl derivatives 1–3 as dark orange–red crystals.
The reaction is straightforward for the dippe and dippp
complexes 2 and 3, since the Ni(0) compounds can be
generated in situ from Ni(cod)2 and the appropriate
diphosphine. However, very pure samples of Ni
(dippm)(cod) and a careful control of the experimental
conditions are required for the preparation of 1 (see
Section 4). When THF solutions of 1–3 are treated with
NaBPh4, a rapid color change from dark orange to
bright orange–yellow takes place, and the corresponding
cationic compounds 4–6 are produced in good yields.
These cationic derivatives are stable in the solid state for
extended periods of time, a valuable property for cata-
lytic applications. In contrast with the NMR spectra of
the g1-benzyl precursors, which display broad features
at room temperature, those of 4–6 exhibit sharp signals,
that are in accord with the g3-coordination mode pro-
posed for the benzyl ligand [9]. For example, the
methylene 13C resonance is shifted by more than 10 ppm
Fig. 1. View of the molecular structure of the cationic part of complex
4 together with the atomic numbering system. Selected bond distances
ꢁ
(A) and angles (°): Ni–C(1) 1.981(2), Ni–C(2) 2.044(2), Ni–C(3)
2.185(2), Ni–P(1) 2.1430(6), Ni–P(2) 2.2015(6), C(1)–C(2) 1.421(3),
C(2)–C(3) 1.420(3), C(2)–C(7) 1.422(3); C(1)–Ni–C(3) 71.13(9), C(1)–
Ni–P(1) 97.90(7), P(1)–Ni–P(2) 77.59(2), P(2)–Ni–C(3) 113.42(6),
C(1)–C(2)–C(3) 117.6(2), Ni–C(3)–C(2) 65.11(11), P(1)–C(9)–P(2)
95.30(11). Angle between planes C(1)–C(2)–C(3) and Ni–P(1)–P(2)–
C(1)–C(3): 72.45(1).
Cl
iPr
iPr
iPr iPr
iPr iPr
+
P
P
P
P
CF3
-
(CH2)n
iPr
Ni
iPr
(CH2)n
Ni
(CH2)n
Ni
CF3
BPh4
P
P
Cl
NaBPh4
iPr iPr
iPr iPr
CF3
n = 1, 1; 2, 2; 3, 3.
n = 1, 4; 2, 5; 3, 6.
Scheme 1.

I. Albers et al. / Journal of Organometallic Chemistry 689 (2004) 833–839
835
which are imposed by the g3-benzyl and dippm ligands.
Notwithstanding this, bond distances within the
pseudoallylic unit are comparable to those found in
other structurally characterized pseudoallylic complexes
of Ni [8c,9,10b,10d], and provide no evidence for a
weakening of the metal-ligand p interaction. In fact, the
interaction between the pseudoallyl ligand and the metal
center appears to be more symmetrical than usual in this
type of complex (e.g., the C(1)–C(2) and C(2)–C(3) bond
ꢁ
distances are identical (1.421(3) and 1.420(3) A), sug-
gesting that g3-coordination could be somewhat more
favoured in cationic benzylnickel compounds than in
related neutral derivatives.
The catalytic activity of complexes 4–6 has been tes-
ted in CH2Cl2 and THF, at a constant ethylene pressure
of 4 bar, in the absence of any cocatalyst. Table 1
summarizes the results of these reactions. As the cata-
lysts display low to moderate activities, the experiments
were conducted over long periods of time (24 h), with
continuous monitoring of the ethylene consumption.
Preliminary experiments showed that changes in the
ethylene pressure within the 2–8 bar range have little
impact on the activity of the three catalysts. The cata-
lytic activity of 5 and 6 is at its maximum nearby 40 °C
(entries 3–6), but catalyst 4 becomes rapidly deactivated
at this temperature in CH2Cl2.
In all cases, the consumption of ethylene was pre-
ceded by an induction period of up to 180 min. Similar
induction periods have been observed in ethylene olig-
omerization reactions catalyzed by Ni complexes, and
have been attributed to the slow rate of the first ethylene
insertion reaction, leading to the active species [12]. This
time interval is followed by a period of 18–20 h of eth-
ylene consumption, which may show spells of inactivity,
probably as a consequence of the slowness of the acti-
vation process, which seems to be comparable to the
catalyst life time. Since the activation period and the life
time of the catalyst are different in each experiment,
instead of using absolute productivities, the catalytic
activities should be better expressed in terms of the
maximum activity achieved (calculated from the slope of
the consumption curves) or as the average value ex-
tended over the time during which the catalyst remains
active.
As can be seen in Table 1, the catalytic activities are
strongly influenced by the size of the polymethylene
spacer of the diphosphine ligands. Thus, the dippm
complex 4 is significantly more active than the dippe and
dippp derivatives, 5 and 6, respectively. This result is not
entirely unexpected, as ligands with small bite angles
have been found to give high activities in other Ni-based
oligomerization or polymerization systems [13]. The
three catalysts retain a significant activity even in a po-
tentially coordinating solvent such as THF.
The bite angle of the diphosphine also affects
the molecular weight of the products. While the dippp

836
I. Albers et al. / Journal of Organometallic Chemistry 689 (2004) 833–839
derivative, 6, only produces C4–C22 oligomers with a
Schulz–Flory distribution curve characterized by
a ¼ 0:46 (as determined by GC), compounds 4 and 5
catalyze the formation of low molecular weight poly-
ethylenes, the higher molecular weight being produced
by the latter catalyst. The 1H NMR spectra of the
oligomers or polymers display signals in the 4.8–5.9 ppm
region, due to terminal or internal vinyl groups. The
intensities of these signals allow Mn estimations that are
consistent with the values obtained from GPC mea-
surements. In addition, the 1H and 13C NMR spectra of
the polymers obtained with 3 and 4 reveal that these are
slightly branched (5–15 Me groups/1000 C).
The polymers obtained in THF display somewhat
larger number of branches and lower Mn than those
produced in CH2Cl2. This effect might be due to THF
coordination to Ni, since it is known that SHOP olig-
omerization catalysts can shift their activity to poly-
merization when strong ligands (e.g., PPh3) are removed
from the reaction medium. A second difference between
the products obtained in CH2Cl2 and THF relates to the
generation in the latter solvent of a significant fraction
of soluble oligomers, especially in the case of 4. As the
polydispersity of the polyethylene insoluble fraction
does not depend appreciably upon the solvent used
(Mw=Mn ¼ 1:8–2:0), the formation of soluble oligomers
in THF suggests a bimodal molecular weight distribu-
tion of the product, even though the higher molecular
weight fraction separates because of its lower solubility.
The formation of oligomers increases at lower temper-
atures, and thus the GPC curve of the product obtained
from 4 at 25 °C in THF displays two peaks with
Mn ¼ 3162 and 794, respectively, due to incomplete
separation of the abundant low-molecular weight frac-
tion. The bimodal molecular weight distribution sug-
gests that in donor solvents the catalyst may operate
through two competing mechanisms.
the polymerization reaction and to improve the activity
of the catalysts are currently under way.
4. Experimental
Microanalyses were performed by the Analytical
ꢀ
Service of the Instituto de Investigaciones Quımicas.
The spectroscopic instruments used were Bruker Model
Vector 22 for IR spectra, and Bruker DPX-300, DRX-
400 and DRX-500 for NMR spectroscopy. The 13C
resonance of the solvent was used as an internal stan-
dard, but chemical shifts are reported with respect to
SiMe4. The 13C{1H} NMR assignments were helped in
all cases with the use of gate-decoupling and two di-
mensional techniques. 31P{1H} NMR shifts are refer-
enced to external 85% H3PO4. All preparations and
other operations were carried out under oxygen-free
nitrogen by conventional Schlenck techniques. Solvents
were dried and degassed before use. The phosphines
PMe3, Pri2PCH2CH2Pr2i (dippe) and Pri2PCH2CH2
CH2PPri2 (dippp) were prepared according to literature
methods.
5. Ni(g1-CH2C6H4-p-CF3)Cl(dippm), 1
(a) Synthesis of Ni(dippm)(cod): 0.26 ml (1mmol) of
dippm were added to a suspension of 275 mg (1 mmol)
of Ni(cod)2 in 30 ml of toluene, cooled at )80 °C. The
mixture was stirred at room temperature for 1 h and
the solvent was evaporated under reduced pressure. The
residue was extracted with 30 ml of Et2O and filtered.
After concentration and cooling to )20 °C, pale yellow
crystals of the complex Ni(dippm)(cod) were obtained.
Yield: 43%. Anal. Calc. for C21H42P2Ni: C, 60.8; H,
10.2. Found: C, 60.7; H, 10.2. 1H NMR (C6D6, 20 °C) d
1.04 (m, 24H, CH3), 1.82 (t, 2H, 2JHP ¼ 6.8 Hz, CH2–P),
2.36 (m, 4H, CH), 1.77 (m, 4H, CHH), 2.56 (m, 4H,
CHH) 4.85 (s, 4H, @CH); 31P{1H} NMR (C6D6 20 °C)
d 17.2 (s); 13C{1H} NMR (C6D6, 20 °C) d 18.7 (s, CH3),
3. Conclusions
The cationic g3-benzylcomplexes [Ni(g3-CH2C6H4-
p-CF3)(P–P)]þ BPh4ꢀ 4–6 catalyze the oligomerization
and/or polymerization of ethylene with moderate activ-
ity. The catalytic activity and the molecular weight of
the products produced by these complexes are depen-
dent on the bite angle of the diphosphine ligand at-
tached to the metal center. Thus, the ligand dippp with
the widest bite angle gives rise to oligomers, whereas the
dippe and dippm complexes produce low molecular
weight polymers. The activity of the dippm complex is
significantly higher than those of the dippe and dippp
ligands. The ethylene uptake curves reveal that the start
of the catalytic process is preceded by an induction pe-
riod that suggests the existence of a slow initiation
process. Further studies to determine the mechanism of
18.9 (s, CH3), 25.9 (t, JCP ¼ 14 Hz, CH2), 26.3 (t,
1
3
1JCP ¼ 6 Hz, CH), 32.1 (t, JCP ¼ 4 Hz, CH2), 77.5 (t,
2JCP ¼ 3 Hz, ¼ CH).
(b) Synthesis of 1: To a solution of 207 mg (0.50 mol)
of Ni(dippm)(cod) in 5 ml of toluene at )80 °C, 75 ll
(0.50 mmol) of p-trifluoromethylbenzyl chloride were
added. The mixture was stirred for 24 h at room tem-
perature and the solvent was evaporated to dryness. The
residue was extracted with Et2O, filtered and the solu-
tion concentrated under reduced pressure and cooled to
)20 °C. Complex 1 was collected in ꢁ60% yield as an
orange powder, although the samples were always con-
taminated with minor amounts (less than 5%) of un-
known impurities that could not be removed by
recystallization. 1H NMR (C6D6, 20 °C) d 0.91 (dd,

I. Albers et al. / Journal of Organometallic Chemistry 689 (2004) 833–839
837
3
3
1
12H, JHP ¼ 20.1 Hz, JHH ¼ 6.6 Hz, CH3), 1.10 (dd,
126.1 (q, JCF ¼ 271 Hz, CF3), 130.2 (s, CarH), 151.0 (s,
Car).
3
3
12H, JHP ¼ 15.8 Hz, JHH ¼ 7.1 Hz, CH3), 1.24 (t, 2H,
2JHP ¼ 8.4 Hz, CH2), 1.72 (m, 4H, CH), 2.70 (s, 2H,
3
CH2), 7.41 (d, 2H, JHH ¼ 8.1 Hz, CarH), 7.76 (d,
2H, 3JHH ¼ 8.0 Hz, CarH); 31P{1H} NMR (C6D6, 20 °C)
d )11.3 (bs), 8.7 (bs); 13C{1H} NMR (C6D6, 20 °C) d
16.4 (t, 1JCP ¼ 18 Hz, CH2), 17.8 (s, CH3), 18.8 (s, CH3),
7. Synthesis of complex [Ni(g3-CH2C6H4-p-CF3)
(P^P)]þ[BPh4]ꢀ (P^P = dippm, 4; dippe, 5; dippp, 6)
1
19.6 (m, CH2), 24.2 (d, JCP ¼ 9 Hz, CH), 24.3 (d,
To a cooled ()78 °C) solution of Ni(g3-CH2C6H4-p-
CF3)(Cl)(P^P) (1 mmol) in 80 ml of anhydrous THF
was added NaBPh4 (340 mg, 1 mmol). After stirring at
room temperature for 1 h the solvent was removed in
vacuo. The resulting yellow solid was extracted with
dichloromethane and this solution was centrifuged to
remove the NaCl, taken to dryness and the solid re-
crystallized.
1JCP ¼ 9 Hz, CH), 123.4 (q, JCF ¼ 32 Hz, Car-CF3),
2
1
124.6 (s, CarH), 126.1 (q, JCF ¼ 271 Hz, CF3), 128.4 (s,
CarH), 154.3 (s, Car).
6. Ni(g1-CH2C6H4-p-CF3)Cl(P^P) (P^P = dippe, 2;
dippp, 3)
4: Orange crystals, recrystallized from dichlorome-
thane. 72% yield. Anal. Calc. for C45H56BF3P2Ni: C,
68.8; H, 7.2. Found: C, 68.5; H, 7.3. 1H NMR (CD2Cl2,
To a suspension of Ni(cod)2 (275 mg, 1 mmol) in
toluene (50 ml) cooled at )78 °C, the appropriate di-
phosphine (dippe: 0.31 ml, 1 mmol or dippp: 0.29 ml, 1
mmol) was added, and the mixture was stirred for 15
min at room temperature. p-Trifluromethylbenzyl chlo-
ride (0.15 ml, 1 mmol) was then added, and the mixture
stirred overnight. The solvent was pumped off and the
residue extracted with Et2O. The volume was reduced
under vacuum and the concentrated solution is kept at
)20 °C until crystallization.
3
3
20 °C) d 1.01 (dd, 6H, JHP ¼ 17.4 Hz, JHH ¼ 7.4 Hz,
3
3
CH3), 1.10 (dd, 6H, JHP ¼ 16.7 Hz, JHH ¼ 7.1
3
3
Hz, CH3), 1.27 (dd, 6H, JHP ¼ 18.0 Hz, JHH ¼ 7.2 Hz,
3
3
CH3), 1.28 (dd, 6H, JHP ¼ 17.1 Hz, JHH ¼ 7.0 Hz,
CH3), 2.00 (m, 2H, CH), 2.32 (m, 2H, CH), 2.50 (dd,
2H, 2JHP ¼ 5.9, 5.3 Hz, CH2), 2.55 (t, 2H, 2JHP ¼ 9.6 Hz,
CH2–P), 6.25 (d, 2H, 3JHH ¼ 7.3 Hz, CarH), 7.83 (d, 2H,
3JHH ¼ 7.9 Hz, CarH); 31P{1H} NMR (CD2Cl2 20 °C)
AX spin system, dA ¼ 3:8, dX ¼ 20:3, JAX ¼ 43 Hz;
13C{1H} NMR (CD2Cl2, 20 °C) d 18.9 (s, CH3), 19.0 (s,
CH3), 20.9 (t, 1JCP ¼ 21 Hz, CH2), 24.9 (d, 1JCP ¼ 13 Hz,
CH), 26.7 (d, 1JCP ¼ 18 Hz, CH), 37.3 (bd, 2JCP ¼ 20 Hz,
CH2), 111.4 (d, JCP ¼ 7 Hz, CarH), 119.7 (s, Car), 128.6
2: Dark orange crystals, 63% yield. Anal. Calc. for
C22H38ClF3P2Ni: C, 51.2; H, 7.4. Found: C, 50.8; H,
7.1. 1H NMR (C6D6, 20 °C) d 1.14 (dd, 6H, 3JHP ¼ 12.5
3
Hz, JHH ¼ 7.0 Hz, CH3), 1.31 (m, 18H, CH3), 1.40 (m,
2H, CH2), 1.69 (m, 2H, CH2), 2.24 (m, 2H, CH), 2.33
3
1
(m, 2H, CH), 2.40 (t, 2H, JHP ¼ 6.7 Hz, CH2), 7.28 (d,
(q, JCF ¼ 32 Hz, Car-CF3), 133.1 (s, CarH), 124.1 (q,
3
3
2H, JHH ¼ 8.1 Hz, CarH), 7.52 (d, 2H, JHH ¼ 8.0 Hz,
CarH); 31P{1H} NMR (C6D6, 20 °C) AX spin system,
dA ¼ 74:6, dX ¼ 84:8, JAX ¼ 16 Hz; 13C{1H} NMR
1JCF ¼ 273 Hz, CF3).
5: Orange crystals, recrystallized from CH2Cl2/Et2O.
82% yield. Anal. Calc. for C46H58BF3P2Ni: C, 69.1; H,
7.3. Found: C, 68.7; H, 7.4. 1H NMR (CD2Cl2, 20 °C) d
0.83 (dd, 6H, 3JHP ¼ 17.2 Hz, 3JHH ¼ 7.2 Hz, CH3), 1.09
(dd, 6H, 3JHP ¼ 14.2 Hz, 3JHH ¼ 7.0 Hz, CH3), 1.17 (dd,
1
2
(C6D6, 20 °C) d 17.8 (dd, JCP ¼ 19 Hz, JCP ¼ 11 Hz,
CH2), 18.6 (s, CH3), 18.7 (s, CH3), 20.0 (d, 2JCP ¼ 3 Hz,
CH3), 20.5 (s, CH3), 23.1 (t, JCP ¼ 24 Hz, CH2), 24.7 (d,
1JCP ¼ 18 Hz, CH), 26.0 (d, 1JCP ¼ 25 Hz, CH), 20.1 (dd,
3
3
6H, JHP ¼ 15.4 Hz, JHH ¼ 7.0 Hz, CH3), 1.51 (dd, 6H,
2JCP ¼ 65, 26 Hz, CH2), 123.6 (q, JCF ¼ 32 Hz, Car-
3JHP ¼ 17.1 Hz, JHH ¼ 7.2 Hz, CH3), 1.61 (m, 2H,
2
3
1
CF3), 124.2 (d, JCP ¼ 3 Hz, CarH), 125.8 (q, JCF ¼ 271
CH2), 1.90 (m, 4H, CH2 and CH), 2.34 (m, 2H, CH),
2.70 (t, 2H, 3JHP ¼ 4.2 Hz, CH2), 6.23 (d, 2H, 3JHH ¼ 7.7
Hz, CF3), 128.9 (d, JCP ¼ 2 Hz, CarH), 153.9 (s, Car).
3: Purple crystals, 60% yield. Anal. Calc. for
C23H40ClF3P2Ni: C, 52.2; H, 7.6. Found: C, 51.9; H,
7.2. 1H NMR (CD2Cl2, 20 °C) d 0.54 (m, 3H, CH3), 0.72
(m, 3H, CH3), 1.00 (m, 16H, CH3 and CH2), 1.15 (m,
8H, CH3 and CH2), 1.18 (m, 2H, CH), 2.10 (m, 2H,
Hz, CarH), 7.86 (d, 2H, JHH ¼ 7.9 Hz, CarH); 31P{1H}
3
NMR (CD2Cl2, 20 °C) d 84.8 (s), 77.2 (s); 13C{1H}
NMR (CD2Cl2, 20 °C) d 18.6 (s, CH3), 18.9 (s, CH3),
19.5 (d, 2JCP ¼ 4 Hz, CH3), 19.5 (m, CH2), 19.7 (s, CH3),
1
2
22.9 (dd, JCP ¼ 26 Hz, JCP ¼ 13 Hz, CH2), 24.7 (d,
1JCP ¼ 23 Hz, CH), 27.7 (d, 1JCP ¼ 27 Hz, CH), 40.4 (dd,
2JCP ¼ 209 Hz, CH2), 110.8 (s, CarH), 119.8 (s, Car),
3
CH), 2.78 (d, 2H, JHP ¼ 2.8 Hz, CH2), 7.44 (d, 2H,
3
3JHH ¼ 8.2 Hz, CarH), 7.85 (d, 2H, JHH ¼ 8.1 Hz,
1
2
CarH); 31P{1H} NMR (CD2Cl2 20 °C) AX spin system,
dA ¼ 16:6, dX ¼ 25:8, JAX ¼ 41 Hz; 13C{1H} NMR
(CD2Cl2, 20 °C) d 16.6 (m, CH2), 17.5 (s, CH3), 17.7 (m,
CH2), 17.8 (s, CH3), 19.3 (s, CH3), 19.9 (s, CH3), 21.1 (s,
CH2), 23.9 (d, 1JCP ¼ 21 Hz, CH), 25.5 (d, 1JCP ¼ 25 Hz,
124.0 (q, JCF ¼ 272 Hz, CF3), 129.0 (q, JCF ¼ 40 Hz,
Car-CF3), 133.0 (s, CarH).
6: Orange crystals, recrystallized from acetone. Yield
52%. Anal. Calc. for C47H60BF3P2Ni: C, 69.4; H, 7.4.
Found: C, 69.4; H, 7.4. 1H NMR (CD2Cl2, 20 °C) d 0.77
(dd, 6H, 3JHP ¼ 17.1 Hz, 3JHH ¼ 7.3 Hz, CH3), 1.04 (dd,
2
CH), 23.1 (dd, JCP ¼ 63, 27 Hz, CH2), 124.0 (q,
3
3
2JCF ¼ 32 Hz, Car-CF3), 124.4 (d, JCP ¼ 3 Hz, CarH),
6H, JHP ¼ 13.4 Hz, JHH ¼ 6.9 Hz, CH3), 1.15 (dd, 6H,

838
I. Albers et al. / Journal of Organometallic Chemistry 689 (2004) 833–839
3
3JHP ¼ 16.4 Hz, JHH ¼ 7.2 Hz, CH3), 1.15 (dd, 6H,
Table 2
Crystal data and structure refinement for 4
3
3JHP ¼ 15.2 Hz, JHH ¼ 7.0 Hz, CH3), 1.30 (m, 2H,
Identification code
Empirical formula
Formula weight
Temperature
Ear1as
CH2–P), 1.44 (m, 2H, CH2–P), 1.63 (m, 2H, CH), 1.75
(m, 2H, CH2), 2.16 (m, 2H, CH), 2.70 (t, 2H, 3JHP ¼ 4.3
C45H56BF3NiP2
785.36
100(2) K
3
Hz, CH2), 6.20 (d, 2H, JHH ¼ 7.6 Hz, CarH), 7.75 (d,
2H, JHH ¼ 7.9 Hz, CarH); 31P{1H} NMR (CD2Cl2 20
3
ꢁ
0.71073 A
Wavelength
°C) AX spin system, dA ¼ 15:9, dX ¼ 35:2, JAX ¼ 30 Hz;
Crystal system
Space group
Unit cell dimensions
Orthorhombic
P 21 21 21
13C{1H} NMR (CD2Cl2, 20 °C) d 16.3 (dd, JCP ¼ 23
1
3
1
Hz, JCP ¼ 3 Hz, CH2–P), 17.9 (dd, JCP ¼ 21 Hz,
3JCP ¼ 6 Hz, CH2–P), 18.2 (s, CH3), 18.8 (s, CH3), 20.3
(s, CH3), 20.5 (d, 2JCP ¼ 5 Hz, CH3), 21.3 (s, CH2), 25.5
ꢁ
a (A)
¼ 9.5884(5)
¼ 19.5775(10)
¼ 22.3413(12)
¼ 90°
ꢁ
b (A)
ꢁ
c (A)
1
1
(d, JCP ¼ 24 Hz, CH), 29.5 (d, JCP ¼ 28 Hz, CH), 40.6
a
b
(dd, 2JCP ¼ 19, 10 Hz CH2), 112.1 (d, JCF ¼ 4 Hz, CarH),
¼ 90°
1
c
Volume
¼ 90°
119.5 (s, Car), 124.3 (q, JCF ¼ 273 Hz, CF3), 129.7 (q,
3
ꢁ
4193.8(4) A
2JCF ¼ 31 Hz, Car-CF3), 132.6 (d, JCF ¼ 3 Hz, CarH).
Crystal data for 4: C45H56BF3P2Ni, Mr ¼ 785.36, red
prism (0.44 ꢂ 0.37 ꢂ 0.34 mm) crystallized from CH2Cl2,
orthorhombic, space group P 21 21 21 (no. 19),
Z
4
1.244
0.582 mmꢀ1
1664
0.44 ꢂ 0.37 ꢂ 0.34 mm3
Density (calculated) (Mg/m3)
Absorption coefficient
F (0 0 0)
Crystal size
Theta range for data collection 1.38–28.64°
ꢁ
ꢁ
ꢁ
a ¼ 9:5884ð5Þ A, b ¼ 19:5775ð10Þ A, c ¼ 22:3413ð12Þ A,
V ¼ 4193:8ð4Þ A , Z ¼ 4, Dx ¼ 1:244 Mg/m3,
k
3
ꢁ
Index ranges
ꢀ12 <¼ h <¼ 12,
ðMo KaÞ ¼ 0:71073 A, l ¼ 0:58 mmꢀ1, T ¼ 100ð2Þ K.
X-ray diffraction data were collected on a Bruker
SMART diffractometer equipped with a APEX CCD
detector, graphite monochromated Mo Ka radiation,
and a Kryoflex low-temperature device. Four sets of
frames covering a hemisphere of the reciprocal space
were recorded (606, 435, 230 y 100 frames to u ¼
0°; 90°; 180° and 0 ° respectively, x-scans, Dx ¼ 0:3°,
time per frame 10 s). Data reduction up to h ¼ 30° by
program SAINT, corrections for absorption with pro-
gram SADABS, 27707 reflections measured, 9862 inde-
pendent, Rint ¼ 0:035215a. Structure solution with direct
methods and program SHELXS97, structure refinement
on F 2 using program SHELXL97 [14b].
ꢁ
ꢀ21 <¼ k <¼ 25,
ꢀ20 <¼ l <¼ 30
27,707
Reflections collected
Independent reflections
9862 [Rint ¼ 0:0352]
Completeness to theta ¼ 28.64 94.5%
Absorption correction
Semi-empirical from
equivalents
0.8275 and 0.7838
Maximum and minimum
transmission
Refinement method
Full-matrix least-squares on F 2
9862/9/657
0.928
Data/restraints/parameters
Goodness-of-fit on F 2
Final R indices [I > 2rðIÞ]
R indices (all data)
R1 ¼ 0:0380, wR2 ¼ 0:0648
R1 ¼ 0:0470, wR2 ¼ 0:0669
)0.004(8)
Absolute structure parameter
ꢀ3
ꢁ
Largest different peak and hole 0.591 and )0.257 e A
The asymmetric unit of the structure is formed by one
mononuclear cationic complex of the p-benzyl Nick-
el(II) and one anionic molecule of tetraphenylborate.
The trifluoromethyl group in the cationic complex p-
benzyl Nickel(II) was observed disordered in two posi-
tions and the occupancy factors for these two disordered
moieties were refined with complementary occupancy
factors 0.713/0.287.
parameter x ¼ ꢀ0:004ð8Þ. The highest residual peak,
ꢁꢀ3
ꢁꢀ3
0.589 e A , and deepest hole, )0.256 e A , were
located close to the heavier atom Ni and have no
chemical sense (Table 2).
8. Polymerization of ethylene by complexes 4–6
All non-hydrogen atoms were refined with aniso-
tropic displacement parameters but some geometric re-
straints (DFIX command) were necessary for the
fluorine–carbon bonds. All the hydrogen atoms were
included in the refinement from observed positions and
refined, first with free isotropic displacement parame-
ters, and later with free positional and thermal param-
eters; except for the methyl hydrogens that were
included from calculated positions and refined riding on
the atoms, which they are bonded with isotropic thermal
parameters. Final refinement with 9862 data, nine re-
straints, and 657 parameters gave R1 ¼ 0:0470, wR2 ¼
0:0670 (all data), and R1 ¼ 0:0380, wR2 ¼ 0:0649 ½I >
2rIÞꢃ, (S ¼ 0:928). Absolute structure parameter, Flack
General procedure for the polymerization of ethylene
of complexes 4–6: A solution of 25 lmol of the corre-
sponding complex (4, 5 or 6) in 2 ml of THF (entries 1,
3, 5 and 7) or dichlorometane (entries 2, 4, 6 and 8) was
prepared and stored under a nitrogen atmosphere. This
solution was added to a pressure reactor that contained
18 ml of the same solvent under an ethylene pressure of
4 bars and maintained at the work temperature. The
solution was stirred for 24 h, during which time the
ethylene consumption was monitored continuously.
Polymerization was terminated by shutting off the eth-
ylene supply. The supernatant liquid was analyzed by
GC and the insoluble polymer formed was filtered off,

I. Albers et al. / Journal of Organometallic Chemistry 689 (2004) 833–839
839
[7] J. Ledford, C.S. Shultz, D.P. Gates, P.S. White, J.M. DeSimone,
M. Brookhart, Organometallics 20 (2001) 5266.
dried and weighed. The solvent was then evaporated and
the residue was transferred to a vial, and weighed.
[8] (a) M. Brookhart, L.K. Johnson, C.M. Killian, S.D. Arthur, J.
Feldman, E.F. McCord, S.J. McLain, K.A. Kreutzer, A.M.A.
Bennett, E.B. Coughlin, S.D. Ittel, A. Parthasarathy, D.J. Tempel,
WO Patent Application 9623010 to Dupont, April 3, 1995;
(b)
9. Supporting information available
J.R. Ascenso, A.R. Dias, P.T. Gomes, D. Neibecker, A. Revillon,
~
C.C. Romao, I. Tkatchenko, Makromol. Chem. 190 (1989)
Crystallographic data for the structural analysis have
been deposited with the Cambridge Crystallographic
Data Centre, CCDC 228266 for Compound 4. Copies of
this information may be obtained free of charge from The
Director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK (Fax: +44-1223-336033; e-mail: deposit@ccdc.cam.
ac.uk or www: http://www.ccdc.cam.ac.uk).
2773
(c) J.R. Ascenso, M.A.A.C.T. Carrondo, A.R. Dias, P.T. Gomes,
ꢀ ~
M. Fatima, M. Piedade, C.C. Romao, Polyhedron 8 (1989)
2449.
[9] (a) E. Carmona, M. Paneque, M.L. Poveda, Polyhedron 8 (1989)
285;
ꢀ
(b) J. Campora, E. Carmona, E. Gutierrez, P. Palma, M.L.
Poveda, C. Ruiz, Organometallics 11 (1992) 11;
ꢀ
ꢀ
(c) J. Campora, E. Gutierrez, M.L. Poveda, C. Ruiz, E. Carmona,
J. Chem. Soc., Dalton Trans. (1992) 1769;
ꢀ
Acknowledgements
ꢀ
(d) E. Carmona, J.M. Marın, M. Paneque, M.L. Poveda,
Organometallics 6 (1987) 1757;
Financial support from DGSIC (Project BQU2000-
1169) and the European Commission (contract HPRN-
CT-2000-00010) are gratefully acknowledged. C.M.M.
ꢀ
ꢀ
(e) J. Campora, E. Gutierrez, P. Palma, M.L. Poveda, C. Ruiz, E.
Carmona, Organometallics 11 (1992) 2644;
ꢀ
(f) E. Carmona, J.M. Marın, P. Palma, M. Paneque, M.L.
Poveda, Organometallics 4 (1985) 2053;
ꢀ
thanks the Direccion General de Ensenanza Superior for
a PFPI studentship.
~
ꢀ
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(g) J. Campora, E. Gutierrez, A. Monge, M.L. Poveda, C. Ruiz,
E. Carmona, Organometallics 12 (1993) 4025;
(h) O. Bountry, M.C. Nicasio, M. Paneque, E. Carmona,
J. Organomet. Chem. 444 (1993) 245;
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