[Bis(amido)cyclodiphosph(III)azane]dichlorozirconium complexes for ethene polymerization

Article abstract of DOI:10.1002/ejic.200400296

A series of new zirconium dichloride complexes bearing bulky cis-bis(amino)cyclodiphosph(III)azane ligands, [(RN)₂-(tBuNP) ₂]ZrCl₂ [R = phenyl (7), diphenylmethyl (8), 2,6-diethylphenyl (9), 2,5-di-tert-butylphenyl (10), and 2,6-diisopropylphenyl (11)] were prepared in high yields by a two-step synthetic route. The structure of cis-[(Ph₂CHN)-(tBuNP)]₂Zr(NMe₂)₂ (8a), determined by X-ray analysis, shows that the zirconium atom has a distorted trigonal-bipyramidal configuration consisting of four equidistant metal-amido nitrogen bonds and an additional coordination between the metal and a nitrogen atom from the cyclodiphosph(III)azane ring. After methylaluminoxane activation, these complexes exhibit moderate to high activities in ethene polymerization and produce high molar mass polyethene (M_w up to 1100 kg/mol). Polymerization experiments reveal that the behavior of bis(amido)cyclodiphosph(III)azane-based Zr^IV catalysts depends on the nature and steric bulkiness of the amido substituents, reaction temperature, MAO/zirconium ratio, as well as monomer pressure. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004).

Full text of DOI:10.1002/ejic.200400296

FULL PAPER
[Bis(amido)cyclodiphosph(III)azane]dichlorozirconium Complexes for Ethene
Polymerization
Kirill V. Axenov,[a] Martti Klinga,[a] Markku Leskelä,[a] Vasily Kotov,[b] and Timo Repo*[a]
Keywords: Zirconium / Polymerization / Homogeneous catalysis
A series of new zirconium dichloride complexes bearing
bulky cis-bis(amino)cyclodiphosph(III)azane ligands, [(RN)2-
phosph(III)azane ring. After methylaluminoxane activation,
these complexes exhibit moderate to high activities in ethene
(tBuNP)2]ZrCl2 [R = phenyl (7), diphenylmethyl (8), 2,6-di- polymerization and produce high molar mass polyethene
ethylphenyl (9), 2,5-di-tert-butylphenyl (10), and 2,6-diiso- (Mw up to 1100 kg/mol). Polymerization experiments reveal
propylphenyl (11)] were prepared in high yields by a two- that the behavior of bis(amido)cyclodiphosph(III)azane-based
step synthetic route. The structure of cis-[(Ph2CHN)-
ZrIV catalysts depends on the nature and steric bulkiness of
(tBuNP)]2Zr(NMe2)2 (8a), determined by X-ray analysis, the amido substituents, reaction temperature, MAO/zirco-
shows that the zirconium atom has a distorted trigonal-bipyr-
amidal configuration consisting of four equidistant
metal−amido nitrogen bonds and an additional coordination
between the metal and a nitrogen atom from the cyclodi-
nium ratio, as well as monomer pressure.
( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2004)
Introduction
cene polymerization catalysts,[22Ϫ25] we have developed a
straightforward synthesis towards new [bis(amido)cyclodi-
phosph()azane]TiIV complexes bearing sterically hindered
aryl substituents and investigated them as ethene polymeri-
zation catalysts.[26] After MAO activation, these Ti com-
plexes were able to polymerize ethene with moderate ac-
tivity and produce polymers with high molar mass and nar-
row molar mass distribution (MMD). Here we describe an
efficient synthetic route to the new [bis(amido)cyclodi-
phosph()azane]Zr complexes and report on the results of
an investigation of their catalytic behavior in ethene
polymerization as well as on the properties of the pro-
duced polymers.
Group 4 metal complexes bearing bi- or tridentate[1Ϫ7]
diamido ligands have attracted considerable attention as a
new generation of early transition metal based polymeri-
zation catalysts.[8,9] After methylaluminoxane (MAO) acti-
vation, highly electrophilic 10-electron cationic species,
[(R2N)2ZrR]ϩ, which serve as active catalytic sites, form.[8]
This type of nonmetallocene complex has the advantage
that the electronic character, geometry and steric hindrance
of the catalytic center can be easily controlled through
rational ligand design. To date, an impressive number of
transition metal complexes have been synthesized[8,9] and
applied for α-olefin polymerization,[10Ϫ13] in particular eth-
ene polymerization.[14Ϫ17]
Recently, novel bis(amido) complexes of Group 4 metals
based on the cyclodiphosph()azane framework were
reported.[18Ϫ21] Due to the fact that these complexes possess
a tetrahedral coordination of the metal center and the chlo-
ride ions are in a cis position, they can be considered as
potential catalyst precursors for olefin polymerization. As
an augmentation to our previous studies on nonmetallo-
[a]
Department of Chemistry, Laboratory of Inorganic Chemistry, Results and Discussion
University of Helsinki,
P. O. Box 55, 00014 Finland
Synthesis of Ligand Precursors
Fax: (internat.) ϩ 358 9-19150198
E-mail: timo.repo@helsinki.fi
[b]
A series of cyclodiphosph()azanes, 1Ϫ5, were prepared
in high yields by reaction of the appropriate anilines with
dichlorocyclodiphosph()azane a in the presence of excess
Et3N, as was reported earlier (Scheme 1).[26] The X-ray
Department of Chemistry, CB#3290 Venable Hall, The
University of North Carolina at Chapel Hill,
Chapel Hill, NC 27599-3290, USA
Supporting information for this article is available on the
WWW under http://www.eurjic.org or from the author.
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DOI: 10.1002/ejic.200400296
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[Bis(amido)cyclodiphosph(III)azane]dichlorozirconium Complexes
FULL PAPER
Scheme 1
analysis (solid state) and NMR spectroscopic data have
shown that these compounds favor a cis conformation Ϫ
the most desirable arrangement for coordination chemistry
applications. The solid-state structure of cis-[(Ph2CHNH)-
(tBuNP)]2 (2, Figure 1, Tables 1 and 2) also supports the
previously observed cis orientation of the bulky amino sub-
stituents. However, this structure differs sharply from pre-
viously reported structures for cis-bis(amino)cyclodi-
phosph()azanes; according to X-ray crystallographic
analysis, the NH groups in all other known cyclodi-
phosph()azanes[27,28] adopt the endo orientation relative
Table 1. Crystallographic data for 2 and 8a
2
8a
Empirical formula
Formula mass
Space group
C34H42N4P2
568.66
P1
C38H52N6P2Zr
746.02
P21/n
10.715(2)
20.287(4)
18.055(4)
¯
˚
a [A]
10.449(1)
12.419(1)
13.493(1)
75.39(1)
73.57(1)
74.65(1)
1589.5(2)
1.188
˚
b [A]
˚
c [A]
α [°]
β [°]
γ [°]
96.31(3)
3
˚
to the PϪN ring, while in 2 these substituents have the V [A ]
3900.9(14)
1.270
4
dcalcd. [g cmϪ3
]
exo,endo orientation (Figure 1). Such an unusual structural
feature has been reported earlier for cis-[(tBuNH)-
(tBuNPS)]2 with PV only.[29] Furthermore, the distortion of
the PϪN ring is diminished as indicated by the PϪN bond
lengths and the planarity of the ring. It can be assumed
that the reduced ring distortion is mainly a consequence of
the unique exo,endo orientation.
Z
2
µ [cmϪ1
]
14.52
1.54179
193(2)
0.053
0.1549
3.98
˚
λ [A]
0.71073
173(2)
0.0927
0.2060
T [K]
R[a]
[b]
Rw
[a] R ϭ Σ(Fo Ϫ Fc)/ΣFo for observed reflections [I Ͼ 2σ(I)]. [b] Rw ϭ
2
2 2
2 2
{Σ[w(Fo Ϫ Fc ) ]/Σ[w(Fo ) ]}1/2 for all data.
Synthesis of Complexes
The most common synthetic route to the transition metal
complexes that have an anionic ligand is a transmetalation
reaction. According to this general strategy, cis-
[(PhNH)(tBuNP)]2 (1) and cis-[(2,6-di-iPrC6H3NH)2(t-
BuNP)2] (5) ligands were first deprotonated with BuLi, and
the obtained Li salts were then treated with ZrCl4 in toluene
at Ϫ78 °C. The resulting reaction mixtures were analyzed
by 31P NMR spectroscopy. When ligand 1 was used, only
one product (δP ϭ 145 ppm, see Supporting Information)
was observed. The same transformation with ligand 5 leads
to a complex mixture of unidentified products. According
to data published previously, the signal at δ ϭ 145 ppm is
assigned to the ZrIV complex that has two cyclodi-
phosph()azane ligands attached to the metal center.[20] In
Figure 1. ORTEP plot of 2 with thermal ellipsoids drawn at 50%
probability level; all hydrogen atoms are omitted for clarity
Eur. J. Inorg. Chem. 2004, 4702Ϫ4709
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K. V. Axenov, M. Klinga, M. Leskelä, V. Kotov, T. Repo
FULL PAPER
corners of a zirconium-centered tetrahedron (Figure 2). In
Table 2. Selected structural parameters for compounds 2 and 8a
general, all amidoϪzirconium bonds are equidistant (aver-
˚
Compound 2
age 2.110 A), while the ZrϪN coordination bond is signifi-
˚
Distances [A]
P1ϪN4
P2ϪN3
P2ϪN4
P1ϪP2
Angles [°]
˚
cantly longer (2.448 A) (Tables 1 and 2). The NϪMϪN
1.727(2)
1.722(2)
1.728(2)
2.5957(9)
1.677(2)
1.468(3)
1.486(3)
1.468(3)
N3ϪP1ϪN4
P1ϪN3ϪP2
P1ϪN4ϪP2
C1ϪN3ϪP1
C5ϪN4ϪP1
N2ϪP2ϪN4
N2ϪP2ϪN3
C9ϪN1ϪP1
C22ϪN2ϪP2
81.20(10)
97.52(11)
97.41(11)
angles range from 100° to 123.19°. The geometry of the
ligand moiety 2 is changed due to the coordination to the
126.59(16) zirconium atom, and the PϪN(amido) bonds adopt an
P2ϪN2
N3ϪC1
N4ϪC5
N1ϪC9
123.57(16)
107.96(10)
105.13(10)
122.51(17)
endo,endo orientation relative to the cyclodiphosph()-
azane ring. Overall, the ZrϪN coordination is similar to
those reported for cis-[(tBuN)2(tBuNP)2]ZrCl2 and cis-
[(PhN)2(tBuNP)2]2Zr.[20]
126.99(16)
Compound 8a
˚
Distances [A]
Angles [°]
P1ϪN3
P1ϪN4
P2ϪN2
N3ϪC1
N1ϪC9
Zr1ϪN1
Zr1ϪN2
Zr1ϪN3
Zr1ϪN51
1.773(7)
1.746(7)
1.702(7)
1.515(10)
1.467(9)
2.141(6)
2.113(7)
2.439(7)
2.046(7)
N61ϪZr1ϪN51
N61ϪZr1ϪN2
N51ϪZr1ϪN1
N2ϪZr1ϪN1
N61ϪZr1ϪN3
N51ϪZr1ϪN3
P2ϪN3ϪZr1
N3ϪP2ϪP4
100.0(3)
117.9(3)
106.7(2)
108.5(2)
104.8(3)
153.8(3)
92.0(3)
81.1(3)
97.9(4)
118.5(5)
P1ϪN3ϪP2
C9ϪN1ϪP1
fact, the salt metathesis route was unselective in the prep-
aration of corresponding titanium() bis(amido)complexes
also, and alternative synthetic routes were therefore looked
for.[26] As in the case of TiIV, the direct metalation of the
ligand precursors by amine elimination[17] appeared to be
Figure 2. ORTEP plot of 8a with thermal ellipsoids drawn at 50%
probability level; all hydrogen atoms are omitted for clarity
Ethene Polymerization
1
the most efficient method. According to H and 31P NMR
spectroscopic data, the reaction of Zr(NMe2)4 with 1Ϫ5
Despite a certain interest in cis-bis(amido)cyclodi-
leads selectively to the bis(amido)complexes [(RN)- phosph()azane-based zirconium complexes, few prelimi-
(tBuNP)]2Zr(NMe2)2 (7aϪ11a) (Scheme 1). nary reports concerning their polymerization properties
However, it is well known that bis(amido) early transition have been published.[18Ϫ20] In order to evaluate the influ-
metal complexes are less active catalyst precursors in poly- ence of the structure of the catalyst precursors on polymer-
merization of α-olefins than the corresponding dichloro de- ization properties, we carried out a detailed ethene polymer-
rivatives. Treatment of bis(amido)[cis-bis(amido)cyclodi- ization investigation. In general, MAO-activated zirconium
phosph()azane]zirconium complexes 7aϪ11a with excess complexes 6Ϫ11 reveal moderate to high catalytic activity
chlorotrimethylsilane in toluene selectively gave the desired and, according to obtained data, the size of the substituents
dichlorozirconium derivatives 7Ϫ11 in high yields at the amido nitrogen atoms has a significant effect on the
(Scheme 1). These complexes have been characterized by catalytic behavior (Table 3).
NMR spectroscopy, elemental analysis, and mass spectro-
Under the chosen polymerization conditions (50 °C and
scopic methods. According to the 1H NMR spectra, the 3.8 bars), 6/MAO bearing tert-butyl groups shows the high-
cis-[(RN)2(tBuNP)2]ZrCl2 complexes show C2 symmetry in est average activity in the series of catalysts (Entry 1,
solution and reveal the equivalence of all aromatic substitu- Table 3). When ethene polymerization is conducted under
ents.
the same conditions, there are two distinct differences in the
X-ray structures of [cis-bis(amido)cyclodiphosph()az- behavior of catalyst 6/MAO from that of its TiIV analog;
ane]zirconium complexes are rather rare, and only one the catalytic activity is significantly higher for 6/MAO as it
structure involving [bis(amido)cyclodiphosph()azane]- remains high during the whole polymerization reaction,
ZrX2-type complexes, namely cis-[(tBuN)2(tBuNP)2]ZrX2 while cis-[(tBuN)2(tBuNP)2]TiCl2/MAO gives a remarkably
(X ϭ Cl, 6),[18,20] has been reported. The crystals of cis- high initial activity that decreases drastically after a few
[(Ph2CHN)2(tBuNP)2]Zr(NMe2)2 (8a) suitable for X-ray minutes. In addition, 6/MAO produces polyethene with
analysis were successfully grown from a saturated Et2O narrow polydispersity, whereas the corresponding TiIV cata-
solution at Ϫ20 °C. In the structure of 8a the four amido lyst is prone to produce polyethylene with bimodal
NϪZr bonds and an additional coordination of the cyclodi- MMD.[26] These facts indicate the higher stability of the
phosph()azane ring nitrogen to the zirconium atom define [bis(amido)cyclodiphosph()azane]Zr catalytic species.
a rather distorted trigonal-bipyramidal configuration of the
Replacement of the tert-butyl groups with di-
metal center. The amido nitrogen atoms are located in the phenylmethyl (8) leads to dramatic changes in the catalyst
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[Bis(amido)cyclodiphosph(III)azane]dichlorozirconium Complexes
FULL PAPER
Table 3. Ethene polymerization data for complexes 6؊11
Entry[a]
Catalyst
Concentration
[µmol]
Reaction temp.
[°C]
Time
[min]
Yield
[g]
Activity[b]
Mw [g/mol]
Mw/Mn
Tm [°C]
1
2
3
4
5
6
6
7
1.5
10
10
10
10
10
50
50
50
50
50
50
30
30
30
30
30
30
5.8
24058
1031
973
1181
2534
7000
228 000
1 132 000
1 042 000
1 039 000
306 000
2.17
3.32
22.18
3.41
4.10
2.84
134
134
131
138
133
136
1.63
1.53
1.89
2.93
4.05
8
9
10
11
672 000
[a]
[b]
MAO (Al/M ϭ 1000), 200 mL of toluene, 3.8 bar of ethylene. kg PE/(molcat ϫ [C2H4] ϫ h).
behavior. The activity decreases substantially and the pro- the stability of these Zr catalysts. The tert-butyl substituents
duced polyethene has a high Mw (1040 kg/mol) and bimo- in 6/MAO seem to create a highly propitious environment
dal MMD (see Supporting Information). The series of cata- for the catalytically active center, and already at 30 °C a
lysts 7/MAO, 9/MAO, 10/MAO, and 11/MAO bearing phe- very high activity is observed. However, the activity de-
nyl, 2,6-diethylphenyl, 2,5-di-tert-butylphenyl, and 2,6-di- creases to one third when the temperature increases from
isopropylphenyl groups, respectively, reveal
a
clear 30 to 70 °C, whereas the molar mass of polyethene and
enhancement of activity with increased steric bulk on the the MMD are slightly enhanced (Figure 4). Polymerization
arylamido substituents. The activity as well as the proper- activities of the other catalysts are much lower but not as
ties of the polymer material are strongly connected to the sensitive to the temperature changes and show their highest
ligand design. The molar mass of polyethene varies between values at temperatures between 50 and 60 °C. At higher
230 and 1130 kg/mol and polymers with diverse MMDs temperatures deactivation of the catalytically active species
and different modalities are obtained.
occurs. Quite unexpectedly, the produced polyethene pos-
Reaction temperature as well as monomer concentration sesses maximum molar mass values at 50 °C. The decrease
are the key factors, which define the activity of catalysts in Mw at higher temperatures is often explained by a change
and also the properties of the polymers produced. Ethene in relative rates of chain propagation and β-H elimin-
was polymerized at 30, 50, 60, and 70 °C to evaluate the ation.[30] This seems to be a plausible explanation here as
influence of polymerization temperature on the catalytic ac- well. The lower Mw values at 30 °C remain unexplained but
tivity and polymer properties (Figure 3). The steric bulki- could be caused by another competing chain termination
ness of the amido substituents is crucial for the catalyst be- route, e.g. chain transfer to aluminum.
havior, in particular, the polymerization activity, as well as
Figure 4. Molar mass of polyethene as a function of polymerization
temperature with selected catalyst precursors [(tBuN)-
(tBuNP)]2ZrCl2 (6), [(2,6-Et2C6H3N)(tBuNP)]2ZrCl2 (9), and [(2,6-
iPr2C6H3N)(tBuNP)]2ZrCl2 (11); the numeric values of Mw (in kg/
mol) as well as polydispersities are given
Figure 3. Catalytic activity as a function of polymerization tem-
perature for [(tBuN)(tBuNP)]2ZrCl2 (6), [(PhN)(tBuNP)]2ZrCl2 (7),
[(Ph2CHN)(tBuNP)]2ZrCl2 (8), [(2,6-Et2C6H3N)(tBuNP)]2ZrCl2
(9), [(2,5-tBu2C6H3N)(tBuNP)]2ZrCl2 (10), and [(2,6-iPr2C6H3N)-
(tBuNP)]2ZrCl2 (11) as catalyst precursors; the numeric values of
the observed average activities are also given for the corresponding
graph points; activity is expressed as kg of PE ϫ (molcat ϫ [C2H4]
ϫ h)Ϫ1; experimental conditions used: MAO (Al/M ϭ 1000), 3.8
bar of ethylene
All cyclodiphosph()azane catalysts were tested with
ethene concentrations ranging from 0.15 to 0.8 mol/L (2Ϫ8
bar at 50 °C). The highest average productivity (calculated
from the yield of polymer) is 22 800 kg of PE/molcat ϫ h
for 6/MAO at 8 bar. The maximum catalytic activity for
6Ϫ10/MAO is reached at low ethene concentrations (Fig-
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K. V. Axenov, M. Klinga, M. Leskelä, V. Kotov, T. Repo
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Depending on the ligand structure, the catalysts have dif-
ferent responses to variations in MAO concentration e.g.
the polymerization activity of 6/MAO significantly de-
creases when the Al/Zr ratio increases (Figure 7). Even
though 6/MAO possesses a high polymerization activity, it
is vulnerable to higher temperatures and MAO concen-
trations. Hence, we assume that the tert-butyl groups of 6/
MAO are not bulky enough to protect the catalytic center
from deactivation. It has been proposed that the coordi-
nation of Lewis acidic MAO to the electron-pair-donating
PIII atoms in the cyclodiphosph()azane ring can initiate
the destruction of the catalyst during the polymerization
process.[19]
Figure 5. Catalytic activity of complexes as a function of ethene
concentration
for
[(tBuN)(tBuNP)]2ZrCl2
(6),
[(PhN)-
(tBuNP)]2ZrCl2 (7), [(Ph2CHN)(tBuNP)]2ZrCl2 (8), [(2,6-
Et2C6H3N)(tBuNP)]2ZrCl2 (9), [(2,5-tBu2C6H3N)(tBuNP)]2ZrCl2
(10), and [(2,6-iPr2C6H3N)(tBuNP)]2ZrCl2 (11) as catalyst precur-
sors; the numeric values of the observed average activities are also
given for the corresponding graph points; activity is expressed as
kg of PE ϫ (molcat ϫ [C2H4] ϫ h)Ϫ1; experimental conditions used:
MAO (Al/M ϭ 1000), polymerization temperature 50 °C
ure 5). It has been suggested that at higher monomer con-
centrations, due to enhanced polymer formation, the active
complex becomes quickly embedded in the swollen-gel-like
polymer matrix, which leads to the diffusion-controlled re-
action conditions.[31]
Despite the increased monomer pressure enhancing the
productivity of catalysts (yield of polymer), the molar mass
of polymers produced by 6/MAO and 11/MAO are slightly
reduced (Figure 6). This fact indicates the presence of β-
H transfer to the monomer as a major chain-termination
mechanism. However, in the case of 10/MAO, where aniline
is unsymmetrically substituted with tert-butyl substituents,
the dominating chain termination reaction changes from β-
H transfer to the monomer to β-H transfer to the metal
center as the molar mass of polyethene appreciably in-
creases from 310 kg/mol at 3.8 bar of ethene to 1480 kg/
mol at 8 bar.[32]
Figure 7. Catalytic activity of complexes as a function of MAO/Zr
ratio for [(tBuN)(tBuNP)]2ZrCl2 (6), [(PhN)(tBuNP)]2ZrCl2 (7),
[(Ph2CHN)(tBuNP)]2ZrCl2 (8), [(2,6-Et2C6H3N)(tBuNP)]2ZrCl2 (9),
[(2,5-tBu2C6H3N)(tBuNP)]2ZrCl2 (10), and [(2,6-iPr2C6H3N)-
(tBuNP)]2ZrCl2 (11) as catalyst precursors; the numeric values of
the observed average activities are also given for the corresponding
graph points; activity is expressed as kg of PE ϫ (molcat ϫ [C2H4]
ϫ h)Ϫ1; experimental conditions used: 3.8 bar of ethylene, poly-
merization temperature 50 °C
According to the polymerization results, diphenylmethyl
substituents are not able to provide a suitable surrounding
for the highly active metal center and, in addition, 8/MAO
is sensitive to increased MAO concentrations. Increasing
the size of substituents at the aniline moiety improves the
shielding at the cationic metal center, and the activity of 10/
MAO, with 2,5-di-tert-butylphenyl groups, is enhanced up
to an MAO/Zr ratio of 1000. In fact, the sterically most
demanding 2,6-diisopropylphenyl groups in 11/MAO ef-
ficiently protect the catalytically active site, and it is the
only catalyst that gradually enhances the polymerization ac-
tivity with increasing MAO/Zr ratio. While the bulky ligand
protects the catalytic species from destructive side reactions,
it also congests the actual polymerization site and the ob-
served activity for 11/MAO is thus lower than for 6/MAO.
Published solid-state structures (Figure 2[18Ϫ20,26]) of [bis-
(amido)cyclodiphosph()azane]Zr and -Ti complexes show
that the environment of the P atoms remains rather open
regardless of the changes in the bulkiness of the amino sub-
stituents. It appears in this study that the observed corre-
lation between the stability of the catalytically active species
Figure 6. Molar mass of polyethene as a function of ethene concen-
tration with selected catalyst precursors [(tBuN)(tBuNP)]2ZrCl2
(6),
[(2,5-tBu2C6H3N)(tBuNP)]2ZrCl2
(10),
and
[(2,6-
iPr2C6H3N)(tBuNP)]2ZrCl2 (11); the numeric values of Mw (in kg/
mol) as well as polydispersities are given
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[Bis(amido)cyclodiphosph(III)azane]dichlorozirconium Complexes
FULL PAPER
[(PhN)2(tBuNP)2]ZrCl2 (7): A solution of Zr(NMe2)4 (1.56 g,
5.86 mmol) in toluene (20 mL) was added with a syringe to a tolu-
ene solution of cis-[(PhNH)2(tBuNP)2] (2.28 g, 5.86 mmol, 30 mL)
at 0 °C. The reaction mixture was then refluxed for 16 h, and the
obtained bis(dimethylamido)zirconium complex [(PhN)(tBu-
NP)]2Zr(NMe2)2 (7a) was characterized by NMR spectroscopy. 1H
NMR (200 MHz, C6D6, 29°C): δH ϭ 1.19 (s, 18 H, tBu), 2.93 (s,
12 H, NMe2), 6.81 (t, J ϭ 6.6 Hz, 2 H, o-H), 7.26 (m, 8 H, Ph)
and the size of amido substituents could be better explained
if destructive MAO interaction with metalϪligand bonding
was the major decomposition pathway for the catalysts.
Conclusion
New [bis(amido)cyclodiphosph()azane]zirconium com- ppm. 13C{1H} NMR (50.3 MHz, C6D6, 29°C): δC ϭ 29.7 [t, JP,C ϭ
6.87 Hz, C(CH3)3], 40.94 (Me2NZr), 53.2 [t, JP,C ϭ 12.5 Hz,
C(CH3)3], 119.36 (Ph), 129.7 (Ph), 150.0 (Ph) ppm. 31P{1H} NMR
(162 MHz, C6D6, 21°C): δP ϭ 124 ppm. The bis(amido) complex
[(PhN)(tBuNP)]2Zr(NMe2)2 was converted into the corresponding
dichloro derivative 7 by reaction with excess Me3SiCl (1.3 g, 1.5
mL, 11.7 mmol) at 0 °C. The obtained reaction mixture was stirred
at room temperature overnight. The volatiles were removed in
vacuo, and the residue was extracted with a mixture of hexane and
CH2Cl2 (1:1). After filtration and evaporation of the solvents, the
product was dried in vacuo to give a pale-yellow powder containing
plexes [(RN)(tBuNP)]2ZrCl2 (7Ϫ11) [R ϭ Ph (7), Ph2CH
(8), 2,6-Et2C6H3 (9), 2,5-tBu2C6H3 (10), 2,6-iPr2C6H3 (11)]
were synthesized by reaction of the corresponding ligand
precursors with Zr(NMe2)4. The amido complexes were
successfully transformed into the dichloro derivatives
[(RN)(tBuNP)]2ZrCl2 (7Ϫ11) with excess Me3SiCl. MAO-
activated 7Ϫ11 display moderate to high activities in ethene
polymerization. The catalyst behavior is dependent on the
bulk of the ligand substituents. The nature and size of the
amido substituents play a great role in defining the catalytic 1 equiv. of Me2NH per Zr (2.03 g; 60%) C20H28Cl2N4P2Zr·Me2NH
(593.6): calcd. C 44.51, H 5.94, N 11.80; found C 44.79, H 6.19, N
11.44. 1H NMR (200 MHz, C6D6, 29°C): δH ϭ 1.32 (s, 18 H, tBu),
1.80 (br. s, Me2NH), 6.82 (t, J ϭ 7.7 Hz, 2 H, p-H), 7.09 (t, J ϭ
7.7 Hz, 4 H, m-H), 7.50 (d, J ϭ 7.7 Hz, 4 H, o-H) ppm. 13C{1H}
NMR (50.3 MHz, C6D6, 29°C): δC ϭ 28.65 [t, JP,C ϭ 7.4 Hz,
C(CH3)3], 32.2 (Me2NH), 54.25 [t, JP,C ϭ 9.15 Hz, C(CH3)3], 124.0,
activity of the investigated Zr complexes as well as the poly-
mer properties. From the series of catalysts studied here,
only 11/MAO revealed increased activity in the range
500Ϫ2000 for the MAO/Zr ratio as well as in the polymeri-
zation temperature range 30Ϫ60°C.
129.5, 150.2 ppm. 31P{1H} NMR (162 MHz, C6D6, 21°C): δP
145.03 (s) ppm. MS(EI): m/z (%) ϭ 548 (10) [Mϩ], 503 (6) [Mϩ
Cl], 388 (10) [ligand].
ϭ
Ϫ
Experimental Section
[(Ph2CHN)2(tBuNP)2]ZrCl2 (8): A toluene solution of Zr(NMe2)4
(0.52 g, 1.97 mmol, 20 mL) was added with a syringe to a solution
of cis-[(Ph2CHNH)2(tBuNP)2] (1.12 g, 1.97 mmol) in toluene (10
mL) at 0 °C. The reaction mixture was then refluxed for 16 h, and
the bis(dimethylamido)zirconium complex [(Ph2CHN)2(tBuNP)2]-
Zr(NMe2)2 (8a) was isolated according to a procedure described
earlier. 1H NMR (200 MHz, C6D6, 29°C): δH ϭ 1.30 (s, 18 H, tBu),
2.70 (12 H, NMe2), 5.57 (dd, 2 H, Ph2CH), 7.09 (m, 20 H, Ph-H)
ppm. Crystals suitable for X-ray analysis were obtained by slow
crystallization from saturated Et2O solution at Ϫ20 °C. The bis-
(amido) complex [(Ph2CHN)2(tBuNP)2]Zr(NMe2)2 (8a) was con-
verted into the corresponding dichloro derivative 8 by reaction with
excess Me3SiCl (2.31 g, 2.0 mL, 21.28 mmol) at 0 °C. The obtained
reaction mixture was stirred at room temperature overnight. The
volatiles were removed in vacuo, and the residue was extracted with
a mixture of hexane and CH2Cl2 (1:1). The crude product was
washed with cold pentane and dried under vacuum (yield 0.95 g).
The remaining pentane solution was kept in a freezer at Ϫ20 °C
for 3 d, and a second crop of product (0.27 g) was isolated as a
white powder by removing the pentane with a syringe. Total yield
1.22 g, 85%. C34H40Cl2N4P2Zr (728.8): calcd. C 56.03, H 5.53, N
7.69; found C 55.85, H 6.30, N 7.50. 1H NMR (200 MHz, C6D6,
29°C): δH ϭ 1.21 (s, 18 H, tBu), 6.08 (t, 2 H, Ph2CH), 7.14Ϫ7.28
(m, 16 H, Ph), 7.68 (d, J ϭ 7.0 Hz, 4 H, p-H) ppm. 13C{1H} NMR
(50.3 MHz, C6D6, 29°C): δC ϭ 30.88 [t, JP,C ϭ 7.25 Hz, C(CH3)3],
51.88 [t, JP,C ϭ 11 Hz, C(CH3)3], 98.4 (Ph2CH), 126.85 (Ph), 128.6
(Ph), 150.8 (Ph) ppm. 31P{1H} NMR (162 MHz, C6D6, 21°C): δP ϭ
102.0 (s) ppm. MS(EI): m/z (%) ϭ 691 (5) [Mϩ Ϫ Cl], 566 (60)
[ligand].
General Remarks: All manipulations were performed under argon
in a glovebox or using standard Schlenk techniques. Hydrocarbon
and ether solvents were refluxed in the presence of sodium and
benzophenone, distilled, and stored under an inert gas in the pres-
ence of sodium flakes. Dichloromethane was refluxed in the pres-
ence of CaH2 powder and distilled before use. Mass spectra were
measured with a JEOL SX102 spectrometer and the 1H and 13C
NMR spectra were recorded with a Varian Gemini 200 MHz spec-
1
trometer. The H and 13C NMR spectra are referenced relative to
CHCl3 (δ ϭ 7.24 ppm and 77.0 ppm, respectively) and C6D5H (δ ϭ
7.15 ppm and 128.0 ppm, respectively). 31P NMR spectra were col-
lected with a Bruker AMX 400 spectrometer and phosphorus sig-
nals were referenced relative to an external 85% H3PO4 solution.
Elemental analyses were performed by Analytische Laboratorien
Prof. Dr. H. Malissa, G. Reuter GmbH, Lindlar, Germany. High-
temperature gel permeation chromatography of polyethylene
samples (GPC) was performed in 1,2,4-trichlorobenzene at 145 °C
using a Waters HPLC 150C. tert-Butylamine and phosphorus tri-
chloride were purchased from Merck and purified by distillation
under argon (tBuNH2 from sodium hydroxide). Arylamines and
diphenylmethylamine were received from Aldrich and distilled in
vacuo from sodium hydroxide before use. Chlorotrimethylsilane
was purchased from Fluka and used as received. Zr(NMe2)4 was
purchased from Aldrich and used as a toluene solution. Methylalu-
minoxane (MAO, 30 wt.% solution in toluene) was received from
Borealis Polymers Oy.
Ligand Synthesis: cis-[Cl(tBuNP)]2 (a) was prepared according to
modified literature procedures.[29] The cyclodiphosph()azane li-
gands cis-[(PhNH)(tBuNP)]2 (1), cis-[(Ph2CHNH)2(tBuNP)2] (2),
cis-[(2,6-di-EtC6H3NH)2(tBuNP)2] (3), cis-[(2,5-di-tBuC6H3NH)2-
[(2,6-Et2C6H3N)2(tBuNP)2]ZrCl2 (9): A toluene solution of cis-
(tBuNP)2] (4), and cis-[(2,6-di-iPrC6H3NH)2(tBuNP)2] (5) were pre- [(2,6-Et2C6H3NH)2(tBuNP)2] (1.5 g, 3.0 mmol, 20 mL) and
pared as described previously.[26] [(tBuN)2(tBuNP)2]ZrCl2 (6) was
Zr(NMe2)4 (0.8 g, 2.99 mmol) in toluene (10 mL) was treated as
in the case of 8. The bis(dimethylamido)zirconium complex [(2,6-
prepared according to the literature.[18]
Eur. J. Inorg. Chem. 2004, 4702Ϫ4709
www.eurjic.org
 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
4707

K. V. Axenov, M. Klinga, M. Leskelä, V. Kotov, T. Repo
FULL PAPER
Et2C6H3N)2(tBuNP)2]Zr(NMe2)2 (9a) was isolated according to a 12 H, NMe2), 3.92 [m, 4 H, (CH3)2CH], 7.0Ϫ7.3 (6 H, Ar) ppm.
previously described procedure. 1H NMR (200 MHz, C6D6, 29°C):
δH ϭ 1.33 (s, 18 H, tBu), 1.40 (t, 12 H, CH3CH2), 3.03 and 3.19
31P{1H} NMR (162 MHz, C6D6, 21°C): δP ϭ 115.45 (s) ppm. Me3-
SiCl (4.5 mL, 3.8 g, 35 mmol) was added with a syringe to a toluene
(2 s, 12 H, NMe2), 3.08 (q, 8 H, CH3CH2), 7.16 (m, 6 H, Ar) ppm. solution of [(2,6-iPr2C6H3N)2(tBuNP)2]Zr(NMe2)2 at 0 °C. The re-
Me3SiCl (4.8 mL, 4.15 g, 38.2 mmol) was added with a syringe to
a stirred solution of [(2,6-Et2C6H3N)2(tBuNP)2]Zr(NMe2)2. The re-
action mixture was stirred at room temperature overnight. The sol-
vent was removed under vacuum. An orange residue was first ex-
tracted with hexane (30 mL) and then twice with a mixture of hex-
action mixture obtained was stirred at room temperature overnight.
The product (yellow oil) was isolated as in the case of 9. Yield
2.28 g, 92.3%. C32H52Cl2N4P2Zr (716.9): calcd. C 53.61, H 7.31, N
7.82; found C 53.50, H 7.17, N 7.80. 1H NMR (200 MHz, C6D6,
29°C): δH ϭ 1.37 (s, 18 H, tBu), 1.42 [d, 24 H, (CH3)2CH], 3.97
ane (20 mL) and CH2Cl2 (7 mL). After solvent evaporation, the [m, J ϭ 6.96 Hz, 4 H, (CH3)2CH], 7.12Ϫ7.28 (6 H, Ar) ppm.
obtained dichloro complex was dried under vacuum to give the
yellow-orange oil (1.6 g, 80.8%). C28H44Cl2N4P2Zr (660.8): calcd.
13C{1H} NMR (50.3 MHz, C6D6, 29°C): δC ϭ 24.17 [t, J ϭ 1 Hz,
(CH3)2CH], 31.37 [t, JP,C ϭ 6.7 Hz, (CH3)3C], 32.2 [d, J ϭ 0.8 Hz,
(CH3)2CH], 51.8 [t, JP,C ϭ 14.6 Hz, (CH3)3C], 123.3 (Ar), 124.0
1
C 50.90, H 6.71, N 8.48; found C 50.47, H 7.06, N 8.64. H NMR
(200 MHz, C6D6, 29°C): δH ϭ 1.41 (s, 18 H, tBu), 1.49 (t, 12 H, (Ar), 128.3 (Ar), 141 (Ar) ppm. 31P{1H} NMR (162 MHz, C6D6,
CH3CH2), 3.16 (q, J ϭ 7.69 Hz, 8 H, CH3CH2), 7.20Ϫ7.33 (m, 6
21°C): δP ϭ 115.47 (s) ppm. MS(EI): m/z (%) ϭ 716 (3) [Mϩ], 681
H, Ar) ppm. 13C{1H} NMR (50.3 MHz, C6D6, 29°C): δC ϭ 14.92 (2) [Mϩ Ϫ Cl], 556 (20) [ligand].
(t, J ϭ 1.53 Hz, CH3CH2), 26.4 (d, J ϭ 9.9 Hz, CH3CH2), 31.23
Polymerization Experiments: A 1-L Büchi glass autoclave (or a steel
[t, JP,C ϭ 6.48 Hz, C(CH3)3], 51.53 [t, JP,C ϭ 14.5 Hz, C(CH3)3],
123.3 (Ar), 127.1 (Ar), 135.75 (Ar), 138.13 (t, J ϭ 1.9 Hz, Ar) ppm.
31P{1H} NMR (162 MHz, C6D6, 21°C): δP ϭ 115.6 (s) ppm.
MS(EI): m/z (%) ϭ 661 (1) [Mϩ], 626 (3) [Mϩ Ϫ Cl], 500 (80)
[ligand].
autoclave at a pressure of 8 bar) was charged with dry toluene
(200 mL), cocatalyst (MAO), and thermostatted to the required
temperature. The autoclave was saturated with ethylene, and a de-
sired amount of precatalyst solution was then injected. The mono-
mer pressure (Ϯ50 mbar), temperature (Ϯ0.5 °C), and monomer
consumption were controlled by real-time monitoring. Polymeriz-
ation was quenched with 10% HCl solution in methanol, and the
polymer precipitated quantitatively by pouring the solution into
methanol (400 mL), acidified with a small amount of aqueous hy-
drochloric acid. The polymer materials obtained were washed sev-
eral times with methanol and water, and dried at 60 °C. The poly-
[(2,5-tBu2C6H3N)2(tBuNP)2]ZrCl2 (10): A toluene solution of cis-
[(2,5-tBu2C6H3NH)2(tBuNP)2] (2.29 g, 3.74 mmol, 30 mL) was
treated with Zr(NMe2)4 (1.0 g, 3.74 mmol) in toluene (10 mL) as
in the case of 8. The obtained bis(dimethylamido)zirconium com-
plex [(2,5-tBu2C6H3N)2(tBuNP)2]Zr(NMe2)2 (10a) was charac-
1
terized by NMR spectroscopy. H NMR (200 MHz, C6D6, 29°C):
merization activities were calculated as kg of PE ϫ (molcat
ϫ
δH ϭ 1.44 (s, 36 H, tBuAr), 1.57 (s, 18 H, tBu), 3.03Ϫ3.28 (12 H,
NMe2), 7.0 (dd, J1 ϭ 6.2, J2 ϭ 2.2 Hz, 2 H, 4-HPh), 7.35 (2 H, 3-
HPh), 8.25 (dd, J1 ϭ 3.1, J2 ϭ 2.2 Hz, 2 H, 2-HPh) ppm. 13C{1H}
NMR (50.3 MHz, C6D6, 29°C): δC ϭ 31.0 [5-(CH3)3CAr], 31.34 [t,
[C2H4] ϫ h)Ϫ1 from experimental data to adjust the changes in the
ethene concentration in toluene. The values of [C2H4] for different
ethene pressures and polymerization temperatures were taken
from ref.[33]
JP,C
ϭ 6.48 Hz, (CH3)3C], 31.54 [2-(CH3)3CAr], 33.11 [5-
(CH3)3CAr], 33.3 [2-(CH3)3CAr], 43.8 (NMe2), 51.7 [t, JP,C
ϭ
X-ray Crystallographic Study: The crystal data of cis-
[(Ph2CHNH)2(tBuNP)2] (2) were collected with an EnrafϪNonius
CAD-4 single-crystal diffractometer at 193(2) K using Cu-Kα radi-
13.7 Hz, (CH3)3C], 113.85 (Ar), 114.5 (Ar), 117.17 (Ar), 127.0 (Ar),
141.9 (Ar), 150.0 (t, J ϭ 1.15 Hz, Ar) ppm. 31P{1H} NMR
(162 MHz, C6D6, 21°C): δP ϭ 99.8 (s) ppm. Me3SiCl (5.1 mL,
4.34 g, 40 mmol) was added with a syringe to a toluene solution of
[(2,5-tBu2C6H3N)2(tBuNP)2]Zr(NMe2)2. The reaction mixture was
stirred at room temperature overnight. All volatiles were removed
under vacuum. The residue was extracted three times with a mix-
ture of hexane (30 mL) and CH2Cl2 (20 mL). The extracts were
combined and the solvent was removed in vacuo. The product, a
yellow powder, was dried under vacuum. Yield 2.4 g, 83%.
C36H60Cl2N4P2Zr (773.0): calcd. C 55.94, H 7.82, N 7.25; found C
˚
ation (graphite monochromator), λ ϭ 1.54179 A (scan type ω/2θ).
Intensities were corrected for Lorentz and polarization effects and
for absorption, XCAD4.[34Ϫ36] The crystal data of
[(Ph2CHN)2(tBuNP)2]Zr(NMe2)2 (8a) were collected with a Nonius
KappaCCD area-detector diffractometer at 173(2) K using Mo-Kα
˚
radiation (graphite monochromator), λ ϭ 0.71073 A. Data re-
duction: COLLECT.[37] Absorption correction: SADABS.[38] Solu-
tion and refinement: SHELX-97,[39] direct methods. All non-hydro-
gen atoms were refined anisotropically. Hydrogen atoms were re-
fined in calculated positions. The displacement factors of the H
atoms were 1.2 ϫ (1.5 ϫ) that of the host atom. Graphics:
SHELXTL/PC.[40] CCDC-231525 and -231526 contain the sup-
plementary crystallographic data for this paper. These data can be
obtained free of charge at www.ccdc.cam.ac.uk/conts/retriev-
ing.html [or from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 1EZ, UK; Fax: ϩ 44-1223-336-033;
E-mail: deposit@ccdc.cam.ac.uk].
55.16, H 8.52, N 7.96. 1H NMR (200 MHz, C6D6, 29°C): δH
ϭ
1.44 (s, 36 H, tBuAr), 1.57 (s, 18 H, tBu), 7.0 (dd, 2 H, J1 ϭ 6.22,
J2 ϭ 2.2 Hz, 4-HPh), 7.36 (2 H, 3-HPh), 8.25 (2 H, J1 ϭ 3.3, J2 ϭ
2.2 Hz, 2-HPh) ppm. 13C{1H} NMR (50.3 MHz, C6D6, 29°C):
δC ϭ 31.0 [5-(CH3)3CAr], 31.34 [t, JP,C ϭ 6.6 Hz, (CH3)3C], 31.54
[2-(CH3)3CAr], 33.1 [5-(CH3)3CAr], 33.7 [2-(CH3)3CAr], 51.7 [t,
JP,C ϭ 13.73 Hz, (CH3)3C], 113.8 (Ar), 114.5 (Ar), 117.15 (Ar),
136.95 (Ar), 140.7 (Ar), 150.0 (t, J ϭ 1.53 Hz, Ar) ppm. 31P{1H}
NMR (162 MHz, C6D6, 21°C): δP ϭ 99.8 (s) ppm. MS(EI): m/z
(%) ϭ 772 (40) [Mϩ], 735 (20) [Mϩ Ϫ Cl], 612 (90) [ligand].
Acknowledgments
[(2,6-iPr2C6H3N)2(tBuNP)2]ZrCl2 (11): A toluene solution of cis-
[(2,6-iPr2C6H3NH)2(tBuNP)2] (1.91 g, 3.44 mmol, 20 mL) was
treated with Zr(NMe2)4 (0.92 g, 3.44 mmol) in toluene (10 mL) as
in the case of 8. The bis(dimethylamido)zirconium complex [(2,6-
iPr2C6H3N)2(tBuNP)2]Zr(NMe2)2 (11a) obtained was charac-
Support of this work by CIMO and Academy of Finland (decision
no.: 0204408) is gratefully acknowledged.
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Eur. J. Inorg. Chem. 2004, 4702Ϫ4709

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