Linked cyclopentadienyl-amido complexes of zirconium; Ligand dependence of cation-anion interactions and ethene polymerisation activity

Article abstract of DOI:10.1016/S1381-1169(97)00168-4

A range of zirconium dichloride complexes [C₅H₄(CH₂)(η)NR]ZrCl₂ (n = 2, R = iPr, tBu; n = 3, R = Me, Et, iPr) with linked cyclopentadienyl-amide ancillary ligands were prepared by amine elimination routes. Their dibenzyl derivatives [C₅H₄(CH₂)(η)NR]Zr(CH₂Ph)₂ react with B(C₆F₅)₃ to give the ionic species {[C₅H₄(CH₂)(ν)NR]Zr(CH₂Ph)} [PhCH₂B(C₆F₅)3]. In bromobenzene solvent, the position of the equilibrium between the solvent-separated ion pair and the species in which the anion is η⁶-coordinated to the metal centre through the B-benzyl phenyl group is strongly dependent on ligand bridge length and substitution. This gives an indication of the overall steric requirement of the ligand system. The activity of the [C₅H₄(CH₂)(n)NR]ZrCl₂/methylaluminoxane catalysts in the homopolymerisation of ethene was probed. The [C₅H₄(CH₂)(n)NiPr]Zr-system found to be several times more efficient for n = 3 than for n=2, with the [C₅H₄(CH₂)₃NMe]Zr-system being the most active of the compounds studied.

Full text of DOI:10.1016/S1381-1169(97)00168-4

Ž
.
Journal of Molecular Catalysis A: Chemical 128 1998 143–153
Linked cyclopentadienyl–amido complexes of zirconium; ligand
dependence of cation–anion interactions and ethene
polymerisation activity
)
Piet-Jan Sinnema, Koert Liekelema, Oetze K.B. Staal, Bart Hessen , Jan H. Teuben
Centre for Catalytic Olefin Polymerisation, UniÕersity of Groningen, Department of Chemistry, Nijenborgh 4,
9747 AG Groningen, The Netherlands
Abstract
w
Ž
.
x
Ž
.
A range of zirconium dichloride complexes C5H4 CH2 nNR ZrCl2 ns2, RsiPr, tBu; ns3, RsMe, Et, iPr with
linked cyclopentadienyl–amide ancillary ligands were prepared by amine elimination routes. Their dibenzyl derivatives
w
Ž
.
x
Ž
.
Ž
.
Äw
Ž
.
x
Ž
.4
C5H4 CH2 nNR Zr CH2 Ph
react with B C6 F5
to give the ionic species
C5 H4 CH2 n NR Zr CH2 Ph
2
3
w
Ž
. x
PhCH2B C6F5 . In bromobenzene solvent, the position of the equilibrium between the solvent-separated ion pair and the
3
species in which the anion is h6-coordinated to the metal centre through the B-benzyl phenyl group is strongly dependent on
ligand bridge length and substitution. This gives an indication of the overall steric requirement of the ligand system. The
w
Ž
.
x
activity of the C5H4 CH2 nNR ZrCl2rmethylaluminoxane catalysts in the homopolymerisation of ethene was probed. The
w
w
Ž
.
x
C5H4 CH2 nNiPr Zr-system found to be several times more efficient for n s 3 than for n s 2, with the
Ž
.
x
C5H4 CH2 3NMe Zr-system being the most active of the compounds studied. q 1998 Elsevier Science B.V.
w x
use of the C5Me4SiMe2 NtBu-ligand 3,4 al-
lows a ready and random incorporation of
comonomer over a wide compositional range. It
1. Introduction
Linked cyclopentadienyl–amido ligands of
Ž
.
Ž
.
the type Cp- bridge -amido have been highly
successful in combination with group 4 transi-
tion metals to give catalyst systems for the
copolymerisation of ethene with a-olefins, when
is suggested that the small Cp CT –M–N angle
enforced by the ligand system is responsible for
Ž
.
this property ‘constrained geometry catalyst’ ,
thus reducing the steric hindrance on a specific
Ž
w x
used in conjunction with MAO methyl-
side of the metal centre 5 .
.
aluminoxane or perfluoroarylborate-derived ac-
tivators for the generation of the catalytically
active cationic alkyl species 1,2 . Especially the
One feature of the linked Cp-amido ligand
system is that it is relatively straightforward to
vary independently various ligand features, such
as bridge length and amide or cyclopentadienyl
substitution pattern, thus making studies of lig-
and structure–catalyst property relationships
possible. Earlier our group developed a rela-
w
x
)
Corresponding author. Fax: q 31-50-3634296;
e-mail: b.hessen@chem.rug.nl
1381-1169r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.
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.
PII S1381-1169 97 00168-4

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144
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
Scheme 1.
tively simple route for the synthesis of the
combinations in the catalytic homopolymerisa-
tion of ethene.
Ž
.
–
3
– CH2
bridged cyclopentadienyl–methyl-
amide ligand and for the attachment of this
ligand to zirconium by an amine elimination
w x
reaction 6 . We have now prepared a range of
2. Synthesis of the complexes
w
Cp–amide zirconium complexes C 5H 4
Ž
.
x
Ž
Ž . Ž
The ligands C5H5 CH2 nNHR ns2; Rs
CH2 nNR ZrCl2 ns2; RsiPr, tBu; ns3,
.
.
iPr, tBu; ns3, RsMe, Et, iPr were obtained
RsMe, Et, iPr which allows a systematic
Ž
.
study of their properties.
conveniently by reaction of Br CH2 nNHRP
A useful spectroscopic ‘probe’ for the total
of steric restrictions imposed by the ligand that
is relatively independent of electronic factors
can be provided by the strength of the cation–
anion interaction in well-defined cationic species
derived from these complexes. The interaction
HBr with an excess of CpNa, as described
w x
before for the ns3, RsMe derivative 6 . The
corresponding zirconium dichloride complexes
w
Ž
.
x
C5H4 CH2 nNR ZrCl2 were prepared accord-
Ž
.
ing to two amine elimination routes Scheme 1 .
Ž
.
Reaction of the ligand with Zr NMe2 Cl2
2
w
Ž
.
x
Ž
.
w x
of the PhCH2 B C6F5 3 -anion with the cationic
metal centre generated by the reaction of
THF 9 in toluene at 758C followed by subli-
2
mation of the crude product afforded pure
Ž
.
w
Ž . x
B C6F5 3 with transition-metal benzyl com-
plexes is sensitive to the steric hindrance around
the metal centre. For example, in the reaction
C5H4 CH2 nNR ZrCl2 for ns2, RsiPr, tBu
and n s 3, R s iPr. For n s 3, R s Me,
Ž
.
Ž
.
Ž
.
products of C5R5 Zr CH2 Ph with B C6F5 3
3
Table 1
the phenyl group of the anion is h6-bound to the
1
w
Ž
.
x
Ž
H-NMR data for C5H4 CH2 nNR ZrCl2 300 MHz, CDCl3, d
.
in ppm
w x
metal centre for RsH 7 , whereas for RsMe
the product exists in solution as a solvent-sep-
arated ion pair 8 .
We prepared the dibenzyl zirconium com-
plexes C5H4 CH2 nNR Zr CH2 Ph
RsiPr, tBu; ns3, RsMe, Et, iPr and stud-
ied their reactions with B C6F5 3. Cation–anion
interactions were studied by NMR spectroscopy
and showed a clear dependence on ligand bridge
length and substitution pattern. This relation is
discussed, together with the catalytic properties
n, R
Cp
NCH2 –CH2 – Cp–CH2 R, a R, b
4.12 3.02 4.43 1.13
6.6
4.09
w x
2, iPr
6.3
6.3
Ž
.
Ž
.
Ž
.
Ž
.
6.6
6.3
6.3
2, tBu 6.38
2.92
1.25
w
Ž
.
x
Ž
.
Ž
n s 2;
Ž
.
Ž .
6.6
2
.
6.32
6.6
3, Me
3, Et
6.46
6.05
6.52
6.02
6.52
5.98
2.95
2.92
2.85
2.17
2.15
2.09
2.80
2.81
2.79
3.27
3.81
Ž
.
1.21
Ž
Ž
.
Ž
Ž
.
6.5
6.5
1.23
.
5.9
3, iPr
4.86
.
5.9
Ž
.
Multiplicities according to assignment, coupling constants Hz in
parentheses.
w
Ž
.
x
of representative C5H4 CH2 nNR ZrCl2rMAO

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P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
145
Table 2
13
w
Ž
.
x
Ž
.
C-NMR data for C5H4 CH2 nNR ZrCl2 75.4 MHz, CDCl3, d in ppm
n, R
Cp ipso
Cp CH
N–CH2
63.34
–CH2–
Cp–CH2
28.76
R, a
49.13
R, b
19.05
2, iPr
141.75
115.53
111.70
Ž
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
Ž
.
.
Ž
Ž
Ž
Ž
Ž
.
Ž
.
Ž
.
173.4
174.6
136.7
129.4
124.5
127.0
2, tBu
3, Me
3, Et
141.46
127.64
128.03
127.98
115.53
113.46
64.98
29.42
57.66
27.24
.
.
Ž
Ž
Ž
Ž
.
.
Ž .
125.7
173.4
174.6
135.5
130.6
114.17
112.31
55.85
26.01
28.95
37.24
.
.
.
Ž
Ž
Ž
.
.
Ž
Ž
Ž
.
176.6
172.1
134.9
128.2
127.0
135.5
114.48
112.20
51.27
26.31
29.83
42.93
12.69
.
.
.
.
.
.
Ž
Ž
.
174.6
171.0
134.9
128.2
127.0
130.6
127.4
3, iPr
114.67
112.01
44.28
26.54
30.47
46.27
19.65
.
127.4
.
.
.
.
.
.
173.4
172.1
134.3
128.8
127.6
116.0
Ž
.
Multiplicities according to assignment, coupling constants Hz in parentheses.
Table 3
1
w
Ž
.
x
Ž
.
Ž
.
H-NMR data for C5H4 CH2 nNR Zr CH2 Ph 300 MHz, C6 D6, d in ppm
2
n, R
Cp
NCH2
–CH2–
Cp–CH2
R, a
R, b
0.94
ZrCH2
Ph o-H
6.58
Ph m-H
Ph p-H
2, iPr
5.72
5.27
3.48
2.44
3.57
1.67
1.05
7.12
6.94
Ž
Ž
.
Ž
Ž
.
Ž
6.1
.
Ž
6.1
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
6.6
6.6
7.4
7.4
7.3
Ž
9.2
.
2, tBu
3, Et
5.57
5.47
3.35
2.24
1.13
1.94
1.43
6.70
7.11
6.93
.
.
.
.
.
6.6
6.6
7.2
7.3
7.3
Ž
.
10.3
5.60
5.39
2.45
2.50
1.53
1.58
2.21
2.23
3.05
1.00
1.62
1.22
6.61
7.11
6.94
Ž
6.5
.
Ž
Ž
.
.
.
.
6.5
7.3
7.3
7.3
Ž
Ž
.
9.5
3, iPr
5.59
5.30
4.00
1.12
1.86
1.01
6.70
7.14
6.95
.
7.3
Ž
5.8
.
.
.
.
5.8
7.4
7.4
.
9.5
Ž
.
Multiplicities according to assignment, coupling constants Hz in parentheses.
Table 4
13
w
Ž
.
x
Ž
.
Ž
.
C-NMR data for C5H4 CH2 nNR Zr CH2 Ph 75.4 MHz, C6 D6, d in ppm
2
n, R
Cp ipso
Cp CH
N–CH2
59.98
–CH2–
26.77
Cp–CH2
29.39
ZrCH2
50.34
2, iPr
135.83
113.06
108.64
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
170.9
170.9
130.0
127.6
128.2
2, tBu
3, Et
134.80
122.69
122.63
113.60
110.98
61.49
29.90
52.86
.
.
.
.
.
170.9
172.1
134.3
127.6
124.5
110.64
110.31
39.66
30.11
49.61
.
.
.
Ž
.
.
.
170.9
170.9
127.6
125.7
126.4
127.6
3, iPr
111.43
110.75
43.49
27.06
30.84
50.98
.
125.1
.
.
.
Ž
.
.
170.9
169.7
132.5
127.0
126.4
n, R
R, a
R, b
Ph ipso C
Ph o-CH
Ph m-CH
Ph p-CH
2, iPr
44.95
21.23
146.53
130.32
125.59
121.85
Ž
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
Ž
Ž
Ž
Ž
.
120.9
125.7
157.5
153.8
162.4
2, tBu
3, Et
56.84
28.02
146.24
145.66
146.51
129.28
126.96
121.79
.
.
.
.
124.5
156.3
155.0
162.4
50.72
14.89
129.51
126.30
121.82
Ž
Ž
.
.
.
.
.
132.5
126.6
157.5
153.8
162.0
3, iPr
42.07
21.59
129.39
126.53
121.77
.
162.4
.
.
.
.
114.8
126.1
157.5
153.8
Ž
.
Multiplicities according to assignment, coupling constants Hz in parentheses.

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)
146
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
w
Et the dimethylamido derivatives C5H4
AB-patterns for the diastereotopic benzyl meth-
ylene protons in the
CH2 nNR Zr NMe2 were formed through re-
1H-NMR spectrum, with
Ž
.
x
Ž
.
2
action of the ligand with Zr NMe2 4, and were
converted in situ to the corresponding dichlo-
rides through subsequent reaction with 2 equiv
2JHH couplings between 9 and 11 Hz. In their
Ž
.
13C-NMR spectra the Zr–CH2 moiety is found
1
in the range d 60–50 ppm with typical JCH
w
x
of Me3SiCl 10–12 . The dichlorides were ob-
tained free from coordinated dimethylamine af-
ter sublimation.
couplings between 120 and 130 Hz. These fea-
tures are similar to those of other relatively
electron-deficient neutral group 4 metal benzyl
w
Ž
.
x
Ž w
The dibenzyl complexes C5H4 CH2 NR
complexes for some recent examples see 13–
x .
15 and references cited therein .
n
Ž
.
Zr CH2 Ph were prepared either by reaction of
2
Ž
. Ž
the free ligand with Zr CH2 Ph
iPr or by reaction of the dichloride complex
with two equiv of PhCH2 MgX XsCl, Br in
ether followed by extraction with pentane. For
ns2, Rs
4
.
Ž
.
(
)
3. Reaction with B C6 F5 3
Ž
comparison, the dibenzyl compound C5Me4
.
Ž
.
SiMe2 NtBu Zr CH2 Ph was prepared in simi-
In C6D5Br solvent, all Cp–amide zirconium
dibenzyls were found to react cleanly with the
2
lar fashion from the corresponding dichloride
w
x
Ž
.
1,12 .
The dichloride and dibenzyl complexes were
Lewis acidic borane B C6F5 3 by abstraction of
one benzyl group to give cationic zirconium
all characterised by H- and 13C-NMR spec-
benzyl species with PhCH2 B C6F5 3-anions. In
1
Ž .
Ž
.
Ä
w
Ž
.
x
Ž
.4
troscopy Tables 1–4 and for several examples
by elemental analysis. For ns3, RsMe the
dibenzyl complex was reported in the literature
these products, C5H4 CH2 nNR Zr CH2 Ph
PhCH2 B C6F5 3 , the interaction beween the
cationic and anionic moieties were found to be
w
Ž
. x
w x
6 . In contrast to the Me2Si-bridged complex
highly dependent on the nature of the
w
Ž
.
Ž
.
x
w
Ž . x
C 5 H 4 CH 2 n NR -ligand. It is known
C5H4SiMe2 NtBu ZrCl m-Cl 2, which was
w x
found to be dimeric in the solid state 1 and in
from an increasing number of literature exam-
ples that in sterically unhindered cationic transi-
tion-metal complexes the phenyl group of the
w
x
.
solution 12 , the –CH2CH2– bridged complex
w
Ž
x
C5H4 CH2 2 NtBu ZrCl2 was found to be
monomeric in solution cryoscopy in benzene .
PhCH2 B C6F5 3-anion can coordinate in h6-
Ž
.
Ž
.
For the ns2, RsiPr complex the observed
fashion to the electron-deficient transition-metal
y
1
Ž
.
w
x
molecular weight 351 g mol
was signifi-
centre 7,15–17 . Typical structurally charac-
Ž
w
Ž
.
.
x
cantly larger than the calculated value 311 g
terised examples are found in CpZr CH2 Ph
.
w
Ž
.
x w x
w Ž
23x
1
6
moly , but for this compound the monomeric
h -PhCH2B C6F5 3
h -PhCH2 B C6F5 3 16 . The NMR spectro-
7
and Zr CH2Ph
6
w
Ž
. x w x
species still is the predominant one in solution.
The dibenzyl complexes all show characteristic
scopic features of the anion respond to h6-coor-
Scheme 2.

(
)
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
147
Table 5
Relative amounts
d e t e r m i n e d
the contact ion pair and solvent-separated ion
Ž
.
1
%
of h6-bound and free anion at y358C as
f o r t h e c o m p l e x e s
.4w . x
pair species can be readily observed by H- and
13C-NMR spectroscopy as well. It thus seems
that this equilibrium can give a reasonable indi-
cation of the relative steric restrictions imposed
C5H4 CH2 nNR Zr CH2 Ph PhCH2 B C6 F5
by 19 F-NMR
Äw
Ž
.
x
Ž
Ž
3
spectroscopy
n, R
Bound
Free
by the ligand system.
2, iPr
2, tBu
3, Me
3, Et
3, iPr
Me4C5SiMe2 NtBu
92
13
85
31
5
8
87
15
69
95
98
1
w
Ž
. x
.
x
Ž
The complexes C5H 4 CH 2 n NR Zr h -
6
.
w
Ž
CH2 Ph h -PhCH2 B C6F5 3 are characterised
in their H- and 13C-NMR spectra by various
1
2
features, including diastereotopic B-CH2 pro-
tons and an h1-benzyl group bound to Zr that is
freely rotating around the CH2–Ph bond. The
h1-benzyl group is evidenced by the downfield
Ž
.
dination in various ways, one of the most in-
shift of the ipso carbon around d150 ppm , and
dicative is a small but distinct change in 19F-
on the methylene group by the relatively small
2
6
w
Ž
. Ž
.x
NMR Dd m-F – p-F , which for the h -coor-
1JCH of 120 Hz and the relatively large JHH of
dinated anion is about 4 ppm, compared to 3
around 10–11 Hz. For the aromatic protons of
the anion five separate resonances are found,
significantly upfield shifted from the positions
in the free anion 7,17 . A full listing of H- and
C-NMR data of a representative example n
w
x
ppm for the free anion 15 .
19
Ž
.
By F-NMR at low temperature y358C it
1
Ä
w
w
x
is seen that for the complexes
CH2 n NR Zr CH2 Ph
there is an equilibrium in bromobenzene solvent
between the contact h -coordinated ion pair
C5H4
13
Ž
.
x
Ž
.
4
w
Ž
.
3 x
Ž
PhCH2 B C6 F5
.
s3, RsMe can be found in the experimental
6
Ž
.
section.
Ž
.
Äw
Ž
and the solvent-separated ion pair Scheme 2 .
The solvent-separated species
C5 H 4
3x
2
Ž
.
x
Ž
.
4
w
.
The resonances of the two species are well-sep-
CH2 nNR Zr h -CH2 Ph
PhCH2 B C6 F5
Ž
.
arated, and at a specific concentration 0.2 M
the ratio of these two species was determined
are characterised in their 1H- and 13C-NMR
spectra by features that show an asymmetric
Ž
.
Ž
.
for the various Cp–amide ligands Table 5 . It
is seen that for a bridge length ns2 changing
the substituent R from iPr to tBu shifts the
equilibrium from a predominantly bound to a
predominantly free anion. Similarly, for RsiPr
it is seen that a lengthening of the bridge from
ns2 to ns3 effects a comparable change. In
the corresponding titanium dichloride com-
structure at y358C and indicate an additional
interaction of the Zr-bound benzyl group with
the metal centre. These include a significant
Ž
upfield shift of the ipso carbon d around 122
ppm and for the methylene group a JCH larger
than 140 Hz together with a small JHH of
1
.
2
1
w
x
around 7–8 Hz 13,19–22 . A full listing of H-
and 13C-NMR data of a representative example
w
Ž
.
x
Ž
.
ns3, RsiPr can be found in the experimen-
plexes C5H4 CH2 nNiPr TiCl2 it was seen by
w
x
single crystal X-ray diffraction 18 that an in-
crease in bridge length from ns2 to ns3
does not significantly alter the M–CrNrCl dis-
tal section.
Ä
w
Ž . x Ž
C 5 H 4 CH 2 n NR Zr h-
The cations
q
.
4
CH2 Ph
are thermally quite robust in solu-
tion. Variable temperature 1H-NMR spec-
troscopy from y358C to 658C of this species
for ns2, RstBu shows fluxional behaviour
by which at high temperatures a spectrum of a
symmetrically averaged structure is observed.
Estimated free energies of activation from the
coalescence of the benzyl o-H and ZrCH2 pro-
Ž
.
tances. Instead the Cp centroid –Ti–N and Ti–
Ž
.
N–C bridge angles increase and the Ti–N–
Ž
.
C iPr angle decreases, pushing the iPr-sub-
stituent forward, thus restricting the remaining
coordination space around the metal centre. For
the cationic Zr complex with ns3, RsEt an
intermediate situation is found, for which both

(
)
148
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
1
4
tons respectively are 12.4 kcal moly Tc s260
At a catalyst concentration of 2=10y mol
Ž
y
1
1
.
Ž
.
K and 13.4 kcal mol
Tc s290 K .
ly the catalyst with ns3, RsMe and
C5Me4 SiMe2 NtBu ZrCl2 both showed rela-
w
Ž
.
x
tively high activities resulting in a significant
exotherm of about 158C, the latter catalyst being
somewhat more productive. At a lower catalyst
4. Ethene homopolymerisation
y
5
T he catalytic activities of the
concentration 3.3 = 10
mol ly1 this
.
Ž
w
Ž
.
x
C5H4 CH2 nNR ZrCl2rMAO catalysts in the
exotherm was eliminated and the ns3, RsMe
catalyst proved to be the more productive. The
relative trends in activity for the other catalysts
were found to be still valid at this lower concen-
tration.
homopolymerisation of ethene were probed in
toluene under various conditions. The results
are listed in Table 6. Note that the activities
listed in the last column are only based on the
observed productivity over the 30 min run time
extrapolated to 1 h. They do not take into
account possible differences in activity profile
for the various catalysts over the run time, and
should be used as relative measures of catalyst
efficiency within the series rather than as abso-
lute activities.
Ž
.
In the C5R4SiMe2 NtBu MCl2rMAO sys-
Ž
.
tem MsTi, Zr it was observed that the pres-
ence of the methyl substituents on the Cp-moiety
w
x
greatly improved catalyst efficiency 1,5 . It ap-
w
Ž
.
x
pears that the C5H4 CH2 nNR ZrCl2rMAO
system can exceed the efficiency of the above
Ž
.
Zr system for the longer bridge length ns3
At 808C and 20 bar ethene pressure the dif-
ference in activity between the ns2, RsiPr
and ns2, RstBu catalysts was found to be
minimal. However, for RsiPr the catalyst with
bridge length ns3 was found to be about four
times more efficient than with bridge length
ns2. This is remarkable in that for the
in the ethene homopolymerisation under the
applied conditions, provided the substituent on
the amido functionality is small. It is possible
Ž
.
that the C5Me4SiMe2 NtBu ZrCl2rMAO sys-
tem has a steeper activity versus temperature
slope than the other catalysts described here, as
the system responds more strongly to the
exotherm observed in the polymerisation at rela-
tively high catalyst concentration. This is also
suggested by the observation that under milder
w
Ž
.
x
C5Me4 SiMe2 nNtBu Ti-system the efficiency
of the catalyst dropped considerably upon in-
creasing the bridge length from ns1 to ns2
w
x
Ž
.
1,5 .
polymerisation conditions 508C, 5 bar ethene
Table 6
w
Ž
.
x
Ž
.
Ethene homopolymerisation with C5H4 CH2 nNR ZrCl2rMAO catalysts toluene solvent, AlrZrs520, 30 min run time
5
y1
y1
Act. g mmol hy1
w
x
Ž
.
Ž
.
Ž
. Ž
.
Ž .
PE yield g
Ž
.
Catalyst
Zr =10 mol l
T
8C
p C2 H4 bar
2, iPr
3, iPr
cata
2, iPr
2, tBu
3, iPr
3, Me
cata
2, iPr
3, iPr
3, Me
cata
20
20
20
20
22
21
21
20
50
50
50
80
80
80
5
5
5
1.2
1.3
0.2
3.4
3.4
17.4
49.7
55.0
0.4
3.0
8.0
60
65
10
20
20
20
20
20
20
20
20
20
170
155
829
2367
2750
81
606
1617
667
80b
80b
80
3.3
3.3
3.3
3.3
80
80
80
3.3
aŽ
.
C5Me4SiMe2 NtBu ZrCl2.
bSignificant exotherm.

(
)
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
149
the activity of this catalyst is even less than that
6. Experimental
of the ns2, 3, RsiPr catalysts.
6.1. General considerations
All organometallic compounds mentioned in
this paper are air and moisture sensitive and
manipulations were performed under nitrogen
atmosphere using standard Schlenk and glove
5. Conclusions
A range of zirconium dichloride complexes
with linked Cp–amido ancillary ligands,
Ž
.
box Braun MB-200 techniques. Solvents
Ž
.
toluene, THF, ether and pentane were purified
w
Ž
.
x
Ž
C5H4 CH2 nNR ZrCl2 ns2, RsiPr, tBu;
by distillation from K or NarK alloy. ZrCl4
.
ns3, RsMe, Et, iPr can be prepared readily
Ž
.
Aldrich, 99.5q% was used without further
using amine elimination reactions employing
purification. Deuterated solvents were distilled
Ž
. Ž
.
Zr NMe2 4 followed by reaction with Me3SiCl
Ž
.
from NarK alloy C6D6 or degassed and dried
Ž
.
Ž
.
or Zr NMe2 2Cl2 THF . The position of the
2
˚
Ž
.
over 4 A mol. sieves CDCl3, C6D5Br .
Zr NMe2 4 23 and B C6F5 3 24 were synthe-
sized according to published procedures.
equilibrium between the contact ion pair and the
Ž
.
w
x
Ž
. w x
Ä
w
.
solvent-separated ion pair in the complexes C5
3 x
Ž
.
x
Ž
.
4
w
Ž
H 4 CH 2 n NR Zr CH 2 Ph PhCH 2 B C6 F5
Ž
.
Ž
.
Zr NMe2 2Cl2 THF
2
was prepared from
Zr NMe2 4 and ZrCl4 in THF according to a
w x
can give a reasonable indication of the change
in steric requirements of the ligand upon varia-
tion in bridge length andror substituent on the
Ž
.
modification of the literature procedure 9 . A
1.5 M solution of MAO in toluene AKZO
Nobel was used as received. Ethene AGA,
polymer grade was passed over a supported
Ž
w
Ž
.
x
amido functionality. The C5H4 CH2 nNR
.
Ž
ZrCl2rMAO combinations are catalysts for the
homopolymerisation of ethene, which are more
efficient for the longer ligand bridge length
ns3 than for ns2. The observed ligand de-
pendence of the polymerisation efficiency does
not clearly correlate with overall ligand steric
hindrance as deduced from the boundrfree an-
ion equilibrium for the cationic benzyl com-
plexes. Within the series of complexes with
unsubstituted Cp ligands the match between
metal centre and bridge length appears to be of
prime importance. It is presently uncertain if the
.
Ž
.
copper scavenger BASF R 3-11 and mol.
˚
Ž
.
sieves 3 A before being passed to the reactor.
1H, 13C and 19F NMR spectra were recorded
using Varian Gemini-200, VXR-300 or Unity-
500 spectrometers. The chemical shifts are re-
ported in ppm and referenced internally using
the residual solvent resonances relative to TMS
Ž
.
d 0 ppm . Elemental analyses were performed
by the Microanalytical Department of the
Chemical Laboratories of the University of
Groningen; data given are the average of at least
two independent determinations. Molecular
weights were determined by cryoscopy in ben-
zene.
Ž
observed effects are specific for the Cp–
.
amide ZrCl2rMAO combination or if they are
valid also when other activatorsrcounterions
are used. This would require separate studies on
the MAO-free systems, where great care has to
be taken to eliminate effects of impurities in the
solvent and feed.
(
)(
)
6.2. Synthesis of C5 H5 CH2 n NHR
The various ligands of this type were pre-
Ž
.
Despite the obvious limitations of the present
study, it seems that comparative reactivity stud-
ies of the series of Cp-bridge–amido complexes
obtained can yield interesting information on
the structure–activity relationships in homoge-
neous Ziegler-type catalysts.
pared by the reaction of Br CH2 nNHRPHBr
with a threefold excess of CpNa in THF in
analogous fashion to that reported for ns3,
w x
RsMe 6 . Yields after vacuum distillation or
vacuum transfer 60–80%. The ligands are ob-
tained as mixtures of the 1,2- and 1,3-isomers.

(
)
150
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
[
(
)
]
Ž
.
6.3. Synthesis of C5 H4 CH2 n NR ZrCl2 from
toluene, 0.8 m l
5.3 m m ol
of
(
)
Ž
.
Ž .
Zr NMe2 4
C5H5 CH2 2 N H –i-Pr was added. Subse-
quently the reaction mixture was stirred for 18 h
at 758C. The resultant yellow solution was fil-
tered and the volatiles were removed in vacuo
giving a yellow solid. This was stripped of
remaining toluene by stirring with 10 ml of
pentane that was then pumped off. The residual
light yellow solid was rinsed 3 times with 25 ml
of pentane and dried in vacuo. After sublima-
6.3.1. ns3, RsMe
Ž
.
To a solution of 6.76 g 25.27 mmol of
Ž
.
Ž
Ž
.
Zr NMe2 4 in 30 ml of toluene 08C was added
Ž
.
.
Ž .
3.4 g 24.8 mmol of C5H5 CH2 3N H Me.
The mixture was warmed to 508C and stirred for
0.5 h. The resulting light green–yellow solution
Ž
.
was cooled to 08C and 6.4 ml 50.4 mmol of
Me3SiCl was added. A light yellow precipitate
formed which dissolved upon heating to reflux.
After refluxing for 4 h a clear brownish yellow
solution was formed. The solvent was removed
in vacuo and the residue rinsed twice with 30
ml of pentane. After drying in vacuo, the residue
was extracted with 60 ml of hot toluene. Con-
centrating at 80–908C to 15 ml and slowly
cooling to y208C produced cream coloured
crystals of the NHMe2 adduct of the title com-
Ž
.
tion 0.05 mm Hg, 608C the title compound
was isolated free from residual dimethylamine
as an off white solid. Yield: 1.2 g 3.9 mmol;
74% . Analysis for C10H15NCl2 Zr: calculated:
C, 38.58; H, 4.86; Zr, 29.30; found: C, 38.58;
H, 4.81; Zr, 29.20. Molecular weight for
C10H15NCl2 Zr: calculated: 311 grmol; found
Ž
.
Ž
.
cryoscopy : 351 grmol.
Ž
Other derivatives made by this route using
.
the appropriate ligand :
– ns2, RstBu: yield 69%. Analysis for
C11H17NCl2 Zr: calculated: C, 40.60; H, 5.27;
Zr, 28.03; found: C, 40.55; H, 5.27; Zr, 28.13.
Molecular weight for C11H17NCl2 Zr: calcu-
Ž
pound. Yield: 6.48 g 18.92 mmol, 75% based
on C5H4 CH2 3NMe ZrCl2 P HNMe2 . 1H
w
Ž
.
x
.
Ž
.
Ž
NMR 200 MHz, CDCl3 : d 6.20 m, JHH
2.68 Hz, 2H, C5H4 ; 6.07 m, JHH s2.68 Hz,
2H, C5H4 ; 2.99 s, 3H, NMe ; 2.93 m, 2H,
NCH2 ; 2.75 m, 2H, C5H4CH2 ; 2.62 d, JHH
s 5.86 Hz, 6H, HNMe2 ; 2.12 m, 2H,
NCH2C H2 . Sublimation of 0.95 g 2.77 mmol
s
.
Ž
Ž
.
lated: 325 grmol; found cryoscopy : 332
.
Ž
.
Ž
Ž
3
grmol.
.
Ž
.
– ns3, RsiPr: yield 71%. Analysis for
C11H17NCl2 Zr: calculated: C, 40.60; H, 5.27;
Zr, 28.03; found: C, 40.66; H, 5.27; Zr, 28.05.
1H- and 13C-NMR data of the compounds
mentioned are found in Tables 1 and 2.
.
Ž
.
Ž
.
w
Ž
.
x
of C5H4 CH2 3NMe ZrCl2 PHNMe2 at 150–
1608C and 10y Torr yielded 0.75 g of
3
w
Ž
.
x
Ž
.
C5H4 CH2 3NMe ZrCl2 2.52 mmol, 91% ,
pure by NMR spectroscopy.
[
(
)
]
6.5. Synthesis of C5 H4 CH2 2 N–i-Pr
(
)
Zr CH2 Ph 2
6.3.2. ns3, RsEt
This compound was obtained in similar fash-
ion, using the appropriate ligand, in 66% overall
Ž
.
Ž
To a cooled 08C solution of 1.33 g 2.92
mmol of Zr CH2 Ph in 10 ml of toluene, 446
.
Ž
.
1
yield. H- and 13C-NMR data of the compounds
4
Ž
.
Ž
.
Ž .
ml 2.99 mmol of C5H5 CH2 2 N H –i-Pr was
added. The mixture was stirred overnight at
ambient temperature. After removal of the sol-
vent the sticky residue was stripped of remain-
ing solvent by stirring with 10 ml of pentane
which was subsequently pumped off. The brown
powder was then extracted with ether. Upon
concentrating the solution and standing
overnight at y208C, 0.55 g crystalline material
mentioned are found in Tables 1 and 2.
[
(
)
]
6.4. Synthesis of C5 H4 CH2 n NR ZrCl2 from
(
)
(
)
Zr NMe2 2Cl2 THF 2
6.4.1. ns2, RsiPr
Ž
To a clear yellow solution of 2.1 g 5.3
.
Ž
.
Ž
.
mmol of Zr NMe2 2Cl2 P THF in 50 ml of
2

(
)
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
151
[ ]
6.7. Synthesis of C5 Me4SiMe2 N–t-Bu Zr
was obtained. Further concentation and cooling
of the mother liquor yielded a second crop of
(
)
CH2 Ph 2
Ž
0.25 g of product. Total yield: 0.80 g 1.89
.
w Ž .
m m ol, 65%
of
C 5 H 4 C H 2 2 N – i-
Pr Zr CH2 Ph . Anal. calc. for C24H29NZr: C,
Ž
.
Ž
To a cooled 08C solution of 1.71 g 4.15
x
Ž
.
.
w
x
2
mmol of C5Me4SiMe2 N–t-Bu ZrCl2 in 20 ml
68.19; H, 6.92; Zr, 21.58; found: C, 68.44; H,
7.15; Zr, 21.47. 1H- and 13C-NMR data are
found in Tables 3 and 4.
Ž
.
of ether 9.6 ml of a 0.93 M 8.9 mmol solution
of PhCH2 MgCl in ether was added dropwise.
After stirring for 1.5 h at room temperature the
solvent was removed in vacuo leaving a light
yellow residue. The residue was stripped of
remaining ether by stirring with 20 ml of pen-
tane which was subsequently pumped off. Ex-
tracting the residue with 50 ml of pentane gave
a clear light yellow solution. The solution was
concentrated at reflux to 10 ml and cooling
overnight to y208C resulted in 1.23 g of light
[
(
)
] (
)
6.6. Synthesis of C5 H4 CH2 n NR Zr CH2 Ph 2
from the corresponding dichlorides
6.6.1. ns3, RsiPr
Ž
.
To a cooled suspension y208C of 2.13 g
Ž
.
w
Ž
.
x
6.55 mmol C5H4 CH2 3N–i-Pr ZrCl2 in 30
Ž
.
ml of ether 15 ml of a 0.93 M 13.9 mmol
Ž
.
yellow crystals. A second crop 0.40 g was
obtained by further concentration and cooling of
PhCH2 MgCl solution in ether was added drop-
wise. After warming to room temperature the
mixture was stirred for 4 h during which the
colourless mixture turned light yellow. Removal
of the solvent yielded a light yellow residue
which was stripped of residual ether by stirring
with with 30 ml of pentane which was subse-
quently pumped off. The solids were extracted
with 50 m of pentane and the resulting light
yellow solution was concentrated to 15 ml. Light
yellow crystals were obtained on standing
overnight at y208C. This yielded 1.92 g of
Ž
the mother liquor. Total yield 1.63 g 3.12
.
w
x
mmol, 75% of C 5 Me4 SiMe2 NtBu
Zr CH2 Ph . H NMR 300 MHz, C6D6 : d
1
Ž
.
Ž
.
2
3
Ž
.
Ž
7.12 t, JHH s7.51 Hz, 4H, m-Ph , 6.90 t,
3
3
.
Ž
JHH s7.33 Hz, 2H, p-Ph , 6.78 d, JHH s7.33
.
Ž
.
Ž
Hz, 4H, o-Ph , 1.91 s, 6H, C5Me4 , 1.87 d,
2
.
Ž
JHH s10.99 Hz, 2H, C H2 Ph , 1.78 s, 6H,
2
.
Ž
C5Me4 , 1.61 d, JHH s 10.99 Hz, 2H,
.
Ž
.
Ž
C H2 Ph , 1.14 s, 9H, CMe3 , 0.42 s, 6H,
13
.
Ž
.
SiMe2 . C NMR 75.4 MHz, C6D6 : d 147.10
s, ipso- Ph , 130.01 s, C5Me4 , 129.08 d,
JCH s156.3 Hz, o-Ph , 127.26 d, JCH s153.8
Hz, m-Ph , 126.22 s, C5Me4 , 122.08 d, JCH
Ž
.
Ž
.
Ž
1
1
Ž
.
product. A second crop 0.51 g was obtained
by further concentration and cooling of the
.
Ž
1
.
Ž
.
.
Ž
Ž
Ž
mother liquor. Total yield: 2.43 g 5.56 mmol.
.
s161.1 Hz, p-Ph , 97.87 s, ipso-C5Me4 ,
1
.
w
Ž
.
.
Ž
.
85% of C5H4 CH2 3N–i-Pr Zr CH2 Ph ,
Ž
.
Ž
2
61.02 t, JCH s122.1 Hz, CH2 Ph , 56.63 s,
1
pure by NMR spectroscopy.
.
Ž
.
CMe3 , 33.80 q, JCH s124.5 Hz, C Me3 ,
1
Other derivatives made by this route:
– ns2, RstBu: yield 65%. Analysis for
C25H31NZr: calculated: C, 68.75; H, 7.15; Zr,
20.89; found: C, 68.39; H, 7.10; Zr, 20.80. The
somewhat low carbon value found may reflect
some zirconium carbide formation during com-
bustion.
Ž
.
Ž
14.44 q, JCH s127.0 Hz, C5 Me4 , 11.46 q,
1
1
.
Ž
JCH s126.6 Hz, C5 Me4 , 6.69 q, JCH s119.2
.
Hz, SiMe2 .
[
(
)
] (
)
6.8. Reaction of C5 H4 CH2 n NR Zr CH2 Ph 2
(
)
with B C6 F5 3 in C6 D5 Br
– ns3, RsEt: yield 65%.
Ž
.
Ž
.
2
–
C5Me4SiMe2 NtBu Zr CH2 Ph : yield
In these experiments 0.08 mmol of a Zr
dibenzyl complex and an equimolar amount of
Ž
.
75% for full details, see below .
1H- and 13C-NMR data of the compounds
mentioned are found in Tables 3 and 4.
B C6F5 3 were dissolved in 0.4 ml of C6D5Br,
giving 0.2 M solutions of the various ionic
Ž
.

(
)
152
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
Ž
Ž
.
complexes without noticeable byproducts as
NMR 125.7 MHz, C6D5Br, y358C : d 20.77,
seen by NMR . Low temperature y358C 1H-
.
Ž
.
Ž
.
Ž
22.05 q, 127.7 Hz, iPr Me , 25.44 t, 129.5 Hz,
–CH2– , 28.38 t, 129.7 Hz, CpCH2 , 31.8
v.br. BCH2 , 39.81 d, 108.1 Hz, iPr CH ,
and 13C-NMR data of two representative species
.
Ž
.
Ž
Ž
.
Ž
.
one contact ion pair, ns3, RsMe, and one
.
Ž
.
Ž
solvent-separated ion pair, ns3, RsiPr are
44.48 t, 135.5 Hz, NCH2 , 53.43 t, 144.5 Hz,
1
.
Ž
.
given below. H-NMR assignments were aided
ZrCH2 , 108.57 d, 171.6 Hz, Cp CH , 109.30,
by recording H,1H-COSY spectra.
1
Ž
.
Ž
109.41 d, about 174 Hz, Cp CH , 115.16 d,
172.0 Hz, Cp CH , 121.82 ZrBz Cipso , 122.93
d, 160.4 Hz, BBz p-CH , 124.04 d, 160.4 Hz,
ZrBz CH , 127.18 d, 156.7 Hz, BBz m-CH ,
128.11 d, 164.1 Hz, ZrBz CH , 128.82 d, part.
overlap, BBz m-CH , 131.82 d, 160.4 Hz,
ZrBz CH , 132.25 Cp Cipso , 132.74 d, 164.1
1
6
w
Ž
.
x
Ž
.w
.
Ž
.
C 5 H 4 CH 2 3 NM e Zr h -CH 2 Ph h -
1H-NMR 500 MHz,
Ž
Ž
.
x
Ž
.
Ž
PhCH 2 B C6 F5
:
3
.
Ž
.
.
Ž
.
C6D5Br, y358C : d 1.17, 1.63 m, –CH2– ,
Ž
.
Ž
Ž
.
Ž
1.63, 1.68 d, 10.8 Hz, ZrCH2 , 2.22, 2.35 m,
.
Ž
.
Ž
.
Ž
CpCH2 , 2.42–2.40 2H, N–CH2 , 3.12, 3.26
br, BCH2 , 4.58, 5.20, 5.34, 5.48 Cp H , 6.52
d, 7.3 Hz, 2H, ZrBz o-H , 6.57, 6.60, 6.80,
Ž
.
.
.
Ž
.
Ž
Ž
.
.
Ž
.
Hz, ZrBz CH , 133.29 d, 164.1 Hz, ZrBz CH ,
148.60 BBz Cipso . 19F-NMR 282 MHz,
Ž
.
Ž
.
Ž
.
Ž
6.92, 7.10 BBz ArH , 6.95 ZrBz p-H , 7.20
2H, ZrBz m-H . 13C-NMR 125.7 MHz,
Ž
.
.
Ž
.
Ž
.
C6D5Br, y358C : dy132.5 o-F , y164.8
p-F , y167.8 m-F , Dd pym s3.0.
Ž
Ž
.
Ž
.
Ž
.
C6D5Br, y358C : d 26.65 t, 128.7 Hz,
.
Ž
Ž
.
Ž
–CH2– , 32.40 t, 128.7 Hz, CpCH2 , 34.6 br,
.
.
Ž
BCH2 , 43.98 q, 132.4 Hz, NMe , 54.41 t,
6.9. Ethene polymerisation experiments
.
Ž
120.3 Hz, ZrCH2 , 105.56 d, 166.0 Hz, Cp
.
Ž
.
Ž
CH , 109.21 d, 169.7 Hz, Cp CH , 116.37 d,
Ethene slurry polymerisation reactions were
carried out in a thermostated electrical heating,
water cooling Medimex 1l stainless steel auto-
clave. For each run a total of 200 ml of toluene
300 ml for the last five entries in Table 6 was
used as solvent. The appropriate Cp–amide zir-
conium dichlorides were stirred for 15 min in
10 ml of toluene with 175 equiv of MAO 33%
.
Ž
Ž
173.5 Hz, Cp CH , 117.07 d, 180.9 Hz, Cp
CH , 122.40 d, 159.4 Hz, ZrBr p-CH , 123.11
d, 167.5, BBz p-CH , 124 v.br., BC , 125.13
d, 153.0 Hz, ZrBz m-CH , 127.11 d, part
overlap, BBz CH , 128.16 d, 162.4 Hz, BBz
CH , 128.42 d, 156.6 Hz, ZrBz o-CH , 128.79
d, part overlap, BBz CH , 129 overlap, BBz
.
Ž
.
.
Ž
Ž
.
Ž
.
.
Ž
Ž
.
.
Ž
.
Ž
.
Ž
.
Ž
Ž
Ž
.
Ž
.
.
CH , 133.35 Cp Cipso , 136.7 d, JCF s247
of the total amount of MAO used, AlrZrs520
.
Ž
.
Hz, m-CF , 138.2 d, JCF s247 Hz, p-CF ,
before use. The remaining MAO was brought
directly into the reactor with the solvent. At the
desired reaction temperature the catalyst solu-
tion was injected into the reactor and ethene
pressure was admitted, after which the ethene
pressure was kept constant. After 30 min the
runs were terminated by venting the reactor and
quenching with methanol. The polymers were
slurried in acidified methanol for several hours,
repeatedly rinsed with ethanol and petroleum
ether and dried in vacuo at 708C. The data in
Table 6 represent single runs, performed as a
series using the same batch of MAOrtoluene
activator and solvent for internal consistency.
Duplo runs performed for several experiments
showed a variance in catalyst activity of about
15–20%.
Ž
.
.
Ž
148.1 d, JCF s242 Hz, o-CF , 149.05 ZrBz
19
Ž
.
Ž
Cipso , 155.95 BBz Cipso . F-NMR 282
.
Ž
Ž
.
MHz, C6D5Br, y358C : d y 132.9 o-F ,
Ž
.
.
Ž
.
y162.0 p-F , y166.0 m-F , Dd pym s
4.0.
2
Ä
w
Ž
.
x
Ž
.
4
C 5 H C H 3 N iP r Z r h -C H P h
2
2
w
4 Ž
.
x
PhCH2 B C6F5 3
1H-NMR 500 MHz,
Ž
:
.
Ž
.
C6D5Br, y358C : d 0.92 d, 5.4 Hz, iPr Me ,
1.03 d, 4.9 Hz, iPr Me , 1.47, 1.62 m, –CH2–
Ž
.
Ž
.
Ž
.
.
Ž
, 1.64, 2.75 d, 7.8 Hz, ZrCH2 , 2.15, 2.20 m,
.
Ž
Ž
CpCH2 , 2.4 m, 2H, NCH2 , 3.22 m, iPr
CH , 3.45 br, 2H, BCH2 , 4.50, 5.25, 5.62,
5.97 Cp CH , 6.26 d, 6.4 Hz, ZrBz o-H , 6.77
d, 7.3 Hz, ZrBz o-H , 6.91 t, 7.1 Hz, BBz
.
Ž
.
Ž
.
Ž
.
Ž
.
Ž
.
.
Ž
Ž
.
Ž
p-H , 7.07 m, BBz m-H , 7.24, 7.31 ZrBz
m-H , 7.26 BBz o-H , 7.28 ZrBz p-H . 13C-
.
Ž
.

(
)
P.-J. Sinnema et al.rJournal of Molecular Catalysis A: Chemical 128 1998 143–153
153
w
w
w
w
w
w
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x
12 D.W. Carpenetti, L. Kloppenburg, J.T. Kupec, J.L. Petersen,
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