Group 4 metal amido fluorides and chlorides: Molecular structures and the first comparison in ethylene polymerization catalysis

Article abstract of DOI:10.1021/om960177v

Lithium (2,6-diisopropylphenyl)(trimethylsilyl)amide (2,6-iPr₂C₆H₃N(SiMe₃)Li) reacts with MCl₄ (M = Zr, Hf) in a 2:1 molar ratio to give [{2,6-iPr₂C₆H₃N(SiMe₃

Full text of DOI:10.1021/om960177v

3176
Organometallics 1996, 15, 3176-3181
Gr ou p 4 Meta l Am id o F lu or id es a n d Ch lor id es:
Molecu la r Str u ctu r es a n d th e F ir st Com p a r ison in
Eth ylen e P olym er iza tion Ca ta lysis
Syed A. A. Shah, Hendrik Dorn, Andreas Voigt, Herbert W. Roesky,*
Emilio Parisini, Hans-Georg Schmidt, and Mathias Noltemeyer
Institut fu¨r Anorganische Chemie der Universita¨t Go¨ttingen, Tammannstrasse 4,
D-37077 Go¨ttingen, Germany
Received March 7, 1996X
Lithium (2,6-diisopropylphenyl)(trimethylsilyl)amide (2,6-iPr2C6H3N(SiMe3)Li) reacts with
MCl4 (M ) Zr, Hf) in a 2:1 molar ratio to give [{2,6-iPr2C6H3N(SiMe3)}2MCl2] (1a , M ) Zr;
1b, M ) Hf) and with (C5Me5)MCl3 (1:1) to give [(C5Me5){2,6-iPr2C6H3N(SiMe3)}MCl2] (2a ,
M ) Zr; 2b, M ) Hf). Further reaction of the dichlorides (1a ,b, 2a ,b) with Me3SnF leads to
the corresponding difluorides [{2,6-iPr2C6H3N(SiMe3)}2MF2] (3a , M ) Zr; 3b, M ) Hf) and
[(C5Me5){2,6-iPr2C6H3N(SiMe3)}MF2] (4a , M ) Zr; 4b, M ) Hf). The compounds 1-4 were
investigated as potential catalysts for the polymerization of olefins, in combination with
methylaluminoxane (MAO). For the first time the catalytic activities, toward the poly-
merization of ethylene, of chlorides and the corresponding fluorides are compared under
identical conditions. The solid-state structures of 1a ,b, 2b, 3a , and 4a were determined by
single-crystal X-ray diffraction.
In tr od u ction
There are many examples of unbridged amido-
monocyclopentadienyl group 4 complexes,19-22 but little
information is known about their catalytic activity.
Unbridged bis(amido) complexes of zirconium, such as
[{(Me3Si)2N}2ZrCl2], were also found to be catalysts for
the polymerization of olefins.23
Up to now, however, only chloro complexes of these
amido systems have been investigated. The corre-
sponding fluorides have not been studied to any great
extent due to the lack of practical preparative proce-
dures. The use of trimethyltin fluoride as a fluorinating
agent for group 4 organometallic systems has recently
been undertaken.24 Mono- and dicyclopentadienyl group
4 chlorides were converted to the respective fluorides
via metathesis with Me3SnF, under mild conditions.
In this paper, we describe the preparation of both
bis(amido) group 4 chlorides and fluorides, as well as
the amido-cyclopentadienyl chlorides and fluorides,
with a view to testing their catalytic activity with
respect to the polymerization of olefins. To our knowl-
The utilization of group 4 metallocenes as catalysts
for olefin polymerization is well established.1-11 The use
of bridged cyclopentadienyl ligands has allowed the
preparation of ansa-metallocenes, which have proved
significant in the stereospecific polymerization of pro-
pylene.12 Recently, there has been growing interest in
bridged amido-cyclopentadienyl complexes where the
cyclopentadienyl group is linked via an SiMe2 unit to
the amido ligand.13 The first complexes of this type had
scandium14 and titanium15 as the metal centers. More
recently, further group 4 metal complexes have been
developed.16 Many such complexes have also found
industrial applications as isospecific polymerization
catalysts for propylene17 and in the synthesis of linear
low-density polyethylene (LLDPE).18
X Abstract published in Advance ACS Abstracts, J une 15, 1996.
(1) Sinn, H.; Kaminsky, W. Adv. Organomet. Chem. 1980, 18, 99.
(2) J ordan, R. F. Adv. Organomet. Chem. 1991, 32, 325.
(3) Marks, T. J . Acc. Chem. Res. 1992, 25, 57.
(4) Horton, A. D. Trends Polym. Sci. 1994, 2, 158.
(5) Kaminsky, W. Angew. Makromol. Chem. 1994, 223, 101.
(6) Bochmann, M.; Lancaster, S. J . Organometallics 1993, 12, 633.
(7) Hlatky, G. G.; Eckmann, R. R.; Turner, H. W. Organometallics
1992, 11, 1413.
(8) Herrmann, W. A.; Anwander, R.; Riepl, H.; Scherer, W.; Whi-
taker, C. R. Organometallics 1993, 12, 4342.
(9) Tsai, W.-M.; Chien, J . C. W. J . Polym. Sci., A: Polym. Chem.
1994, 32, 149.
(16) (a) Herrmann, W. A.; Morawietz, M. J . A.; Priermeier, T. Angew.
Chem. 1994, 106, 2025; Angew. Chem., Int. Ed. Engl. 1994, 33, 1941.
(b) Herrmann, W. A.; Morawietz, M. J . A. J . Organomet. Chem. 1994,
482, 169. (c) Herrmann, W. A.; Morawietz, M. J . A.; Priermeier, T.;
Mashima, K. J . Organomet. Chem. 1995, 486, 291. (d) Spence, R. E.
v. H.; Piers, W. E. Organometallics 1995, 14, 4617. (e) Scollard, J . D.;
McConville, D. H.; Vittal, J . J . Organometallics 1995, 14, 5478.
(17) Stevens, C. J .; Timmers, J . F.; Wilson, R. D.; Schmidt, G. F.;
Nickias, P. N.; Rosen, R. K.; Knight, G. W.; Lai, S. Eur. Pat. Appl.
416 815, 1989.
(18) Canich, J . A. M. U.S. Patent 5 026 798, 1990.
(10) Mo¨hring, P. C.; Coville, N. C. J . Organomet. Chem. 1994, 479,
1.
(19) J ekel-Vroegop, C. T.; Teuben, J . H. J . Organomet. Chem. 1985,
286, 309.
(20) (a) Bai, Y.; Roesky, H. W.; Noltemeyer, M. Z. Anorg. Allg. Chem.
1991, 595, 21. (b) Bai, Y.; Noltemeyer, M.; Roesky, H. W. Z. Natur-
forsch. 1991, 46B, 1357.
(21) Giolando, D. M.; Kirschbaum, K.; Graves, L. J .; Bolle, U. Inorg.
Chem. 1992, 31, 3887.
(22) (a) Martin, A.; Mena, M.; Yelamos, C.; Serrano, R.; Raithby, P.
R. J . Organomet. Chem. 1994, 467, 79. (b) Irigoyen, A. M.; Martin,
A.; Mena, M.; Palacios, F.; Yelamos, C. J . Organomet. Chem. 1995,
494, 255.
(11) Spaleck, W.; Ku¨ber, F.; Winter, A.; Rohrmann, J .; Bachmann,
B.; Antberg, M.; Dolle, V.; Paulus, E. F. Organometallics 1994, 13, 954.
(12) Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. Angew. Chem. 1995, 107, 1255; Angew. Chem. Int. Ed.
Engl. 1995, 34, 1143 and references cited therein.
(13) (a) Canich, J . A. M. Eur. Pat. Appl. 420 436, 1991. (b) Canich,
J . A. M.; Hlatky, G. G.; Turner, H. W. U.S. Patent 542 236, 1990. (c)
Campbell, R. E. U.S. Patent 5 066 741, 1991. (d) LaPointe, R. E.;
Rosen, R. K.; Nickias, P. N. Eur. Pat. 495 375, 1992.
(14) Shapiro, P. J .; Bunel, E.; Schaefer, W. P.; Bercaw, J . E.
Organometallics 1990, 9, 867.
(23) Canich, J . A. M. WO 92/12162, 1992.
(24) Herzog, A.; Liu, F.-Q.; Roesky, H. W.; Demsar, A.; Keller, K.;
Noltemeyer, M.; Pauer, F. Organometallics 1994, 13, 1251.
(15) Okuda, J . Chem. Ber. 1990, 123, 1649.
S0276-7333(96)00177-X CCC: $12.00 © 1996 American Chemical Society
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Group 4 Metal Amido Fluorides and Chlorides
Organometallics, Vol. 15, No. 14, 1996 3177
Sch em e 1
our group it was found that bridging imido systems are
accessible by reaction of MCl4 (M ) Zr, Hf) with (tBu)-
NHLi, while compounds having terminal imido groups
can be synthesized by heating a solution of (C5Me5)Zr-
(NHAr)3.25 Wigley and co-workers, however, prepared
terminal and bridging imido chloride complexes by
simple reaction of ZrCl4‚2THF or (C5Me5)ZrCl3 with
ArNHLi and treatment with Me3SiCl. Attempts to
prepare mono- or dichloro imido complexes from the
appropriate stoichiometric reactions of ZrCl4‚2THF and
ArNHLi did not yield tractable products.26
The dichlorides (1a ,b, 2a ,b) undergo metathesis with
trimethyltin fluoride to give the first group 4 bis(amido)
and amido cyclopentadienyl fluorides (3a ,b, 4a ,b). This
was achieved by reaction with trimethyltin fluoride in
a molar ratio of 2:1, in toluene at room temperature.
The 19F NMR spectra of 3a ,b and 4a ,b all contain one
singlet in the region of δ 110-36, indicating that they
are monomeric in solution. Interestingly, the trimeth-
ylsilyl group on the amido function is not affected by
trimethyltin fluoride; i.e., an imido complex is not
formed via elimination of Me3SiF. This suggests that
trimethyltin fluoride is an appropriate fluorinating
agent for N-substituted group 4 systems.
The main diagnostic feature of the IR spectra of the
difluorides is the appearance of two M-F bond stretch-
ing frequencies. These occur in the range 610-570 cm-1
and are consistent with values of known zirconium and
hafnium difluorides.27
The crystal structure of 1a is shown in Figure 1, with
the structures of 2b and 3a shown in Figures 2 and 3,
respectively. Relevant bond distances and angles are
reported in Table 1, while crystallographic data are
summarized in Table 2.
Complexes 1a and 1b are isostructural. The crystal
structures of 1a and 1b, where two chlorine atoms and
two (trimethylsilyl)(diisopropylphenyl)amide groups co-
ordinate a Zr and Hf atom, respectively, do not show
any significant variations in terms of internal geo-
metrical parameters. The Cl-metal-Cl angles are
102.9(1) and 103.9(1)°, while the N-metal-N angles are
118.2(1) and 117.6(1)° in 1a and 1b, respectively. The
average Zr-Cl distance in 1a is 2.380(1) Å, while the
average Hf-Cl bond length in 1b is 2.347(1) Å. The
difference between the mean metal-nitrogen distances
in the two structures is within experimental error
(2.029(2) vs 2.023(3) Å).
The sterically demanding pentamethylcyclopenta-
dienyl ligand coordinating the Hf atom in 2b causes a
slight lengthening of the Hf-N distance with respect
to the corresponding average bond length in the sym-
metrically substituted structure of 1b (2.054(3) vs
2.023(3) Å). The increased bulkiness of the ring system
with respect to the N-bonded ligand is also reflected by
the angle N(1)-Hf(1)-X(1A), where X(1A) is the cen-
troid of the Cp* ligand (Cp* ) C5Me5), this being larger
than the corresponding N(1)-Hf(1)-N(2) angle in 1b
(123.9(1) and 117.6(1)°, respectively).
edge, these represent the first structurally characterized
group 4 amido fluorides and the first comparison of their
catalytic properties.
Resu lts a n d Discu ssion
The preparations of the bis(amido)zirconium and
-hafnium dichlorides and difluorides (1a ,b, 3a ,b) and
the amido(pentamethylcyclopentadienyl)zirconium and
-hafnium dichlorides and difluorides (2a ,b, 4a ,b) are
outlined in Scheme 1. All compounds were isolated as
spectroscopically pure, crystalline materials after re-
crystallization from hexane. It was found that the bis-
(amido) dichlorides (1a ,b) could be prepared from either
MCl4 or MCl4‚2THF (M ) Zr, Hf). Throughout this
paper Ar ) 2,6-iPr2C6H3.
Work in our research group has shown that the ligand
(2,6-diisopropylphenyl)(trimethylsilyl)amide provides sys-
tems with increased solubility. Use of this ligand in
compounds 1-4 would thus ensure the complete homo-
geneity of catalyst solutions for the polymerization of
olefins, particularly in the case of the fluorides. Despite
the steric demand of the amido ligand, it was still
possible to synthesize the bis(amido) compounds of
zirconium and hafnium (1a ,b, 3a ,b).
Compound 3a crystallizes with two independent
molecules in the asymmetric unit. Each of the Zr atoms
(25) Bai, Y.; Roesky, H. W.; Noltemeyer, M.; Witt, M. Chem. Ber.
1992, 125, 825.
(26) Arney, D. J .; Bruck, M. A.; Huber, S. R.; Wigley, D. E. Inorg.
Chem. 1992, 31, 3749.
(27) Druce, P. M.; Kingston, B. M.; Lappert, M. F.; Srivastava, R.
C.; Frazer, M. J .; Newton, W. E. J . Chem. Soc. A 1969, 2814.
The use of the trimethylsilyl group not only provides
a sterically demanding ligand but also makes it neces-
sary to prevent the formation of imido compounds. In
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3178 Organometallics, Vol. 15, No. 14, 1996
Ta ble 1. Selected Bon d Len gth s (Å) a n d An gles (d eg) for 1a ,b, 2b, a n d 3a
Shah et al.
1a
1b
2b
3a
Zr(1)-Cl(1) 2.380(1)
Zr(1)-Cl(2) 2.380(1)
Hf(1)-Cl(1) 2.344(1)
Hf(1)-Cl(2) 2.350(1)
Hf(1)-Cl(1) 2.364(1)
Hf(1)-Cl(2) 2.383(1)
Zr(1)-F(1) 1.946(3)
Zr(1)-F(2) 1.944(3)
Zr(2)-F(3) 1.948(3)
Zr(2)-F(4) 1.960(3)
Zr(1)-N(1) 2.029(2)
Zr(1)-N(2) 2.030(2)
Hf(1)-N(1) 2.028(3)
Hf(1)-N(2) 2.018(3)
Hf(1)-N(1) 2.054(3)
Hf(1)-C(Cp*)av 2.495(3)
Hf(1)-X(1A) 2.182(3)
Zr(1)-N(1) 2.068(4)
Zr(1)-N(2) 2.090(5)
Zr(2)-N(3) 2.067(5)
Zr(2)-N(4) 2.092(4)
Si(1)-N(1) 1.790(2)
Si(2)-N(2) 1.770(2)
N(1)-C(1) 1.460(3)
N(2)-C(13) 1.461(3)
Si(1)-N(1) 1.759(3)
Si(2)-N(2) 1.795(3)
N(1)-C(1) 1.473(5)
N(2)-C(13) 1.452(5)
Si(1)-N(1) 1.799(3)
N(1)-C(11) 1.462(5)
Si(1)-N(1) 1.767(5)
Si(2)-N(2) 1.767(5)
N(1)-C(1) 1.455(7)
N(2)-C(16) 1.451(7)
Zr(1)‚‚‚O(1) 2.250(4)
Zr(2)‚‚‚O(2) 2.241(4)
Cl(1)-Zr(1)-Cl(2) 103.0(1)
N(1)-Zr(1)-N(2) 118.2(1)
Cl(1)-Hf(1)-Cl(2) 103.9(1)
N(1)-Hf(1)-N(2) 117.6(1)
Cl(1)-Hf(1)-Cl(2) 101.9(1)
N(1)-Hf(1)-X(1A) 123.9(1)
F(1)-Zr(1)-F(2) 155.0(1)
N(1)-Zr(1)-N(2) 123.0(2)
F(3)-Zr(2)-F(4) 156.5(1)
N(3)-Zr(2)-N(4) 119.7(2)
Ta ble 2. Cr ysta l Da ta for 1a ,b, 2b, a n d 3a
1a
1b
2b
3a
formula
fw
cryst size (mm)
space group
a (Å)
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
C30H52Cl2N2Si2Zr
659.04
0.70 × 0.35 × 0.35
P21/n
11.816(2)
16.305(2)
18.366(2)
90
94.27(1)
90
3529(1)
4
C30H52Cl2N2Si2Hf
746.31
0.7 × 0.5 × 0.4
P21/n
11.879(2)
16.330(3)
18.375(4)
90
94.54(3)
90
3553(1)
4
C25H41Cl2NSiHf
633.07
0.7 × 0.5 × 0.3
P21/c
16.842(3)
9.494(2)
17.048(3)
90
90.61(3)
90
2726(1)
4
C34H60F2N2OSi2Zr
698.24
0.6 × 0.5 × 0.5
C2/c
35.180(7)
17.016(3)
25.580(5)
90
94.26(3)
90
15271(5)
8
Z
temp (K)
153(2)
1.241
0.551
213(2)
1.395
3.174
153(2)
1.543
4.079
213(2)
1.215
0.387
Fc (g mm-3
)
µ (mm-1
F(000)
)
1392
1520
1272
5952
2θ range (deg)
5-45
7-45
7-45
7-40
no. of rflns measd
no. of unique reflns
no. of restraints
no. of refined params
R1 (I > 2σ(I))
9236
9279
7042
7995
4619
0
348
0.0286
0.0698
0.0300; 1.50
0.73
4648
0
348
0.0250
0.0685
0.0404; 2.95
1.76
3565
0
278
0.0203
0.0534
0.0314; 2.36
2.06
7036
0
785
0.0448
0.1199
0.0533; 65.58
0.65
wR2a (all data)
g1; g2b
highest diff peak (e Å-3
)
a
2
b
2
wR2 ) {[∑w(Fc - Fo2)2]/[∑w(Fo2)2]}1/2
.
w-1 ) σ2(Fo2) + [(g1)P]2 + [(g2)P]; P ) [Fo + 2Fc2]/3.
in this pair of isomers coordinates a THF molecule
(Zr‚‚‚O ) 2.245(4) Å), with the oxygen lying on the plane
defined by the Zr atom and the two fluorines in both
molecules (deviations 0.03 and 0.06 Å). This results in
the wide F-Zr-F angles observed for the two inde-
pendent molecules of this species (155.1(1) and 156.5(1)°).
Work in the utilization of group 4 organometallic
fluorides as cataysts for the polymerization of olefins
has only recently been undertaken.29 This paper de-
scribes our initial studies of the catalytic potential of
complexes 1-4, with regard to ethylene polymerization.
Polymerization reactions, with methylaluminoxane
(MAO) as cocatalyst, were carried out at different Al:M
ratios under identical conditions. Table 3 summarizes
the polymerization results.
All reactions were carried out in 100 mL of toluene
in a magnetically stirred 250 mL reactor at room
temperature. After 30 min, the reactions were termi-
nated by injection of ethanol. As expected, the activities
of the amido cyclopentadienyl systems are much greater
than those of the bis(amido) systems, with the zirconium
complexes 2a and 4a proving to be the most active. In
comparison, the activities of the hafnium analogues (2b
and 4b) are poor.
The X-ray crystal structure of 4a was also determined,
indicating a structure similar to that of 2b. However,
the structure could not be fully refined (R1 ) 11%) and
no discussion of bond distances and angles is given.28
All the compounds described herein show the same
conformation of the N-bonded ligand, with the ring lying
on a plane perpendicular to the plane defined by the
Si-N-metal atoms. This conformation minimizes the
steric interactions between the two isopropyl groups and
the remaining atoms in the molecules.
(28) The compound was found to crystallize in the triclinic space
group P1h (a ) 9.216(5) Å, b ) 9.221(5) Å, c ) 35.230(5) Å, R ) 85.31(5)°,
â ) 78.87(5)°, γ ) 61.22(4)°), with two independent molecules in the
asymmetric unit.
(29) (a) Herzog, A.; Roesky, H. W.; Zak, Z.; Noltemeyer, M. Angew.
Chem. 1994, 106, 1035; Angew. Chem., Int. Ed. Engl. 1994, 33, 967.
(b) Shah, S. A. A.; Dorn, H.; Roesky, H. W. Unpublished results.
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Group 4 Metal Amido Fluorides and Chlorides
Organometallics, Vol. 15, No. 14, 1996 3179
Exp er im en ta l Section
All reactions were carried out under a dry nitrogen atmo-
sphere using standard Schlenk techniques. Solvents were
dried and purified by known procedures and distilled from
benzophenone ketyl under nitrogen prior to use. ZrCl4‚2THF,33
HfCl4‚2THF,33 (C5Me5)ZrCl3,34 (C5Me5)HfCl3,35 [2,6-iPr2C6-
H3N(SiMe3)Li],36 and Me3SnF37 were prepared according to
literature methods. ZrCl4 and HfCl4 were purchased (Aldrich)
and used without further purification. Methylaluminoxane
was obtained from Professor W. Kaminsky, Hamburg, Ger-
many, and used as a 10% solution by weight in toluene.
Ethylene (BASF AG) was polymerization grade and dried by
passing through columns of P4O10 prior to use.
NMR spectra were recorded on a Bruker AM 250 spectrom-
eter. C6D6 was trap-to-trap distilled from CaH2. 1H and 19F
NMR data are listed in ppm downfield from TMS and CFCl3,
respectively. IR spectra were recorded on a Perkin-Elmer Bio-
Rad Digilab FTS-7 spectrometer (Nujol mulls between CsI
plates). Mass spectra were obtained on a Finnigan MAT
System 8230 and a Varian MAT CH 5 mass spectrometer.
Melting points (uncorrected) were obtained by using a Bu¨chi
510 and an HWS-SG 3000 apparatus. Microanalyses were
performed by Beller Laboratory (Go¨ttingen, Germany) or in
our institute.
F igu r e 1. Crystal structure of 1a , with anisotropic
displacement parameters depicting 50% probability. All
the hydrogen atoms of the molecule have been omitted for
clarity.
[{2,6-iP r 2C6H3N(SiMe3)}2Zr Cl2] (1a ). To a suspension of
ZrCl4 (2.47 g, 10.6 mmol) or ZrCl4‚2THF (4.00 g, 10.6 mmol)
in diethyl ether (50 mL) was slowly added a solution of [2,6-
iPr2C6H3N(SiMe3)Li] (5.39 g, 21.1 mmol) in diethyl ether (50
mL), at 0 °C. After the mixture was stirred for 36 h and the
solvent was removed under reduced pressure, hexane (50 mL)
was added and the mixture filtered, removing LiCl. The clear,
pale yellow solution was concentrated to ∼25 mL and stored
at -25 °C overnight. A yield of 4.40 g (63%) of large, colorless
crystals was obtained (mp 132 °C). MS (m/z (relative intensity
(%), assignment)): 658 (5, M+), 248 (100, [2,6-iPr2C6H3N-
(SiMe3)]). IR (Nujol, cm-1): 1251 s, 1163 s, 1100 m, 891 m,
839 s, 784 s, 713 s, 679 m, 528 m, 431 m, 364 m. 1H NMR
(200 MHz, C6D6): δ 7.09 (s, 6H, Ph), 3.65 (sept, 4H, CH3CHCH3,
3
3J HH ) 6.73 Hz), 1.44 (d, 12H, CH3CHCH3, J HH ) 6.75 Hz),
1.12 (d, 12H, CH3CHCH3, 3J HH ) 6.68 Hz), 0.15 (s, 18H, SiMe3).
Anal. Calcd for C30H52Cl2N2Si2Zr: C, 54.7; H, 8.0; N, 4.3.
Found: C, 54.5; H, 7.9; N, 4.1.
F igu r e 2. Crystal structure of 2b, with anisotropic
displacement parameters depicting 50% probability. All
the hydrogen atoms of the molecule have been omitted for
clarity.
[{2,6-iP r 2C6H3N(SiMe3)}2HfCl2] (1b). The reaction was
performed by the same procedure described for the preparation
of 1a . HfCl4 (3.45 g, 10.77 mmol) or HfCl4‚2THF (5.00 g, 10.76
mmol) in diethyl ether (50 mL) was treated with a solution of
[2,6-iPr2C6H3N(SiMe3)Li] (5.50 g, 21.54 mmol) in diethyl ether
(50 mL), at 0 °C. After removal of LiCl by filtration, the clear,
colorless solution was concentrated to ∼25 mL and stored at
-25 °C overnight. A yield of 4.74 g (59%) of colorless crystals
was obtained (mp 148 °C). MS (m/z): 746 (3, M+), 73 (100,
[Me3Si]). IR (Nujol, cm-1): 1258 m, 1251 m, 1164 m, 1104 s,
892 m, 842 s, 785 s, 717 m, 523 m, 432 m, 358 m. 1H NMR
(200 MHz, C6D6): δ 7.08 (s, 6H, Ph), 3.72 (sept, 4H, CH3CHCH3,
The increase in activity of the dichloride complexes
with an increase in the amount of MAO used as
cocatalyst is consistent with the findings of Kaminsky,30
Chien,31 and Ewen.32 Remarkably, the activity of the
difluoride 4a initially remained unchanged as the ratio
Al:M was increased. For instance, there was a plateau
in activity for 4a between 1000:1 and 2000:1. As the
ratio reached 3000:1, the activity once more increased
as the amount of MAO increased.
3
3J HH ) 6.73 Hz), 1.42 (d, 12H, CH3CHCH3, J HH ) 6.75 Hz),
1.15 (d, 12H, CH3CHCH3, 3J HH ) 6.69 Hz), 0.14 (s, 18H, SiMe3).
Anal. Calcd for C30H52Cl2HfN2Si2: C, 48.3; H, 7.0; N, 3.8.
Found: C, 47.9; H, 7.1; N, 3.9.
Despite the visible differences in the polymerization
behavior of the dichloride (2a ) and the difluoride (4a ),
no clear trend is obvious. However, these differences
led us to investigate the catalytic activities of simple
metallocene difluorides compared to those of the corre-
sponding metallocene dichlorides, using lower concen-
trations of MAO.29b More detailed studies of the influ-
ence of the concentration of MAO on catalyst performance
are in progress.
[(C5Me5){2,6-iP r 2C6H3N(SiMe3)}Zr Cl2] (2a ). To a sus-
pension of (C5Me5)ZrCl3 (1.50 g, 4.51 mmol) in diethyl ether
(30 mL) was slowly added a solution of [2,6-iPr2C6H3N(SiMe3)-
Li] (1.15 g, 4.50 mmol) in diethyl ether (30 mL), at 0 °C. After
(33) Heyn, B.; Hippler, B.; Kreisel, G.; Scheer, H.; Walther, D.
Anorganische Synthesechemie; Springer-Verlag: Berlin, 1987.
(34) Wolczanski, P. T.; Bercaw, J . E. Organometallics 1982, 1, 793.
(35) Roddick, D. M.; Fryzuk, M. D.; Seidler, P. F.; Hillhouse, G. L.;
Bercaw, J . E. Organometallics 1985, 4, 97.
(36) Kennepohl, D. K.; Brooker, S.; Sheldrick, G. M.; Roesky, H. W.
Chem. Ber. 1991, 124, 2223.
(37) (a) J ohnson, W. K. J . Org. Chem. 1960, 25, 2253. (b) Levchuk,
L. E.; Sams, J . R.; Aubke, F. Inorg. Chem. 1972, 11, 43. (c) Krause, E.
Ber. Dtsch. Chem. Ges. 1918, 51, 1447.
(30) (a) Kaminsky, W.; Miri, M.; Sinn, H.; Woldt, R. Makromol.
Chem. Rapid Commun. 1983, 4, 417. (b) Kaminsky, W.; Ku¨lper, K.;
Niedoba, S. Makromol. Chem., Makromol. Symp. 1986, 3, 377.
(31) Chien, J . C. W.; Wang, B.-P. J . Polym. Sci. A: Polym. Chem.
1988, 26, 3089.
(32) Ewen, J . A. J . Am. Chem. Soc. 1984, 106, 6355.
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3180 Organometallics, Vol. 15, No. 14, 1996
Shah et al.
F igu r e 3. Crystal structure of 3a (two independent molecules in the asymmetric unit), with anisotropic displacement
parameters depicting 50% probability. All the hydrogen atoms of the two molecules have been omitted for clarity.
Ta ble 3. Eth ylen e P olym er iza tion w ith
(50 mL) was stirred at room temperature for 5 h. All the
volatiles were removed under reduced pressure to yield 1.01
g (85%) of colorless crystals after recrystallization from hexane
(mp 150 °C). MS (m/z): 624 (80, M+), 376 (100, [M - 2,6-
iPr2C6H3N(SiMe3)]). IR (Nujol, cm-1): 1251 s, 1171 m, 1159
m, 1102 m, 1039 m, 930 w, 894 s, 842 s, 787 s, 752 m, 720 s,
676 m, 610 m, 600 s, 532 m, 524 m, 426 m, 355 m. 1H NMR
(200 MHz, C6D6): δ 7.06 (s, 6H, Ph), 3.62 (sept, 4H, CH3CHCH3,
Com p ou n d s 1-4
amt of
mole ratio yield of activity 105 g PE/
catalyst catalyst (µmol)
Al:M
PE (g) (mol of M h atm)
1a
1b
2a
2a
2a
2a
2b
3a
3b
4a
4a
4a
4a
4a
4a
4b
18.7
12.2
14.7
11.9
9.3
1000:1
1000:1
500:1
1000:1
2000:1
3000:1
1000:1
1000:1
1000:1
500:1
0.122
0.13
0.237
0.889
1.113
1.134
0.051
0.186
0.32
1.49
2.38
4.76
0.06
0.09
3
3J HH ) 6.78 Hz), 1.35 (d, 12H, CH3CHCH3, J HH ) 6.79 Hz),
1.18 (d, 12H, CH3CHCH3, 3J HH ) 6.75 Hz), 0.22 (s, 18H, SiMe3).
4.7
19F NMR (188 MHz, C6D6): δ 109.6 (s). Anal. Calcd for
16.3
43.4
15.3
14.4
10.1
11.1
7.6
11.9
9.6
20.8
C
30H52F2N2Si2Zr: C, 57.5; H, 8.4; F, 6.1; N, 4.5. Found: C,
57.3; H, 8.5; F, 6.2; N, 4.3.
0.197
0.442
1.146
0.743
1.149
1.400
0.017
0.27
0.87
2.06
1.95
1.93
2.93
0.02
[{2,6-iP r 2C6H3N(SiMe3)}2HfF 2] (3b). A mixture of 1b
(1.50 g, 2.01 mmol) and Me3SnF (0.73 g, 3.99 mmol) was
reacted in toluene (40 mL) as described for 3a to yield 1.19 g
(83%) of colorless crystals (mp 144 °C). MS (m/z): 714 (20,
M+), 73 (100, [SiMe3]). IR (Nujol, cm-1): 1252 s, 1172 m, 1158
m, 1102 m, 1040 m, 895 m, 844 s, 789 s, 751 m, 724 m, 611 m,
601 s, 532 m, 525 m, 426 m. 1H NMR (200 MHz, C6D6): δ
750:1
1000:1
1500:1
2000:1
3000:1
1000:1
the mixture was stirred for 36 h and the solvent was removed
under reduced pressure, hexane (50 mL) was added and the
mixture filtered, removing LiCl. The filtrate was concentrated
to ∼20 mL and stored at -25 °C overnight. A yield of 1.63 g
(66%) of colorless crystals was obtained (mp 168 °C). MS (m/
z): 545 (5, M+), 162 (100, [C9H12NSi]). IR (Nujol, cm-1): 1251
s, 1163 s, 1100 m, 891 m, 839 s, 784 s, 713 s, 679 m, 528 m,
431 m, 364 m. 1H NMR (200 MHz, C6D6): δ 7.06 (s, 3H, Ph),
3
7.06 (s, 6H, Ph), 3.64 (sept, 4H, CH3CHCH3, J HH ) 6.78 Hz),
1.33 (d, 12H, CH3CHCH3, 3J HH ) 6.79 Hz), 1.18 (d, 12H, CH3-
CHCH3, 3J HH ) 6.77 Hz), 0.18 (s, 18H, SiMe3). 19F NMR (188
MHz, C6D6): δ 75.3 (s). Anal. Calcd for C30H52F2HfN2Si2: C,
50.5; H, 7.4; F, 5.3; N, 3.9. Found: C, 50.3; H, 7.3; F, 5.1; N,
3.8.
[(C5Me5){2,6-iP r 2C6H3N(SiMe3)}Zr F 2] (4a ). A mixture of
2a (1.36 g, 2.49 mmol) and Me3SnF (0.91 g, 4.98 mmol) was
reacted in toluene (40 mL) as described for 3a to yield 1.01 g
(79%) of colorless crystals (mp 85 °C). MS (m/z): 511 (20, M+),
248 (100, [2,6-iPr2C6H3N(SiMe3)]). IR (Nujol, cm-1): 1423 m,
1250 s, 1175 s, 1112 m, 1100 m, 874 m, 841 s, 779 m, 753 m,
711 m, 579 s, 571 m, 383 m. 1H NMR (200 MHz, C6D6): δ
3
3.63 (sept, 2H, CH3CHCH3, J HH ) 6.71 Hz), 1.87 (s, 15H,
C5Me5), 1.40 (d, 6H, CH3CHCH3, 3J HH ) 6.72 Hz), 1.20 (d, 6H,
CH3CHCH3, 3J HH ) 6.65 Hz), 0.32 (s, 9H, SiMe3). Anal. Calcd
for C25H41Cl2NSiZr: C, 55.0; H, 7.6; N, 2.6. Found: C, 54.8;
H, 7.7; N, 2.5.
[(C5Me5){2,6-iP r 2C6H3N(SiMe3)}HfCl2] (2b). The reaction
was performed by the same method described for the prepara-
tion of 2a , using (C5Me5)HfCl3 (1.00 g, 2.38 mmol) and [2,6-
iPr2C6H3N(SiMe3)Li] (0.60 g, 2.35 mmol). A yield of 1.16 g
(78%) of large, colorless crystals was obtained (mp 147 °C).
MS (m/z): 633 (10, M+), 248 (100, [2,6-iPr2C6H3N(SiMe3)]). IR
(Nujol, cm-1): 1253 s, 1168 s, 1108 m, 1041 m, 1030 w, 888
3
7.05 (s, 3H, Ph), 3.49 (sept, 2H, CH3CHCH3, J HH ) 6.76 Hz),
1.87 (s, 15H, C5Me5), 1.39 (d, 6H, CH3CHCH3, 3J HH ) 6.78 Hz),
3
1.19 (d, 6H, CH3CHCH3, J HH ) 6.70 Hz), 0.26 (s, 9H, SiMe3).
19F NMR (188 MHz, C6D6): δ 78.2 (s). Anal. Calcd for
C
25H41F2NSiZr: C, 58.5; H, 8.1; F, 7.4; N, 2.7. Found: C, 57.2;
H, 7.6; F, 7.6; N, 2.9.
1
m, 870 m, 843 s, 801 w, 780 s, 703 s, 683 m, 436 m, 357 w. H
[(C5Me5){2,6-iP r 2C6H3N(SiMe3)}HfF 2] (4b). A mixture of
2b (0.86 g, 1.36 mmol) and Me3SnF (0.50 g, 2.73 mmol) was
reacted in toluene (40 mL) as described for 3a to yield 0.66 g
(81%) of colorless crystals (mp 72 °C). MS (m/z): 601 (6, M+),
248 (100, [2,6-iPr2C6H3N(SiMe3)]). IR (Nujol, cm-1): 1251 s,
1175 m, 1112 m, 1101 m, 891 m, 874 m, 841 s, 781 s, 755 m,
714 m, 584 s, 570 s, 358 m. 1H NMR (200 MHz, C6D6): δ 7.06
NMR (200 MHz, C6D6): δ 7.07 (s, 3H, Ph), 3.57 (sept, 2H,
3
CH3CHCH3, J HH ) 6.71 Hz), 1.91 (s, 15H, C5Me5), 1.40 (d,
3
6H, CH3CHCH3, J HH ) 6.72 Hz), 1.23 (d, 6H, CH3CHCH3,
3J HH ) 6.64 Hz), 0.32 (s, 9H, SiMe3). Anal. Calcd for
C
25H41Cl2HfNSi: C, 47.4; H, 6.5; N, 2.2. Found: C, 47.5, H,
6.5; N, 2.0.
[{2,6-iP r 2C6H3N(SiMe3)}2Zr F 2] (3a ). A suspension of 1a
(1.25 g, 1.90 mmol) and Me3SnF (0.69 g, 3.77 mmol) in toluene
3
(s, 3H, Ph), 3.53 (sept, 2H, CH3CHCH3, J HH ) 6.76 Hz), 1.87
(s, 15H, C5Me5), 1.38 (d, 6H, CH3CHCH3, 3J HH ) 6.75 Hz), 1.21
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Group 4 Metal Amido Fluorides and Chlorides
Organometallics, Vol. 15, No. 14, 1996 3181
3
(d, 6H, CH3CHCH3, J HH ) 6.70 Hz), 0.29 (s, 9H, SiMe3). 19F
refined versus F2 by the least-squares method with all data
(SHELX-93).40 All non-hydrogen atoms were refined aniso-
tropically. The hydrogen atoms were included in the refine-
ment in ideal positions.
NMR (188 MHz, C6D6):
C25H41F2HfNSi: C, 50.0; H, 6.9; F, 6.3; N, 2.3. Found: C, 49.8;
H, 6.8; F, 6.3; N, 2.2.
δ 36.3 (s). Anal. Calcd for
Gen er a l P r oced u r e for P olym er iza tion Rea ction s. To
solutions of complexes 1-4 in toluene (10 mL) were added
appropriate amounts of MAO. After a prereaction time of 20
min, the catalyst solution was injected into a magnetically
stirred 250 mL reactor previously charged with toluene (100
mL), into which ethylene was bubbling at a pressure of 1 atm.
This pressure was maintained throughout the reaction. After
30 min, ethanol (10 mL) was injected into the reactor to
terminate the reaction. The polymer produced was filtered
off, washed with acidified ethanol, water, and ethanol and
dried at 60 °C for 24 h. To ensure reproducibility, polymeriza-
tions were carried out twice with each complex under identical
conditions.
Ack n ow led gm en t . We thank the Deutsche For-
schungsgemeinschaft and the BMBF for their generous
support. S.A.A.S. is grateful to the Alexander von
Humboldt Foundation for a postdoctoral fellowship, and
E.P. thanks the European Community for a post-
doctoral grant (No. ERB CHBG CT 940731).
Su p p or tin g In for m a tion Ava ila ble: For compounds 1a ,
2b, and 3a , tables of crystal data and structure refinement
details, atomic coordinates, displacement parameters, and all
bond distances and angles (23 pages). Ordering information
is given on any current masthead page.
X-r a y Str u ctu r e An a lyses for 1a ,b, 2b, 3a , a n d 4a . The
intensities for all the structures were collected by the ω-2θ
scan method on a Siemens AED2 four-circle diffractometer
using graphite-monochromated Mo KR radiation (λ ) 0.710 73
Å), according to the Learnt-Profile Method.38 All the struc-
tures were solved by direct methods (SHELXS-90)39 and
OM960177V
(38) Clegg, W. Acta Crystallogr., Sect. A 1983, 39, 158.
(39) Sheldrick, G. M. Acta Crystallogr., Sect. A 1990, 46, 467.
(40) Sheldrick, G. M. SHELXL-93; University of Go¨ttingen, Go¨ttin-
gen, Germany, 1993.
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