Weakly coordinating Al-, Nb-, Ta-, Y-, and La-based perfluoroaryloxymetalate anions as cocatalyst components for single-site olefin polymerization

Article abstract of DOI:10.1021/om020087s

Reaction of LiAlH₄, with 4.0 equiv of HOC₆F₅ in toluene leads to H₂ evolution and formation of Li⁺Al(OC₆F₅)₄^-; subsequent metathesis with Ph₃CCl then yields the corresponding trityl tetrakis(pentafluorophenoxo)aluminate, Ph₃C⁺Al(OC₆F₅)₄^- (4). The pentachlorides MCl₅ (M = Nb, Ta) undergo reaction with 6.0 equiv of LiOC₆F₅ in Et₂O to afford crystalline Li(OEt₂)_n⁺-{[M(OC₆F₅) ₄(μ₂-OC₆F₅)₂]₂ Li}·C₇H₈ salts (M = Nb, n = 4 (5a); M = Ta, n = 3 (5b)), which can be cleanly converted with Ph₃CCl to the corresponding mononuclear, thermally stable Ph₃C⁺M(OC₆F₅)₆^- salts (M = Nb (6a); M = Ta (6b)) in high yield. X-ray diffraction analysis of 6 reveals six-coordinate metal centers with substantial distortion of the M-O-C₆F₅ linkages from linearity. The reactivity and cocatalytic characteristics of 6 were investigated with respect to a series of metallocene dimethyls. For sterically unencumbered metallocenes, facile C₆F₅O^- transfer from Nb/Ta to Zr/Ti is observed. However, (C₅Me₅)₂ZrMe(THF-d₈)⁺-Nb( OC₆F₅)₆^- (7) is formed in the reaction of 6a with (C₅Me₅)₂ZrMe₂ in THF-d₈. In situ activation of (C₅Me₅)₂ZrMe₂ and (C₅Me₄H)₂ZrMe₂ with 4 and 6 yields efficient ethylene polymerization catalysts, having activities comparable to those of Ph₃C⁺B(C₆F₅)₄^- -activated systems under identical polymerization conditions. To impede aryloxide ring transfer, a bulkier ligand, 2-nonafluorobiphenoxide (C₁₂F₉O^-), was combined with highly oxophilic Y^3- and La³⁺ centers. Reaction of M[CH(SiMe₃)₂]₃ (M = Y, La) with 4.0 equiv of 2-HOC₁₂F₉ results in the clean formation of M(OC₁₂F₉)₃(HOC₁₂F₉) complexes (M = Y (9a); M = La, (9b)) in high yield. When 9 is paired with metallocene dimethyl precursors, even sterically open precatalysts such as CGCTiMe₂ (CGC = Me₂Si(C₅Me₄)^tBuN) or (C₅H₅)₂ZrMe₂ yield highly active ethylene polymerization systems.

Full text of DOI:10.1021/om020087s

Organometallics 2002, 21, 3691-3702
3691
Wea k ly Coor d in a tin g Al-, Nb-, Ta -, Y-, a n d La -Ba sed
P er flu or oa r yloxym eta la te An ion s a s Coca ta lyst
Com p on en ts for Sin gle-Site Olefin P olym er iza tion
Matthew V. Metz, Yimin Sun,† Charlotte L. Stern, and Tobin J . Marks*
Department of Chemistry, Northwestern University, 2145 Sheridan Road,
Evanston, Illinois 60208-3113
Received February 5, 2002
Reaction of LiAlH4 with 4.0 equiv of HOC6F5 in toluene leads to H2 evolution and formation
-
of Li+Al(OC6F5)4 ; subsequent metathesis with Ph3CCl then yields the corresponding trityl
tetrakis(pentafluorophenoxo)aluminate, Ph3C+Al(OC6F5)4- (4). The pentachlorides MCl5 (M
+
) Nb, Ta) undergo reaction with 6.0 equiv of LiOC6F5 in Et2O to afford crystalline Li(OEt2)n
-
{[M(OC6F5)4(µ2-OC6F5)2]2Li}‚C7H8 salts (M ) Nb, n ) 4 (5a ); M ) Ta, n ) 3 (5b)), which can
be cleanly converted with Ph3CCl to the corresponding mononuclear, thermally stable
Ph3C+M(OC6F5)6- salts (M ) Nb (6a ); M ) Ta (6b)) in high yield. X-ray diffraction analysis
of 6 reveals six-coordinate metal centers with substantial distortion of the M-O-C6F5
linkages from linearity. The reactivity and cocatalytic characteristics of 6 were investigated
with respect to a series of metallocene dimethyls. For sterically unencumbered metallocenes,
facile C6F5O- transfer from Nb/Ta to Zr/Ti is observed. However, (C5Me5)2ZrMe(THF-d8)+-
-
Nb(OC6F5)6 (7) is formed in the reaction of 6a with (C5Me5)2ZrMe2 in THF-d8. In situ
activation of (C5Me5)2ZrMe2 and (C5Me4H)2ZrMe2 with 4 and 6 yields efficient ethylene
-
polymerization catalysts, having activities comparable to those of Ph3C+B(C6F5)4 -activated
systems under identical polymerization conditions. To impede aryloxide ring transfer, a
bulkier ligand, 2-nonafluorobiphenoxide (C12F9O-), was combined with highly oxophilic Y3+
and La3+ centers. Reaction of M[CH(SiMe3)2]3 (M ) Y, La) with 4.0 equiv of 2-HOC12F9 results
in the clean formation of M(OC12F9)3(HOC12F9) complexes (M ) Y (9a ); M ) La, (9b)) in
high yield. When 9 is paired with metallocene dimethyl precursors, even sterically open
precatalysts such as CGCTiMe2 (CGC ) Me2Si(C5Me4)tBuN) or (C5H5)2ZrMe2 yield highly
active ethylene polymerization systems.
- 6
In tr od u ction
e.g., methylalumoxane (MAO),4 MArFxAr3-x,5 MArF
4
(M ) B, Al; ArF ) fluoroaryl group), etc., are combined
to form the active catalytic species consisting of a
cationic metal center and a weakly coordinating anion
(1). Due to their structurally well-defined chemical
In single-site R-olefin polymerization catalysis, a
precatalyst (usually a group 4-based metallocene or
similar complex)1,2 and a cocatalyst,3 typically group 13-
based and containing metal/metalloid-carbon bonds,
† Current address: Uniroyal Chemical Company, 280 Elm St.,
Building 310, Naugatuck, CT 06770.
(1) For recent reviews see: (a) Chum, P. S.; Kruper, W. J .; Guest,
M. J . Adv. Mater. 2000, 12, 1759-1767. (b) Gladysz, J . A., Ed. Chem.
Rev. 2000, 100 (special issue on “Frontiers in Metal-Catalyzed Polym-
erization”). (c) Marks, T. J ., Stevens, J . C., Eds. Top. Catal. 1999, 7, 1
(special volume on “Advances in Polymerization Catalysis. Catalysts
and Processes”). (d) Scheirs J .; Kaminsky, W. Metallocene-Based
Polyolefins: Preparation, Properties, and Technology; J ohn Wiley &
Sons: New York, 1999; Vols. 1 and 2. (e) Kaminsky, W. Metalorganic
Catalysts for Synthesis and Polymerization: Recent Results by Ziegler-
Natta and Metallocene Investigations; Springer-Verlag: Berlin, 1999.
nature and high cocatalytic activity, the perfluoro-
arylboranes, -borates, and -aluminates are of consider-
(f) J ordan, R. F. J . Mol. Catal. 1998, 128,
1
(special issue on
(3) For recent reviews of cocatalysts and weakly coordinating anions
see: (a) Pedeutour, J .-N.; Radhakrishnan, K.; Cramail, H.; Deffieux,
A. Macromol. Rapid Commun. 2001, 22, 1095-1123. (b) Chen, Y-. X.;
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10.1021/om020087s CCC: $22.00 © 2002 American Chemical Society
Publication on Web 08/09/2002

3692 Organometallics, Vol. 21, No. 18, 2002
Metz et al.
activity, thermal stability, chain transfer characteristics,
stereoselection, etc.4-6,8 Nevertheless, the number of
available cocatalyst families is currently rather limited
and has so far impeded a broad, systematic study of
cation-anion effects.
To truly broaden the available cocatalytic options for
single-site Ziegler-Natta olefin polymerization systems,
it is intriguing to inquire whether viable cocatalyst
anions devoid of group 13 elements and element-carbon
bonds can be synthesized and whether they form stable
catalytic species when paired with group 4 hydrocarbyls.
Recent results5i,j suggest that by increasing the steric
bulk of the cocatalyst anion, hence decreasing the
strength of localized ion pairing, catalyst systems with
much higher polymerization activities can be achieved.
To develop new, more sterically encumbered cocatalysts,
a linker was sought to introduce between the metal/
metalloid anionic center and an inert perfluoroaryl
periphery. Oxygen was chosen as the linker because it
forms very strong bonds to the early transition metal
and rare earth ions, which were in turn chosen as the
non-group 13 cores of the new cocatalyst structures.
Although oxygen and alcohols are known poisons for
homogeneous Ziegler-Natta polymerization systems, it
was hypothesized that by screening the oxygen atoms
with sterically encumbered perfluoroaryl substituents
and by decreasing the nucleophilicity of the oxygen
atoms with strongly electron-withdrawing perfluoroaryl
rings, stable cocatalyst anions could be formed. The
following contribution describes the synthesis, charac-
terization, and cocatalytic features of a new series of
sterically encumbered metalloid, transition metal, and
rare earth cocatalysts/counteranions based on penta-
fluorophenoxide (2; C6F5O-) and nonafluorobiphenoxide
(3; C12F9O-) substituents.9
F igu r e 1. Representative perfluoroaryl borane and borate
cocatalyst structures used in single-site olefin polymeriza-
tion.
able current scientific and technological interest (Figure
1). Experimental results to date, supported by theoreti-
cal analyses,7 argue that many of the properties of such
catalyst systems are intimately connected with the
nature of the cation-anion interaction in ways that are
presently not well-understood. The size, shape, charge,
electronic structure, and potential ligational character-
istics of the anion can have profound effects on catalyst
(5) (a) Chen, E. Y.-X.; Kruper, W. J .; Roof, G. R.; Wilson, D. R. J .
Am. Chem. Soc. 2001, 123, 745-746. (b) Zhou, J .; Lancaster, S. J .;
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Chem. Soc. 2001, 123, 223-237. (c) Metz, M. V.; Schwartz, D. J .; Stern,
C. L.; Nickias, P. N.; Marks, T. J . Angew. Chem., Int. Ed. 2000, 39,
1312-1316. (d) Chase, P. A.; Piers, W. E.; Patrick, B. O. J . Am. Chem.
Soc. 2000, 122, 12911-12912. (e) Klosin, J .; Roof, G. R.; Chen, E. Y.-
X.; Abboud, K. A. Organometallics 2000, 19, 4684-4686. (f) LaPointe,
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122, 9560-9561. (g) Williams, V. C.; Irvine, G. J .; Piers, W. E.; Li, Z.;
Collins, S.; Clegg, W.; Elsegood, M. R. J .; Marder, T. B. Organometallics
2000, 19, 1619-1621. (h) Williams, V. C.; Piers, W. E.; Clegg, W.;
Elsegood, M. R. J .; Collins, S.; Marder, T. B. J . Am. Chem. Soc. 1999,
121, 3244-3245. (i) Luo, L.; Marks, T. J . Top. Catal. 1999, 7, 97-106.
(j) Kohler, K.; Piers, W. E. Can. J . Chem. 1998, 76, 1249-1255. (k) Li,
L.; Marks, T. J . Organometallics 1998, 17, 3996-4003. (l) Chen, Y.-
X.; Metz, M. V.; Li, L.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc.
1998, 120, 6287-6305. (m) Deck, P. A.; Beswick, C. L.; Marks, T. J . J .
Am. Chem. Soc. 1998, 120, 1772-1784. (n) Temme, B.; Erker, G.; Karl,
J .; Luftmann, H.; Frohlich, R.; Kotila, S. Angew. Chem., Int. Ed. Engl.
1995, 34, 1755-1757. (o) Yang, X.; Stern, C. L.; Marks, T. J . J . Am.
Chem. Soc. 1994, 116, 10015-10031. (p) J ia, L.; Yang, X.; Stern, C.
L.; Marks, T. J . Organometallics 1994, 13, 3755-3757.
(6) (a) J ia, L.; Yang, X.; Stern, C. L.; Marks, T. J . Organometallics
1997, 16, 842-857. (b) Chien, J . C. W.; Tsai, W. M.; Rausch, M. D. J .
Am. Chem. Soc. 1991, 113, 8570-8571. (c) Yang, X.; Stern, C.; Marks,
T. J . Organometallics 1991, 10, 840-842. (d) Ewen, J . A.; Elder, M. J .
(Fina Technology, Inc.) Preparation of Metallocene Catalysts for
Polymerization of Olefins; EP0426637, May 8, 1991. (e) Hlatky, G. G.;
Upton, D. J .; Turner, H. W. (Exxon Chemical Patents, Inc.) Supported
Ionic Metallocene Catalysts for Olefin Polymerization; WO 9109882,
J uly 7, 1991. (f) Turner, H. W. (Exxon Chemical Patents, Inc.) Soluble
Catalysts for Polymerization of Olefins; EP 277004A1, Aug 3, 1988.
(7) (a) Lanza, G.; Fragala`, I. L.; Marks, T. J . Organometallics 2001,
20, 4006-4017. (b) Vanka, K.; Ziegler, T. Organometallics 2001, 20,
905-913. (c) Lanza, G.; Fragala`, I. L.; Marks, T. J . J . Am. Chem. Soc.
2000, 122, 12764-12777. (d) Chan, M. S. W.; Ziegler, T. Organome-
tallics 2000, 19, 5182-5189. (e) Rappe´, A. K.; Skiff, W. M.; Casewit,
C. J . Chem. Rev. 2000, 100, 1435-1456. (f) Vanka, K.; Chan, M. S.
W.; Pye, C.; Ziegler, T. Organometallics 2000, 19, 1841-1849. (g) Chan,
M. S. W.; Vanka, K.; Pye, C. C.; Ziegler, T. Organometallics 1999, 18,
4624-4636. (h) Lanza, G.; Fragala`, I. L. Top. Catal. 1999, 15, 45-60.
(i) Lanza, G.; Fragala`, I. L.; Marks, T. J . J . Am. Chem. Soc. 1998, 120,
8257-8258. (j) Fusco, R.; Longo, L.; Proto, A.; Masi; F.; Garbasi, F.
Macromol. Rapid Commun. 1998, 19, 257-262. (k) Fusco, R.; Longo,
L.; Masi, F.; Garbasi, F. Macromolecules 1997, 30, 7673-7685. (l)
Fusco, R.; Longo, L.; Masi, F.; Garbasi, F. Macromol. Rapid Commun.
1997, 18, 433-441.
The first class of perfluoroaryloxide cocatalyst anions
investigated was based on AlIII, NbV, and TaV centers
and the C6F5O- ligand. It will be seen that the trityl
salts [Ph3C]+[Al(OC6F5)4]- (4), [Ph3C]+[Nb(OC6F5)6]-
(6a ), and [Ph3C]+[Ta(OC6F5)6]- (6b) form active ethyl-
ene polymerization systems, but only when paired with
sterically demanding metallocenium cations. Facile
C6F5O- transfer to the cationic metallocene occurs when
less encumbered metallocenes, such as (C5H5)2ZrMe2,
(8) (a) Shiomura, T.; Uchikawa, N.; Asanuma, T.; Sugimoto, R.;
Fujio, I.; Kimura, S.; Harima, S.; Akiyama, M.; Kohno, M.; Inoue, N.
In Metallocene-Based Polyolefins; Scheirs, J ., Kaminsky, W., Eds.; J ohn
Wiley & Sons Ltd.: Chichester, UK, 2000; Vol. 1, pp 437-465. (b)
Rhodes, B.; Chien, J . C. W.; Rausch, M. D. Organometallics 1998, 17,
1931-1933. (c) Shiomura, T.; Asanuma, T.; Inoue, N. Macromol. Rapid
Commun. 1996, 17, 9-14. (d) Giardello, M. A.; Eisen, M. S.; Stern, C.
L.; Marks, T. J . J . Am. Chem. Soc. 1995, 117, 12114-12129. (e) Siedle,
A. R.; Hanggi, B.; Newmark, R. A.; Mann, K. R.; Wilson, T. Macromol.
Symp. 1995, 89, 299-305. (f) Eisch, J . J .; Pombrik, S. I.; Gurtzgen, S.;
Rieger, R.; Uzick, W. Stud. Surf. Sci. Catal. 1994, 89, 221-235.
(9) Portions of this work previously communicated: Sun, Y.; Metz,
M. V.; Stern, C. L.; Marks, T. J . Organometallics 2000, 19, 1625-1627.

Perfluoroaryloxymetalate Anions
Organometallics, Vol. 21, No. 18, 2002 3693
19F), or Mercury 400 (FT 400 MHz, 1H; 100 MHz, 13C; 376 MHz,
are employed as organo-group 4 catalysts. To expand
the scope of perfluorophenoxide cocatalysts and to
improve their catalytic versatility, it was necessary to
reduce phenoxide group transfer to the metallocene.
This was accomplished in two ways. To increase the
steric bulk of the cocatalyst anions, pentafluorophenox-
ide ligands were replaced with more sterically encum-
bered nonafluorobiphenoxide ligands. To decrease the
propensity for perfluoroaryloxide ring transfer to the
metallocenium components, trivalent lanthanides were
chosen as the central core because of their high oxophi-
licity. Thus, cocatalysts Y(OC12F9)3(HOC12F9) (9a ) and
La(OC12F9)3(HOC12F9) (9b) were synthesized and stud-
ied as homogeneous single-site polymerization cocata-
lysts. The present results demonstrate that effective
cocatalysts need not contain metalloid/metal-carbon
bonds and that the properties of the resulting metallo-
cenium cation-anion pairs are sensitive to both the
counteranion core structure as well as to the metal-
locene ancillary ligation.9
1
19F) instruments. Chemical shifts for H and 13C spectra were
referenced to internal solvent resonances and are reported
relative to tetramethylsilane. 19F NMR spectra were referenced
to external CFCl3. NMR experiments on air-sensitive samples
were conducted in Teflon valve-sealed sample tubes (J . Young).
Elemental analyses were performed by Midwest Microlab,
Indianapolis, IN. Melting temperatures of polymers were
measured by DSC (DSC 2920, TA Instruments, Inc.) from the
second scan with a heating rate of 10 °C/min. GPC analyses
of polymers were recorded by Dow Chemical Company on a
Waters Alliance GPCV 2000 relative to polystyrene standards.
Syn th esis of P h 5C+Al(OC6F 5)4- (4). A solution of LiAlH4
(2.0 mL, 1.0 M, 2.0 mmol) in Et2O was added to a Schlenk
flask via syringe. At room temperature, a solution of C6F5OH
(6.7 mL, 1.2 M, 8.4 mmol) in toluene was added to a slurry of
the LiAlH4 in toluene (50 mL). The mixture was heated to 85
°C and stirred overnight. After removing the solvent under
vacuum, the flask was transferred to the glovebox, and solid
Ph3CCl (0.552 g, 1.98 mmol) was added to the flask. The flask
was next transferred from the glovebox to the high-vacuum
line. Under vacuum, pentane (35 mL) was condensed in. The
mixture was allowed to warm to room temperature and then
stirred for 4 h. Removing the solvent under vacuum gave dark
red material. Extraction with CH2Cl2 (20 mL), filtration,
evaporation of the solvent, and washing with pentane gave
Ph3C+Al(C6F5)4-, a bright-red oily material (0.58 g), in 29%
Exp er im en ta l Section
Ma ter ia ls a n d Meth od s. All manipulations of air-sensitive
materials were carried out with rigorous exclusion of oxygen
and moisture in flame-dried Schlenk-type glassware on a dual-
manifold Schlenk line interfaced to a high-vacuum line (10-6
Torr) or in a nitrogen-filled Vacuum Atmospheres glovebox
with a high capacity recirculator (<1 ppm of O2). Argon
(Matheson, prepurified), ethylene (Matheson, polymerization
grade), and propylene (Matheson, polymerization grade) were
purified by passage through a Matheson Gas Products OX-
ISORB-W column or by passage through a supported MnO
oxygen-removal column and an activated Davison 4 Å molec-
ular sieve column. All solvents were distilled before use under
dry nitrogen over appropriate drying agents (Et2O, THF, from
sodium benzophenone ketyl; pentane, hexane, toluene from
Na/K alloy or by passage though solvent purification col-
umns;10 CH2Cl2, from CaH2). All solvents for high-vacuum line
manipulations were subsequently stored in vacuo over Na/K
alloy for nonhalogenated solvents or over P2O5 for halogenated
solvents, in Teflon-valved bulbs. Benzene-d6, toluene-d8, me-
thylenechloride-d2, and THF-d8 (Cambridge Laboratories; all
99+ atom % D) used for NMR-scale reactions were stored in
vacuo over Na/K alloy (benzene-d6, THF-d8) or over Davison
4 Å molecular sieves (methylenechloride-d2) in resealable bulbs
and were vacuum transferred immediately prior to use. The
reagent C6F5Br (Aldrich) was vacuum distilled from P2O5 prior
to use. The reagents TiCl4, ZrCl4, BCl3 (gas or 1.0 M in
hexanes), LiAlH4, n-BuLi (1.6 M in hexanes), MeLi (1.0 M in
diethyl ether), MCl5 (M ) Nb, Ta), C6F5OH, Ph3CCl, and 50%
H2O2 were purchased from Aldrich and used as received except
that C6F5OH was dried over Davison 4 Å molecular sieves as
1
yield. H NMR (CD2Cl2, 23 °C): δ 8.27(t, 1 H, J H-H ) 7.5 Hz),
7.89(tr, 2 H, J H-H ) 8.0 Hz), 7.66(d, 2 H, J H-H ) 8.2 Hz). 19F
NMR (CD2Cl2, 23 °C): δ -162.04 (d, 2 F, o-F, J F-F ) 21.4 Hz),
-166.72 (tr, 2 F, p-F, J F-F ) 20.6 Hz), -173.81 (tr, br, 1 F,
m-F). Anal. Calcd for
C43H15O4F20Al: C, 51.51; H, 1.51.
Found: C, 50.90; H, 1.48.
Syn th esis of Li(OEt2)4+{[Nb(OC6F 5)4(µ2-OC6F 5)2]2Li}‚
C7H8 (5a ). Solid NbCl5 (0.765 g, 2.83 mmol) and LiOC6F5 (3.23
g, 6 × 2.83 mmol) were added to a reaction flask in the
glovebox. The flask was next transferred from the glovebox to
the high-vacuum line. On the vacuum line, Et2O (50 mL) was
condensed in, and the mixture stirred overnight at room
temperature. After removing the Et2O under vacuum, toluene
(50 mL) was condensed in, and the solution was heated to 50
°C and filtered. Slow cooling of the solution to -20 °C afforded
yellow crystalline [Li(OEt2)4]+{[Nb(OC6F5)4(µ2-OC6F5)2]2Li}--
1
(C7H8) (2.0 g) in 51% yield. H NMR (C6D6, 23 °C): δ 3.04 (q,
4 H, O(CH2CH3)2 J H-H ) 7.1 Hz), 0.84 (tr, 6 H, O(CH2CH3)2
J H-H ) 7.1 Hz). 19F NMR (C6D6, 23 °C): δ -161.6 (br d, 2 F,
o-F), -163.8 (br, 3 F, p/ m-F). Anal. Calcd for C95H48O16F60
-
Li2Nb2: C, 40.97; H, 1.74; F, 40.93. Found: C, 41.36; H, 1.58;
F, 40.71.
Syn th esis of P h 3C+Nb(OC6F 5)6 (6a ). Li(OEt2)4+{[Nb-
-
(OC6F5)4(µ2-OC6F5)2]2Li}‚C7H8 (1.91 g, 6.84 × 10-4 mol) and
Ph3CCl (0.389 g, 2 × 6.89 × 10-4 mol) were added to a reaction
flask in the glovebox. The flask was next transferred from the
glovebox to the high-vacuum line. On the vacuum line, pentane
(50 mL) was condensed in. The mixture was then allowed to
a
pentane solution, and Ph3CCl was recrystallized from
pentane. The organometallic reagents Y(CH(SiMe3)2)3,11 La-
(CH(SiMe3)2)3,12 Cp2ZrMe2,13 Me2Si(C5Me4)(tBuN)TiMe2,14 (CGC-
TiMe2), CGCZrMe2,14 Me2Si(Ind)2ZrMe2,15 (C5Me4H)2ZrMe2,16
(14) (a) Stevens, J . C.; Timmers, F. J .; Wilson, D. R.; Schmidt, G.
F.; Nickias, P. N.; Rosen, R. K.; Knight, G. W.; Lai, S. Y. (Dow Chemical
Co.) Constrained Geometry Addition Polymerization Catalysts, Pro-
cesses for Their Preparation, Precursors Therefor, Methods of Use, and
Novel Polymers Formed Therewith; EP0416815, Mar 13, 1991. (b)
Canich, J . M.; Hlatky, G. G.; Turner, H. W. (Exxon Chemical Patents,
Inc.) Aluminum-Free Monocyclopentadienyl Metallocene Catalysts for
Olefin Polymerization; WO-9200333 A2, J an 9, 1992. (c) Canich, J . A.
M. (Exxon Chemical Patents, Inc.) Olefin Polymerization Catalysts; EP-
420436A1, April 3, 1991.
(C5Me5)2ZrMe2,16 and Ph3C+B(C6F5)4
published procedures.
were prepared by
-
17
P h ysica l a n d An a lytica l Mea su r em en ts. NMR spectra
were recorded on Varian VXR 300 (FT 300 MHz, 1H; 75 MHz,
13C), Gemini-300 (FT 300 MHz, 1H; 75 MHz, 13C; 282 MHz,
(10) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J . Organometallics 1996, 15, 1518-1520.
(11) Barker, G. K.; Lappert, M. F. J . Organomet. Chem. 1974, 76,
C45-C56.
(12) Hitchcock, P. B.; Lappert, M. F.; Smith, R. G.; Bartlett, R. A.;
Power, P. P. J . Chem. Soc., Chem. Commun. 1988, 1007-1009.
(13) Samuel, E.; Rausch, M. D. J . Am. Chem. Soc. 1973, 95, 6263-
6267.
(15) (a) Herrmann, W. A.; Herdtweck, E.; Winter, A.; Spaleck, W.;
Rohrmann, J . Angew. Chem., Int. Ed. Engl. 1989, 28, 1511-1512. (b)
Herfert, N.; Fink, G. Makromol. Chem., Rapid Commun. 1993, 14, 91-
96.
(16) Manriquez, J . M.; McAlister, D. R.; Sanner, R. D.; Bercaw, J .
E. J . Am. Chem. Soc. 1978, 100, 2716-2724.
(17) Chien, J . C. W.; Tsai, W. M.; Rausch, M. D. J . Am. Chem. Soc.
1991, 113, 8570-8571.

3694 Organometallics, Vol. 21, No. 18, 2002
Metz et al.
-
warm to room temperature and stirred for 4 h. Subsequent
removal of the solvent under vacuum afforded an orange
powder. The powder was dissolved in CH2Cl2 (20 mL) and
centrifuged to remove precipitated LiCl. The clear CH2Cl2
solution was decanted, then concentrated to about 10 mL, and
pentane (30 mL) was transferred in under vacuum, layering
it on top of the CH2Cl2 solution. Diffusion at room temperature
B(C6F5)4 in C6D5Br: δ 1.55 (s, 30 H, C5Me5), 0.06 (s, 3 H,
Zr-Me).18
In Situ Gen er a tion of Meta llocen e P en ta flu or op h en -
oxid e Com p lexes. The reagent C6F5OH (35 mg) was charged
into a 5.0 mL volumetric flask, and C6D6 was added until the
total volume reached 5.0 mL. Next, 6.2 mg of rac-Me2Si-
(Ind)2ZrMe2 was charged into a serum-capped NMR tube, and
0.7 mL of C6D6 was added. 1H and 19F NMR spectra of the
NMR tube were then recorded after the successive addition of
0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 1.2 mL aliquots of
the C6F5OH/C6D6 solution (0.1 mL is approximately equal to
0.25 molar equiv of C6F5OH:Zr complex).
overnight gave red crystalline Ph3C+Nb(OC6F5)6 (1.97 g) in
-
95% yield. 1H NMR (CD2Cl2, 23 °C): δ 8.28 (tr tr, 1 H, m-C6H5,
J H-H ) 7.5/1.3 Hz), 7.89 (tr m, 2 H, p-C6H5, J H-H ) 8.0 Hz),
7.67 (d m, 2 H, o-C6H5, J H-H ) 8.5 Hz). 19F NMR (CD2Cl2, 23
°C): δ -158.90 (d, 2 F, o-F, J F-F ) 17.2 Hz), -165.99 (tr, 2 F,
p-F, J F-F ) 20.6 Hz), -169.56 (tr, 1 F, m-F, J F-F ) 22.0 Hz).
Anal. Calcd for C55H15O6F30Nb: C, 46.05; H, 1.05; F, 39.73.
Found: C, 45.69; H, 1.16; F, 40.13.
The initial aliquot of C6F5OH forms structures assignable
to both rac-Me2Si(Ind)2Zr(OC6F5)Me [19F NMR (C6D6, 23 °C):
δ -163.47 (dd, 2 F, o-F, 3J FF ) 19.2 Hz, 4J FF ) 7.6 Hz), -167.42
3
3
Syn th esis of Li(OEt2)3+{[Ta (OC6F 5)4(µ2-OC6F 5)2]2Li}‚
C7H8 (5b). Solid TaCl5 (0.990 g, 2.76 mmol) and LiOC6F5 (3.14
g, 6 × 2.76 mmol) were added to a reaction flask in the
glovebox. The flask was next transferred from the glovebox to
the high-vacuum line. On the vacuum line, Et2O (50 mL) was
condensed in, and mixture stirred overnight at room temper-
ature. After removing the Et2O under vacuum, toluene (50 mL)
was condensed in. The solution was next heated to 50 °C and
filtered. Slow cooling of the filtrate to -20 °C gave yellow
crystalline [Li(OEt2)3]+{[Ta(OC6F5)4(µ2-OC6F5)2]2Li}‚C7H8 (3.1
g) in 78% yield. 1H NMR (C6D6, 23 °C): δ 3.04 (q, 4 H, O(CH2-
CH3)2 J H-H ) 7.1 Hz), 0.84 (tr, 6 H, O(CH2CH3)2 J H-H ) 7.1
(dd, 2 F, m-F, J FF ) 22.9 Hz, J FF ) 19.2 Hz), -173.85 (tt, 1
3 4
F, p-F, J FF ) 22.9 Hz, J FF ) 7.1 Hz)] and rac-Me2Si(Ind)2Zr-
(OC6F5)2 [19F NMR (C6D6, 23 °C): δ -163.66 (dd, 2 F, o-F, 3J FF
4
3
) 16.8 Hz, J FF ) 3.8 Hz), -167.04 (dd, 2 F, m-F, J FF ) 22.9
Hz, 3J FF ) 19.2 Hz), -173.05 (tt, 1 F, p-F, 3J FF ) 22.4 Hz, 4J FF
) 6.6 Hz)] in a 6:1 ratio, respectively. The second through
fourth aliquots of C6F5OH solution continue to form the same
products in similar ratios. Aliquots 5 and 6 show increased
amounts of rac-Me2Si(Ind)2Zr(OC6F5)2 relative to rac-Me2Si-
(Ind)2Zr(OC6F5)Me. The seventh aliquot shows >95% of the
rac-Me2Si(Ind)2Zr(OC6F5)2 product. Further aliquots show free
C6F5OH [19F NMR (C6D6, 23 °C): δ -163.95 (dd, 2 F, o-F, 3J FF
4
3
Hz). 19F NMR (C6D6, 23 °C): δ -162.26 (br d, 2 F, o-F, J F-F
)
) 18.6 Hz, J FF ) 5.1 Hz), -165.00 (dd, 2 F, m-F, J FF ) 22.2
Hz, 3J FF ) 18.2 Hz), -179.56 (tt, 1 F, p-F, 3J FF ) 22.9 Hz, 4J FF
) 5.6 Hz)] in solution.
18.4 Hz), -163.73 (tr, 2 F, p-F, J F-F ) 21.2 Hz), -164.33 (tr,
1 F, m-F, J F-F ) 22.3 Hz). Anal. Calcd. for C91H38O15F60Li2-
Ta2: C, 37.86; H, 1.33; F, 39.48. Found: C, 37.95; H, 1.35; F,
38.98.
Syn th esis of Non a flu or obip h en yl-2-ol (P BOH). The
reagent 2-bromononafluorobiphenyl (21.0 g, 0.053 mol) was
charged into a reaction flask interfaced to a Schlenk line, and
150 mL each of freshly distilled Et2O and pentane were added
via syringe. The solution was next cooled to -78 °C and
n-butyllithium (33.2 mL, 1.6 M in hexanes, 0.053 mol) added.
The reaction mixture was stirred for 3 h at -78 °C, boron
trichloride (17.7 mL, 1.0 M in hexanes, 0.017 mol) was added,
and the reaction mixture was stirred overnight. Solvent was
then removed in vacuo, 100 mL of 50% H2O2 (Ca u tion : 50%
H2O2 is dangerous; proper handling is required) containing 3.0
g of KOH was added at 0 °C, and the reaction mixture was
stirred for 12 h. The product was then extracted with CH2Cl2,
solvent was removed, and distillation at 120 °C/10-6 Torr gave
9.0 g of PBOH in 51% yield as a colorless oil. 19F NMR (C6D6,
-
Syn th esis of P h 3C+Ta (OC6F 5)6 (6b). Li(OEt2)3+{[Ta-
(OC6F5)4(µ2-OC6F5)2]2Li}‚C7H8 (0.689 g, 2.39 × 10-4 mol) and
Ph3CCl (0.137 g, 2 × 2.46 × 10-4 mol) were added to a reaction
flask in the glovebox. The flask was next transferred from the
glovebox to the high-vacuum line. On the vacuum line, pentane
(50 mL) was condensed in. The mixture then was allowed to
warm to room temperature and stirred for 4 h. Subsequent
removal of the solvent under vacuum gave an orange powder.
The powder was dissolved in CH2Cl2 (20 mL) and centrifuged
to remove precipitated LiCl. After decanting, the clear CH2-
Cl2 solution was concentrated to about 10 mL and pentane
(30 mL) was transferred in under vacuum, layering it on top
of the CH2Cl2 solution. Diffusion at room temperature over-
3
night gave red crystalline Ph3C+Ta(OC6F5)6 (0.52 g) in 72%
-
25 °C): δ -139.07 (d, 2 F, F-2′/6′), J FF ) 22.6 Hz), - 139.74
3
3
yield. 1H NMR (CD2Cl2, 23 °C): δ 8.28 (tr tr, 1 H, m-C6H5,
J H-H ) 7.5/1.3 Hz), 7.89 (tr m, 2 H, p-C6H5, J H-H ) 8.0 Hz),
7.67 (d m, 2 H, o-C6H5, J H-H ) 8.5 Hz). 19F NMR (CD2Cl2, 23
°C): δ -159.40 (d, 2 F, o-F, J F-F ) 17.2 Hz), -166.02 (tr, 2 F,
p-F, J F-F ) 21.2 Hz), -170.01 (tr, 1 F, m-F, J F-F ) 21.7 Hz).
Anal. Calcd for C55H15O6F30Ta: C, 43.39; H, 0.99; F, 37.43.
Found: C, 42.59; H, 1.02; F, 37.72.
(d, 1 F, F-3, J FF ) 23.7 Hz), -151.95 (t, 1 F, F-4′, J FF ) 21.4
3
Hz), -153.36 (t, 1 F, F-4, J FF ) 21.7 Hz), -161.94 (dd, 2 F,
3
4
F-3′/5′, J FF ) 22.8 Hz, J FF ) 7.1 Hz), -162.97 (dd, 1 F, F-6,
3J FF ) 21.2 Hz, J FF ) 8.7 Hz), -167.23 (t, 1 F, F-5, J FF
)
4
3
1
22.7 Hz). H NMR (C6D6, 25 °C): δ 4.27 (s, 1 H). Anal. Calcd.
for C12F9OH: C, 43.40; H, 0.30. Found: C, 43.88; H, 0.77.
Syn th esis of Y(P BO)3(P BOH) (9a ). Solid Y[CH(SiMe3)2]3
(0.254 g, 4.48 × 10-4 mol) was charged into a reaction flask in
the glovebox. The flask was then transferred to the high-
vacuum line. Under vacuum, hexanes (25 mL) were condensed
in. At -78 °C, a pentane solution of PBOH (0.595 g, 4 × 4.48
× 10-4 mol, 10 mL) was then added slowly via syringe. The
mixture was stirred for 30 min at -78 °C, then slowly warmed
to room temperature and stirred for an additional 2 h.
Filtration, washing with pentane, and drying under vacuum
Tr a p p in g of a Meta llocen iu m In ter m ed ia te. To inves-
tigate the possible intermediacy of a cationic metallocene/anion
complex in the activation process, (C5Me5)2ZrMe2 (5.0 mg, 1.28
-
× 10-2 mmol) and Ph3C+Nb(OC6F5)6 (18.3 mg, 1.28 × 10-2
mmol) were weighed into a J . Young NMR tube in the
glovebox. The tube was brought out of the box and interfaced
to a high-vacuum line, and tetrahydrofuran-d8 was condensed
in at -78 °C. The tube was warmed to room temperature, and
NMR spectra were immediately recorded. 1H and 19F NMR
data (THF-d8, 23 °C): δ 2.01 (s, 30 H, C5Me5), 0.40 (s, 3 H,
Zr-Me). 19F NMR (THF-d8, 23 °C): δ -157.26 (d, 2 F, o-F, J F-F
) 18.1 Hz), -165.38 (tr, 2 F, p-F, J F-F ) 20.6 Hz), -169.14
(tr, 1 F, m-F, J F-F ) 22.9 Hz). The 19F NMR data reveal that
the Nb(OC6F5)6- anion is intact and that no OC6F5- rings have
been transferred to the cationic metallocene. The 1H NMR
shows an activated metallocene with characteristic downfield
gave an off-white powder of Y(PBO)3(PBOH) in 80% yield. 19
F
NMR (C6D6, 25 °C): δ -136.0 (br, s, 4 F), -140.0 (br, s, 8 F),
-151.3 (br, s, 4 F), -154.9 (br, s, 4 F), -161.3 (br, s, 8 F),
1
-162.1 (br, s, 4 F), -167.2 (br, s, 4 F). H NMR (C6D6, 25 °C):
δ 4.19 (s, H+). Anal. Calcd for C48HO4F36Y: C, 40.76; H, 0.07;
F, 48.36. Found: C, 40.39; H, 0.54; F, 48.46.
Syn th esis of La (P BO)3(P BOH) (9b). On the high-vacuum
line, a pentane solution of La[CH(SiMe3)2]3 (0.561 g, 9.09 ×
1
shifts for all protons. The H data are also consistent with the
published 1H NMR data reported for (C5Me5)2ZrMe(THF)+-
(18) Horton, A. D. Organometallics 1996, 15, 2675-2677.

Perfluoroaryloxymetalate Anions
Organometallics, Vol. 21, No. 18, 2002 3695
10-4 mol) was charged into a reaction flask and cooled to -78
°C, and a pentane solution of PBOH (1.208 g, 4 × 9.09 × 10-4
mol, 25 mL) was added slowly via syringe. The mixture was
immediately warmed to room temperature and stirred for an
additional 2 h. Filtration, washing with pentane, and drying
under vacuum gave an off-white powder of La(PBO)3(PBOH)
in 56% yield. 19F NMR (C6D6, 25 °C): δ -136.7 (br, s, 1 F),
-140.2 (br, s, 2 F), -151.2 (br, s, 1 F), -155.5 (br, s, 1 F),
structure was solved by direct methods, the structure solution
was expanded through successive least-squares cycles, absorp-
tion corrections were applied, and the final solution was
determined. Further details of the structural refinements are
given in Tables 2, 5, and 8 and in the Supporting Information.
Eth ylen e, P r op ylen e P olym er iza tion Exp er im en ts.
This polymerization procedure is designed to minimize mass
transfer (gas to solution; catalyst entrainment) and exotherm
effects while at the same time maintaining strictly vacuum
line-quality anaerobic/anhydrous conditions.5k,l,n,6a Polymeri-
zation activities of this magnitude measured by this procedure
have previously been found to be in reasonable agreement with
those measured in large-scale batch reactors.5c On the high
vacuum line (10-6 Torr), ethylene and propylene polymeriza-
tion reactions were carried out in 250 mL round-bottom three-
neck Morton flasks equipped with large magnetic stirring bars
and thermocouple probes. In a typical experiment (all experi-
ments were carried out in triplicate), toluene (100 mL) was
vacuum-transferred into the flask containing either (C5Me5)2-
ZrMe2 or (C5Me4H)2ZrMe2, and the reactor was saturated with
1.0 atm of ethylene or propylene (pressure control using an
Hg bubbler) and equilibrated at the desired reaction temper-
ature using an external water bath. A toluene solution (2 mL)
containing 1.0 equiv of cocatalyst was then quickly injected
into the rapidly stirred solution using a gastight syringe with
a flattened needle for spraying small droplets of solution. The
temperature of the toluene solution in polymerization experi-
ments was monitored using a thermocouple (OMEGA Type K
thermocouple with a Model HH21 microprocessor thermom-
eter). After a measured time interval (short to minimize mass
transport and exotherm effects), the polymerization was
quenched by the addition of 20 mL of acidified (2% HCl)
methanol. Another 100 mL of methanol was then added, and
the polymer was collected by filtration, washed with methanol,
and dried on the high-vacuum line overnight to a constant
weight.
Eth ylen e a n d P r op ylen e Cop olym er iza tion Exp er i-
m en ts. Using the polymerization setup described above, a
toluene solution (100 mL) of the catalyst was initially satu-
rated with 1.0 atm pressure of propylene at 25 °C. The vessel
was then reconfigured to admit 1.0 atm pressure of ethylene.
After saturation with ethylene at -78 °C for 5 min, the vessel
was warmed and equilibrated at 25 °C. A toluene solution (2
mL) containing 1.0 equiv of cocatalyst was then quickly
injected into the rapidly stirred flask using a gastight
syringe and the polymerization reaction subsequently
quenched with 20 mL of acidic methanol after a measured time
interval.
Alter n a tive P a r a llel P olym er iza tion P r oced u r e. To
increase the throughput of multiple polymerizations under
identical conditions and to improve the precision of multiple
polymerization runs, the following modified polymerization
protocol was employed. In the glovebox, three polymerization
reactors, 250 mL Morton style flasks equipped with type K
thermocouples and large magnetic stirring bars, were filled
with 100 mL of toluene (previously vacuum transferred from
Na/K alloy on a high-vacuum line) via a 100.0 mL volumetric
flask. The reactors were removed from the glovebox and then
interfaced to the high-vacuum line and an Omega OM-3001 4
channel thermocouple data logger. The data logger is config-
ured to record each channel every 0.6 s; channels 1-3 are the
respective polymerization reactors, and channel 4 is the water
bath. The three polymerization reactors were immersed in a
large-capacity water bath to control the temperature. The
reactors were degassed with successive vacuum cycles and
back-filled with 1.0 atm of monomer. In the glovebox, the
cocatalyst was weighed out and added to a 10.0 mL volumetric
flask, which was then filled with ca. 5 mL of toluene. The flask
was capped and shaken to completely dissolve the cocatalyst.
The catalyst precursor was then weighed out and added to the
volumetric flask, and toluene was added to bring the total
1
-160.7 (br, s, 2 F), -162.3 (br, s, 1 F), -168.6 (br, s, 1 F). H
NMR (C6D6, 25 °C): δ 4.20 (s, H+). Anal. Calcd for C48HO4F36
-
La: C, 39.37; H, 0.07; F, 46.71. Found: C, 39.03; H, 0.32; F,
45.47.
Rea ction of Cp 2Zr Me2 w ith Y(P BO)3(P BOH). In the
glovebox, Y(PBOH)(PBO)3 (30.1 mg, 2.12 × 10-2 mmol) and
Cp2ZrMe2 (5.3 mg, 2.12 × 10-2 mmol) were charged in to a J .
Young NMR tube, and toluene-d8 (ca. 1 mL) was added. The
solution immediately turned light yellow, and gas (CH4) was
evolved. The tube was then removed from the glovebox, and
NMR spectra were recorded within ca. 5 min. The solution
consisted of a complex mixture that appeared to contain Cp2-
ZrMe+, [Cp2ZrMe(µ-Me)MeZrCp2]+, and Cp2Zr(PBO)Me spe-
3
cies. 19F NMR (C7D8, 25 °C): δ -138.93 (d, 2 F, F-2′/6′), J FF
3
4
) 21.4 Hz), - 141.55 (d of d, 1 F, F-3, J FF ) 22.7, J FF ) 3.2
3
Hz), -153.74 (t, 1 F, F-4′, J FF ) 21.4 Hz), -155.08 (t, 1 F,
3
3
F-4, J FF ) 22.0 Hz), -162.57 (d of t, 2 F, F-3′/5′, J FF ) 22.1
4
3
Hz, J FF ) 7.1 Hz), -164.09 (d of t, 1 F, F-6, J FF ) 13.6 Hz,
3
4
4J FF ) 6.6 Hz), -171.07 (d of t, 1 F, F-5, J FF ) 22.1 Hz, J FF
) 4.6 Hz). Also present in the 19F NMR are broad (e.g., 1.0 to
3.0 ppm) peaks centered around -139, -155, and -162. 1H
NMR (C7D8, 25 °C): δ -1.23 (s, Cp2ZrMe(µ-CH3)Zr(Me)Cp2),
-0.16 (s, Cp2Zr(PBO)Me), 0.03 (s, Cp2ZrMe(µ-CH3)Zr(Me)Cp2),
0.18 (s, CH4) 0.49 (s, Cp2ZrMe+), 5.55 (s, Cp2Zr(PBO)Me), 5.65,
5.68 (s, Cp2ZrMe(µ-CH3)Zr(Me)Cp2), 5.80 (s, Cp2ZrMe+).
Rea ction of Cp 2Zr Me2 w ith P BOH. To verify the exist-
ence of Cp2Zr(PBO)Me in the reaction mixture of Cp2ZrMe2 +
Y(PBOH)(PBO)3, an authentic sample of Cp2ZrMe(PBO) was
generated. In the glovebox, Cp2ZrMe2 (5.0 mg, 1.99 × 10-2
mmol) and PBOH (6.6 mg, 1.99 × 10-2 mmol) were charged
into a J . Young NMR tube, and toluene-d8 was added.
Unreacted Cp2ZrMe2, Cp2Zr(PBO)Me, and Cp2Zr(PBO)2 can be
1
seen in the NMR in roughly a 3:6:1 ratio. H NMR: δ -0.21
(s, 6 H, Cp2ZrMe2), -0.20 (s, 3 H, Cp2Zr(PBO)Me), 5.57 (s, 10
H, Cp2Zr(PBO)Me), 5.61 (s, 10 H, Cp2Zr(PBO)2), 5.70 (s, 10 H,
Cp2ZrMe2). 19F NMR for Cp2Zr(PBO)Me (C7D8, 25 °C):
δ
-138.59 (d, 2 F, F-2′/6′), 3J FF ) 22.8 Hz), -141.55 (d, 1 F, F-3,
3J FF ) 23.1), -153.50 (t, 1 F, F-4′, 3J FF ) 21.3 Hz), -154.84 (t,
3
3
1 F, F-4, J FF ) 21.6 Hz), -162.37 (t, 2 F, F-3′/5′, J FF ) 21.4
3
Hz), -163.88 (d, 1 F, F-6, J FF ) 18.9 Hz), -170.90 (t, 1 F,
F-5, J FF ) 24.3 Hz). 19F NMR for Cp2Zr(PBO)2 (C7D8, 25 °C):
3
3
δ -138.35 (d, 4 F, F-2′/6′), J FF ) 21.4 Hz), -140.05 (d, 2 F,
F-3, 3J FF ) 24.3), -153.04 (t, 2 F, F-4′, 3J FF ) 21.2 Hz), -154.41
3
(t, 2 F, F-4, J FF ) 21.3 Hz), -162.12 (peak partially under a
Cp2Zr(PBO)Me peak) (t, 4 F, F-3′/5′, 3J FF ) 21.7 Hz), -163.12
3
3
(d, 2 F, F-6, J FF ) 21.2 Hz), -169.12 (t, 2 F, F-5, J FF ) 20.0
Hz).
Gen er al P r ocedu r e for Sin gle-Cr ystal Str u ctu r al Ch ar -
a cter iza tion of Com p ou n d s 5a , 5b, 6a , 6b, a n d 7. Inside
the glovebox, crystals were placed on a glass slide and covered
with dry Infineum V8512 (formerly Paratone-N) oil. The
crystals were then removed from the box, and a suitable crystal
was chosen under a microscope using plane-polarized light.
The crystal was mounted on a glass fiber and transferred to
the cold stage of a Bruker SMART 1000 CCD area detector
having a nitrogen cold-stream at 153(2) K. Twenty frames
(usually 20 s exposures, 0.3° slices) were collected in three
areas of reciprocal space to determine the orientation matrix.
The parameters for data collection were determined by the
peak intensities and widths from the 60 frames used to
determine the orientation matrix. The faces of the crystal were
then indexed, and data collection was started. After data
collection, the frames were integrated, the initial crystal

3696 Organometallics, Vol. 21, No. 18, 2002
Metz et al.
Sch em e 1. P r ep a r a tion of Com p lexes 5 a n d 6
volume of the solution to 10.0 mL. The flask was next capped
and shaken to ensure a homogeneous solution. Three aliquots
of the catalyst (usually 2.0 mL) were withdrawn from the flask
using 5.0 mL graduated, gastight syringes equipped with
deflected-point needles. The syringes were removed from the
glovebox with the needles inserted into silicone-capped, screw-
top vials, and the contents were rapidly injected into the
rapidly stirred polymerization reactors. After measured time
intervals, the polymerizations were quenched with 20 mL of
acidic (2% HCl) methanol. The polymer was precipitated with
100 mL of methanol, filtered, and dried to a constant weight
under vacuum.
In cases where catalyst lifetime was limited and activation
was known to be rapid, a modified procedure was employed.
The cocatalyst and precatalyst were prepared in separate 10.0
mL toluene solutions, and aliquots of the cocatalyst were added
to the reactors before they were removed from the glovebox.
Then, aliquots of the precatalyst were loaded into syringes,
and the remainder of the polymerization procedure was as
previously described (vide supra). These procedures increase
the precision of polymerization runs by ensuring the amount
and concentration of catalysts are equal for each run. Simul-
taneous utilization of the same solvent batch, monomer
stream, and water bath ensures polymerization conditions for
each reactor are as close as possible to the other reactors.
F igu r e 2. ORTEP plot (50% probabilities on thermal
ellipsoids) of polynuclear perfluorophenoxide complexes 5.
M ) Nb (5b).
(Tables 3, 4; bond angles and distances for 5a are
analogous) reveal a quasi-octahedral coordination ge-
ometry. Thus, trans O-Ta-O bond angles are 176.19-
(9)°, 172.94(8)°, and 171.62(7)°, and angles for cis
O-Ta-O range from 88.07(8)° to 95.38(9)° excluding
those involved in the square-planar Li+ atom coordina-
tion, 79.95(7)°, for the oxygen atoms bridging the group
5 metal and lithium centers. The four nonbridging
Ta-O distances range from 1.900(2) to 1.929(2) Å, while
the distances for the two oxygen atoms bridging the
metal and lithium centers are 2.031(2) and 2.033(2) Å.
The group 5 centers are bridged by a slightly distorted
square-planar Li+ atom coordination (79.95(7)° for
oxygen atoms bound to the same metal and 99.36(7)°
for oxygen atoms bound to adjacent metal centers;
Figure 2). The related structure of the pentakis(p-cres-
oxy)tantalum dimer,21 (CH3OC6H4O)4Ta(µ-OC6H4OCH3)2-
Ta(OC6H4OCH3)4 (I), reveals a similar, although more
distorted octahedral geometry around the Ta centers,
with bond angles for trans O-Ta-O geometries )
176.9(4)°, 163.8(4)°, and 159.2(4)° and angles for cis
O-Ta-O geometries ranging from 88.0(4)° to 105.2(4)°,
excluding the 68.2(4)° for the µ-oxygen atoms bridging
the Ta centers. The four nonbridging Ta-O distances
range from 1.836(10) to 1.925(9) Å, with the distances
for two oxygen atoms bridging the metal centers being
2.084(8) and 2.134(8) Å.
Resu lts a n d Discu ssion
Syn th esis of P en ta flu or op h en oxid e-Ba sed Co-
ca ta lysts. The reaction of LiAlH4 with HOC6F5 affords
Li+Al(OC6F5)4-,19and subsequent metathesis with Ph3-
CCl yields the corresponding trityl tetrakis(pentafluo-
rophenoxy)aluminate salt, Ph3C+Al(OC6F5)4 (4; eq 1).
-
Compound 4 is thermally stable at 25 °C in CD2Cl2
solution for days without noticeable decomposition and
was characterized using standard analytical techniques
(see Experimental Section for details).
LiAlH4 + 4 HOC6F5 toluene, 85 °C8
-H2
Ph3CCl
Li+Al(OC6F5)4
8Ph3C+Al(OC6F5)4 (1)
-
-LiCl
The group 5 pentachlorides MCl5 (M ) Nb, Ta) readily
undergo reaction with LiOC6F5 in Et2O at 25 °C to
afford crystalline Li(OEt2)n+{[M(OC6F5)4(µ2-OC6F5)2]2-
Li}‚C7H8 salts (Scheme 1; M ) Nb, n ) 4 (5a ); M ) Ta,
n ) 3 (5b)), which were characterized using standard
analytical methodology (see Experimental Section for
details).20 X-ray diffraction results (Figure 2) for 5b
Compounds 5 are cleanly converted by metathesis
with Ph3CCl in pentane to the corresponding mono-
nuclear, thermally stable Ph3C+M(OC6F5)6- salts (M )
(20) The synthesis of related fluoroalkoxide complexes Ph3C+-
[Nb(OCH(CF3)2)6]- and Li+[Nb(OCH(CF3)2)6]- has been reported:
Rockwell, J . J .; Kloster, G. M.; DuBay, W. J .; Grieco, P. A.; Shriver,
D. F.; Strauss, S. H. Inorg. Chim. Acta 1997, 263, 195-200.
(21) Lewis, L. N.; Garbauskas, M. F. Inorg. Chem. 1985, 24, 363-
366.
(19) The synthesis of related fluoralkoxide complex Li+[Al[OC(Ph)--
(CF3)2]4]- has been reported: Barbarich, T. J .; Handy, S. T.; Miller, S.
M.; Anderson, O. P.; Grieco, P. A.; Strauss, S. H. Organometallics 1996,
15, 3776-3778.

Perfluoroaryloxymetalate Anions
Organometallics, Vol. 21, No. 18, 2002 3697
Ta ble 1. Eth ylen e P olym er iza tion Activities a n d P olym er P r op er ties Usin g P en ta flu or op h en oxid e-Ba sed
Coca ta lystsa
c
µ mol
of cat.
rxn
time (s)
polymer
yield (g)
activity
g PE/atm.mol‚h
Tm
b
entry
precursor
cocatalyst
Mn
Mw/Mn
(°C)
1
2
3
4
5
6
7
8
(C5Me5)2ZrMe2
(C5Me5)2ZrMe2
(C5Me5)2ZrMe2
(C5Me5)2ZrMe2
(C5Me4H)2ZrMe2
(C5Me4H)2ZrMe2
(C5Me4H)2ZrMe2
(C5Me4H)2ZrMe2
Ph3C+Al(OC6F5)4- (4)
Ph3C+Nb(OC6F5)6- (6a )
Ph3C+Ta(OC6F5)6- (6b)
13.5
12.7
13.2
17.6
18.1
17.3
17.5
17.3
30
30
30
30
30
30
30
30
0.441
0.498
0.561
0.636
0.471
0.549
0.739
0.729
3.9 × 106
6.0 × 106
6.5 × 106
4.3 × 106
3.1 × 106
4.1 × 106
5.0 × 106
5.1 × 106
62 200
45 800
79 800
88 200
127 000
106 000
62 500
33 200
2.77
3.32
2.48
2.15
1.91
3.30
4.03
7.60
139.8
138.7
136.9
137.9
137.2
136.8
136.5
135.9
-
Ph3C+B(C6F5)4
Ph3C+Al(OC6F5)4- (4)
Ph3C+Nb(OC6F5)6- (6a )
Ph3C+Ta(OC6F5)6- (6b)
-
Ph3C+B(C6F5)4
a
Carried out at 1.0 atm of ethylene pressure in 100 mL of toluene on a high-vacuum line at 25 °C. See Experimental Section and ref
5k for polymerization procedures. GPC relative to polystyrene standards. c DSC trace from the second scan.
b
Ta ble 2. Su m m a r y of th e Cr ysta l Str u ctu r e Da ta
for P er flu or op h en oxid e Com p lexes 5
5a
5b
formula
C
98H48F60Li2Nb2O15
C
98H48F60Li2O15Ta2
fw
2805.06
2981.14
cryst color, habit
cryst dimens, mm
cryst syst
a, Å
b, Å
c, Å
yellow, needle
yellow, needle
triclinic
triclinic
14.5656(18)
15.0032(18)
15.4214(19)
61.447(2)
63.499(2)
88.445(2)
2573.8(5)
P1h (#2)
14.5435(11)
15.0132(11)
15.4426(11)
61.270(1)
63.729(1)
88.506(1)
2575.5(3)
P1h (#2)
R, deg
â, deg
γ, deg
volume, Å3
space group
Z
2
2
D(calc), g/cm3
µ, mm-1
2θ range, deg
intensities
(unique, Ri)
abs corr
1.810
0.396
1.59 to 28.41
16 513 (11 486,
0.0322)
1.922
2.296
1.59 to 28.33
16 573 (11 437,
0.0138)
SADABS
11 437/0/868
F igu r e 3. ORTEP plot (50% probabilities on thermal
ellipsoids) of trityl perfluorophenoxymetalate cocatalysts
6. M ) Nb (6a ).
SADABS
no. data/restraints/ 11 486/0/868
params
goodness-of-fit on
0.979
1.050
Nb, (6a ); M ) Ta (6b)) in high yield (Scheme 1). These
were characterized by standard techniques (see Experi-
mental Section for details). Diffraction analysis for 6a
(Figure 3;Table 6) reveals six-coordinate metal centers
with pronounced nonlinearity of the M-O-C6F5 link-
ages (Nb-O-C(aryl) ranges from 135.3(2)° to 170.6(2)°)
and dispersion in Nb-O distances ranging from
1.913(2) to 2.009(2) Å. Metrical parameters for 6b are
similar (Table 7).Work by Parkin22 and Rothwell23 has
shown that for early transition metal ions (Zr, Nb, Ta)
there is little correlation between the M-O-C(aryl)
bond angles and M-O bonding distances, and the
structures presented here also exhibit little correlation
between M-O bond distances and M-O-C(aryl) angles.
The quasi-octahedral environment is maintained with
trans O-Nb-O angles of 176.61(8)°, 173.62(8)°, and
170.56(8)° and cis O-Nb-O angles that range from
83.29(8)° to 94.59(8)°. A closely related structural
analogue of 6, the anion hexakis(3,5-dimethylphenoxy)-
F2
final R indices
[I>2σ]
R
Rw
0.0615
0.1597
1.451, -0.639
0.0259
0.0669
1.819, -1.004
2
largest diff peak,
hole, e-/Å3
O-Nb-O angles that range from 86.8(6)° to 92.5(6)°)
with similar Nb-O bonding distances of 1.95(1)-1.98-
(1) Å. In contrast to 6a , the Nb-O-C(aryl) angles of II
also exhibit a much narrower dispersion in magnitude
(142.6(1)-152.7(1)°).
-
niobium, Nb(OC8H9)6 (II),24 has a less distorted octa-
hedral geometry around the Nb center (trans O-Nb-O
angles of 178.5(6)°, 177.6(6)°, and 176.9(6)° and cis
Rea ctivity of Rep r esen ta tive Gr ou p 4 Meta llo-
cen es w ith Coca ta lysts 6. The reactivity and cocata-
lytic characteristics of the trityl hexakis(pentafluoro-
phenoxides) 6 were investigated with respect to a series
of metallocene dimethyls to determine their suitability
as activators in single-site olefin polymerization. At
room temperature, facile C6F5O- transfer from Nb/Ta
to Zr/Ti is observed for coordinatively more open group
4 complexes such as (C5H5)2ZrMe2, which reacts readily
(22) Howard, W. A.; Trnka, T. M.; Parkin, G. Inorg. Chem. 1995,
34, 5900-5909.
(23) (a) Steffey, B. D.; Fanwick, P. E.; Rothwell, I. P. Polyhedron
1990, 9, 963-968. (b) Coffindaffer, T. W.; Steffy, B. D.; Rothwell, I. P.;
Folting, K.; Huffman, J . C. Streib, W. E. J . Am. Chem. Soc. 1989, 111,
4742-4749.
(24) Coffindaffer, T. W.; Steffy, B. D.; Rothwell, I. P.; Folting, K.;
Huffman, J . C.; Streib, W. E. J . Am. Chem. Soc. 1989, 111, 4742-
4749.

3698 Organometallics, Vol. 21, No. 18, 2002
Metz et al.
Ta ble 3. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for
Ta ble 5. Su m m a r y of th e Cr ysta l Str u ctu r e Da ta
for P er flu or op h en oxid e Com p lexes 6
[Li(OEt2)4]+{[Nb(OC6F 5)4(µ2-OC6F 5)2]2Li}‚C7H8 (5a )a
6a
6b
Nb(1)-O(1)
Nb(1)-O(3)
Nb(1)-O(5)
Nb(1)-Li(1)
O(2)-C(7)
O(4)-C(19)
O(6)-C(31)
O(2)-Li(1)
2.029(3)
1.899(3)
1.897(3)
3.1123(5)
1.353(5)
1.334(5)
1.337(5)
2.045(3)
Nb(1)-O(2)
Nb(1)-O(4)
Nb(1)-O(6)
O(1)-C(1)
O(3)-C(13)
O(5)-C(25)
O(1)-Li(1)
2.029(3)
1.895(3)
1.935(3)
1.351(4)
1.332(5)
1.329(5)
2.030(2)
formula
fw
cryst color, habit
cryst dimens (mm)
cryst syst
a, Å
C
55H15O6F30Nb
C55H15O6F30Ta
1522.62
1434.58
orange, cut needle orange, needle
0.25 × 0.15 × 0.10 0.53 × 0.10 × 0.09
monoclinic
14.2798(6)
14.3771(6)
25.0458(11)
90.00
monoclinic
14.2781(10)
14.4033(10)
25.028(2)
90.00
96.9200(13)
90.00
5109.6(5)
P21/n (#14)
4
1.979
2.312
to 56.7
33 026 (12 545,
0.034)
b, Å
c, Å
R, deg
O(1)-Nb(1)-O(2)
80.03(10) O(1)-Nb(1)-O(3)
88.64(13)
88.37(12)
90.03(12)
88.07(12)
91.01(15)
89.67(12)
94.78(12)
â, deg
96.9330(1)
90.00
5104.4(3)
P21/n (#14)
4
1.867
0.400
to 56.6
O(1)-Nb(1)-O(4) 173.90(11) O(1)-Nb(1)-O(5)
γ, deg
O(1)-Nb(1)-O(6)
O(2)-Nb(1)-O(4)
91.31(11) O(2)-Nb(1)-O(3)
93.88(12) O(2)-Nb(1)-O(5)
volume, Å3
space group
Z
O(2)-Nb(1)-O(6) 171.34(11) O(3)-Nb(1)-O(4)
O(3)-Nb(1)-O(5) 176.70(13) O(3)-Nb(1)-O(6)
D(calc), g/cm3
µ, mm-1
2θ range, deg
O(4)-Nb(1)-O(5)
O(5)-Nb(1)-O(6)
91.81(14) O(4)-Nb(1)-O(6)
91.80(12) C(1)-O(1)-Nb(1) 135.4(2)
C(7)-O(2)-Nb(1) 129.3(2)
C(19)-O(4)-Nb(1) 161.0(3)
C(31)-O(6)-Nb(1) 149.6(3)
C(13)-O(3)-Nb(1) 165.3(3)
C(25)-O(5)-Nb(1) 172.5(3)
Nb(1)-O(1)-Li(1) 100.11(10)
intensities (unique, Ri) 38 570 (12 600,
0.030)
abs corr
face-centered,
SADABS
6862/0/829
face-centered,
SADABS
7452/0/829
Nb(1)-O(2)-Li(1)
O(1)-Li(1)-O(2)
99.61(10) O(1)-Li(1)-O(2)# 100.38(10)
79.62(10)
no. of data/restraints/
params
a
Symmetry transformations used to generate equivalent at-
goodness-of-fit on F2
final R indices [I>3σ]
R
1.17
1.11
oms: # -x+1, -y-1, -z-1.
Ta ble 4. Selected Bon d Len gth s (Å) a n d Bon d
An gles (d eg) for
0.030
0.048
0.77, -0.51
0.029
0.050
2.29, -1.60
2
Rw
[Li(OEt2)3]+{[Ta (OC6F 5)4(µ2-OC6F 5)2]2Li}‚C7H8 (5b)a
largest diff peak,
hole, e-/Å3
Ta(1)-O(1)
Ta(1)-O(3)
Ta(1)-O(5)
Ta(1)-Li(1)
O(2)-C(7)
O(4)-C(19)
O(6)-C(31)
O(2)-Li(1)
2.0331(17)
1.906(2)
1.9042(19)
3.1157(2)
1.350(3)
1.334(3)
1.335(3)
2.0557(17)
Ta(1)-O(2)
Ta(1)-O(4)
Ta(1)-O(6)
O(1)-C(1)
O(3)-C(13)
O(5)-C(25)
O(1)-Li(1)
2.0308(18)
1.900(2)
1.9292(18)
1.353(3)
1.332(4)
1.329(3)
Ta ble 6. Selected Bon d Len gth s (Å) a n d Bon d
-
An gles (d eg) for P h 3C+Nb(OC6F 5)6 (6a )
Nb(1)-O(1)
Nb(1)-O(3)
Nb(1)-O(5)
O(1)-C(1)
O(3)-C(13)
O(5)-C(25)
2.009(2)
1.929(2)
1.935(2)
1.322(3)
1.329(3)
1.328(3)
Nb(1)-O(2)
Nb(1)-O(4)
Nb(1)-O(6)
O(2)-C(7)
O(4)-C(19)
O(6)-C(31)
1.978(2)
1.968(2)
1.913(2)
1.324(3)
1.337(3)
1.327(3)
2.0203(17)
O(1)-Ta(1)-O(2)
O(1)-Ta(1)-O(4)
O(1)-Ta(1)-O(6)
O(2)-Ta(1)-O(4)
O(2)-Ta(1)-O(6)
O(3)-Ta(1)-O(5)
O(4)-Ta(1)-O(5)
O(5)-Ta(1)-O(6)
C(7)-O(2)-Ta(1)
79.95(7)
172.94(8)
91.67(8)
93.00(8)
171.62(7)
176.19(9)
O(1)-Ta(1)-O(3)
O(1)-Ta(1)-O(5)
O(2)-Ta(1)-O(3)
O(2)-Ta(1)-O(5)
O(3)-Ta(1)-O(4)
O(3)-Ta(1)-O(6)
88.52(9)
88.07(8)
89.61(9)
88.12(8)
91.22(11)
90.02(9)
95.38(9)
134.46(16)
O(1)-Nb(1)-O(2)
O(1)-Nb(1)-O(4)
O(1)-Nb(1)-O(6)
O(2)-Nb(1)-O(4)
O(2)-Nb(1)-O(6)
O(3)-Nb(1)-O(5)
O(4)-Nb(1)-O(5)
O(5)-Nb(1)-O(6)
Nb(1)-O(2)-C(7)
87.31(8) O(1)-Nb(1)-O(3)
176.61(8) O(1)-Nb(1)-O(5)
83.29(8) O(2)-Nb(1)-O(3)
94.59(8) O(2)-Nb(1)-O(5)
170.56(8) O(3)-Nb(1)-O(4)
173.62(8) O(3)-Nb(1)-O(6)
86.32(8) O(4)-Nb(1)-O(6)
92.62(8) Nb(1)-O(1)-C(1)
93.97(8)
90.94(8)
87.70(8)
88.46(8)
88.91(8)
92.00(8)
94.84(8)
135.3(2)
91.96(10) O(4)-Ta(1)-O(6)
91.78(8) C(1)-O(1)-Ta(1)
129.42(16) C(13)-O(3)-Ta(1) 163.7(2)
C(25)-O(5)-Ta(1) 171.97(19)
C(19)-O(4)-Ta(1) 159.8(2)
150.2(2)
Nb(1)-O(3)-C(13) 153.9(2)
Nb(1)-O(5)-C(25) 170.6(2)
C(31)-O(6)-Ta(1) 149.38(17) Ta(1)-O(1)-Li(1) 100.46(7)
Nb(1)-O(4)-C(19) 137.4(2)
Nb(1)-O(6)-C(31) 148.6(2)
Ta(1)-O(2)-Li(1)
O(1)-Li(1)-O(2)
99.36(7)
79.66(7)
O(1)-Li(1)-O(2)# 100.34(7)
a
Symmetry transformations used to generate equivalent at-
oms: # -x+1, -y-1, -z-1.
(OC6F5)Me or (C5Me5)2Zr(OC6F5)Me, respectively. These
latter assignments were confirmed by NMR spectral
comparison with authentic samples generated by in situ
C6F5OH titration with neutral dimethyl complexes. On
standing at -20 °C in an NMR tube, the red oily
material slowly converts to crystals of the metallo-
to form, as assessed by 1H/19F NMR spectral comparison
with authentic samples, (C5H5)2Zr(OC6F5)2, Ph3CCH3,
and presumably MeNb(OC6F5)4, as well as unidentified
minor byproducts. Authentic samples of perfluoroaryl-
oxide transfer products were synthesized by titration
of a dilute C6F5OH solution in toluene-d8 into a serum-
capped NMR tube containing a solution of metallocene
in toluene-d8 (see Experimental Section for details).
-
cenium ion pair (C5Me5)2ZrOC6F5+Nb(OC6F5)6 (7;
Scheme 2), which were isolated in small quantities and
characterized by X-ray diffraction.
The molecular structure of complex 7 (Figure 4; Table
9) features a (C5Me5)2ZrR+ fragment with normal bent
metallocene metrical parameters,5n Cp(cent)-Zr-Cp-
(cent) angle of 137.8(13)°, Cp(cent)-Zr distances of
2.205(4) and 2.213(4) Å, and an average C(Cp)-Zr
distance of 2.517(4) Å. The related structures (C5Me5)2-
ZrMe(THT)+B(C6H5)4- 25 (THT ) tetrahydrothiophene)
NMR-scale reaction of cocatalyst 6a with 1.0 equiv
of rac-Me2Si(Ind)2ZrMe2 proceeds in a similar fashion
with formation of rac-Me2Si(Ind)2Zr(OC6F5)Me. In con-
trast, the behavior toward sterically encumbered met-
allocenes, e.g., (C5Me4H)2ZrMe2 and (C5Me5)2ZrMe2, is
significantly different. Thus, reaction of 6a with 1.0
equiv of each of these metallocenes in toluene-d8 initially
results in red oily products, typical of more ionic (more
loosely ion-paired) species,6a as well as (C5Me4H)2Zr-
and (C5Me5)2ZrMe+MeB(C6F5)3
display Cp(cent)-
-
5o
Zr-Cp(cent) angles of 138.2(3)° and 136.6(5)° with
average C(Cp)-Zr distances of 2.54(1) and 2.537(7) Å,

Perfluoroaryloxymetalate Anions
Organometallics, Vol. 21, No. 18, 2002 3699
Sch em e 2. P r op osed Rea ctivity P a tter n of (C5Me5)2Zr Me2 w ith Coca ta lyst 6a
Ta ble 7. Selected Bon d Len gth s (Å) a n d Bon d
-
An gles (d eg) for P h 3C+Ta (OC6F 5)6 (6b)
Ta(1)-O(1)
Ta(1)-O(3)
Ta(1)-O(5)
O(1)-C(1)
O(3)-C(13)
O(5)-C(25)
2.000(3))
1.926(3))
1.931(3))
1.327(5)
1.344(5)
1.335(4)
Ta(1)-O(2)
Ta(1)-O(4)
Ta(1)-O(6)
O(2)-C(7)
O(4)-C(19)
O(6)-C(31)
1.980(3))
1.965(3))
1.912(3))
1.326(5)
1.326(5)
1.335(5)
O(1)-Ta(1)-O(2)
O(1)-Ta(1)-O(4)
O(1)-Ta(1)-O(6)
O(2)-Ta(1)-O(4)
O(2)-Ta(1)-O(6)
O(3)-Ta(1)-O(5)
O(4)-Ta(1)-O(5)
O(5)-Ta(1)-O(6)
Ta(1)-O(2)-C(7)
Ta(1)-O(4)-C(19)
Ta(1)-O(6)-C(31)
87.7(1)
176.8(1)
83.7(1)
O(1)-Ta(1)-O(3)
O(1)-Ta(1)-O(5)
O(2)-Ta(1)-O(3)
O(2)-Ta(1)-O(5)
O(3)-Ta(1)-O(4)
O(3)-Ta(1)-O(6)
O(4)-Ta(1)-O(6)
Ta(1)-O(1)-C(1)
Ta(1)-O(3)-C(13)
Ta(1)-O(5)-C(25)
93.4(1)
91.5(1)
88.6(1)
87.8(1)
89.2(1)
91.1(1)
94.3(1)
136.7(3)
153.5(3)
169.9(3)
94.4(1)
171.3(1)
173.8(1)
86.0(1)
93.2(1)
149.3(3)
138.2(3)
148.5(3)
F igu r e 4. Solid-state structure of [(C5Me5)2Zr(OC6F5)]+-
Nb(OC6F5)6 (7). Selected bond distances (Å) and angles
-
(deg): Zr1-Cent1 ) 2.205(4); Zr1-Cent2 ) 2.213(4); Zr1-
F8 ) 2.342(2); Zr1-O7 ) 1.984(2); C10-F8 ) 1.383(4);
C-F(av) ) 1.344(4); Nb-O(av) ) 1.946(3); Cent1-Zr1-
Cent2 ) 1.378(13); F8-Zr1-O7 ) 94.28(9); Zr1-O7-C37
) 168.0(3); Zr1-F8-C10 ) 167.7(2); O1-Nb1-O5 )
176.44(11); O2-Nb1-O6 ) 178.49(11); O3-Nb1-O4 )
174.76(11); smallest cis O-Nb1-O ) 86.84(11); largest cis
O-Nb1-O ) 93.12(11).
respectively. The Zr-O bond distance of 1.984(2) Å in
structure 7 is indistinguishable from Zr-O bond dis-
26
tances of 1.989(3) Å found in (C5Me5)Zr(OC6H5)2 and
1.991(2) Å found in (C5H5)2Zr(OC6F5)2.27
The geometry of the anionic Nb(OC6F5)6 fragment
-
in ion pair 7 is closer to octahedral than the analogous
anion structures found in 6a and 6b, with trans
O-Nb-O angles of 178.49(11)°, 176.44(11)°, and
174.76(11)° (vs 176.61(8)°, 173.62(8)°, and 170.56(8)° in
structure 6a ) and cis O-Nb-O angles ranging from
86.84(11)° to 93.12(11)° (vs 83.29(8)-94.59(8)° in struc-
ture 6a ). Average Nb-O bond distances are equivalent
for structures 6a and 7 (6a , 1.955(2) Å, 7, 1.946(3) Å),
and both structures have similar dispersions in the
Nb-O-C(aryl) angles (135.3(2)-170.6(2)° for 6a and
136.2(2)-168.5(3)° for 7).
(2.342(2) Å) and a correspondingly elongated F-C bond
distance (1.383(4) vs 1.345(4) Å (av)). Such bonding
patterns have been observed before in ion pairs com-
posed of metallocenium cations and perfluoroarylate
counteranions.6c,28 This structural result argues for the
intermediacy of (C5Me5)2ZrMe+Nb(OC6F5)6- in the reac-
tion of (C5Me5)2ZrMe2 and 6a , as does observation of
(C5Me5)2ZrMe(THF-d8)+Nb(OC6F5)6- (8) in in situ reac-
tion of activator 6a with (C5Me5)2ZrMe2 in THF-d8, and
the observed olefin polymerization activity of this reac-
tion product (vide infra). The instability of (C5Me5)2-
Additionally, the molecular structure of complex 7
contains a relatively short Zr+‚‚‚F-C(aryl) contact
(25) Eshuis, J . J . W.; Tan, Y. Y.; Meetsma, A.; Teuben, J . H.
Organometallics 1992, 11, 362-369.
(28) (a) Sun, Y.; Spence, R. E. v. H.; Piers, W. E.; Parvez, M.; Yap,
G. P. A. J . Am. Chem. Soc. 1997, 119, 5132-5143. (b) Ruwwe, J .; Erker,
G.; Froehlich, R. Angew. Chem., Int. Ed. Engl. 1996, 35, 80-82. (c)
Horton, A. D.; Orpen, A. G. Organometallics 1991, 10, 3910-3918. (d)
Pasynkiewicz, S. Polyhedron 1990, 9, 429-453.
(26) Howard, W. A.; Trnka, T. M.; Parkin, G. Inorg. Chem. 1995,
34, 5900-5909.
(27) Amor, J . I.; Burton, N. C.; Cuenca, T.; Gomez-Sal, P.; Royo, P.
J . Organomet. Chem. 1995, 485, 153-160.

3700 Organometallics, Vol. 21, No. 18, 2002
Metz et al.
Ta ble 8. Su m m a r y of th e Cr ysta l Str u ctu r e Da ta
for Com p lex 7
ditions, reaction of 4 and 6 with (C5Me5)2ZrMe2 and (C5-
Me4H)2ZrMe2 at 25 °C affords efficient ethylene polym-
erization catalysts (Table 1) with activities and product
polymer properties comparable to those of Ph3C+B-
(C6F5)4--activated systems under identical polymeriza-
tion conditions. One unusual feature of the present
catalysts is that high ethylene polymerization activity
is not paralleled by high propylene polymerization
activity. To our knowledge, this is the first report of such
a large anion-modulated metallocene reactivity pat-
tern.29 However, propylene incorporation in ethylene +
propylene copolymerizations is observed. The ability of
the present catalyst systems to differentiate between
CH2dCH2 and CH2dCHCH3 at the activation step may
be related to secondary interactions of the anion phe-
noxide ligands with the cationic metallocene centers.
P er flu or ob ip h en oxym et a la t e P olym er iza t ion
Ca ta lysts. Since the utility of the aforementioned
pentafluorophenoxy-based cocatalysts is to some degree
limited by phenoxide group transfer to less encumbered
cationic metallocenes, new synthetic approaches were
explored to improve catalyst stability. Substituting
pentafluorophenoxide substituents with nonafluorobi-
phenoxide substituents adds considerable steric bulk
about the cocatalyst core and more effectively screens
the oxygen atoms from the cationic metallocene elec-
trophile. Reaction of 2-bromononafluorobiphenyl with
1 equiv of n-butyllithium at -78 °C and subsequent
reaction with 0.33 equiv of boron trichloride generates
tris(2,2′,2′′-nonfluorobiphenyl)borane.5l After solvent re-
moval in vacuo, 50% hydrogen peroxide and KOH were
added at 0 °C. Stirring overnight, workup, and purifica-
tion by high-vacuum distillation at 120 °C leads to pure
nonafluorobiphenyl-2-ol (PBOH) in 51% yield (eq 2).
formula
C72.50H38O7F35ZrNb
fw
1870.16
cryst color, habit
cryst dimens (mm)
cryst syst
yellow, shard
0.3 × 0.3 × 0.2
triclinic
a, Å
b, Å
c, Å
12.6785(5)
16.2379(7)
17.6165(7)
95.4110(10)
105.0270(10)
90.4730(10)
3485.1(2)
R, deg
â, deg
γ, deg
volume, Å3
space group
Z
P1h(#2)
2
D(calc), g/cm3
µ, mm-1
1.782
0.464
to 56.6
22 696 (15 655, 0.021)
emprical and SADABS
10 332/0/1054
1.90
2θ range, deg
intensities (unique, Ri)
abs corr
no. of data/restraints/params
goodness-of-fit on F2
final R indices [I>2σ]
R
0.039
0.077
0.68, -0.66
2
Rw
largest diff peak, hole, e-/Å3
Ta ble 9. Selected Bon d Len gth s (Å) a n d Bon d
-
An gles (d eg) for [(C5Me5)2Zr (OC6F 5)]+Nb(OC6F 5)6
(7)
-
Nb(OC6F5)6
Nb(1)-O(1)
Nb(1)-O(3)
Nb(1)-O(5)
O(1)-C(1)
O(3)-C(13)
O(5)-C(25)
1.957(3)
1.972(3)
1.903(3)
1.324(4)
1.336(4)
1.324(4)
Nb(1)-O(2)
Nb(1)-O(4)
Nb(1)-O(6)
O(2)-C(7)
O(4)-C(19)
O(6)-C(31)
1.990(3)
1.935(3)
1.919(3)
1.327(4)
1.328(4)
1.327(4)
O(1)-Nb(1)-O(2)
O(1)-Nb(1)-O(4)
O(1)-Nb(1)-O(6)
O(2)-Nb(1)-O(4)
89.89(11) O(1)-Nb(1)-O(3)
87.70(11)
90.75(11) O(1)-Nb(1)-O(5) 176.44(11)
90.90(12) O(2)-Nb(1)-O(3)
88.16(11) O(2)-Nb(1)-O(5)
86.84(11)
87.45(11)
O(2)-Nb(1)-O(6) 178.49(11) O(3)-Nb(1)-O(4) 174.76(11)
O(3)-Nb(1)-O(5)
O(4)-Nb(1)-O(5)
O(5)-Nb(1)-O(6)
Nb(1)-O(2)-C(7) 136.2(2)
Nb(1)-O(4)-C(19) 153.9(3)
Nb(1)-O(6)-C(31) 168.5(3)
89.79(11) O(3)-Nb(1)-O(6)
91.53(11) O(4)-Nb(1)-O(6)
91.90(11)
93.12(11)
91.71(11) Nb(1)-O(1)-C(1) 155.3(3)
Nb(1)-O(3)-C(13) 140.4(2)
Nb(1)-O(5)-C(25) 156.5(2)
(C5Me5)2Zr(OC6F5)+
2.205(4)
Zr(1)-Cent(1)
Zr(1)-F(8)
C(10)-F(8)
O(7)-C(37)
Zr(1)-Cent(2)
2.213(4)
1.984(2)
1.344(4)
2.342(2)
1.383(4)
1.332(4)
Zr(1)-O(7)
C-F (av)
Cent(1)-Zr(1)-Cent(2) 137.8(13) F(8)-Zr(1)-O(7)
Zr(1)-O(7)-C(37)
94.28(9)
168.0(3) Zr(1)-F(8)-C(10) 167.7(2)
ZrMe+Nb(OC6F5)6- may reflect, among other factors, the
aforementioned deformability of the Nb-O-C6F5 link-
ages, which would facilitate Nb-O-C6F5 interaction
with, and subsequent C6F5O- transfer to, the electro-
philic zirconium center.
P er flu or op h en oxym et a la t e-Ba sed Sin gle-Sit e
P olym er iza tion Ca ta lysts. The above results imply
that phenoxide transfer from cocatalyst 6 is facile for
sterically more open metallocenium systems, explaining
why such preactivated catalysts are inactive toward
olefin polymerization. However, spectroscopic observa-
tion of ion pair 8 prompted studies of in situ (C5Me5)2-
ZrMe2 and (C5Me4H)2ZrMe2 activation in the presence
of olefin (as is commonly performed with relatively
unstable B(C6F5)4--based catalysts).6a Under such con-
Initial attempts to synthesize the hexakis(nonafluoro-
biphenoxy)tantalum anions were unsuccessful, likely
due to the severely crowded metal center that would be
formed. Instead lithium pentakis(nonafluorobiphenoxy)-
tantalum chloride was isolated and characterized by
X-ray diffraction.30
Next, a protonolytic route employing low coordination
number oxophilic lanthanide hydrocarbyls was inves-
tigated. Reaction of Ln(CH(SiMe3)2)3 (where Ln ) Y,11
La12) with 4.0 equiv of nonafluorobiphenyl-2-ol in pen-
(29) (a) J ia, L.; Yang, X.; Stern, C. L.; Marks, T. J . Organometallics
1997, 16, 842-857. (b) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem.
Soc. 1994, 116, 10015-10031.

Perfluoroaryloxymetalate Anions
Organometallics, Vol. 21, No. 18, 2002 3701
Ta ble 10. Eth ylen e P olym er iza tion Activities a n d P olym er P r op er ties Usin g Ln (P BO)3(P BOH)a Coca ta lysts
b
catalyst precursor
cocatalyst
µmol cat.
polym time (s)
polymer (g)
Mn
Mw/Mn
Tmc (°C)
activityd,e
CGCZrMe2
CGCTiMe2
Cp2ZrMe2
Me2Si(Ind)2ZrMe2
(C5Me5)2ZrMe2
CGCTiMe2
Y(PBO)3(PBOH)
Y(PBO)3(PBOH)
Y(PBO)3(PBOH)
Y(PBO)3(PBOH)
Y(PBO)3(PBOH)
La(PBO)3(PBOH)
La(PBO)3(PBOH)
16.5
17.1
16.3
14.8
14.6
15.5
12.7
1800
90
30
30
30
0.030
0.489
0.720
0.730
0.603
0.146
0.556
135
140
139
137
141
138
142
3.6 × 103
1.1 × 106
5.3 × 106
5.9 × 106
5.0 × 106
5.6 × 104
5.0 × 106
414 000
307 100
268 000
182 800
499 800
263 700
1.86
2.12
2.39
2.56
1.84
2.63
600
30
(C5Me5)2ZrMe2
a
b
Carried out at 1.0 atm of ethylene pressure in 100 mL of toluene on a high-vacuum line at 25 °C. GPC relative to polystyrene
standards. c DSC trace from second scan. Activity in units of g polymer/mol catalyst‚atm ethylene‚h. e Activity is the average of three
runs with approximately 10% reproducibility.
d
tane at room temperature results in the rapid and
quantitative formation of Ln(PBO)3(PBOH) complexes
(eq 3). These products were characterized by standard
analytical techniques (see Experimental Section for
details). The exact location of the proton has not been
determined, but it is presumably associated with an
oxygen atom.31 The 19F NMR data are consistent with
metallocene dimethyls in hydrocarbon solvents, cation-
anion pairs are formed immediately, as assessed by in
situ NMR spectroscopy, immediate gas evolution, and
immediate polymerization activity. In stark contrast to
the pentafluorophenoxide-based cocatalysts discussed
above, these cation-anion pairs are surprisingly stable
over significant periods of time. Ion pairs of 9a with
either (C5Me5)2ZrMe2 or Cp2ZrMe2 are extremely active
ethylene polymerization catalysts even after 4.0 h of
standing at room temperature. In fact, samples used in
unsuccessful crystallization experiments, which were
carried out at room temperature for periods of up to 3
days, followed by standing in a -15 °C freezer for a
week, still exhibited high activity for ethylene polym-
erization.
-
magnetically equivalent C12F9 groups in solution at
room temperature.
Further evidence for this increased ion pair stability
can be seen in NMR data from the reaction of 9a with
either Cp2ZrMe2 or (C5Me5)2ZrMe2. Previous decomposi-
tion of perfluoroaryloxide-based cocatalysts (6a , 6b)
involved abstraction of an aryloxide ring from the
cocatalyst by the cationic metallocenium electrophile.
In the case of 9a , the cationic metallocene interacts with
the corresponding neutral metallocene to form the
known µ-Me-bridged Cp2ZrMe(µ-Me)MeZrCp2+ and (C5-
+
Me5)2ZrMe(µ-Me)MeZr(C5Me5)2 dimers derived from
Cp2ZrMe2 and (C5Me5)2ZrMe2,6c,32,5l respectively. These
dimers were identified by the characteristic upfield shift
of the bridging Zr(µ-CH3)Zr groups, δ -1.30 for the Cp2-
Zr dimer and δ -2.43 for the (C5Me5)2Zr dimer, along
1
with assignment of the remaining H resonances. The
Rea ctivity of P er flu or obip h en oxid e Com p lexes
w ith Meta llocen e Dim eth yls. The reactivity of co-
catalysts 9a and 9b in the formation of single-site olefin
polymerization catalysts was explored using a series of
metallocene precatalysts. When 9a or 9b is mixed with
tendency for metallocene µ-Me dimer formation is
associated with counteranions having very weak coor-
dinative tendencies.6a
P olym er iza tion Ch a r a cter istics of P er flu or obi-
p h en oxid e-Ba sed Coca t a lyst s. When cocatalysts 9
are paired with a variety of metallocene precatalysts,
rather active ethylene polymerization catalysts are
formed (Table 10). Yttrium-based cocatalyst 9a forms
highly active (activity >106 g polymer/mol cat‚atm
monomer‚h) polymerization systems when combined
with a sterically varied array of organo-group 4 pre-
catalysts. From sterically open CGCTiMe2 to the steri-
cally encumbered (C5Me5)2ZrMe2, 9a forms highly active
polymerization systems, in contrast to cocatalysts 4 and
6, which are not compatible with sterically open met-
allocenes. In all likelihood, the severely encumbered
perfluorobiphenyl rings block access to the oxygen atoms
and stabilize what appear to be loosely bound ion pairs.
The ability of 9a and 9b to effect the rapid polymeri-
(30) Reaction of 6 equiv of lithium nonafluorobiphenoxide with
tantalum pentachloride in ether failed to form the desired hexakis-
(nonafluorobiphenoxy)tantalate anion. Rather, lithium pentakis(nona-
fluorobiphenoxy)tantalum chloride (Li+ClTa(PBO)5
) was formed.
-
Crystals suitable for single-crystal X-ray diffraction analysis were
grown and reveal a crowded tantalum center surrounded by bulky
perfluorobiphenoxy ligands. The crowded tantalum center is evidenced
by the well-defined octahedral geometry (trans O-Ta-O or O-Ta-
Cl angles of 177.4(2)°, 176.4(2)°, and 176.4(2)° with cis O-Ta-O or
O-Ta-Cl angles falling in the narrow range of 87.0(1)-92.6(2)°),
presumably to minimize interligand nonbonded contacts. In contrast,
the structure of 6b, Ph3C+Ta(OC6F5)6-, reveals a less sterically crowded
Ta center, evident in the distorted octahedral environment discussed
in the text (trans O-Ta-O angles of 176.8(1)°, 173.8(1)°, and
171.3(1)° with cis O-Ta-O ranging from 83.7(1)-94.4(1)°). Another
factor indexing the steric crowding around the Ta center are the Ta-
O-C(aryl) angles, which expand out to an average of 158.2(5)° for
Li+ClTa(PBO)5 versus 149.4(3)° for 6b.
-
(31) (C6F5)3B‚ROH complexes that have been used as cocatalysts,
see: (a) Beringhelli, T.; Maggioni, D.; D’Alfonso, G. Organometallics
2001, 20, 4927-2938, and references therein. (b) Siedle, A. R.;
Lamonna, W. M.; Newmark, R. A.; Stevens, J .; Richardson, D. E.; Ryan,
M. Makromol. Chem., Makromol. Symp. 1993, 66, 215-224.
(32) (a) Bochmann, M.; Lancaster, S. J . Angew. Chem., Int. Ed. Engl.
1994, 33, 1634-1637. (b) Beck, S.; Prosenc, M. H.; Brintzinger, H. H.;
Goretzki, R.; Herfert, N.; Fink, G. J . Mol. Catal. 1998, 111, 67-79.

3702 Organometallics, Vol. 21, No. 18, 2002
Metz et al.
zation of ethylene with open precatalysts such as
CGCTiMe2 and the extremely long lifetime of resultant
cation-anion pairs demonstrate high stability with
respect to perfluoroaryloxide ring transfer to the cationic
metal center. Note also that the molecular weights of
the 9-derived polyethylenes are significantly higher
than those from 4 and 6 (Table 1).
metalate cocatalyst system. Not only are catalyst life-
times longer, but even the most sterically open group 4
complexes, such as CGCTiMe2 and Cp2ZrMe2, serve as
precursors for active polymerization systems. Perfluo-
roaryloxide ring transfer is not completely inhibited by
the increased steric bulk of 9; however it is significantly
retarded. As evidenced by the formation of cationic
+
µ-methylmetallocene dimers, Cp2ZrMe(µ-Me)MeZrCp2
and (C5Me5)2ZrMe(µ-Me)MeZr(C5Me5)2+, the metalate
Con clu sion s
-
anions of 9 are weakly coordinating, much like B(C6F5)4
,
Highly efficient single-site cocatalysts containing
neither group 13 elements nor metal/metalloid-carbon
bonds have been synthesized and shown to form highly
active ethylene polymerization catalysts when paired
with sufficiently encumbered metallocenes. Although
the new class of perfluorophenoxymetalate cocatalysts
utilizing C6F5O- ligands is limited by facile perfluoro-
aryloxide ring transfer to cationic metallocenes with
nonbulky ligands, the lifetime of the resultant active
species is sufficient to demonstrate high polymerization
activity.
Lanthanide-based cocatalysts (9) employing the per-
fluorobiphenoxide ligand form stable, highly active
ethylene polymerization catalysts. Introduction of the
nonafluorobiphenoxide (2-C12F9O-) group has major
consequences for stabilization of the perfluoroaryloxy-
and with similar ethylene polymerization cocatalytic
characteristics.
Ack n ow led gm en t. This research was supported by
the U.S. Department of Energy (DE-FG 02-86 ER13511).
Y.S. thanks Dow Chemical Co. for a postdoctoral fel-
lowship. We thank Dr. P. N. Nickias of Dow Chemical
Co. for GPC analyses.
Su p p or tin g In for m a tion Ava ila ble: Complete X-ray
structural data, figures of polymerization apparatus, and a
temperature profile of a typical parallel polymerization reac-
tion. This material is available free of charge via the Internet
at http://pubs.acs.org.
OM020087S