Bis(pentafluorophenyl)(2-perfluorobiphenylyl)borane. A new perfluoroarylborane cocatalyst for single-site olefin polymerization

Article abstract of DOI:10.1021/om0002780

Bis(pentafluorophenyl)(2-perfluorobiphenylyl)borane, (C₆F₅)₂B(C₁₂F₉) (BPB), has been synthesized and characterized to serve as a new strong organo-Lewis acid cocatalyst for single-site olefin polymerization. BPB efficiently activates a variety of group 4 dimethyl complexes to form highly active homogeneous Ziegler-Natta olefin polymerization catalysts. Reaction of BPB with Cp₂ZrMe₂, rac-Me₂Si(Ind)₂ZrMe₂, and (CGC)MMe₂ (M = Zr, Ti; CGC = Me₂Si(η⁵- Me₄C₅)(^tBuN)) (1:1 molar ratio) rapidly and cleanly produces the base-free cationic complexes Cp₂ZrMe⁺[MeB(C₁₂F₉) (C₆F₅)₂]^- (1), rac-Me₂Si(Ind)₂ ZrMe⁺[MeB(C₁₂F₉)(C₆F₅)₂]^- (2), and (CGC)MMe⁺[MeB(C₁₂F₉) (C₆F₅)₂]^- (M = Zr; 3; M = Ti, 4), respectively. These complexes have been characterized by NMR and elemental analysis and are shown to be competent for ethylene and propylene polymerization. In general, BPB-derived catalysts exhibit polymerization activities comparable to or higher than those of the B(C₆F₅)₃-derived analogues, with the products exhibiting higher molecular weights but comparable polydispersities, polypropylene isotacticities, and, for ethylene + 1-hexene, comonomer incorporation.

Full text of DOI:10.1021/om0002780

3332
Organometallics 2000, 19, 3332-3337
Bis(P en ta flu or op h en yl)(2-p er flu or obip h en ylyl)bor a n e. A
New P er flu or oa r ylbor a n e Coca ta lyst for Sin gle-Site
Olefin P olym er iza tion
Liting Li, Charlotte L. Stern, and Tobin J . Marks*
Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113
Received March 31, 2000
Bis(pentafluorophenyl)(2-perfluorobiphenylyl)borane, (C6F5)2B(C12F9) (BPB), has been
synthesized and characterized to serve as a new strong organo-Lewis acid cocatalyst for
single-site olefin polymerization. BPB efficiently activates a variety of group 4 dimethyl
complexes to form highly active homogeneous Ziegler-Natta olefin polymerization catalysts.
Reaction of BPB with Cp2ZrMe2, rac-Me2Si(Ind)2ZrMe2, and (CGC)MMe2 (M ) Zr, Ti; CGC
) Me2Si(η5-Me4C5)(tBuN)) (1:1 molar ratio) rapidly and cleanly produces the base-free cationic
complexes Cp2ZrMe+[MeB(C12F9)(C6F5)2]- (1), rac-Me2Si(Ind)2ZrMe+[MeB(C12F9)(C6F5)2]- (2),
and (CGC)MMe+[MeB(C12F9)(C6F5)2]- (M ) Zr, 3; M ) Ti, 4), respectively. These complexes
have been characterized by NMR and elemental analysis and are shown to be competent
for ethylene and propylene polymerization. In general, BPB-derived catalysts exhibit
polymerization activities comparable to or higher than those of the B(C6F5)3-derived
analogues, with the products exhibiting higher molecular weights but comparable polydis-
persities, polypropylene isotacticities, and, for ethylene + 1-hexene, comonomer incorporation.
In tr od u ction
Homogeneous single-site metallocene olefin polymer-
ization catalysts have had a profound impact on con-
temporary polyolefin science and technology.1 These
catalysts exhibit extremely high intrinsic activities
based on transition-metal content, facile control over
polymer molecular weight and molecular weight distri-
bution, uniform comonomer incorporation, and precise
control of polymer stereoregularity. Cocatalysts are
generally used to activate the single-site catalysts by
forming ion pairs which are the active agents for olefin
polymerization. Organo-Lewis acid cocatalysts such as
perfluoroarylboranes are therefore of great current
interest for both technological and fundamental scien-
tific reasons.1a,2 They undergo reaction with metallocene
dimethyls in 1:1 catalyst to cocatalyst ratios to form
highly active, structurally characterizable catalytic spe-
cies. Recently, the sterically encumbered perfluoro-
arylborane tris(2,2′,2′′-perfluorobiphenylyl)borane (PBB;
I),2c was reported from our laboratory. PBB generates
cationic species with generally higher catalytic activities
for olefin polymerization and copolymerization than does
B(C6F5)3 (II). However, in the case of group 4 metal-
locene dimethyls, PBB preferentially affords cationic
dinuclear complexes such as [Cp2ZrMe(µ- Me)MeZrCp2]+
at room temperature (reflecting the weaker coordinative
tendencies of MePBB- versus MeB(C6F5)3-), even with
excess PBB and long reaction times.2c Monomeric spe-
cies can only be generated in situ at higher tempera-
tures. The activation of metallocene dimethyls with PBB
is also rather sluggish; for example, 1 h is required to
completely activate rac-Me2Si(Ind)2ZrMe2 in millimolar
toluene solution at 25 °C.2c For these reasons, it would
be of great interest to investigate the properties of
modified perfluoroarylboranes with mixed 2-perfluoro-
biphenylyl (C12F9) and perfluorophenyl (C6F5) substit-
uents which may be sterically and electronically inter-
mediate in properties between PBB and B(C6F5)3. We
report here the synthesis, molecular structure, reactiv-
(2) (a) Chen, E. Y.-X.; Marks, T. J . In ref 1a, pp 1371-1434. (b) Metz,
M. V.; Schwartz, D. J .; Stern, C. L.; Nickias, P. N.; Marks, T. J . Angew.
Chem., Int. Ed. 2000, 39, 1312-1316. (c) Luo, L.; Marks, T. J . In ref
1b, pp 97-106. (d) 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. (e) Chen, Y.-X.; Metz, M. V.; Li, L.; Stern, C. L.; Marks, T. J . J .
Am. Chem. Soc. 1998, 120, 6287-6305. (f) Li, L.; Marks, T. J .
Organometallics 1998, 17, 3996-4003. (g) Deck, P. A.; Beswick, C. L.;
Marks, T. J . J . Am. Chem. Soc. 1998, 120, 1772-1784. (h) Piers, W.
E.; Chivers, T. Chem. Soc. Rev. 1997, 26, 345-354. (i) Temme, B.;
Erker, G.; Karl, J .; Luftmann, H.; Fro¨hlich, R.; Kotila, S. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 1755-1757. (j) Yang, X.; Stern, C. L.; Marks,
T. J . J . Am. Chem. Soc. 1994, 116, 10015-10031. (k) Ewen, J . A.; Elder,
M. J . Chem. Abstr. 1991, 115, 136998g. (l) Yang, X.; Stern, C. L.; Marks,
T. J . J . Am. Chem. Soc. 1991, 113, 3623-3625.
(1) For recent reviews, see: (a) Gladysz, J . A., Ed. Chem. Rev. 2000,
100(4). (b) Marks, T. J ., Stevens, J . C. Eds. Topics in Catalysis
Baltzer: Basel, Switzerland, 1999; Vol. 15, and references therein. (c)
Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int. Ed.
1999, 38, 428-447. (d) Kaminsky, W.; Arndt, M. Adv. Polym. Sci. 1997,
127, 144-187. (e) Bochmann, M. J . Chem. Soc., Dalton Trans. 1996,
255-270. (f) Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt, R.; Rieger, B.;
Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995, 34, 1143-1170.
(g) Soga, K., Terano, M., Eds. Catalyst Design for Tailor-Made
Polyolefins; Elsevier: Tokyo, 1994. (h) Mo¨hring, P. C.; Coville, N. J . J .
Organomet. Chem. 1994, 479, 1-29. (i) Marks, T. J . Acc. Chem. Res.
1992, 25, 57-65.
10.1021/om0002780 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 07/27/2000

Bis(pentafluorophenyl)(2-perfluorobiphenylyl)borane
Organometallics, Vol. 19, No. 17, 2000 3333
2d
F igu r e 1. Comparison of the molecular structures of PBB2d and B(C6F5)3 computed with the AM1 model Hamiltonian
and BPB determined by X-ray diffraction in this study.
2-perfluorobiphenylyl bromide8 were prepared according to
ity, and polymerization catalytic characteristics of the
literature procedures.
new strong organo-Lewis acid bis(pentafluorophenyl)-
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), VXR 400 (FT 400 MHz, 1H; 100 MHz, 13C; 377 MHz, 19F),
and Gemini-300 (FT 300 MHz, 1H; 75 MHz, 13C; 282 MHz, 19F)
instruments. Chemical shifts for 1H and 13C spectra were
referenced using 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 Oneida Research
Services, Inc., Whitesboro, NY, or by Midwest Microlab,
Indianapolis, IN. 13C NMR assays of polypropylene micro-
structure were conducted in C2D2Cl4 at 120 °C. Signals were
assigned according to the literature for polypropylene9 and
ethylene/1-hexene copolymers,10 respectively. Melting temper-
atures of polymers were measured by DSC (DSC 2920, TA
Instruments, Inc.) from the second scan with a heating rate
of 10 °C/min.
(2-perfluorobiphenylyl)borane (BPB, III) and demon-
strate that it is an excellent cocatalyst for metallocene-
mediated ethylene polymerization. The differences in
molecular architectures of PBB, B(C6F5)3, and BPB can
be appreciated from the computed geometries of PBB
and B(C6F5)32d and the molecular structure of BPB from
X-ray diffraction shown in Figure 1 and discussed
herein.
Exp er im en ta l Section
Ma ter ia ls a n d Meth od s. All manipulations of air-sensitive
materials were performed with rigorous exclusion of oxygen
and moisture in flamed Schlenk-type glassware on a dual-
manifold Schlenk line or interfaced to a high-vacuum line (10-5
Torr) or in a nitrogen-filled Vacuum Atmospheres glovebox
with a high-capacity recirculator (<1 ppm of O2). Argon,
ethylene, and propylene (Matheson, polymerization grade)
were purified by passage through a supported MnO oxygen-
removal column and an activated Davison 4A molecular sieve
column. Ether solvents were purified by distillation from Na/K
alloy/benzophenone ketyl. Hydrocarbon solvents were distilled
under nitrogen from Na/K alloy. All solvents for high-vacuum-
line manipulations were stored in vacuo over Na/K alloy in
Teflon-valved bulbs. Deuterated solvents were obtained from
Cambridge Isotope Laboratories (all g99 atom %D), were
freeze-pump-thaw degassed and dried over Na/K alloy, and
were stored in resealable flasks. Other nonhalogenated sol-
vents were dried over Na/K alloy, and halogenated solvents
were distilled from P2O5 and stored over activated Davison
4A molecular sieves. The comonomer 1-hexene (Aldrich) was
dried over Na/K and vacuum-transferred into a storage tube
containing activated 4A molecular sieves. The reagents Me3-
SnCl, Me2SnCl2, BCl3 (1.0 M in hexane), and n-BuLi (1.6 M
in hexanes) were purchased from Aldrich and used as received.
B(C6F5)3,3 Me2Si(Me4C5)(t-BuN)TiMe2 ((CGC)TiMe2),4 (CGC)-
ZrMe2,4 rac-Me2Si(Ind)2ZrMe2,5 Cp2ZrMe2,6 (C6F5)2BCl,7 and
Syn th esis of Bis(p en ta flu or op h en yl)(2-p er flu or obi-
p h en ylyl)bor a n e, (C6F 5)2B(C12F 9) (BP B; III). In a 100 mL
flask, 2-perfluorobiphenylyl bromide (3.16 g, 8.0 mmol) was
dissolved in 20 mL of dry pentane. In another 250 mL flask,
30 mL of pentane and 5.1 mL of n-butyllithium (1.6 M in
hexanes, 9.0 mmol) was added and the solution was cooled to
-50 °C. The solution of 2-perfluorobiphenyl bromide was then
added dropwise via syringe. A white precipitate formed im-
mediately. The solution was stirred between -40 and -30 °C
for 90 min after the addition was complete, and then 20 mL
of (C6F5)2BCl (3.16 g, 8.0 mmol in pentane) was added at -50
°C. The solution was warmed slowly to room temperature
overnight. After filtration and removal of all volatiles, a sticky
(5) (a) Herrmann, W. A.; Rohrmann, J .; Herdtweck, E.; Spaleck, W.;
Winter, A. Angew. Chem., Int. Ed. Engl. 1989, 28, 1511-1512. (b)
Herfert, N.; Fink, G. Makromol. Chem. Rapid Commun. 1993, 14, 91-
96. (c) Christopher, J . N.; Diamond, G. M.; J ordan, R. F.; Petersen, J .
L. Organometallics 1996, 15, 4038-4044.
(6) Samuel, E.; Rausch, M. D. J . Am. Chem. Soc. 1973, 95, 6263.
(7) Chambers, R. D.; Chivers, T. J . Chem. Soc. 1965, 3933.
(8) Penton, D. E.; Park, A. J .; Shaw, D.; Massey, A. G. J . Organomet.
Chem. 1964, 2, 437.
(3) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2, 245-
250.
(9) (a) Pellecchia, C.; Pappalardo, D.; D’Arco, M.; Zambelli, A.
Macromolecules 1996, 29, 1158. (b) Miyatake, T.; Miaunuma, K.;
Kakugo, M. Macromol. Symp. 1993, 66, 203. (c) Kakugo, M.: Miyatake,
T.; Miaunuma, K. Stud. Surf. Sci. Catal. 1990, 56, 517. (d) Longo, P.;
Grassi, A. Makromol. Chem. 1990, 191, 2387. (e) Randall, J . C. J .
Polym. Sci., Part B: Polym. Phys. 1975, 13, 889.
(10) (a) Soga, K.; Uozumi, T.; Park, J . R. Makromol. Chem. 1990,
191, 2853. (b) Hsich, E. T.; Randall, J . C. Macromolecules 1982, 15,
1402.
(4) (a) Fu, P.-F.; Luo, L.; Lanza, D. L.; Wilson, D. J .; Rudolph, P.
R.; Fragala`, I. L.; Stern, C. L.; Marks, T. J . Submitted for publication.
(b) Canich, J . M.; Hlatky, G. G.; Turner, H. W. PCT Appl. WO 92-
00333, 1992; Canich, J . M. Eur. Patent Appl. EP 420 436-A1, 1991
(Exxon Chemical Co.). (c) Stevens, J . C.; Timmers, F. J .; Wilson, D.
R.; Schmidt, G. F.; Nickias, P. N.; Rosen, R. K.; Knight, G. W.; Lai, S.
Eur. Patent Appl. EP 416 815-A2, 1991 (Dow Chemical Co.).

3334 Organometallics, Vol. 19, No. 17, 2000
Li et al.
Ta ble 1. Cr ysta llogr a p h ic Deta ils for
(C6F 5)2B(C12F 9) (BP B, III)
oil remained. It was washed with cold pentane (-78 °C) three
times to afford a colorless solid product. Yield: 2.0 g (37%).
The complex can be further purified by sublimation at 110 °C
(0.05 Torr) for 3 h. Spectroscopic and analytical data for BPB
(III) are as follows. 19F NMR (benzene-d6, 282.33 MHz, 23
°C): δ -127.48 (d, 3J F-F ) 21.5 Hz, 4 F, o-F), -128.28 (m, 1 F,
formula
BC24F19
660.04
fw
cryst dimens
cryst color, habit
cryst syst
a, Å
0.4 × 0.2 × 0.1 mm
colorless, columnar
orthorhombic
9.663(6)
3
3-F), -135.10 (m, 1 F, 6-F), -139.89 (d, J F-F ) 21.5 Hz, 2 F,
3
2′, 6′-F), -140.90 (tt, J F-F ) 20.8 Hz, 2 F, p-F), -144.94 (td,
b, Å
19.673(2)
11.826(5)
2248(1)
5
3
3J F-F ) 21.0 Hz, J F-F ) 7.6 Hz, 1 F, 5-F), -150.07 (t, J F-F
)
c, Å
3
5
21.2 Hz, 1 F, 4′-F), -151.48 (td, J F-F ) 22.2 Hz, J F-F ) 6.8
Hz, 1 F, 4-F), -160.25 (m, 4 F, m-F), -160.98 (m, 2 F, 3′, 5′-
F). Anal. Calcd for C24BF19: C, 43.67; H, 0.00; N, 0.00. Found:
C, 43.65, H, 0.10, N, 0.00.
V, Å3
space group
Z value
Pna21 (No. 33)
4
1.950
D
calcd, g/cm3
Syn th esis of Cp 2Zr Me+[MeB(C12F 9)(C6F 5)2]- (1). Cp2-
ZrMe2 (50 mg, 0.21 mmol) and (C6F5)2B(C12F9) (146 mg, 0.22
mmol) were loaded into a 25 mL reaction flask in the glovebox.
On the high-vacuum line, C6H6 (15 mL) was condensed in at
-78 °C. The solution was then stirred at room temperature
for 1 h, and all the volatiles were removed under high vacuum
to give a yellow solid. Pentane was condensed in to wash the
solid twice, and the yellow solid was dried under vacuum (10-5
Torr) for 4 h at room temperature. Yield: 110 mg (61%). The
diffractometer
temp, °C
transmissn factors, range
radiation
Enraf-Nonius CAD4
-120
0.8323-1.000
Mo KR (λ ) 0.710 69 Å)
ω-θ
2-48.9
2161, 0.021
1149
0.064
0.047
scan type
2θ range, deg
intensities (unique, Ri)
intensities > 3.00 σ(I)
R
Rw, for w ) 1/σ2(Fo)
1
spectroscopic data for 1 are as follows. H NMR (benzene-d6,
(s, 3 H, SiCH3). 13C NMR (benzene-d6, 74.42 MHz, 23 °C): δ
57.74 (ZrCH3), 44.27 (CMe3), 33.05 (CMe3), 15.04 (CH3), 12.74
(CH3), 11.37 (CH3), 10.37 (CH3), 5.54 (SiCH3), 5.12 (SiCH3).
The B-CH3 resonance was too broad to be detected with
certainty 19F NMR (benzene-d6, 282.33 MHz, 23 °C): δ -129.31
(s, 1 F, 3-F), -131.67 (br, 4 F, o-F), -136.49 (s, 1 F, 6-F),
299.91 MHz, 23 °C): δ 5.47 (s, 10 H, C5H5), 0.32 (s, 3 H,
ZrCH3), 0.24 (br, 3 H, BCH3). 13C NMR (benzene-d6, 74.42
MHz, 23 °C): δ 114.04 (C5H5), 40.92 (ZrCH3), 26.79 (br, BCH3).
19F NMR (benzene-d6, 282.33 MHz, 23 °C): δ -128.75 (s, 1 F,
3-F), -132 (very broad, 4 F, o-F), -136.80 (s, 1 F, 6-F), -138.94
(s, 2 F, 2′,6′-F), -153.48 (t, 3J F-F ) 21.1 Hz, 1 F, 4′-F), -156.46
3
3
(t, J F-F ) 22.2 Hz, 1 F, 4-F), -158.41 (multi, 3 F, p-F, 5-F),
-138.38 (s, 2 F, 2′,6′-F), -153.48 (t, J F-F ) 21.3 Hz, 1 F, 4′-
F), -156.02 (t, 3J F-F ) 21.5 Hz, 1 F, 4-F), -158.42 (s, 3 F, p-F,
5-F), -162.99 (s, 2 F, 3′,5′-F), -163.89 (br, 4 F, m-F). Anal.
Calcd for C41H33BF19NSiZr: C, 47.77; H, 3.22. Found: C, 47.10,
H, 3.01.
-162.91 (s, 2 F, 3′,5′-F), -164.00 (br, 4 F, m-F). Anal. Calcd
for C36H16BF19Zr: C, 47.44; H, 1.76. Found: C, 47.09, H, 1.67.
Syn th esis of r a c-Me2Si(In d)2Zr Me+[MeB(C12F9)(C6F5)2]-
(2). rac-Me2Si(Ind)2ZrMe2 (50 mg, 0.13 mmol) and (C6F5)2B-
(C12F9) (87 mg, 0.13 mmol) were loaded into a 25 mL reaction
flask in the glovebox. On the high-vacuum line, C6H6 (10 mL)
was condensed in at -78 °C. The solution was then stirred at
room temperature for 1 h, and all the volatiles were removed
under high vacuum to give a yellow solid. Pentane was
condensed in to wash the solid twice, and the resulting yellow
solid was dried under vacuum (10-5 Torr) for 4 h at room
temperature. Yield: 82 mg (60%). The spectroscopic data for
Syn th esis of CGCTiMe+[MeB(C12F 9)(C6F 5)2]- (4). (CGC)-
TiMe2 (70 mg, 0.21 mmol) and (C6F5)2B(C12F9) (141 mg, 0.21
mmol) were loaded into a 25 mL reaction flask in the glovebox.
On the high-vacuum line, C6H6 (15 mL) was condensed in at
-78 °C. The solution was then stirred at room temperature
for 1 h, and all the volatiles were removed under high vacuum
to give a yellow solid. Pentane was condensed in to wash the
solid twice, and the yellow solid was dried under vacuum (10-5
Torr) for 4 h at room temperature. Yield: 101 mg (48%). The
1
2 are as follows. H NMR (C6D6, 23 °C, 399.941 MHz): δ 7.63
3
3
1
(d, J H-H ) 8.5 Hz, 1 H, Ind), 7.26 (d, J H-H ) 8.5 Hz, 1 H,
spectroscopic data for 4 are as follows. H NMR (benzene-d6,
3
3
Ind), 7.06 (t, J H-H ) 7.4 Hz, 1 H, Ind), 6.99 (d, J H-H ) 8.4
299.91 MHz, 23 °C): δ 1.71 (s, 3 H, CH3), 1.54 (s, 3 H, CH3),
1.53 (s, 3 H, CH3), 1.41 (s, 3 H, CH3), 0.99 (s, 9 H, CMe3), 0.95
(s, 3 H, TiCH3), 0.66 (br, 3 H, BCH3), 0.29 (s, 3 H, SiCH3),
0.16 (s, 3 H, SiCH3). 19F NMR (benzene-d6, 282.33 MHz, 23
°C): δ -126.96 (s, 1 F, 3-F), -131.04 (br, 4 F, o-F), -136.85
3
Hz, 1 H, Ind), 6.62-6.72 (m, 2 H, Ind), 6.58 (d, J H-H ) 3.0
3
Hz, 1 H, Ind), 6.54 (d, J H-H ) 7.8 Hz, 1 H, Ind), 6.26 (d, 1 H,
3J H-H ) 8.1 Hz, Ind), 6.21 (d, 1 H, J H-H ) 3.0 Hz, Ind), 5.65
3
3
3
(d, 1 H, J H-H ) 3.3 Hz, Ind), 4.95 (d, 1 H, J H-H ) 3.3 Hz,
Ind), 0.36 (s, 3 H, Me2Si), 0.21 (s, 3 H, Me2Si), -0.32 (s, br, 3
H, B-CH3), -0.55 (s, 3 H, Zr-CH3). 19F NMR (benzene-d6,
282.33 MHz, 23 °C): δ -127.53 (s, 1 F, 3-F), -131 (very broad,
4 F, o-F), -137.15 (m, 1 F, 6-F), -137.94 (m, 2 F, 2′,6′-F),
-153.74 (t, J F-F ) 21 Hz, 1 F, 4′-F), -156.65 (t, J F-F ) 22
Hz, 1 F, 4-F), -158.56 (m, 2 F, p-F), -159.26 (t, J F-F ) 21
3
(m, 1 F, 6-F), -138.10 (s, 2 F, 2′,6′-F), -153.60 (t, J F-F ) 21
Hz, 1 F, 4′-F), -156.26 (t, 3J F-F ) 22 Hz, 1 F, 4-F), -158.44 to
3
-158.75 (m, 2 F, p-F), -158.84 (t, J F-F ) 22 Hz, 1 F, 5-F),
-162.90 (s, 1 F, 3′-/5′-F), -163.34 (s, 1 F, 3′-/5′-F), -164.12
(br, 4 F, m-F). Anal. Calcd for C41H33BF19NSiTi: C, 49.87; H,
3.37. Found: C, 49.89, H, 3.43.
3
3
3
Hz, 1 F, 5-F), -162.75 (br, 1 F, 3′-/5′-F), -163.33 (br, 1 F, 3′/
5′-F), -164.16 (br, 4 F, m-F). Anal. Calcd for C46H24BF19Zr:
C, 53.14; H, 2.33. Found: C, 52.82, H, 2.37.
X-r a y Cr ysta llogr a p h ic Stu d y of (C6F 5)2B(C12F 9) (BP B;
III). Crystals for diffraction analysis were grown by slow
cooling of a pentane solution. A colorless, translucent, colum-
nar crystal of III having the approximate dimensions 0.4 ×
0.2 × 0.1 mm was mounted using oil (Paratone-N, Exxon) on
a glass fiber. The crystal was poorly shaped and had been
detached from the side of the glass container. All measure-
ments were made on an Enraf-Nonius CAD4 diffractometer
with graphite-monochromated Mo KR radiation. The crystal,
data collection, and refinement parameters are collected in
Table 1. Corrections for Lorentz and polarization effects and
anomalous dispersion effects11 were applied to the data, as was
an empirical absorption correction (DIFABS).12
Syn t h esis of (CGC)Zr Me+[MeB(C12F 9)(C6F 5)2]- (3).
(CGC)ZrMe2 (80 mg, 0.22 mmol) and (C6F5)2B(C12F9) (142 mg,
0.22 mmol) were loaded into a 25 mL reaction flask in the
glovebox. On the high-vacuum line, C6H6 (15 mL) was con-
densed in at -78 °C. The solution was then stirred at room
temperature for 1 h, and all the volatiles were removed under
high vacuum to give a yellow solid. Pentane was condensed
in to wash the solid twice, and the yellow solid was dried under
vacuum (10-5 Torr) for 4 h at room temperature. Yield: 119
mg (53%). The spectroscopic data for 3 are as follows. 1H NMR
(benzene-d6, 299.91 MHz, 23 °C): δ 1.73 (s, 3 H, CH3), 1.68 (s,
3 H, CH3), 1.59 (s, 3 H, CH3), 1.46 (s, 3 H, CH3), 1.00 (s, 12 H,
CMe3 + BCH3), 0.31(s, 3 H, ZrCH3), 0.24 (s, 3 H, SiCH3), 0.17
The structure was solved by direct methods (SHELXS-86)13
and expanded using Fourier techniques.14 Owning to the
paucity of data, the non-hydrogen atoms were refined isotro-

Bis(pentafluorophenyl)(2-perfluorobiphenylyl)borane
Organometallics, Vol. 19, No. 17, 2000 3335
F igu r e 2. Two views of the molecular structure and atom-numbering scheme for (C6F5)2B(C12F9) (BPB; III).
pically. The enantiomer was refined, giving the same un-
weighted and weighted agreement factors. Bijvoet reflections
were then compared, and this enantiomer was favored slightly.
Maximum and minimum peaks on the final difference Fourier
map corresponded to 0.45 and -0.53 e-/Å3.
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. Standard devia-
tions in activities reported in Table 3 are the average of three
trials.
All calculations were performed using the teXsan crystal-
lographic software package of Molecular Structure Corp.
E t h ylen e a n d P r op ylen e P olym er iza t ion E xp er i-
m en ts. On a high-vacuum line (10-5 Torr), ethylene and
propylene polymerizations were carried out in 250 mL round-
Resu lts a n d Discu ssion
A. Syn th esis of BP B, [(C6F 5)2B(C12F 9)]. The start-
ing materials, (C6F5)2BCl7 and 2-perfluorobiphenyl bro-
mide,8 were synthesized using the literature procedure.
Low-temperature lithium-halogen exchange using
nBuLi and 2-perfluorobiphenyl bromide produced (2-
perfluorobiphenylyl)lithium, which was then subjected
to reaction with (C6F5)2BCl at low temperature to afford
bis(pentafluorophenyl)(2-perfluorobiphenylyl)borane
((C6F5)2B(C12F9); BPB, III) (eqs 1 and 2). The product
bottom three-neck Morton flasks equipped with
a large
magnetic stirring bar and a thermocouple probe. In a typical
experiment, a measured quantity of dry toluene (and 1-hexene
in the case of ethylene and 1-hexene copolymerization) was
vacuum-transferred into the flask, presaturated under 1.0 atm
of rigorously purified ethylene or propylene (pressure control
using a mercury bubbler), and equilibrated at the desired
reaction temperature using an external bath. The catalytically
active species was freshly generated (within 1.0 min) using a
solution having a 1:1 metallocene to cocatalyst ratio in 1.5 mL
of toluene. The solution of catalyst was then quickly injected
into the rapidly stirred flask using a gastight syringe equipped
with a spraying needle. The temperature of the toluene
solution in representative polymerization experiments was
monitored using a thermocouple (OMEGA Type K thermo-
couple with a Model HH21 microprocessor thermometer). The
reaction exotherm temperature rise was invariably less than
5 °C during these polymerizations. After a measured polym-
erization time interval (short to minimize mass transport and
exotherm effects), the polymerization was quenched by the
addition of 15 mL of 2% acidified methanol. Another 30 mL of
(11) (a) International Tables for X-ray Crystallography; Ibers, J . A.,
Hamilton, W. C., Eds.; Kynoch Press: Birmingham, U.K., 1974; Vol.
IV. (b) Creagh, D. C., McAuley, W. J . International Tables for
Crystallography; Wilson, A. J . C., Ed.; Kluwer Academic: Boston, 1992;
Vol. C, Tables 4.2.6.8 (pp 219-222) and 4.2.4.3 (pp 200-206).
(12) Walker, N.; Stuart, D. Acta Crystallogr. 1983, A39, 158-166.
(13) Sheldrick, G. M. SHELXS-86. In Crystallographic Computing;
Sheldrick, G. M., Kruger, C., Goddard, R., Eds.; Oxford University
Press: Oxford, U.K., 1985; pp 175-189.
(14) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
de Gelder, R.; Israel, R.; Smits, J . M. M. M. DIRDIF 94: The DIRDIF-
94 Program System; Technical Report of the Crystallography Labora-
tory; University of Nijmegen, Nijmegen, The Netherlands, 1994.
was purified by washing with pentane at low temper-
ature and vacuum sublimation. BPB is an air-sensitive
colorless solid which is thermally stable at room tem-
perature. It was characterized by standard spectroscopic
and analytical techniques (see Experimental Section for
details). Crystals of BPB were grown from pentane
solution for X-ray diffraction studies. Figure 2 shows

3336 Organometallics, Vol. 19, No. 17, 2000
Li et al.
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for BP B
Bond Distances
B-C19
B-C13
C1-C6
C7-C8
C14-C15
1.54(2)
1.57(2)
1.40(2)
1.41(2)
1.36(2)
B-C1
1.57(2)
1.40(1)
1.47(2)
1.40(1)
1.35(2)
C1-C2
C6-C7
C13-C14
C6-C5
Bond Angles
C1-B-C19
C13-B-C19
B-C1-C2
120(1)
122(1)
119(1)
123(1)
C1-B-C13
116(1)
123(1)
121(1)
124(1)
B-C1-C6
C1-C6-C7
B-C19-C20
B-C13-C14
two views of the solid-state structure of BPB. Selected
bond distances and angles are given in Table 2. The sum
of bond angles around the boron atom is 358°, indicating
that atoms C1, C19, C13, and B are essentially coplanar.
The molecular structure suggests that there is probably
a weak π-π interaction between two phenyl rings as
shown in Figure 2b. The closest nonbonded intramo-
lecular contact between these two rings is 3.13(2) Å for
C7-C13. On the basis of calculated least-squares planes,
the dihedral angle between the two phenyl rings is
29.32°. The smaller C13-B-C1 angle (116°) and some-
what larger C19-B-C13 angle (122°) also support the
possibility of the weak π stacking interaction. The B-C
bond distances in BPB are similar to those recently
reported for the o-phenylene-bridged diborane 1,2-C6F4-
[B(C6F5)2]2 (IV).2b
C. Olefin P olym er iza tion Ca ta lysis. Olefin polym-
erization experiments were carried out with rigorous
exclusion of air and moisture. The results (Table 3) show
that cationic species generated with BPB are highly
active catalysts. Compared to tris(2-perfluoronaphthyl)-
borane (B(C10F7)3; PNB)2d and PBB,2c BPB-derived
B. Meta llocen iu m Ca tion s Gen er a ted fr om BP B.
Metallocene cations are rapidly (unlike PBB, I) gener-
ated by reaction of BPB with metallocene dimethyls in
aromatic hydrocarbon solvents (eq 3). The reaction of
catalysts exhibit approximately the same polymeriza-
tion catalytic characteristics as the PNB-derived ana-
logues2d but exhibit polymerization activities compa-
rable to or lower than those of PBB-derived analogues.2c
Cationic complex 1 is approximately as active as the
B(C6F5)3 analogue for ethylene polymerization (entries
1 and 2). The polyethylenes produced have similar
molecular weights and polydispersities. In the case of
“constrained geometry” catalysts (CGC), complex 4 is
approximately 3× more active than the B(C6F5)3 ana-
logue for ethylene polymerization and yields high-
molecular-weight polyethylenes with narrower polydis-
persities. Catalyst 4 is also much more active toward
ethylene and 1-hexene copolymerization than the
B(C6F5)3 analogue and produces a copolymer with
comparable levels of comonomer incorporation. In the
isospecific polymerization of propylene, catalyst 1 ex-
hibits slightly higher activity than the B(C6F5)3-derived
analogue (entries 5-8). Compared to the polymers
produced by the analogous B(C6F5)3-derived catalyst at
various temperatures, the polymer produced by cocata-
lyst III has higher molecular weight but a similar
isotacticity index.
BPB with dimethylmetallocenes in benzene cleanly
forms monomeric cationic species (using a 1:1 reactant
ratio) having the generalized formula L2ZrMe+MeBPB-.
These cation-anion complexes were isolated and puri-
fied by washing with pentane and were characterized
1
by NMR spectroscopy and elemental analysis. The H
and 13C NMR spectra of the cationic portions of these
complexes are very similar to those of the B(C6F5)3-
derived complexes,2h with downfield shifted Zr-CH3
resonances and broad, upfield-shifted CH3-B reso-
nances being particularly distinctive. The diastereotopic
ring and MeSi resonances in 2-4 indicate that catalyst-
cocatalyst ion pairing is relatively “tight” and that
symmetrization processes (eqs 4 and 5)2a,c,e,h are slow
on the NMR time scale at room temperature.

Bis(pentafluorophenyl)(2-perfluorobiphenylyl)borane
Organometallics, Vol. 19, No. 17, 2000 3337
Ta ble 3. Olefin P olym er iza tion Da ta for Meta llocen es Activa ted by (C6F 5)2B(C12F 9) (BP B; III)a
amt of
cat.,
e
mono- temp,
polym
activityd
Mw
Mw/
entry
cat.
merb
°C
µmol conditionsc yield, g
× 105
× 103 Mn
remarks
1
2
3
4
5
Cp2ZrMe+MeBPB- (1)
E
E
E
E
P
23
25
23
25
24
15
15
15
15
10
100, 1.0
100, 1.0
100, 10
100, 10
50, 2.0
0.85(15) 34(6)
149
124
1.88
2.03
5.90
9.54
-
Cp2ZrMe+MeB(C6F5)3
1.00g
40g
(CGC)TiMe+MeBPB- (4)
0.60(8)
2.4(3) 1170
-
(CGC)TiMe+MeB(C6F5)3
0.21g
0.84g
20(2)
1058
41
rac-Me2Si(Ind)2ZrMe+MeBPB- (2)
0.67(7)
2.03 Tm ) 146 °C,
% mmmm ) 93
2.40 Tm ) 146 °C,
% mmmm ) 93
3.7 1.51 Tm ) 125 °C,
% mmmm ) 86
2.7 1.39 Tm ) 122 °C,
% mmmm ) 86
-
6
7
8
rac-Me2Si(Ind)2ZrMe+MeB(C6F5)3
P
P
P
24
60
60
10
10
10
50, 2.5
50, 1.5
0.73g
18g
33
rac-Me2Si(Ind)2ZrMe+MeBPB- (2)
0.68(10) 27(4)
22g
rac-Me2Si(Ind)2ZrMe+MeB(C6F5)3
(CGC)TiMe+MeBPB- (4)
50, 1.75 0.63g
-
f
9
10
E/H
E/H
25
25
15
25
25, 10
25, 10
1.57(15)
0.05g
6.3(6)
0.12g
71
2.01 65% H
(CGC)TiMe+MeB(C6F5)3
63.2% Hf
-
a
All polymerizations carried out on a high-vacuum line (10-5 Torr); uncertainties in yields and activities are the average of three runs.
Standard deviations are given in parentheses. Ethylene (E) and propylene (P) 1 atm pressure; 44.0 mmol of 1-hexene (H). c Conditions
b
d
given as milliliters of toluene, time in minutes. In units of (g of polymer)/[(mol of cationic metallocene) atm h]; quantities in parentheses
are estimated standard deviations. e GPC relative to polystyrene standards. f 1-Hexene incorporation in E/H copolymer. Data from ref
g
2c (reproducibility between runs 10-15%).
Con clu sion s
polydispersities, polypropylene isotacticities, and, for
ethylene + 1-hexene, comonomer incorporation.
The new organo-Lewis acid bis(pentafluorophenyl)-
(2-perfluorobiphenylylyl)borane ((C6F5)2B(C12F9); BPB)
has been synthesized and characterized. It is a potent
cocatalyst which activates a variety of dimethyl group
4 complexes efficiently and rapidly to form highly active
cationic olefin polymerization catalysts. BPB-derived
catalysts are very similar to PNB-derived catalysts in
polymerization characteristics and exhibit polymeriza-
tion activities comparable to or higher than those of
B(C6F5)3-derived analogues, with the products exhibit-
ing higher molecular weights but having comparable
Ack n ow led gm en t. The research was supported by
the U.S. Department of Energy (Grant DE-FG02-86 ER
13511). We thank Dr. Peter N. Nickias of Dow Chemical
Co. for GPC analyses.
Su p p or tin g In for m a tion Ava ila ble: Tables of final
positional parameters and isotropic displacement parameters
for all atoms and bond lengths and angles in molecule III. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM0002780