A novel phenolate constrained geometry catalyst system. Efficient synthesis, structural characterization, and α-olefin polymerization catalysis

Article abstract of DOI:10.1021/om9707376

This paper reports the convenient one-pot synthesis of a bifunctional ^-Me₄Cp^? phenolate^- ligand and the efficient one-step synthesis of the corresponding Ti^IV and Zr^IV complexes. The reaction of 2-bromo-4-methylphenol with 2 equiv of ⁿBuLi followed by addition of 2,3,4,5-tetramethyl-2-cyclopentenone produces the bifunctional mono-Cp phenol ligand precursor 2-(tetramethylcyclopentadienyl)-4-methylphenol ((TCP)H₂, 1). Reaction of 1 with Ti(CH₂-Ph)₄ at 60°C in toluene cleanly generates (TCP)Ti(CH₂Ph)₂ (2), while the corresponding reaction with Zr(CH₂Ph)₄ at higher temperatures affords the chelated C₂-symmetric zirconocene (TCP)₂Zr (3). In solution at room temperature, the two benzyl groups of 2 are magnetically equivalent, however, in the solid state, X-ray diffraction reveals that one benzyl group is coordinated in a normal η¹-fashion and the other in an η²-mode. The small Cp-(centroid)-Ti-O angle of 107.7(2)° in 2 indicates sterically open features in common with amido-based constrained geometry polymerization catalysts. Low-temperature NMR-scale reactions of 2 with B(C₆F₅)₃ and Ph₃C⁺B(C₆F₅)₄^- indicate the formation of the corresponding cationic complexes (TCP)TiCH₂Ph⁺ PhCH₂B(C₆F₅)₃^- (4) and (TCP)TiCH₂Ph⁺B(C₆F₅) ₄^- (5). Upon activation with Ph₃C⁺B(C₆F₅)₄ ^-, complex 2 is highly active for ethylene, propylene, and styrene polymerization.

Full text of DOI:10.1021/om9707376

5958
Organometallics 1997, 16, 5958-5963
A Novel P h en ola te “Con str a in ed Geom etr y” Ca ta lyst
System . Efficien t Syn th esis, Str u ctu r a l
Ch a r a cter iza tion , a n d r-Olefin P olym er iza tion Ca ta lysis
You-Xian Chen, Peng-Fei Fu, Charlotte L. Stern, and Tobin J . Marks*
Department of Chemistry, Northwestern University, Evanston, Illinois 60208-3113
Received August 18, 1997X
This paper reports the convenient “one-pot” synthesis of a bifunctional -Me4Cpkphenolate-
ligand and the efficient “one-step” synthesis of the corresponding TiIV and ZrIV complexes.
The reaction of 2-bromo-4-methylphenol with 2 equiv of nBuLi followed by addition of 2,3,4,5-
tetramethyl-2-cyclopentenone produces the bifunctional mono-Cp phenol ligand precursor
2-(tetramethylcyclopentadienyl)-4-methylphenol ((TCP)H2, 1). Reaction of 1 with Ti(CH2-
Ph)4 at 60 °C in toluene cleanly generates (TCP)Ti(CH2Ph)2 (2), while the corresponding
reaction with Zr(CH2Ph)4 at higher temperatures affords the chelated C2-symmetric
zirconocene (TCP)2Zr (3). In solution at room temperature, the two benzyl groups of 2 are
magnetically equivalent, however, in the solid state, X-ray diffraction reveals that one benzyl
group is coordinated in a normal η1-fashion and the other in an η2-mode. The small Cp-
(centroid)-Ti-O angle of 107.7(2)° in 2 indicates sterically open features in common with
amido-based “constrained geometry” polymerization catalysts. Low-temperature NMR-scale
reactions of 2 with B(C6F5)3 and Ph3C+B(C6F5)4- indicate the formation of the corresponding
cationic complexes (TCP)TiCH2Ph+ PhCH2B(C6F5)3 (4) and (TCP)TiCH2Ph+B(C6F5)4 (5).
-
-
Upon activation with Ph3C+B(C6F5)4 , complex 2 is highly active for ethylene, propylene,
-
and styrene polymerization.
In tr od u ction
Ligand modifications have played a key role in
developing new “single-site” group 4 metallocene cata-
lyst precursors for optimizing polymerization activity
as well as polymer properties such as stereoregularity,
molecular weight, thermal/rheological characteristics,
bulky and polar comonomer incorporation, and micro-
structure.1 In particular, complexes of bifunctional
monocyclopentadienyl ligands having an appended het-
eroatom donor have attracted considerable attention,2
as exemplified by “constrained geometry” catalysts
having the formula Me2Si(η5-Me4C5)(tBuN)MX2 (CGC-
MX2; M ) Ti, Zr, Hf; X ) Cl, Me, CH2Ph).3 These
catalysts have a convalently attached amide donor
ligand which stablizes the electrophilic metal center
electronically, while the short Me2Si< bridging group
considerably opens the metal coordination sphere vis-
a`-vis a conventional metallocene. The result upon
activation with a variety of cocatalysts is a new genera-
tion of catalysts which, among other features, efficiently
produce ultra-low-density elastomeric ethylene-octene
copolymers.3c
Given the impact of the Cp-appended heteroatom
donor groups on the catalytic performance of such
complexes, ligand design remains a very active and
challenging area of olefin polymerization research, and
much attention has been focused on the design of new
N-2,4 and O-containing ligands.2,5 In addition, develop-
ing more efficient syntheses of useful ligands as well
as of the corresponding metal complexes has attracted
X Abstract published in Advance ACS Abstracts, December 1, 1997.
(1) For recent reviews, see: (a) Kaminsky, W.; Arndt, M. Adv. Polym.
Sci. 1997, 127, 144-187. (b) Bochmann, M. J . Chem. Soc., Dalton
Trans. 1996, 255-270. (c) Brintzinger, H.-H.; Fischer, D.; Mu¨lhaupt,
R.; Rieger, B.; Waymouth, R. M. Angew. Chem., Int. Ed. Engl. 1995,
34, 1143-1170. (d) Catalyst Design for Tailor-Made Polyolefins; Soga,
K., Terano, M., Eds.; Elsevier: Tokyo, 1994. (e) Mo¨hring, P. C.; Coville,
N. J . J . Organomet. Chem. 1994, 479, 1-29. (f) Marks, T. J . Acc. Chem.
Res. 1992, 25, 57-65. (g) J ordan, R. F. Adv. Organomet. Chem. 1991,
32, 325-387.
(2) For reviews, see: (a) J utzi, P.; Siemeling, U. J . Organomet.
Chem. 1995, 500, 175. (b) Okuda, J . Comm. Inorg. Chem. 1994, 16,
185-205.
(4) For recent examples, see: (a) Amor, F.; Okuda, J . J . Organomet.
Chem. 1996, 520, 245-248. (b) Okuda, J .; Schattenmann, F. J .;
Wocadlo, S.; Massa, W. Organometallics 1995, 14, 789-795. (c) J utzi,
P.; Kleimeier, J . J . Organomet. Chem. 1995, 486, 287. (d) Flores, J .;
Chien, J . C. W.; Rausch, M. D. Organometallics 1994, 13, 4140. (e)
Herrmann, W. A.; Morawietz, M. J . A. J . Organomet. Chem. 1994, 482,
169. (f) Hughes, A. K.; Meetsma, A.; Teuben, J . H. Organometallics
1993, 12, 1936. (g) Piers, W. E.; Shapiro, P. J .; Bunnel, E. E.; Bercaw,
J . E. Synlett 1990, 2, 74. (h) Shapiro, P. J .; Bunel, E. E.; Schaefer, W.
P.; Bercaw, J . E. Organometallics 1990, 9, 867.
(5) For recent examples, see: (a) van der Zeijden, A. A. H.; Matteis,
C. Organometallics 1997, 16, 2651. (b) Trouve, G.; Laske, D. A.;
Meetsma, A.; Teuben, J . H. J . Organomet. Chem. 1996, 511, 255. (c)
Christoffers, J .; Bergman, R. G. Angew. Chem., Int. Ed. Engl. 1995,
34, 2266. (d) Huan, Q.; Qian, Y.; Li, G.; Tang, Y. Transition Met. Chem.
1990, 15, 483.
(3) (a) Chen, Y.-X.; Marks, T. J . Organometallics 1997, 16, 3649-
3657. (b) Fu, P.-F.; DiBella, S.; Wilson, D. J .; Rudolph, P. R.; Fragala,
I. L.; Stern, C. L.; Marks, T. J . Submitted for publication. (c) Stevens,
J . C. In Studies in Surface Science and Catalysis; Hightower, J . W.,
Delglass, W. N., Iglesia, E., Bell, A. T., Eds.; Elsevier: Amsterdam,
1996; Vol. 101, pp 11-20 and references therein. (d) Shapiro, P. J .;
Cotter, W. D.; Schaefer, W. P.; Labinger, J . A.; Bercaw, J . E. J . Am.
Chem. Soc. 1994, 116, 4623 (e) 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.). (f) 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.).
S0276-7333(97)00737-1 CCC: $14.00 © 1997 American Chemical Society

A Novel Phenolate Catalyst System
Organometallics, Vol. 16, No. 26, 1997 5959
- 10a
Ph3C+B(C6F5)4
were prepared and purified according to
both scientific and technological interest.3a,6 In view of
the importance of the aforementioned issues, we report
here a convenient “one-pot” synthesis of a new bifunc-
tional mono-Cp ligand containing an appended pheno-
late group (ligand 1; (TCP)H2) as well as efficient one-
step syntheses of the corresponding Cs-symmetric Ti and
chiral C2-symmetric Zr complexes.7 Attractive features
literature procedures.
P h ysica l a n d An a lytica l Mea su r em en ts. NMR spectra
were recorded on either Varian VXR 300 (FT 300 MHz, 1H;
75 MHz, 13C) or Germini-300 (FT 300 MHz, H; 75 MHz, 13C;
1
282 MHz, 19F) instruments. Chemical shifts for 1H and 13C
NMR 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 Oneida Research Services, Inc., Whitesboro, NY. 13C NMR
assays of polymer microstructure were conducted in C2D2Cl4
at 120 °C. Melting temperatures of polymers were measured
by DSC (DSC 2920, TA Instruments, Inc.) from the second scan
with a heating rate of 20 °C/min. GPC analyses of polymer
samples were performed at L. J . Broutman & Associates Ltd.,
Chicago, on a Waters 150C GPC relative to polystyrene
standards.
of the new ligand system include a simple synthetic
procedure as well as great intrinsic steric and electronic
flexibility introducible via modification of the aryl
fragment. We also report the solution and solid state
structure, cocatalyst abstraction/activation chemistry,
and the performance in olefin polymerization of the Ti
dibenzyl complex.
On e-P ot Syn t h esis of 2-(Tet r a m et h ylcyclop en t a d i-
en yl)-4-m eth ylp h en ol, (TCP )H2 (1). Into a 1 L Schlenk
flask were charged 50.0 g (267 mmol) of 2-bromo-4-methylphe-
nol and 250 mL of THF, and then 350 mL of nBuLi (560 mmol,
1.6 M in hexanes) was added dropwise with stirring at 0 °C.
A white precipitate formed, and the resulting mixture was
allowed to warm to room temperature and stirred for another
2 h. The solution was next cooled to -78 °C, and 2,3,4,5-
tetramethyl-2-cyclopentenone (40.2 mL, 36.9 g, 267 mmol) was
added dropwise over 30 min. The resulting solution was then
allowed to warm to room temperature and stirred overnight.
The reaction mixture was next treated with 20 mL of water
followed by 120 mL of concentrated HCl. The organic layer
was separated and treated 3 times with 40 mL of concentrated
HCl. Volatiles were removed by rotary evaporation, and the
oily residue was distilled under vacuum at 150 °C/15 Torr to
yield 28.5 g of the title ligand as a dark brown crystalline solid.
Yield: 46.8%. 1H NMR (C6D6, 23 °C): δ 6.88 (s, 1 H, Ar), 6.78
(m, 2 H, Ar), 3.00 (s, 1 H, OH), 2.50 (q, J H-H ) 6.6 Hz, 1 H,
Cp-H), 2.18 (s, 3 H, Ar-CH3), 1.63 (s, 3 H, Cp-CH3), 1.48 (s,
3 H, Cp-CH3), 1.28 (s, 3 H, Cp-CH3), 1.00 (d, J H-H ) 7.2 Hz,
3 H, Cp-CH3). 13C NMR (C6D6, 23 °C): δ 157.11, 138.57, 132,-
63, 129.18, 129.00, 125.40 (Ar), 109.88, 101.36, 58.37, 51.40
(Cp), 24.86 (Ar-CH3), 21.00, 20.45, 12.27, 9.63 (Cp-CH3).
Anal. Calcd for C16H20O: C, 84.16; H, 8.83. Found: C, 84.37;
H, 8.94.
Exp er im en ta l Section
Ma ter ia ls a n d Meth od s. All manipulations of air-sensi-
tive 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
(10-6 Torr) or in
glovebox with
a
nitrogen-filled Vacuum Atmospheres
a
high-capacity recirculator (<1 ppm O2).
Argon, hydrogen (Matheson, prepurified), ethylene, and pro-
pylene (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/ben-
zophenone ketyl. Hydrocarbon solvents (toluene and pentane)
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), freeze-pump-thaw degassed, dried over Na/K alloy, and
stored in resealable flasks. Other non-halogenated solvents
were dried over Na/K alloy, and halogenated solvents were
distilled from P2O5 and stored over activated Davison 4A
molecular sieves. C6F5Br (Aldrich) was vacuum distilled from
P2O5. Styrene (Aldrich) was dried over CaH2 and vacuum-
transferred into a storage tube containing activated 4A mo-
lecular sieves. TiCl4, ZrCl4, PhCH2MgCl (1.0 M in diethyl
ether), nBuLi (1.6 M in hexanes), 2-bromo-4-methylphenol,
and 2,3,4,5-tetramethyl-2-cyclopentenone were purchased
from Aldrich. Ti(CH2Ph)4,8 Zr(CH2Ph)4,8 B(C6F5)3,9 and
On e-Step Syn th esis of (TCP )Ti(CH2P h )2 (2). Ti(CH2-
Ph)4 (1.01 g, 2.40 mmol), (TCP)H2 (0.46 g, 2.0 mmol), and 50
mL of toluene were heated with stirring at 60-65 °C for 30 h
in the absence of light. The solvent was removed in vacuo,
and the black residue was extracted with 50 mL of pentane.
The pentane extracts were then filtered, and the solvent was
removed from the filtrate under vacuum. The resulting crude
product was washed with 5 mL of cold pentane and dried to
produce 0.46 g of the pure product as a brown solid. Yield:
50.4%. The product is very soluble in pentane. 1H NMR (C6D6,
23 °C): δ 7.13 (d, J H-H ) 7.5 Hz, 4 H, Ph), 7.04 (d, J H-H ) 7.5
Hz, 4 H, Ph), 6.89 (d, J H-H ) 8.1 Hz, 2 H, Ar), 6.83 (t, J H-H
)
(6) (a) Tsuie, B.; Swenson, D. C.; J ordan, R. F.; Petersen, J . L.
Organometallics 1997, 16, 1392-1400. (b) Mu, Y.; Piers, W. E.;
MacQuarrie, D. C.; Zaworotko, M. J .; Young, V. G., J r. Organometallics
1996, 15, 2720-2726. (c) Diamond, G. M.; J ordan; R. F.; Petersen, J .
L. J . Am. Chem. Soc. 1996, 118, 8024-8033. (d) Diamond, G. M.;
J ordan; R. F.; Petersen, J . L. Organometallics 1996, 15, 4030-4037;
Ibid. 4038-4044; Ibid. 4045-4053. (e) Carpenetti, D. W.; Kloppenburg,
L.; Kupec, J . T.; Petersen, J . L. Organometallics 1996, 15, 1572-1581.
(f) Gauthier, W. J .; Corrigan, J . F.; Taylor, N. J .; Collins, S. Macro-
molecules 1995, 28, 377. (g) van der Linden, A.; Schaverien, C. J .;
Meijboom, N.; Ganter, C.; Orpen, A. G. J . Am. Chem. Soc. 1995, 117,
3008-3021. (h) Herrmann, W. A.; Morawietz, M. J . A.; Priermeier, T.
Angew. Chem., Int. Ed. Engl. 1994, 33, 1946. (i) Nickias, P. N.; Devore,
D. D.; Wilson, D. R. PCT Appl. WO 08199, 1993.
7.5 Hz, 2 H, Ph), 6.59 (d, J H-H ) 7.5 Hz, 1 H, Ar), 2.50 (d,
J H-H ) 10.2 Hz, 2 H, CH2Ph), 2.32 (d, J H-H ) 10.2 Hz, 2 H,
CH2Ph), 2.11 (s, 3 H, Ar-CH3), 1.90 (s, 6 H, C5Me4), 1.44 (s, 6
H, C5Me4). 13C NMR (C6D6, 23 °C): δ 170.71, 147.87, 136.73,
130.50, 130.00, 129.76, 128.70 (Ar, Ph), 123.07, 121.18, 114.00
(Cp), 83.85 (t, J C-H ) 127.5 Hz, CH2Ph), 20.73 (Ar-CH3), 11.49
(C5Me4), 11.25 (C5Me4). Anal. Calcd for C30H32OTi: C, 78.93;
H, 7.09. Found: C, 78.67; H, 6.83.
(9) Massey, A. G.; Park, A. J . J . Organomet. Chem. 1964, 2, 245-
250.
(7) Communicated in part previously, see: Chen, Y.-X.; Fu, P.-F.;
Stern, C. L.; Marks, T. J . Abstracts of Papers, 213th National Meeting
of the American Society, San Francisco, CA, April 13-17, 1997;
American Chemical Society: Washington, DC, 1997; INOR 676.
(8) Zucchini, U.; Albizzati, E.; Giannini, U. J . Organomet. Chem.
1971, 26, 357-372.
(10) (a) Chien, J . C. W.; Tsai, W.-M.; Rausch, M. D. J . Am. Chem.
Soc. 1991, 113, 8570-8571. (b) Yang, X.; Stern, C. L.; Marks, T. J .
Organometallics 1991, 10, 840-842. (c) Ewen, J . A.; Elder, M. J . Eur.
Pat. Appl. 426637, 1991; Chem. Abstr. 1991, 115, 136987c, 136988d.
(d) Hlatky, G. G.; Upton, D. J .; Turner, H. W. U.S.Pat. Appl. 459921,
1990; Chem. Abstr. 1991, 115, 256897v.

5960 Organometallics, Vol. 16, No. 26, 1997
Chen et al.
Ta ble 1. Su m m a r y of th e Cr ysta l Str u ctu r e Da ta
for (TCP )Ti(CH2P h )2 (2)
On e-Step Syn th esis of (TCP )2Zr (3). Zr(CH2Ph)4 (2.10
g, 4.60 mmol), (TCP)H2 (0.840 g, 3.68 mmol), and 50 mL of
toluene were heated with stirring at 110 °C for 12 h in the
absence of light. Using the same work-up procedure as in the
synthesis of (TCP)Ti(CH2Ph)2 above, 0.35 g of the title complex
formula
fw
C30H32TiO
456.48
cryst color, habit
cryst dimens mm
cryst syst
a, Å
orange, platey
0.24 × 0.15 × 0.01
triclinic
1
was isolated as a colorless crystalline solid. Yield: 35.0%. H
NMR (C6D6, 23 °C): δ 7.07 (d, J H-H ) 2.1 Hz, 2 H, Ar), 7.01
8.324(3)
(dd, J H-H ) 7.8 Hz, J H-H ) 2.1 Hz, 2 H, Ar), 6.73 (d, J H-H
)
b, Å
10.432(4)
8.4 Hz, 2 H, Ar), 2.25 (s, 6 H, Ar-CH3), 2.08 (s, 6 H, C5Me4),
1.78 (s, 6 H, C5Me4), 1.72 (s, 12 H, C5Me4). 13C NMR (C6D6,
23 °C): δ 173.89, 138.84, 129.91, 129.24, 129.18, 126.47 (Ar),
120.14, 118.42, 117.09, 115.83 (Cp), 20.83 (Ar-CH3), 11.07,
10.56, 10.00, 9.52 (C5Me4). Anal. Calcd for C32H36O2Zr: C,
70.67; H, 6.67. Found: C, 70.49; H, 6.73.
c, Å
14.634(4)
R, deg
85.67(3)
79.23(3)
76.64(4)
1213.9(8)
â, deg
γ, deg
V, Å3
space group
Z
P1h (No. 2)
-
In Situ Gen er a tion of (TCP )TiCH2P h +P h CH2B(C6F 5)3
2
d(calcd), g/cm3
µ, cm-1
1.249
3.72
(4). (TCP)Ti(CH2Ph)2 (4.6 mg, 0.010 mmol) and B(C6F5)3 (5.1
mg, 0.010 mmol) were loaded in the glovebox into a J . Young
NMR tube, which was then attached to the high-vacuum line.
CD2Cl2 (0.7-1 mL) was then vacuum-transferred into this tube
at -78 °C. The NMR spectroscopy was carried out at -40 °C.
1H NMR (CD2Cl2, -40 °C): δ 7.81 (t, J H-H ) 7.5 Hz, 1 H), 7.65
(t, J H-H ) 7.5 Hz, 1 H), 7.41 (t, J H-H ) 7.5 Hz, 1 H), 7.35 (t,
J H-H ) 7.5 Hz, 1 H), 7.23 (d, J H-H ) 7.5 Hz, 1 H), 7.07 (t, J H-H
) 7.5 Hz, 2 H), 6.85 (t, J H-H ) 7.5 Hz, 2 H), 6.79 (t, J H-H ) 7.5
Hz, 1 H), 6.64 (d, J H-H ) 6.9 Hz, 2 H), 6.10 (d, J H-H ) 6.9 Hz,
diffractometer
radiation
Enraf-Nonius, CAD4
Mo KR (λ ) 0.710 69 Å),
graphite monochromated
-120 °C
temperature, °C
scan type
2θ range, deg
ω-θ
2.0-45.9
intensities (unique, Ri)
transmission factor range
secondary extinction
intensities > 3σ(I)
no. of params
3634 (3358, 0.114)
0.9543-0.9970
coefficient: 6.29514e-08
1335
1 H), 3.84 (d, J H-H ) 6.3 Hz, 1 H, Ti-CH2Ph), 2.96 (d, J H-H
)
220
6.3 Hz, 1 H, Ti-CH2Ph), 2.71 (s, br, 2 H, B-CH2Ph), 2.44 (s,
3 H, Ar-CH3), 2.33 (s, 3 H, C5Me4), 2.13 (s, 3 H, C5Me4), 2.04
(s, 3 H, C5Me4), 1.57 (s, 3 H, C5Me4). A small amount of
dibenzyl (δ 2.84 ppm) was also detected in the NMR reaction.
19F NMR (CD2Cl2, -40 °C): δ -130.00 (s, br, 6 F, o-F), -162.30
R
0.066
Rw
0.054
0.37
max density in ∆F map, e-/Å3
cooling of a saturated pentane solution to -20 °C over several
days. The solvent was decanted in the glovebox, and the
crystals were quickly covered with a layer of Paratone-N oil
(Exxon, dried and degassed at 120 °C/10-6 Torr for 24 h). The
crystals were then mounted on thin glass fibers and trans-
ferred into the cold-steam (-120 °C) of the Enraf-Nonius CAD4
diffractometer. Final cell dimensions were obtained by a least-
squares fit to the automatically centered settings for 25
reflections. Intensity data were all corrected for absorption,
anomalous dispersion, and Lorentz and polarization effects.
The space group was determined by statistical analysis of
intensity distribution and sucessful refinement of the proposed
structure. Crystallographic data are summarized in Table 1.
The structure was solved by direct methods11 and expanded
using Fourier techniques.12 Owing to the paucity of data,
atoms C17-C30 (the benzyl groups) were refined isotropically
while the remaining non-hydrogen atoms were refined aniso-
tropically. The hydrogen atoms were included in idealized
positions. The final cycle of full-matrix least-squares refine-
ment was based on 1335 observed reflections (I > 3.00σ(I)) and
220 variable parameters. All calculations were performed
using the TeXsan crystallographic software package of Mo-
lecular Structure Corp.
3
(t, J F-F ) 21.4 Hz, 3 F, p-F), -165.30 (s, br, 6 F, m-F).
-
In Situ Gen er a tion of (TCP )TiCH 2P h +B(C6F 5)4 (5).
-
(TCP)Ti(CH2Ph)2 (4.6 mg, 0.010 mmol) and Ph3C+B(C6F5)4
(9.2 mg, 0.010 mmol) were loaded in the glovebox into a J .
Young NMR tube, which was then attatched to the high-
vacuum line. CD2Cl2 (0.7-1 mL) was then vacuum-trans-
ferred into this tube at -78 °C. The NMR spectroscopy was
carried out at -60 °C. 1H NMR (CD2Cl2, -60 °C): δ 7.81 (t,
J H-H ) 7.5 Hz, 1 H), 7.65 (t, J H-H ) 7.5 Hz, 1 H), 7.43 (t, J H-H
) 7.5 Hz, 1 H), 7.40-6.90 (m, obscured by superimposed
signals of Ph3CCH2Ph), 6.09 (d, J H-H ) 8.1 Hz, 1 H), 3.84 (d,
J H-H ) 6.3 Hz, 1 H, Ti-CH2Ph), 2.96 (d, J H-H ) 6.3 Hz, 1 H,
Ti-CH2Ph), 2.44 (s, 3 H, Ar-CH3), 2.31 (s, 3 H, C5Me4), 2.13
(s, 3 H, C5Me4), 2.03 (s, 3 H, C5Me4), 1.59 (s, 3 H, C5Me4). A
small amount of dibenzyl (δ 2.83 ppm) was also detected in
the NMR reaction. 13C NMR (CD2Cl2, -60 °C): δ 82.56 (t, J C-H
) 150.8 Hz, Ti-CH2Ph). 19F NMR (CD2Cl2, -60 °C): δ -131.86
(s, br, 8 F, o-F), -161.08 (t, 3J F-F ) 21.2 Hz, 4 F, p-F), -165.03
(s, br, 8 F, m-F).
E t h ylen e, P r op ylen e, a n d St yr en e P olym er iza t ion
Exp er im en ts. Ethylene, propylene, and styrene polymeriza-
tions were carried out at room temperature in 250-mL flamed,
round-bottomed flasks equipped with magnetic stirring bars
and attached to the high-vacuum line. In a typical experiment,
a 1:1 ratio of (TCP)Ti(CH2Ph)2:cocatalyst in 2 mL of toluene
or 1,2-difluorobenzene (for those catalysts activated with
Ph3C+B(C6F5)4-), freshly prepared in the glovebox, was quickly
injected (using a gas-tight syringe equipped with a spraying
needle) into a rapidly stirred flask containing a measured
quantity of dry toluene, which was presaturated under 1.0 atm
of rigorously purified ethylene or propylene. The solution was
equilibrated at the desired reaction temperature using an
external constant-temperature bath. For styrene polymeri-
zation, the toluene solution contained 2.0 mL of freshly
distilled styrene under 1.0 atm of Ar. After a measured time
interval, the polymerization was quenched by the addition of
2% acidified methanol. The polymer was then collected by
filtration, washed with methanol, and dried on the high-
vacuum line overnight to a constant weight.
Resu lts a n d Discu ssion
Syn th esis of (TCP )H2 (1), (TCP )Ti(CH2P h )2 (2),
a n d (TCP )2Zr (3). The one-pot synthesis of the 2-(tet-
ramethylcyclopentadienyl)-4-methylphenol ligand (TCP)-
H2 is depicted in Scheme 1. The reaction of commeri-
cally available 2-bromo-4-methylphenol with 2 equiv of
nBuLi yields a dilithio salt, which is not isolated and is
next reacted with 2,3,4,5-tetramethyl-2-cyclopentenone
to produce ligand 1 (obtained as a single isomer judging
from the NMR) as a brown crystalline solid after
hydrolysis and subsequent vacuum distillation. This
(11) Sheldrick, G. M. SHELXS-86. In Crystallographic Computing;
Sheldrick, G. M., Kruger, C., Goddard, R., Eds.; Oxford University
Press: Oxford, 1985; pp 175-189.
(12) 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.
X-r a y Cr ysta llogr a p h ic Stu d ies of (TCP )Ti(CH2P h )2.
Orange crystals of (TCP)Ti(CH2Ph)2 were grown by slow

A Novel Phenolate Catalyst System
Organometallics, Vol. 16, No. 26, 1997 5961
Sch em e 1
Sch em e 2
approach can be compared to the conventional three-
step synthesis of Me2Si(C5Me4H)(tBuNH),4g,h with the
attraction of the present system being the efficient
synthetic procedure as well as the great potential steric
and electronic flexibility introducible via modification
of the aryl fragment.
F igu r e 1. Perspective ORTEP drawing of the molecular
structure of the complex (TCP)Ti(CH2Ph)2 (2). Thermal
ellipsoids are drawn at the 50% probability level.
Interestingly, in attempts to synthesize the corre-
sponding group 4 metal complexes from 1, both the
conventional metalation/salt elimination (double depro-
Sch em e 3
n
tonation with BuLi followed by metalation with MCl4)
and amine elimination approaches6c-h (1 + M(NMe2)4
at 110 °C for 3 days) gave complex mixtures of unidenti-
fied products. On the other hand, the alkane elimina-
tion approach reported3a earlier for the efficient syn-
thesis of group 4 constrained geometry catalysts afforded
the desired complex 2 (Scheme 2) in 50% yield. In
1
solution at room temperature, the H NMR spectrum
Ta ble 2. Selected Bon d Dista n ces (Å) a n d An gles
(d eg) for (TCP )Ti(CH2P h )2 (2)
of 2 reveals two magnetically equivalent benzyl groups,
each having diastereotopic benzylic protons at δ 2.50
and 2.32 ppm (J H-H ) 10.2 Hz). Although the observa-
tion of a normal Ph ipso-13C chemical shift at δ 147.87
Bond Distances
Ti-O
1.851(7)
2.36(1)
2.37(1)
2.121(10)
2.92(1)
1.36(1)
Ti-Cl
2.33(1)
2.39(1)
2.35(1)
2.13(1)
1.50(1)
1.49(1)
Ti-C2
Ti-C4
Ti-C17
Ti-C18
O-C15
Ti-C3
2
1
ppm, a CH2 J HH value of 10.2 Hz, and a CH2 J CH value
of 127.5 Hz can be taken as evidence against significant
ηn-benzyl bonding,4f,13 the solid state structural results
(see below) suggest rapid interconversion4f of one η1 and
one ηn group in solution at room temperature. The
corresponding reaction of 1 with Zr(CH2Ph)4 under the
same conditions yields a mixture of products. However,
at higher reaction temperatures (110 °C for 12 h), the
reaction yields a new, chiral chelated C2-symmetric
zirconocene14 (TCP)2Zr (3; Scheme 3) which has been
characterized spectroscopically and analytically. This
salt-free synthetic/ligational approach which by design
yields only the rac isomer may offer attractive features
in the stereoselective synthesis of other precursors for
rac-metallocene catalysts.
Ti-C5
Ti-C24
C24-C25
C17-C18
Bond Angles
O-Ti-C17
104.5(4)
O-Ti-C24
108.0(4)
106.7(7)
116.6(10)
112.6(10)
101.1(4)
Ti-O-C15
126.6(6)
127.2(7)
124(1)
128(1)
107.7(2)
Ti-C17-C18
O-C15-C10
C1-C10-C15
C17-Ti-C24
Ti-C24-C25
O-C15-C14
C1-C10-C11
Cp(centroid)-Ti-O
X-ray diffraction is shown in Figure 1, and important
bond distances and angles are summarized in Table 2.
The geometry around Ti is slightly distorted tetrahedral,
with a Cp(centroid)-Ti-O angle of 107.7(2)° and a
C17-Ti-C24 angle of 101.1(4)°. This acute Cp(cen-
troid)-Ti-O angle is nearly identical to that of the Cp-
Ti-N angle in Me2Si(Me4C5)(tBuN)TiCl2 (107.6),3f in-
dicating similar sterically open features for both
complexes as catalyst precursors. The Ti-Cring(av)
distance of 2.36(1) Å is probably slightly longer than
the corresponding distance in Me2Si(Me4C5)(tBuN)TiCl2
(2.340(5) Å).3f The (phenyl)C10-C1(ring) vector in 2 is
bent 15(1)° from the Me4Cp ring mean-square plane,
and the phenyl plane-Me4Cp plane dihedral angle is
81(1)°. The Ti-O bond length in 2 (1.851(7) Å) is
comparable to those reported for bent metallocene TiIV
and TiIII alkoxide complexes, such as Cp2Ti(OCHdCH2)2
Cr ysta l Str u ctu r e of (TCP )Ti(CH2P h )2 (2). The
solid state structure of 2 as derived from single-crystal
(13) (a) Bochmann, M.; Lancaster, S. J .; Hursthouse, M. B.; Malik,
K. M. A. Organometallics 1994, 13, 2235-2243. (b) Bochmann, M.;
Lancaster, S. J . Organometallics 1993, 12, 633-640. (c) J ordan, R. F.;
LaPointe, R. E.; Baenziger, N. C.; Hinch, G. D. Organometallics 1990,
9, 1539. (d) J ordan, R. F.; LaPointe, R. E.; Bajgur, C. S.; Echols, S. F.;
Willet, R. J . Am. Chem. Soc. 1987, 109, 4111. (e) Latesky, S. L.;
McMullen, A. K.; Niccolai, G. P.; Rothwell, I. P.; Huffman, J . C.
Organometallics 1985, 4, 902. (f) Mintz, E. A.; Moloy, K. G.; Marks, T.
J . J . Am. Chem. Soc. 1982, 104, 4692. (g) Davis, G. R.; J arvis, J . A.;
Kilburn, B. T. J . Chem. Soc., Chem. Commun. 1971, 15111.
(14) For related chelated complexes having different ligand frame-
works and prepared by different synthetic approaches, see refs 5c and
6h.

5962 Organometallics, Vol. 16, No. 26, 1997
Chen et al.
Sch em e 4
Sch em e 5
Ta ble 3. Su m m a r y of r-Olefin P olym er iza tion Ca ta lyzed by (TCP )Ti(CH2P h )2
polymer
yield (g)
entry
1
cocatalyst
B(C6F5)3
conditions
monomera
ethylene
activityb
Mw
Mw/Mn
>10
remarks
c
15 µmol of catalyst
100 mL of toluene, 30 min
15 µmol of catalyst
100 mL of toluene, 1 min
20 µmol of catalyst
50 mL of toluene, 5 min
0.11
1.47 × 104
1.27 × 106
Tm ) 142.5 °C
Ph3C+B(C6F5)4
Ph3C+B(C6F5)4
ethylene
0.52
6.37
2.10 × 106
3.82 × 106
1.14 × 106
2.36 × 104
>10
Tm ) 142.4 °C
-
-
2
3
propylene
1.85
[mm] ) 0.224
[mr] ) 0.512
[rr] ) 0.264
atactic
Ph3C+B(C6F5)4
25 µmol of catalyst
5 mL of toluene, 5 min
styrene
1.57
4.33 × 107
8.00 × 103
3.32
-
4
a
b
Carried out at 25 °C, 1 atm of ethylene, 1 atm of propylene, and 17.4 mmol of styrene. Activities in units of g of polymer/(mole of
catalyst‚atm‚h), except entry 4 in units of g of polystyrene/(mole of catalyst‚mole styrene‚h). c GPC relative to polystyrene standards.
-
(1.903(2) Å),15a Cp2Ti(OC2H5)Cl (1.855(2) Å),15b Cp2TiO-
(2,6-Me2C6H3) (1.892(2) Å),15c [C5H4(CH2)3O]TiCl2
(1.762(2) Å),5b and [C5Me4(CH2)3O]TiCl2 (1.767(1) Å),15d
where a partial Ti-O double-bond character involving
oxygen π-donation to the metal in addition to the
σ-interaction is associated with short Ti-O bond lengths.
On the other hand, the present Ti-O-C15 angle (126.6-
(6)°) is somewhat smaller than typical Ti-O-C angles,
as in the above examples (∼140°)15 where Ti-O multiple
bonding is assumed operative, reflecting the great steric
strain in 2, also evidenced by the 15° bend of the
(phenyl)C10-C1(ring) vector from the Me4Cp ring mean-
square plane.
Ph3C+B(C6F5)4 in CD2Cl2 indicate the formation of
cationic monobenzyl species, preparative-scale reactions
at higher temperature afford C-H activation products,
i.e., intramolecularly ring-metallated η1,η6-fulvene-type
complexes (e.g., Scheme 4).3a Likewise, the low-tem-
perature NMR-scale reactions of (TCP)Ti(CH2Ph)2 with
B(C6F5)3 and Ph3C+B(C6F5)4- in CD2Cl2 clearly indicate
the formation of the corresponding cationic mono-
benzyl species (TCP)TiCH2Ph+PhCH2B(C6F5)3- (4) and
(TCP)TiCH2Ph+B(C6F5)4- (5), respectively, with identi-
cal cation structures based upon the NMR analyses (the
formation of 5 is depicted in Scheme 5). The Ti-CH2-
1
Ph H NMR signals of 5 are observed at δ 3.84 (d, J H-H
The two benzyl ligands in complex 2 are inequivalent
in the solid state, with one engaging in normal η1-
bonding (Ti-C24 ) 2.13(1) Å; Ti-C24-C25 ) 127.2-
(7)°) and the other in partial η2-bonding, with Ti-C17
and Ti-Cipso(C18) distances of 2.121(10) and 2.92(1) Å,
respectively, and a Ti-C17-C18 angle of 106.7(7)°
(Figure 1).
Rea ction Ch em istr y of (TCP )Ti(CH2P h )2 w ith
B(C6F 5)3 a n d P h 3C+B(C6F 5)4-. The reaction of bis-
Cp-type metallocene dibenzyls with B(C6F5)3 and
Ph3C+B(C6F5)4- often generates the corresponding cat-
ionic complexes with η2-bonding of the remaining benzyl
group to the electrophilic metal center.3a,13a-c In
contrast, we previously found that the reaction of
the Me2Si(Me4C5)(tBuN)M(CH2Ph)2 complexes with
B(C6F5)3 and Ph3C+B(C6F5)4- follows a different course.3a
While low-temperature NMR-scale reactions of Me2Si-
(Me4C5)(tBuN)M(CH2Ph)2 complexes with B(C6F5)3 and
) 6.3 Hz) and 2.96 (d, J H-H ) 6.3 Hz) (CD2Cl2, -60 °C),
which is 1.34 and 0.64 ppm down-field-shifted, respec-
tively, from the benzyl resonances of neutral precursor
2 (δ 2.50 (d, J H-H ) 10.2 Hz) and 2.32 (d, J H-H ) 10.2
Hz) (C6D6, 23 °C)) as a consequence of cation formation.
η2-Coordination of the benzyl ligand in the cationic
complex is evidenced by a reduction of the value of 2J H-H
for the diastereotopic CH2Ph protons from 10.2 to 6.3
Hz, a high-field-shifted Ti-13CH2Ph signal (δ 82.56 ppm
1
in 5 vs 83.85 ppm in 2), and a large CH2 J CH value
(150.8 Hz in 5 vs 127.5 Hz in 2).13 However, despite
the clean NMR-scale reactions at low temperatures, and
unlike the case of the constrained geometry mono-
benzyls,3a preparative-scale reactions at higher temper-
atures are accompanied by extensive decomposition and
isolation of the cationic complexs could not be achieved
in this case.
r-Olefin P olym er iza tion Stu d ies. Table 3 sum-
marizes ethylene, propylene, and styrene polymerization
activities of (TCP)Ti(CH2Ph)2 upon activation with
B(C6F5)3 and Ph3C+B(C6F5)4- as well as the properties
of the resulting polymers. (TCP)Ti(CH2Ph)2 when
(15) (a) Curtis, M. D.; Thanedar, S.; Butler, W. M. Organometallics
1984, 3, 1855. (b) Huffman, J . C.; Moloy, K. G.; Marsella, J . A.; Caulton,
K. G. J . Am. Chem. Soc. 1980, 102, 3009. (c) Cetinkaya, B.; Hitchcock,
P. B.; Lappert, M. F.; Torroni, S.; Atwood, J . L.; Hunter, W. E.;
Zaworotko, M. J . J . Organomet. Chem. 1980, 188, C31. (d) Fandos, R.;
Meetsma, A.; Teuben, J . H. Organometallics 1991, 10, 59.
-
activated with Ph3C+B(C6F5)4 is a highly active cata-

A Novel Phenolate Catalyst System
Organometallics, Vol. 16, No. 26, 1997 5963
lyst for ethylene, propylene, and styrene polymerization,
producing high molecular weight (>106) polyethylenes
with high melting transition temperatures (Tm ) 142
°C), as well as atactic polypropylene and polystyrene.
The open nature of the catalytic site can be associated
with the low degree of polymerization stereocontrol, and
the homopoly R-olefin products are generally atactic,
similar to the performance of group 4 amido-based
constrained geometry catalysts.3c The broad polydis-
persities of the polyethylene products may be associated
with the rapid decomposition of the cationic species at
room temperature (possibly with the formation of η1,η6
“tuck-in” cations3a) or slow initiation with respect to the
fast propagation and significant inhomogenity during
the course of the catalytic reaction under the present
ethylene polymerization conditions. In contrast, pro-
pylene polymerization mediated by 2 activated with
sized by one-pot/one-step syntheses. The solid state
structure, cocatalyst activation chemistry, and perfor-
mance for olefin polymerization of the titanium complex
has been investigated in detail. The results consider-
ably expand what is known about constrained geometry
catalyst design and the consequent olefin polymerization
performance.
Ack n ow led gm en t. This research was supported by
the U.S. Department of Energy (Grant No. DE-FG 02-
86 ER 13511). Y.X.C. thanks Akzo-Nobel Chemicals for
a postdoctoral fellowship. We thank Dr. Tetsuo Ohta
for helpful discussions concerning the ligand synthesis.
Su p p or tin g In for m a tion Ava ila ble: Text giving com-
plete X-ray experimental details and tables of crystal data,
intensity measurements, structure solution and refinement,
atomic coordinates, torsion angles, and bond lengths and
angles, and ORTEP diagram of 2 (26 pages). Ordering
information is given on any current masthead page.
-
Ph3C+B(C6F5)4 is both very rapid and produces a
polymer having narrow polydispersity, which can be
attributed to the structurally open nature of the cationic
metal coordination sphere (catalytic activity is not
affected by the steric encumberence of monomer) and
apparently greater stabilization of the catalytic sites in
the presence of propylene. The substantial activity
difference of identical cations having different counter-
anions (entry 1 vs 2) further demonstrates the signifi-
cant influence of the anion identity on catalytic activity,
as previously shown in detail by us and others.16
In summary, a novel phenolic bifunctional mono-Cp
constrained geometry ligand framework and the Ti and
Zr complexes thereof have been designed and synthe-
OM9707376
(16) (a) Chen, Y.-X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc.
1997, 119, 2582-2583. (b) J ia, L.; Yang, X.; Stern, C. L.; Marks, T. J .
Organometallics 1997, 16, 842-857. (c) Chen, Y.-X.; Stern, C. L.; Yang,
S.; Marks, T. J . J . Am. Chem. Soc. 1996, 118, 12451-12452. (d) Deck,
P. A.; Marks, T. J . J . Am. Chem. Soc. 1995, 117, 6128-6129. (e)
Giardello, M. A.; Eisen, M. S.; Stern, C. L.; Marks, T. J . J . Am. Chem.
Soc. 1995, 117, 12114-12129. (f) J ia, L.; Yang, X.; Ishihara, A.; Marks,
T. J . Organometallics 1995, 14, 3135-3137. (g) Chien, J . C. W.; Song,
W.; Rausch, M. D. J . Polym. Sci., Part A: Polym. Chem. 1994, 32,
2387-2393. (h) Eisch, J .; Pombrik, S. I.; Zheng, G.-X. Organometallics
1993, 12, 3856-3863. (i) Siedle, A. R.; Lamanna, W. M.; Newmark, R.
A.; Stevens, J .; Richardson, D. E.; Ryan, M. Makromol. Chem.,
Macromol. Symp. 1993, 66, 215-224.