Group 4 metal olefin polymerization catalysts stabilized by bidentate O,P ligands

Article abstract of DOI:10.1021/om7008149

A series of bis(phosphanylphenoxide) group 4 metal dichloride complexes has been synthesized via treatment of MCl₄(THF)₂ (M = Ti, Zr, Hf) with sodium salts of the phosphanylphenols. The complexes bearing diphenylphosphine donors adopt C₁-symmetric, all-cis ground-state structures as determined by X-ray crystallography. In solution an O,P ligand exchange process is observed. Eyring analyses indicate a nondissociative process proposed to proceed via a 120° rotation of the P,P,C1 or the O,P,C1 trigonal faces. A zirconium complex containing diisopropylphosphine donors adopts a configurationally rigid trans-P₂ geometry. In ethylene polymerization studies (methylaluminoxane (MAO) activation), bis(6-ierf-butyl-2-diphenylphosphanylphenoxide) zirconium and hafnium catalysts gave activities up to 49 000 and 2000 g/mmol ·h ·bar, respectively. Both of these catalysts also afforded efficient catalyzed chain growth using ZnEt₂. The zirconium derivative afforded activities up to 13 300 g/mmol ·h for propylene polymerization using dried -MAO (DMAO) as the cocatalyst. The polymer had a slight syndiotactic bias and is formed by a chain-end control mechanism. A dibenzyl analogue of the highly active zirconium catalyst revealed an all-cis structure by crystallography, but a mixture of isomers in solution by NMR spectroscopy. Cationic monoalkyl complexes were synthesized using either [CPh ₃][B(C₆F₅)₄] or DMAO and suggest a highly fluxional structure for the catalytically active species.

Full text of DOI:10.1021/om7008149

Organometallics 2008, 27, 235–245
235
Group 4 Metal Olefin Polymerization Catalysts Stabilized by
Bidentate O,P Ligands
Richard J. Long, Vernon C. Gibson,* and Andrew J. P. White
Department of Chemistry, Imperial College London, Exhibition Road, London, U.K., SW7 2AZ
ReceiVed August 9, 2007
A series of bis(phosphanylphenoxide) group 4 metal dichloride complexes has been synthesized
via treatment of MCl4(THF)2 (M ) Ti, Zr, Hf) with sodium salts of the phosphanylphenols. The
complexes bearing diphenylphosphine donors adopt C1-symmetric, all-cis ground-state structures as
determined by X-ray crystallography. In solution an O,P ligand exchange process is observed. Eyring
analyses indicate a nondissociative process proposed to proceed via a 120° rotation of the P,P,Cl or
the O,P,Cl trigonal faces. A zirconium complex containing diisopropylphosphine donors adopts a
configurationally rigid trans-P2 geometry. In ethylene polymerization studies (methylaluminoxane
(MAO) activation), bis(6-tert-butyl-2-diphenylphosphanylphenoxide) zirconium and hafnium catalysts
gave activities up to 49 000 and 2000 g/mmol · h · bar, respectively. Both of these catalysts also
afforded efficient catalyzed chain growth using ZnEt2. The zirconium derivative afforded activities
up to 13 300 g/mmol · h for propylene polymerization using “dried”-MAO (DMAO) as the cocatalyst.
The polymer had a slight syndiotactic bias and is formed by a chain-end control mechanism. A
dibenzyl analogue of the highly active zirconium catalyst revealed an all-cis structure by
crystallography, but a mixture of isomers in solution by NMR spectroscopy. Cationic monoalkyl
complexes were synthesized using either [CPh3][B(C6F5)4] or DMAO and suggest a highly fluxional
structure for the catalytically active species.
evidence that softer second-row donors may offer beneficial
stabilization of the highly reactive metal center.14c,h,20 While
there have been a growing number of reports concerning
catalyststhatcombinephenoxideswiththioetherdonors2a,b,7e,14c,h,19g,21,22
there has been little focus on ligands containing tertiary
phosphines14c,d,j,23,24 Therefore bis(o-phosphanylphenoxide) com-
plexes of the group 4 metals25,26 appeared attractive; additional
benefits include (i) a fairly straightforward synthesis (Vide infra)
with several sites around the ligand amenable to elaboration,
(ii) a rigid phenylene bridge, which should help to enforce
phosphine coordination, and (iii) an active species that could
Introduction
Ligands containing monoanionic oxygen donors, especially
phenoxides, have proved to be a popular alternative to the
cyclopentadienyl fragment in post-metallocene olefin polym-
erization catalysts.1 Although simple group 4 metal bis-
phenoxide catalysts are active,2 additional neutral donors are
often incorporated into the ligand frame to occupy sites of
coordinative unsaturation not needed for chain growth.2a,b,3–19,21,22
Such additional donors may also help to “rigidify” the structure
of the complex and open up the possibility for stereoselective
polymerizations using prochiral olefins.
In group 4 metal complexes, the phenoxide donors tend to
be matched with relatively hard first-row nitrogen-3–18 and
14c,h,19
7
(5) (a) Repo, T.; Klinga, M.; Pietikäinen, P.; Leskelä, M.; Uusitalo, A.-
M.; Pakkanen, T.; Hakala, K.; Aaltonen, P.; Löfgren, B. Macromolecules
1997, 30, 171. (b) Huang, J.; Lian, B.; Yong, L.; Qian, Y. Inorg. Chem.
Commun. 2001, 4, 392. (c) Knight, P. D.; Clarke, A. J.; Kimberley, B. S.;
Jackson, R. A.; Scott, P. Chem. Commun. 2002, 352. (d) Ishii, S.; Mitani,
M.; Saito, J.; Matsuura, S.; Furuyama, R.; Fujita, T. Stud. Surf. Sci. Catal.
2003, 145, 49. (e) Wang, M.; Zhu, H.; Jin, K.; Dai, D.; Sun, L. J. Catal.
2003, 220, 392. (f) Cuomo, C.; Strianese, M.; Cuenca, T.; Sanz, M.; Grassi,
A. Macromolecules 2004, 37, 7469. (g) Zhu, H.; Wang, M.; Ma, C.; Li,
B.; Chen, C.; Sun, L. J. Organomet. Chem. 2005, 690, 3929. (h) Lamberti,
M.; Consolmagno, M.; Mazzeo, M.; Pellecchia, C. Macromol. Rapid
Commun. 2005, 26, 1866. (i) Strianese, M.; Lamberti, M.; Mazzeo, M.;
Tedesco, C.; Pellecchia, C. J. Mol. Catal. A: Chem. 2006, 258, 284. (j)
Clarkson, G. J.; Gibson, V. C.; Goh, P. K. Y.; Hammond, M. L.; Knight,
P. D.; Scott, P.; Smit, T. M.; White, A. J. P.; Williams, D. J. Dalton Trans.
2006, 5484.
(6) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2000,
122, 10706. (b) Busico, V.; Cipullo, R.; Ronca, S.; Budzelaar, P. H. M.
Macromol. Rapid Commun. 2001, 22, 1405. (c) Busico, V.; Cipullo, R.;
Friederichs, N.; Ronca, S.; Togrou, M. Macromolecules 2003, 36, 3806.
(d) Busico, V.; Cipullo, R.; Friederichs, N.; Ronca, S.; Talarico, G.; Togrou,
M.; Wang, B. Macromolecules 2004, 37, 8201. (e) Segal, S.; Goldberg, I.;
Kol, M. Organometallics 2005, 24, 200. (f) Yeori, A.; Goldberg, I.; Shuster,
M.; Kol, M. J. Am. Chem. Soc. 2006, 128, 13062. (g) Busico, V.; Cipullo,
R.; Pellecchia, R.; Ronca, S.; Roviello, G.; Talarico, G. Proc. Natl. Acad.
Sci. U.S.A. 2006, 103, 15321.
oxygen-based c,f-i,
donors. However, there is growing
* To whom correspondence should be addressed. E-mail:
v.gibson@imperial.ac.uk.
(1) (a) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428. (b) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV.
2003, 103, 283. (c) Suzuki, Y.; Terao, H.; Fujita, T. Bull. Chem. Soc. Jpn.
2003, 76, 1493. (d) Kawaguchi, H.; Matsuo, T. J. Organomet. Chem. 2004,
689, 4228.
(2) (a) van der Linden, A.; Schaverien, C. J.; Meijboom, N.; Ganter,
C.; Orpen, A. G. J. Am. Chem. Soc. 1995, 117, 3008. (b) Sernetz, F. G.;
Mülhaupt, R.; Fokken, S.; Okuda, J. Macromolecules 1997, 30, 1562. (c)
Fokken, S.; Spaniol, T. P.; Okuda, J.; Sernetz, F. G.; Mülhaupt, R.
Organometallics 1997, 16, 4240. (d) Thorn, M. G.; Etheridge, Z. C.;
Fanwick, P. E.; Rothwell, I. P. Organometallics 1998, 17, 3636. (e) Thorn,
M. G.; Etheridge, Z. C.; Fanwick, P. E.; Rothwell, I. P. J. Organomet.
Chem. 1999, 591, 148.
(3) (a) For recent reviews on bis(phenoxyimine) catalysts see: Mitani,
M.; Saito, J.; Ishii, S.-I.; Nakayama, Y.; Makio, H.; Matsukawa, N.; Matsui,
S.; Mohri, J.-I.; Furuyama, R.; Terao, H.; Bando, H.; Tanaka, H.; Fujita, T.
Chem. Rec. 2004, 4, 137. (b) Nakayama, Y.; Bando, H.; Sonobe, Y.; Fujita,
T. Bull. Chem. Soc. Jpn. 2004, 77, 617. (c) Makio, H.; Fujita, T. Bull. Chem.
Soc. Jpn. 2005, 78, 52. (d) Sakuma, A.; Weiser, M.-S.; Fujita, T. Polym. J.
2007, 39, 193.
(4) Suzuki, Y.; Kashiwa, N.; Fujita, T. Chem. Lett. 2002, 358.
10.1021/om7008149 CCC: $40.75
2008 American Chemical Society
Publication on Web 12/29/2007

236 Organometallics, Vol. 27, No. 2, 2008
Long et al.
parallel the highly active group 4 metal phenoxyimine systems3
and offer a new class of early transition metal polymerization
catalyst with the potential to influence polymer microstructure
and stereochemistry.
deprotection strategy of Rauchfuss27 (Scheme 1). In each case
a hitherto unreported phosphonium salt was obtained that
required treatment with ammonia to effect deprotection of the
proligand. This product (A) was isolated and characterized
during the synthesis of 6-(tert-butyl)-2-diphenylphosphanylphe-
nol and revealed a hydroxymethyl substituent attached to the
phosphorus center, presumably formed by an intramolecular
attack during the MOM deprotection (Scheme 2; the structure
of the salt was confirmed by crystallography; see Supporting
Information).
Results and Discussion
Complex Synthesis and Structure. A range of ortho-
substituted phosphanylphenols was synthesized from the cor-
responding phenols using the MOM protection, lithiation,
(7) (a) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Inorg.
Chem. Commun. 2000, 3, 611. (b) Tshuva, E. Y.; Goldberg, I.; Kol, M.;
Weitman, H.; Goldschmidt, Z. Chem. Commun. 2000, 379. (c) Tshuva,
E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Chem. Commun. 2001, 2120.
(d) Tshuva, E. Y.; Goldberg, I.; Kol, M.; Goldschmidt, Z. Organometallics
2001, 20, 3017. (e) Groysman, S.; Tshuva, E. Y.; Reshef, D.; Gendler, S.;
Goldberg, I.; Kol, M.; Goldschmidt, Z.; Shuster, M.; Lidor, G. Isr. J. Chem.
2002, 42, 373. (f) Tshuva, E. Y.; Groysman, S.; Goldberg, I.; Kol, M.;
Goldschmidt, Z. Organometallics 2002, 21, 662. (g) Groysman, S.;
Goldberg, I.; Kol, M.; Genizi, E.; Goldschmidt, Z. Inorg. Chim. Acta 2003,
345, 137. (h) Groysman, S.; Goldberg, I.; Kol, M.; Genizi, E.; Goldschmidt,
Z. Organometallics 2003, 22, 3013. (i) Groysman, S.; Tshuva, E. Y.;
Goldberg, I.; Kol, M.; Goldschmidt, Z.; Shuster, M. Organometallics 2004,
23, 5291. (j) Reybuck, S. E.; Lincoln, A. L.; Ma, S.; Waymouth, R. M.
Macromolecules 2005, 38, 2552. (k) Gendler, S.; Groysman, S.; Gold-
schmidt, Z.; Shuster, M.; Kol, M. J. Polym. Sci., Part A: Polym. Chem.
2006, 44, 1136.
(19) (a) Matilainen, L.; Klinga, M.; Leskelä, M. J. Chem. Soc., Dalton
Trans. 1996, 219. (b) Sobota, P.; Przybylak, K.; Utko, J.; Jerzykiewicz,
L. B.; Pombeiro, A. J. L.; Guedes da Silva, M. F. C.; Szczegot, K.
Chem.-Eur. J. 2001, 7, 951. (c) Motta, O.; Capacchione, C.; Proto, A.;
Acierno, D. Polymer 2002, 43, 5847. (d) Capacchione, C.; Neri, P.; Proto,
A. Inorg. Chem. Commun. 2003, 6, 339. (e) Reimer, V.; Spaniol, T. P.;
Okuda, J.; Ebeling, H.; Tuchbreiter, A.; Mulhaupt, R. Inorg. Chim. Acta
2003, 345, 221. (f) Suzuki, Y.; Inoue, Y.; Tanaka, H.; Fujita, T. Macromol.
Rapid Commun. 2004, 25, 493. (g) Boussie, T. R.; Brümmer, O.; Diamond,
G. M.; Goh, C.; LaPointe, A. M.; Leclerc, M. K.; Shoemaker, J. A. W.
(Symyx Technologies, Inc.) US 7126031 B2, 2006.
(20) (a) Froese, R. D. J.; Musaev, D. G.; Matsubara, T.; Morokuma, K.
J. Am. Chem. Soc. 1997, 119, 7190. (b) Froese, R. D. J.; Musaev, D. G.;
Matsubara, T.; Morokuma, K. Organometallics 1999, 18, 373. (c) Porri,
L.; Ripa, A.; Colombo, P.; Miano, E.; Capelli, S.; Meille, S. V. J.
Organomet. Chem. 1996, 514, 213. (d) Lavanant, L.; Silvestru, A.;
Faucheux, A.; Toupet, L.; Jordan, R. F.; Carpentier, J. F. Organometallics
2005, 24, 5604.
(21) (a) Miyatake, T.; Mizunuma, K.; Seki, Y.; Kakugo, M. Makromol.
Chem., Rapid Commun. 1989, 10, 349. (b) Miyatake, T.; Mizunuma, K.;
Kakugo, M. Makromol. Chem., Macromol. Symp. 1993, 66, 203. (c) Fokken,
S.; Spaniol, T. P.; Kang, H. C.; Massa, W.; Okuda, J. Organometallics
1996, 15, 5069. (d) Janas, Z.; Jerzykiewicz, L. B.; Przybylak, K.; Sobota,
P.; Szczegot, K. Eur. J. Inorg. Chem. 2004, 1639. (e) Natrajan, L. S.; Wilson,
C.; Okuda, J.; Arnold, P. L. Eur. J. Inorg. Chem. 2004, 3724. (f) Janas, Z.;
Jerzykiewicz, L. B.; Przybylak, K.; Sobota, P.; Szczegot, K.; Wisniewska,
D. Eur. J. Inorg. Chem. 2005, 1063. (g) Janas, Z.; Jerzykiewicz, L. B.;
Sobota, P.; Szczegot, K.; Wisniewska, D. Organometallics 2005, 24, 3987.
(h) Wisniewska, D.; Janas, Z.; Sobota, P.; Jerzykiewicz, L. B. Organome-
tallics 2006, 25, 6166.
(22) (a) Capacchione, C.; Proto, A.; Ebeling, H.; Muelhaupt, R.; Moller,
K.; Spaniol, T. P.; Okuda, J. J. Am. Chem. Soc. 2003, 125, 4964. (b) Proto,
A.; Capacchione, C.; Venditto, V.; Okuda, J. Macromolecules 2003, 36,
9249. (c) Capacchione, C.; Proto, A.; Ebeling, H.; Mulhaupt, R.; Moller,
K.; Manivannan, R.; Spaniol, T. P.; Okuda, J. J. Mol. Catal. A, Chem. 2004,
213, 137. (d) Capacchione, C.; D’Acunzi, M.; Motta, O.; Oliva, L.; Proto,
A.; Okuda, J. Macromol. Chem. Phys. 2004, 205, 370. (e) Capacchione,
C.; Proto, A.; Okuda, J. J. Polym. Sci., Part A: Polym. Chem. 2004, 42,
2815. (f) Beckerle, K.; Capacchione, C.; Ebeling, H.; Manivannan, R.;
Mulhaupt, R.; Proto, A.; Spaniol, T. P.; Okuda, J. J. Organomet. Chem.
2004, 689, 4636. (g) Capacchione, C.; De Carlo, F.; Zannoni, C.; Okuda,
J.; Proto, A. Macromolecules 2004, 37, 8918. (h) Capacchione, C.;
Manivannan, R.; Barone, M.; Beckerle, K.; Centore, R.; Oliva, L.; Proto,
A.; Tuzi, A.; Spaniol, T. P.; Okuda, J. Organometallics 2005, 24, 2971. (i)
De Carlo, F.; Capacchione, C.; Schiavo, V.; Proto, A. J. Polym. Sci., Part
A: Polym. Chem. 2006, 44, 1486. (j) Capacchione, C.; Proto, A.; Ebeling,
H.; Mülhaupt, R.; Okuda, J. J. Polym. Sci., Part A: Polym. Chem. 2006,
44, 1908. (k) Beckerle, K.; Manivannan, R.; Spaniol, H. P.; Okuda, J.
Organometallics 2006, 25, 3019.
(8) (a) Huang, J.; Lian, B.; Qian, Y.; Zhou, W.; Chen, W.; Zheng, G.
Macromolecules 2002, 35, 4871. (b) Bott, R. K. J.; Hughes, D. L.;
Schormann, M.; Bochmann, M.; Lancaster, S. J. J. Organomet. Chem. 2003,
665, 135. (c) Sanz, M.; Cuenca, T.; Galakhov, M.; Grassi, A.; Bott, R. K. J.;
Hughes, D. L.; Lancaster, S. J.; Bochmann, M. Organometallics 2004, 23,
5324. (d) Chen, Q.; Huang, J.; Yu, J. Inorg. Chem. Commun. 2005, 8, 444.
(e) Coles, S. R.; Clarkson, G. J.; Gott, A. L.; Munslow, I. J.; Spitzmesser,
S. K.; Scott, P. Organometallics 2006, 25, 6019.
(9) (a) Chan, M. C. W.; Tam, K.-H.; Pui, Y.-L.; Zhu, N. J. Chem. Soc.,
Dalton Trans. 2002, 3085. (b) Chan, M. C. W.; Tam, K.-H.; Zhu, N.; Chiu,
P.; Matsui, S. Organometallics 2006, 25, 785.
(10) Kui, S. C. F.; Zhu, N.; Chan, M. C. W. Angew. Chem., Int. Ed.
2003, 42, 1628.
(11) Bei, X.; Swenson, D. C.; Jordan, R. F. Organometallics 1997, 16,
3282.
(12) Inoue, Y.; Nakano, T.; Tanaka, H.; Kashiwa, N.; Fujita, T. Chem.
Lett. 2001, 1060.
(13) (a) Cozzi, P. G.; Gallo, E.; Floriani, C.; Chiesi-Villa, A.; Rizzoli,
C. Organometallics 1995, 14, 4994. (b) Bott, R. K. J.; Hammond, M.;
Horton, P. N.; Lancaster, S. J.; Bochmann, M.; Scott, P. Dalton Trans.
2005, 3611.
(14) (a) Pennington, D. A.; Hughes, D. L.; Bochmann, M.; Lancaster,
S. J. Dalton Trans. 2003, 3480. (b) Owiny, D.; Parkin, S.; Ladipo, F. T. J.
Organomet. Chem. 2003, 678, 134. (c) Oakes, D. C. H.; Kimberley, B. S.;
Gibson, V. C.; Jones, D. J.; White, A. J. P.; Williams, D. J. Chem. Commun.
2004, 2174. (d) Hu, W.-Q.; Sun, X.-L.; Wang, C.; Gao, Y.; Tang, Y.; Shi,
L.-P.; Xia, W.; Sun, J.; Dai, H.-L.; Li, X.-Q.; Yao, X.-L.; Wang, X.-R.
Organometallics 2004, 23, 1684. (e) Pennington, D. A.; Clegg, W.; Coles,
S. J.; Harrington, R. W.; Hursthouse, M. B.; Hughes, D. L.; Light, M. E.;
Schormann, M.; Bochmann, M.; Lancaster, S. J. Dalton Trans. 2005, 561.
(f) Wang, C.; Sun, X.-L.; Guo, Y.-H.; Gao, Y.; Liu, B.; Ma, Z.; Xia, W.;
Shi, L.-P.; Tang, Y. Macromol. Rapid Commun. 2005, 26, 1609. (g) Oakes,
D. C. H.; Gibson, V. C.; White, A. J. P.; Williams, D. J. Inorg. Chem.
2006, 45, 3476. (h) Wang, C.; Ma, Z.; Sun, X.-L.; Gao, Y.; Guo, Y.-H.;
Tang, Y.; Shi, L.-P. Organometallics 2006, 25, 3259. (i) Paolucci, G.;
Zanella, A.; Sperni, L.; Bertolasi, V.; Mazzeo, M.; Pellecchia, C. J. Mol.
Catal. A: Chem. 2006, 258, 275. (j) Said, M.; Hughes, D. L.; Bochmann,
M. Inorg. Chim. Acta 2006, 359, 3467.
(23) (a) Baxter, S. M.; Wolczanski, P. T. O,P ligated group 4 metal
complexes that have not been evaluated for olefin polymerization include
the following. Organometallics 1990, 9, 2498. (b) van Doorn, J. A.; van
der Heijden, H.; Orpen, A. G. Organometallics 1994, 13, 4271. (c) Miquel;
L.; Bassobert, M.; Choukroun, R.; Madhouni, R.; Eichhorn, B.; Sanchez,
M.; Mazières, M. R.; Jaud, J. J. Organomet. Chem. 1995, 490, 21. (d)
Willoughby, C. A.; Duff, R. R.; Davis, W. M.; Buchwald, S. L. Organo-
metallics 1996, 15, 472. (e) Priya, S.; Balakrishna, M. S.; Mague, J. T.
Chem. Lett. 2004, 33, 308. (f) Liang, L.-C.; Chang, Y.-N.; Lee, H. M. Inorg.
Chem. 2007, 46, 2666.
(15) (a) Milione, S.; Montefusco, C.; Cuenca, T.; Grassi, A. Chem.
Commun. 2003, 1176. (b) Milione, S.; Bertolasi, V.; Cuenca, T.; Grassi,
A. Organometallics 2005, 24, 4915. (c) Cuomo, C.; Milione, S.; Grassi, A.
Macromol. Rapid Commun. 2006, 27, 611.
(16) Kraft, B. M.; Huang, K.-W.; Cole, A. P.; Waymouth, R. M. HelV.
Chim. Acta 2006, 89, 1589.
(24) O,P nickel complexes have been extensively studied as oligomer-
ization catalysts. For a recent review see: Kuhn, P.; Sémeril, D.; Matt, D.;
Chetcuti, M. J.; Lutz, P. Dalton Trans. 2007, 515.
(17) (a) Wang, W.; Fujiki, M.; Nomura, K. Macromol. Rapid Commun.
2004, 25, 504. (b) Padmanabhan, S.; Katao, S.; Nomura, K. Organometallics
2007, 26, 1616.
(25) Long, R. J.; Gibson, V. C.; White, A. J. P.; Williams, D. J. Inorg.
Chem. 2006, 45, 511.
(18) (a) Pennington, D. A.; Coles, S. J.; Hursthouse, M. B.; Bochmann,
M.; Lancaster, S. J. Chem. Commun. 2005, 3150. (b) Pennington, D. A.;
Coles, S. J.; Hursthouse, M. B.; Bochmann, M.; Lancaster, S. J. Macromol.
Rapid Commun. 2006, 27, 599. (c) Bryliakov, K. P.; Kravtsov, E. A.;
Broomfield, L.; Talsi, E. P.; Bochmann, M. Organometallics 2007, 26, 288.
(26) (a) Kashiwamura, T.; Okamoto, T. (Idemitsu Petrochemical Co.)
US 6730626 B2, 2004. (b) Gibson, V. C.; Jacobsen, G. B.; Jones, D. J.;
Long, R. J. (Innovene Europe Ltd) US 7144839 B2, 2006.
(27) Rauchfuss, T. B. Inorg. Chem. 1977, 16, 2966.

Group 4 Metal Olefin Polymerization Catalysts
Organometallics, Vol. 27, No. 2, 2008 237
Table 1. Selected Bond Lengths (Å) and Angles (deg) for
Complexes 3 (molecules I and II), 4, and 6
Scheme 1. Synthesis of Bis(phosphanylphenoxide)M(IV)
Dichloride Complexes (OMOM ) OCH2OCH3)
3 (I)
3 (II)
[M ) Ti] [M ) Ti] 4 [M ) Zr] 6 [M ) Hf]
M-O(1)
1.839(2)
1.874(2)
1.8388(19) 1.9632(15)
1.956(3)
1.989(3)
M-O(2)
1.837(2)
1.9889(14)
2.8872(6)
2.8208(6)
2.4239(6)
2.4263(6)
170.66(2)
154.08(5)
152.95(5)
96.87(2)
103.30(2)
101.81(5)
92.55(5)
85.026(19)
84.69(2)
M-P(1)
M-P(2)
M-Cl(1)
M-Cl(2)
Cl(1)-M-P(1)
Cl(2)-M-O(2) 161.34(7) 160.62(7)
P(2)-M-O(1) 159.34(7) 163.71(7)
Cl(1)-M-Cl(2) 94.95(3)
Cl(1)-M-P(2) 92.18(3)
Cl(1)-M-O(1) 105.87(7) 101.22(7)
Cl(1)-M-O(2) 93.52(7)
Cl(2)-M-P(1)
Cl(2)-M-P(2)
Cl(2)-M-O(1) 100.04(7) 97.95(7)
P(1)-M-P(2)
P(1)-M-O(1)
P(1)-M-O(2)
P(2)-M-O(2)
O(1)-M-O(2)
2.7055(8) 2.7408(9)
2.6309(8) 2.6979(9)
2.2679(9) 2.2794(9)
2.3177(8) 2.3307(9)
178.98(4) 170.81(4)
2.8628(11)
2.7954(11)
2.4058(11)
2.4060(12)
169.99(4)
155.76(10)
154.30(10)
96.37(5)
103.34(4)
100.33(10)
92.43(9)
86.04(4)
85.37(4)
101.88(11)
86.52(3)
69.66(10)
89.20(9)
70.61(9)
98.68(14)
94.15(3)
92.88(3)
Scheme 2. Proposed Mechanism for Formation of A
95.13(8)
81.17(3)
89.03(3)
86.07(3)
88.05(3)
102.16(5)
85.965(16)
68.86(5)
89.57(4)
69.62(4)
87.96(2)
73.81(7)
85.54(6)
75.03(6)
93.57(9)
94.94(3)
71.81(6)
91.73(7)
73.54(6)
96.89(9)
The phosphanylphenols were converted to sodium salts using
NaH and reacted with MCl4(THF)2 (M ) Ti, Zr, and Hf) to
give the desired complexes 1-6 as analytically pure air- and
moisture-sensitive solids (Scheme 1). The bis-O,P structures of
1 and 3-6 were confirmed by single-crystal X-ray analyses.
The structures of 3 and 4 are discussed below; analyses of 1, 5,
and 6 have been reported previously and revealed all-cis
structures for 1 and 6 and a trans-P2 structure for 5.25
99.44(6)
dination sphere “stationary” (these atoms have an rms fit of ca.
0.06 Å in the two molecules), this difference can be viewed as
a bending of the aryl ring of the P(1)/O(1) ligand about the
P · · · O vector either toward or away from O(2) (see Figure S6
in the Supporting Information). This flexing is accompanied by
a shift in the P(1) position between the two molecules by ca.
0.37 Å. The different conformations of the C2OPTi rings may
be caused by steric interactions between the two tert-butyl
substituents as the analogous chelates in 1 are planar to within
0.04 Å.25 The trans influence of the various donors can be seen
by inspection of the Ti-X bond lengths (Table 1). The Ti-P(1)
bond is longer than its Ti-P(2) counterpart, reflecting the
difference between a chloride and a (phen)oxide, respectively,
in the trans position. Likewise, Ti-Cl(2) is longer than
Ti-Cl(1), reflecting the difference between a formally monoan-
ionic oxygen donor and a neutral phosphorus donor, and
Ti-O(2) is longer than Ti-O(1) [in complex I but not,
strangely, in complex II], showing the difference between
chloride and phosphorus.
The solid-state structure of 3 revealed the presence of two
crystallographically independent molecules (I and II) in the
asymmetric unit (molecule I is shown in Figure 1, molecule II
in Figure S4 in the Supporting Information). The coordination
sphere for each molecule is distorted octahedral with cis angles
being in the ranges 73.81(7)–105.87(7)° and 71.81(6)–101.22(7)°
for molecules I and II, respectively; the two most acute angles
in each case are associated with the bites of the O,P ligands.
The primary difference between the molecules is not the
arrangement of the donor atoms, which, like in 1 and 6, are
all-cis, but the conformation of the P(1)/O(1) ligand. This
difference can be readily appreciated by considering the folding
of the five-membered C2OPTi chelate rings. While for both
complexes the P(2)/O(2) ring is essentially planar (the five atoms
being coplanar to within ca. 0.03 and 0.01 Å for molecules I
and II, respectively), the P(1)/O(1) ring in each case has an
envelope conformation with the metal lying out of the C2OP
plane (coplanar to within ca. 0.02 Å). For molecule I the metal
lies ca. 0.57 Å out of this plane in the direction of O(2), whereas
for molecule II the metal lies ca. 0.63 Å in the opposite direction
toward Cl(2′). Keeping the Ti,Cl(1),Cl(2),P(2),O(1),O(2) coor-
The crystal structure of the zirconium complex 4 (Figure 2)
is very similar to that of 3-I. The geometry at the metal center
isdistortedoctahedralwithcisanglesintherange68.86(5)–103.30(2)°.
The coordination sphere is all-cis, and the two five-membered
C2OPZr chelate rings have different geometries; the P(2)/O(2)
Figure 1. Molecular structure of I, one of the two independent
molecules present in the crystals of 3.
Figure 2. Molecular structure of 4.

238 Organometallics, Vol. 27, No. 2, 2008
Scheme 3. Interchange of all-cis enantiomers.
Long et al.
the temperature range 203–363 K in toluene-d8; selected 31P
NMR spectra and calculated exchange rates are shown in Figure
3, and activation parameters are in Table 2. Significantly, for
each complex a negative entropy of activation was obtained,
suggesting that rearrangement of the ligands occurs via a
nondissociative mechanism.31 There are two possible nondis-
sociative pathways for the interconversion of all-cis enantiomers
in (O,P)2MCl2 complexes;32,33 these are shown in Figure 4.
The first involves a 120° rotation about an O,P,Cl trigonal
face with the two chelate rings confined to each face (C2V-
symmetric transition state); the second requires a 120° rotation
about the P,P,Cl face with the chelate rings spanning the two
trigonal faces (Cs-symmetric transition state). These mechanisms
are not distinguishable by NMR spectroscopy. What is clear is
that the rate of this rearrangement is determined by the steric
bulk of the substituents ortho to the phenoxide donors, with 2,
bearing phenyl substituents, exchanging 100 times faster at 303
K than 3, which contains tert-butyl groups (this difference is
almost entirely entropic). Otherwise the separation of the trigonal
faces, determined by the radii of the metal centers (Ti < Zr >
Hf), appears to play a key role in controlling the rate of ligand
exchange.
The NMR spectra of 5 afforded a single set of resonances
for the O,P ligands in accord with the ground-state structure
established by crystallography.25 Comparable spectra were
obtained at 323 and 223 K, indicating a nonfluxional structure.
Ethylene Polymerization Studies. Complexes 1-6 were
investigated as catalysts for ethylene polymerization34 using
methylaluminoxane (MAO) as the cocatalyst; activity and
molecular weight data are collected in Table 3. The produc-
tivities of the titanium catalysts, 1-3/MAO, are clearly im-
proved when a bulky substituent is positioned ortho to the
phenoxide donor. Increasing bulk also gives order of magnitude
increases in molecular weight with concurrent decreases in the
polydispersity index (PDI). Similar observations have been noted
by Fujita et al. for phenoxyimine catalyst systems.3 Analyses
of the polymer by 13C NMR spectroscopy revealed highly linear
polyethylene (PE). Also visible in the polymer samples isolated
using 1/MAO and 2/MAO were signals for n-alkyl end-groups,
consistent with chain transfer to aluminum operating as the
predominant termination mechanism.
The zirconium catalyst 4/MAO was found to have exceptional
activity for ethylene polymerization with submicromolar quanti-
ties of catalyst required to prevent excessive exotherms and
polymer yields. At reduced precatalyst loadings the concentra-
tion of cocatalyst also had to be reduced to achieve optimal
activity. At a precatalyst loading of 40 nmol and employing
0.75mmolofMAO,anoptimizedactivityof49 000g/mmol · h · bar
was recorded over 60 min, with a molecular weight (Mn) of
16.6 kg/mol. Altering the phosphine substituents from phenyl
to isopropyl resulted in a dramatic lowering of the productivity
and a very broad molecular weight distribution. Although care
must be exercised when extrapolating metal–ligand geometries
from precatalysts to the active species, the differing configura-
tions of 4 (all-cis) and 5 (P-trans) may be responsible for this
clear change in performance. We shall return later to scrutinize
the nature of the active species derived from 4. The polyethylene
from both zirconium catalysts showed evidence for chain
transfer to aluminum in their 13C NMR spectra.
ring is flat (all five atoms coplanar to within ca. 0.03 Å), while
the P(1)/O(1) ring has an envelope conformation with the metal
lying ca. 0.36 Å out of the C2OP plane (which is coplanar to
within ca. 0.02 Å) in the direction of O(2).28 This planarity for
the P(2)/O(2) ring, and folding of the P(1)/O(1) ring, is also
seen in the structure of the hafnium analogue 6,25 where the
five atoms of the P(2)/O(2) ring are all coplanar to within ca.
0.03 Å, and the metal lies ca. 0.37 Å out of the C2O(1)P(1)
plane (which is coplanar to within ca. 0.02 Å) in the direction
of O(2).29 The most noticeable difference between complexes
3 and 4 (except the obvious presence of only one independent
molecule in the structure of 4) is in the pattern of bonding at
the metal center (Table 1). Although the bonds to phosphorus
and oxygen show the same pattern as in 3 [M-P(1) longer than
M-P(2), M-O(2) longer than M-O(1)], the two Zr-Cl bond
lengths are statistically identical [2.4239(6) and 2.4263(6) Å to
Cl(1) and Cl(2), respectively], whereas in 3 the Ti-Cl(2) bonds
were noticeably longer than those to Cl(1). This may in part be
a consequence of the Zr-Cl bonds being ca. 0.1 Å longer than
their Ti-Cl counterparts. This pattern of bond lengths is
repeated in the hafnium analogue 6 (Table 1).
The configurations of 1-6 in solution were determined by
1H and 31P NMR spectroscopy. All signals in the 31P spectra
were shifted substantially downfield (by 16–30 ppm) from the
value found for the corresponding sodium phosphanylphenoxide,
consistent with coordination of the phosphines to the metal
center.23b,d If, as seen in the solid state, the PPh2-substituted
complexes adopt a C1-symmetric, all-cis configuration, then two
sets of signals are expected for the inequivalent O,P ligands.
This should be conveniently observed in the 31P NMR spectra
with two doublets anticipated for the two coupled phosphorus
environments. However, only the spectrum of 3 gave this pattern
(2JPP ) 6.2 Hz); 31P NMR spectra of 1, 2, 4, and 6 all returned
single 31P resonances, apparently contradicting the crystal-
lographic data. Therefore, variable-temperature 31P NMR
experiments were performed. At low temperature the anticipated
set of doublets was observed for each complex, thus indicating
that a dynamic interchange of the all-cis enantiomers is occurring
at ambient temperature (Scheme 3).
To probe the mechanism of ligand exchange, kinetic param-
eters for the averaging process were calculated for 2-4 and 6
using line-shape analysis30 of the 31P NMR data measured over
(28) The molecular structure of 5, reported in ref 25, has folded C2OPZr
rings with the metal lying ca. 0.29 and ca. 0.36 Å out of the rest of the
chelate.
(29) The chlorine, phosphorus, and oxygen atoms of the coordination
sphere in 6 have been renumbered with respect to the report in ref 25 in
order to match the numbering of the atoms in the structures reported here.
Cl(1) and Cl(2) have swapped, as have P(1) and P(2), and O(1) and O(2).
(30) Reich, H. J. WINDNMR v7.1.6, 2002. For full kinetic data and
Eyring plots see the Supporting Information.
(31) Non-dissociative pathways have been proposed in other octahedral
bis-bidentate Group 4 metal complexes: (a) Fay, R. C.; Lindmark, A. F.
J. Am. Chem. Soc. 1983, 105, 2118. (b) Rahim, M.; Taylor, N. J.; Xin, S.;
Collins, S. Organometallics 1998, 17, 1315. (c) Kakaliou, L.; Scanlon, W. J.;
Qian, B.; Baek, S. W.; Smith, M. R.; Motry, D. H. Inorg. Chem. 1999, 38,
5964. (d) Otten, E.; Dijkstra, P.; Visser, C.; Meetsma, A.; Hessen, B.
Organometallics 2005, 24, 4374.
(32) (a) Bickley, D. G.; Serpone, N. Inorg. Chem. 1976, 15, 948. (b)
Bickley, D. G.; Serpone, N. Inorg. Chem. 1976, 15, 2577.
(33) Bailar, J. C. J. Inorg. Nucl. Chem. 1958, 8, 165.
(34) After all polymerizations the reaction medium was examined by
GC. No oligomeric products were detected in any instance.

Group 4 Metal Olefin Polymerization Catalysts
Organometallics, Vol. 27, No. 2, 2008 239
Figure 3. Selected variable-temperature 31P NMR spectra (toluene-d8) for 2-4 and 6 with associated exchange rates.
of the polymer revealed that termination occurs by chain transfer
to aluminum, which regenerates Hf-Me bonds and hence
further limits insertion. As aluminum methyls are steadily
consumed, the rate at which Hf-Me bonds are formed should
decrease, resulting in an increased ethylene uptake as the run
progresses.
Since chain transfer to aluminum appears to occur readily
for these catalysts, we decided to investigate 4 and 6 as
candidates for the catalyzed chain growth (CCG) of short chain
linear alkanes using ZnEt2 as the chain transfer agent.36
Polymerizations in the presence or absence of ZnEt2 are
collected in Table 4. For both catalysts introducing ZnEt2 to
the reaction mixture gave a significant decrease in molecular
weight and narrow molecular weight distributions (PDI 1.2–1.3)
consistent with efficient CCG. Also of note was the considerable
increase in the productivity of 6/MAO. This is consistent with
the previous assertion that insertion into Hf-Me bonds is rate-
limiting. In the presence of ZnEt2 rapid alkyl exchange generates
Hf-Et bonds into which ethylene readily inserts. Additional
CCG reactions in which samples were taken at intervals through
the run and the products analyzed by GC revealed Poisson
distributions of PE oligomers that increased in molecular weight
over time; selected distributions for 4 are shown in Figure 5
(all distributions can be found in the Supporting Information).
Figure 4. Nondissociative pathways for ligand exchange in
bis(phosphanylphenoxide)MCl2 complexes.
Table 2. Activation Parameters for the Ligand Exchange in 2-4
and 6 (toluene-d8 solvent)
Propylene Polymerization Studies. Complexes 4 and 6 also
showed significant productivities for the polymerization of
propylene using “dried”-MAO37 (DMAO) as the cocatalyst (see
Table 5). At 20 °C 4/DMAO gave a viscous oil of moderate
molecular weight and low PDI with a productivity of 5340
g/mmol · h · bar. Analysis of the polymer by 13C NMR spec-
troscopy (Figure 6) showed it to have a slight syndiotactic bias
([rr] ) 38.5%; cf. 25.0% for atactic polymer). Full pentad
complex (M, R) ∆Hq (kcal/mol) ∆Sq (cal/K · mol) ∆G‡
(kcal/mol)
298K
2 (Ti, Ph)
13.2(2)
12.3(2)
11.5(2)
10.8(1)
-0.6(5)
-12.6(5)
-3.4(6)
-8.3(5)
13.4(4)
t
3 (Ti, Bu)
16.1(3)
12.5(3)
13.3(3)
t
4 (Zr, Bu)
t
6 (Hf, Bu)
The hafnium catalyst 6/MAO also showed a marked sensitiv-
ity to the quantity of cocatalyst, with an optimized productivity
of 2000 g/mmol · h · bar. In all cases the polymer had a broad
multimodal molecular weight distribution. It is also of note that
polymerizations using 6/MAO were accompanied by significant
induction times, with the vast majority of the polymer being
formed in the final 30 min. Since aging a solution of 6/MAO
(100 equiv) for 30 min prior to injection into the polymerization
vessel did not improve the productivity, or reduce the induction
time, it is proposed that insertion into the initially formed
Hf-Me bonds is rate-limiting.35 Furthermore, 13C NMR analysis
(36) (a) Britovsek, G. J. P.; Cohen, S. A.; Gibson, V. C.; Maddox, P. J.;
van, Meurs Angew. Chem., Int. Ed. 2002, 41, 489. (b) Britovsek, G. J. P.;
Cohen, S. A.; Gibson, V. C.; van Meurs, M. J. Am. Chem. Soc. 2004, 126,
10701. (c) van Meurs, M.; Britovsek, G. J. P.; Gibson, V. C.; Cohen, S. A.
J. Am. Chem. Soc. 2005, 127, 9913. (d) Arriola, D. J.; Carnahan, E. M.;
Hustad, P. D.; Kuhlmann, R. L.; Wenzel, T. T. Science 2006, 312, 714. (e)
Kempe, R. Chem.-Eur. J. 2007, 13, 2764.
(37) DMAO is MAO with residual AlMe3 removed under vacuum (see
Supporting Information). DMAO has been shown to improve the perfor-
mance of several non-metallocene catalysts: (a) Hasan, T.; Ioku, A.; Nishii,
K.; Shiono, T.; Ikeda, T. Macromolecules 2001, 34, 3142. (b) Hagimoto,
H.; Shiono, T.; Ikeda, T. Macromol. Rapid Commun. 2002, 23, 73. (c)
Furayama, R.; Saito, J.; Ishii, S.; Mitani, M.; Matsui, S.; Tohi, Y.; Makio,
H.; Matsukawa, N.; Tanaka, H.; Fujita, T. J. Mol. Catal. A: Chem. 2003,
200, 31.
(35) (a) Wester, T. S.; Johnsen, H.; Kittilsen, P.; Rytter, E. Macromol.
Chem. Phys. 1998, 199, 1989. (b) Liu, Z.; Somsook, E.; White, C. B.;
Rosaaen, K. A.; Landis, C. R. J. Am. Chem. Soc. 2001, 123, 11193.

240 Organometallics, Vol. 27, No. 2, 2008
Long et al.
Table 3. Ethylene Polymerization Results for Complexes 1-6a
c
c
precatalyst (loading (µmol))
MAO loading (mmol)
yield PE (g)
activityb
Mn (kg/mol)
Mw (kg/mol)
Mw/Mn
1 (5.0)
2 (5.0)
3 (5.0)
4 (0.1)
4 (0.1)
4 (0.1)
4 (0.04)
5 (5.0)
6 (1.0)
6 (1.0)
6 (1.0)
2.50
2.50
2.50
2.50
1.25
0.75
0.75
2.50
2.50
1.25
0.75
0.41
6.15
3.90
2.24
5.34
5.00e
3.92
0.35
1.10
2.13
4.00
41
615
390
1.9
19.2
782
8.2
12.0
13.1
16.6
1.0
529
44.5
1,370
21.0
71.8
54.3
143
109
8.3
228
580
278d
2.3
1.8
2.6
6.0
4.1
11 200
26 700
100,000e
49 000
35
8.6
109f
8.3g
114h
88i
550
1070
2000
1.0
2.0
6.6
a Conditions: 400 mL glass reactor, mechanical stirring, toluene (200 mL), 2 bar ethylene, 25 °C, 1 h (except e). b Activities in g/mmol · h · bar.
c Determined by high-throughput GPC. i Trimodal: Mpk ) 1.7, 51.5, and 899 kg/mol. h Trimodal: Mpk ) 1.2, 18.6, and 562 kg/mol. d Multimodal: Mpk
1.5 kg/mol. e Run time 15 min. f Bimodal: Mpk ) 0.5 and 25.9 kg/mol. g Bimodal: Mpk ) 0.6 and 10.5 kg/mol.
)
Table 4. CCG on ZnEt2 Using 4 and 6a
activityb
Mn (g/mol)
Mwc(g/mol)
Mw/Mn
c
precatalyst (loading (µmol))
ZnEt2 loading (mmol)
yield (g)
4 (0.5)
4 (0.5)
6 (1.5)
6 (1.5)
0
4
0
4
1.05
1.25
0.17
3.75
25 200
30 000
461
2600
250
800
300
13 900
300
3000
400
5.3
1.2
3.8
1.3
10 000
a Conditions: Schlenk, magnetic stirring, MAO (1 mmol), toluene (100 mL), 1 bar ethylene, 25 °C, 5 min (4)/15 min (6). b Activities in
g/mmol · h · bar. c Determined by high-throughput GPC.
Consistent with the observations for ethylene polymerization,
6/DMAO (772 g/mmol · h · bar at 25 °C) gave a somewhat lower
productivity than 4/DMAO, but this could be increased, to 949
g/mmol · h · bar, by raising the polymerization temperature to
50 °C. Again the polymer was isolated as a viscous oil, with
NMR analysis revealing a reduced level of stereocontrol (Pr )
56.2% at 25 °C) and isobutyl end-groups.
Toward the Active Species. In order to rationalize the
stereoselectivity of 4/DMAO for propylene polymerization, more
information was required on the structure of the catalytically
active species. Treating ZrBn4 (Bn ) CH2Ph) with 2 equiv of
6-(tert-butyl)-2-diphenylphosphanylphenol, or reacting 4 with
2 equiv of BnMgBr, gave the dibenzyl complex 7 as an
analytically pure air- and moisture-sensitive yellow solid
(Scheme 5).
Figure 5. Oligomer distributions from 4/MAO with ZnEt2.
analysis38 indicates this selectivity is induced by chain-end
control, with the probability of a rac insertion (Pr) at 61.7%.
No chain end-groups were visible in the NMR spectrum of the
polymer. By lowering the polymerization temperature to -20
°C, and hence increasing the concentration of propylene in
solution, the activity of 4/DMAO was increased to 7010
g/mmol · h · bar. At -30 and -50 °C activities decreased,
indicating that insertion becomes rate-limiting. At lower tem-
peratures stereoselectivities did improve slightly; for example
at -50 °C Pr ) 65.9%. A polymerization in liquid propylene
at room temperature39 gave a productivity of 13 300 g/mmol · h,
which is among the highest reported productivities for a post-
metallocene propylene polymerization system. By using MAO
as the cocatalyst the molecular weight of the polymer could be
decreased such that isobutyl end-groups became visible in the
13C NMR spectrum.40 This not only indicates that chain transfer
to aluminum operates but that insertion occurs in a 1,2-fashion
(Scheme 4).
Recrystallization from heptane yielded crystals suitable for
an X-ray structure determination. The molecular structure
(Figure 7) revealed an geometry analogous to that found for its
dichloride relative 4, with the oxygen, phosphorus, and carbon
donor atoms all lying mutually cis. The geometry at the metal
center is a little more distorted from octahedral for 7, the
cis angles ranging between 65.70(8)° and 112.86(11)° (cf.
68.86(5)–103.30(2)° in 4) and the two most acute angles being
associated with the bites of the O,P ligands (Table 6). The P(2)/
O(2) five-membered C2OPZr chelate ring is again flat, all five
atoms being coplanar to within ca. 0.02 Å, while the P(1)/O(1)
ring has an envelope conformation, the metal lying ca. 0.53 Å
out of the C2OP plane (which is coplanar to within ca. 0.01 Å)
in the direction of O(2). Despite the change from chloride to
benzyl ligands, the pattern of Zr-P and Zr-O bonding is
similar, with Zr-P(1) longer than Zr-P(2) (carbon vs oxygen
in the trans position) and Zr-O(2) longer than Zr-O(1) (carbon
vs phosphorus in the trans position). For the two benzyl ligands,
Zr-C(8) (trans to oxygen) is longer than Zr-C(1) (trans to
phosphorus). There is no evidence of any multiple bonding
between the benzyl ligand and the metal center.
(38) Pentad intensities determined by line fitting using MestReC v4.7.0.0.
These were compared to best-fit chain-end and enantiomorphic site control
models. (a) Busico, V.; Cipullo, R. Prog. Polym. Sci. 2001, 26, 443. (b)
Bovey, F. A.; Tiers, G. V. D. J. Polym. Sci. 1960, 44, 173. (c) Shelden,
R. A.; Fueno, T.; Tsunetsugu, T.; Furukawa, J. J. Polym. Sci., Part B 1965,
3, 23.
The room-temperature solution-state NMR spectra of 7
revealed broad peaks for the benzyl and tert-butyl protons,
indicative of a complex with an intermediate rate of O,P ligand
exchange (Figure 8). Additionally, a sharp peak in the tert-butyl
region suggested that a more rigid geometric isomer might also
(39) Conditions: 1 L steel autoclave, mechanical stirring, 4 (1 µmol),
MAO (2.5 mmol), 500 mL of liquid propylene, 25 °C, 1 h.
(40) Polymerization conditions: as for Table 5 except MAO (5.0 mmol)
used as cocatalyst. See Supporting Information for 13C NMR spectrum.

Group 4 Metal Olefin Polymerization Catalysts
Organometallics, Vol. 27, No. 2, 2008 241
Table 5. Propylene Polymerizations Using 4 and 6a
c
precatalyst (loading (µmol))
temp (°C)
activityb
Mn (kg/mol)
Mwc(kg/mol)
Mw/Mn
[rr]d(%)
4 (2.5)
4 (2.5)
4 (2.5)
4 (2.5)
6 (10.0)
6 (10.0)
6 (10.0)
20
-20
-30
- 50e
50
5,340
7,010
4,500
1,750e
949
37.0
52.9
58.4
18.3
14.9
18.2
7.79
62.7
79.1
95.5
28.4
34.4
35.1
12.7
1.70
1.49
1.63
1.6
2.30
1.93
1.63
38.5
40.5
42.1
44.6
33.7
36.0
37.3
25
0
772
112
a Conditions: Schlenk, magnetic stirring, DMAO (2.5 mmol), TIBAL (125 µmol), heptane (100 mL) (except e), 2 bar propylene, 30 min (4)/1 h (6).
b Activities in g/mmol · h · bar (except e). c Determined by GPC. d Determined by 13C NMR (101 MHz). e Liquid propylene (100 ml); activity in
g/mmol · h.
Figure 6. 13C NMR (101 MHz, methyl region) of polypropylene
formed with 4/DMAO at 20 °C, with pentad analysis. aFrom line-
b
fitting analysis. Calculated for chain-end control (Pr ) 61.7%).
Scheme 4. Isobutyl-Terminated Polymer from 1,2-Propylene
Insertions and Chain Transfer to Aluminum
Figure 7. Molecular structure of 7.
Table 6. Selected Bond Lengths (Å) and Angles (deg) for 7
Zr-O(1)
1.981(3)
3.0194(11)
2.277(4)
Zr-O(2)
2.013(3)
2.8583(10)
2.310(4)
Zr-P(1)
Zr-P(2)
Zr-C(1)
Zr-C(8)
Scheme 5. Synthesis of
a
Bis(phosphanylphenoxide)
P(1)-Zr-C(1)
P(2)-Zr-O(1)
O(2)-Zr-C(8)
P(1)-Zr-P(2)
O(1)-Zr-O(2)
C(1)-Zr-C(8)
P(1)-Zr-O(2)
P(1)-Zr-C(8)
160.56(11)
149.73(8)
147.94(13)
85.47(3)
99.10(11)
100.73(17)
86.06(8)
P(2)-Zr-C(1)
P(2)-Zr-C(8)
O(1)-Zr-C(8)
O(1)-Zr-C(1)
O(2)-Zr-C(1)
P(1)-Zr-O(1)
P(2)-Zr-O(2)
112.86(11)
79.59(11)
107.34(14)
95.09(13)
94.55(14)
65.70(8)
Zirconium Dibenzyl Complex
68.49(7)
88.53(12)
be present. The room-temperature 31P NMR spectrum revealed
broad signals of approximately equal intensity at 2.3 and -9.3
ppm, consistent with inequivalent but exchanging phosphorus
environments in the all-cis structure. However, the spectrum
also included a very broad peak at 5 ppm and a sharper signal
at -14.6 ppm. It is proposed that these peaks are due to trans-
O2 and trans-P2 geometric isomers. To probe whether this
mixture could be converted to a single geometric product, a
sample of 7 in C6D6 was heated to 50 °C for 2 h. No change in
the isomer distribution was observed. It is also of note that the
ratio of the isomers was dependent on the synthetic route
employed, with a greater proportion of the all-cis isomer formed
using BnMgBr (ca. 80% compared to ca. 53% using ZrBn4).
Therefore, the observed distribution is not an interchanging
equilibrium mixture but rather represents a kinetic distribution
of products.
cantly alter upon cooling and is hence assigned to the trans-P2
isomer by comparison to the variable-temperature behavior of
1
5. The low-temperature H NMR spectrum of 7 includes five
distinct benzyl signals in the region 1.9–3.0 ppm. Four of these
are of equal intensity and are assigned to the four inequivalent
benzyl protons of the all-cis isomer.41 It was anticipated that
the benzyl protons of the trans-O2 and trans-P2 structures should
give at least two signals. Since only one benzyl signal (2.68
ppm) remains unassigned, it is proposed that these two isomers
have benzyl signals with coincidental chemical shifts. It should
be noted that the low-temperature 13C NMR spectrum contains
four signals for the benzylic carbons (64–74 ppm) and the
quaternary carbon of the tert-butyl groups (34–35 ppm),
consistent with there being one C1- and two C2-symmetric
isomers.
The activation parameters for O,P ligand exchange in the all-
cis isomer of 7 (∆Hq ) 10.5(3) kcal/mol, ∆Sq ) -10.4(9) cal/
On cooling to 223 K, the broad signal at 5 ppm in the 31P
NMR spectrum sharpened to a singlet. Additionally, the broad
signals assigned to the all-cis isomer resolved to two sharp
doublets (2JPP ) 21 Hz), consistent with a configurationally rigid
C1-symmetric complex. The high-field peak does not signifi-
(41) A COSY spectrum revealed cross-peaks for the peaks at 2.93 and
1.95 ppm and at 2.33 and 2.17 ppm, indicating that each pair is bound to
the same benzylic carbon.

242 Organometallics, Vol. 27, No. 2, 2008
Long et al.
1
Figure 9. Variable-temperature H and 31P NMR spectra of 8 in
C6D5Br. * ) residual toluene.
respectively, indicating that the cation is either highly fluxional
or adopts a square-based pyramidal structure with the benzyl
ligand in the apical position. At low temperature the H NMR
1
Figure 8. Variable-temperature 1H and 31P NMR spectra of 7 (from
ZrBn4) in CDCl3; * ) residual toluene; a ) trans-O2, b ) all-cis,
c ) trans-P2 geometric isomer.
spectrum significantly broadens and the 31P NMR spectrum
reveals two distinct, though broad, resonances indicative of a
C1-symmetric ground state akin to the parent six-coordinate
complex 7. To further probe the structure of 8, a small amount
of ether was added to the NMR sample. The room-temperature
31P NMR then contained two separate, equal intensity signals
at 8.3 and -2.1 ppm, consistent with a six-coordinate ether
complex in which trigonal face rotation is restricted by the
additional steric constraints imposed by binding of a molecule
of diethyl ether. Near-identical 19F NMR spectra were obtained
K · mol, ∆Gq
) 13.6(6) kcal/mol) were obtained using the
298K
same methodology as for the dichloro complexes.30 Again,
negative ∆Sq values are indicative of a nondissociative process.
Predictably, given the increased steric influence of the benzyl
ligands compared to chlorides, the rate of isomerization was
considerably slower than in 4 (approximately 7-fold at 298 K).
Of the reagents that can be used to abstract alkyl groups,
[Ph3C][B(C6F5)4] is particularly attractive since both the borate
anion and eliminated hydrocarbon are typically noncoordinating,
thus facilitating study of the base-free cation.42 Hence, 7 was
treated with 1 equiv of [Ph3C][B(C6F5)4] at room temperature
in an NMR-scale reaction in C6D5Br. Near-quantitative forma-
-
with or without ether coordination, consistent with B(C6F5)4
acting as a noncoordinating counterion.
An analogous cationic species 8′ could be obtained upon
treatment of 7 with 50 equiv of DMAO in C6D6 (Figure 10).
1
The H NMR spectrum clearly shows signals for an η2-bound
benzyl moiety, and the 31P NMR spectrum reveals a sharp
singlet almost identical to that seen for 8. Analogous NMR-
scale experiments were performed using the dichloride complex
1
tion of the cationic benzyl complex 8 was observed in the H
NMR spectrum (Figure 9), which included two equimolar
signals assignable to the CH2 groups of the zirconium-bonded
benzyl (2.84 ppm) and the eliminated 1,1,1,2-tetraphenylethane
(3.82 ppm). Also of note are the relatively high-field shifts for
the aromatic protons of the benzyl ligand (6.12–6.64 ppm),
suggesting η2-coordination. Further evidence for this bonding
mode was provided by a 1H-coupled 13C NMR spectrum, which
included a triplet at 79.3 ppm for the benzylic carbon with a
1JCH value of 148 Hz.43,44 Only one C(CH3)3 signal and one
phosphorus signal are observed in the 1H and 31P NMR spectra,
(43) Values above 130 Hz indicate some distortion of the benzyl ligand.
Examples of Zr complexes in which a solution state η2-interaction has been
confirmed by X-ray analysis include: (a) Tsurugi, H.; Matsuo, Y.; Yamsgata,
T.; Mashima, K. Organometallics 2004, 23, 2797. (b) Shao, P.; Gendron,
R. A. L.; Berg, D. J.; Bushnell, G. W. Organometallics 2000, 19, 509. (c)
Bei, X. H.; Swenson, D. C.; Jordan, R. F. Organometallics 1997, 16, 3282.
(d) Crowther, D. J.; Borkowsky, S. L.; Swenson, D.; Meyer, T. Y.; Jordan,
R. F. Organometallics 1993, 12, 2897. (e) Jordan, R. F.; Lapointe, R. E.;
Bajgur, C. S.; Echols, S. F.; Willett, R. J. Am. Chem. Soc. 1987, 109, 4111.
(f) Latesky, S. L.; McMullen, A. K.; Niccolai, G. P.; Rothwell, I. P.;
Huffman, J. C. Organometallics 1985, 4, 902.
(42) Coordination of solvent cannot typically be ruled out. A chloroben-
zene adduct of a zirconium benzyl cation has been structurally characterized:
Wu, F.; Dash, A. K.; Jordan, R. F. J. Am. Chem. Soc. 2004, 126, 15360.
(44) It has recently been suggested that in the absence of coordinated
solvent benzyl ligands may in fact bind in an η3 manner: Sassmannshausen,
J.; Track, A.; Stelzer, F. Organometallics 2006, 25, 4427.

Group 4 Metal Olefin Polymerization Catalysts
Organometallics, Vol. 27, No. 2, 2008 243
Table 7. Ethylene Polymerizations with 7a
d
d
temp
yield
Mn
Mw
cocatalystb (°C) PE (g) activityc (kg/mol) (kg/mol) Mw/Mn
TB
TB
MAO
25
50
25
0.00
1.56
2.79
0
3900
14 000
6.3
7.8
16.2
20.6
2.6
2.6
a Conditions: glass reactor, mechanical stirring, 7 (0.2 µmol), MAO
(2.5 mmol) or [Ph3C][B(C6F5)4] (0.2 µmol) and AliBu3 (0.5 mmol),
toluene (200 mL), 2 bar ethylene, 1 h (TB)/30 min (MAO). b TB )
[Ph3C][B(C6F5)4]. c Activities in g/mmol · h · bar. d Determined by GPC
vs PS standards.
polypropylene formed is virtually atactic. However, it should
be noted that there are fluxional zirconocenes that can form
isotactic-atactic stereoblock polymers.48 Furthermore, the
highly syndiotactic polymer generated using bis(phenoxy-
imine)titanium catalysts is thought to be a direct consequence
of an isomerization process that occurs after each monomer
insertion.49 For a fluxional catalyst to give stereoenriched PP
via an enantiomorphic site control mechanism, two requirements
must be met. First, the ground-state structure(s) must be able
to influence the orientation of the polymer chain in order to
control the mode of monomer insertion. Second, the rate of
geometrical isomerization must be comparable to, but preferably
less than, the rate of insertion. Assuming that the O,P ligand
framework in 4/DMAO can control monomer insertion, this
means the rate of ligand reorganization must be slower than
the rate of monomer insertion, which is calculated as 71 s-1 at
20 °C.50 A crude comparison with the ligand exchange rates
calculated for 4 and 7 (3400 and 596 s-1, respectively) indicates
that the fluxional processes in 4/DMAO are too rapid for any
stereocontrol to be imparted.
1
Figure 10. H and 31P NMR spectra of 8′ (7 + DMAO) in C6D6
(*). † ) residual heptane in DMAO.
Figure 11. 31P NMR spectra of 4 + DMAO in C6D6.
4 with differing amounts of DMAO. The 31P NMR spectra
reveal a low-intensity sharp signal and a larger broad peak
(Figure 11). The low-intensity signal is tentatively assigned to
a (O,P)2Zr(Me)Cl complex and the broad peak to (O,P)2Zr+Me.
In the absence of the additional alkyl-metal interactions seen
for 8/8′ it is proposed that the aluminoxane anion can reversibly
access the zirconium center. Such dynamic interactions, and the
nonuniform nature of aluminoxanes, can hence explain the
observed broadening.45 Increasing the concentration of DMAO
increases both the yield of the cationic species and the likelihood
of cation–anion interactions.
Conclusions
A number of bis(phosphanylphenoxide) group 4 metal
complexes have been synthesized in order to assess the effect
of incorporating phosphine donors into early transition metal
based olefin polymerization catalysts. The geometries of these
complexes are dependent upon the phosphine substituents, with
diisopropyl- and diphenyl-phosphine zirconium derivatives
possessing trans-P2 and all-cis structures, respectively.
Polymerization studies have highlighted a tert-butyl-substi-
tuted zirconium catalyst that shows excellent activity in the
production of polyethylene and polypropylene. In fact this
catalyst is one of the most active post-metallocene catalysts
reported to date, suggesting that there is considerable scope for
utilizing the combination of hard donors with soft phosphine
donors in early transition metal polymerization catalysis. It can
be expected that linking the O,P ligands to one another might
increase the configurational stability of the catalyst, which may
thenofferthepossibilityforstereoselectiveR-olefinpolymerizations.
Interestingly, when
a solution of 8 (formed using
[Ph3C][B(C6F5)4]) was placed under an atmosphere of ethylene,
the yellow color was retained46 and no polymer was formed,
suggesting that the η2-benzyl interaction is too strong to be
displaced by ethylene.47 This was reproduced under polymer-
ization conditions (Table 7) with no polymer formed at 25 °C.
However, running the polymerization at 50 °C did give polymer,
suggesting that an η2-η1 rearrangement may occur at elevated
temperature. Furthermore, polymer could be formed at room
temperature using MAO as the cocatalyst, with a steady increase
in ethylene uptake measured throughout the run. This suggests
gradual exchange of the η2-benzyl ligands for methyls by the
AlMe3 present in the cocatalyst.
Experimental Methods
The synthesis of the phosphanylphenols, phosphanylphenoxides,
and complexes 1-6 has been reported elsewhere.25 ZrBn4 was
synthesized according to a published procedure.51 Air-sensitive
procedures were performed under nitrogen using standard Schlenk
techniques, with solvents being distilled over standard drying agents
Given the fluxional nature of the catalytically active species
derived from 4 or 7 it is perhaps less surprising that the
(48) Lin, S.; Waymouth, R. M. Acc. Chem. Res. 2002, 35, 765.
(49) Miliano, G.; Cavallo, L.; Guerra, G. J. Am. Chem. Soc. 2002, 124,
13368.
(45) Hawrelak, E. J.; Deck, P. A. Organometallics 2003, 22, 3558.
(46) Kress et al. have observed a single ethylene insertion, indicated by
a lack of polymer coupled with a loss of color: Gauvin, R. M.; Osborn,
J. A.; Kress, J. Organometallics 2000, 19, 2944.
(50) Insertion rate (s-1) ) polymer yield (g)/[fw(propylene) (g/mol) ×
cat. loading (mol) × run time (s)].
(47) Bochmann, M.; Lancaster, S. J. Organometallics 1993, 12, 633.
(51) Felten, J. J.; Anderson, W. P. J. Organomet. Chem. 1972, 36, 87.

244 Organometallics, Vol. 27, No. 2, 2008
Long et al.
and degassed before use. Deuterated solvents were dried and stored
over 4 Å molecular sieves. Ethylene (CP grade) and propylene
(instrument grade) were purified by passing them through an Oxy-
trap and a gas drier (Alltech Associates). Compounds were analyzed
by NMR: Bruker AC-250, Bruker DRX-400, or Bruker Avance-
600 spectrometers (referenced to solvent resonances for 1H and
13C NMR, and externally to 85% H3PO4(aq) and CFCl3 for 31P and
19F NMR, respectively). IR: Perkin-Elmer 1760X FT-IR. Mass
spectrometry: Autospec Q spectrometer. Elemental analyses were
performed at London Metropolitan University. Polymer samples
were analyzed by 13C NMR: Bruker Avance-400 spectrometer (in
2:1 (by weight) 1,2,4-C6H3Cl3:1,1,2,2-C2D2Cl4 at 130 °C using a
pulse delay of 15 s). GPC (polyethylene): Polymer Laboratories
GPC-220 with PLgel HTS-B column (1,2,4-trichlorotoluene, 160
°C, run time ) 6 min, PS standards). GPC (polypropylene): Polymer
Laboratories LC1220 HPLC pump with two 5 µm (PL gel mixed
C 300 × 7.5 mm) columns (CHCl3, 25 °C, run time ) 30 min, PS
standards).
K): δ 7.70 (t, J ) 8.3 Hz, Ar-H), 7.38–6.61 (br m, Ar-H), 3.00–1.80
(br, 4H(a) + 4H(b) + 4H(c), C H2Ph), 1.50–0.80 (br, 18H(a) +
18H(b), C(C H3)3), 0.94 (s, 18H(c), C(C H3)3). 1H NMR (400 MHz,
CDCl3, 223 K): δ 7.74 (t, J ) 7.8 Hz, Ar-H), 7.43–7.12 (m, Ar-
H), 7.02–6.68 (m, Ar-H), 6.64–6.50 (m, Ar-H), 6.21 (t, J ) 8.1
Hz, Ar-H), 2.96–2.90 (m, 1H(b), C H2Ph), 2.71–2.64 (m, 4H(a) +
4H(c), C H2Ph), 2.33 (d, 2JHH ) 10.8 Hz, 1H(b), C H2Ph), 2.17 (d,
2JHH ) 10.8 Hz, 1H(b), C H2Ph), 1.97–1.92 (m, 1H(b), C H2Ph),
1.34 (s, 9H(a/b), C(C H3)3), 1.04 (s, 9H(a/b), C(C H3)3), 0.87 (s,
18H(a/b) + 18H(c), C(C H3)3). 13C{1H} NMR (101 MHz, CDCl3,
223 K): δ 169.1, 169.0, 168.9, 168.7, 166.4, 166.1, 147.6, 147.5,
146.0, 145.8, 137.8, 137.3, 137.2, 137.2, 137.1, 134.0, 133.6, 133.6,
133.5, 133.5, 133.3, 133.1, 133.1, 132.8, 132.7, 132.2, 132.1, 131.9,
131.8, 131.6, 131.5, 131.3, 131.2, 131.1, 131.0, 130.8, 130.5, 130.1,
129.9, 129.9, 129.8, 129.4, 129.3, 129.2, 129.0, 128.9, 128.7, 128.4,
128.2, 128.0, 127.9, 127.7, 127.2, 125.5, 125.5, 125.2, 123.7, 123.5,
121.3, 120.7, 120.5, 120.2, 119.7, 119.7, 119.6, 119.4, 119.3, 118.3
(Ar-C), 73.9, 73.7, 69.6, 63.5 (CH2Ph), 34.8, 34.7, 34.4, 34.0
(C(CH3)3), 29.2, 28.8, 28.3 (C(CH3)3). 31P{1H} NMR (162 MHz,
CDCl3, 298 K): δ 5.3–2.4 (br, 2P(a) + 1P(b) [49%]), -9.5 (br,
1P(b) [33%]), -15.3 (s, 2P(c) [18%]). 31P{1H} NMR (162 MHz,
CDCl3, 223 K): δ 5.3 (s 2P(a) [35%]), 2.0 (d, 2JPP ) 21 Hz, 1P(b)
The numbering scheme below is used in the assignments of the
O,P precursors and complexes:
2
[27%]), -9.8 (d, JPP ) 21 Hz, 1P(b) [27%]), -16.2 (s, 2P(c)
[11%]).
Method 2: To a solution of 4 (0.301 g, 0.36 mmol) in toluene
(30 mL) cooled to -78 °C was added dropwise PhCH2MgBr (1.24
M in THF; 0.60 mL, 0.74 mmol), giving immediate formation of
a yellow solution. The mixture was allowed to warm to room
temperature over 12 h, over which time a colorless precipitate was
formed. The suspension was filtered through Celite and the solvent
then removed under vacuum. The residual yellow oil was triturated
with pentane and the resultant precipitate filtered and dried under
vacuum to give 7 as a yellow powder (0.181 g, 0.19 mmol, 53%
yield). Anal. Calcd (%) for C58H58O2P2Zr (940.25): C, 74.09; H,
6.21. Found: C, 73.95; H, 6.10. 31P{1H} NMR (101 MHz, CDCl3,
298 K): δ 2.3 (br, 2P(a) + 1P(b) [60%]), -9.2 (br, 1P(b) [40%]),
-15.2 (s, 2P(c) [<1%]).
Synthesis of A. To a solution of 1-tert-butyl-2-(methoxymethox-
y)benzene (14.55 g, 75.0 mmol) in ether (150 mL) was added
n-butyllithium (30.6 mL, 76.5 mmol), and the mixture was stirred
for 12 h. Chlorodiphenylphosphine (14.15 mL, 78.8 mmol) was
added to the mixture dropwise at -78 °C. The mixture was stirred
at room temperature for 3 h and then filtered. The filtrate was
concentrated to dryness and the residue dissolved in THF (75 mL)
and 5 M HCl (75 mL). The mixture was stirred and heated at 50
°C for 12 h. The mixture was poured into water (500 mL), filtered,
and washed with water (3 × 100 mL). The crude product was
triturated in methanol, filtered, and dried under vacuum to give a
colorless powder (16.69 g, 41.6 mmol, 56% yield). Anal. Calcd
(%) for C23H26ClO2P (400.88): C, 68.91; H, 6.54. Found: C, 68.87;
Synthesis of 8. In a nitrogen filled glovebox, a C6D5Br solution
of [CPh3][B(C6F5)4] (1 equiv) was added to a C6D5Br solution of
7 (1 equiv) at 25 °C. The orange solution was transferred to an
NMR tube fitted with a Youngs tap valve. The NMR data was
acquired immediately. 1H NMR (250 MHz, C6D5Br, 298 K): δ 7.34
1
H, 6.49. H NMR (400 MHz, CDCl3): δ 9.40 (br, 1H, Ar-O H),
7.74–7.70 (m, 3H, Ar-H(4,D)), 7.58–7.53 (m, 8H, Ar-H(B,C)), 7.29
(br, 1H, CH2O H), 7.02 (dt, J ) 7.7 Hz, J ) 3.6 Hz, 1H, Ar-H(5)),
3
2
(dd, JHH ) 7.4 Hz, JHH ) 1.6 Hz, 2H, Ar-H), 7.28–6.98 (m, 34
H, Ar-H), 6.93–6.82 (m, 8H + 2H, Ar-H + Ar-H(γ)), 6.62 (d, J )
7.8 Hz, 2H, Ar-H), 6.28 (d, 3JHH ) 7.5 Hz, Ar-H(ꢀ)), 6.12 (t, 3JHH
) 7.3 Hz, Ar-H(δ)), 3.81 (s, 2H, Ph3CC H2Ph), 2.83 (s, 2H, ZrC
H2Ph), 1.22 (s, 18H, C(C H3)3). 1H NMR (400 MHz, C6D5Br, 248
K): δ 7.50–6.40 (br m, 48H, Ar-H), 6.24 (br s, Ar-H(ꢀ)), 5.94 (br
3
3
4
6.59 (ddd, JHP ) 13.9 Hz, JHH ) 6.9 Hz, JHH ) 1.4 Hz, 1H,
Ar-H(6)), 5.43 (s, 2H, C H2OH), 1.47 (s, 9H, C(C H3)3). 13C{1H}
NMR (101 MHz, CDCl3): δ 159.5 (d, 2JCP ) 3.0 Hz, Ar-C(2)), 144.7
(d, 3JCP ) 6.6 Hz, Ar-C(3)), 135.3 (Ar-C(4)), 134.5 (Ar-C(D)), 133.8
(d, 2JCP ) 9.2 Hz, Ar-C(6)), 133.2 (d, 3JCP ) 9.4 Hz, Ar-C(C)), 130.0
3
t, JHH ) 7.5 Hz, Ar-H(δ)), 3.78 (s, 2H, Ph3CC H2Ph), 2.84 (br s,
2
3
(d, JCP ) 12.0 Hz, Ar-C(B)), 123.6 (d, JCP ) 13.9 Hz, Ar-C(5)),
2H, ZrC H2Ph), 1.21 (s, 18H, C(C H3)3). 13C NMR (63 MHz,
C6D5Br, 298 K): selected δ 165.3 (br, Ar-C(1)), 150.6 (s, Ar-C(R)),
1
1
119.3 (d, JCP ) 82.7 Hz, Ar-C(A)), 109.6 (d, JCP ) 89.4 Hz, Ar-
1
C(1)), 61.0 (d, JCP ) 62.6 Hz, P CH2OH), 35.3 (C(CH3)3), 30.4
1
79.3 (t, JCH ) 148 Hz, Zr CH2Ph), 35.2 (s, C(CH3)3), 29.7 (q,
(C(CH3)3). 31P{1H} NMR (162 MHz, CDCl3): δ 20.9 (s). MS
(negative FAB; m/z): 399 [M]-, 333 [M - Cl - CH2OH]-, 188
1JCH ) 123 Hz, C(CH3)3). 31P{1H} NMR (101 MHz, C6D5Br, 298
K): δ 9.4 (s). 31P{1H} NMR (162 MHz, C6D5Br, 248 K): δ 8.4 +
7.9 (2 unresolved br s). 19F{1H} NMR (235 MHz, C6D5Br, 298
[M - Bu-2Ph]-. IR (KBr; cm-1): 3142 (OH), 2868br (OH).
t
Crystals suitable for X-ray analyses were grown from a chloroform
solution layered with pentane.
3
K): δ -135.9 (s, o-BC6F5), -166.4 (t, JFF ) 21.2 Hz, p-BC6F5),
-170.2 (pt, JFF ) 18.5 Hz, m-BC6F5).
Synthesis of 7. Method 1: A solution of ZrBn4 (0.312 g, 0.68
mmol) in toluene (20 mL) was cooled to -10 °C and a solution of
2-tert-butyl-6-diphenylphosphanylphenol (0.477 g, 1.43 mmol) in
toluene (20 mL) added dropwise. The mixture was stirred for 30
min at -10 °C and for 30 min at 25 °C. The solvent was removed
under vacuum and the residue triturated with pentane (5 mL),
filtered, and dried under vacuum to give 7 as a yellow powder
(0.547 g, 0.58 mmol, 85% yield). Anal. Calcd (%) for C58H58O2P2Zr
(940.25): C, 74.09; H, 6.21. Found: C, 73.82; H, 6.10. Three
different isomers were detected by NMR analysis: trans-O2 (isomer
The reaction was repeated and two drops of dry Et2O added to
the solution. The NMR data were acquired immediately. 1H NMR
3
(250 MHz, C6D5Br, 298 K): selected δ 7.59 (d, JHH ) 7.5 Hz,
2H, Ar-H), 7.18–6.40 (br m, 49 H, Ar-H), 2.50 (br s, 2H, ZrC
H2Ph). 31P{1H} NMR (101 MHz, C6D5Br, 298 K): δ 8.3 (br s),
-2.1 (br s). 19F{1H} NMR (235 MHz, C6D5Br, 298 K): δ -136.0
3
(s, o-BC6F5), -166.6 (t, JFF ) 21.0 Hz, p-BC6F5), -170.4 (pt,
JFF ) 18.4 Hz, m-BC6F5).
Reaction of 7 with DMAO. In a nitrogen-filled glovebox, a C6D6
solution of DMAO (50 equiv) was added to a C6D6 solution of 7
1
a), all-cis (b), and trans-P2 (c). H NMR (400 MHz, CDCl3, 298

Group 4 Metal Olefin Polymerization Catalysts
Organometallics, Vol. 27, No. 2, 2008 245
(1 equiv) at 25 °C. After 20 min, the pale yellow solution was
transferred to an NMR tube fitted with a Youngs tap valve, and
NMR data were acquired. 1H NMR (250 MHz, C6D6): δ 7.41–6.70
(dd + br m, JHH ) 6.9 Hz, JHH ) 2.1 Hz, 33H, Ar-H), 6.26 (d,
3JHH ) 7.8 Hz, 2H, Ar-H(ꢀ)), 6.14 (t, 3JHH ) 6.7 Hz, 1H, Ar-H(δ)),
3.24 (br, 2H, DMAO-C H2Ph), 2.80 (s, 2H, Zr-C H2Ph), 1.30 (s,
18H, C(C H3)3), 0.5 > 23>(-1.0) (br m, Al-C H3). 31P{1H} NMR
(101 MHz, C6D6): δ 9.4 (s).
Propylene Polymerization Procedures. Method 1 (-30 to 50
°C): A Schlenk, containing 100 mL of heptane, DMAO, and a
magnetic stirrer under a nitrogen atmosphere, fitted with a rubber
septum was purged under 1 bar of propylene overpressure for 5
min (to give 2 bar total propylene pressure). AliBu3 was added as
a scavenger and the temperature of the vessel adjusted as required,
allowing 20 min for the solvent to saturate with propylene. A
toluene solution of precatalyst treated with 100 equiv of DMAO
was introduced via syringe to initiate the polymerization. The
reaction mixture was rapidly stirred throughout. Polymerizations
were terminated by venting the overpressure followed by addition
of 5 mL of 2 M HCl(aq). After warming to room temperature, a
further 50 mL of 2 M HCl(aq) was added, and the layers were
separated. The organic fraction was washed with 2 M HCl(aq) (50
mL) and water (50 mL), dried (MgSO4), and filtered. The solvent
was removed under vacuum and the polymer dried under high
vacuum for 12 h.
3
4
Ethylene Polymerization Procedure. A 400 mL glass Fisher-
Porter vessel was dried at 50 °C for 12 h. The Fisher-Porter head,
equipped with an injection port (fitted with a rubber septum),
pressure gauge, and mechanical stirrer, was flame-dried for 5 min
and fitted to the glass vessel. The reactor was then purged with
nitrogen for 45 min, charged with solvent, purged with 1 bar of
ethylene overpressure for 5 min (to give 2 bar total ethylene
pressure), and placed in a room-temperature water bath. Scavenger
(MAO or AliBu3) was introduced at least 5 min before catalyst
injection. A solution of precatalyst (for polymerizations using MAO)
or activated catalyst (for polymerizations using [CPh3][B(C6F5)4])
in toluene was introduced via syringe to initiate the polymerization.
The reaction mixture was rapidly stirred throughout. Polymeriza-
tions were terminated by venting the overpressure followed by
addition of 5 mL of 2 M HCl(aq). A sample of the reaction mixture
was taken for GC analysis. The solid product was precipitated from
the mixture by addition of MeOH (400 mL). After filtration the
polymer was washed with a large quantity of MeOH and dried under
vacuum at 60 °C for 12 h.
Catalyzed Chain Growth Procedure. A Schlenk, containing
100 mL of toluene and a magnetic stirrer under a nitrogen
atmosphere, fitted with a rubber septum was purged with ethylene
for 5 min and the overpressure then vented (1 bar total ethylene
pressure). MAO and, when required, ZnEt2 were then added. If
GC samples were to be taken during the run, then a known quantity
of 2,2,4,4,6,8,8-heptamethylnonane was added as the GC standard.
The catalyst was introduced via syringe. Reactions were terminated
and worked up in the same manner as for the ethylene polymeriza-
tions above.
Method 2 (-50 °C): The vessel was prepared as in method 1,
except no solvent was added, and then placed in a cold bath at
-50 °C. When 100 mL of propylene had condensed, the Schlenk
was isolated from the propylene feed. A toluene solution of
precatalyst treated with 100 equiv of DMAO was introduced via
syringe to initiate the polymerization. The reaction mixture was
rapidly stirred throughout. Polymerizations were terminated by
addition of 5 mL of 2 M HCl(aq). The vessel was SLOWLY vented
and warmed to room temperature. The polymer was isolated as for
method 1.
Acknowledgment. BP Chemicals and, subsequently, In-
novene and Ineos are thanked for financial support of this
work.
Supporting Information Available: Crystallographic details,
VT-NMR spectra, kinetic data, polymer NMRs, and GC results.
OM7008149