Zirconium complexes containing tetradentate O,P,P,O ligands: Ethylene and propylene polymerization studies

Article abstract of DOI:10.1021/om800652w

The synthesis of a series of zirconium complexes bearing a linear diphosphanyl-bisphenoxide O,P,P,O ligand is described. The diphosphanyl- bisphenol proligand was prepared from Ph(Cl)PC₂H₄P(Cl)Ph as a 1:1 mixture of rac and meso diastereomers, which could be separated as a result of their differing solubilities in methanol. A relatively low barrier to phosphine inversion (ΔG^?_373K = 28.02(3) kcal/mol) allows interconversion of the two isomers. The zirconium dichloride complex of each diastereomer was prepared via treatment of ZrCl ₄(THF)₂ with the sodium (rac) or lithium (meso) salt of the respective bisphenol. Crystallographic and NMR analyses revealed a cis-α structure for the complex bearing the rac-O,P,P,O ligand and a seven-coordinate quasi-cis-β structure for the complex derived from the meso-O,P,P,O ligand. Dibenzyl complexes were synthesized by treatment of Zr(CH₂Ph)₄ with the rac and meso bisphenols; NMR evidence revealed cis-α and fluxional cis-β structures, respectively. Reactions of the dibenzyl complexes with [CPh₃][B(C₆F ₅)₄] afforded cationic alkyl derivatives in which the pre-existing ligand geometries were maintained. Ethylene polymerization studies afforded productivities up to 5450 and 116 g/mmol · h · bar for the cis-α and cis-β complexes, respectively, when using [CPh ₃][B(C₆F₅)₄]/Al(ⁱBu) ₃ as the activator. Under a propylene atmosphere, oligomeric products were obtained with low to moderate productivities.

Full text of DOI:10.1021/om800652w

5960
Organometallics 2008, 27, 5960–5967
Zirconium Complexes Containing Tetradentate O,P,P,O Ligands:
Ethylene and Propylene Polymerization Studies
Richard J. Long, David J. Jones, Vernon C. Gibson,* and Andrew J. P. White
Department of Chemistry, Imperial College London, Exhibition Road, London, U.K., SW7 2AZ
ReceiVed July 10, 2008
The synthesis of a series of zirconium complexes bearing a linear diphosphanyl-bisphenoxide O,P,P,O
ligand is described. The diphosphanyl-bisphenol proligand was prepared from Ph(Cl)PC2H4P(Cl)Ph as a
1:1 mixture of rac and meso diastereomers, which could be separated as a result of their differing solubilities
in methanol. A relatively low barrier to phosphine inversion (∆Gq
) 28.02(3) kcal/mol) allows
373K
interconversion of the two isomers. The zirconium dichloride complex of each diastereomer was prepared
via treatment of ZrCl4(THF)2 with the sodium (rac) or lithium (meso) salt of the respective bisphenol.
Crystallographic and NMR analyses revealed a cis-R structure for the complex bearing the rac-O,P,P,O
ligand and a seven-coordinate quasi-cis-ꢀ structure for the complex derived from the meso-O,P,P,O ligand.
Dibenzyl complexes were synthesized by treatment of Zr(CH2Ph)4 with the rac and meso bisphenols;
NMR evidence revealed cis-R and fluxional cis-ꢀ structures, respectively. Reactions of the dibenzyl
complexes with [CPh3][B(C6F5)4] afforded cationic alkyl derivatives in which the pre-existing ligand
geometries were maintained. Ethylene polymerization studies afforded productivities up to 5450 and
116 g/mmol · h · bar for the cis-R and cis-ꢀ complexes, respectively, when using [CPh3][B(C6F5)4]/Al(iBu)3
as the activator. Under a propylene atmosphere, oligomeric products were obtained with low to moderate
productivities.
Introduction
C2-Symmetric ansa-metallocenes are capable of generating
highly isotactic polyolefins. This is, in part, due to the rigid
coordination sphere enforced by the bridge between the two
cyclopentadienyl rings, which helps to maintain the catalyst
geometry throughout the growth of a polymer chain. In the
continuing search for new catalysts, linear tetradentate ligands
offer a feasible alternative to cyclopentadienyl ligands, as they
are capable of generating rigid chirality at a metal center1 and
hence have potential for stereoselective olefin enchainment. That
said, there are still a number of structural isomers that can form,
as shown in Figure 1. The binding mode depends inter alia
upon the nature of the donors, the size of the metal ion, the
nature of the interdonor linkages, and the spatial requirements
of the ligand framework.
Bis-aryloxide ligands, with or without additional neutral
donors, are well suited to group 4 metal catalysts and have been
studied extensively.2 Diimino-bisphenoxide, or salen-type,
complexes typically give trans structures, although cis configu-
rations can be accessed using less flexible N,N linkages.3 Their
saturated analogues, or salan-type ligands, are more flexible,
and group 4 metal complexes have been shown to adopt the
cis-R configuration.4,5 A (Bn ) CH2Ph) is an example of the
latter case and has been shown to give isotactic poly(R-olefins).
Figure 1. Structural isomers in octahedral complexes containing a
linear tetradentate ligand.
R′ ) H, B ) C2H4) has been shown to possess a cis-ꢀ
structure.6a However, ligand substituents can switch the coor-
dination mode to cis-R, although ∆-Λ interconversion can
occur for all but the bulkiest complexes (R ) tBu, cumyl).5b-5m
These complexes are active for the isospecific polymerization
of styrenes. It is of note that when B ) C3H6 the coordination
mode switches back to cis-ꢀ. Analogous diether-bisphenoxide
complexes have not been extensively studied.6a However, a
patent disclosure by Symyx Technologies reports that bridged
biaryl O,O,O,O hafnium complexes C are capable of showing
high isoselectivity for propylene polymerization, even at elevated
temperature.7
(3) (a) Biradar, N. S.; Kulkarni, V. H. J. Inorg. Nucl. Chem. 1971, 33,
3847. (b) Woodman, P. R.; Hitchcock, P. B.; Scott, P. Chem. Commun.
1996, 2735. (c) Bowden, F. L.; Ferguson, D. J. Chem. Soc., Dalton Trans.
1974, 460. (d) Coles, S. J.; Hursthouse, M. B.; Kelly, D. G.; Toner, A. J.;
Walker, N. M. J. Chem. Soc., Dalton Trans. 1998, 3489. (e) Corden, J. P.;
Errington, W.; Moore, P.; Wallbridge, M. G. H. Chem. Commun. 1999,
323. (f) Woodman, P. R.; Munslow, I. J.; Hitchcock, P. B.; Scott, P. J. Chem.
Soc., Dalton Trans. 1999, 4069. (g) Choudhary, N. F.; Hitchcock, P. B.;
Leigh, G. J. Inorg. Chim. Acta 2000, 306, 24. (h) Woodman, P. R.; Alcock,
N. W.; Munslow, I. J.; Sanders, C. J.; Scott, P. J. Chem. Soc., Dalton Trans.
2000, 3340. (i) Knight, P. D.; O’Shaughnessy, P. N.; Munslow, I. J.;
Kimberley, B. S.; Scott, P. J. Organomet. Chem. 2003, 683, 103. (j) Cuomo,
C.; Strianese, M.; Cuenca, T.; Sanz, M.; Grassi, A. Macromolecules 2004,
37, 7469. (k) Katsuki, T. Chem. Soc. ReV. 2004, 33, 437. (l) Lamberti, M.;
Consolmagno, M.; Mazzeo, M.; Pellecchia, C. Macromol. Rapid Commun.
2005, 26, 1866. (m) 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.
Nitrogen donors have been replaced by alternative hetereoa-
toms. The titanium dithioether-bisphenoxide complex B (R )
* To whom correspondence should be addressed. E-mail: v.gibson@
imperial.ac.uk.
(1) Knight, P. D.; Scott, P. Coord. Chem. ReV. 2003, 242, 125.
(2) For review articles see: (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.
10.1021/om800652w CCC: $40.75
2008 American Chemical Society
Publication on Web 10/15/2008

Zr Complexes Containing Tetradentate O,P,P,O Ligands
Organometallics, Vol. 27, No. 22, 2008 5961
Scheme 1. Synthesis of a Diphosphanyl-bisphenol
We have recently reported the synthesis and characterization
of a series of group 4 metal complexes containing two bidentate
O,P phosphanylphenoxide ligands and evaluated their capacity
for olefin polymerization.8 Of special note was a tert-butyl-
substituted zirconium derivative, which gave excellent produc-
tivities for propylene polymerization, but essentially atactic
polymer. NMR studies on cationic alkyl derivatives indicated
that the active species is highly fluxional. Therefore, in order
to enhance the potential for stereoselective insertion chemistry,
we decided to target tetradentate ligands in which the O,P units
are linked by an alkylene backbone. It was anticipated that the
greater rigidity of the tetradentate ligand frame might allow a
well-defined coordination environment to be maintained through-
out the polymerization process.
and an ethylene bridge between the phosphines.9 The synthetic
pathway involved treating commercially available Ph2PC2H4-
PPh2 with an excess of lithium to give [PhPC2H4PPh]2-Li+
-
2
(THF)4,10 which was then treated with PCl3 at -78 °C to give
Ph(Cl)PC2H4P(Cl)Ph as a white solid.11,12 Reaction of the latter
with ortho-lithiated MOM-protected 2-tert-butylphenol gave the
MOM-protected bisphenol in situ. Deprotection using AcOH/
H2O, followed by treatment with ammonia, afforded the desired
diphosphanyl-bisphenol as a 1:1 mixture of rac and meso
isomers (31P(CDCl3) -43.3 and -43.5 ppm, respectively).
Conveniently, the two diastereomers could be separated by their
differing solubilities in methanol. The insoluble product was
assigned as the meso isomer by X-ray crystallography (see
Supporting Information).
Results and Discussion
Ligand Synthesis. The targeted diphosphanyl-bisphenol 1
(see Scheme 1) included tert-butyl groups ortho to the phenols
(4) (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. (h) Yeori, A.; Goldberg, I.; Kol, M.
Macromolecules 2007, 40, 8521. (i) Segal, S.; Yeori, A.; Shuster, M.;
Rosenberg, Y.; Kol, M. Macromolecules 2008, 41, 1612. (j) Gendler, S.;
Zelikoff, A. L.; Kopilov, J.; Goldberg, I.; Kol, M. J. Am. Chem. Soc. 2008,
130, 2144.
Since the maximum yield of either isomer using this route
was limited to 50%, the temperature required to induce inversion
at phosphorus, and hence interconversion of the isomers, was
probed by heating a solution of meso-1 in toluene/C6D6 (5:1)
to 100 °C. After heating for 45 min a near 1:1 mixture of
diastereomers was observed, indicating a relatively facile
inversion of the phosphorus centers. Repeating the process over
shorter time intervals gave a rate of inversion, kinv, at 100 °C
of 2.98(11) × 10-4 s-1, corresponding to a Gibbs free energy
of activation (∆Gq373K) of 28.02(3) kcal/mol, which is somewhat
lower than in other biaryl-alkyl-phosphines (typically 29.1-30.8
kcal/mol at 403 K).13 The fortuitous consequence of this
accessible barrier is that, following isomer separation, the
unwanted isomer can be recycled to a diastereotopic mixture,
allowing further batches of the desired isomer to be isolated.
Complex Synthesis. The zirconium dichloride complex 2 was
synthesized by treating rac-1 with an excess of NaH followed
by ZrCl4(THF)2 (Scheme 2). The disodium salt of meso-1 was
insoluble in THF; hence its zirconium complex 3 was synthe-
(5) Hybrid imino-amino-bisphenxoide Ti and Zr complexes have been
reported with a cis-ꢀ structure: Yeori, A.; Gendler, S.; Groysman, S.;
Goldberg, I.; Kol, M. Inorg. Chem. Commun. 2004, 7, 280.
(6) (a) Snell, A.; Kehr, G.; Wibbeling, B.; Fro¨hlich, R.; Erker, G. Z.
Naturforsch. 2003, 58b, 838. (b) Capacchione, C.; Proto, A.; Ebeling, H.;
Muelhaupt, R.; Moller, K.; Spaniol, T. P.; Okuda, J. J. Am. Chem. Soc.
2003, 125, 4964. (c) Proto, A.; Capacchione, C.; Venditto, V.; Okuda, J.
Macromolecules 2003, 36, 9249. (d) 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. (e) Capacchione, C.; D’Acunzi, M.;
Motta, O.; Oliva, L.; Proto, A.; Okuda, J. Macromol. Chem. Phys. 2004,
205, 370. (f) Capacchione, C.; Proto, A.; Okuda, J. J. Polym. Sci., Part A:
Polym. Chem. 2004, 42, 2815. (g) Beckerle, K.; Capacchione, C.; Ebeling,
H.; Manivannan, R.; Mulhaupt, R.; Proto, A.; Spaniol, T. P.; Okuda, J. J.
Organomet. Chem. 2004, 689, 4636. (h) Capacchione, C.; De Carlo, F.;
Zannoni, C.; Okuda, J.; Proto, A. Macromolecules 2004, 37, 8918. (i)
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. (j) De Carlo, F.; Capacchione, C.; Schiavo, V.; Proto, A.
J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 1486. (k) Capacchione, C.;
Proto, A.; Ebeling, H.; Mu¨lhaupt, R.; Okuda, J. J. Polym. Sci., Part A:
Polym. Chem. 2006, 44, 1908. (l) Beckerle, K.; Manivannan, R.; Spaniol,
H. P.; Okuda, J. Organometallics 2006, 25, 3019. (m) Cohen, A.; Yeori,
A.; Goldberg, I.; Kol, M. Inorg. Chem. 2007, 46, 8114.
(9) The Mehr convention is used to illustrate the two diastereomers,
with bold and hashed bonds used to imply relative, not absolute,
configurations: Mehr, H. J. Chem. Educ. 1985, 62, 114.
(10) (a) Dogan, J.; Schulte, J. B.; Swiegers, G. F.; Wild, B. S. J. Org.
Chem. 2000, 65, 951. (b) Brooks, P.; Craig, D. C.; Gallagher, M. J.; Rae,
D. A.; Sarroff, A. J. Organomet. Chem. 1987, 323, C1. (c) Anderson, D. M.;
Hitchcock, P. B.; Lappert, M. F.; Leung, W.-P.; Zora, J. A. J. Organomet.
Chem. 1987, 333, C13.
(7) Boussie, T. R.; Bru¨mmer, O.; Diamond, G. M.; Goh, C.; LaPointe,
A. M.; Leclerc, M. K.; Shoemaker, J. A. W. (Symyx Technologies, Inc.)
US 7126031 B2, 2006.
(8) (a) Long, R. J.; Gibson, V. C.; White, A. J. P.; Williams, D. J. Inorg.
Chem. 2006, 45, 511. (b) Long, R. J.; Gibson, V. C.; White, A. J. P.
Organometallics 2008, 27, 235.
(11) Issleib, K.; Bo¨ttcher, W. Synth. React. Inorg. Met.-Org. Chem. 1976,
6, 179.
(12) (a) The same chlorophosphine has also been synthesized using
Me3SiCl followed by C2Cl6: Nieuwenhuyzen, M.; Saunders, G. C.; Smyth,
E. C. M. S. Organometallics 2006, 25, 996. (b) Mu¨ller, G.; Klinga, M.;
Leskela¨, M.; Reiger, B. Eur. J. Inorg. Chem. 2002, 2625.

5962 Organometallics, Vol. 27, No. 22, 2008
Long et al.
Table 1. Selected Bond Lengths (Å) and Angles (deg) for 2
Scheme 2. Synthesis of Diphosphanyl-bisphenoxide Zirconium
Dichloride Complexes
Zr-O(2)
1.989(3)
2.4001(10)
1.996(3)
109.63(4)
91.58(3)
100.70(8)
154.86(4)
92.85(8)
70.08(8)
69.37(8)
158.11(11)
Zr-P(1)
Zr-P(2)
2.7865(10)
2.8602(10)
2.3981(10)
151.78(4)
93.31(8)
Zr-Cl(1)
Zr-O(1)
Zr-Cl(2)
Cl(1)-Zr-Cl(2)
Cl(1)-Zr-P(2)
Cl(1)-Zr-O(2)
Cl(2)-Zr-P(2)
Cl(2)-Zr-O(2)
P(1)-Zr-O(1)
P(2)-Zr-O(2)
O(1)-Zr-O(2)
Cl(1)-Zr-P(1)
Cl(1)-Zr-O(1)
Cl(2)-Zr-P(1)
Cl(2)-Zr-O(1)
P(1)-Zr-P(2)
P(1)-Zr-O(2)
P(2)-Zr-O(1)
95.59(4)
98.21(8)
67.83(3)
90.16(8)
93.71(8)
Table 2. Selected Bond Lengths (Å) and Angles (deg) for 3
Zr-O(1)
2.0324(12)
2.0125(11)
2.7425(5)
2.7746(5)
2.4437(5)
91.814(17)
85.072(18)
154.59(3)
143.292(14)
77.51(3)
74.409(16)
69.15(3)
142.067(14)
69.78(3)
88.11(5)
84.33(3)
Zr-Cl(2)
2.6234(5)
2.6495(5)
3.1884(8)
4.1998(5)
Zr-O(2)
Zr-Cl(2A)
Cl(2) · · · Cl(2A)
Zr · · · ZrA
Zr-P(1)
sized via reaction of the dilithium salt (generated using nBuLi)
with ZrCl4(THF)2. Recrystallization from DCM/pentane gave
analytically pure, air- and moisture-sensitive samples of both
complexes. Crystals suitable for X-ray structure determinations
were grown by slow diffusion of pentane into DCM solutions
of the complexes.
Zr-P(2)
Zr-Cl(1)
Cl(1)-Zr-Cl(2)
Cl(1)-Zr-P(2)
Cl(1)-Zr-O(2)
Cl(2)-Zr-P(1)
Cl(2)-Zr-O(1)
Cl(2)-Zr-Cl(2A)
P(1)-Zr-O(1)
P(1)-Zr-Cl(2A)
P(2)-Zr-O(2)
O(1)-Zr-O(2)
O(2)-Zr-Cl(2A)
Cl(1)-Zr-P(1)
Cl(1)-Zr-O(1)
Cl(1)-Zr-Cl(2A)
Cl(2)-Zr-P(2)
Cl(2)-Zr-O(2)
P(1)-Zr-P(2)
P(1)-Zr-O(2)
P(2)-Zr-O(1)
P(2)-Zr-Cl(2A)
O(1)-Zr-Cl(2A)
Zr-Cl(2)-ZrA
84.564(15)
108.17(4)
91.776(18)
146.858(14)
111.09(3)
69.345(14)
83.27(3)
134.69(3)
72.726(15)
145.90(3)
105.591(16)
The X-ray crystal structure of 2 (Figure 2) shows the metal
center to have a distorted octahedral geometry (cis angles in
the range 67.83(3)-109.63(4)°, Table 1), with the tetradentate
ligand adopting a cis-R coordination mode, characterized by
the two end donors [O(1) and O(2)] being mutually trans. This
coordination mode gives approximate C2 symmetry to the
complex about an axis that passes through the metal center and
bisects the Cl(1)-Zr-Cl(2) angle. The only notable feature of
the bonding at the metal center is that the Zr-P(2) distance
of 2.8602(10) Å is statistically significantly longer than that of
Zr-P(1) [2.7865(10) Å]. This may be associated with the
noticeably different folds of the two five-membered C2OPZr
chelate rings. For both the P(1)/O(1) and P(2)/O(2) rings, the
{C2OP} atoms are coplanar to better than 0.01 Å, but whereas
for the former the metal lies ca. 0.32 Å out of this plane [in the
direction of P(2)], for the latter the metal lies only ca. 0.05 Å
out of this plane [in the direction of P(1)]. The C2P2Zr ring has
a twisted conformation, C(7) and C(8) lying ca. 0.44 and 0.28
Å “above” and “below” the {P2Zr} plane, respectively (in the
structure shown in Figure 2 this ring has a λ-twist, but the crystal
contains an equal number of complexes with a δ-twist).
The solid-state structure of 3 revealed an unexpected Ci-
symmetric dinuclear complex with a pair of seven-coordinate
zirconium centers bridged by two chlorine atoms (Figure 3).
The geometry at the metal center is distorted pentagonal
bipyramidal with Cl(1) and O(2) in the axial sites [the
Cl(1)-Zr-O(2) angle is 154.59(3)°]. Much of the distortion in
the coordination geometry is in the equatorial plane, where O(1)
lies ca. 0.71 Å out of the {Zr,P(1),P(2),Cl(2),Cl(2A)} plane,
which is coplanar to within ca. 0.06 Å. Both of the five-
membered C2OPZr chelate rings have folded geometries, with
the metal lying out of the associated {C2OP} plane which in
each case is coplanar to within ca. 0.02 Å. For the O(1)/P(1)
ring, the metal is displaced by ca. 0.88 Å towards O(2), while
for the O(2)/P(2) ring the metal is displaced by ca. 0.32 Å in
the direction of Cl(2a). The C2P2Zr ring again has a twisted
conformation, C(7) and C(8) lying ca. 0.59 and 0.20 Å “below”
and “above” the {P2Zr} plane, respectively (in the structure
shown in Figure 3 this ring has a λ-twist, but because of the
center of symmetry, the P(1A)/P(2A) ring has a δ-twist). The
two Zr-P bonds are asymmetric, with that to P(2) [2.7746(5)
Å] being ca. 0.03 Å longer than that to P(1) [2.7425(5) Å] (Table
2). This is probably caused by the differing trans environments.
The Zr-O bonds are also different, with that to the equatorial
oxygen O(1) [2.0324(12) Å] ca. 0.02 Å longer than that to its
axial counterpart O(2) [2.0125(11) Å]. The central Zr2Cl2 ring
is perfectly planar and has an asymmetric geometry, the two
Figure 2. Molecular structure of 2.
Figure 3. Molecular structure of 3.

Zr Complexes Containing Tetradentate O,P,P,O Ligands
Organometallics, Vol. 27, No. 22, 2008 5963
1
1
Figure 4. H and 31P NMR spectra of 2 in CDCl3 (*).
Figure 6. H and 31P NMR spectra of 4 in CDCl3.
the P(2) bound phenyl ring with an H · · · π separation of ca.
3.12 Å and a C-H · · · π angle of ca. 144°, the H · · · π vector
being inclined by ca. 70° to the ring plane.
The solution-state structure of 2 is consistent with the C2-
symmetric cis-R structure found in the solid state. The 1H NMR
spectrum showed one set of aromatic signals and two resonances
for the inequivalent protons of the ethylene bridge, while the
31P NMR spectrum gave a single resonance (Figure 4). The
behavior of 3 in solution is more complicated. The room
temperature 31P NMR (CDCl3) spectrum at 323 K showed
severely broadened signals (Figure 5), which resolve to two sets
of doublets at 223 K, suggesting that two asymmetric species
are present in solution. A solution equilibrium between the dimer
species identified in the solid state and its monomeric relative,
accompanied by intramolecular fluxional processes, may account
for these observations. In DMSO-d6 single, sharp peaks were
observed in both the 1H and 31P NMR spectra, consistent with
the donor solvent breaking up any aggregated species to give a
monomeric complex. The observation of only one 31P signal
for 3 in DMSO suggests that the complex is highly fluxional
on the NMR time scale in this solvent.
Reaction of rac-1 and meso-1 with ZrBn4 at -78 °C afforded
the zirconium dibenzyl complexes 4 and 5, respectively (Scheme
3), as analytically pure yellow solids that were highly sensitive
to air and moisture and also decomposed at room temperature
in the presence of light. The geometries of these complexes
was probed by NMR techniques. In addition to a single set of
1
Figure 5. Variable-temperature H and 31P NMR spectra of 3 in
CDCl3 and DMSO-d6 (*).
Scheme 3. Synthesis of Diphosphanyl-bisphenoxide Zirconium
Dibenzyl Complexes (Bn ) CH2Ph)
1
signals for the benzyl ligands, the H and 31P NMR spectra of
4 were comparable to those of its dichloro analogue 2, pointing
1
to a cis-R configuration (Figure 6). The H-coupled 13C NMR
1
spectrum revealed a JCH coupling constant of 128 Hz for the
benzylic carbon, indicating equivalent benzyl ligands coordi-
1
nated in an undistorted η1 fashion.14 The H and 31P NMR
spectra of 5 at room temperature showed single resonances for
the tert-butyl groups and phosphorus donors, consistent with
rapid exchange (Figure 7). At low temperature there was
significant broadening in the 1H NMR spectrum and two broad
signals in the 31P spectrum, consistent with a cis-ꢀ ground state.
Zr-Cl bonds differing by ca. 0.03 Å [Zr-Cl(2) 2.6234(5) Å,
Zr-Cl(2A) 2.6495(5) Å]. The bond to the terminal chlorine
Cl(1) is, unsurprisingly, much shorter at 2.4437(5) Å. The
transannular Zr · · · ZrA and Cl(2) · · · Cl(2A) distances [4.1998(5)
and 3.1884(8) Å, respectively] differ by more than 1 Å, and
this disparity is reflected in the angles within the ring
[Zr-Cl(2)-ZrA 105.591(16)°, Cl(2)-Zr-Cl(2A) 74.409(16)°].
The conformation of the complex is stabilized by a pair of
C-H · · · π contacts (a in Figure 3), with one of the methyl
protons of the O(1) tert-butyl unit approaching the centroid of
(13) Baechler, R. D.; Mislow, K. J. Am. Chem. Soc. 1970, 92, 3090.
(14) 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.

5964 Organometallics, Vol. 27, No. 22, 2008
Long et al.
1
Figure 7. Variable-temperature H and 31P NMR spectra of 5 in
CDCl3. * ) residual toluene.
Figure 9. 1H and 31P NMR spectra of (a) 4/[CPh3][B(C6F5)4] and
(b) 5/[CPh3][B(C6F5)4] in C6D5Br. * ) residual toluene; † ) residual
pentane.
Olefin Polymerization. Ethylene polymerization studies
using 2-5 were performed with either MAO or [CPh3]-
[B(C6F5)4] as the cocatalyst; the results are collected in Table
3. Conditions for 4 and 5 were optimized using in situ generated
precatalysts (4′ and 5′) and then compared to catalysts generated
from the isolated complexes. When MAO was used as the
cocatalyst, the rac-O,P,P,O-containing complexes 2 and 4′ gave
low productivities and a mixture of low molecular weight
oligomers (eC14) along with a high molecular weight polymeric
fraction consistent with multiple propagating species. In contrast,
activation of 4′ with [CPh3][B(C6F5)4] gave a highly active, long-
lived catalyst that exclusively gave the same oligomeric products
as 4′/MAO, suggesting that the active species responsible for
the polymeric product is formed via a side reaction with the
aluminoxane cocatalyst. Increasing the polymerization temper-
ature to 50 °C improved the activity of 4′/[CPh3][B(C6F5)4] to
5570g/mmol · h · bar(acomparableactivityof5450g/mmol · h · bar
was obtained with 4/[CPh3][B(C6F5)4]). The GC trace of the
liquid products is shown in Figure 10. In addition to linear
R-olefins a large number of branched products are formed,
indicative of efficient re-incorporation of the olefinic products.
For instance, the C6 fraction contains 2-ethyl-1-butene, which
is a dimerization product of ethylene and 1-butene.
Figure 8. Transition states of O,P,C and P,P,C trigonal face rotation
in 5.
Significantly, since two sets of signals are observed for the
1
benzyl ligands in the H NMR spectrum at room temperature,
P-P exchange must occur via rotation of a P,P,C trigonal face,
not a O,P,C face, which would give equivalent benzyls in the
transition state (see Figure 8).
Some insight into the nature of the catalytically active species
derived from diphosphanyl-bisphenoxide complexes was ob-
tained by treating 4 and 5 with [CPh3][B(C6F5)4] at room
temperature in NMR-scale reactions in C6D5Br. Included in the
1H NMR spectrum of 4/[CPh3][B(C6F5)4] (Figure 9a) are two
tert-butyl and four ethylene bridge signals. These, combined
with the observation of two doublets in the 31P spectrum, are
consistent with a square-pyramidal structure in which the benzyl
ligand does not migrate to and from the vacant site (although
coordination of the solvent at this site cannot be ruled out).15
The NMR spectra of 5/[CPh3][B(C6F5)4] (Figure 9b) were
consistent with a highly fluxional complex with one tert-butyl
and one phosphine signal in the 1H and 31P NMR spectra,
respectively. Neither cationic species was sufficiently stable to
obtain 1H-coupled 13C NMR spectra. However, the upfield shift
The meso-O,P,P,O-containing complexes 3 and 5′ also gave
high molecular weight polymer when activated with MAO. Only
a slight increase in activity (up to 116 g/mmol · h · bar) was
observed by switching to the boron activator, although the
molecular weight of the product dropped substantially to around
600 g/mol. Analysis of this product by 13C NMR spectroscopy
revealed a linear structure terminated by isobutyl and n-alkyl
end-groups, consistent with chain transfer to AliBu3 acting as
the sole termination mechanism.
1
of some of the aromatic signals in the H NMR spectrum of
5/[CPh3][B(C6F5)4] suggests η2-coordination of the remaining
benzyl ligand.
(15) The 19F NMR spectrum indicated no anion-cation interactions.

Zr Complexes Containing Tetradentate O,P,P,O Ligands
Organometallics, Vol. 27, No. 22, 2008 5965
Table 3. Ethylene Polymerization Using 2-5a
e
e
precatalyst
(loading (µmol))
temp
(°C)
liquid
solid
Mn
Mw
entry
cocatalyst
MAO
MAO
[CPh3][B(C6F5)4]
[CPh3][B(C6F5)4]
[CPh3][B(C6F5)4]
MAO
productb (g)
productc (g)
activityd (g/mmol · h · bar)
(kg/mol)
(kg/mol)
Mw/Mn
1
2
3
4
5
6
7
8
9
10
2 (5)
4′ (5)
4′ (1)
4′ (1)
4 (1)
3 (5)
5′ (5)
5′ (5)
5′ (5)
5 (5)
25
25
25
50
50
25
25
25
50
50
0.30
0.42
2.75
11.14
10.89
0.11
0.09
41
51
1380
5570
5450
11
16
80
107
116
>2000
>2000
0.11
0.16
0.80
1.07
1.16
>2000
>2000
1.1
MAO
[CPh3][B(C6F5)4]
[CPh3][B(C6F5)4]
[CPh3][B(C6F5)4]
0.5
0.4
0.6
2.2
1.8
1.2
0.7
0.7
a Polymerization conditions: glass reactor with mechanical stirrer, MAO (2.5 mmol) or [CPh3][B(C6F5)4] (1 equiv) with AliBu3 (0.5 mmol), toluene
(200 mL), 2 bar ethylene, 1 h. b Fraction analyzable by GC. c Obtained by precipitation with methanol. d Based on total yield. e Determined by
high-throughput GPC.
Scheme 4. Dimerization of Propylene to 1-Hexene
Under a propylene atmosphere16 at 50 °C, 4/[CPh3][B(C6F5)4]
gave predominantly 1-hexene (84 wt %) with a productivity of
211 g/mmol · h · bar. The C6 product is presumed to arise via a
1,2-insertion of propylene into a zirconium hydride followed
by a 2,1-insertion and finally ꢀ-hydrogen transfer (Scheme 4).
Higher oligomer fractions (up to around C30; see Supporting
Information for GC traces) were obtained using 5/[CPh3]-
[B(C6F5)4], although the productivity was notably reduced (43
Figure 10. GC trace from 4/[CPh3][B(C6F5)4] and ethylene at 50
°C. 1-Cn′′ ) n carbon linear 1-alkene, Cn ) n carbon product,
2-EB-1 ) 2-ethyl-1-butene, * ) GC reference, † ) toluene eluent.
g/mmol · h · bar at 50 °C).
The dramatic drop in productivity and molecular weight
center can explain the drop in molecular weight on tethering
observed with these O,P,P,O catalysts compared to the previ-
two bidentate O,P ligands to form one O,P,P,O ligand. Changing
ously reported bis(O,P) zirconium catalyst (up to 49 000
the size and electronic characteristics of the substituents attached
g/mmol · h · bar and Mn ) 8-17 kg/mol)9 is likely to be a
to the ortho position of the phenoxide donors and the P donors,
consequence of a more open coordination sphere caused by
as well as modulating the length of the unit bridging the
tethering of the phosphine donors with the relatively short
phosphorus centers, can be anticipated to have a marked affect
ethylene bridge. A more open coordination sphere can accelerate
on the productivities, product distribution, and stereoselectivities
ꢀ-hydrogen termination reactions and allow unrestricted access
afforded by this catalyst system.
to chain transfer agents. It is also consistent with the efficient
incorporation of higher olefins seen from polymerizations using
4/[CPh3][B(C6F5)4].
Experimental Methods
General Considerations. ZrCl4(THF)2 and Zr(CH2Ph)4 were
synthesized according to a published procedures.17 Air-sensitive
procedures were performed under nitrogen using standard Schlenk
Conclusions
techniques with solvents being distilled over standard drying agents
A new diphosphanyl-bisphenoxide ligand has been intro-
and degassed before use. Deuterated solvents were dried and stored
duced. Unlike their nitrogen donor relatives, i.e., the bis(ami-
over 4 Å molecular sieves. Ethylene (CP grade) and propylene
no)diphenoxide or salan ligand family, the large barrier to
(instrument grade) were purified by passing them through an Oxy-
inversion at tertiary phosphorus, compared to those found in
trap and a gas drier (Alltech Associates). Lithium wire (3.2 mm diam.,
tertiary amines, allows the stabilization of rac and meso isomers.
Differing solubilities for these isomers allowed for their
convenient separation. The resultant zirconium dichloride and
∼0.01% Na) was purchased from Aldrich Chemical Co. Compounds
were analyzed by NMR [Bruker AC-250, Bruker DRX-400, Bruker
Avance-400, or Bruker Avance-500 spectrometer (referenced to solvent
dibenzyl complexes selectively adopt a cis-R coordination mode
for the rac isomer and cis-ꢀ for the meso isomer. Having the
facility to change the coordination geometry of a complex
without changing the ligand substituents is a unique feature of
this class of tetradentate ligand, a facet that should readily lend
itself to other areas of transition and main group metal catalysis.
The cis-R complex, when treated with [CPh3][B(C6F5)4],
showed good ethylene oligomerization and propylene dimer-
ization activities. Less steric hindrance around the active metal
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]; and mass spectrometry [Autospec Q spectrometer]. Elemental
analyses were performed at London Metropolitan University. Liquid
oligomers were analyzed by GC [Agilent 6890 gas chromatograph
with a HP-5 column (30 m × 0.32 mm, film thickness 0.25 µm)] and
quantified against a known mass of 2,2,4,4,6,8,8-heptamethylnonane.
Solid oligomer/polymer samples were analyzed by 13C NMR [Bruker
Avance-400 spectrometer (in a 2:1 (by weight) mixture of 1,2,4-
(16) Conditions: Schlenk, magnetic stirring, 10 µmol of catalyst, heptane
(100 mL), AliBu3 (0.25 mmol), 2 bar of propylene, 50 °C, 1 h.
(17) (a) Manzer, L. E. Inorg. Synth. 1982, 21, 135. (b) Felten, J. J.;
Anderson, W. P. J. Organomet. Chem. 1972, 36, 87.

5966 Organometallics, Vol. 27, No. 22, 2008
Long et al.
C6H3Cl3/1,1,2,2-C2D2Cl4 at 130 °C using a pulse delay of 15 s)] and
GPC [Polymer Laboratories GPC-220 with PLgel HTS-B column (160
°C, 1,2,4-trichlorotoluene, run time ) 6 min, PS standards)].
The numbering scheme below is used in the assignments of the
O,P,P,O ligands and complexes:
MHz, CDCl3): δ 7.32-7.29 (m, 12H, Ar-H(5,B,C,D)). 7.16 (pt, J ) 5.9
Hz, 2H, OH), 6.98-6.94 (m, 2H, Ar-H(3)), 6.82 (pt, J ) 7.6 Hz, 2H,
Ar-H(4)), 2.22-2.08 (m, 4H, PCH2), 1.42 (s, 18H, C(CH3)3). 13C{1H}
NMR (101 MHz, CDCl3): δ 158.7 (pt, JCP ) 10.3 Hz, Ar-C(1)), 136.5
(Ar-C(6/A)), 136.0 (Ar-C(6/A)), 131.8 (pt, JCP ) 8.6 Hz, Ar-C(B)), 130.3
3
(Ar-C(3)), 129.0 (Ar-C(5)), 128.6 (d, JCP ) 3.9 Hz, Ar-C(C)), 128.6
(Ar-C(D)), 120.9 (Ar-C(2)), 120.4 (Ar-C(4)), 34.9 (C(CH3)3), 29.5
(C(CH3)3), 22.8 (PCH2). 31P{1H} NMR (101 MHz, CDCl3): δ -43.5
(s). MS (FAB; m/z): 543 (15%) [M]+, 285 (75%) [M -
P(Ph)((tBu)C6H3OH)]+, 77 (100%) [Ph]+. IR (KBr; cm-1): 3393br
(OH). Crystals suitable for X-ray structural determination were grown
from slow diffusion of pentane into a DCM solution.
rac-1. A diastereotopic mixture of 1 was triturated with degassed
methanol (25 mL) and then filtered. The filtrate was reduced in
volume to ca. 10 mL, cooled, and filtered to give rac-1 as a colorless
powder (32% yield). Anal. Calcd (%) for C34H40O2P2 (542.64): C,
[PhPC2H4PPh]2-Li+2(THF)4. A solution of 1,2-bis(diphenylphos-
phinoethane) (9.96 g, 25 mmol) in THF (100 mL) was added slowly
to a rapidly stirred THF suspension of Li (1.75 g, 250 mmol). The
mixture was allowed to warm to room temperature and stirred for 12 h.
The mixture was decanted from the excess Li and the solvent reduced
by half and cooled to -15 °C. The yellow precipitate was collected
by filtration, washed with cold THF (30 mL) and pentane (2 × 25
mL), and then dried under vacuum (10.53 g, 19.3 mmol, 77% yield).
1
75.26; H, 7.43. Found: C, 75.39; H, 7.51. H NMR (400 MHz,
CDCl3): δ 7.32-7.29 (m, 12H, Ar-H(5,B,C,D)). 7.18 (pt, J ) 5.9 Hz,
2H, OH), 6.94-6.91 (m, 2H, Ar-H(3)), 6.82 (pt, J ) 7.6 Hz, 2H,
Ar-H(4)), 2.21-2.04 (m, 4H, PCH2), 1.41 (s, 18H, C(CH3)3).
13C{1H} NMR (101 MHz, CDCl3): δ 158.9 (pt, JCP ) 10.4 Hz,
Ar-C(1)), 136.5 (Ar-C(6/A)), 136.2 (Ar-C(6/A)), 131.7 (pt, JCP ) 8.5
Hz, Ar-C(B)), 130.3 (Ar-C(3)), 129.0 (Ar-C(5)), 128.6 (Ar-C(C) + Ar-
C(D)), 120.4 (Ar-C(4)), 120.2 (Ar-C(2)), 34.9 (C(CH3)3), 29.5
(C(CH3)3), 22.6 (PCH2). 31P{1H} NMR (101 MHz, CDCl3): δ
-43.3 (s). MS (FAB; m/z): 543 (75%) [M]+, 285 (100%) [M -
P(Ph)((tBu)C6H3OH)]+. IR (KBr; cm-1): 3398br (OH).
3
1H NMR (400 MHz, C6D6): δ 7.69 (d, JHH ) 7.2 Hz, 4H, Ar-H),
7.12 (t, JHH ) 7.6 Hz, 4H, Ar-H), 6.72 (br, 2H, Ar-H), 3.36 (m, 16H,
OCH2CH2), 3.10 (br, 4H, PCH2), 1.25 (m, 16H, OCH2CH2). 31P{1H}
NMR (162 MHz, C6D6): δ -71-(-86) (br m).
[rac-2,2′-{1,2-Ethanediylbis(phenylphosphinidene)}bis(6-tert-
butyl)phenoxide]zirconium dichloride, 2. A THF (20 mL) solution
of rac-1 (0.326 g, 0.60 mmol) was added dropwise to a suspension of
NaH (36 mg, 1.5 mmol) in THF (10 mL) at 0 °C. The mixture was
stirred at room temperature for 3 h and then filtered. The excess NaH
was washed with THF, and the combined THF fractions were added
dropwise to a THF (20 mL) solution of ZrCl4(THF)2 (0.226 g, 0.60
mmol) at -78 °C. The mixture was allowed to warm to room
temperature over 12 h and the solvent then removed under vacuum.
The residue was extracted with DCM (20 mL) and the filtrate reduced
in volume to around 5 mL. Pentane (20 mL) was added and the
resultant precipitate filtered, washed with pentane (10 mL), and dried
under vacuum to give a colorless precipitate. Recrystallization from
DCM/pentane gave 2 (0.309 g, 0.44 mmol, 74% yield). Anal. Calcd
(%) for C34H38Cl2O2P2Zr (702.74): C, 58.11; H, 5.45. Found: C, 57.98;
H, 5.54. 1H NMR (500 MHz, CDCl3): δ 7.54-7.50 (m, 4H, Ar-H(B)),
7.42-7.35 (m, 8H, Ar-H(5,C,D)), 7.07-7.04 (m, 2H, Ar-H(3)), 6.90 (pt,
J ) 7.5 Hz, 2H, Ar-H(4)), 2.56 (dd, 2JHH ) 19.8 Hz, 3JHH ) 8.5 Hz,
2H, PCH(H)), 1.94-1.87 (m, 2H, PCH(H)), 1.42 (s, 18H, C(CH3)3).
13C{1H} NMR (126 MHz, CDCl3): δ 168.8 (pt, J ) 12.1 Hz, Ar-
C(1)), 138.7 (Ar-C(6)), 131.7 (pt, J ) 5.9 Hz, Ar-C(B)), 130.8 (Ar-C(5/
D)), 130.5 (Ar-C(5/D)), 129.9 (pt, JCP ) 18.0 Hz, Ar-C(A)), 129.6 (Ar-
C(3)), 128.8 (pt, JCP ) 4.5 Hz, Ar-C(C)), 121.4 (Ar-C(4)), 120.7 (pt, JCP
Ph(Cl)PC2H4P(Cl)Ph. To an ether (40 mL) solution of [Ph-
PC2H4PPh]2- · Li+2 · (THF)4 (3.63 g, 6.64 mmol) cooled to -78 °C
was slowly added PCl3 (2.9 mL, 33.2 mmol). The mixture was stirred
for 30 min at -78 °C and 30 min at 25 °C. The suspension was filtered
and the solvent removed from the filtrate. The resultant colorless
product (50:50 mix of rac and meso diastereomers) was washed with
cold pentane and dried under vacuum (1.38 g, 4.38 mmol, 66% yield).
1H NMR (400 MHz, C6D6): δ 7.41-7.36 (m, 4H, Ar-H), 7.02-6.95
(m, 6H, Ar-H), 2.19-1.83 (m, 4H, PCH2). 31P{1H} NMR (162 MHz,
C6D6): δ 92.4 (s), 91.8 (s).
2-Methoxymethoxy-3-tert-butylphenyl lithium · (Et2O)n. To an
ether solution (150 mL) of 1-tert-butyl-2-methoxymethoxybenzene
(23.4 g, 120 mmol) cooled to 0 °C was added n-butyllithium (2.5 M
in hexanes; 48 mL, 120 mmol). The mixture was stirred overnight at
room temperature, giving a yellow solution and colorless precipitate.
All volatiles were removed under vaccum. The product was triturated
with pentane (50 mL) for 3 h and then filtered, washed with pentane
(2 × 50 mL), and dried under vacuum (22.1 g, 80.5 mmol, 67% yield).
3
1H NMR (250 MHz, C6D6): δ 7.92 (d, JHH ) 5.0 Hz, 1H, Ar-H),
3
7.35 (d, JHH ) 7.5 Hz, 1H, Ar-H), 7.25-7.18 (m, 1H, Ar-H), 5.33
3
(s, 2H, OCH2O), 2.97 (q, JHH ) 7.0 Hz, 4nH, OCH2CH3), 2.80 (s,
3
3H, OCH3), 1.60 (s, 9H, C(CH3)3), 0.82 (t, JHH ) 7.0 Hz, 6nH,
OCH2CH3).
) 18.5 Hz, Ar-C(2)), 35.0 (C(CH3)3), 29.3 (C(CH3)3), 23.1 (pt, JCP
)
2,2′-[1,2-Ethanediylbis(phenylphosphinidene)]bis(6-tert-bu-
tyl)phenol, 1. An ether (10 mL) solution of 2-methoxymethoxy-3-
tert-butylphenyl lithium · (Et2O)n (n ) 0.92; 0.867 g, 3.23 mmol) was
added dropwise to a suspension of Ph(Cl)PC2H4P(Cl)Ph (0.504 g, 1.60
mmol) in ether (15 mL) cooled to -78 °C. The mixture was stirred
for 30 min at -78 °C and 30 min at 25 °C. The solvent was removed
and the residue dissolved in 9:1 AcOH/H2O (50 mL) and heated to
110 °C for 2 h. All volatiles were removed under vacuum and degassed
EtOAc and NH3(aq) (25 mL) added. The mixture was stirred for 1 h,
after which the organic fraction was separated and washed with NH3(aq)
(25 mL) and H2O (25 mL), dried (MgSO4), and filtered. The solvent
was removed to give a 1:1 diastereotopic mixture of the product as a
white powder (0.746 g, 1.37 mmol, 86% yield).
13.5 Hz, PCH2). 31P{1H} NMR (202 MHz, CDCl3): δ 0.6 (s). Crystals
suitable for X-ray structural determination were grown from slow
diffusion of pentane into a DCM solution.
[meso-2,2′-{1,2-Ethanediylbis(phenylphosphinidene)}bis(6-
tert-butyl)phenoxide]zirconium dichloride, 3. To a THF (20 mL)
solution of meso-1 (0.326 g, 0.60 mmol) cooled to -78 °C was added
n-BuLi (2.5 M in hexanes; 0.48 mL, 1.20 mmol) dropwise. The mixture
was allowed to warm to room temperature over 12 h and then filtered.
The filtrate was added dropwise to a THF (20 mL) solution of
ZrCl4(THF)2 (0.226 g, 0.60 mmol) at -78 °C. The mixture was
allowed to warm to room temperature over 12 h and the solvent then
removed under vacuum. The residue was extracted with DCM (20
mL) and the filtrate reduced in volume to around 5 mL. Pentane (20
mL) was added and the resultant precipitate filtered, washed with
pentane (10 mL), and dried under vacuum to give a colorless
precipitate. Recrystallization from DCM/pentane gave 3 (0.274 g, 0.39
meso-1. A diastereotopic mixture of 1 was triturated with degassed
methanol (25 mL) and then filtered to give insoluble meso-1 as a
colorless powder (44% yield). Anal. Calcd (%) for C34H40O2P2
(542.64): C, 75.26; H, 7.43. Found: C, 75.33; H, 7.34. 1H NMR (400

Zr Complexes Containing Tetradentate O,P,P,O Ligands
Organometallics, Vol. 27, No. 22, 2008 5967
mmol, 65% yield). Anal. Calcd (%) for C34H38Cl2O2P2Zr (702.74):
C, 58.11; H, 5.45. Found: C, 58.04; H, 5.34. H NMR (500 MHz,
(m, PCH2). 31P{1H} NMR (202 MHz, CDCl3, 298 K): δ 2.3 (s).
31P{1H} NMR (202 MHz, CDCl3, 223 K): δ 7.4 (br s), -3.6 (br s).
NMR Reactions Using [CPh3][B(C6F5)4]. In a nitrogen-filled
glovebox, a C6D5Br solution of [CPh3][B(C6F5)4] (1 equiv) was
added to a C6D5Br solution of 4 or 5 (1 equiv) at 25 °C. The orange
solution was transferred to an NMR tube fitted with a Youngs tap
valve. The NMR data were acquired immediately.
1
DMSO-d6): δ 7.70-7.67 (m, 4H, Ar-H(B)), 7.49-7.46 (m, 6H, Ar-
3
4
H(C,D)), 7.17 (dd, JHH ) 8.0 Hz, JHH ) 1.5 Hz, 2H, Ar-H(5)),
7.05-7.02 (m, 2H, Ar-H(3)), 6.69 (pt, J ) 8.0 Hz, 2H, Ar-H(4)), 2.94
(br, 2H, PCH(H)), 2.06 (br, 2H, PCH(H)), 1.22 (s, 18H, C(CH3)3).
13C{1H} NMR (126 MHz, DMSO-d6): δ 168.7 (m, Ar-C(1)), 136.7
(Ar-C(6)), 132.0-131.8 (m, Ar-C(A,B)), 129.9, 129.7, 128.6 (Ar-C(3,5,6)),
128.6 (Ar-C(C)), 123.7 (m, Ar-C(2)), 119.6 (Ar-C(4)), 34.5(C(CH3)3),
29.4 (C(CH3)3), 23.9 (m, PCH2). 31P{1H} NMR (242 MHz, CDCl3,
323 K): δ 22.2 (br), 10.9 (br), 8.3 (br). 31P{1H} NMR (242 MHz,
CDCl3, 298 K): δ 24.0 (s), 23.2 (s), 13.5 (s), 11.4 (s). 31P{1H} NMR
4/[CPh3][B(C6F5)4]. 1H NMR (250 MHz, C6D5Br): δ 7.34-6.73
(m, 38H, Ar-H). 6.64-6.56 (m, 3H, Ar-H). 3.82 (s, 2H, Ph3CCH2Ph),
2.70 (t, J ) 8.0 Hz, 1H, ZrC(H)HPh), 2.51-2.12 (m, 2H, PC(H)H),
2.18 (t, J ) 7.5 Hz, 1H, ZrC(H)HPh), 1.79 (t, J ) 15.0 Hz, 1H,
PC(H)H), 1.58 (t, J ) 14.7 Hz, 1H, PC(H)H), 1.28 (s, 9H, C(CH3)3),
1.15 (s, 9H, C(CH3)3). 31P{1H} NMR (101 MHz, C6D5Br): δ 32.5 (d,
(242 MHz, CDCl3, 223 K): δ 25.1 (d, 2JPP ) 29 Hz), 23.4 (d, 2JPP
)
2
25 Hz), 15.6 (d, 2JPP ) 29 Hz), 13.7 (d, 2JPP ) 25 Hz). 31P{1H} NMR
(202 MHz, DMSO-d6): δ 10.0 (s).
2JPP ) 29 Hz), 17.9 (d, JPP ) 29 Hz). 19F{1H} NMR (235 MHz,
C6D5Br): -136.0 (s, o-BC6F5), -166.4 (t, 3JFF ) 21.1 Hz, p-BC6F5),
-170.2 (pt, J ) 17.9 Hz, m-BC6F5).
[rac-2,2′-{1,2-Ethanediylbis(phenylphosphinidene)}bis(6-tert-
butyl)phenoxide]zirconium dibenzyl, 4. [Reaction performed in
the absence of light] To a mixture of rac-1 (135 mg, 0.25 mmol) and
ZrBn4 (113 mg, 0.25 mmol) cooled to -78 °C was added toluene (10
mL) cooled to -78 °C. The reaction mixture was stirred for 1 h at
-78 °C and 30 min at room temperature. The solvent was removed
under vacuum and the yellow residue triturated with pentane at 0 °C.
The mixture was filtered and dried under vacuum to give 4 as a yellow
powder (123 mg, 0.15 mmol, 60% yield). Anal. Calcd (%) for
C48H52O2P2Zr (814.10): C, 70.82; H, 6.44. Found: C, 70.69; H, 6.33.
1H NMR (500 MHz, CDCl3): δ 7.38 (dd, 3JHH ) 7.6 Hz, 4JHH ) 1.4
Hz, 2H, Ar-H(5)), 7.35-7.26 (m, 6H, Ar-H(C,D)), 7.20-7.13 (m, 6H,
Ar-H(3,B)), 6.90-6.87 (m, 6H, Ar-H(4,γ)), 6.77 (t, 3JHH ) 7.2 Hz, 2H,
Ar-H(δ)), 6.37 (d, 3JHH ) 7.3 Hz, 4H, Ar-H(ꢀ)), 2.42 (dd, 2JHH ) 19.1
1
5/[CPh3][B(C6F5)4]. H NMR (250 MHz, C6D5Br): δ 7.36 (d,
3JHH ) 7.8 Hz, 2H, Ar-H), 7.28-6.80 (m, 32H, Ar-H), 6.65-6.58
(m, 4H, Ar-H), 6.24 (t, 3JHH ) 7.3 Hz, 1H, Ar-H), 6.08 (d, 3JHH
)
6.8 Hz, 2H, Ar-H), 3.81 (s, 2H, Ph3CCH2Ph), 2.87 (s, 2H,
ZrCH2Ph), 2.33 (br, 2H, PC(H)H), 1.89 (br, 2H, PC(H)H), 1.48 (s,
18H, C(CH3)3). 31P{1H} NMR (101 MHz, C6D5Br): δ 16.5 (s).
19F{1H} NMR (235 MHz, C6D5Br): δ -135.9 (s, o-BC6F5), -166.2
(t, 3JFF ) 21.2 Hz, p-BC6F5), -170.0 (pt, J ) 18.1 Hz, m-BC6F5).
Ethylene Oligo/polymerization. A 400 mL glass Fischer-Porter
vessel was dried at 50 °C for 12 h. The Fischer-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 and then
charged with solvent, purged with 1 bar of ethylene overpressure for
5 min (to give 2 bar total ethylene pressure), and placed in a water
bath at the required temperature, allowing 10 min for the temperature
to equilibrate. Scavenger (MAO or AliBu3) was then 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.
Polymerizations were terminated by venting of 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.
3
Hz, JHH ) 8.0 Hz, 2H, PC(H)H), 1.80 (m, 2H, PC(H)H), 1.68 (d,
2JHH ) 8.9 Hz, 2H, ZrC(H)HPh), 1.34 (s, 18H, C(CH3)3), 1.11 (d,
2JHH ) 9.0 Hz, 2H, ZrC(H)HPh). 13C{1H} NMR (126 MHz, CDCl3):
δ 169.3 (pt, J ) 12.4 Hz, Ar-C(1)), 143.9 (Ar-C(R)), 137.7 (Ar-C(6)),
132.6 (pt, J ) 16.8 Hz, Ar-C(A)), 131.2 (pt, J ) 5.6 Hz, Ar-C(B)), 130.5
(Ar-C(3)), 130.0 (Ar-C(5)), 129.7 ((Ar-C(γ)), 128.9 (Ar-C(D)), 128.4 (pt,
J ) 4.2 Hz, Ar-C(C)), 127.2 (Ar-C(ꢀ)), 121.9 (Ar-C(δ)), 120.0 (pt, J )
16.7 Hz, Ar-C(2)), 119.7 (Ar-C(4)), 55.3 (ZrCH2Ph), 34.9 (C(CH3)3),
29.3 (C(CH3)3), 25.1 (pt, J ) 12.5 Hz, PCH2). 31P{1H} NMR (202
MHz, CDCl3): δ 13.2 (s).
[meso-2,2′-{1,2-Ethanediylbis(phenylphosphinidene)}bis(6-
tert-butyl)phenoxide]zirconium dibenzyl, 5. [Reaction performed
in the absence of light] To a mixture of meso-1 (136 mg, 0.25 mmol)
and ZrBn4 (115 mg, 0.25 mmol) cooled to -78 °C was added toluene
(10 mL) cooled to -78 °C. The reaction mixture was stirred for 1 h
at -78 °C and 30 min at room temperature. The solvent was removed
under vacuum and the yellow residue triturated with pentane at 0 °C.
The mixture was filtered and dried under vacuum to give 5 as a yellow
powder (150 mg, 0.18 mmol, 73% yield). Anal. Calcd (%) for
C48H52O2P2Zr (814.10): C, 70.82; H, 6.44. Found: C, 70.74; H, 6.32.
1H NMR (500 MHz, CDCl3, 298 K): δ 7.41-7.34 (m, 6H, Ar-H(C,D)),
7.28 (dd, 3JHH ) 7.6 Hz, 4JHH ) 1.5 Hz, 2H, Ar-H(5)), 7.12-7.08 (m,
4H, Ar-H(B)), 6.98 (pt, J ) 7.7 Hz, 2H, Ar-H(ꢀ′)), 6.89-6.74 (m, 7H,
Propylene Oligomerization. A Schlenk, containing 100 mL of
heptane and a magnetic stirrer and fitted with a rubber septum, was
purged under 1 bar 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 using a water bath to 50 °C. A
toluene solution of precatalyst treated with [CPh3][B(C6F5)4] was
introduced via syringe to initiate the polymerization. The reaction
mixture was rapidly stirred throughout. Polymerizations were termi-
nated by venting of the overpressure followed by addition of 5 mL of
2 M HCl(aq). A sample of the reaction mixture was taken for GC
analysis.
3
3
Ar-H(3,ꢀ,γ′,δ′)), 6.70 (t, JHH ) 7.5 Hz, 2H, Ar-H(4)), 6.65 (d, JHH
)
7.3 Hz, 2H, Ar-H(γ)), 6.60 (t, 3JHH ) 7.3 Hz, 1H, Ar-H(δ)), 2.55-2.45
(s + br, 4H, ZrCH2Ph + PC(H)H), 2.17-2.13 (t + br, J ) 4.8 Hz,
4H, ZrCH2Ph + PC(H)H), 1.28 (s, 18H, C(CH3)3). H NMR (500
Acknowledgment. This work was supported by Ineos
Technologies.
1
MHz, CDCl3, 223 K): δ 7.43-7.32 (br m, 6H, Ar-H), 7.26 (d, J )
9.0 Hz, 2H, Ar-H), 7.15-6.95 (br + t, J ) 9.0 Hz, 6H, Ar-H),
6.90-6.83 (m, 4H, Ar-H), 6.79-6.65 (m, 8H, Ar-H), 2.48 (br, 6H, 3
× CH2), 2.08 (br, 2H, CH2), 1.24 (br, 18H, C(CH3)3). 13C{1H} NMR
(101 MHz, CDCl3, 298 K): δ 168.3 (br, Ar-C(1)), 147.4 (Ar-C(R′)),
142.7 (Ar-C(R)), 137.8 (Ar-C(6)), 131.7 (pt, J ) 6.0 Hz, Ar-C(B)), 129.9
(Ar-C(5)), 129.7 (Ar-C(D)), 129.5 (Ar-C(ꢀ′)), 129.4 (Ar-C(ꢀ)), 128.7 (pt,
J ) 4.3 Hz, Ar-C(C)), 128.2 (Ar-C(3)), 127.3 (Ar-C(γ′)), 126.9 (Ar-C(γ)),
121.1 (Ar-C(δ′)), 120.8 (Ar-C(δ)), 120.1 (Ar-C(4)), 65.4-65.2 (m,
ZrCH2Ph), 61.8 (ZrCH2Ph), 34.9 (C(CH3)3), 29.5 (C(CH3)3), 25.9-25.5
Supporting Information Available: Crystallographic data for
meso-1, 2, and 3; kinetic data for phosphine inversion; GC traces
for oligomeric products; and polymer NMR data. This mate-
rial is available free of charge via the Internet at http://pubs.acs.
org.
OM800652W