Zirconium phosphinimide complexes: Synthesis, structure, and deactivation pathways in ethylene polymerization catalysis

Article abstract of DOI:10.1021/om010433q

Zirconium phosphinimide complexes of the form CpZr(NP-t-Bu₃)Cl₂ (1) and Cp*Zr(NPR₃)-Cl₂ (R = i-Pr (2), t-Bu (3)) were readily prepared under ambient conditions via the reaction of [CpZrCl₃]_n or Cp*ZrCl₃ with the appropriate trialkylphosphinimide lithium salt (R₃PNLi). A series of derivatives were readily obtained via alkylation or arylation of the above dihalide precursors. These included CpZr(NP-t-Bu₃)Me₂ (4), Cp*Zr(NPR₃)Me₂ (R = i-Pr (5), t-Bu (6)), CpZr(NP-t-Bu₃)Ph₂ (7), Cp*Zr(NPR₃)Ph₂ (R = i-Pr (8), t-Bu (9)), CpZr(NP-t-Bu₃)Bn₂ (10), CpZr(NP-t-Bu₃)(CH₂SiMe₃)₂ (11), Cp*Zr(NPR₃)(allyl)₂ (R = i-Pr (12), t-Bu (13)), Cp*Zr(NPR₃)(Cp)Cl (R = i-Pr (14), t-Bu (15)), and Cp*Zr(NPR₃)(CH₂C(CH₃)C(CH₃) CH₂) (R = i-Pr (16), t-Bu (17)). Reaction of 17 with the borane B(C₆F₅)₃ yielded the zwitterionic and cationic complexes Cp*Zr(NP-t-Bu₃)(CH₂C(CH₃)C(CH₃ )CH₂B(C₆F₅)₃) (18) and Cp*Zr(NP-t-Bu₃)(THF)-(CH₂C(CH₃)C(CH₃ )CH₂B(C₆F₅) ₃) (19). A number of the above compounds were screened for their potential as catalyst precursors in ethylene polymerization. In general, upon activation with methylaluminoxane, the resulting catalysts exhibit low activity. Efforts to understand the deactivation pathway for these zirconium catalysts involved investigating the interactions of catalyst precursors with activators. For example, reaction of 4 with the borane B(C₆F₅)₃ leads to aryl group transfer and formation of catalytically inactive CpZr(NP-t-Bu₃)(C₆F₅)₂ (20). Interactions with MAO were modeled via reaction with AlMe₃. The Zr clusters (Cp*Zr)₄(μ-Cl)₅(Cl) (μ-CH)₂ (21) and (Cp*Zr)₅(μ-Cl)₆(μ-CH)₃ (22) were two of the products that were characterized from these reactions. The isolation of 21 and 22 infers that aryl for methyl exchange, ligand abstraction, and C-H bond activation may be catalyst deactivation pathways.

Full text of DOI:10.1021/om010433q

4424
Organometallics 2001, 20, 4424-4433
Zir con iu m P h osp h in im id e Com p lexes: Syn th esis,
Str u ctu r e, a n d Dea ctiva tion P a th w a ys in Eth ylen e
P olym er iza tion Ca ta lysis
Nancy Yue, Emily Hollink, Fred Gue´rin, and Douglas W. Stephan*
School of Physical Sciences, Chemistry and Biochemistry, University of Windsor, Windsor,
Ontario, Canada N9B 3P4
Received May 23, 2001
Zirconium phosphinimide complexes of the form CpZr(NP-t-Bu3)Cl2 (1) and Cp*Zr(NPR3)-
Cl2 (R ) i-Pr (2), t-Bu (3)) were readily prepared under ambient conditions via the reaction
of [CpZrCl3]n or Cp*ZrCl3 with the appropriate trialkylphosphinimide lithium salt (R3PNLi).
A series of derivatives were readily obtained via alkylation or arylation of the above dihalide
precursors. These included CpZr(NP-t-Bu3)Me2 (4), Cp*Zr(NPR3)Me2 (R ) i-Pr (5), t-Bu (6)),
CpZr(NP-t-Bu3)Ph2 (7), Cp*Zr(NPR3)Ph2 (R ) i-Pr (8), t-Bu (9)), CpZr(NP-t-Bu3)Bn2 (10),
CpZr(NP-t-Bu3)(CH2SiMe3)2 (11), Cp*Zr(NPR3)(allyl)2 (R ) i-Pr (12), t-Bu (13)), Cp*Zr(NPR3)-
(Cp)Cl (R ) i-Pr (14), t-Bu (15)), and Cp*Zr(NPR3)(CH2C(CH3)C(CH3)CH2) (R ) i-Pr (16),
t-Bu (17)). Reaction of 17 with the borane B(C6F5)3 yielded the zwitterionic and cationic
complexes Cp*Zr(NP-t-Bu3)(CH2C(CH3)C(CH3)CH2B(C6F5)3) (18) and Cp*Zr(NP-t-Bu3)(THF)-
(CH2C(CH3)C(CH3)CH2B(C6F5)3) (19). A number of the above compounds were screened for
their potential as catalyst precursors in ethylene polymerization. In general, upon activation
with methylaluminoxane, the resulting catalysts exhibit low activity. Efforts to understand
the deactivation pathway for these zirconium catalysts involved investigating the interactions
of catalyst precursors with activators. For example, reaction of 4 with the borane B(C6F5)3
leads to aryl group transfer and formation of catalytically inactive CpZr(NP-t-Bu3)(C6F5)2
(20). Interactions with MAO were modeled via reaction with AlMe3. The Zr clusters (Cp*Zr)4-
(µ-Cl)5(Cl)(µ-CH)2 (21) and (Cp*Zr)5(µ-Cl)6(µ-CH)3 (22) were two of the products that were
characterized from these reactions. The isolation of 21 and 22 infers that aryl for methyl
exchange, ligand abstraction, and C-H bond activation may be catalyst deactivation
pathways.
In tr od u ction
Thus, in this paper we report the synthesis and struc-
ture of a family of neutral CpZr- and Cp*Zr-phosphin-
imide complexes. The activation, utility in olefin polym-
erization, and deactivation pathways of corresponding
zwitterionic and cationic Zr-phosphinimide catalysts
are examined and considered in the light of previous
work on Ti-phosphinimide systems.
Industrial interest in early metal metallocene based
single-site olefin polymerization catalysts has spurred
studies of related systems for more than 20 years. More
recently, systems that incorporate noncyclopentadienyl
ancillary ligands have been the subject of intense study.1
In our own efforts, we have uncovered several families
of titanium-based ethylene polymerization precatalysts
based on the steric analogy between phosphinimide
ligands and cyclopentadienyl ligands.2,3 In some cases,
the resulting catalysts exhibit unprecedented activity.2
The success of this approach appears to be the result of
the steric demands that are remote from the metal
center, making the immediate coordination sphere of
the metal center accessible. While others have recently
demonstrated that selected nonmetallocene derivatives
of Zr do show good activity in olefin polymerization
catalysis, the related systems that incorporate phosphin-
imide ligands have received only limited attention.4-10
Exp er im en ta l Section
Gen er a l Da ta . All preparations were done under an
atmosphere of dry, O2-free N2 employing both Schlenk line
techniques and Innovative Technologies, Braun, or Vacuum
Atmospheres inert-atmosphere gloveboxes. Solvents were
purified by employing Grubb type column systems manufac-
(4) Carraz, C.-A.; Stephan, D. W. Organometallics 2000, 19, 3791-
3796.
(5) Gue´rin, F.; Stewart, J . C.; Beddie, C.; Stephan, D. W. Organo-
metallics 2000, 19, 2994-3000.
(6) Gue´rin, F.; Stephan, D. W. Angew. Chem., Int. Ed. 2000, 39,
1298-1300.
(7) Kickham, J . E.; Gue´rin, F.; Stewart, J . C.; Stephan, D. W. Angew.
Chem., Int. Ed., 2000, 39, 3263-3266.
(1) Britovsek, G. J . P.; Gibson, V. C.; Wass, D. F. Angew. Chem.,
Int. Ed. 1999, 38, 428-447.
(8) Sung, R. C. W.; Courtenay, S.; McGarvey, B. R.; Stephan, D. W.
Inorg. Chem., 2000, 39, 2542-2546.
(2) Stephan, D. W.; Gue´rin, F.; Spence, R. E. v. H.; Koch, L.; Gao,
X.; Brown, S. J .; Swabey, J . W.; Wang, Q.; Xu, W.; Zoricak, P.; Harrison,
D. G. Organometallics 1999, 18, 2046-2048.
(9) Courtenay, S.; Stephan, D. W. Organometallics 2001, 20, 1442-
1450.
(3) Stephan, D. W.; Stewart, J . C.; Gue´rin, F.; Spence, R. E. v. H.;
Xu, W.; Harrison, D. G. Organometallics 1999, 18, 1116-1118.
(10) Kickham, J . E.; Gue´rin, F.; Stewart, J . C.; Urbanska, E.;
Stephan, D. W. Organometallics, 2001, 20, 1175-1182.
10.1021/om010433q CCC: $20.00 © 2001 American Chemical Society
Publication on Web 09/11/2001

Zirconium Phosphinimide Complexes
Organometallics, Vol. 20, No. 21, 2001 4425
tured by Innovative Technology.11 All organic reagents were
purified by conventional methods. Solvents used for the
generation of zwitterionic species were further purified by
distillation from Na/benzophenone. 1H and 13C{1H} NMR
spectra were recorded on Bruker Avance 300 and 500 spec-
trometers operating at 300 and 500 MHz, respectively. Trace
amounts of protonated solvents were used as references, and
chemical shifts are reported relative to SiMe4. 31P NMR, 11B
NMR, and 19F NMR spectra were recorded on a Bruker Avance
300 and are referenced to 85% H3PO4, saturated NaBH4/H2O,
and 80% CFCl3 in CDCl3, respectively. Guelph Chemical
Laboratories performed combustion analyses. In some cases,
particularly the alkyl derivatives, repeated attempts to obtain
good elemental analyses were unsuccessful, despite the fact
that X-ray-quality crystals of the respective compounds were
sent. This reflects the limited stability and high sensitivity of
Hz), 29.5, 28.1; 31P{1H} NMR (C6D6) δ 33.4. Anal. Calcd for
C
19H38NPZr: C, 56.67; H, 9.51; N, 3.48. Found: C, 53.59; H,
9.41; N, 3.18. 5: yield 73 mg (80%); 1H NMR (C6D6) δ 2.10 (s,
15H, CH3), 1.64 (m, 3H, CH, J H-H ) 7 Hz), 0.98 (dd, 18H, CH3,
J H-H ) 7 Hz, J P-H ) 14 Hz), 0.08 (s, 6H, CH3); 13C{1H} NMR
(C6D6) δ 117.1, 31.3, 26.8 (d, J P-C ) 58 Hz), 17.5, 12.0; 31P-
{1H} NMR (C6D6) δ 22.5. 6: yield 80%; 1H NMR (C6D6) δ 2.09
(s, 15H, C5(CH3)5), 1.24 (d, 27H, J P-H ) 12 Hz, (CH3)3C), 0.11
(s, 6H, Zr-CH3); 13C{1H} NMR (C6D6) δ 116.6, 40.5 (d, J P-C
)
47 Hz), 31.8, 29.7, 11.6; 31P{1H} NMR (C6D6) δ 34.2 (s). 7: light
1
brown, crystalline solid (84%); H NMR (C6D6) δ 7.95 (d, 4H,
J H-H ) 7 Hz, C6H5 (o-H)), 7.31 (t, 4H, J H-H ) 7 Hz, C6H5 (m-
H)), 7.21 (t, 2H, J H-H ) 7 Hz, C6H5 (p-H)), 6.38 (s, 5H, C5H5),
1.06 (d, 27H, J P-H ) 6 Hz, (CH3)3C); 13C{1H} NMR (C6D6) δ
183.9, 136.7, 126.9, 126.7, 111.5, 40.2 (d, J P-C ) 46 Hz), 23.0;
31P{1H} NMR (C6D6) δ 35.4 (s). 8: yield 82%; 1H NMR (C6D6)
δ 7.94 (d, 4H, o-Ar, J H-H ) 7 Hz), 7.35 (t, 4H, m-Ar, J H-H ) 7
Hz), 7.23 (d, 2H, p-Ar, J H-H ) 7 Hz), 2.03 (s, 15H, Cp*), 1.60
(m, 3H, CH, J H-H ) 7 Hz), 0.85 (dd, 18H, CH3, |J H-H| ) 7 Hz,
J H-H ) 14 Hz); 13C{1H} NMR (C6D6) δ 189.1, 137.0, 126.9,
126.8, 119.5, 26.4 (d, J P-C ) 57 Hz), 17.5, 12.6; 31P{1H} NMR
(C6D6) δ 24.7. 9: yield 79%, white solid; 1H NMR (C6D6) δ 7.95
(d, 4H, o-Ar, J H-H ) 7 Hz), 7.34 (t, 4H, m-Ar, J H-H ) 7 Hz),
7.21 (d, 2H, p-Ar, J H-H ) 7 Hz), 1.98 (s, 15H, Cp*), 1.10 (d,
27H, CH3, J H-H ) 12 Hz); 13C{1H} NMR (C6D6) δ 189.5, 136.8,
126.9, 126.7, 119.5, 40.7 (d, C, J P-C ) 47 Hz), 30.0, 12.7; 31P-
{1H} NMR (C6D6) δ 35.8. Anal. Calcd for C34H52NPZr: C, 68.40;
H, 8.78; N, 2.35. Found: C, 68.50; H, 8.72; N, 2.39. 10: light
brown solid when washed with Et2O (80%); 1H NMR (C6D6) δ
7.22 (t, 4H, J H-H ) 8 Hz, C6H5 (o-H)), 7.03 (d, 4H, J H-H ) 7
Hz, C6H5 (m-H)), 6.93 (t, 2H, J H-H ) 9 Hz, C6H5 (p-H)), 5.95
(s, 5H, C5H5), 2.48, 2.03 (AB q, 4H, J H-H ) 10 Hz, CH2C6H5),
1.09 (d, 27H, J P-H ) 13 Hz, (CH3)3-C-); 13C{1H} NMR (C6D6)
δ 149.9, 130.0, 126.3, 120.7, 111.7, 56.5, 40.2 (d, J P-C ) 45
Hz), 29.5; 31P{1H} NMR (C6D6) δ 35.4. 11: white solid (77%);
1H NMR (C6D6) δ 6.35 (s, 5H, C5H5), 1.15 (d, 27H, J P-H ) 13
Hz, (CH3)3C), 0.34 (s, 18H, CH2Si(CH3)3), 0.47, 0.07 (AB q, 4H,
J H-H ) 11 Hz, CH2Si(CH3)3); 13C{1H} NMR (C6D6) δ 109.5,
42.5, 40.4 (d, J P-C ) 47 Hz), 29.6, 4.3; 31P{1H} NMR (C6D6)
1
these compounds. In these cases, H NMR spectra have been
deposited in the Supporting Information. The compounds R3-
PNSiMe3 and R3PNLi were prepared via known methods.12,13
[CpZrCl3]n, Cp*ZrCl3, and AlMe3 were purchased from Aldrich
and Strem Chemical Companies and used without further
purification.
Syn th esis of Cp Zr (NP -t-Bu 3)Cl2 (1). Solid t-Bu3PNLi
(0.16 g, 0.72 mmol) was added in several portions over a 30
min period to a slurry of [CpZrCl3]n (0.18 g, 0.72 mmol) in PhH
(20 mL). The heterogeneous solution was stirred for 12 h at
25 °C, after which time it was filtered through Celite. Removal
of the solvent in vacuo afforded a white crystalline solid (0.26
g, 81%). 1H NMR (C6D6): δ 6.40 (s, 5H, C5H5), 1.10 (d, 27H,
J P-H ) 12 Hz, (CH3)3C). 13C{1H} NMR (C6D6): δ 113.8, 41.0
(d, J P-C ) 28 Hz), 29.8. 31P{1H} NMR (C6D6): δ 40.7. Anal.
Calcd for C17H32Cl2NPZr: C, 46.26; H, 7.26; N, 3.17. Found:
C, 46.21; H, 7.30; N, 3.16.
Syn th esis of Cp *Zr (NP R3)Cl2 (R ) i-P r (2), t-Bu (3)).
These compounds were prepared in a similar manner, and thus
only one preparation is described in detail. To a slightly turbid
yellow toluene solution (80 mL) of Cp*ZrCl3 (1.00 g, 3.00 mmol)
was added a toluene solution (10 mL) of i-Pr3PNLi (0.54 g,
3.00 mmol). The solution was stirred at room temperature
overnight. The resulting solution was filtered. Removal of
toluene under vacuum gave a yellow solid. 2: yield 1.11 g
(74%); 1H NMR (C6D6) δ 2.16 (s, 15H, CH3), 1.61 (m, 3H, CH,
J H-H ) 7 Hz), 0.92 (dd, 18H, CH3, J H-H ) 7 Hz, J P-H ) 12
Hz); 13C{1H} NMR (C6D6) δ 122.1, 26.3 (d, J P-C ) 59 Hz), 17.1,
12.3; 31P{1H} NMR (C6D6) δ 27.4. Anal. Calcd for C19H36Cl2-
NPZr: C, 48.39; H, 7.69; N, 2.97. Found: C, 48.25; H, 8.83;
N, 3.04. 3: 1H NMR (C6D6) δ 2.17 (s, 15H, C5(CH3)5), 1.20 (d,
27H, J P-H ) 13 Hz, (CH3)3C); 13C{1H} NMR (C6D6) δ 121.9,
40.7 (d, J P-C ) 45 Hz), 29.6, 12.2; 31P{1H} NMR (C6D6) δ 42.2.
Syn th esis of Cp Zr (NP -t-Bu 3)Me2 (4), Cp *Zr (NP R3)Me2
(R ) i-P r (5), t-Bu (6)), Cp Zr (NP -t-Bu 3)P h 2 (7), Cp *Zr -
(NP R3)P h 2 (R ) i-P r (8), t-Bu (9)), Cp Zr (NP -t-Bu 3)Bn 2
(10), Cp Zr (NP -t-Bu 3)(CH2SiMe3)2 (11), a n d Cp *Zr (NP R3)-
(a llyl)2 (R ) i-P r (12), t-Bu (13)). These compounds were
prepared in a similar manner using the appropriate Grignard
reagents and Zr precursor; thus, only one preparation is
described in detail. A solution of MeMgBr (3.6 mmol) in Et2O
was added dropwise at room temperature to a slurry of 1 (0.32
g, 0.72 mmol) in the same solvent (30 mL). The heterogeneous
mixture was stirred for 15 h, after which time the solvent was
removed in vacuo. The product was extracted with hexanes
(3 × 20 mL) and filtered through Celite. Removal of the solvent
afforded a white solid (0.21 g, 72%). 4: 1H NMR (C6D6) δ 6.26
(s, 5H, C5H5), 1.16 (d, 27H, J P-H ) 13 Hz, (CH3)3C), 0.26 (s,
6H, ZrCH3); 13C{1H} NMR (C6D6) δ 109.7, 40.3 (d, J P-C ) 47
1
34.0. 12: yield 71%; H NMR (C6D6) δ 6.00 (quint, 2H, CH,
J H-H ) 12 Hz), 3.23 (d, 4H, CH2, J H-H ) 12 Hz), 1.88 (s, 15H,
Cp*), 1.54 (m, 3H, CH, J H-H ) 7 Hz), 0.84 (dd, 18H, J H-H ) 7
Hz, J H-H ) 14 Hz); 13C{1H} NMR (C6D6) δ 143.4, 115.1, 73.4,
26.4 (d, J P-C ) 57 Hz), 17.6, 12.2; 31P{1H} NMR (C6D6) δ 21.3.
13: yield 73%, white solid; 1H NMR (C6D6) δ 6.04 (quint, 2H,
CH, J H-H ) 12 Hz), 3.27 (d, 4H, CH2, J H-H ) 12 Hz), 1.89 (s,
15H, Cp*). 1.12 (d, 27H, CH3, |J H-H| ) 18 Hz); 13C{1H} NMR
(C6D6) δ 143.6, 115.1, 73.3, 41.1 (d, J P-C ) 46 Hz), 30.1, 12.2;
31P{1H} NMR (C6D6) δ 29.1.
Syn th esis of Cp *Zr (NP R3)(Cp )Cl (R ) i-P r (14), t-Bu
(15)). Both compounds were prepared via similar routes; thus,
only one representative procedure is described. To a yellow
THF solution (5 mL) of 2 (100 mg, 0.21 mmol) was added a
THF solution of (3 mL) NaCp‚2THF (123 mg, 0.53 mmol). The
solution was stirred at room temperature overnight. Removal
of benzene under vacuum gave a yellow solid. The solid was
extracted with 4 × 5 mL of hexane, followed by filtration and
evaporation under vacuum. 14: yield 57%, light yellow solid;
1H NMR (C6D6) δ 6.13 (s, 5H, Cp), 1.99 (s, 15H, Cp*), 1.75 (m,
3H, CH, J H-H ) 7 Hz), 0.98 (dd, 18H, CH3, J H-H ) 7 Hz, J P-H
) 14 Hz); 13C{1H} NMR (C6D6) δ 119.0, 111.7, 27.9 (d, CH,
J P-C ) 57 Hz), 17.4, 12.5; 31P{1H} NMR (C6D6) δ 24.0. Anal.
Calcd for C24H41ClNPZr: C, 57.51; H, 8.24; N, 2.79. Found:
C, 57.76; H, 9.11; N, 2.91. 15: yield 68%, light yellow solid;
1H NMR (C6D6) δ 6.27 (s, 5H, Cp), 2.02 (s, 15H, Cp*), 1.28 (d,
27H, CH3, J H-H ) 12 Hz); 13C{1H} NMR (C6D6) δ 119.9, 112.3,
41.2 (d, J P-C ) 46 Hz), 30.5, 12.9; 31P{1H} NMR (C6D6) δ 37.8.
(11) Pangborn, A. B.; Giardello, M. A.; Grubbs, R. H.; Rosen, R. K.;
Timmers, F. J . Organometallics 1996, 15, 1518.
(12) Latham, I. A.; Leigh, G. J .; Huttner, G.; J ibril, I. J . Chem. Soc.
D 1986, 377-384.
(13) Rubenstahl, T.; Weller, F.; Harms, K.; Dehnicke, K. Z. Anorg.
Allg. Chem. 1994, 620, 1741-1749.
Syn th esis of Cp *Zr (NP R3)(CH2C(CH3)C(CH3)CH2) (R
) i-P r (16), t-Bu (17)). These compounds were prepared in a
similar manner, and thus a single preparation is detailed. To
a yellow THF solution (5 mL) of 3 (100 mg, 0.19 mmol) was

4426 Organometallics, Vol. 20, No. 21, 2001
Yue et al.
added excess Mg (14 mg, 0.59 mmol). After 30 min of stirring,
the solution mixture became deep blue, and 2,3-dimethyl-1,3-
butadiene (16 mg, 0.19 mmol) was added. The resulting
solution was stirred at room temperature overnight. Removal
of THF under vacuum gave a dark green solid. Extraction with
4 × 5 mL of hexane and subsequent removal of the solvent
gave 77 mg (75%) of orange solid product, 17. 16: yield 76%,
orange solid; 1H NMR (C6D6) δ 2.73 (d, 2H, CH2, J H-H ) 9 Hz),
45 Hz, (CH3)3-C), 28.9 (s, (CH3)3-C). 19F{1H} NMR (C6D6): δ
-118.7 (m, 4F, o-F), -154.5 (t, 2F, J F-F ) 20 Hz, p-F), -161.5
(m, 4F, m-F). 31P{1H} NMR (C6D6): δ 42.7 (s). Anal. Calcd for
C
29H32F10NPZr: C, 49.28; H, 4.56; N, 1.98. Found: C, 49.10;
H, 4.37; N, 1.74.
Rea ction of 2 w ith AlMe3. (i) To a yellow benzene solution
(0.5 mL) of 2 (100 mg; 0.21 mmol) was added a 2.5 M hexanes
solution (0.42 mL, 1.06 mmol) of AlMe3. The color of the
solution changed from yellow to red after it was left in an NMR
tube overnight. NMR data revealed the formation of a complex
mixture of products. A few crystals of 21 suitable for X-ray
crystallography were obtained. This species was identified by
(Cp*Zr)4(µ-Cl)5(Cl)(µ-CH)2‚0.5C6H6 (21). Yield: <5%. 1H NMR
(C6D6): δ 14.29 (s, 2H, CH), 2.06 (s, 15H, CH3), 1.97 (s, 30H,
CH3), 1.95 (s, 15H, CH3). 13C{1H} NMR (C6D6): partial, 123.5,
120.1, 13.8, 13.3, 12.8.
(ii) To a turbid yellow solution of 136 mg (0.288 mmol) of 2
in 0.5 mL of C6D6 was added dropwise 0.14 mL (1.44 mmol) of
AlMe3. The color of the solution changed from yellow to red
after it was left in an NMR tube overnight. NMR data revealed
the formation of a complex mixture of products. After 3 days,
red crystals suitable of 22 suitable for X-ray crystallography
were obtained. This species was identified as (Cp*Zr)5(µ-Cl)6-
(µ-CH)3‚C6H6 (22). Yield: <5%. 1H NMR (C6D6): δ 14.4 (s, 2H,
CH), 9.34 (s, 1H, CH), 2.06 (s, 15H, CH3), 1.97 (s, 15H, CH3),
1.93 (s, 30H, CH3), 1.83 (s, 15H, CH3). 13C{1H} NMR (C6D6):
δ 372.9 (s, 2 CH), 168.3 (s, CH), 120.8, 119.6, 118.1, 14.45,
13.6, 13.4, 13.3.
Eth ylen e P olym er iza tion . (i) A solution of 6-10 µmol of
catalyst precursor in 2.0 mL of dry toluene was added to a
flask containing 2.0 mL of dry toluene. A 500 equiv amount of
a 10 wt % toluene solution of MAO was added to the flask.
Alternatively, the catalyst precursors were combined with
[Ph3C][B(C6F5)4] under an ethylene atmosphere at 25 °C. The
flask was attached to a Schlenk line with a cold trap, a
stopwatch was started, and the flask was evacuated three
times for 5 s and refilled with predried 99.9% ethylene gas.
The solution was rapidly stirred under 1 atm of ethylene at
room temperature. The polymerization was stopped by the
injection of a 1.0 N HCl/methanol solution. The total reaction
time was noted, and the polymer was isolated.
(ii) A typical experiment is as follows: a 1 L autoclave was
dried under vacuum (10-2 mmHg) for several hours. Toluene
(500 mL) was transferred into the vessel under a positive
pressure of N2 and was heated to 30 °C. The temperature was
controlled (to ca. (2 °C) with an external heating/cooling bath
and was monitored by a thermocouple that extended into the
polymerization vessel. A solution of MAO (500 equiv) in
toluene was injected, and the mixture was stirred for 3 min
at a rate of 150 rpm. The precatalyst in a solution of toluene
was then injected while the reaction mixture was stirred for
3 min at the same rate. The rate of stirring was increased to
1000 rpm, and the vessel was vented of N2 and pressurized
with ethylene (33 psi). Any recorded exotherm was within the
allowed temperature differential of the heating/cooling system.
The solution was stirred for 1 h, after which time the reaction
was quenched with 1 M HCl in MeOH. The precipitated
polymer was subsequently washed with MeOH and dried at
100 °C for at least 24 h prior to weighing.
2.14 (s, 15H, Cp*), 2.10 (s, 6H, CH3), 1.55 (m, 3H, CH, J H-H
)
7 Hz), 0.87 (dd, 18H, CH3, J H-H ) 7 Hz, J P-H ) 14 Hz), -0.06
(d, 2H, CH2, J H-H ) 9 Hz); 13C{1H} NMR (C6D6) δ 115.6, 112.2,
57.2, 28.0 (d, J P-C ) 57 Hz), 25.0, 17.9, 12.7; 31P{1H} NMR
(C6D6) δ 19.1. Anal. Calcd for C25H46NPZr: C, 62.19; H, 9.60;
N, 2.90. Found: C, 61.89; H, 9.40; N, 2.58. 17: 1H NMR (C6D6)
δ 2.20 (s, 6H, CH3), 2.17 (d, 2H, CH2, J H-H ) 11 Hz), 2.12 (s,
15H, Cp*), 1.12 (d, 27H, CH3, J P-H ) 12 Hz), 0.38 (d, 2H, CH2,
J H-H ) 11 Hz); 13C{1H} NMR (C6D6) δ 121.6, 115.8, 55.3, 40.0
(d, J P-C ) 48 Hz), 30.5, 25.6, 12.7; 31P{1H} NMR (C6D6) δ 33.2.
Anal. Calcd for C28H52NPZr: C, 64.07; H, 9.98; N, 2.67.
Found: C, 63.87; H, 9.67; N, 2.54.
Gen er a t ion of Cp *Zr (NP -t-Bu 3)(CH 2C(CH 3)C(CH 3)-
CH2B(C6F 5)3) (18). Compound 17 (148 mg, 0.313 mmol) and
B(C6F5)3 (176 mg, 0.344 mmol) were placed into a reaction vial.
Toluene (6 mL) was added to the solid mixture and the solution
stirred at 25 °C overnight. The solution was decanted and the
yellow solid was dried under vacuum. Yield: 208 mg (71%).
1H NMR (tol-d8): δ 2.21 (m, 2H, CH2, J H-H ) 12 Hz), 1.79 (s,
15H, Cp*-CH3), 1.60 (s, 3H, diene-CH3), 1.52 (3H, diene-CH3),
0.59 (d, 2H, CH2, J H-H ) 15 Hz), 0.95 (d, 27H, t-Bu-CH3, J P-H
) 15 Hz). 31P{1H} NMR (tol-d8): δ 44.2. 11B NMR (tol-d8): 31.7.
19F NMR (tol-d8, 193 K): m-F, δ -127.8, -130.2, -131.1,
-131.1, -133.1, -134.6, p-F, δ -158.7, -159.1, -160.3; o-F,
δ -161.9, -162.9, -162.9, -163.7, -164.9, -166.2. The
extreme sensitivity of this compound precluded elemental
analysis; NMR data have been deposited as Supporting
Information.
Gen er a tion of Cp *Zr (NP -t-Bu 3)(THF )n (CH2C(CH3)C-
(CH3)CH2B(C6F 5)3) (19). Compound 18 was dissolved in THF
and characterized by NMR methods. 1H NMR (THF-d8): 2.36
(d, 1H, CH2, J H-H ) 13 Hz), 2.22 (d, 1H, CH2, J H-H ) 13 Hz),
2.06 (s, 15H, Cp*-CH3), 1.56 (d, 3H, diene-CH3, J H-H ) 14 Hz),
1.46 (d, 27H, CH3, J P-H ) 13 Hz), 1.35 (s, 3H, CH3), 0.88 (br.
m, 1H, CH2, J H-H ) 13 Hz), 0.82 (d, 1H, CH2, J H-H ) 11 Hz).
31P{1H} NMR (THF-d8): 46.5. 13C{1H} NMR (THF-d8): 128.5
(d, J P-C ) 57 Hz), 122.0, 78.8, 40.4 (d, J P-C ) 45 Hz), 34.4,
29.3, 28.1, 21.8, 19.1, 11.1. 11B{1H} NMR (THF-d8): 28.5. 19F-
{1H} NMR (THF-d8): -130.1 (s, o-C6F5), -165.7 (t, m-C6F5),
-168.4 (t, p-C6F5). The extreme sensitivity of this compound
precluded elemental analysis; NMR data have been deposited
as Supporting Information.
Syn th esis of Cp Zr (NP -t-Bu 3)(C6F 5)2 (20). This compound
was obtained in two ways. (i) A solution of C6F5MgBr (2.8
mmol) in Et2O was added dropwise at 25 °C to a slurry of 1
(0.25 g, 0.56 mmol) in the same solvent (80 mL). The
heterogeneous mixture was stirred for 15 h, after which time
the solvent was removed in vacuo. The product was extracted
with PhH (3 × 20 mL) and filtered through Celite. Following
removal of solvent, the brown residue was washed with
hexanes (3 × 5 mL), filtered, and dried in vacuo to afford a
pale gray solid (0.32 g, 81%).
X-r a y Da ta Collection a n d Red u ction . X-ray-quality
crystals were obtained directly from the preparation as
described above. The crystals were manipulated and mounted
in capillaries in a glovebox, thus maintaining a dry, O2-free
environment for each crystal. Diffraction experiments were
performed on a Siemens SMART System CCD diffractometer.
The data were collected for a hemisphere of data in 1329
frames with 10 s exposure times. Crystal data are summarized
in Table 1. The observed extinctions were consistent with the
space groups in each case. A measure of decay was obtained
by re-collecting the first 50 frames of each data set. The
intensities of reflections within these frames showed no
(ii) Solid 4 (36 mg, 0.089 mmol) and B(C6F5)3 (46 mg, 0.089
mmol) were combined in a dry vial. Subsequent addition of
benzene (2 mL) resulted in a heterogeneous solution, which
grew clear within 1 min. After the mixture was stirred for 30
min, the solvent was removed in vacuo and the residue was
washed with hexanes (56 mg, 89%). 1H NMR (C6D6): δ 6.41
(s, 5H, C5H5), 0.94 (d, 27H, J P-H ) 6 Hz, (CH3)3-C-). 13C{1H}
NMR (C6D6): δ 148.0 (dd, J C-F ) 220 Hz, J C-F ) 30 Hz, C6F5
(o-C)), 140.6 (dd, J C-F ) 240 Hz, J C-F ) 15 Hz, C6F5 (p-C)),
140.1 (s, C6F5 (ipso-C)), 136.8 (ddd, J C-F ) 260 Hz, J C-F ) 30
Hz, J C-F ) 15 Hz, C6F5 (m-C)), 112.5 (s, C5H5), 39.9 (d, J P-C
)

Zirconium Phosphinimide Complexes
Organometallics, Vol. 20, No. 21, 2001 4427
F igu r e 1. ORTEP drawing of 1. Thermal ellipsoids at the
30% level are shown; hydrogen atoms have been omitted
for clarity. Selected bond distances (Å) and angles (deg):
Zr(1)-N(1) ) 1.902(5), Zr(1)-Cl(1) ) 2.410(2), Zr(1)-Cl-
(2) ) 2.418(2), P(1)-N(1) ) 1.588(5); N(1)-Zr(1)-Cl(1) )
105.42(18), N(1)-Zr(1)-Cl(2) ) 103.27(18), Cl(1)-Zr(1)-
Cl(2) ) 105.02(13), P(1)-N(1)-Zr(1) ) 174.8(4).
statistically significant change over the duration of the data
collections. An empirical absorption correction based on re-
dundant data was applied to each data set. Subsequent
solution and refinement was performed using the SHELXTL
solution package.
St r u ct u r e Solu t ion a n d R efin em en t . Non-hydrogen
atomic scattering factors were taken from the literature
tabulations.14 The heavy-atom positions were determined using
direct methods. The remaining non-hydrogen atoms were
located from successive difference Fourier map calculations.
The refinements were carried out by using full-matrix least-
squares techniques on F, minimizing the function ω(|Fo| -
|Fc|)2, where the weight ω is defined as 4Fo2/2σ(Fo2) and Fo and
Fc are the observed and calculated structure factor amplitudes.
For noncentrosymmetric space groups, the correct enantio-
morphic was confirmed by data inversion and refinement. In
the final cycles of each refinement, all non-hydrogen atoms
were assigned anisotropic temperature factors. Carbon-bound
hydrogen atom positions were calculated and allowed to ride
on the carbon to which they are bonded, assuming a C-H bond
length of 0.95 Å. Hydrogen atom temperature factors were
fixed at 1.10 times the isotropic temperature factor of the
carbon atom to which they are bonded. The hydrogen atom
contributions were calculated but not refined. The final values
of refinement parameters are given in Table 1. Positional
parameters, hydrogen atom parameters, thermal parameters,
and bond distances and angles have been deposited as Sup-
porting Information.
Resu lts a n d Discu ssion
Zirconium phosphinimide complexes are readily pre-
pared under ambient conditions via the reaction of
[CpZrCl3]n or Cp*ZrCl3 with the appropriate trialkyl-
phosphinimide lithium salt (R3PNLi). In this manner,
the compounds CpZr(NP-t-Bu3)Cl2 (1) and Cp*Zr(NPR3)-
Cl2 (R ) i-Pr (2), t-Bu (3)) were obtained in good yields.
While spectroscopic data were consistent with these
formulations, X-ray crystallographic data confirmed the
pseudo-tetrahedral geometry of the Zr coordination
spheres in 1 and 2 (Figures 1 and 2). In both cases the
P-N-Zr angles were approaching linearity, being
(14) Cromer, D. T.; Mann, J . B. Acta Crystallogr., Sect. A 1968, A24,
321-324.

4428 Organometallics, Vol. 20, No. 21, 2001
Yue et al.
F igu r e 3. ORTEP drawing of 6. Thermal ellipsoids at the
30% level are shown; hydrogen atoms have been omitted
for clarity. Selected bond distances (Å) and angles (deg):
P(1)-N(1) ) 1.574(2), Zr(1)-N(1) ) 1.955(2), Zr(1)-C(23)
) 2.258(4), Zr(1)-C(24) ) 2.265(4); N(1)-Zr(1)-C(23) )
104.4(2), N(1)-Zr(1)-C(24) ) 103.8(2), P(1)-N(1)-Zr(1) )
168.5(2).
F igu r e 2. ORTEP drawing of 2. Thermal ellipsoids at the
30% level are shown; hydrogen atoms have been omitted
for clarity. Selected bond distances (Å) and angles (deg):
Zr(1)-N(1) ) 1.926(7), Zr(1)-Cl(1) ) 2.581(2), Zr(1)-Cl-
(2) ) 2.559(3), P(1)-N(1) ) 1.569(7); P(1)-N(1)-Zr(1) )
175.2(4), Cl(2)-Zr(1)-Cl(1) ) 94.70(10), N(1)-Zr(1)-Cl-
(1) ) 104.7(2), N(1)-Zr(1)-Cl(2) ) 104.0(2).
174.8(4) and 175.2(4)° in 1 and 2, respectively. These
are much larger than those reported for the related
dimeric ([Zr2Cl4(NPMe3)4(µ-HNPMe3)]) (159.3(2), 155.6-
(2)°)15 and trimeric ([Zr3Cl6(NPMe3)5]+) (132.9(7), 126.1-
(6)°)16 species. The P-N bond distances of 1.588(5) and
1.569(7) Å, respectively, are typical of those found in
other group IV phosphinimide complexes.17 The Zr-N
bond distances of 1.902(5) and 1.926(7) Å in 1 and 2,
respectively, are significantly shorter than the Zr-N
bond distances found in the dimeric and trimeric species
(1.95(2)-2.27(9) Å).15-17 This suggests some degree of
Zr-N multiple bond character.
A series of derivatives are readily obtained via alky-
lation or arylation of the above dihalide precursors. For
example, the dimethyl derivatives CpZr(NP-t-Bu3)Me2
(4) and Cp*Zr(NPR3)Me2 (R ) i-Pr (5), t-Bu (6)) were
readily isolated in high yields via reaction of the dihalide
precursor with a methyl Grignard reagent. Spectro-
scopic data were consistent with dimethylation, and this
was confirmed crystallographically in the case of 6
(Figure 3). The P-N-Zr angle (168.5(2)°), P-N bond
distance (1.574(2) Å), and Zr-N bond distance (1.955-
(2) Å) in 6 is a reflection of a slightly lesser degree of
Zr-N multiple-bond character, presumably arising from
the presence of the electron-donating methyl groups.
In a similar synthetic route, the aryl derivatives CpZr-
(NP-t-Bu3)Ph2 (7) and Cp*Zr(NPR3)Ph2 (R ) i-Pr (8),
t-Bu (9)) were obtained in 79-84% yield via reaction of
the dichloride precursors with a phenyl Grignard re-
agent. Single crystals of 9 were crystallographically
characterized (Figure 4). The metric parameters were
similar to those observed for 6. Similar alkylation of 1
with benzyl Grignard or (trimethylsilyl)methyl Grignard
reagents afford the species CpZr(NP-t-Bu3)Bn2 (10) and
CpZr(NP-t-Bu3)(CH2SiMe3)2 (11), respectively.
F igu r e 4. ORTEP drawing of one of the two molecules in
the asymmetric unit of 9. Thermal ellipsoids at the 30%
level are shown; hydrogen atoms have been omitted for
clarity. Selected bond distances (Å) and angles (deg): Zr-
(1)-N(1) ) 1.922(4), Zr(1)-C(29) ) 2.251(5), Zr(1)-C(23)
) 2.268(4), P(1)-N(1) ) 1.551(4); N(1)-Zr(1)-C(29) )
104.16(17), N(1)-Zr(1)-C(23) ) 102.38(17), C(29)-Zr(1)-
C(23) ) 105.11(18), P(1)-N(1)-Zr(1) ) 168.2(2).
Reactions of allyl Grignard reagent with 2 and 3 gave
complexes of the formulation Cp*Zr(NPR3)(allyl)2 (R )
i-Pr (12), t-Bu (13)) in 71 and 73% yields, respectively.
1
The H NMR spectra at 25 °C for complexes 12 and 13
clearly showed a quintet and doublet attributable to the
methine and methylene portions of symmetrically bound
allyl fragments, inferring bis-η3 binding. When the
temperature is lowered to -80 °C, these resonances
simply broadened, hinting that allyl group interconver-
sion between η1- and η3-bound forms may be occurring
rapidly. The X-ray structure of complex 13 revealed that
in the solid state, both η1- and η3-bound allyl moieties
are present (Figure 5). Thus, the coordination sphere
of the chiral Zr center is comprised of the η5-penta-
methylcyclopentadienyl ligand, the phosphinimide ligand,
and the two differently bonded allyl groups in a pseudo-
tetrahedral geometry. One allyl group (C(26)-C(27)-
C(28)) is bound solely through C(26) (Zr-C ) 2.378(4)
Å), while the second is η3-bound, with Zr-C distances
of 2.488(6), 2.543(6), and 2.378(4) Å.
(15) Stahl, M. M.; Faza, N.; Massa, W.; Dehnicke, K. Z. Anorg. Allg.
Chem. 1997, 623, 1855-1856.
(16) Gru¨n, M.; Weller, F.; Dehnicke, K. Z. Anorg. Allg. Chem. 1997,
623, 224.
(17) Dehnicke, K.; Krieger, M.; Massa, W. Coord. Chem. Rev. 1999,
182, 19-65.

Zirconium Phosphinimide Complexes
Organometallics, Vol. 20, No. 21, 2001 4429
F igu r e 5. ORTEP drawing of 13. Thermal ellipsoids at
the 30% level are shown; hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles
(deg): Zr(1)-N(1) ) 1.976(2), Zr(1)-C(23) ) 2.490(5), Zr-
(1)-C(24) ) 2.488(6), Zr(1)-C(25) ) 2.543(6), Zr(1)-C(26)
) 2.378(4), P(1)-N(1) ) 1.588(2), C(23)-C(24) ) 1.358-
(13), C(24)-C(25) ) 1.165(13), C(26)-C(27) ) 1.440(7),
C(27)-C(28) ) 1.163(9); P(1)-N(1)-Zr(1) ) 173.56(16),
N(1)-Zr(1)-C(23) ) 94.20(13), N(1)-Zr(1)-C(24) ) 107.7-
(4), N(1)-Zr(1)-C(25) ) 118.8(2), N(1)-Zr(1)-C(26) )
92.27(12).
F igu r e 6. ORTEP drawing of 15. Thermal ellipsoids at
the 30% level are shown; hydrogen atoms have been
omitted for clarity. Selected bond distances (Å): Zr(1)-N(1)
) 1.976(2), Zr(1)-Cl(1) ) 2.5070(8).
The “mixed-ring” complexes Cp*Zr(NPR3)(Cp)Cl (R )
i-Pr (14), t-Bu (15)) were also prepared cleanly from the
reaction of sodium cyclopentadienide and 2 or 3, respec-
tively. The proposed η5 coordination of both the penta-
methylcyclopentadienyl and the cyclopentadienyl ligands
was supported by spectroscopic data and confirmed
crystallographically in the case of compound 15 (Figure
6).
Reaction of the compounds Cp*Zr(NPR3)Cl2 (R ) i-Pr
(2), t-Bu (3)) with Mg powder in THF resulted in a color
change to dark blue. Subsequent addition of 1 equiv of
2,3-dimethyl-1,3-butadiene afforded, after 12 h of stir-
ring and typical workup, a new orange species formu-
lated as Cp*Zr(NPR3)(CH2C(CH3)C(CH3)CH2) (R ) i-Pr
(16), t-Bu (17)) in approximately 75% isolated yield.
Each of these species exhibited a single resonance in
the 31P{1H} NMR spectra, as was expected. Similarly,
the 1H and 13C{1H} NMR data were also consistent with
the above formulations. Nonetheless, a number of
possible isomers of these products are conceivable.18,19
These include cis and trans conformations of the buta-
diene, in addition to the prone (A) and supine (B)
F igu r e 7. ORTEP drawing of 16. Thermal ellipsoids at
the 30% level are shown; hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles
(deg): Zr(1)-N(1) ) 1.982(3), P(1)-N(1) ) 1.564(3), Zr(1)-
C(11) ) 2.282(3), Zr(1)-C(12) ) 2.533(3), Zr(1)-C(13) )
2.538(3), Zr(1)-C(14) ) 2.288(3), C(11)-C(12) ) 1.454(5),
C(12)-C(13) ) 1.383(5), C(13)-C(14) ) 1.455(5); C(11)-
Zr(1)-C(14) ) 80.05(14), P(1)-N(1)-Zr(1) ) 173.52(17).
F igu r e 8. ORTEP drawing of 17. Thermal ellipsoids at
the 30% level are shown; hydrogen atoms have been
omitted for clarity. Selected bond distances (Å) and angles
(deg): Zr(1)-N(1) ) 1.996(4), P(1)-N(1) ) 1.576(4), Zr(1)-
C(23) ) 2.258(6), Zr(1)-C(24) ) 2.638(6), Zr(1)-C(25) )
2.642(5), Zr(1)-C(26) ) 2.269(5), C(23)-C(24) ) 1.462(9),
C(24)-C(25) ) 1.390(9), C(25)-C(26) ) 1.476(8); C(23)-
Zr(1)-C(26) ) 80.5(2), P(1)-N(1)-Zr(1) ) 169.3(3).
isomers, which differ only with respect to the orientation
of the butadiene ligand in relation to the pentamethyl-
cyclopentadienyl and phosphinimide ligands. At ambi-
ent temperature, two doublets of equal intensity were
1
observed in the H NMR spectra of 16 and 17 and were
attributed to the terminal CH2 of the diene. The lower
and higher field resonances of these were assigned to
the syn and anti protons, respectively. This is consistent
with shielding of the anti protons by the proximal
pentamethylcyclopentadienyl ligand.
While the above NMR data were consistent with the
presence of only one isomer in solution, the precise
nature of these Zr compounds was unambiguously
confirmed via X-ray crystallographic studies (Figures
7 and 8). In both cases, the structural data reveal that
the coordination of the Zr center is comprised of penta-
methylcyclopentadienyl, phosphinimide, and cis-buta-
diene ligands, such that the butadiene substituents are
(18) Yasuda, H.; Tatsumi, K.; Nakmura, A. Acc. Chem. Res. 1985,
18, 120-126.
(19) Yasuda, H.; Nakamura, A. Angew. Chem., Int. Ed. Engl. 1987,
26, 723-742.

4430 Organometallics, Vol. 20, No. 21, 2001
Yue et al.
oriented away from the pentamethylcyclopentadienyl
ligand: that is, in a supine conformation. The Zr-C
distances for the R- and â-butadiene carbons average
2.285(3) and 2.534(3) Å in 16, while the corresponding
averages are 2.640(5) and 2.263(6) Å in 17, respectively.
The butadiene ligand clearly makes a closer approach
to the Zr in 16 than in 17, consistent with changes in
the steric demands and donor abilities of the phosphin-
imide ligands. However, the corresponding Zr-N dis-
tances appear to be dominated by steric effects, as the
Zr-N distance in 16 (1.982(3) Å) is slightly longer than
that in 17 (1.996(4) Å). It is also noteworthy that the
C-C distances of the central bond of the butadiene
ligands are 1.383(5) and 1.390(9) Å in 16 and 17,
respectively. In addition, the dihedral angle between the
planes containing the four carbons of the butadiene
ligand and that consisting of Zr and the two R-carbons
are 116.5 and 108.7° for 16 and 17, respectively. These
data infer that the Zr-butadiene interaction is best
described as a σ2,π-bonded η4 interaction. These struc-
tural parameters of the butadiene moieties are typical
of those seen for a number of other early metal buta-
diene complexes.18,19
cluded analysis and the determination of associated
kinetic and thermodynamic data.
Zw itter ion ic Com p lexes. The reactions of 17 with
B(C6F5)3 in toluene results in the formation of the yellow
betaine complex Cp*Zr(NP-t-Bu3)(CH2C(CH3)C(CH3)-
CH2B(C6F5)3) (18) in 71% yield. The 1H NMR resonances
at δ 2.21 and 0.59 are attributable to methylene groups
bonded to the formal cationic Zr and anionic B centers,
respectively. The 19F NMR spectrum exhibits the in-
equivalence of the 15 fluorine environments. Given that
cis-diene complexes are known to react with B(C6F5)3
to give dienylborate species with a linear Zr-C-B
dipole, we attribute the observed inequivalence to
inhibited rotation about the B-C bonds. This contrasts
with the trans-butadiene complex Cp2Zr(CH2CHCH-
CH2B(C6F5)3), where Karl et al.26 observed 15 inequiva-
lent 19F NMR resonances with an interaction of an ortho
fluorine with the cationic Zr, resulting in the observation
of one 19F resonance that is dramatically shifted down-
field. In this case, a Zr-F interaction was confirmed
crystallographically (eq 2); however, the precise orienta-
A number of previously characterized metallocene-
butadiene complexes18-25 exhibit fluxional behavior. For
example, Erker et al.23 have observed and determined
the energetics of equilibrium processes involving both
cis-trans isomerization of the butadiene as well as ring
flipping (eq 1). In the case of compounds 16 and 17,
tion of the aryl groups in 18 remains unknown in the
absence of crystallographic data. However, a structur-
ally related half-sandwich species (C5H3(SiMe3)2)Hf-
(C3H5)(CH2CMeCMeCH2B(C6F5)3) has been reported by
Bochmann et al.27 It is worth mentioning that dissolu-
tion of 18 in THF affords the species Cp*Zr(NP-t-Bu3)-
(THF)n(CH2C(CH3)C(CH3)CH2B(C6F5)3) (19). In this
species, THF coordination to Zr presumably results in
an η1 binding mode of the butadienyl-borate, allowing
unrestricted rotation of the borate fragment, as evi-
denced by the presence of only three 19F{1H} NMR
resonances.
Eth ylen e P olym er iza tion . A number of the above
compounds were screened for their potential as catalyst
precursors in ethylene polymerizations. These tests
were performed either using the known route of com-
bining early metal dichloride complexes with excess
methylalumoxane (MAO) or employing corresponding
dialkyl species and either MAO or trityl tetrakis-
(pentafluorophenyl)borate as the activator. Reaction
conditions of 1 atm of ethylene at 25 °C or 33 psig of
ethylene and 30 °C were employed. The nature of the
tests reported herein is tabulated in Table 2. In general,
the compounds described herein are poor ethylene
polymerization catalysts in comparison to the related
Titanium species,2,3 although the activities were in-
creased somewhat under elevated temperatures and
pressures. The cause of this marked difference may be
related to the significantly larger ionic radius of Zr,
variable-temperature 1H NMR studies reveal only a
slight broadening of the resonances attributable to the
butadiene moieties. The dissymmetry of these phos-
phinimide complexes presumably generates a significant
thermodynamic preference for the supine conformation,
thus providing a significant barrier to ring inversion.
While the butadiene fragments are temperature-invari-
ant, the signals arising from the tert-butyl groups in
compounds 17 did show a temperature dependence. At
room temperature, the 1H resonance is the predicted
doublet arising from coupling to phosphorus. Upon
cooling, the resonance broadens and splits into two
peaks in a ratio of 2:1. The coalescence occurs at
approximately -55 °C in each case. These observations
are consistent with restricted rotation about the Zr-N
bond, due to a cogwheel effect of the tert-butylphosphin-
imide and pentamethylcyclopentadienyl groups. It is
noteworthy that we have recently described similar
observations for the species Cp*Ta(NP-t-Bu3)X3 (X ) Cl,
Me).9 The complexity of this fluxional behavior pre-
(20) Kruger, C.; Muller, G. Organometallics 1985, 4, 215-223.
(21) Dorf, U.; Engel, K.; Erker, G. Organometallics 1983, 2, 462-
463.
(22) Erker, G.; Dorf, U.; Benn, R.; Reinhardt, R.-D. J . Am. Chem.
Soc. 1984, 106, 7649-7650.
(23) Erker, G.; Wicher, J .; Engel, K.; Rosenfeldt, F.; Dietrich, W. J .
Am. Chem. Soc. 1980, 102, 6344-6346.
(24) Wreford, S. S.; Whitney, J . F. Inorg. Chem. 1981, 20, 3918-
(26) Karl, J .; Erker, G.; Fohlich, R. J . Am. Chem. Soc. 1997, 119,
11165-11173.
(27) Pindado, G. J .; Thornton-Pett, M.; Bochmann, M. J . Chem. Soc.,
Dalton Trans. 1997, 3115-3127.
3924.
(25) Fujita, K.; Ohnuma, Y.; Yasuda, H.; Tani, H. J . Organomet.
Chem. 1976, 113, 201-213.

Zirconium Phosphinimide Complexes
Organometallics, Vol. 20, No. 21, 2001 4431
Ta ble 2. Eth ylen e P olym er iza tion Da ta
catalyst
time
productivity
precursor cocatalysta (min) (g mmol-1 h-1
)
Mw
Mw/Mn
1b
MAO
MAO
MAO
MAO
MAO
MAO
MAO
MAO
TB
TB
TB
TB
MAO
30.0
60.0
30.0
30.0
60.0
60.0
60.0
60.0
11
100
d
d
43
1
48
87
d
d
181
d
94,300
234,000 67.9
2.6
1c
2b
3b
4b
2c
506,400 41.5
9220
49,900 33.5
3c
3.3
4c
5b
3.00
6b
3.00
3.00
3.00
2.00
16b
132,300
116,353
4.4
2.8
17b
Cp2ZrCl2b
895
F igu r e 9. ORTEP drawing of 21. Thermal ellipsoids at
the 30% level are shown; the methyl carbons and hydrogen
atoms have been omitted for clarity. Selected bond dis-
tances (Å) and angles (deg): Zr(1)-Cl(1) ) 2.495(6), Zr-
(1)-Cl(2) ) 2.583(6), Zr(1)-Cl(3) ) 2.585(6), Zr(1)-Cl(6)
) 3.063(5), Zr(2)-Cl(5) ) 2.581(5), Zr(2)-Cl(6) ) 2.637-
(5), Zr(2)-Cl(3) ) 2.677(5), Zr(1)-C(52) ) 2.197(19), Zr-
(2)-C(51) ) 2.300(19), Zr(2)-C(52) ) 2.33(2), Zr(3)-C(51)
) 2.314(17), Zr(3)-C(52) ) 2.327(16), Zr(3)-Cl(4) ) 2.595-
(6), Zr(3)-Cl(6) ) 2.613(6), Zr(3)-Cl(2) ) 2.694(5), Zr(4)-
C(51) ) 2.177(16), Zr(4)-C(52) ) 2.304(19), Zr(4)-Cl(4) )
2.591(6), Zr(4)-Cl(5) ) 2.619(6); C(52)-Zr(1)-Cl(1) )
140.2(5), C(52)-Zr(1)-Cl(2) ) 82.1(5), Cl(1)-Zr(1)-Cl(2)
) 86.0(2), C(52)-Zr(1)-Cl(3) ) 82.2(5), Cl(1)-Zr(1)-Cl(3)
) 87.3(2), Cl(2)-Zr(1)-Cl(3) ) 146.28(17), C(52)-Zr(1)-
Cl(6) ) 66.4(5), Cl(1)-Zr(1)-Cl(6) ) 73.83(17), Cl(2)-Zr-
(1)-Cl(6) ) 74.10(16), Cl(3)-Zr(1)-Cl(6) ) 72.30(16),
C(51)-Zr(2)-C(52) ) 70.1(6), C(51)-Zr(2)-Cl(5) ) 89.7-
(4), C(52)-Zr(2)-Cl(5) ) 76.3(4), C(51)-Zr(2)-Cl(6) ) 86.0-
(4), C(52)-Zr(2)-Cl(6) ) 73.2(5), Cl(5)-Zr(2)-Cl(6) )
148.77(18), C(51)-Zr(2)-Cl(3) ) 147.2(5), C(52)-Zr(2)-Cl-
(3) ) 77.9(5), Cl(5)-Zr(2)-Cl(3) ) 89.11(17), Cl(6)-Zr(2)-
Cl(3) ) 78.27(17), C(51)-Zr(3)-C(52) ) 69.8(6), C(51)-
Zr(3)-Cl(4) ) 89.5(5), C(52)-Zr(3)-Cl(4) ) 76.1(5), C(51)-
Zr(3)-Cl(6) ) 86.3(5), C(52)-Zr(3)-Cl(6) ) 73.7(5), Cl(4)-
Zr(3)-Cl(6) ) 149.08(17), C(51)-Zr(3)-Cl(2) ) 146.9(4),
C(52)-Zr(3)-Cl(2) ) 77.4(5), Cl(4)-Zr(3)-Cl(2) ) 86.82-
(18), Cl(6)-Zr(3)-Cl(2) ) 80.33(18), C(51)-Zr(4)-C(52) )
72.7(6), C(51)-Zr(4)-Cl(4) ) 92.7(5), C(52)-Zr(4)-Cl(4) )
76.6(5), C(51)-Zr(4)-Cl(5) ) 91.5(5), C(52)-Zr(4)-Cl(5) )
75.9(5), Cl(4)-Zr(4)-Cl(5) ) 149.52(18), Zr(4)-C(51)-Zr-
(2) ) 90.4(6), Zr(4)-C(51)-Zr(3) ) 89.8(6), Zr(2)-C(51)-
Zr(3) ) 93.2(6), Zr(1)-C(52)-Zr(4) ) 164.1(9), Zr(1)-
C(52)-Zr(2) ) 104.6(8), Zr(4)-C(52)-Zr(2) ) 86.7(6), Zr(1)-
C(52)-Zr(3) ) 104.1(7), Zr(4)-C(52)-Zr(3) ) 86.4(6), Zr(2)-
C(52)-Zr(3) ) 92.1(6).
a
Abbreviations: MAO, methylaluminoxane (500 equiv); TB,
b
trityl tetrakis(pentafluorophenyl)borate (1 equiv). Polymeriza-
tions were run at 1 atm pressure of ethylene and 25 °C. c Poly-
merizations were run at 33 psi pressure of ethylene, 30 °C.
Molecular weight data were recorded against polyethylene stan-
d
dards. Too little polymer to determine accurately.
which facilitates deactivation pathways over chain
propagation.
Dea ctiva tion P a th w a ys. Efforts to understand the
deactivation pathway for these zirconium catalysts were
undertaken. Zwitterionic complexes analogous to those
reported for both titanium phosphinimide species2,3,5
and metallocene derivatives28,29 are readily prepared
using the now conventional approach of reaction of an
alkyl-complex with the Lewis acid B(C6F5)3. However,
reaction of 4 with this borane did not yield the expected
zwitterion; rather, the quantitative product of aryl group
transfer CpZr(NP-t-Bu3)(C6F5)2 (20) was formed as
evidenced by multinuclear NMR spectral data. This
interpretation was confirmed by the independent syn-
thesis of 20 from 1 and the Grignard reagent BrMgC6F5.
This observation stands in contrast to the analogous Ti
reaction, which readily affords the zwitterionic species
CpTi(NP-t-Bu3)(CH3)(µ-CH3B(C6F5)3),3 suggesting that
the increase in the metal atom size prompts the
observed alkyl for aryl exchange. Similar C6F5 transfer
reactions have been previously observed.5,30,31 Moreover,
this observation offers an explanation for the markedly
low catalytic activity in comparison with the Ti ana-
logues,3 suggesting a chemical pathway for deactivation
of the catalyst precursor.
In modeling the interaction of the dichloride com-
plexes with MAO, the reaction of 2 with AlMe3 was
studied. Monitoring the 31P NMR spectra for this
reaction indicated the formation of complex mixture of
products. While the nature of these phosphorus-contain-
ing products remains unknown, two Zr-containing prod-
ucts could be recrystallized in very low yields from
reactions under slightly varied conditions. The species
21 and 22 were characterized by NMR and X-ray
methods. Compound 21, obtained from the reaction of
2 with AlMe3 in benzene/hexane, exhibited 1H NMR
data consistent with three pentamethylcyclopentadienyl
ligand environments in a 1:2:1 ratio. X-ray methods
confirmed the formulation of 21 as the Zr4 cluster
(Cp*Zr)4(µ-Cl)5(Cl)(µ-CH)2 (Figure 9). This species is
comprised of four Zr atoms bound to a central methine
carbon (C52). Each of the Zr atoms are bonded to a
pentamethylcyclopentadienyl ligand and two bridging
chloride atoms. One of the Zr atoms has an additional
terminal chloride, while the remaining three Zr atoms
are bridged by an additional methine carbon (C51). The
Zr-Cl distances range from 2.581(5) to 2.677(5) Å for
the bridging chlorides, while the terminal Zr-Cl bond
distance is 2.495(6) Å. There is also a close approach of
Zr(1) to Cl(6) at 3.063(5) Å. The triply bridging methine
carbon is approximately tetrahedral: C-Zr-C angles
and Zr-C distances averaging 91.0(6)° and 2.263(18)
Å, respectively. The geometry about the central carbon
C(52) suggests a trigonal-bipyramidal Zr coordination
sphere, as the Zr(1)-C(52)-Zr(4) angle is 164.1(9)° and
(28) Yang, X.; Stern, C. L.; Marks, T. J . J . Am. Chem. Soc. 1991,
113, 3623.
(29) Bochmann, M.; Lancaster, S. J .; Hursthouse, M. B.; Malik, K.
M. A. Organometallics 1994, 13, 2235.
(30) Scollard, J . D.; McConville, D. M.; Rettig, S. J . Organometallics
1997, 16, 1810.
(31) Woodman, T. J .; Bochmann, M.; Thornton-Pett, M. Chem.
Commun. 2001, 329-330.

4432 Organometallics, Vol. 20, No. 21, 2001
Yue et al.
F igu r e 11. ORTEP drawings of the Zr-C-Cl cores of
compounds (a) 21 and (b) 22.
the remaining Zr-C-Zr angles range from 86.4(6) to
104.6(8)° (Figure 11a).
A similar reaction of 3 with neat AlMe3 in benzene
afforded a similar mixture of reaction products as judged
by 31P NMR spectroscopy. One of these species crystal-
lized from solution. The product 22 exhibits two 1H
methine resonances at 14.44 and 9.34 ppm in a ratio of
2:1, as well as four resonances attributable to pentam-
ethylcyclopentadienyl methyl groups in a ratio of 1:1:
2:1. 1H-13C 2D spectra confirmed the correlation of the
1H resonances at 14.44 and 9.34 ppm with the 13C
resonances at 372.9 and 168.3 ppm, respectively. X-ray
crystallography confirmed the formulation of 22 as
(Cp*Zr)5(µ-Cl)6(µ-CH)3 (Figure 10). This species, like 21,
is a Zr cluster. Compound 22 is comprised of five Cp*Zr
fragments about a central methine carbon atom. The
Zr atoms form a square-based pyramid about the central
carbon (C(51)), and the basal Zr atoms are bridged by
four chloride atoms below the plane. Two chlorine atoms
and two pseudo-tetrahedral methine carbons above the
plane bridge the axial Zr center. Bridging Zr-Cl dis-
tances are similar to those seen in 21, ranging from
2.507(3) to 2.774(2) Å for the basal Zr atoms and average
2.890(4) Å for the axial Zr atom. The geometries about
the triply bridging methine carbons in 22 are similar
to that seen in 21. The geometry about the central
carbon is that of a distorted octahedron (Figure 11b),
with Zr-C distances ranging from 2.324(10) to 2.412-
(9) Å. The coplanar Zr atoms adopt a pseudo-square-
planar arrangement about the C with Zr(2)-C(51)-
Zr(3) and Zr(1)-C(51)-Zr(5) angles of 166.4(4) and
176.9(5)°, respectively. Zr(4) is approximately orthogo-
nal to these Zr atoms, with Zr-C-Zr angles from 83.0-
(3) to 103.6(3)°. The located and refined hydrogen atom
occupies the axial position approximately trans to Zr-
(4) (H-C-Zr ) 174.4°). The distortion in the geometry
about the central carbon is presumably a ramification
of the molecular dissymmetry and the steric crowding
of five Cp*Zr fragments. It is noteworthy that the
related C-H bond activation products [(Cp*Zr)3Al6Me8-
(CH2)2(CH)4(CH)], {[(C5Me4Et)Zr]3Al6Me8(CH2)2(CH)4-
(CH)}, and [(Cp*Hf)3Al6Me8(CH2)2(CH)4(CH)] have been
isolated in low yield by Roesky et al. from the reactions
of Cp′ZrF3 with varying equivalents of AlMe3.32,33
F igu r e 10. ORTEP drawings of 22. Thermal ellipsoids at
the 30% level are shown; hydrogen atoms have been
omitted for clarity. The views (a) and (b) are approximately
orthogonal; methyl carbons are omitted for clarity in (b).
Selected bond distances (Å) and angles (deg): Zr(1)-C(51)
) 2.349(8), Zr(1)-Cl(4) ) 2.507(3), Zr(1)-Cl(1) ) 2.536-
(3), Zr(1)-Cl(3) ) 2.607(3), Zr(1)-Cl(2) ) 2.647(3), Zr(2)-
C(53) ) 2.186(9), Zr(2)-C(51) ) 2.412(9), Zr(2)-Cl(2) )
2.722(3), Zr(2)-Cl(1) ) 2.746(3), Zr(3)-C(52) ) 2.164(9),
Zr(3)-C(51) ) 2.410(10), Zr(3)-Cl(6) ) 2.545(2), Zr(3)-
Cl(4) ) 2.774(2), Zr(3)-Cl(3) ) 2.780(2), Zr(4)-C(52) )
2.235(9), Zr(4)-C(53) ) 2.267(10), Zr(4)-C(51) ) 2.324-
(10), Zr(4)-Cl(3) ) 2.863(2), Zr(4)-Cl(2) ) 2.917(3), Zr-
(5)-C(52) ) 2.311(9), Zr(5)-C(53) ) 2.331(9), Zr(5)-Cl(5)
) 2.660(3), Zr(5)-Cl(6) ) 2.690(2); C(51)-Zr(1)-Cl(4) )
79.3(2), C(51)-Zr(1)-Cl(1) ) 78.1(2), Cl(4)-Zr(1)-Cl(1) )
94.93(9), C(51)-Zr(1)-Cl(3) ) 76.2(2), Cl(4)-Zr(1)-Cl(3)
) 86.28(8), Cl(1)-Zr(1)-Cl(3) ) 153.58(8), C(51)-Zr(1)-
Cl(2) ) 75.1(2), Cl(4)-Zr(1)-Cl(2) ) 154.22(8), Cl(1)-Zr-
(1)-Cl(2) ) 82.87(9), Cl(3)-Zr(1)-Cl(2) ) 84.72(8), C(53)-
Zr(2)-C(51) ) 74.9(3), Cl(5)-Zr(2)-Cl(2) ) 149.56(8),
C(53)-Zr(2)-Cl(1) 147.9(3), C(51)-Zr(2)-Cl(1) ) 73.1(2),
Cl(2)-Zr(2)-Cl(1) ) 77.73(8), C(52)-Zr(3)-C(51) ) 74.8-
(3), C(52)-Zr(3)-Cl(6) ) 90.4(2), C(51)-Zr(3)-Cl(6) ) 79.2-
(2), C(52)-Zr(3)-Cl(4) ) 147.9(2), C(51)-Zr(3)-Cl(4) )
73.1(2), Cl(6)-Zr(3)-Cl(4) ) 84.55(8), C(52)-Zr(3)-Cl(3)
) 91.3(2), C(51)-Zr(3)-Cl(3) ) 71.9(2), Cl(6)-Zr(3)-Cl(3)
) 149.53(8), Cl(4)-Zr(3)-Cl(3) ) 78.07(8), C(52)-Zr(4)-
C(53) ) 92.3(3), C(52)-Zr(4)-C(51) ) 75.3(3), C(53)-Zr-
(4)-C(51) ) 75.2(3), C(52)-Zr(4)-Cl(3) ) 87.7(2), C(53)-
Zr(4)-Cl(3) ) 145.6(3), C(51)-Zr(4)-Cl(3) ) 71.5(2), C(52)-
Zr(4)-Cl(2) ) 145.0(3), C(53)-Zr(4)-Cl(2) ) 85.3(2), C(51)-
Zr(4)-Cl(2) ) 70.3(2), Cl(3)-Zr(4)-Cl(2) ) 75.53(7), C(52)-
Zr(5)-C(53) ) 88.8(3), C(52)-Zr(5)-C(51) ) 70.0(3), C(53)-
Zr(5)-C(51) ) 70.1(3), C(52)-Zr(5)-Cl(5) ) 144.1(3), C(53)-
Zr(5)-Cl(5) ) 84.5(2), C(51)-Zr(5)-Cl(5) ) 74.6(2), C(52)-
Zr(5)-Cl(6) ) 83.8(2), C(53)-Zr(5)-Cl(6) ) 144.0(3), C(51)-
Zr(5)-Cl(6) ) 74.3(2), Cl(5)-Zr(5)-Cl(6) ) 81.28(8), Zr(4)-
C(51)-Zr(1) ) 103.6(3), Zr(4)-C(51)-Zr(2) ) 88.4(3), Zr(1)-
C(51)-Zr(2) ) 97.3(3), Zr(4)-C(51)-Zr(3) ) 87.2(3), Zr(1)-
C(51)-Zr(3) ) 96.2(3), Zr(2)-C(51)-Zr(3) ) 166.4(4), Zr(4)-
C(51)-Zr(5) ) 79.5(3), Zr(1)-C(51)-Zr(5) ) 176.9(5), Zr(2)-
C(51)-Zr(5) ) 83.5(3), Zr(3)-C(51)-Zr(5) ) 83.0(3), Zr(3)-
C(52)-Zr(4) ) 95.8(4), Zr(3)-C(52)-Zr(5) ) 94.3(4), Zr(4)-
C(52)-Zr(5) ) 86.4(3), Zr(2)-C(53)-Zr(4) ) 95.7(4), Zr(2)-
C(53)-Zr(5) ) 93.7(4), Zr(4)-C(53)-Zr(5) ) 85.2(3).
The compounds 21 and 22 were obtained in poor yield
from the reactions of 3 with AlMe3, and thus it cannot
be assumed that these products represent the major
reaction pathways. Nonetheless, these compounds do
suggest avenues by which catalyst-cocatalyst interac-
(32) Herzog, A.; Roesky, H. W.; J ager, F.; Steiner, A.; Noltemeyer,
M. Organometallics 1996, 15, 909-917.
(33) Herzog, A.; Roesky, H. W.; Zak, Z.; Noltemeyer, M. Angew.
Chem., Int. Ed. Engl. 1994, 33, 967-968.

Zirconium Phosphinimide Complexes
Organometallics, Vol. 20, No. 21, 2001 4433
tions can lead to deactivation. First, phosphinimide
ligand abstraction clearly occurs in the formation of 21
and 22, and thus this may also occur upon reaction of
Zr-phosphinimide complexes with Al-based cocatalysts.
This stands in contrast to the related Ti complexes,
where phosphinimide ligands have been shown to bridge
Ti and Al centers.7,10 Second, methyl transfer from Al
to Zr followed by C-H bond activation is clearly
indicated by the isolation of 22 and 23. Thus, C-H bond
activation could be one route for catalyst deactivation.
Recent studies of Ti-Al-carbide species derived from
Ti-phosphinimide complex reactions with AlMe3 sug-
gest a similar proposition.7,10
Ack n ow led gm en t . Financial support from the
NSERC of Canada and NOVA Chemicals Corp. is
gratefully acknowledged.
Su p p or tin g In for m a tion Ava ila ble: Figures giving NMR
data and electronic files giving crystallographic data, in CIF
format. This material is available free of charge via the
Internet at http://pubs.acs.org.
OM010433Q