Phosphinimide complexes with pendant hemilabile donors: Synthesis, structure and ethylene polymerization activity

Article abstract of DOI:10.1039/b817959j

The phosphines tBu₂P(CH₂)₃ECH ₂Ph (E = O (1), S (2)) converted to the corresponding phosphinimines (Me₃SiN)PtBu₂(CH₂)₃ECH ₂Ph, E = O (3), S (4)) which were

Full text of DOI:10.1039/b817959j

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www.rsc.org/dalton | Dalton Transactions
Phosphinimide complexes with pendant hemilabile donors: synthesis,
structure and ethylene polymerization activity†
Krishan Yadav, Jenny S. J. McCahill, Guangcai Bai and Douglas W. Stephan*‡
Received 13th October 2008, Accepted 25th November 2008
First published as an Advance Article on the web 23rd January 2009
DOI: 10.1039/b817959j
The phosphines tBu2P(CH2)3ECH2Ph (E = O (1), S (2)) converted to the corresponding
phosphinimines (Me3SiN)PtBu2(CH2)3ECH2Ph, E = O (3), S (4)) which were used to prepared the
titanium complexes Cp¢TiCl2NPtBu2(CH2)3ECH2Ph, (E = O, Cp¢ = Cp (5), Cp* (6); E = S, Cp¢ = Cp
(7), Cp* (8)). These species were subsequently methylated to the corresponding dimethyl-derivatives
(9)–(12). Activation of (9)–(12) with both B(C6F5)3 and [Ph3C][B(C6F5)4] was studied. For example, the
[CpTiMe(NPtBu2(CH2)3OCH2Ph)][MeB(C6F5)3] (13) reacted with THF to give [CpTiMe(THF)-
(NPtBu2(CH2)3OCH2Ph)][MeB(C6F5)3] (14). Similar reactions gave the stable ion pairs [Cp¢TiMe(NP-
tBu2(CH2)3XCH2Ph)][MeB(C6F5)3] (X = O, Cp¢ = Cp*, (15); X = S Cp¢ = Cp, (16), Cp*(17)) and
[Cp¢TiMe(NPtBu2(CH2)3XCH2Ph)][B(C6F5)4] (X = O, Cp¢ = Cp, (18); Cp*(19); X = S, Cp¢ = Cp, (20),
Cp* (21)). The dihalide complexes (5)–(8), activated with MAO, proved to be ethylene polymerization
catalysts of moderate activities. The dialkyl titanium complexes (9)–(12) activated with B(C6F5)3 or
[Ph3C][B(C6F5)4], gave catalysts that exhibited substantially higher activity and high molecular weight
polyethylene. Polymerization at 60 ◦C rather than 30 ◦C significantly increased activity as well. The
impact of the hemilabile donor with respect to catalyst activity is discussed. Crystallographic studies of
(5) and (6) are reported.
Such ligands will provide a stabilizing donor for reactive cationic
Introduction
catalysts and yet be labile in the presence of substrate olefin.
Recently, Hessen and coworkers have employed a hemilabile ligand
to develop the first ethylene trimerization catalyst50–52 in which a
pendant arene fragment on a cyclopentadienyl ligand stabilizes
a cationic titanium(II) intermediate (Scheme 1). Employing a
related strategy we have shown that pendant arene substituents on
phosphinimide ligands can act as hemilabile ligands (Scheme 1)34,53
to stabilize reduced Ti centers and coordinatively unsaturated
Ti(IV) cations. In this manuscript we further explore hemilabile
ligand systems. To this end, we noted earlier literature describing
transition metal compounds featuring hemilabile phosphorus–
oxygen (P,O) ligands.54 Herein, we target new Ti-complexes
featuring a tethered heteroatom donor on a phosphinimide ligand.
Such systems are expected to exhibit hemilabile behavior offering
a strategy for stabilization of reactive cationic species. The impact
on the utility of these species in ethylene polymerization activity
is also probed.
The study of homogeneous catalysts for olefin polymerization
has been on-going around the globe for more than 25 years.1–7
A great deal of research has focused on metallocene systems with
particular reference to ligand design strategies allowing the control
of the stereo-regularity of the resulting a-olefin polymers.8–11
Catalyst derived that incorporate non-cyclopentadienyl ligand
systems have also garnered much attention. One of particular
note is the “constrained geometry catalysts”12–15 derived from
the linked amide-cyclopentadienyl ligand introduced by Bercaw
and coworkers.16 In the 1990s titanium complexes containing
bulky bis-amido-chelate ligands were shown to give rise to living
catalysts as described by McConville and coworkers.17–20 More
recently, the “FI” catalysts developed by researchers at Mitsui have
drawn considerable attention.21–25 In 1999, we reported the utility
of phosphinimide ligands in the development of highly active
olefin polymerization catalysts under commercial conditions.26–28
Since those early reports, efforts to understand the structure–
activity relationship,29–43 and the mechanisms of deactivation44–49
of phosphinimide-catalyst systems have been extensively
studied.
In targeting the development of catalysts that are effective at
even higher temperature, we targeted hemilabile ligand systems.
Department of Chemistry & Biochemistry, University of Windsor, Windsor,
Ontario, Canada N9B3P4. E-mail: dstephan@chem.utoronto.ca
† CCDC reference numbers 702186–702187. For crystallographic data in
CIF or other electronic format see DOI: 10.1039/b817959j
‡ Current address: Department of Chemistry, University of Toronto, 80
St. George St. Toronto, Ontario, Canada M5S 3H6.
Scheme 1 Examples of pendant arene stabilized Ti-complexes.
1636 | Dalton Trans., 2009, 1636–1643
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(m, 2H, CH2CH2CH2); 1.51 (m, 2H, PCH2); 1.02 (d, 18H, tBu,
Experimental section
1
JH-H = 13 Hz); 0.31 (s, 9H, SiMe3). 13C{ H} NMR (C6D6): 139.2–
General considerations
127.5 (Ph); 72.9 (s, PhCH2O); 71.1 (d, OCH2CH2, JP-C = 11 Hz);
36.7 (d, tBu, JP-C = 63 Hz); 27.0 (s, tBu); 24.9 (s, CH2CH2CH2);
19.2 (d, PCH2, JP-C = 60 Hz); 4.8 (s, SiMe3). Anal. Calc¢d for
C21H40NPSiO: C, 66.10, N, 3.67, H, 10.57; found: C, 66.01, N, 3.33,
All preparations were performed under an atmosphere of dry O2-
free N2 employing either Schlenk-line techniques or a Vacuum
Atmospheres inert atmosphere glovebox. Solvents were purified
employing Grubbs-type column systems manufactured by Inno-
vative Technologies or were distilled from the appropriate drying
1
H, 10.31%. (4): Yield: 3.24 g, 78%. 31P{ H} NMR (C6D6): 26.8.
1H NMR (C6D6): 7.28–7.07 (Ph); 3.56 (s, 2H, PhCH2S); 2.38 (t,
2H, SCH2CH2, JH-H = 7 Hz); 1.82 (m, 2H, CH2CH2CH2); 1.42 (m,
2H, PCH2); 1.05 (d, 18H, tBu, JH-H = 13 Hz); 0.32 (s, 9H, SiMe3).
agents under N2. 1H and 13C{ H} NMR spectra were recorded on
1
Bruker Avance 300 and 500 spectrometers. Deuterated benzene,
toluene and methylene chloride were purchased from Cambridge
Isotopes Laboratories, vacuum distilled from the appropriate
drying agents and freeze–pump–thaw degassed (3 times). Trace
amounts of protonated solvents were used as references, and
1
13C{ H} NMR (C6D6): 138.6–126.7 (Ph); 35.6 (s, PhCH2S); 32.9
(d, SCH2CH2, JP-C = 13 Hz); 29.6 (d, tBu, JP-C = 13 Hz); 27.1 (s,
tBu); 24.1 (s, CH2CH2CH2); 20.4 (d, PCH2, JP-C = 12 Hz); 4.7 (s,
SiMe3). Anal. Calc¢d for C21H40NPSiS: C, 63.42, N, 3.52, H, 10.14;
found: C, 63.40, N, 3.43, H, 9.98%.
1
1H and 13C{ H} NMR chemical shifts are reported relative to
1
1
SiMe4. 31P{ H}, 11B{ H}, and 19F NMR spectra were referenced
to external 85% H3PO4, BF3·Et2O, and CFCl3, respectively.
Combustion analyses were performed at the University of Windsor
Chemical Laboratories employing a Perkin Elmer CHN Analyzer.
High temperature GPC data were provided by the technical staff
at NOVA Chemicals Corporation.
Synthesis of Cp¢TiCl2NPtBu2(CH2)3ECH2Ph, (E = O, Cp¢ = Cp
(5), Cp* (6); E = S Cp¢ = Cp (7), Cp* (8)). These compounds
were prepared in a similar fashion and thus only one preparation is
detailed. A solution of (4) (0.30 g, 0.786 mmol) in 5 mL of toluene
was added dropwise at room temperature to a solution of CpTiCl3
(0.184 g, 0.825 mmol) in toluene. The yellow solution was then
refluxed overnight to give a clear orange solution. The solvent was
removed in vacuo to yield a dark orange oil. Treatment of the oil
with hexanes, and subsequent decanting gave a yellow solid. The
Synthesis of tBu2P(CH2)3ECH2Ph (E = O (1); E = S (2)).
These compounds were prepared in a similar fashion and thus
only one preparation is detailed. A solution of Br(CH2)3OCH2Ph
(0.696 g, 3.04 mmol) in 10 mL THF was added dropwise at
-35 ◦C to a solution of tBu2PLi (0.462 g, 3.04 mmol) in 20 mL of
THF. Following addition of the bromoether, there was an almost
immediate color change from deep yellow to very pale yellow. The
1
solid was dried in vacuo. (5): Yield: 0.289 g, 73%. 31P{ H} NMR
1
(C6D6): 39.9. H NMR (C6D6): 7.30–7.09 (Ph); 6.46 (s, 5H, Cp);
4.35 (s, 2H, PhCH2O); 3.34 (t, 2H, OCH2CH2, JH-H = 7 Hz); 2.12
◦
(m, 2H, CH2CH2CH2); 1.59 (m, 2H, PCH2); 0.99 (d, 18H, tBu,
solution was stirred and allowed to warm to 25 C. The solvent
1
JH-H = 14 Hz). 13C{ H} NMR (C7D8): 138.7–119.4 (Ph); 118.2 (s,
was removed in vacuo to afford a white and yellow solid. The
yellow residue was extracted with 10 mL of toluene, filtered and
the solvent removed in vacuo to afford a yellow oil. Yield: 0.814 g,
Cp); 72.7 (s, PhCH2O); 69.9 (d, OCH2CH2, JP-C = 19 Hz); 38.3
(d, tBu, JP-C = 62 Hz); 26.4 (s, tBu); 24.5 (s, CH2CH2CH2); 18.7
(d, PCH2, JP-C = 64 Hz). Anal. Calc¢d for C23H36Cl2NPOTi: C,
56.12, N, 2.85, H, 7.37; found: C, 56.01, N, 2.69, H, 7.25%. (6):
1
91%. (1): 31P{ H} NMR: 27.0. 1H NMR (C6D6): 7.28–7.07 (Ph);
4.35 (s, 2H, OCH2Ph); 3.46 (t, 2H, OCH2CH2, JH-H = 6 Hz); 1.85
(m, 2H, CH2CH2CH2); 1.42 (m, 2H, PCH2); 1.06 (d, 18H, tBu).
1
Yield: 0.600 g, 81%.31P{ H} NMR (C6D6): 38.5. 1H NMR (C6D6):
1
13C{ H} NMR (C6D6): 139.4–127.3 (Ph); 73.1 (s, PhCH2O); 71.1
7.42–7.18 (Ph); 4.45 (s, 2H, PhCH2O); 3.47 (t, 2H, OCH2CH2,
JH-H = 6 Hz); 2.40 (m, 2H, CH2CH2CH2); 2.30 (s, 5H, Cp); 1.92
(d, OCH2CH2, JP-C = 14 Hz); 30.7 (d, tBu, JP-C = 8 Hz); 29.8
(s, tBu); 25.7 (s, CH2CH2CH2); 18.1 (d, PCH2, JP-C = 22 Hz).
Anal. Calc¢d for C18H31PO: C, 73.43, H, 10.61; found: C, 73.18,
1
(m, 2H, PCH2); 1.11 (d, 18H, tBu, JH-H = 14 Hz). 13C{ H} NMR
(C6D6): 139.5–128.1 (Ph); 125.9 (s, Cp*; 73.4 (s, PhCH2O); 71.4
(d, OCH2CH2, JP-C = 13 Hz); 38.9 (d, tBu, JP-C = 53 Hz); 27.9
(s, tBu); 25.2 (d, CH2CH2CH2, JP-C = 15 Hz); 21.8 (d, PCH2,
JP-C = 53 Hz); 13.5 (s, Cp*). Anal. Calc¢d for C28H50Cl2NPOTi: C,
59.37, N, 2.47, H, 8.90; found: C, 59.12, N, 2.41, H, 8.88%. (7):
H, 10.28%. (2): Yield: 2.33 g, 92%. 31P{ H} NMR (C6D6): 27.4.
1
1H NMR (C6D6): 7.27–7.07 (Ph); 3.53 (s, 2H, PhCH2S); 2.46 (t,
SCH2CH2, JH-H = 7 Hz); 1.79 (m, 2H CH2CH2CH2); 1.36 (m, 2H,
PCH2); 1.13 (d, tBu, JH-H = 12 Hz). 13C{ H} NMR (C6D6): 129.1–
1
1
Yield: 0.956 g, 77%. 31P{ H} NMR (C6D6): 39.2. 1H NMR (C6D6):
126.8 (Ph); 36.2 (s, PhCH2S); 32.6 (d, SCH2CH2, JP-C = 12 Hz);
29.7 (d, tBu, JP-C = 14 Hz); 27.2 (s, tBu); 26.4 (s, CH2CH2CH2);
20.5 (d, PCH2, JP-C = 22 Hz). Anal. Calc¢d for C18H31PS: C, 69.63,
H, 10.06; found: C, 69.43, H, 9.99%.
7.42–7.01 (Ph); 6.52 (s, 5H, Cp); 3.63 (s, 2H, PhCH2S); 2.31 (t, 2H,
SCH2CH2, JH-H = 6 Hz); 2.09 (m, 2H, CH2CH2CH2); 1.45 (m, 2H,
1
PCH2); 0.98 (d, 18H, tBu, JH-H = 14 Hz). 13C{ H} NMR (C6D6):
139.2–127.6 (Ph); 119.9 (s, Cp); 38.9 (d, tBu, JP-C = 52 Hz); 36.2 (s,
PhCH2S); 32.8 (d, tBu, JP-C = 13 Hz); 27.5 (s, SCH2CH2); 24.2 (d,
CH2CH2CH2, JP-C = 4 Hz); 21.2 (d, P-CH2, JP-C = 53 Hz). Anal.
Calc¢d for C23H36Cl2NPSTi: C, 54.34, N, 2.76, H, 7.14; found:
Synthesis of (Me3SiN)tBu2P(CH2)3ECH2Ph (E = O (3); E = S
(4)). These compounds were prepared in a similar fashion and
thus only one preparation is detailed. Azidotrimethylsilane (5 eq.,
6.49 g, 56.3 mmol) was added dropwise to a yellow solution of 1
(1.713 g, 3.315 mmol) in 20 mL of toluene. The mixture became
off white and cloudy, and was refluxed overnight. The solution
was cooled and filtered to remove any impurities. Solvent was
removed in vacuo to afford the yellow oil, (3). Yield: 1.11 g, 88%.
1
C, 54.17, N, 2.65, H, 7.03%. (8): Yield: 0.451 g, 61%. 31P{ H}
NMR (C6D6): 37.7. 1H NMR (C6D6): 7.61–7.00 (Ph); 3.65 (s, 2H,
PhCH2S); 2.40 (m, 2H, SCH2CH2); 2.25 (m, 2H, CH2CH2CH2);
2.19 (s, 15H, Cp*); 1.70 (m, 2H, PCH2); 1.07 (d, 18H, tBu, JH-H
=
1
14 Hz). 13C{ H} NMR (C6D6): 139.5–127.5 (Ph); 126.0 (s, Cp*);
38.8 (d, tBu, JP-C = 53 Hz); 36.5 (s, PhCH2S); 33.4 (d, SCH2CH2,
JP-C = 15 Hz); 27.8 (s, tBu); 24.4 (s, CH2CH2CH2); 23.7 (d, P-CH2,
1
1
31P{ H} NMR (C6D6): 27.1. H NMR (C6D6): 7.28–7.05 (Ph);
4.37 (s, 2H, PhCH2O); 3.33 (t, 2H, OCH2CH2, JH-H = 6 Hz); 1.86
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JP-C = 52 Hz); 13.5 (s, Cp*). Anal. Calc¢d for C28H50Cl2NPSTi: C,
Synthesis of [Cp¢TiMeNPtBu2(CH2)3XCH2Ph][MeB(C6F5)3]
(X = O, Cp¢ = Cp, (13), Cp* (15); X = S, Cp¢ = Cp (16), Cp*
(17) and [Cp¢TiMeNPtBu2(CH2)3XCH2Ph][B(C6F5)4] X = O, Cp¢ =
Cp, (18), Cp* (19); X = S, Cp¢ = Cp (20), Cp* (21)). These
compounds were prepared in a similar fashion, and thus one
preparation is detailed. A 4 mL solution of B(C6F5)3 (79 mg,
0.155 mmol) in C6D5Br was slowly added dropwise at -35 ◦C to a
C6D5Br solution of (9) (4 mL, 70 mg, 0.155 mmol). The reaction
57.73, N, 2.40, H, 8.65; found: C, 57.61, N, 2.28, H, 8.61%.
Synthesis of Cp¢TiMe2NPtBu2(CH2)3OCH2Ph, (Cp¢ = Cp (9),
Cp* (10)). These compounds were prepared in a similar fashion
and thus only one preparation is detailed. 0.405 mL (0.648 mmol)
of a 1.6 M MeLi ether solution was added dropwise to a yellow
benzene solution of 155 mg (0.314 mmol) of (5). After stirring for
25 minutes, the mixture turned cloudy with a grey-yellow color.
Removal of benzene in vacuo afforded a yellow oil. Treatment
with hexanes precipitated LiCl, which was removed via filtration to
afford a clear orange filtrate. Removal of hexanes in vacuo afforded
◦
mixture was stored at -35 C overnight to give compound (13).
1
1
(13):◦31P{ H} NMR (C6D5Br): 45.4. H NMR (partial, C6D5Br,
-30 C): 7.62–7.34 (Ph); 6.72 (s, 5H, Cp); 4.96 (d, 1H, PhCH2O,
JH-H = 12 Hz); 4.61 (d, 1H, PhCH2O, JH-H = 12 Hz); 3.98 (m,
1H, OCH2CH2); 3.82 (m, 1H, OCH2CH2); 1.47 (br s, 3H, TiMe);
1.24 (d, 9H, tBu, JH-H = 7 Hz); 1.19 (d, 9H, tBu, JH-H = 7 Hz);
0.58 (br s, 3H, BMe). 11B NMR (C6D5Br): -15.0 (s). 19F NMR
(C6D5Br): -132.0 (d, 6F, C6F5 (o-F), JF-F = 23 Hz); -164.0 (t,
3F, C6F5 (p-F), JF-F = 20 Hz); -166.4 (m, 6F, C6F5 (m-F)). Anal.
Calc¢d for C43H42BF15NPOTi: C, 53.61, N, 1.45, H, 4.39; found:
1
a dark orange oil. (9): Yield: 0.109 g, 77%. 31P{ H} NMR (C6D6):
1
25.7. H NMR (C6D6): 7.31–7.09 (Ph); 6.19 (s, 5H, Cp); 4.35 (s,
2H, PhCH2O); 3.34 (t, 2H, OCH2CH2, JH-H = 6 Hz); 2.08 (m,
2H, CH2CH2CH2); 1.59 (m, 2H, PCH2); 1.04 (d, 18H, tBu, JH-H
=
14 Hz); 0.63 (s, 6H, TiMe). 13C NMR (C7D8): 138.9–124.5 (Ph);
110.5 (s, Cp); 72.7 (s, PhCH2O); 70.4 (d, OCH2CH2, JP-C = 11 Hz);
40.3 (s, TiMe); 37.8 (d, tBu, JP-C = 55 Hz); 26.7 (s, tBu); 24.7 (s,
CH2CH2CH2); 19.0 (d, PCH2, JP-C = 54 Hz). Anal. Calc¢d for
C25H42NPOTi: C, 66.51, N, 3.10, H, 9.38; found: C, 66.37, N, 3.02,
1
C, 53.49, N, 1.39, H, 4.22%. (15): 31P{ H} NMR (C6D5Br): 43.0.
1H NMR (partial, C6D5Br, -30 ◦C): 7.23–6.82 (Ph); 4.08 (d, 1H,
PhCH2O, JH-H = 7 Hz); 3.99 (d, 1H, PhCH2O, JH-H = 7 Hz); 3.52
(m, 1H, OCH2CH2); 3.34 (m, 1H, OCH2CH2); 1.69 (s, 15H, Cp*);
1.12 (br s, 3H, TiMe); 0.82 (br s, 3H, BMe); 0.77 (d, 9H, tBu,
JH-H = 9 Hz); 0.74 (d, 9H, tBu, JH-H = 10 Hz). 11B NMR (C6D5Br):
1
H, 9.11%. (10): Yield: 0.758 g, 82%.31P{ H} NMR (C6D6): 24.0.
1H NMR (C6D6): 7.32–7.07 (Ph); 4.35 (s, 2H, PhCH2O); 3.35 (t,
2H, OCH2CH2, JH-H = 6 Hz); 2.13 (m, 2H, CH2CH2CH2); 2.06 (s,
15H, Cp*); 1.78 (m, 2H, PCH2); 1.1 8(d, 18H, tBu, JH-H = 13 Hz);
0.41 (s, 6H, TiMe). 13C NMR (C6D6): 129.0–128.1 (Ph); 118.7
(s, Cp*); 73.4 (s, PhCH2O); 71.8 (d, OCH2CH2, JP-C = 13 Hz);
43.3 (s, TiMe); 38.8 (d, tBu, JP-C = 55 Hz); 28.0 (s, tBu); 25.5 (s,
CH2CH2CH2); 21.9 (d, PCH2, JP-C = 54 Hz); 12.6 (s, Cp*). Anal.
Calc¢d for C30H56NPOTi: C, 68.55, N, 2.66, H, 10.74; found: C,
68.38, N, 2.49, H, 10.66%.
-15.0 (s). 19F NMR (C6D5Br): -132.3 (d, 6F, C6F5 (o-F), JF-F
=
20 Hz); -164.4 (t, 3F, C6F5 (p-F), JF-F = 11 Hz); -166.9 (m, 6F,
C6F5 (m-F)). Anal. Calc¢d for C48H56BF15NPOTi: C, 55.56, N, 1.35,
1
H, 5.44; found: C, 55.43, N, 1.23, H, 5.23%. (16): 31P{ H} NMR
(C6D5Br): 45.7. 1H NMR (partial, C6D5Br, -30 ◦C, d): 7.11–6.81
(Ph); 5.77 (s, 5H, Cp); 3.18 (d, 1H, SCH2Ph, JH-H = 12 Hz); 2.99
(d, 1H, SCH2Ph, JH-H = 12 Hz); 2.70 (m, 1H, SCH2CH2); 2.43
(m, 1H, SCH2CH2); 1.12 (br s, 3H, TiMe); 0.87 (br s, 3H, BMe);
0.82 (d, 9H, tBu, JH-H = 20 Hz); 0.76 (d, 9H, tBu, JH-H = 17 Hz).
11B NMR (C6D5Br): -14.7 (s). 19F NMR (C6D5Br): -132.2 (d, 6F,
C6F5 (o-F), JF-F = 20 Hz); -164.3 (t, 3F, C6F5 (p-F), JF-F = 24 Hz);
-166.8 (m, 6F, C6F5 (m-F)). Anal. Calc¢d for C43H42BF15NPSTi:
C, 52.73, N, 1.43, H, 4.32; found: C, 52.68, N, 1.29, H, 4.21%.
Synthesis of Cp¢TiMe2NPtBu2(CH2)3SCH2Ph, (Cp¢ = Cp (11),
Cp* (12)). These compounds were prepared in a similar fashion
and thus only one preparation is detailed. 1.88 mL (5.64 mmol)
of a 3.0 M MeMgBr ether solution was added dropwise at
-78 ◦C to a yellow ether solution of 840 mg (1.71 mmol) of
(7). The reaction mixture was allowed to warm slowly to room
temperature. Following filtration over celite, removal of solvent in
vacuo afforded a brownish orange oil. The product was extracted
with hexanes to give a clear orange filtrate. Subsequent removal
of hexanes in vacuo afforded a viscous orange oil. (11): Yield:
1
1
(17): 31P{ H} NMR (C6D5Br): 44.4. H NMR (partial, C6D5Br,
-30 ◦C): 7.13–6.81 (Ph); 3.22 (d, 1H, SCH2Ph, JH-H = 14 Hz); 2.77
(d, 1H, SCH2Ph, JH-H = 14 Hz); 1.67 (s, 15H, Cp*); 1.13 (br s, 3H,
TiMe); 0.83 (d, 9H, tBu, JH-H = 13 Hz); 0.79 (d, 9H, tBu, JH-H
=
1
0.369 g, 46%. 31P{ H} NMR (C6D6): 25.0. 1H NMR (C6D6): 7.31–
14 Hz); 0.42 (br s, 3H, BMe). 11B NMR (C6D5Br): -14.6 (s). 19F
NMR (C6D5Br): -132.2 (d, 6F, C6F5 (o-F), JF-F = 22 Hz); -164.4
(t, 3F, C6F5 (p-F), JF-F = 23 Hz); -166.9 (m, 6F, C6F5 (m-F)). Anal.
Calc¢d for C48H56BF15NPSTi: C, 54.72, N, 1.33, H, 5.37; found: C,
7.02 (Ph); 6.23 (s, 5H, Cp); 3.53 (s, 2H, PhCH2S); 2.34 (t, 2H,
SCH2CH2, JH-H = 4 Hz); 2.02 (m, 2H, CH2CH2CH2); 1.54 (m, 2H,
PCH2); 1.07 (d, 18H, tBu, JH-H = 12 Hz); 0.66 (s, 6H, TiMe). 13
C
1
NMR (C6D6): 139.3–127.6 (Ph); 111.2 (s, Cp); 41.0 (s, TiMe); 38.5
(d, tBu, JP-C = 55 Hz); 36.6 (s, PhCH2S); 33.4 (d, tBu, JP-C = 13 Hz);
27.8 (s, SCH2CH2); 24.4 (d, CH2CH2CH2, JP-C = 4 Hz); 21.6 (d,
PCH2, JP-C = 54 Hz). Anal. Calc¢d for C25H42NPSTi: C, 66.23,
N, 3.00, H, 9.06; found: C, 66.08, N, 2.87, H, 8.97%. (12): Yield:
54.65, N, 1.21, H, 5.27%. (18): 31P{ H} NMR (C6D5Br): 45.1. 1H
NMR (partial, C6D5Br, -30 ◦C): 7.00–6.81 (Ph); 6.04 (s, 5H, Cp);
3.99 (br s, 1H, OCH2Ph); 3.39 (m, 1H, OCH2CH2); 3.26 (m, 1H,
OCH2CH2); 1.88 (br s, 3H, Ph3CMe); 1.02 (br s, 3H, TiMe); 0.80
(d, 9H, tBu, JH-H = 14 Hz); 0.76 (d, 9H, tBu, JH-H = 9 Hz). Anal.
Calc¢d for C48H39BF20NPOTi: C, 51.68, N, 1.26, H, 3.52; found:
1
0.176 g, 92%. 31P{ H} NMR (C6D6): 23.5. 1H NMR (C6D6): 7.27–
1
7.01 (Ph); 3.54 (s, 2H, PhCH2S); 2.37 (t, 2H, SCH2CH2, JH-H
=
C, 51.43, N, 1.17, H, 3.46%. (19): 31P{ H} NMR (C6D5Br): 43.0.
7 Hz); 2.12 (m, 2H, CH2CH2CH2); 2.06 (m, 15H, Cp*); 1.60 (m,
2H, PCH2); 1.20 (d, 18H, tBu, JH-H = 10 Hz); 0.40 (s, 6H, TiMe).
13C NMR (C6D6): 139.4–127.6 (Ph); 118.7 (s, Cp*; 43.5 (s, TiMe);
38.9 (d, tBu, JP-C = 55 Hz); 36.9 (s, PhCH2S); 33.9 (d, SCH2CH2,
JP-C = 14 Hz); 28.0 (s, tBu); 24.7 (s, CH2CH2CH2); 24.0 (d, PCH2,
JP-C = 46 Hz); 12.6 (s, Cp*). Anal. Calc¢d for C30H56NPSTi: C,
66.52, N, 2.59, H, 10.42; found: C, 66.47, N, 2.45, H, 10.27%.
1H NMR (partial, C6D5Br, -30 ◦C, d): 7.14–6.76 (Ph); 4.08 (d,
1H, OCH2Ph, JH-H = 7 Hz); 4.02 (d, 1H, OCH2Ph, JH-H = 7 Hz);
3.47 (m, 1H, OCH2CH2); 3.33 (m, 1H, OCH2CH2); 1.88 (br s,
3H, Ph3CMe); 1.71 (s, 15H, Cp*); 0.85 (br s, 3H, TiMe); 0.83 (d,
9H, tBu, JH-H = 9 Hz); 0.77 (d, 9H, tBu, JH-H = 9 Hz). Anal.
Calc¢d for C52H53BF20NPOTi: C, 53.04, N, 1.19, H, 4.54; found:
C, 52.89, N, 1.01, H, 4.34%. (20): 31P{ H} NMR (C6D5Br): 45.4.
1
1638 | Dalton Trans., 2009, 1636–1643
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◦
1H NMR (partial, C6D5Br, -30 C): 7.26–6.81 (Ph); 5.88 (s, 5H,
Table 1 Crystallographic data
(5)
Cp); 3.28 (d, 1H, SCH2Ph, JH-H = 13 Hz); 3.13 (d, 1H, SCH2Ph,
JH-H = 13 Hz); 2.53 (m, 1H, SCH2CH2); 2.43 (m, 1H, SCH2CH2);
1.98 (br s, 3H, Ph3CMe); 0.99 (br s, 3H, TiMe); 0.94 (d, 9H, tBu,
JH-H = 23 Hz); 0.83 (d, 9H, tBu, JH-H = 13 Hz). Anal. Calc¢d for
C48H39BF20NPSTi: C, 50.95, N, 1.24, H, 3.47; found: C, 50.86,
(6)
Formula
C23H36Cl2NOPTi
C28H46Cl2NOPTi
562.43
Monoclinic
P21/n
10.6707(12)
11.1671(12)
25.817(3)
94.268(1)
3067.9(6)
4
1.218
0.525
28755
0.0751
5420
307
0.0609
0.1518
Formula weight
Crystal system
Space group
492.30
Monoclinic
P21/n
9.020(3)
20.667(7)
14.584(5)
106.219(4)
2610.5(14)
4
1.253
0.608
24680
0.0496
4600
N, 1.16, H, 3.20%. (21◦): 31P{ H} NMR (C6D5Br): 44.3. 1H NMR
1
˚
a/A
(partial, C6D5Br, -30 C): 7.10–6.81 (Ph); 3.24 (d, 1H, SCH2Ph,
JH-H = 14 Hz); 2.77 (d, 1H, SCH2Ph, JH-H = 14 Hz); 1.87 (br s, 3H,
Ph3CMe); 1.68 (s, 15H, Cp*); 0.80 (d, 9H, tBu, JH-H = 13 Hz); 0.76
(d, 9H, tBu, JH-H = 11 Hz); 0.42 (br s, 3H, TiMe). Anal. Calc¢d for
C52H53BF20NPSTi: C, 52.32, N, 1.17, H, 4.48; found: C, 52.16, N,
1.08, H, 4.34%.
˚
b/A
˚
c/A
b/deg
3
˚
V/A
Z
d(calc)/g cm-1
Abs coeff, m/cm-1
Data collected
Rint
Polymerization protocol. The polymerizations were performed
in a 1 L Buchi reactor system. Following assembly, the reactor
vessel and solvent storage unit were refilled with nitrogen with
4 refill–evacuation cycles over at least 90 minutes. Approximately
600 mL of toluene was transferred to the solvent storage container
from a Grubbs-type purification column. The solvent was purged
with dry nitrogen for 20 minutes and then transferred to the
reactor vessel by differential pressure. The solvent was stirred
at 1500 10 RPM and the temperature was kept constant at
2
2
Data Fo >3s(Fo
)
Variables
R
262
0.0582
0.1482
0.990
wR2
GOF
1.032
◦
˚
Data collected at 20 C with Mo Ka radiation (l = 0.71069 A).
ꢀ
ꢀ
1
2
aR = R(Fo - Fc)/RFo. bwR2 = { [w(Fo - Fc 2]/ [w(Fo) ]}
2
2
2
)
30
2
◦C. The system was then exposed to ethylene via five
change over the duration of the data collections. The data were
processed using the SAINT and SHELXTL processing packages.
An empirical absorption correction based on redundant data was
applied to each data set. Subsequent solution and refinement was
performed using the SHELXTL solution package.55,56
vent–refill cycles. The activator, pre-catalyst and solvent scrubber
stock solutions were prepared in an inert atmosphere glovebox.
Stock solutions were loaded into syringes and transferred to the
reactor. iBu3Al was used as a solvent scrubber for polymerizations
using either B(C6F5)3 or [Ph3C][B(C6F5)4)] as the co-catalyst. When
experiments employed methylalumoxane (MAO), it served as
both the activator and solvent scrubber. CpTi(NPtBu3)Cl2 and
CpTi(NPtBu3)Me2 were used as standards and these standards
were tested regularly to ensure consistent performance of the
reactor system. All trials reported have been done in duplicate
to ensure reproducibility. In a typical experiment, 3.0 mL of
iBu3Al solution (0.125 mmol, 20.8 equivalents) was injected into
the reactor via the catalyst injection inlet. The solvent scrubber
was allowed to stir for 5 minutes. 1.0 mL pre-catalyst solution
of CpTi(NPtBu3)Me2 (0.0060 mmol) was injected. Immediately
afterwards, 1.5 mL solution of B(C6F5)3 (0.0060 mmol) was
injected. The reactor was allowed to stir (1500 10 RPM) for
Structure solution and refinement (Table 1). Non-hydrogen
atomic scattering factors were taken from the literature
tabulations.57 The heavy atom positions were determined using
direct methods employing the SHELXTL direct methods routine.
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 w (Fo - Fc)2 where the weight w is defined as
2
4Fo /2s (Fo2) and Fo and Fc are the observed and calculated
structure factor amplitudes, respectively. In the final cycles of each
refinement, all non-hydrogen atoms were assigned anisotropic
temperature factors in the absence of disorder or insufficient data.
In the latter cases atoms were treated isotropically. C–H atom
positions were calculated and allowed to ride on the carbon to
5 minutes at 30
2
◦C and under 2 atm of ethylene. The
polymerization was halted by closing off the ethylene inlet, venting
the reactor to air and the addition of methanol. Stirring was
stopped, the reactor disassembled and the reactor contents were
transferred to a 4 L beaker containing approximately 100 mL
of 10% HCl in MeOH. The polymer was collected via filtration,
washed with toluene, and dried overnight.
˚
which they are bonded assuming a C–H bond length of 0.95 A.
H-Atom temperature factors were fixed at 1.10 times the isotropic
temperature factor of the C-atom to which they are bonded.
The H-atom contributions were calculated, but not refined. The
locations of the largest peaks in the final difference Fourier map
calculation as well as the magnitude of the residual electron
densities in each case were of no chemical significance. Additional
details are provided in the ESI.†
X-Ray data collection and reduction
Crystals were manipulated and mounted in capillaries in a glove-
box, thus maintaining a dry, O2-free environment for each crystal.
Diffraction experiments were performed on a Siemens SMART
System CCD diffractometer. The data (4.5◦ < 2q < 45–50.0◦) were
collected in a hemisphere of data in 1329 frames with 10 second
exposure times. 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 statistically significant
Results and discussion
Complex synthesis
The phosphines tBu2P(CH2)3ECH2Ph (E = O (1), S (2)) were
prepared in high yield via nucleophilic attack of the lithium
phosphide salt on the commercially available precursor benzyl
3-bromopropyl ether or from the known thioether58 in THF
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at -35 ◦C (Scheme 2). The oils were isolated in good yields
of >90% and they exhibited single resonances in the respective
1
31P{ H} NMR spectra. The oxidation of these phosphines to the
corresponding phosphinimines (Me3SiN)PtBu2(CH2)3ECH2Ph,
E = O (3), S (4)) was carried out by reaction with Me3SiN3
in a typical fashion (Scheme 2). The corresponding reso-
1
nances in the 31P{ H} NMR spectra showed downfield shift
relative to the precursor phosphines. The titanium complexes
Cp¢TiCl2NPtBu2(CH2)3ECH2Ph, (E = O, Cp¢ = Cp (5), Cp* (6);
E = S Cp¢ = Cp (7), Cp* (8)) were readily prepared via reaction
of the phosphinimines (3) or (4) with CpTiCl3 in toluene at room
temperature (Scheme 2). These products were isolated in yields
ranging from 61–81% and (5) and (7) showed a downfield shift
Fig. 2 ORTEP drawing of (6), Hydroge◦n atoms are omitted for
˚
˚
clarity. Selected distances (A) and angles ( ): Ti(1)–N(1) 1.766(3) A,
˚
˚
N(1)–P(1) 1.604(3) A, Ti(1)–Cl(1) 2.3040(14) A, Ti(1)–Cl(2) 2.3169(15)
1
◦
◦
for the Cp resonances (6.46 ppm) in the H NMR spectrum. In
˚
A, Ti(1)–N(1)–P(1) 168.7(2) , Cl(1)–Ti(1)–Cl(2) 101.43(6) .
all cases, the benzylic methylene protons were equivalent in the
1H NMR spectrum, which affirms a pendant nature of the ether
or thioether chain. This view was further confirmed via X-ray
crystallographic studies of compounds (5) and (6) (Fig. 1, 2). The
X-ray data showed a typical pseudo-tetrahedral geometry about
titanium with almost linear Ti–N–P vector ((5): 179.5(2)◦, (6):
168.6(2)◦) indicative of significant multiple Ti–N bond character.
the metal centers. The corresponding dialkyl titanium species were
prepared in moderate to excellent yields of 46–92% by reaction of
the dichloride precursors (5)–(8) with either alkyllithium (MeLi)
or Grignard reagents (MeMgBr) in benzene or ether, respectively.
In the case of the Cp* derivatives (10) and (12) the dialkyl products
were isolated as solids, whereas the Cp-dialkyl products (9) and
(11) could only be isolated as waxy oils (Scheme 2). Expected
˚
˚
The N–P and Ti–N distances of 1.601(3) A and 1.754(3) A and
1
upfield shifts in the 31P{ H} NMR spectra upon alkylation of the
˚
˚
1.604(3) A and 1.766(3) A in (5) and (6), respectively, were similar
to previously reported titanium phosphinimide complexes.46,59 The
1
metal complexes were observed in all cases. H NMR chemical
˚
˚
Ti–O distances of 5.296 A and 5.204 A in (5) and (6) respectively
shifts for the methyl groups ranged from 0.63 ppm for (9) to
0.40 ppm for (12), comparable to those reported for similar
titanium–phosphinimide complexes.60
affirm no significant interaction between the oxygen atoms and
Activation. Activation of species analogous to (9)–(12) with
both B(C6F5)3 and [Ph3C][B(C6F5)4]38 in C6D5Br at -35 ◦C
were examined and studied by NMR spectroscopy. In the
case of 9, slow addition of a cooled solution of the activator
to a solution of 9, following by warming to room tempera-
ture, resulted in the clean formation of the cationic species
[CpTiMe(NPtBu2(CH2)3OCH2Ph)][MeB(C6F5)3] (13) (Scheme 3).
1
The 31P{ H} NMR spectrum of (13) displayed a singlet at
45.4 ppm. A singlet at -15.0 ppm in the 11B NMR spectrum
confirmed the generation of the borate anion while the 19F NMR
spectrum showed a Dd (m,p) value of 2.38, clearly consistent with a
freely solvated methyl borate anion61,62 and thus affirming that (13)
exists in solution as a solvent separated ion pair. Interestingly, the
1H NMR spectrum at -35 ◦C showed that both the methylene
protons alpha to oxygen and the benzylic methylene protons
Scheme 2 Synthesis of (1)–(12).
Fig. 1 ORTEP drawing of (5), Hydrogen atoms are omitted for
◦
˚
˚
clarity. Selected distances (A) and angles ( ): Ti(1)–N(1) 1.754(3)A,
˚
˚
N(1)–P(1) 1.601(3) A, Ti(1)–Cl(1) 2.2981(15) A, Ti(1)–Cl(2) 2.2977(15)
˚
◦
◦
A, Ti(1)–N(1)–P(1) 179.5(2) , Cl(1)–Ti(1)–Cl(2) 101.26 .
Scheme 3 Synthesis of (13)–(14).
1640 | Dalton Trans., 2009, 1636–1643
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Table 2 Ethylene polymerization catalysis
Activity/g
Activity/g
Pre-cat.
Act. (equiv.)
mmol-1h-1atm-1
GPC/103g mol-1
PDI
Pre-cat.
Act. (equiv.)
mmol-1h-1atm-1
GPC/103g mol-1
PDI
b
b
A
(5)
(6)
(7)
(8)
A
(9)
(10)
(11)
(12)
A
MAO (500)
MAO (500)
MAO (500)
MAO (500)
MAO (500)
BCF(1)
BCF(1)
BCF(1)
BCF(1)
BCF(1)
BCF(2)
BCF(2)
BCF(2)
BCF(2)
21132
401
759
105
166
10125
293
1108
873
1894
7429
1499
2862
1185
4092
A
(9)
(10)
(11)
(12)
A
TB(1)
TB(1)
TB(1)
TB(1)
TB(1)
TB(2)
TB(2)
TB(2)
TB(2)
TB(2)
TB(2)
TB(2)
TB(2)
TB(2)
TB(2)
8292
42
846
460
928
2.6
1.8
6.0
1.8
479
449
830
3.6
1.9
11.3
4.4
2365
1776
4846
8438
1766
3004
2575
4812
11774
5267
5894
6052
7730
921
b
629
864
164
298
1.9
3.8
b
(9)
676
6.7
(10)
(11)
(12)
Aa
1.8
b
c
355
1012
480
1.9
2.6
1.9
1015
1014
510
2.0
1.9
1.9
1.7
2.0
(9)
389
(9)a
(10)a
(11)a
(12)a
b
(10)
(11)
(12)
791
b
b
1235
b
BCF(2)
A = CpTiCl2NPtBu3, MAO = methylalumoxane; BCF = B(C6F5)3, TB = [Ph3C][B(C6F5)4]; all reactions were performed at T = 30 ◦C unless otherwise
noted.a T = 60◦C. b sample insoluble. c multimodal distribution.
were diastereotopic. The resonances attributable to the benzylic
methylene protons were resolved as two doublets (4.96 ppm,
JH-H = 12 Hz; 4.61 ppm, JH-H = 12 Hz) while the methylene
protons alpha to oxygen gave rise to two sets of broad signals.
Additionally, two overlapping doublets arose from the tert-butyl
group (1.24 and 1.19 ppm) while the cyclopentadienyl ligand,
methyl group of the borate and Ti-bound methyl group resulted
in signals at 6.72, 0.58 and 1.47 ppm, respectively. These data
are consistent with the coordination of the pendant ethereal
oxygen to Ti. Also consistent with this interpretation is the
observation that addition of a stoichiometric amount of THF
contrast to the very high activity derived from CpTi(NPtBu3)Cl2
activated by excess MAO, compounds (5)–(8) gave rise to only
moderate activities (Table 2). We have previously shown that phos-
phinimide complexes of the form CpTi(NPR3)Cl2 with sterically
less encumbering substituents on P prompt an interaction of the N
atom with AlMe3 giving rise to C–H bond activation products.47,48
It may be that the reduced steric demands about N in (5)–(8) results
in similar processes in the presence of MAO thus deactivating the
catalyst. As well, the Lewis acidity of the Al centers in MAO may
prompt and interaction with the pendant donor ether oxygen or
thioether sulfur atoms. It is noteworthy that Do and coworkers
have described an interaction of metallocene derivative [1-(p-
Me2NC6H4)-3,4-Me2C2H2]2ZrCl2with pendant donor ligands and
MAO.63
The dialkyl titanium complexes (9)–(12) were tested as precat-
alysts for ethylene polymerization using 1 and 2 equivalents of
B(C6F5)3 as the co-catalyst. This activation strategy resulted in
a significant elevation of the polymerization activities (Table 2).
All of the present pre-catalysts showed a significant increase in
activity when two equivalents of the co-catalyst were used. It
is noteworthy that some of the activator may be deterred from
catalyst activation by alternative equilibria involving interaction
with the pendant sulfur or oxygen heteroatom, thus increased
activator concentration results in increased concentration of active
catalyst. Complexes (10) and (12) which feature the bulkier Cp*
ancillary ligand exhibited higher activities than the Cp derivatives
(9) and (11). Similar increases in polymerization activities with
increased steric demand of the cyclopentadienyl ligand have
been previously observed in the case of the related pre-catalysts
Cp¢Ti(NPR3)Me2 (Cp¢ = Cp, tBuC5H4; R = Cy, iPr, tBu).26 The
thioether complex (12) resulted in the highest activity of the
present compounds, suggesting the presence of soft donors gives
improved polymerization activities. A similar observation has
been noted for imine–phenoxide tridentate ligand complexes.64,65
Use of [Ph3C][B(C6F5)4] to activate the dialkyl pre-catalysts (9)–
(12) for polymerization (Table 2) gave even higher activities. This
observation is similar to that previously reported for other Ti–
phosphinimide complexes60 and is consistent with the expected
greater ion pair separation of [B(C6F5)4]- over [MeB(C6F5)3]-.66
1
to the solution of (13) resulted in a collapse of the H NMR
signals from the benzylic methylene protons and methylene
protons alpha to oxygen into single resonances, suggesting that
THF displacement of the pendant ether oxygen occurs giving
rise to the generation of [CpTiMe(THF)(NPtBu2(CH2)3OCH2Ph)]
[MeB(C6F5)3] (14) in which the ether fragment is freely pendant
(Scheme 3). Similar reactions with (10)-–(12) gave the stable ion
pairs [Cp¢TiMe(NPtBu2(CH2)3XCH2Ph)][MeB(C6F5)3] (X = O,
Cp¢ = Cp*, (15); X = S Cp¢ = Cp, (16), Cp* (17)). Spectral
parameters of these species were similar to those observed for
(13). In all cases, the data were consistent with a solvent separated
ion pair, in which the Ti center was stabilized by coordination of
the pendant donor (O or S). In an analogous fashion, reactions
of complexes (9)–(12) with [Ph3C][B(C6F5)4] afforded the ion pair
complexes [Cp¢TiMe(NPtBu2(CH2)3XCH2Ph)][B(C6F5)4] (X = O,
Cp¢ = Cp, (18); Cp* (19); X = S, Cp¢ = Cp, (20), Cp* (21)).
1H NMR spectroscopy revealed that the pairs of benzylic and
the methylene protons alpha to S or O were observed to be
inequivalent consistent with coordination of the heteroatom donor
to titanium.
Polymerization activity. The ability of these complexes to act
as catalyst precursors for ethylene polymerization was investigated
using a Bu¨chi polymerization reactor employing 600 mL of toluene
as the solvent, a catalyst concentration of 10 mmol L-1 and the
reaction was performed at 30 ◦C, under 2 atm of ethylene and
stirred at 1500 rpm. Initially, the dihalide complexes (5)–(8) were
evaluated using 500 equivalents of MAO as the co-catalyst. In
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Performance of the reactions at 60 ◦C employing two equivalents
of [Ph3C][B(C6F5)4], revealed that the precatalysts (9)–(12) results
in a further increase in activity.67–69 Perhaps the most dramatic
increase was seen for (12) where the activity (7730 g mmol-1 h-1
atm-1) was about 65% of that seen for the parent Ti–phosphinimide
species CpTi(NPtBu3)Me2 (11774 g mmol-1 h-1 atm-1). The nature
of the resulting polyethylene was characterized when possible. In
most cases, polydispersities of the polymers suggest single-site
catalyst behavior. In general, these catalysts gave relatively high
molecular weight polyethylene ranging from 389 000–1 235 000,
although in several cases the molecular weight of the polymers
could not be determined as a result of poor solubility. Similar
situations have been described for other Ti–phosphinimide-based
catalysts.
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of olefins; Eur. Pat., 890581, 1999.
28 D. W. Stephan, F. Guerin, R. E. v. H. Spence, L. Koch, X. Gao, S. J.
Brown, J. W. Swabey, Q. Wang, W. Xu, P. Zoricak and D. G. Harrison,
Organometallics, 1999, 18, 2046–2048.
29 C. Beddie, E. Hollink, P. Wei, J. Gauld and D. W. Stephan,
Organometallics, 2004, 23, 5240–5251.
30 S. J. Brown, X. Gao, D. G. Harrison, I. McKay, L. Koch, Q. Wang,
W. Xu, R. E. Spence, and D. W. Stephan, Organometallic complexes
having bis-phosphinimine ligands as catalysts for olefin polymerization;
WO Pat., PCT 2000005238, 2000.
31 S. J. Brown, X. Gao, M. G. Kowalchuk, R. E. v. H. Spence, D. W.
Stephan and J. Swabey, Can. J. Chem., 2002, 80, 1618–1624.
32 L. Cabrera, E. Hollink, J. C. Stewart, P. Wei and D. W. Stephan,
Organometallics, 2005, 24, 1091–1098.
Summary
The chemistry and polymerization data described herein demon-
strate the unique impact of incorporation of pendant hemilabile
donors in phosphinimide complexes. As noted above the stability
of the cationic species (13)–(21) in the absence of ethylene stands
in contrast to that of Ti–phosphinimide complexes that lack
the pendant donor. In addition, it is noteworthy that in general
replacement of a bulky substituent on P with an n-alkyl group
results in a dramatic suppression of polymerization activity. The
present complexes stand in contrast to this observation as well.
These observations support the view that the pendant hemilabile
donor acts to stabilize the active cationic catalyst species generated
by activation of dialkyl–Ti–phosphinimide complexes by B(C6F5)3
or [Ph3C][B(C6F5)4], and yet the donor remains sufficiently labile
to permit continued ethylene polymerization. In addition, the
increased activity as 60 ◦C of the present complexes suggests that
the incorporation of a hemilabile donor may be a strategy to build
in higher temperature catalyst stability.
Supplementary crystallographic data in CIF format have been
deposited with Cambridge database: CCDC 702186–702187.†
33 C.-A. Carraz and D. W. Stephan, Organometallics, 2000, 19, 3791–3796.
34 T. W. Graham, J. Kickham, S. Courtenay, P. Wei and D. W. Stephan,
Organometallics, 2004, 23, 3309–3318.
35 F. Guerin, C. L. Beddie, D. W. Stephan, R. E. v. H. Spence and R.
Wurz, Organometallics, 2001, 20, 3466–3471.
36 R. E. V. H. SpenceS. J. Brown, R. P. Wurz, D. Jeremic, and D. W.
Stephan, Hydrocarbyl phosphinimine/cyclopentadienyl complexes of
group 4 and their use in olefin polymerization; WO Pat., PCT
2001019512, 2001.
Acknowledgements
Financial support from NSERC of Canada and NOVA Chemicals
Corporation is gratefully acknowledged.
37 D. W. Stephan, Can. J. Chem., 2002, 80, 125–132.
38 D. W. Stephan, J. C. Stewart, F. Guerin, S. Courtenay, J. Kickham, E.
Hollink, C. Beddie, A. Hoskin, T. Graham, P. Wei, R. E. v. H. Spence,
W. Xu, L. Koch, X. Gao and D. G. Harrison, Organometallics, 2003,
22, 1937–1947.
39 R. C. W. Sung, S. Courtenay, B. R. McGarvey and D. W. Stephan,
Inorg. Chem., 2000, 39, 2542–2546.
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