Phosphinimide-phosphinimide ligands: New bulky ligands for ethylene polymerization catalysts

Article abstract of DOI:10.1021/om0101184

The phosphinimide-phosphines PPh₂(NPR₃) (R = i-Pr 1, t-Bu 2) were readily prepared in 80-98% yield. These species react with AlMe₃ or B(C₆F₅)₃ to form Me₃AlPPh₂(NPR

Full text of DOI:10.1021/om0101184

Organometallics 2001, 20, 2303-2308
2303
P h osp h in im id e-P h osp h in im id e Liga n d s: New Bu lk y
Liga n d s for Eth ylen e P olym er iza tion Ca ta lysts
Nancy L. S. Yue and Douglas W. Stephan*
School of Physical Sciences, Chemistry and Biochemistry, University of Windsor,
Windsor, Ontario, Canada, N9P 3P4
Received February 13, 2001
The phosphinimide-phosphines PPh2(NPR3) (R ) i-Pr 1, t-Bu 2) were readily prepared
in 80-98% yield. These species react with AlMe3 or B(C6F5)3 to form Me3AlPPh2(NPR3) (R
) i-Pr 3, t-Bu 4) and (C6F5)3B(PPh2(NPi-Pr3)) (5), respectively. Oxidation of compounds 1
and 2 with Me3SiN3 yields Me3SiNPPh2(NPR3) (R ) i-Pr 6, t-Bu 7). These species react with
CpTiCl3 to give titanium(IV) complexes CpTiCl2(NPPh2(NPR3) (R ) i-Pr 8, t-Bu 9) and
subsequently the alkylated complexes CpTiMe2(NPPh2(NPR3)) (R ) i-Pr 10, t-Bu 11).
Compounds 8-11 were tested for activity in ethylene polymerization. In the presence of
excess methylalumoxane, the species 8 and 9 gave rise to active single-site catalysts,
generating 299 and 34 gPE mmol-1 h-1, respectively. In contrast, activation of 10 and 11 by
[Ph3C][B(C6F5)4] showed negligible polymerization activity. Reaction of 11 with B(C6F5)3 was
shown to give numerous products, one of which was the dicationic species [CpTi(µ-Cl)(NPPh2-
(NPt-Bu3)]2[BC6F5)4]2, 12. The formation of this species and the implications of these results
for catalyst and ancillary ligand design are considered and discussed. X-ray crystallographic
data are reported for 1, 3, 4, 8, and 12.
In tr od u ction
phinimide complexes.36-41 These works have shown that
complexes of the form CpTi(NPR3)X2 and (R3PN)2TiX2
are active single-site catalysts for the polymerization
of ethylene.40 In fact, the latter systems exhibit activity
that exceeds that of the constrained geometry catalysts
under specific commercially relevant conditions.41 One
advantage to this family of catalysts is the ability to
effect facile modification of the steric and electronic
properties of the ancillary phosphinimide ligands (Scheme
1). In exploring new derivatives, we have recently
studied Ti complexes of phosphaadamantylphosphin-
imides.42 (Scheme 1) While these ligands offer very
sterically demanding ligands, the presence of the oxygen
in the adamantyl cages prompts reaction with Lewis
acids, leading to ligand-cage rupture and catalyst
deactivation. In this article, we adopt an alternate
The development of olefin polymerization catalysts
continues to be a strong motivation for the development
of the chemistry of a variety of the transition metals.1-5
While the recent efforts focusing on the potential of late
transition metal complexes have drawn much atten-
tion,6-12 the implementation of group 4 metal catalysts
in commercial practice continues to prompt study of new
related systems. The introduction of new ancillary
ligands offers one strategy for the discovery of new
catalysts. In this regard, a variety of Ti and Zr species
have been studied.13-35 In our own efforts, we have
recently published several studies of titanium phos-
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10.1021/om0101184 CCC: $20.00 © 2001 American Chemical Society
Publication on Web 04/27/2001

2304 Organometallics, Vol. 20, No. 11, 2001
Yue and Stephan
Hz), 17.2(s, CH3). Anal. Calcd for C21H31NP2: C, 70.17; H, 8.69;
N, 3.90. Found: C, 69.63; H, 8.37; N, 3.68. 2: Yield: 87% pale
yellow crystalline solid. 31P{1H} NMR (C6D6): 47.9(d, t-Bu3P,
Sch em e 1
| J P-P| ) 62 Hz), 40.8(d, PPh2, | J P-P| ) 62 Hz). 1H NMR
(C6D6): 8.01(m, 4H, m-Ar, |J H-H| ) 7 Hz), 7.23(m, 4H, o-Ar,
|J H-H| ) 8 Hz), 7.05(m, 2H, p-Ar, |J H-H| ) 7 Hz), 1.24(d, 27H,
CH3, |J P-H| ) 13 Hz). 13C{1H} NMR (C6D6): 151.7(d, ipso-Ar,
2
2
2
|12J P-C| ) 20 Hz), 130.4(d, o-Ar, | J P-C| ) 22 Hz), 128.4(d,
3
m-Ar, | J P-C| ) 7 Hz), 127.7(s, p-Ar), 41.6(d, C, |J P-C| ) 49
Hz), 30.3(s, CH3). Anal. Calcd for C24H37NP2: C, 71.79; H, 9.29;
N, 3.49. Found: C, 71.87; H, 9.37; N, 3.34.
strategy to sterically demanding phosphinimide ligands.
Herein we describe the synthesis of phosphinimide-
phosphinimide ligands and the corresponding titanium
complexes. The utility of these ligands and this strategy
in the design of new polymerization catalysts is as-
sessed, and the implications are considered.
Syn th esis of Me3AlP P h 2(NP R3) (R ) i-P r 3, t-Bu 4).
Both compounds were prepared in a similar manner; thus one
procedure is described. A 2.5 M hexane solution of AlMe3 (0.42
mL; 0.84 mmol) was added to a clear benzene solution (6 mL)
of 1 (100 mg; 0.28 mmol). The solution mixture was allowed
to stir at room temperature overnight. Evaporation of the
solvent gave a white solid. The solid was then washed with (2
× 2 mL) hexane and subsequently dried under vacuum. 3:
Yield: 90% white crystalline solid. 31P{1H} NMR (C6D6): 39.7,
Exp er im en ta l Section
Gen er a l Da ta All preparations were done under an atmos-
phere of dry, O2-free N2 employing both Schlenk line tech-
niques and an Innovative Technologies or Vacuum Atmos-
pheres inert atmosphere glovebox. Solvents were purified
employing a Grubb’s type column system manufactured by
Innovative Technology. All organic reagents were purified by
1
26.3. H NMR (C6D6): 7.77(m, 4H, o-Ar, |J H-H| ) 8 Hz), 7.16-
(m, 4H, m-Ar, |J H-H| ) 7 Hz), 7.09(m, 2H, p-Ar, |J H-H| ) 7
Hz), 1.80(m, 3H, CH, |J H-H| ) 7 Hz), 0.86(quart, 18H, CH3,
|J H-H| ) 7 Hz). 13C{1H} NMR (C6D6): 142.0(d, ipso-Ar, |J P-C
|
2
) 30 Hz), 132.5(d, o-Ar, | J P-C| ) 14 Hz), 130.0(s, p-Ar), 128.5-
3
(d, m-Ar, | J P-C| ) 9 Hz), 26.3(d, CH, |J P-C| ) 61 Hz), 17.4(s,
conventional methods. H, 13C, 11B, 19F, and 31P NMR spectra
1
CH3), -6.4(s, CH3). Anal. Calcd for C24H40AlNP2: C, 63.78; H,
10.19; N, 3.54. Found: C, 63.24; H, 9.96; N, 3.12.
were recorded on a Bruker Avance-300 and/or 500. 1H and 13C
NMR spectra are referenced to SiMe4. 31P NMR, 11B NMR, and
19F NMR spectra were recorded on a Bruker Avance-300 and
are referenced to 85% H3PO4, NaBH4/H2O, and F3CCOOH,
respectively. Guelph Chemical Laboratories, Guelph, Ontario,
performed combustion analyses.
4: Yield: 98% white crystalline solid. 31P{1H} NMR
2
2
(C6D6): 45.0(d, t-Bu3P, | J P-P| ) 26 Hz), 28.1(d, PPh2, | J P-P
|
1
) 26 Hz). H NMR (C6D6): 7.84(m, 4H, o-Ar, |J H-H| ) 8 Hz),
7.16(m, 4H, m-Ar, |J H-H| ) 6 Hz), 7.08(m, 2H, p-Ar, |J H-H| )
7 Hz), 1.06(m, 27H, CH, |J H-H| ) 14 Hz), -0.15(s, 9H, CH3).
13C{1H} NMR (C6D6): 141.9(d, ipso-Ar, |J P-C| ) 29 Hz), 133.4-
Syn th esis of P P h 2(NP R3) (R ) i-P r 1, t-Bu 2). Both
compounds were prepared in a similar manner; thus one
procedure is described. Ph2PCl (2.44 g; 0.01 mol) was added
dropwise to a clear orange benzene solution (100 mL) of i-Pr3-
PNLi (2.00 g; 0.01 mol). A white precipitate was formed. The
solution became yellow after 4 h of stirring, and evaporation
of the solvent under vacuum gave a pale yellow solid. The
residue was extracted with 100 mL of hexane. Filtration and
concentration of the solvent gave 1 in 80% yield. 1: 31P{1H}
2
3
(d, o-Ar, | J P-C| ) 14 Hz), 130.0(s, p-Ar), 128.4(d, m-Ar, | J P-C
|
) 8 Hz), 41.0 (d, C, |J P-C| ) 51 Hz), 29.9 (s, CH3), -5.9(s, CH3).
Anal. Calcd for C27H46AlNP2: C, 68.47; H, 9.79; N, 2.96.
Found: C, 68.80; H, 10.28; N, 2.99.
Syn th esis of (C6F 5)3B(P P h 2(NP i-P r 3)), 5. A benzene
solution of B(C6F5)3 (140 mg; 0.28 mmol) was added to a clear
benzene solution (5 mL) of 1 (100 mg; 0.28 mmol). The solution
mixture was allowed to stir at room temperature for 2 h.
Evaporation of the solvent gave a white solid. The solid was
then washed with (2 × 2 mL) hexane and subsequently dried
under vacuum. 5: Yield: 87% white solid. 31P{1H} NMR
2
NMR (C6D6): 42.4(d, i-Pr3P, | J P-P| ) 80 Hz), 38.9(d, PPh2,
2
1
| J P-P| ) 80 Hz). H NMR (C6D6): 8.02(m, 4H, o-Ar, |J H-H| )
7 Hz), 7.26(m, 4H, m-Ar, |J H-H| ) 7 Hz), 7.08(m, 2H, p-Ar,
|J H-H| ) 7 Hz), 1.94(m, 3H, CH, |J H-H| ) 4 Hz), 0.95(quart,
18H, CH3, |J H-H| ) 7 Hz). 13C{1H} NMR (C6D6): 151.2(d, ipso-
2
(C6D6): 39.8(d, i-Pr3P, |J P-P| ) 59 Hz), 33.2(v br, PPh2). 1H
NMR (C6D6): 7.56(m, 4H, o-Ar, |J H-H| ) 8 Hz), 6.97(m, 2H,
p-Ar, |J H-H| ) 8 Hz), 6.87(m, 4H, m-Ar, |J H-H| ) 8 Hz), 1.59-
(m, 3H, CH, |J H-H| ) 7 Hz), 0.52(quart, 18H, CH3, |J H-H| ) 7
Hz). 11B NMR (C6D6): 34.8. 19F NMR (C6D6): -47.9(d, 6F,
o-C6F5, |J F-F| ) 22 Hz), -81.0(t, 6F, m-C6F5, |J F-F| ) 21 Hz),
-87.5(m, 3F, p-C6F5, |J F-F| ) 23 Hz). 13C{1H} NMR (C6D6):
151.9, 142.0, 136.2, 135.5, 133.0, 131.2, 128.7(d, |J P-C| ) 15
Hz), 127.8(d, |J P-C| ) 15 Hz), 27.0(d, |J P-C| 12 ) 61 Hz), 16.7.
Anal. Calcd for C39H49BF15NP2: C, 53.75; H, 3.59; N, 1.61.
Found: C, 53.21; H, 3.45; N, 1.42.
2
Ar, |J P-C| ) 27 Hz), 130.4(d, o-Ar, | J P-C| ) 22 Hz), 128.1(d,
3
m-Ar, | J P-C| ) 6 Hz), 127.5(s, p-Ar), 25.5(d, CH, |J P-C| ) 59
(30) Rogers, J . S.; Lachicotte, R. J .; Bazan, G. C. J . Am. Chem. Soc.
1999, 121, 1288-1298.
(31) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K.; Imai, A. Organo-
metallics 1998, 17, 2152-2154.
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1998, 17, 308-321.
(33) Rodriguez, G.; Bazan, G. C. J . Am. Chem. Soc. 1997, 119, 343-
352.
(34) Sun, Y.; Piers, W. E.; Yap, G. P. A. Organometallics 1997, 16,
2509-2513.
Syn th esis of Me3SiNP P h 2(NP R3) (R ) i-P r 6, t-Bu 7).
Both compounds were prepared in a similar manner; thus one
procedure is described. Me3SiN3 (129 mg; 1.12 mmol) was
added dropwise to 335 mg (0.93 mmol) of white crystalline 1.
Gas evolution was observed. The mixture became an orange
oil after refluxing overnight. The orange oil was extracted with
(2 × 5 mL) hexane, and the hexane was filtered and removed
under vacuum. 6: Yield: 94% white solid. 31P{1H} NMR
(35) Fokken, S.; Spaniol, T. P.; Kang, H.-C.; Massa, W.; Okuda, J .
Organometallics 1996, 15, 5069-5072.
(36) Sung, R. C. W.; Courtenay, S.; McGarvey, B. R.; Stephan, D.
W. Inorg. Chem. 2000, 39, 2542-2546.
(37) Kickham, J . E.; Guerin, F.; Stewart, J . C.; Stephan, D. W.
Angew. Chem. 2000, 112, 1354-1356.
(38) Gue´rin, F.; Stewart, J . C.; Beddie, C.; Stephan, D. W. Organo-
metallics 2000.
(39) Guerin, F.; Stephan, D. W. Angew. Chem. Int. Ed. 2000, 39,
1298-1301.
2
2
(C6D6): 41.4(d, i-Pr3P, | J P-P| ) 8 Hz), -6.1(d, PPh2, | J P-P| )
9 Hz). 1H NMR (C6D6): δ 8.10(m, 4H, o-Ar, |J H-H| ) 8 Hz),
7.20(m, 4H, m-Ar, |J H-H| ) 8 Hz), 7.08(m, 2H, p-Ar, |J H-H| )
7 Hz), 2.06(m, 3H, CH, |J H-H| ) 7 Hz), 0.94(m, 18H, CH3,
|J H-H| ) 8 Hz), 0.41(s, 9H, CH3). 13C{1H} NMR (C6D6): 144.3-
(40) Stephan, D. W.; Stewart, J . C.; Guerin, F.; Spence, R. E. v.;
Xu, W.; Harrison, D. G. Organometallics 1999, 17, 1116-1118.
(41) Stephan, D. W.; Guerin, F.; Spence, R. E. v.; Koch, L.; Gao, X.;
Brown, S. J .; Swabey, J . W.; Wang, Q.; Xu, W.; Zoricak, P.; Harrison,
D. G. Organometallics 1999, 17, 2046-2048.
(42) Carraz, C.; Stephan, D. W. Organometallics 2000, 19, 3791-
3796.
2
(d, ipso-Ar, |J P-C| ) 128 Hz), 132.0(d, o-Ar, | J P-C| ) 10 Hz),
3
129.4(p-Ar), 128.0(d, m-Ar, | J P-C| ) 12 Hz), 25.5(d, CH, |J P-C
|

Phosphinimide-Phosphinimide Ligands
Organometallics, Vol. 20, No. 11, 2001 2305
) 60 Hz), 27.5(s, CH3), 5.2(s, CH3). 7: Yield: 90% white solid.
Hz), 0.82(s, 6H, CH3). 13C{1H} NMR (C6D6): 142.1(d, ipso-Ar,
2
3
31P{1H} NMR (C6D6): 46.5(d, t-Bu3P, J P-P| ) 11 Hz), -8.4(d,
|J P-C| ) 129 Hz), 132.2(d, o-Ar, | J P-C| ) 10 Hz), 130.1(s, p-Ar),
2
2
PPh2, | J P-P| ) 11 Hz). 1H NMR (C6D6): 8.07(m, 4H, o-Ar,
128.2(d, m-Ar, | J P-C| ) 12 Hz), 111.1(s, Cp), 41.0(d, C, |J P-C
|
|J H-H| ) 8 Hz), 7.20(m, 4H, m-Ar, |J H-H| ) 8 Hz), 7.08(m, 2H,
p-Ar, |J H-H| ) 7 Hz), 1.21(d, 27H, CH3, |J H-H| ) 13 Hz), 0.41-
(s, 9H, CH3). 13C{1H} NMR (C6D6): 144.6(d, ipso-Ar, |J P-C| )
130 Hz), 132.0(d, o-Ar, |J P-C| ) 10 Hz), 129.3(s, p-Ar), 128.0-
(d, m-Ar, |J P-C| ) 12 Hz), 41.1(d, C, |J P-C| ) 51 Hz), 30.1(s,
CH3), 5.1(s, CH3).
) 50 Hz), 40.5(s, CH3), 29.9(s, CH3).
Syn th esis of [Cp Ti(µ-Cl)(NP P h 2(NP t-Bu 3))]2[BC6F 5)4]2,
12. To a CH2Cl2 solution (1.5 mL) of B(C6F5)3 (70 mg; 0.136
mmol) was added dropwise a clear orange CH2Cl2 solution (1.5
mL) of 11 (0.200 g; 0.036 mmol). The solution was allowed to
stir at room temperature for 2 weeks. A few deep red crystals
were obtained upon standing. Yield: <10%. 31P{1H} NMR
Syn th esis of Cp TiCl2(NP P h 2(NP R3) (R ) i-P r 8, t-Bu
9). Both compounds were prepared in a similar manner; thus
one procedure is described. (i) To a clear orange toluene
solution (80 mL) of CpTiCl3 (420 mg; 2.00 mmol) was added a
toluene solution (10 mL) of 6 (940 mg; 2.10 mmol). The solution
mixture was stirred at room temperature overnight. Evapora-
tion of toluene under vacuum gave an orange oil. The oil was
extracted with benzene (2 × 50 mL) and filtered, and the
solvent was removed under vacuum. The resulting orange oil
was washed with (3 × 5 mL) diethyl ether and dried under
vacuum. 8: Yield: 70% yellow solid. 9: Yield: 91% orange
solid. (ii) To a clear orange benzene solution (50 mL) of CpTiCl3
(307 mg; 1.39 mmol) was added Me3SiN3 (256 mg; 2.23 mmol).
(Caution! Although no problems were encountered with this
preparation, metal azides may be explosive.) The solution
mixture was stirred at room temperature overnight, and a
benzene solution (30 mL) of 1 (500 mg; 1.39 mmol) was added.
The solution became deep red-orange with gas evolution and
was stirred at room temperature overnight. Evaporation of
benzene gave a yellow solid, which was then washed with (3
× 10 mL) hexane. 8: Yield: 84% yellow solid. 31P{1H} NMR
2
2
(CD2Cl2): 58.0(d, | J P-P| ) 10 Hz), 10.2(d, | J P-P| ) 10 Hz). 1H
NMR (CD2Cl2): 7.81(m, 8H, o-Ar, |J H-H| ) 7 Hz), 7.68(m, 4H,
p-Ar, |J H-H| ) 8 Hz), 7.57(m, 8H, m-Ar, |J H-H| ) 8 Hz), 6.63(s,
10H, Cp), 1.46(d, 54H, CH3, |J P-H| ) 14 Hz). Anal. Calcd for
C
56H48BClF20N2P2Ti: C, 52.34; H, 3.76; N, 2.18. Found: C,
52.01; H, 3.28; N, 2.09.
Eth ylen e P olym er iza tion These experiments were done
in one of two ways. Each is described below. (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. Five
hundred equivalents of a 10 wt % toluene solution of methyl-
aluminoxane (MAO) was added to the flask. Alternatively, a
catalyst precursor was combined with [Ph3C][B(C6F5)4] under
an ethylene atmosphere. The flask was attached to a Schlenk
line with cold trap, a stopwatch was started, and the flask was
three times evacuated 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, total reaction
time was noted, and the polymer was isolated. (ii) A 1 L
autoclave was dried under vacuum (10-2 mmHg) for several
hours. Dried 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. Solutions of MAO
(500 equiv) and catalyst precursor in toluene were sequentially
injected. The mixture was stirred for 3 min at a rate of 150
rpm after each addition. The rate of stirring was increased to
1000 rpm, and the vessel was vented of N2 and pressurized
with ethylene (33 psi). Any 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.
X-r a y Da ta Collection a n d Red u ction . X-ray quality
crystals were obtained 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 either on a Rigaku
AFC6 four-circle or a Siemens SMART System CCD diffrac-
tometer. In the latter case the data were collect in a hemi-
sphere 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.
The data sets were collected (4.5° < 2θ < 45-50.0°). 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 change over the duration
of the data collections. The data were processed using the
SAINT and XPREP processing package. An empirical absorp-
tion correction based on redundant data was applied to each
data set. Subsequent solution and refinement was performed
using the SHELXTL solution package operating on a Pentium
computer.
2
(C6D6): 48.7(d, i-Pr3P, | J P-P| ) 8 Hz), -4.87(s, PPh2). 1H NMR
(C6D6): 8.07(m, 4H, o-Ar, |J H-H| ) 7 Hz), 7.15(m, 4H, m-Ar,
|J H-H| ) 8 Hz), 7.07(m, 2H, p-Ar, |J H-H| ) 8 Hz), 6.24, 2.24(d,
3H, CH, |J P-H| ) 7 Hz), 1.03(quart, 18H, CH3, |J H-H| ) 7 Hz).
13C{1H} NMR (C6D6): 138.2(d, ipso-Ar, |J P-C| ) 129 Hz), 132.3-
3
2
(d, o-Ar, | J P-C| ) 11 Hz), 131.4(s, p-Ar), 128.7(d, m-Ar, | J P-C
|
) 13 Hz), 114.9(s, Cp), 25.4(d, CH, |J P-C| ) 59 Hz), 17.2. Anal.
Calcd for C26H36Cl2N2P2Ti: C, 56.03; H, 6.51; N, 5.03. Found:
C, 56.99; H, 6.71; N, 5.04. 9: Yield: 96%. 31P{1H} NMR
2
2
(C6D6): 52.3(d, t-Bu3P, | J P-P| ) 12 Hz), -11.5(d, PPh2, | J P-P
|
1
) 10 Hz). H NMR (C6D6): 8.11(m, 4H, m-Ar, |J H-H| ) 8 Hz),
7.14(m, 4H, o-Ar, |J H-H| ) 8 Hz), 7.06(m, 2H, p-Ar, |J H-H| ) 7
Hz), 6.29(s, 5H, Cp), 1.13(d, 27H, CH3, |J P-H| ) 14 Hz). 13C-
{1H} NMR (C6D6): 138.5(d, ipso-Ar, |J P-C| ) 132 Hz), 132.5-
3
2
(d, o-Ar, | J P-C| ) 11 Hz), 131.2(s, p-Ar), 128.7(d, m-Ar, | J P-C
|
) 13 Hz), 115.0(s, Cp), 40.9(d, C, |J P-C| ) 50 Hz), 29.8(CH3).
Anal. Calcd for C30H45Cl2N2P2Ti: C, 58.64; H, 7.38; N, 4.56.
Found: C, 58.31; H, 7.43; N, 4.88.
Syn th esis of Cp TiMe2(NP P h 2(NP R3)) (R ) i-P r 10, t-Bu
11). Both compounds were prepared in a similar manner; thus
one procedure is described. To a clear orange toluene solution
(10 mL) of 8 (150 mg; 0.27 mmol) was added a 3.0 M diethyl
ether solution of CH3MgBr (0.20 mL; 0.59 mmol). The solution
mixture became orange-brown after 30 min of stirring. The
solution was allowed to stir at room temperature overnight.
Evaporation of toluene gave an orange-brown solid. The solid
was extracted with (2 × 5 mL) benzene/hexane (3:1) and
filtered, and the solvent was removed under vacuum. 10:
Yield: 91% yellow solid. 31P{1H} NMR (C6D6): δ 44.9(d, i-Pr3P,
|J 2P-P| ) 7 Hz), -12.1(s, PPh2). 1H NMR (C6D6): δ 8.11(m, 4H,
m-Ar, |J H-H| ) 7 Hz), 7.19(m, 4H, o-Ar, |J H-H| ) 7 Hz), 7.08-
(m, 2H, p-Ar, |J H-H| ) 7 Hz), 6.09(s, 5H, Cp), 2.20(m, 3H, CH,
|J H-H| ) 7 Hz), 0.97(q, 18H, CH3, |J H-H| ) 7 Hz), 0.76(s, 6H,
CH3). 13C{1H} NMR (C6D6): 141.7(d, ipso-Ar, |J P-C| ) 126 Hz),
3
132.0(d, o-Ar, | J P-C| ) 10 Hz), 130.2(s, p-Ar), 128.3(d, m-Ar,
2
| J P-C|) 12 Hz), 111.0(s, Cp), 39.7(s, CH3), 25.5(d, CH, |J P-C
|
) 60 Hz), 17.3(s, CH3). 11: Yield: 88% yellow solid. 31P{1H}
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.43 The heavy atom positions were determined using
2
NMR (C6D6): 49.0(d, t-Bu3P, | J P-P| ) 11 Hz), -17.1(d, PPh2,
2
1
| J P-P| ) 10 Hz). H NMR (C6D6): 8.15(m, 4H, m-Ar, |J H-H| )
8 Hz), 7.18(m, 4H, o-Ar, |J H-H| ) 7 Hz), 7.07(m, 2H, p-Ar,
|J H-H| ) 7 Hz), 6.11(s, 5H, Cp), 1.20(d, 27H, CH3, |J P-H| ) 14
(43) Cromer, D. T.; Mann, J . B. Acta Crystallogr. A 1968, A24, 390.

2306 Organometallics, Vol. 20, No. 11, 2001
Ta ble 1. Cr ysta llogr a p h ic P a r a m eter sa
Yue and Stephan
1
3
4
8
12
formula
fw
C
21H31NP2
C24H40AlNP2
431.49
17.6217(2)
15.2123(2)
21.5862(3)
C39H32BF15NP2
872.41
14.654(4)
13.954(8)
19.314(16)
C26H36Cl2N2P2Ti
557.31
10.479(5)
25.114(8)
10.932(2)
C59H48BClF20N2P2Ti
1321.09
11.1052(4)
15.3036(6)
18.4595(8)
93.7560(10)
106.3140(10)
95.5220(10)
2982.8(2)
P1h
359.41
a, Å
9.27450(10)
14.67250(10)
15.6324(2)
b, Å
c, Å
R, deg
â, deg
99.890(1)
113.6220(10)
104.11(5)
94.81(4)
γ, deg
V (Å3)
2095.65(4)
P21/c
1.139
4
0.210
8907
3647
217
0.0691
0.1571
0.685
5301.68(12)
P21/n
1.081
4
3830(4)
P21/n
1.513
4
2866.8(16)
P21/n
1.291
4
0.613
3703
2393
288
0.0950
0.2456
1.133
space group
d(calc), g cm-1
Z
1.471
2
µ, mm-1
no. of data collected
no. of data used
no. of variables
R (%)
0.207
25 603
9190
0.218
18 407
6628
0.345
125 429
7643
505
523
724
0.0514
0.1247
1.044
0.0732
0.1496
1.032
0.1038
Rw (%)
goodness of fit
0.2960
1.251
a
2
All data collected at 24 °C with Mo KR radiation (λ ) 0.71069 Å), R ) ∑||Fo| - |Fc||/∑|Fo|, Rw ) [∑(|Fo| - |Fc|)2|/∑|Fo| ]0.5
.
Ta ble 2. Eth ylen e P olym er iza tion Da ta
productivity
catalyst
time
(g mmol-1
presursor cocatalysta (min) h-1 atm-1
)
Mw
Mw/Mn
8c
MAO
MAO
TB
3.00
60.00
3.00
299
34
d
118 700
1.74
2.24
d
9b
1 083 000
10c
d
d
11c
TB
3.00
d
d
c
Cp2ZrCl2
MAO
2.00
895
11 600
2.82
a
MAO ) methylaluminoxane; TB ) trityl tetrakis(pentafluo-
rophenyl)borate. 33 psi (ethylene), 60-65 °C. c 1 atm (ethylene),
25 °C. Insufficient polymerization to report.
b
d
Sch em e 2
F igu r e 1. 31P NMR and 31P{1H} NMR spectra (inset)
of 2.
groups, the correct enantiomorphic was confirmed by data
inversion and refinement. The final values of refinement
parameters are given in Table 1. 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. Positional parameters,
hydrogen atom parameters, thermal parameters, and bond
distances and angles have been deposited as Supporting
Information.
Resu lts a n d Discu ssion
Syn th esis. The phosphinimide-phosphines PPh2-
(NPR3) (R ) i-Pr 1, t-Bu 2) were readily prepared in
80-98% yields by stoichiometric reaction of R3PNLi and
chlorodiphenylphosphine under mild conditions (Scheme
2). The presence of two phosphorus atoms was con-
firmed by the presence of the two doublets in the 31P-
{1H} NMR spectra. For compound 2, the resonance at
47.9 ppm was attributed to a P(V) center, while the
signal at 40.8 ppm was assigned to the P(III) atom. The
P-P coupling constant is 62 Hz. In the 31P NMR
spectrum, the P(V) signal was split into a multiplet
centered at 47.4 ppm, revealing coupling to the tert-
butyl methyl protons of 12 Hz. On the other hand, only
broadening of the P(III) doublet was observed (Figure
1). The structure of 1 was confirmed by X-ray crystal-
lographic data (Figure 2). The P-N bond distances of
1.584(3) and 1.659(3) Å correspond to those expected for
P-N double and single bonds, respectively.44,45 The
direct methods employing either the SHELXTL or 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 ω is defined as 4Fo2/2σ(Fo2) and Fo and
Fc are the observed and calculated structure factor amplitudes.
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. For chiral space
(44) Dehnicke, K.; Kreiger, M.; Massa, W. Coord. Chem. Rev. 1999,
182, 19-65.

Phosphinimide-Phosphinimide Ligands
Organometallics, Vol. 20, No. 11, 2001 2307
F igu r e 2. ORTEP drawing of 1; 30% ellipsoids are shown,
hydrogen atoms have been omitted for clarity. P(1)-N(1)
1.584(3) Å; P(2)-N(1) 1.659(3) Å; P(1)-N(1)-P(2) 126.55-
(19)°.
F igu r e 4. ORTEP drawing of 4; 30% thermal ellipsoids
are shown, hydrogen atoms have been omitted for clarity.
P(1)-N(1) 1.590(4) Å; P(1)-B(1) 2.135(5) Å; P(2)-N(1)
1.577(4) Å; N(1)-P(1)-B(1) 110.9(2)°; P(2)-N(1)-P(1)
157.1(3)°.
Sch em e 3
F igu r e 3. ORTEP drawing of one of the two molecules of
3 in the asymmetric unit; 30% ellipsoids are shown,
hydrogen atoms have been omitted for clarity. Selected
bond distances and angles for the two molecules are
listed: (a) Al(1)-P(2) 2.5190(11) Å; P(1)-N(1) 1.568(2) Å;
P(2)-N(1) 1.627(2) Å; N(1)-P(2)-Al(1) 123.92(9)°; P(1)-
N(1)-P(2) 141.52(16)°. (b) Al(2)-P(4) 2.5183(11) Å; P(3)-
N(2) 1.567(2) Å; P(4)-N(2) 1.619(2) Å; N(2)-P(4)-Al(2)
124.72(10)°; P(3)-N(2)-P(4) 144.48(18)°.
P-N-P angle is bent as expected, forming an angle of
126.55(19)°.
The Lewis basicity of 1 and 2 was probed. Upon
reaction with AlMe3, coordination of Al at the P(III)
centers of 1 and 2 was inferred by the shift and the
breadth of the upfield signals in the 31P{1H} NMR
spectra. The formulation of these products as the alane
adducts Me3AlPPh2(NPR3) (R ) i-Pr 3, t-Bu 4) was
confirmed by an X-ray crystallographic study of 3
(Figure 3). The Al-P distances in 3 average 2.5186(11)
Å, while the P-N distances range from 1.567(2) to
1.627(2) Å. The Al-N-P and P-N-P angles average
124.82(10)° and 144.50(18)°, respectively, consistent
with a sterically crowded pseudo-tetrahedral coordina-
tion geometry about phosphorus. In a similar manner,
1 reacts with B(C6F5)3 in hydrocarbon solvents at room
temperature, generating compound 5 in 87% yield. On
the basis of the multinuclear NMR data, 5 is formulated
as (C6F5)3B(PPh2(NPi-Pr3)). The quadrupolar-broadened
resonance in the 31P{1H} NMR spectrum is attributed
to the boron-bound P(III) center. An X-ray structure of
5 (Figure 4) confirmed the formulation. The P-N bond
lengths in 5 are 1.590(4) and 1.577(4) Å. The shortening
of the P(III)-N bond is consistent with electron donation
to B. The P-N-P bond angle in 5 of 157.1(3)° in
considerably larger than that in 3, presumably a result
of the steric demands of both the phosphinimide-
phosphine ligand and B(C6F5)3.
Oxidation of compounds 1 and 2 via the Staudinger
reaction44,45 with 1 equiv of Me3SiN3 proceeds with the
elimination of N2 and the formation of the corresponding
phosphinimide-phosphinimine ligands Me3SiNPPh2-
(NPR3) (R ) i-Pr 6, t-Bu 7, respectively. In a standard
manner,40,41 these species react with CpTiCl3 to give
titanium(IV) complexes CpTiCl2(NPPh2(NPR3) (R ) i-Pr
8, t-Bu 9, respectively) with loss of Me3SiCl (Scheme
3). Alternatively, complexes 8 and 9 were also prepared
via a one-pot reaction of CpTiCl3 with Me3SiN3, followed
by the addition of 1 equiv of the precursor phosphin-
imide-phosphine 1 or 2. The 31P{1H} NMR spectra of
8 and 9 consist of the typical AX spin pattern similar
to that seen for compounds 6 and 7. The formulation of
these titanium complexes was confirmed spectroscopi-
cally and by an X-ray crystallographic study of complex
8 (Figure 5). The Ti-N bond distance of 1.774(3) Å in
complex 8 was within the range typically seen for Ti-
phosphinimide derivatives.38 It is interesting to note
that the P(1)-N(1) bond distance, 1.612(3) Å, is slightly
longer than the P(1)-N(2) and P(2)-N(2) distances of
1.598(4) and 1.593(4) Å. The P-N-Ti angle in 8 of
164.7(2)° approaches linearity, as is typical of Ti-
phosphinimide derivatives.36,38,40,41 Treatment of 8 and
(45) Dehnicke, K.; Weller, F. Coord. Chem. Rev. 1997, 158, 103-
169.

2308 Organometallics, Vol. 20, No. 11, 2001
Yue and Stephan
noteworthy that in contrast to Ti-phosphaadaman-
tylphosphinimide complexes42 or Ti-trialkylphosphin-
imide derivatives,37 these systems are not attacked by
excess AlMe3. This tolerance augurs well for catalyst
optimization efforts employing related phosphinimide-
phosphinimide ligands.
In marked contrast to the above results, related tests
at 1 atm ethylene employing the methyl derivatives 10
and 11 using [Ph3C][B(C6F5)4] as the activator showed
minimal polymerization activity. This is in sharp con-
trast to the analogous phosphinimide complexes CpTi-
(NPR3)Me2, where activation with [Ph3C][B(C6F5)4] or
B(C6F5)3 leads to catalysts of varying activity depending
on the phosphinimide substituents.40 Stoichiometric
reactions of phosphinimide complexes of the form CpTi-
(NPR3)Me2 with B(C6F5)3 have been shown to lead
cleanly to the zwitterionic species CpTiMe(NPR3)(µ-
MeB(C6F5)3).40 Efforts to probe similar reactions with
11 were undertaken in an effort to understand the
surprisingly low activity of catalysts derived from 10
and 11/[Ph3C][B(C6F5)4]. The reaction of 11 with excess
B(C6F5)3 was monitored by 31P NMR spectroscopy,
revealing the formation of a number of unidentified
products. Upon standing for 2 weeks in CH2Cl2, one of
the products crystallized from solution. Although the
crystal quality was not the best, the X-ray crystal-
lographic data did establish the formulation of 12 as
[CpTi(µ-Cl)(NPPh2(NPt-Bu3))]2[BC6F5)4]2. This centrosym-
metric dication of 12 is comprised of a chloro-bridged
dimeric unit analogous to the previously reported Ti-
(III) dimer [CpTi(µ-Cl)(NPt-Bu3)]2.36 It is noteworthy
that the Ti-Cl and Ti-N distances of 1.755(5) and
2.453(2) Å in 12 are significantly shorter than the
corresponding distances of 1.820(2) and 2.4840(11) Å
found in [CpTi(µ-Cl)(NPt-Bu3)]2,36 consistent with the
dicationic charge. A pair of [BC6F5)4] anions provide the
required charge balance.
While the mechanism of formation of 12 is the subject
of speculation, its formation does permit some inferences
to be made. Assuming the initial interaction of 11 with
B(C6F5)3 is the expected methyl abstraction, the result-
ing zwitterion is apparently highly reactive. Subsequent
reactions are complex but clearly include borate-sub-
stituent redistribution as well as activation of the
solvent CD2Cl2. In contrast, the analogous zwitterionic
Ti species of the form CpTiMe(NPR3)(µ-MeB(C6F5)3) are
stable.40 This observation suggests that electron-with-
drawing phosphinimide substituents on phosphinimide
ligand complexes result in highly Lewis acidic and
consequently reactive Ti centers. The activity of the
catalysts derived from 8 or 9 and MAO suggests that
interactions with MAO serve to stabilize the generated
catalysts. Moreover, these results suggest that the steric
bulk of these ligands preclude complex degradation by
the Al activator as has been seen in related systems.37,42
F igu r e 5. ORTEP drawing of 8; 30% thermal ellipsoids
are shown, hydrogen atoms have been omitted for clarity.
Ti(1)-N(1) 1.774(3), Ti(1)-Cl(2) 2.3145(15) Å; Ti(1)-Cl(1)
2.3176(16), P(1)-N(2) 1.598(4) Å; P(1)-N(1) 1.612(3) Å;
P(2)-N(2) 1.593(4) Å; N(1)-Ti(1)-Cl(2) 104.24(12)°; N(1)-
Ti(1)-Cl(1) 102.07(12)°; Cl(2)-Ti(1)-Cl(1) 102.01(7)°; N(2)-
P(1)-N(1) 118.16(18)°; P(1)-N(1)-Ti(1) 164.7(2)°; P(2)-
N(2)-P(1) 134.9(2)°.
F igu r e 6. ORTEP drawing of the dication of 12; 30%
thermal ellipsoids are shown, hydrogen atoms have been
omitted for clarity. Ti(1)-N(1) 1.755(5) Å; Ti(1)-Cl(1)′
2.451(2) Å; Ti(1)-Cl(1) 2.455(2) Å; P(1)-N(2) 1.577(6) Å;
P(1)-N(1) 1.666(5) Å; P(2)-N(2) 1.600(6) Å; N(1)-Ti(1)-
Cl(1)′ 104.53(17)°; N(1)-Ti(1)-Cl(1) 104.11(17)°; Cl(1)′-
Ti(1)-Cl(1) 89.12(6)°; Ti(1)′-Cl(1)-Ti(1) 90.88(6)°; N(2)-
P(1)-N(1) 116.6(3)°; P(1)-N(1)-Ti(1) 162.4(3)°; P(1)-
N(2)-P(2) 157.6(4)°.
9 with MeMgBr readily provides the alkylated com-
plexes CpTiMe2(NPPh2(NPR3)) (R ) i-Pr 10, t-Bu 11)
1
in high yields, as evidenced by 31P{1H}, H, and 13C-
{1H} NMR data.
Eth ylen e P olym er iza tion Compounds 8-11 were
tested for activity in ethylene polymerization. Employ-
ing a large excess of MAO (500 equiv), the species 8 gave
rise to an active catalyst. The initial rate of polyethylene
production (3 min) in this case was 299 gPE mmol-1
h-1 at 25 °C and 1 atm ethylene pressure. Employing 9
and MAO at higher temperature (60-65 °C) and pres-
sure (33 psi) resulted in a catalyst that gave 34 gPE
mmol-1 h-1 atm-1 over a 1 h period. In both cases, the
polydispersity and high molecular weights of the result-
ing polyethylene were consistent with single-site ca-
talysis. While the activities are significant, they are
substantially less than those derived from use of Cp2-
ZrCl2 or other simple Ti-phosphinimide complexes as
catalyst precursors under similar conditions.40,41 It is
Ack n ow led gm en t. Financial support from NSERC
of Canada and NOVA Chemicals is gratefully acknowl-
edged. Xiaoliang Gao of NOVA Chemicals is thanked
for helpful discussions.
Su p p or tin g In for m a tion Ava ila ble: Crystallographic
tables and spectra data for 6, 7, 10, and 11. This material is
available free of charge via the Internet at http://pubs.acs.org.
OM0101184