Titanium complexes of sterically demanding cage-phosphinimide ligands

Article abstract of DOI:10.1021/om0003178

The known ligand PPh(C₆H₄O₃Me₄) (1) and its analogue PCy(C₆H₄O₃Me₄) (2) have been prepared. In the latter synthesis the diphosphine species (PCy)₂(C₆H₂O₃Me₄) (3) was also isolated as a minor product. Reaction of the cage phosphines 1 and 2 with Me₃SiN₃ effected oxidation to the corresponding (trimethylsilyl)phosphinimines Me₃SiNPR(C₆H₄O₃Me₄) (R = Ph (4), Cy (5)). Subsequent reactions afforded the titanium complexes CpTiCl₂(NPR(C₆H₄O₃-Me₄)) (R = Ph (6), Cy (7)) and CpTiMe₂(NPR(C₆H₄O₃Me₄)) (R = Ph (8), Cy (9)). Preliminary screening for catalytic activity in ethylene polymerization employing either methylalumoxane (MAO) or [Ph₃C][B (C₆F₅)₄] as the activator showed minimal catalytic activity. These observations were probed via reactions of these complexes with AlMe₃, MAO, or [Ph₃C]-[B(C₆F₅)₄]. Reaction of 8 with AlMe₃ gave several products, one of which was fully characterized as the cage-rupture product CpTiMe₂(NPCy(C₆H₄O₃Me₅)(μ-AlMe₂)(AlMe₃)) (10). A similar product is inferred by the spectroscopic monitoring of the reaction of 8 with MAO. In contrast, reaction of 2 with AlMe₃ resulted only in the formation of the adduct Me₃AlPCy-(C₆H₄O₃Me₄) (11). Structural data are reported for 2, 3, 8, 10, and 11.

Full text of DOI:10.1021/om0003178

Organometallics 2000, 19, 3791-3796
3791
Tita n iu m Com p lexes of Ster ica lly Dem a n d in g
Ca ge-P h osp h in im id e Liga n d s
Charles-Antoine Carraz and Douglas W. Stephan*
School of Physical Sciences, Chemistry and Biochemistry, University of Windsor,
Windsor, Ontario, Canada N9B 3P4
Received April 18, 2000
The known ligand PPh(C6H4O3Me4) (1) and its analogue PCy(C6H4O3Me4) (2) have been
prepared. In the latter synthesis the diphosphine species (PCy)2(C6H2O3Me4) (3) was also
isolated as a minor product. Reaction of the cage phosphines 1 and 2 with Me3SiN3 effected
oxidation to the corresponding (trimethylsilyl)phosphinimines Me3SiNPR(C6H4O3Me4) (R )
Ph (4), Cy (5)). Subsequent reactions afforded the titanium complexes CpTiCl2(NPR(C6H4O3-
Me4)) (R ) Ph (6), Cy (7)) and CpTiMe2(NPR(C6H4O3Me4)) (R ) Ph (8), Cy (9)). Preliminary
screening for catalytic activity in ethylene polymerization employing either methylalumoxane
(MAO) or [Ph3C][B(C6F5)4] as the activator showed minimal catalytic activity. These
observations were probed via reactions of these complexes with AlMe3, MAO, or [Ph3C]-
[B(C6F5)4]. Reaction of 8 with AlMe3 gave several products, one of which was fully
characterized as the cage-rupture product CpTiMe2(NPCy(C6H4O3Me5)(µ-AlMe2)(AlMe3)) (10).
A similar product is inferred by the spectroscopic monitoring of the reaction of 8 with MAO.
In contrast, reaction of 2 with AlMe3 resulted only in the formation of the adduct Me3AlPCy-
(C6H4O3Me4) (11). Structural data are reported for 2, 3, 8, 10, and 11.
In tr od u ction
enes,15,17,25-27 cyclopentadienylborate,28 and multiden-
tate ligands29 have drawn recent attention. In our own
efforts, we have recently reported examinations of
titanium phosphinimide complexes. Complexes of the
form CpTi(NPR3)X2 have proven to be active single-site
catalysts for the polymerization of ethylene,30 while
catalysts derived from (R3PN)2TiX2 are highly active,
exhibiting activity which exceeds that of the constrained-
geometry catalysts under specific commercially relevant
conditions.31 An advantage to this family of catalysts is
the ease with which modification of the steric and
electronic properties of the ancillary phosphinimide
ligands is achieved. In targeting new derivatives, the
A variety of approaches are being developed in the
design of new homogeneous olefin polymerization
catalysts.1-5 Although recent efforts have broadened the
range of metals to include group 5 and 6 metals, group
4 metals remain a focus due to the current commercial
viability of these systems. It is the introduction of new
ancillary ligands that offers complexes with the poten-
tial for enhanced reactivity. In this regard, Ti and Zr
species containing diamides,6-13 aryloxides,14 borol-
lide,15 boratabenzenes,16-23 borylamides,24 trimethyl-
* To whom correspondence should be addressed. Fax: 519-973-7098.
E-mail: stephan@uwindsor.ca.
(1) Hlatky, G. G. Coord. Chem. Rev. 2000, 199, 235-329.
(2) Hlatky, G. G. Coord. Chem. Rev. 1999, 181, 243-296.
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1999, 112, 1354-1356; Angew. Chem., Int. Ed. 1999, 38, 428-447.
(4) Bochmann, M. Chem. Commun. 1996, 255-270.
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R. R. J . Am. Chem. Soc. 1999, 121, 7822-7836.
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nometallics 1998, 17, 3883-3888.
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1999, 18, 4234-4236.
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2494.
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1999, 121, 1288-1298.
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1997, 119, 3830-3831.
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10008-10009.
(25) Kowal, C. M.; Bazan, G. C. J . Am. Chem. Soc. 1996, 118,
10317-10318.
(11) Tinkler, S.; Deeth, R. J .; Duncalf, D. J .; McCamley, A. Chem.
Commun. 1996, 023, 2623-2624.
(26) Quan, R. W.; Bazan, G. C.; Kiely, A. F.; Schaefer, W. P.; Bercaw,
J . E. J . Am. Chem. Soc. 1994, 116, 4489-4490.
(27) Sperry, C. K.; Cotter, W. D.; Lee, R. A.; Lachicotte, R. J .; Bazan,
G. C. J . Am. Chem. Soc. 1998, 121, 7791-7805.
(28) Sun, Y.; Piers, W. E.; Yap, G. P. A. Organometallics 1997, 16,
2509-2513.
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8009-8015.
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tallics 1996, 15, 923-927.
(14) Nomura, K.; Naga, N.; Miki, M.; Yanagi, K.; Imai, A. Organo-
metallics 1998, 17, 2152-2154.
(29) Fokken, S.; Spaniol, T. P.; Kang, H.-C.; Massa, W.; Okuda, J .
Organometallics 1996, 15, 5069-5072.
(30) Stephan, D. W.; Stewart, J . C.; Guerin, F.; Spence, R. E. v.;
Xu, W.; Harrison, D. G. Organometallics 1999, 17, 1116-1118.
(31) 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.
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10.1021/om0003178 CCC: $19.00 © 2000 American Chemical Society
Publication on Web 08/16/2000

3792 Organometallics, Vol. 19, No. 19, 2000
Carraz and Stephan
2
3
) 2.8 Hz, 1H, CH2), 1.91 (dd, | J H-H| ) 12.5 Hz, | J H-P| ) 2.7
steric bulk of the phosphinimide ligand was proposed
as an important asset, as it could offer protection of the
Ti-N bond in the derived catalyst. Focusing on bulky
phosphine precursors, we noted the recent work of
Pringle et al.,32,33 who have reported a new class of bulky
bidentate phosphine ligands where the P atoms are
incorporated in a sterically demanding adamantane-like
cage. The structural characterization of Pd derivatives
of these ligands revealed the very large ligand cone
angles. Herein, we have adopted related ligands for the
synthesis of new titanium phosphaadamantyl-phos-
phinimide derivatives. Reactions of these species with
Lewis acids are investigated, and the implications for
the design of new single-site olefin polymerization
catalysts are considered.
Hz, 1H, CH2), 1.77 (m, 1H, CH2), 1.77 (m, 1H, CH2), 1.70 (m,
3
1H, CH2), 1.56 (s, 3H, CH3), 1.43 (s, 3H, CH3), 1.40 (d, | J H-P
|
) 12.6 Hz, 3H, CH3), 1.22 (d, |J 3H-P| ) 12.6 Hz, 3H, CH3), 0.52
(s, 9H, Si(CH3)3); 13C{1H} NMR (C6D6, 25 °C, δ) 134.3 (d, | J C-P
|
2
4
1
) 8 Hz, Ph), 131.6 (d, | J C-P| ) 3 Hz, Ph), 130.4 (d, | J C-P| )
3
76 Hz, Ph), 128.9 (d, | J C-P| ) 11 Hz, Ph), 97.2 (s, quat), 96.7
1
1
(s, quat), 75.4 (d, | J C-P| ) 75 Hz, quat), 74.0 (d, | J C-P| ) 65
Hz, quat), 43.4 (d, |J C-P| ) 5 Hz, CH2), 40.9 (s, CH2), 28.2 (s,
CH3), 28.0 (s, CH3), 21.8 (s, CH3), 21.2 (s, CH3), 4.9 (s, Si(CH3)3).
Anal. Calcd for C19H30NO3PSi: C, 60.13; H, 7.97; N, 3.69.
Found: C, 59.95; H, 7.81; N, 3.42. 5: yield 82%; 31P{1H} NMR
1
(C6D6, 25 °C, δ) -2.7 (s); H NMR (C6D6, 25 °C, δ): 2.58 (dd,
2
3
| J H-H| ) 12.8 Hz, | J H-P| ) 5.0 Hz, 1H, CH2), 1.93 (2H), 1.41-
1.73 (m, 10H), 1.42 (s, 3H, CH3), 1.31 (s, 3H, CH3), 1.26 (d,
3
3
| J H-P| ) 12.6 Hz, 3H, CH3), 1.23 (d, | J H-P| ) 11.6 Hz, 3H,
CH3), 1.07 (m, 2H), 0.39 (s, 9H, Si(CH3)3); 13C{1H} NMR (C6D6,
1
25 °C, δ) 96.4 (s, quat), 96.0 (s, quat), 74.9 (d, | J C-P| ) 33 Hz,
1
quat), 74.1 (d, | J C-P| ) 27 Hz, quat), 43.9 (d, |J C-P| ) 5 Hz,
Exp er im en ta l Section
CH2), 40.5 (s), 34.7 (s), 33.9 (s), 29.3 (s), 28.1 (s), 28.0 (s), 27.9
(s), 27.4 (d, |J C-P| ) 12 Hz), 26.7 (d, |J C-P| ) 12 Hz), 26.3 (s),
Gen er a l Da ta . All preparations were done under an
atmosphere of dry, O2-free N2 employing both Schlenk line
techniques and an Innovative Technologies or Vacuum Atmo-
spheres inert-atmosphere glovebox. Solvents were purified
employing a Grubb type column system manufactured by
Innovative Technology. All organic reagents were purified by
conventional methods. 1H, 13C{1H}, and 31P{1H} NMR spectra
were recorded on Bruker Avance 300 and 500 spectrometers
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 spectra were
referenced to 85% H3PO4. Guelph Chemical Laboratory (Guel-
ph, Ontario, Canada) performed combustion analyses. The
ligand PPh(C6H4O3Me4) (1) was prepared as reported in the
literature.35
23.0 (d, |J C-P| ) 4 Hz), 4.9 (s, Si(CH3)3). Anal. Calcd for C19H36
-
NO3PSi: C, 59.19; H, 9.41; N, 3.63. Found: C, 59.01; H, 9.11;
N, 3.45.
Syn th esis of Cp TiCl2(NP R(C6H4O3Me4)) (R ) P h (6), Cy
(7)). These compounds were prepared in a similar manner,
and thus only one preparation is detailed. To 311 mg (1.42
mmol) of CpTiCl3 and 537 mg (1.42 mmol) of 4 was added 50
mL of benzene to give a cloudy yellow mixture. Heating for 3
h at 80 °C gave a clear deep yellow solution. Cooling and
removal of volatiles gave 635 mg (91%) of the yellow solid
product 6. 6: 31P{1H} NMR (C6D6, 25 °C, δ) -8.3 (s); 1H NMR
(C6D6, 25 °C, δ) 8.22 (m, 2H, Ph), 7.67 (m, 3H, Ph), 6.54 (s,
2
3
5H, Cp), 2.82 (dd, | J H-H| ) 14.0 Hz, | J H-P| ) 2.8 Hz, CH2),
2
2
1.68 (d, | J H-H| ) 13.9 Hz, CH2), 1.61 (d, | J H-H| ) 13.9 Hz,
3
CH2), 1.45 (m, 1H, CH2), 1.42 (s, 3H, CH3), 1.34 (d, | J H-P| )
Syn th esis of P Cy(C6H4O3Me4) (2) a n d (P Cy)2-
(C6H2O3Me4) (3). To 200 mL of a stirred 5 M solution of HCl
was added 20 g of 2,4-pentanedione (0.2 mol), 20 mL of MeOH,
and 3 g (25.8 mmol) of CyPH2. After the mixture was stirred
for 24 h, the volatiles were removed in vacuo and the resulting
orange oil was triturated with 200 mL of water to give a pale
yellow solid that was recrystallized from MeCN to give 4.6 g
(60%) of the white crystalline product 2. Successive recrystal-
lization from the mother liquor yielded a small crop of crystals
of 3 suitable for X-ray crystallography. 2: 31P{1H} NMR (C6D6,
25 °C, δ) -12.6 (s); 1H NMR (C6D6, 25 °C, δ) 1.89 (m, 1H),
1.68 (br m, 1H), 1.54-1.68 (m, 7H), 1.11-1.33 (m, 18H); 13C-
{1H} NMR (C6D6, 25 °C, δ) 97.6 (s, quat), 95.9 (s, quat), 73.1
(d, |J C-P| ) 26 Hz, quat), 72.4 (d, |J C-P| ) 13 Hz, quat), 45.6
(d, |J C-P| ) 11 Hz, CH2), 38.5 (s, CH2), 33.5 (d, |J C-P| ) 22 Hz,
CH2), 31.9 (d, |J C-P| ) 24 Hz, CH3), 30.1 (d, |J C-P| ) 7 Hz,
CH2), 29.6 (d, |J C-P| ) 22 Hz, CH3), 28.3 (d, |J C-P| ) 11 Hz,
CH), 28.0 (s, CH3), 27.6 (s, CH3), 26.9 (d, |J C-P| ) 7 Hz, CH2),
26.3 (d, |J C-P| ) 13 Hz, CH3), 26.0 (s, CH2). Anal. Calcd
for C16H27O3P: C, 64.41; H, 9.12. Found: C, 64.30; H, 9.01. 3:
3
9.7 Hz, CH3), 1.20 (s, 3H, CH3), 1.10 (d, 3H, | J H-P| ) 13.5
Hz); 13C{1H} NMR (C6D6, 25 °C, δ) 134.3 (d, | J C-P| ) 7 Hz,
2
2
Ph), 133.5 (s, Ph), 129.5 (d, | J C-P| ) 11 Hz), 124.9 (s, Ph),
1
116.4 (s, Cp), 97.6 (s, quat), 96.9 (s, quat), 75.9 (d, | J C-P| ) 11
Hz, quat), 75.2 (s, quat), 42.2 (d, |J C-P| ) 6 Hz, CH2), 40.9 (s,
CH2), 27.8 (s, CH3), 27.6 (s, CH3), 22.3 (s, CH3), 21.4 (s, CH3).
Anal. Calcd for C21H26Cl2NO3PTi: C, 51.45; H, 5.35; N, 2.86.
Found: C, 51.05; H, 5.11; N, 2.52. 7: yield 91%; 31P{1H} NMR
1
(C6D6, 25 °C, δ) 4.1 (s); H NMR (C6D6, 25 °C, δ) 6.50 (s, 5H,
2
3
Cp), 2.73 (dd, | J H-H| ) 13.7 Hz, | J H-P| ) 2.6 Hz, CH2), 2.1
3
(m, 1H), 1.96 (m, 2H), 1.43-1.59 (m, 3H), 1.39 (d, | J H-P| )
3
13.1 Hz, CH3), 1.37 (s, 3H, CH3), 1.26 (d, | J H-P| ) 12.2 Hz,
CH3), 1.18 (s, 3H, CH3), 0.89-1.13 (m, 4H); 13C{1H} NMR
(C6D6, 25 °C, δ) 115.8 (s, Cp), 96.9 (s, quat), 96.2 (s, quat), 75.5
1
1
(d, | J C-P| ) 13 Hz, quat), 75.1 (d, | J C-P| ) 22 Hz, quat), 43.4
(d, |J C-P| ) 5 Hz, CH2), 40.6 (s, CH2), 35.7 (d, |J C-P| ) 50 Hz,
CH), 28.9 (d, |J C-P| ) 4 Hz, CH2), 28.2 (d, |J C-P| ) 4 Hz, CH2),
27.6 (s, CH3), 27.4 (s, CH3), 27.1 (d, |J C-P| ) 13 Hz, CH2), 26.6
(d, |J C-P| ) 12 Hz, CH2), 25.8 (s, CH2), 23.8 (s, CH3), 23.6 (s,
CH3). Anal. Calcd for C21H32Cl2NO3PTi: C, 50.83; H, 6.50; N,
2.82. Found: C, 50.35; H, 6.21; N, 2.42.
1
31P{1H} NMR (C6D6, 25 °C, δ) 0.6; H NMR (C6D6, 25 °C, δ)
0.87-2.5 (br, m).
Syn th esis of Cp TiMe2(NP R(C6H4O3Me4)) (R ) P h (8),
Cy (9)). These compounds were prepared in a similar manner,
and thus only one preparation is detailed. To a stirred solution
of 100 mg (0.204 mmol) of 6 in 5 mL of Et2O was added
dropwise 0.34 mL (1.021 mmol) of a 3.0 M ether solution of
MeMgBr. After 1 h the solvent was evacuated, leaving a pale
beige solid which was extracted with 3 × 10 mL of hexane.
The extracts were filtered and pumped dry, yielding 77 mg
(84%) of the pale yellow solid product. 8: 31P{1H} NMR (C6D6,
25 °C, δ) -18.1 (s); 1H NMR (C6D6, 25 °C, δ) 8.36 (m, 2H, Ph),
Syn th esis of Me3SiNP R(C6H4O3Me4) (R ) P h (4), Cy
(5)). These compounds were prepared in a similar manner,
and thus only one preparation is detailed. To 1.38 g (4.72
mmol) of 1 was added 652 mg (5.67 mmol) of (CH3)3SiN3 to
form a pale yellow slush. Heating for 3 h melted the mixture
to give a clear, brown liquid, which was cooled to give 1.5 g
(85%) of the waxy, brown solid product 4. 4: 31P{1H} NMR
1
(C6D6, 25 °C, δ) -12.1 (s); H NMR (C6D6, 25 °C, δ) 8.34 (m,
2
3
2H, Ph), 7.24 (m, 3H, Ph), 2.81 (dd, | J H-H| ) 12.4 Hz, | J H-P
|
2
7.11 (m, 3H, Ph), 6.26, (s, 5H, Cp), 2.83 (dd, | J H-H| ) 13.5
(32) Gee, V.; Orpen, A. G.; Phetmung, H.; Pringle, P. G.; Pugh, R. I.
3
Hz, | J H-P| ) 2.9 Hz, CH2), 1.65 (m, 3H, CH2), 1.46 (s, CH3),
Chem. Commun. 1999, 901-902.
(33) Budzelaar, P. H.; Drent, E.; Pringle, P. G. Eur. Patent
97302079, 1996.
3
3
1.38 (d, | J H-P| ) 13.2 Hz, CH3), 1.31 (s, CH3), 1.17 (d, | J H-P
|
p
) 12.8 Hz, CH3), 0.88 (s, 3H, TiCH3), 0.82 (s, 3H, TiCH3); 13C-

Ti Complexes of Cage-Phosphinimide Ligands
Organometallics, Vol. 19, No. 19, 2000 3793
Ta ble 1. Cr ysta llogr a p h ic P a r a m eter sa
2
3
8
10
11
formula
fw
a, Å
b, Å
C
16H27O3P
C22H32O2P2
390.42
8.3606(2)
14.4883(3)
18.3934(4)
90
2228.01(9)
orthorhombic
P212121
1.164
C23H32NO3PTi
449.37
15.967(3)
14.966(5)
20.101(4)
90
4803(2)
orthorhombic
Pbca
1.243
8
0.445
22 635
4212
C29H56Al2NO3PTi
599.58
18.8861(5)
19.0758(4)
10.0047(3)
90
3604.37(16)
orthorhombic
Pnn2
1.105
4
0.357
16 188
C19H36AlO3P
370.43
298.35
17.746(3)
10.070(3)
9.139(2)
91.56(2)
1632.6(6)
monoclinic
P21/c
1.214
4
0.174
8105
2844
181
0.0342
0.1193
1.026
9.2469(2)
11.9776(4)
19.9925(6)
102.1940(10)
2164.32(11)
monoclinic
P21/n
1.137
4
0.181
10 630
c, Å
â, deg
V, Å3
cryst syst
space group
d(calcd) g cm-3
Z
4
µ, mm-1
no. of data collected
no. of data used
no. of variables
R, %
0.208
11 461
3888
6173
334
0.0854
0.2000
3761
217
0.0480
0.1227
191
262
0.0856
0.2221
1.633
0.0683
0.1822
1.260
Rw, %
goodness of fit
1.118
0.879
All data collected at 24 °C with Mo KR radiation (λ ) 0.710 69 Å). R ) ∑||Fo| - |Fc||/∑|Fo|, Rw ) [∑[w(Fo - Fc2)2]/∑[w(Fo2)2]]0.5
.
a
2
2
{1H} NMR (C6D6, 25 °C, δ) 134.3 (d, | J C-P| ) 9 Hz, Ph), 132.4
2.0 mL of dry toluene. A 500 equiv amount of a 10 wt % toluene
2
(s, Ph), 129.6 (d, | J C-P| ) 11 Hz), 124.9 (s, Ph), 113.6 (s, Cp),
solution of methylaluminoxane (MAO) was added to the flask.
Alternatively, the compound 8 or 9 was 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 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 temper-
ature. The polymerization was stopped by the injection of a
1.0 M HCl/methanol solution, the total reaction time was
noted, and the polymer was isolated.
1
97.4 (s, quat), 96.8 (s, quat), 75.9 (d, | J C-P| ) 32 Hz, quat),
1
75.1 (d, | J C-P| ) 30 Hz, quat), 42.8 (d, |J C-P| ) 6 Hz, CH2),
40.9 (s, CH2), 32.3 (s, TiCH3), 30.5 (s, TiCH3), 28.0 (s, CH3),
27.8 (s, CH3), 22.3 (s, CH3), 21.1 (s, CH3). 9: yield 91%; 31P-
1
{1H} NMR (C6D6, 25 °C, δ) -7.6 (s); H NMR (C6D6, 25 °C, δ)
2
3
6.35 (s, 5H, Cp), 2.79 (dd, | J H-H| ) 13.2 Hz, | J H-P| ) 2.7 Hz,
CH2), 2.03-2.33 (m, 3H, CH2), 1.45-1.83 (m, 10H), 1.50 (s,
2
3
3H, CH3), 1.43 (d, | J H-P| ) 11.3 Hz, CH3), 1.38 (d, | J H-P| )
11.7 Hz, CH3), 1.37 (s, 3H, CH3), 0.96-1.31 (m, 4H), 0.87 (s,
3H, TiCH3), 0.84 (s, 3H, TiCH3); 13C{1H} NMR (C6D6, 25 °C,
X-r a y Da ta Collection a n d Red u ction . X-ray-quality
crystals of 2, 3, 8, 10, and 11 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 experi-
ments were performed on a Siemens SMART System CCD
diffractometer collecting 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. The data sets were collected (4.5°
< 2θ < 45-50.0°). A measure of decay was obtained by
recollecting 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 absorption correction based
on redundant data was applied to each data set. Subsequent
solution and refinement was performed using the TEXSAN
solution package operating on a SGI Indy computer. The
1
δ) 111.5 (s, Cp), 96.8 (s, quat), 96.3 (s, quat), 75.3 (d, | J C-P| )
1
36 Hz, quat), 75.0 (d, | J C-P| ) 23 Hz, quat), 43.4 (s, CH2),
42.5 (s, TiCH3), 42.4 (s, TiCH3), 40.6 (s, CH2), 35.3 (d, |J C-P| )
53 Hz, CH), 29.5 (s, CH2), 28.3 (d, |J C-P| ) 4 Hz, CH2), 28.1 (s,
CH3), 28.0 (s, CH3), 27.5 (d, |J C-P| ) 12 Hz, CH2), 26.9 (d, |J C-P
) 12 Hz, CH2), 23.9 (s, CH3), 23.5 (s, CH3).
|
Syn t h esis of Cp TiMe2(NP Cy(C6H 4O3Me5)(µ-AlMe2)-
(AlMe3)) (10). To a solution of 80 mg (0.178 mmol) of 9 in 1
mL of hexane was added dropwise 0.3 mL (0.6 mmol) of a 2.0
M heptane solution of Al(CH3)3. The solution was filtered and
placed in an NMR tube. After 16 h, crystals suitable for X-ray
crystallography had formed. 31P{1H} NMR (C6D6, 25 °C, δ):
1
46.4 (br s), minor impurity at 45.1. H NMR (C6D6, 25 °C, δ):
6.11, (s, 5H, Cp), 2.86 (m, 1H), 2.46 (m, 2H), 2.20 (m, 1H), 1.94
(m, 2H), 1.69 (m, 2H), 1.41-1.59 (m, 5H), 1.39 (s, 1H), 1.28 (s,
3H), 0.79-1.23 (m, 14H), -0.07 (br s, 9H, Al(CH3)3), -0.25 (s,
6H, Al(CH3)3).
Syn th esis of Cy(ca ge)P AlMe3. To a stirred benzene (5
mL) solution of 2 (93 mg, 0.31 mmol) was added dropwise with
stirring 0.60 mL (1.2 mmol) of a 2.0 M heptane solution of
AlMe3. After the mixture was stirred for 3 h, a white
precipitate was formed, which was filtered and dried to give
107 mg (93%) of the product. Recrystallization from benzene
gave crystals suitable for X-ray crystallography. 31P{1H} NMR
(C6D6, 25 °C, δ): -17.9 (s). 1H NMR (C6D6, 25 °C, δ): 2.00 (dd,
2
2
reflections with Fo > 3σFo were used in the refinements.
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.34 The heavy-atom positions were determined using
direct methods employing either the SHELX or SHELXTL
direct-methods routine. The remaining non-hydrogen atoms
were located from successive difference Fourier map calcula-
tions. 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 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 fac-
tors. 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
2
3
| J H-H| ) 13.3 Hz, | J H-P| ) 5.1 Hz, CH2), 1.89 (m, 2H), 1.72
3
(m, 1H), 1.27-1.57 (m, 8H), 1.38 (d, | J H-P| ) 12.3 Hz, CH3),
3
1.35 (s, 3H, CH3), 1.28 (d, | J H-P| ) 11.1 Hz, CH3), 1.26 (s, 3H,
CH3), 1.04 (m, 1H), 0.95 (m, 2H), -0.22 (s, 9H, Al(CH3)3). 13C-
{1H} NMR (C6D6, 25 °C, δ): 96.7 (s, quat), 96.3 (s, quat), 73.3
1
2
(s, quat), 72.8 (d, | J C-P| ) 8 Hz, quat), 44.4 (d, | J C-P| ) 5 Hz,
2
CH2), 39.5 (s, CH2), 32.8 (d, | J C-P| ) 10 Hz, CH3), 32.5 (s, CH2),
29.3 (s, CH), 28.9 (d, |J C-P| ) 11 Hz, CH3), 28.3 (s, CH2), 27.8
(s, CH3), 27.7 (d, |J C-P| ) 13 Hz, CH2), 27.0 (d, |J C-P| ) 13 Hz,
CH2), 26.3 (s, CH2), -5.3 (s, Al(CH3)3). Anal. Calcd for C19H26O3-
PAl: C, 59.07; H, 8.37; Found: C, 58.85; H, 8.22.
Eth ylen e P olym er iza tion . A solution of 6-10 µmol of 6
or 7 in 2.0 mL of dry toluene was added to a flask containing
(34) Cromer, D. T.; Mann, J . B. Acta Crystallogr. Sect. A: Cryst.
Phys., Theor. Gen. Crystallogr. 1968, A24, 390.

3794 Organometallics, Vol. 19, No. 19, 2000
Carraz and Stephan
F igu r e 1. ORTEP drawing of 2. Thermal ellipsoids of 30%
probability are shown; all but the bridging methyl hydrogen
atoms are omitted for clarity.
F igu r e 2. ORTEP drawing of 3. Thermal ellipsoids of 30%
probability are shown; all but the bridging methyl hydrogen
atoms are omitted for clarity.
Sch em e 1
Sch em e 2
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. In the cases where the space group is acentric,
model inversion and re-refinement was employed to determine
the correct enantiomorph. 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.
oxidation to the corresponding (trimethylsilyl)phosphin-
imines Me3SiNPR(C6H4O3Me4) (R ) Ph (4), Cy (5)) as
confirmed by 1H, 31P, and 13C NMR spectroscopy. These
products were isolated in 85 and 82% yields, respec-
tively. Analogous attempts to oxidize the even more
sterically demanding phosphaadamantyl ligand derived
from hexafluoroacetylacetone, PPh(C6H4O3(CF3)4), failed.
No reaction between the phosphine with Me3SiN3 was
observed, even under reflux conditions in xylene for 14
days.
Resu lts a n d Discu ssion
Epstein and Buckler35 showed in 1961 that the
reaction of PhPH2 with 2,4-pentanedione affords the
“cage-phosphine” PPh(C6H4O3Me4) (1). In the corre-
sponding reaction of CyPH2, they described only the
isolation of the diphosphine species, formulated as
(PCy)2(C6H2O3Me4) (3) (Scheme 1). While we have
reproduced the preparation of 1 using their method, we
have also isolated the phosphine PCy(C6H4O3Me4) (2)
as a white crystalline product in 60% yield from the
analogous reaction of CyPH2. In addition, the species 3
was isolated as a minor product. The formulations of
Reaction of 4 and 5 with 1 equiv of CpTiCl3 in
refluxing benzene for 3 h afforded yellow products in
greater than 90% yields. These products were formu-
lated as CpTiCl2(NPR(C6H4O3Me4)) (R ) Ph (6), Cy (7))
(Scheme 2) on the basis of NMR data. Subsequent
reaction of 6 and 7 with excess MeMgBr in diethyl ether
gave pale beige solids in 84% and 91% yields, respec-
tively. These species were formulated as the complexes
CpTiMe2(NPR(C6H4O3Me4)) (R ) Ph (8), Cy (9)). NMR
data supported these formulations, and in the case of
8, this was confirmed crystallographically (Figure 3).
The metric parameters of 8 are unexceptional.30,31,37 As
in previously reported species, the Ti-N-P vector is
approximately linear (171.3(2)°), while the Ti-N bond
distance of 1.806(3) Å is also typical.
1
these compounds were confirmed by H, 13C, and 31P
NMR spectroscopy. Compounds 2 and 3 were also
characterized by X-ray crystallography (Figures 1 and
2). Compound 2 was confirmed as the trioxaphos-
phaadamantyl species. In the case of 3, the X-ray data
confirmed that the only isomer formed was the 1,3-
diphosphine cage. This preference can be explained via
the mechanistic considerations described by Bekiaris et
al.36 in studies of closely related systems.
Heating these phosphaadamantyl ligands, 1 and 2,
in the presence of a slight excess of Me3SiN3 effected
Preliminary screening (1 atm, 25 °C) for catalytic
activity in ethylene polymerization was performed for
(35) Epstein, M.; Buckler, S. A. J . Am. Chem. Soc. 1961, 83, 3279.
(36) Bekiaris, G.; Lork, E.; Offermann, W.; Roeshenthaler, G. V.
Chem. Ber. 1997, 130, 1547-1550.
(37) Dehnicke, K.; Kreiger, M.; Massa, W. Coord. Chem. Rev. 1999,
182, 19-65.

Ti Complexes of Cage-Phosphinimide Ligands
Organometallics, Vol. 19, No. 19, 2000 3795
F igu r e 4. ORTEP drawing of 10. Thermal ellipsoids of
30% probability are shown; all but the bridging methyl
hydrogen atoms are omitted for clarity. Selected bond
distances (Å) and angles (deg) are as follows: Ti(1)-N(1),
1.997(5); Ti(1)-C(7), 2.132(8); Ti(1)-C(6), 2.124(10); Al(1)-
O(1), 1.886(5); Al(1)-N(1), 1.972(6); Al(1)-C(26), 1.970(10);
Al(1)-C(25), 1.996(10); Al(2)-O(1), 1.953(5); Al(2)-C(27),
1.991(10); Al(2)-C(29), 2.025(11); Al(2)-C(28), 2.035(12);
P(1)-N(1), 1.624(5); N(1)-Ti(1)-C(7), 105.3(3); N(1)-Ti-
(1)-C(6), 108.0(3); C(7)-Ti(1)-C(6), 92.6(5); O(1)-Al(1)-
N(1), 94.6(2); O(1)-Al(1)-C(26), 110.9(4); N(1)-Al(1)-
C(26), 110.3(4); O(1)-Al(1)-C(25), 107.8(4); N(1)-Al(1)-
C(25), 113.6(4); C(26)-Al(1)-C(25), 117.2(5); O(1)-Al(2)-
C(27), 104.0(4); O(1)-Al(2)-C(29), 111.8(4); C(27)-Al(2)-
C(29), 114.6(6); O(1)-Al(2)-C(28), 104.9(4); C(27)-Al(2)-
C(28), 113.0(6); C(29)-Al(2)-C(28), 108.1(6); P(1)-N(1)-
Al(1), 109.6(3); P(1)-N(1)-Ti(1), 132.1(3); Al(1)-N(1)-
Ti(1), 118.1(3); Al(1)-O(1)-Al(2), 120.1(3).
F igu r e 3. ORTEP drawing of 8. Thermal ellipsoids of 30%
probability are shown; all but the bridging methyl hydrogen
atoms are omitted for clarity. Selected bond distances (Å)
and angles (deg) are as follows: Ti(1)-N(1), 1.806(3); Ti-
(1)-C(23), 2.162(5); Ti(1)-C(22), 2.165(6); P(1)-N(1), 1.565-
(3); N(1)-Ti(1)-C(23), 103.3(2); N(1)-Ti(1)-C(22), 102.0-
(2); C(23)-Ti(1)-C(22), 99.7(3); P(1)-N(1)-Ti(1), 171.3(2).
compounds 6 and 7 in the presence of 500 equiv of
methylalumoxane (MAO). Alternatively, the compounds
8 and 9 were combined with [Ph3C][B(C6F5)4] under an
ethylene atmosphere at 25 °C. In all cases, only a
minimal amount of polymer was observed under these
conditions. These low activities (<10 g of PE/(mmol/h))
stand in marked contrast to our previous reports of
active olefin polymerization catalysts derived from the
complexes (Cp‡)TiX2(NPR3) (Cp‡ ) Cp, t-BuCp; X ) Cl,
Me; R ) t-Bu, i-Pr, Cy) and (R3PN)2TiX2.30,31
The interaction of the complexes of these cage-
phosphinimides with aluminum reagents was investi-
gated. Initially, reaction of 8 with AlMe3 was used as a
model for the interaction with MAO. Monitoring by 31P-
{1H} NMR spectroscopy revealed the formation of two
products, a major species exhibiting a resonance at 46.4
1
ppm and a minor impurity at 45.1 ppm. The H NMR
spectrum was complex and precluded structural formu-
lation of the products. Fortunately, crystals of the major
product 10 were isolated upon standing. An X-ray
diffraction study provided the unequivocal identification
of 10 as CpTiMe2(NPCy(C6H4O3Me5)(µ-AlMe2)(AlMe3))
(Figure 4). In this species, the phosphaadamantyl cage
has been split open by the transfer of a methyl group
from AlMe3 to one of the quaternary carbons with
cleavage of the adjacent C-O bond. The resulting
oxygen atom bridges AlMe2 and AlMe3 groups, while the
AlMe2 is also bound to the phosphinimide nitrogen
atom. The reduced P-N and Ti-N bond strengths in
10 compared to 8 are reflected in the corresponding
distances of 1.997(5) and 1.624(5) Å, respectively.
In contrast to the reaction of 8, reaction of the free
phosphine 2 with AlMe3 resulted only in the formation
of the adduct Me3AlPCy(C6H4O3Me4) (11). The formula-
tion of this white solid, isolated in 93% yield, was
confirmed by X-ray crystallography (Figure 5). The
Al-P bond length in the phosphine-alane adduct is
2.5526(11) Å.
F igu r e 5. ORTEP drawing of 11. Thermal ellipsoids of
30% probability are shown; all but the bridging methyl
hydrogen atoms are omitted for clarity. Selected bond
distances (Å) and angles (deg) are as follows: Al(1)-C(17),
1.971(3); Al(1)-C(19), 1.975(3); Al(1)-C(18), 1.973(3); Al-
(1)-P(1), 2.5526(11); C(17)-Al(1)-C(19), 114.0(2); C(17)-
Al(1)-C(18), 115.3(2); C(19)-Al(1)-C(18), 115.1(2); C(17)-
Al(1)-P(1), 103.87(10); C(19)-Al(1)-P(1), 104.18(11); C(18)-
Al(1)-P(1), 102.09(11); C(1)-P(1)-Al(1), 114.77(9).
Monitoring of the reaction of 8 with MAO directly by
31P NMR spectroscopy revealed the presence of several
products with resonances around 45 ppm. The similarity
of this chemical shift range to that seen for the reaction
with AlMe3 suggests that cage rupture may have occur-
red under polymerization conditions. It is interesting

3796 Organometallics, Vol. 19, No. 19, 2000
Carraz and Stephan
that the AlMe3 does not effect cage rupture of ligand 2;
rather, 11 is formed cleanly. These observations suggest
that an interaction of Al with the Ti-bound phosphin-
imide N atom may be involved in the initiation of the
process of cage rupture. Reactions of 8 and 9 with [Ph3C]-
[B(C6F5)4] were also monitored by 31P{1H} NMR spec-
troscopy, revealing the formation of a handful of prod-
ucts, none of which could be fully characterized. Although
unconfirmed, we speculate that ligand rupture is also
effected by the Lewis acidic reagent [Ph3C][B(C6F5)4].
In summary, titanium derivatives of the sterically
demanding cage-phosphinimide ligands have been syn-
thesized. The corresponding Ti complexes react with
Lewis acids to effect ligand cage rupture, affording a
mixture of Ti products, observations that do not augur
well for single-site catalysis. Current efforts are focused
on ligand modifications that provide enhanced Ti-N
bond stability and are suited to the generation of a
single active center.
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: Tables giving X-ray
data for 2, 3, 8, 10, and 11; data are also given as CIF files.
This material is available free of charge via the Internet at
http://pubs.acs.org.
OM0003178