Silica-Grafted Borato Cocatalysts for Olefin Polymerization Modeled by Silsesquioxane Borato Complexes

Article abstract of DOI:10.1021/om990855o

The syntheses and reactivity studies of silsesquioxane-borato complexes are described. Treatment of B(C₆F₅)₃ with (c-C₅H₉)₇Si₈O₁₂(OH) and (c-C₅H₉)₇Si₇O₉(OH) ₃ in the presence of a Br?nsted base yields the silsesquioxane-borates X⁺{[(c-C₅H₉)₇Si₈O ₁₃]B(C₆F₅)₃}^- (1a, X⁺ = PhN(H)Me₂⁺; 1b, X⁺ = Et₃NH⁺) and X⁺{[(c-C₅H₉)₇Si₇(OH) ₂O₁₀]B(C₆F₅)₃} ^- (1b, X⁺ = PhN-(H)Me₂⁺; 2b, X⁺ = Et₃NH⁺), respectively. When the more nucleophilic base pyridine is used, (C₆F₅)₃B·NC₅H₅ (3) is formed instead, demonstrating the competition between B(C₆F₅)₃ and H⁺ to react with the amine. The dimethylaniline in 1a and 2a is readily exchanged by NEt₃ to form 1b and 2b. With the nucleophilic Lewis base NC₅H₅, the B-O bond in 1a and 2a is split, yielding (C₆F₅)₃B·NC₅H₅ (3) and the free silsesquioxanes. Complexes 1 and 2 rapidly undergo hydrolysis under formation of the hydroxyl complexes X⁺{(C₆F₅)₃BOH}^- (4a, X⁺ = PhN(H)Me₂⁺; 4b, X⁺ = Et₃NH⁺). Likewise, alcoholysis of 1a and 2a with i-PrOH yields the alkoxide {PhN(H)Me₂}⁺{i-PrOB(C₆F₅) ₃}^- (5). The B-O bond is only moderately stable toward early-transition-metal alkyls. Nevertheless, Cp₂Zr(CH₂Ph)₂ + 1a and Zr(CH₂Ph)₄ + 2a form single-site ethylene polymerization catalysts. Detailed reactivity studies demonstrated that both B-O and B-C bond splitting plays a crucial role, as not 1a and 2a, but their decomposition product B(C₆F₅)₃ is the actual cocatalyst. The solid-state structures of 1a and 4b were determined by single-crystal X-ray analysis.

Full text of DOI:10.1021/om990855o

Organometallics 2000, 19, 809-816
809
Silica -Gr a fted Bor a to Coca ta lysts for Olefin
P olym er iza tion Mod eled by Silsesqu ioxa n e-Bor a to
Com p lexes
,
†
†
‡
Robbert Duchateau,* Rutger A. van Santen, and G. P. A. Yap
Dutch Polymer Institute/ Schuit Institute of Catalysis, Eindhoven University of Technology,
P.O. Box 513, 5600 MB Eindhoven, The Netherlands, and University of Ottawa,
Ottawa K1N 6N5, Ontario, Canada
Received October 25, 1999
The syntheses and reactivity studies of silsesquioxane-borato complexes are described.
Treatment of B(C
a Brønsted base yields the silsesquioxane-borates X {[(c-C
6
F
5
)
3
with (c-C
5
H
9
)
7
Si
8
O
12(OH) and (c-C
5
H
9
)
5
7
Si
7
O
9
(OH)
3
in the presence of
+
-
+
H
9
)
7
Si
8
O
13]B(C
6
F
5
)
3
} (1a , X
+
+
+
+
-
+
)
PhN(H)Me
2
; 1b, X ) Et
3
NH ) and X {[(c-C
NH ), respectively. When the more nucleophilic base pyridine is used,
and
5
H
9
)
7
Si
7
(OH)
2
O
10]B(C
6
F
5
)
3
} (1b, X ) PhN-
+
+
+
(
H)Me
2
; 2b, X ) Et
3
(C
6
+
F
5
)
3
B‚NC (3) is formed instead, demonstrating the competition between B(C F )
5
H
5
6 5 3
H to react with the amine. The dimethylaniline in 1a and 2a is readily exchanged by NEt
to form 1b and 2b. With the nucleophilic Lewis base NC , the B-O bond in 1a and 2a is
split, yielding (C B‚NC (3) and the free silsesquioxanes. Complexes 1 and 2 rapidly
3
5
H
5
6
F
5
)
3
5 5
H
+
-
+
undergo hydrolysis under formation of the hydroxyl complexes X {(C
; 4b, X ) Et
alkoxide {PhN(H)Me
6
F
5
)
3
BOH} (4a , X )
+
+
+
PhN(H)Me
2
3
NH ). Likewise, alcoholysis of 1a and 2a with i-PrOH yields the
+
-
2
} {i-PrOB(C
6
F
5
)
3
} (5). The B-O bond is only moderately stable toward
Zr(CH Ph) + 1a and Zr(CH Ph) + 2a form
early-transition-metal alkyls. Nevertheless, Cp
single-site ethylene polymerization catalysts. Detailed reactivity studies demonstrated that
2
2
2
2
4
both B-O and B-C bond splitting plays a crucial role, as not 1a and 2a , but their
decomposition product B(C
6 5 3
F ) is the actual cocatalyst. The solid-state structures of 1a and
4
b were determined by single-crystal X-ray analysis.
+
+
In tr od u ction
) PhN(H)Me2 , Ph3C ) and B(C6F5)3 have been found
4
to effectively activate metallocenes. Hence, immobilized
For the industrial production of polyolefins hetero-
geneous catalysts are generally preferred over homo-
geneous ones. For example, the polymers formed in gas-
phase, slurry, or bulk-monomer processes are usually
of high density and are insoluble in most solvents. For
these processes only heterogeneous catalysts allow
polymer morphology control and narrow particle size
borato cocatalysts might also afford well-defined het-
erogeneous olefin polymerization catalysts. Reports on
immobilization of boron-based cocatalysts have ap-
peared nearly exclusively in patent literature. Most
commonly the borates are physisorbed or tethered to
5,6
(
2) (a) Chien, J . C. W.; He, D. J . Polym. Sci., A: Polym. Chem. 1991,
2
1
9, 1603. (b) Collins, S.; Kelly, W. M.; Holden, D. A. Macromolecules
992, 25, 1780. (c) Soga, K.; Kaminaka, M. Makromol. Chem., Rapid
1
distribution and avoid reactor fouling. Besides tradi-
tional heterogeneous olefin polymerization catalysts
(
Commun. 1992, 13, 221. (d) Soga, K.; Kaminaka, M. Makromol. Chem.
1993, 194, 1745. (e) Kaminsky, W.; Renner, F. Makromol. Chem., Rapid
Commun. 1993, 14, 239. (f) J aniak, C.; Rieger, B. Angew. Makromol.
Chem. 1994, 47, 215. (g) Sacchi, M. C.; Zucchi, D.; Titto, I.; Locatelli,
P.; Dall’Occo, T. Macromol. Rapid. Commun. 1995, 16, 581. (h)
Kamfjord, T.; Wester, T. S.; Rytter, E. Macromol. Rapid Commun.
Ziegler-Natta, Phillips),1 immobilization of well-
defined homogeneous metallocene catalysts is receiving
increasing interest.2,3 The most common immobilization
technique consists of adsorption of a combination of
1
998, 19, 505. (i) Hlatky, G. G. Coord. Chem. Rev. 1999, 181, 243 and
methylalumoxane (MAO) and the metallocene precursor
references therein. (j) Chien, J . C. W. Top. Catal. 1999, 7, 23 and
references therein.
onto a silica support.2
(3) (a) Soga, K.; Arai, T.; Hoang, B. T.; Uozumi, T. Macromol. Rapid
In search of alternatives for MAO, weakly coordinat-
Commun. 1995, 16, 905. (b) J in, J .; Uozumi, T.; Soga, K. Macromol.
Rapid Commun. 1995, 16, 317. (c) Nishida, H.; Uozumi, T.; Soga, K.
Macromol. Rapid Commun. 1995, 16, 821. (d) Iiskola, E. I.; Timonen,
S.; Pakkanen, T. T.; H a¨ rkki, O.; Lehmus, P.; Sepp a¨ l a¨ , J . V. Macro-
molecules 1997, 30, 2853. (e) Lee, D.-H.; Yoon, K.-B. Macromol. Rapid
Commun. 1997, 18, 427. (f) Arai, T.; Ban, H. T.; Uozumi, T.; Soga, K.
Macromol. Chem. Phys. 1997, 198, 229. (g) Barrett, A. G. M.; Miguel,
Y. R. Chem. Commun. 1998, 2079. (h) Arai, T.; Ban, H. T.; Uozumi,
T.; Soga, K. J . Polym. Sci., A: Polym. Chem. 1998, 36, 421. (i) Galan-
Fereres, M.; Koch, T.; Hey-Hawkins, E.; Eisen, M. S. J . Organomet.
Chem. 1999, 580, 145. (j) Alt, H. G.; Schertl, P.; K o¨ ppl, A. J . Organomet.
Chem. 1999, 568, 263. (k) Alt, H. G. J . Chem. Soc., Dalton Trans. 1999,
1703. (l) Chan, M. C. W.; Chin Chew, K.; Dalby, C. I.; Gibson, V. C.;
Kohlmann, A.; Little, I. R.; Reed, W. Chem. Commun. 1998, 1673. (m)
Antberg, M.; L u¨ ker, H.; B o¨ hm, L. U.S. Pat. Appl. 5,202,398, 1993. (n)
Vega, W. M.; C a˜ nas, P. L.; Lafuente, A. M.-E.; Llinas, G. H.; Royo, J .
S.; Llatas, L. M. U.S. Pat. Appl. 5,824,620, 1998.
+
-
+
ing boron-based cocatalysts such as X {B(C6F5)4} (X
*
To whom correspondence should be addressed. E-mail: R.
Duchateau@tue.nl. Fax: +31 40 2455054.
†
Eindhoven University of Technology.
University of Ottawa.
‡
(1) For example see: (a) Sinn, H.; Kaminsky, W. Adv. Organomet.
Chem. 1980, 18, 99. (b) Tait, P. T. Comput. Polym. Sci. 1989, 4, 1. (c)
Herrmann, H. F.; B o¨ hm, L. L. Polym. Commun. 1991, 32, 58. (d) Xie,
T.; McAuley, K. B.; Hsu, J . C. C.; Bacon, D. W. Ind. Eng. Chem. Res.
1
1
994, 33, 449. (e) Marsden, C. E. Plast., Rubber Compos. Process. Appl.
994, 21, 193. (f) Hungenberg, K. D.; Kerth, J .; Langhauser, F.;
Marczinke, B.; Schlund, R. In Ziegler Catalysts; Fink, G., M u¨ lhaupt,
R., Brintzinger, H. H., Eds.; Springer-Verlag: New York, 1995; Chapter
2
0.
1
0.1021/om990855o CCC: $19.00 © 2000 American Chemical Society
Publication on Web 02/04/2000

8
10 Organometallics, Vol. 19, No. 5, 2000
Duchateau et al.
Ch a r t 1. Silica -Su p p or ted Bor a te Coca ta lysts a n d
Th eir Silsesqu ioxa n e Ba sed An a logu es
silica-grafted borato species as olefin polymerization
cocatalysts. As homogeneous model systems are much
easier to characterize than those of amorphous silica,
they provide a powerful tool to study the interaction of
substrates, such as boranes, with silanol sites. We used
silsesquioxanes, soluble auxiliaries that have proven to
be realistic models for a variety of silica surface silanol
9
,10
sites.
Here we describe the synthesis of several silsesqui-
oxane-borato complexes. The stability of the B-O bond
in these complexes is studied in detail, as well as the
applicability of the siloxy-borato systems as cocatalysts
in olefin polymerization reactions.
Resu lts a n d Discu ssion
Chart 1 shows two possible silica surface sites con-
taining a grafted boron cocatalyst and their homoge-
neous analogues that have been mimicked using the
silsesquioxanes (c-C5H9)7Si8O12(OH) and (c-C5H9)7Si7O9-
(
OH)3 (c-C5H9 ) cyclopentyl), respectively.
As is indicated by the broad signals in the 19F NMR
toluene-d8), in the absence of a proton acceptor, the
(
silsesquioxanes [(c-C5H9)7Si8O12(OH)] and [(c-C5H9)7-
Si7O9(OH)3] form fluxional, weakly bonded adducts with
the borane B(C6F5)3 (Scheme 1). In the presence of
proton acceptors such as the strong Brønsted basic
1
1
amines PhNMe2 and NEt3, equimolar amounts of the
silsesquioxanes and B(C6F5)3 react to yield the stable
silsesquioxane-borato ammonium salts 1 and 2 (Chart
1
and Scheme 1). Interestingly, the more nucleophilic
Lewis base pyridine yield the borane base adduct
C6F5)3B‚Py (3) instead (Scheme 1). This clearly indi-
the support. Interestingly, effective olefin polymeriza-
tion cocatalysts formed by simply grafting B(C6F5)3 onto
silica in the presence of an amine have been claimed
(
cates that high Brønsted basicity and low nucleophilicity
of the amine are required to form the desired silsesqui-
oxane-borato complexes (Scheme 1).
5
d,7
+
-
(
Chart 1).
Comparable X {(C6F5)3BOR} (R ) alkyl;
X ) H, Et3NH) complexes have been used as cocatalysts
in olefin polymerization as well. To our knowledge,
8
+
Ammonium silsesquioxane borates X {[(c-C5H9)7-
however, no serious investigations on the stability and
reactivity of the B-O bond of siloxy-borato species
formed upon grafting onto silica5 have been reported.
As part of our interest in developing useful im-
-
+
+
+
Si8O13]B(C6F5)3} (1a , X ) PhN(H)Me2 ; 1b, X ) Et3-
NH ) are very soluble in toluene and even slightly
soluble in hexane. In contrast, the silsesquioxane bis-
+
d,7
+
(silanol) borato complexes X {[(c-C5H9)7Si7(OH)2O10]B-
9
mobilization strategies, we tried to get an insight into
-
+
+
+
+
(
C6F5)3} (2a , X ) PhN(H)Me2 ; 2b, X ) Et3NH ) are
the stability of the B-O bond and the suitability of
only moderately soluble in toluene and insoluble in
1
3
29
hexane. The C and Si NMR spectra of 1a and 1b
are in agreement with a C3-symmetric structure in
solution. With five methine and silicon resonances in a
(4) (a) Turner, H. W. Eur. Pat. Appl. 277004, 1988. (b) Hlatky, G.
G.; Upton, D. J .; Turner, H. W. PCT Int. Appl. 91/09882, 1991. (c)
Ewen, J . A.; Elder, M. J . Eur. Pat. Appl. 427697, 1991. (d) Campbell,
R. E. Eur. Pat. Appl. 421659, 1991. (e) Yang, X.; Stern, C. L.; Marks,
T. J . J . Am. Chem. Soc. 1991, 113, 3623. (f) Chien, J . C. W.; Tsai, W.-
M.; Rausch, M. D. J . Am. Chem. Soc. 1991, 113, 8570. (g) Yang, X.;
Stern, C. L.; Marks, T. J . Organometallics 1991, 10, 840.
1
3
29
1
:1:1:2:2 ratio, the C and Si spectra of 2a and 2b
1
3
support the expected C2v symmetric structure. The C,
19
29
F, and Si NMR resonances for the silsesquioxane-
(5) (a) Chen, Y.-X.; Rausch, M. D.; Chien, J . C. W. J . Polym. Sci., A:
Polym. Chem. 1995, 33, 2093. (b) Hlatky, G. G.; Upton, D. J .
Macromolecules 1996, 29, 8019. (c) Roscoe, S. B.; Fr e´ chet, J . M. J .;
Walzer, J . F.; Dias, A. J . Science 1998, 280, 270. (d) Bochmann, M.;
Pindado, G. J .; Lancaster, S. J . J . Mol. Catal., A: Chem. 1999, 146,
borato anion of 1a are significantly shifted with respect
to those of 1b. The NH resonance in the H NMR of 1a
is found at 9.40 ppm, which is typical for a hydrogen-
bonded NH group. The high-field shift of the NH
resonance of 1b to 4.25 ppm suggests an even stronger
1
1
79.
(6) For example see: (a) Turner, H. W. U.S. Pat. Appl. 5,427,991,
1
995. (b) Ono, M.; Hinokuma, S.; Miyake, S.; Inazawa, S. Eur. Pat.
Appl. 710,663, 1996. (c) J acobsen, G. B.; Wijkens, P.; J astrzebski, J .;
van Koten, G. PCT Int. Appl. 96/28480, 1996. (d) Kaneko, T.; Sato, M.
Eur. Pat. Appl. 727,433, 1996. (e) Hinokuma, S.; Miyake, S.; Ono, M.;
Inazawa, S. Eur. Pat. Appl. 775,707, 1997. (f) Carnahan, E. M.; Carney,
M. J .; Neithamer, D. R.; Nickias, P. N.; Shih, K.-Y.; Spencer, L. PCT
Int. Appl. 97/19959, 1997. (g) Kaneko, T.; Sato, M. U. S. Pat. Appl.
(9) For example see: (a) Duchateau, R.; Abbenhuis, H. C. L.; van
Santen, R. A.; Meetsma, A.; Thiele, S. K.-H.; van Tol, M. F. H.
Organometallics 1998, 17, 5663. (b) Duchateau, R.; Cremer, U.;
Harmsen, R. J .; Mohamud, S.; Abbenhuis, H. C. L.; van Santen, R. A.;
Meetsma, A.; Thiele, S. K.-H.; van Tol, M. F. H.; Kranenburg, M.
Organometallics 1999, 18, 5447.
(10) For example see: (a) Feher, F. J .; Newman, D. A.; Walzer, J .
F. J . Am. Chem. Soc. 1989, 111, 1741. (b) Feher, F. J .; Budzichowski,
T. A. Polyhedron 1995, 14, 3239. (c) Feher, F. J .; Blanski, R. L. J . Chem.
Soc., Chem. Commun. 1990, 1614. (d) Feher, F. J .; Walzer, J . F.;
Blanski, R. L. J . Am. Chem. Soc. 1991, 113, 3618. (e) Liu, J . C. Chem.
Commun. 1996, 212.
5
,807,938, 1998.
7) (a) Ward, D. G.; Carnahan, E. M. PCT Int. Appl. 96/23005, 1996.
b) Walzer, J . F.. J r. U.S. Pat. Appl. 5,643,847, 1997.
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b) Siedle, A. R.; Lamanna, W. M.; Newark, R. A.; Stevens, J .;
(
(
(
(
Richardson, D. E.; Ryan, M. Makromol. Chem., Macromol. Symp. 1993,
6, 215. (c) Siedle, A. R.; Newmark, R. A.; Lamanna, W. M. Organo-
metallics 1993, 12, 1491.
6
(11) Liu, W.-Z.; Bordwell, F. G. J . Org. Chem. 1996, 61, 4778.

Cocatalysts Modeled by Silsesquioxane-Borato Complexes
Organometallics, Vol. 19, No. 5, 2000 811
Sch em e 1. Dep r oton a tion ver su s Ad d u ct F or m a tion Dep en d in g on th e P r oton -Accep tin g Ca p a bility of th e
Ba se
interaction of the ammonium cation with the silsesqui-
1
2
oxane-borato anion of 1b than in 1a . For 2a and 2b,
the differences in the 13C, F, and Si NMR are much
smaller, indicating that in the latter type of silsesqui-
oxane-borates strong cation-anion interaction is less
apparent.13 Possible intramolecular hydrogen bonding
in the anions of 2a and 2b may also explain the smaller
shift differences observed as compared to those in the
anions of 1a and 1b.14
19
29
Definite proof for an interaction between the am-
monium cation and the silsesquioxane-borato anion in
1
a was provided by a single-crystal X-ray analysis
(
Figure 1). The ammonium cation is clearly hydrogen-
bonded to the silsesquioxane-borato anion (N-O1 )
.874(6) Å). As a result of the hydrogen bridge, the
oxygen (O1) adopts a trigonal-planar rather than a
2
1
5
linear geometry. Due to the anionic charge at boron
in 1a , the B-O1 bond distance of 1.505(5) Å in 1a is
significantly longer than the B-O distances in the
neutral boron-containing silsesquioxane {[(c-C6H11)7-
Si7O12]B}2, ranging from 1.325(23) to 1.406(18) Å. The
B-O bond distance in 1a is within the wide range found
for transition-metal borato complexes LnM-O-B(C6F5)3
-
F igu r e 1. ORTEP drawing of {[(c-C H ) Si O ]B(C F ) } -
5
9 7
8
13
6
5 3
+
{PhN(H)Me2} (1a ). Ellipsoids are scaled to enclose 50%
of the electron density. Hydrogen atoms and cyclopentyl
groups are omitted for clarity. Selected bond distances
1
6
(
(
Å): Si1-O1, 1.615(2); Si1-O2, 1.614(2); Si1-O3, 1.619-
2); Si1-O4, 1.604(2); O1-B, 1.505(5); O1-N, 2.874(6);
B-C14, 1.669(5); B-C20, 1.657(5); B-C26, 1.656(5). Angles
2
15a
2
(
(
LnM ) Ti[η -(OCMe)2CH]2, 1.496(3) Å; LnM ) V[η -
(
deg): B-O1-Si1, 125.0(2); B-O1-N, 126.1(2); Si1-O1-
1
5a
2
OCMe)2CH]2, 1.527(2) Å; LnM ) Mo(dO)[η -(OCMe)2-
N, 107.2(2); O1-Si1-O2, 106.03(13); O1-Si1-O3, 109.44-
1
5a
15b
CH]2, 1.521(3) Å; LnM ) (C5H4Me)2Mo, 1.484(2) Å;
(
13); O1-Si1-O4, 112.59(13); O1-B-C14, 110.4(3); O1-
8
b
LnM ) (C5Me5)2Zr, 1.460(6) Å ) and [LnM][(C6F5)3BOH]
B-C20, 105.6(3); O1-B-C26, 111.4(3); C6-N-C7, 113.0(3);
C6-N-C8, 110.9(3); C7-N-C8, 110.3(3).
(
LnM ) (C5Me5)2Ta(OH)Me, 1.490(10) Å;15c LnM ) (4,4′-
1
5d
di-tert-butyl-2,2′-bipyridine)PtMe, 1.526(3) Å ). The
B-C bonds in 1a are normal for borates1
5,17
significantly elongated (by approximately 0.1 Å) com-
pared to the corresponding B-C bonds in base-free
and are
1
8
boranes.
(
12) The concentrations of NMR tube solutions of 1a ,b and 2a ,b were
comparable, 65((10) mM.
13) IR spectra of 1a ,b and 2a ,b did not provide additional informa-
tion about possible hydrogen bonding in these complexes.
14) Feher, F. J .; Phillips, S. H.; Ziller, J . W. Chem. Commun. 1997,
29.
15) (a) Galsworthy, J . R.; Green, M. L. H.; M u¨ ller, M.; Prout, K. J .
The presence of the hydrogen bridge in 1a might
suggest that the B-O bond is quite labile and that
formation of the silsesquioxane-borate is reversible. To
verify this possibility, the stability of the B-O bond in
silsesquioxane-borato complexes 1 and 2 was deter-
mined.
(
(
8
(
Chem. Soc., Dalton Trans. 1997, 1309. (b) Galsworthy, J . R.; Green,
J . C.; Green, M. L. H.; M u¨ ller, M. J . Chem. Soc., Dalton Trans. 1998,
1
1
5. (c) Schaefer, W. P.; Quan, R. W.; Bercaw, J . E. Acta Crystallogr.
993, C49, 878. (d) Hill, G. S.; Manojlovic-Muir, L.; Muir, K. W.;
The Lewis acidic B(C6F5)3 is known to form stable
nitrile and amine adducts (C6F5)3B‚L (L ) MeCtN,
Puddephatt, R. J . Organometallics 1997, 16, 525.
16) Feher, F. J .; Budzichowski, T. A.; Ziller, J . W. Inorg. Chem.
992, 31, 5100.
17) For example see: (a) Bochmann, M.; Lancaster, S. J . Organo-
(
1
(18) For example see: (a) Duchateau, R.; Lancaster, S. J .; Thornton-
Pett, M.; Bochmann, M. Organometallics 1997, 16, 4995. (b) Williams,
V. C.; Piers, W. E.; Clegg, W.; Elsegood, M. R. J .; Collins, S.; Marder,
T. B. J . Am. Chem. Soc. 1999, 121, 3244.
(
metallics 1994, 13, 2235. (b) Yang, X.; Stern, C. L.; Marks, T. J . J .
Am. Chem. Soc. 1994, 116, 10015.

8
12 Organometallics, Vol. 19, No. 5, 2000
Duchateau et al.
Py).19 Hence, when 1 and 2 are in equilibrium with free
silsesquioxane and B(C6F5)3, in the presence of excess
of Lewis base, the equilibrium is expected to be pushed
to the formation of the borane Lewis base adduct. None
of the silsesquioxane-borates (1 and 2) react with
MeCtN. However, treating a benzene-d6 solution of 1a
with pyridine gave a significant amount (∼30%) of the
borane-pyridine adduct (C6F5)3B‚NC5Η5 (3).20 Benzene-
d6 solutions of 2a treated with pyridine quantitatively
afforded 3, as the poorly soluble silsesquioxane (c-
C5H9)7Si7O9(OH)3 precipitated from the benzene solu-
tion, pushing the equilibrium to the formation of the
borane-Lewis base adducts 3. The triethylammonium
salts 1b and 2b clearly show less tendency to react with
Lewis bases, as only a small amount (∼7%) of the
1
19
pyridine adduct 3 was detected by H and F NMR
spectroscopy (benzene-d6).20 The difference in reactivity
toward pyridine of 1a , 2a compared to that of 1b, 2b
can be explained on the basis of the different pKa values
+
of the ammonium ions (C5H5NH , pKa ) 3.5; PhN(H)-
+
+
11
Me2 , pKa ) 2.5; Et3NH , pKa ) 9.0). This also agrees
with the observation that treating the dimethyla-
nilinium salts 1a and 2a with the stronger Brønsted
base NEt3 quantitatively afforded the corresponding
triethylammonium salts 1b and 2b.
-
NH}+
F igu r e 2. ORTEP drawing of {(C
6
F
5
)
3
BOH} {Et
3
(4b). Ellipsoids are scaled to enclose 50% of the electron
density. Selected bond distances (Å): B-O, 1.495(5); B-C6,
1
.652(6); B-C12, 1.662(6); B-C18, 1.665(6); O-N, 2.734(6).
Because of the hydrolyzable nature of the B-O bond,
siloxy-borato complexes 1 and 2 are moisture sensitive.
Treatment of 1 and 2 with equimolar amounts of water
quantitatively yielded the corresponding hydroxyl com-
Angles (deg): O-B-C6, 102.3(3); O-B-C12, 109.3(3);
O-B-C18, 112.3(3); B-O-N, 134.6(3).
alkyl) can react either as a Brønsted base or a nucleo-
phile. Furthermore, tetravalent group 4 metal ions are
strongly oxophilic. Therefore, the question arises whether
the B-O bond of siloxyborates is stable in the presence
of group 4 metal alkyl complexes. Comparable X {(C6F5)3-
BOR} (R ) alkyl; X ) H, Et3NH) complexes were
+
-
plexes {R3NH} {(C6F5)3BOH} (R3N ) PhNMe2 (4a ),
NEt3 (4b)). Similarly, alcoholysis of 1a and 2a with
i-PrOH quantitatively affords the corresponding alkoxy-
+
-
+
borate {PhN(H)Me2} {i-PrOB(C6F5)3} (5), which fits in
with the higher acidity of silsesquioxane silanols com-
pared to alcohols.21
-
reported to be stable toward such exchange and have
been used as cocatalysts in olefin polymerization.8
In preliminary polymerization experiments, Cp2Zr(CH2-
Ph)2 activated by 1a (Mw ) 566 000, Mw/Mn ) 2.3) and
Zr(CH2Ph)4 activated by 2a (Mw ) 17 000, Mw/Mn ) 2.4)
did indeed give single-site ethylene polymerization
catalysts.
NMR studies on a toluene-d8 solution of equimolar
amounts of Cp2Zr(CH2Ph)2 and 1a showed that at -25
°C a rapid reaction occurs, yielding the cationic {[(c-
C5H9)7Si8O13]ZrCp2} {PhCH2B(C6F5)3} (6) as the main
product (>90%) (Scheme 2). Hence, the initially formed
cationic alkyl complex is rapidly transformed into the
inactive cationic silsesquioxane complex 6. The reaction
of Cp2Zr(CH2Ph)2 with 1b is considerably slower. Warm-
ing to room temperature is required for the reaction to
proceed. This strongly suggests that the first step of the
reaction is protonolysis of one of the benzyl groups by
the ammonium cation, as protonolysis is more facile for
a,b,15c
Figure 2 shows the X-ray structure of 4b. With an
O-N distance of 2.734(6) Å the ammonium cation in
4
b is clearly hydrogen-bonded to the borato oxygen,
which corresponds well with the hydrogen bridge found
in 1a . The B-O and B-C bond distances and O-B-C
angles in 4b are virtually identical with those in 1a and
1
5,22
compare well with those of other oxoborates.
Due
to differences in steric bulk compared to that of 1a , the
B-O-N bond angle in 4b (134.6(3)°) is widened com-
pared to the B-O-N angle in 1a (126.1(2)°).
+
-
From the results above it is clear that substitution of
the amine in ammonium siloxyborates 1 and 2 can be
accomplished by a stronger Brønsted base. On the other
hand, when these compounds are treated with a strong
nucleophile, formation of the borane-Lewis base adduct
is likely to occur. Depending on its Brønsted/Lewis base
character, the base shows a clear preference for either
+
the Brønsted acid H or the Lewis acid B(C6F5)3
+
+
PhN(H)Me2 than for the less acidic Et3NH . The
concurrent formation of {(C6F5)3BCH2Ph} {Et3NH}
and [(c-C5H9)7Si8O13]Zr(CH2Ph)Cp2 (7) indicates that
direct exchange between Cp2Zr(CH2Ph)2 and 1b is also
possible when protolysis is hampered.
(Scheme 1). The alkyl substituent in early-transition-
-
+
metal complexes such as Cp2MR2 (M ) Ti, Zr, Hf; R )
(
19) (a) J acobsen, H.; Berke, H.; D o¨ ring, S.; Kehr, G.; Erker, G.;
Fr o¨ hlich, R.; Meyer, O. Organometallics 1999, 18, 1724. (b) Massey,
A. G.; Park, A. J . J . Organomet. Chem. 1964, 2, 245. (c) Massey, A. G.;
Park, A. J .; Stone, F. G. A. Proc. Chem. Soc. 1963, 521, 212.
23
1
The H NMR spectrum of 6 shows the characteristic
(20) Long reaction time (1 week) did not lead to an increase in the
broad BCH2Ph resonance at 3.60 ppm. With a ∆δ(Fm-
Fp) value of 2.89 for the [PhCH2B(C6F5)3] group, limited
concentration of 3, indicating that the equilibrium is rapidly estab-
lished.
-
(
21) pK
c-C Si
22) Without referring to an X-ray structure analysis, Siedle et al.
a
values determined in THF: (c-C
5
9
)
7
Si
7
O
9
b(OH)
3 a
, pK ) 7.6;
9
+
Ph}- crystallized from the toluene-d
/n, a ) 13.119(1) Å, b ) 14.090-
(
5
H
9
)
7
8
O
12(OH), pK ) 8.9; PhOH, pK
a
(23) {Et
solution: C31
(1) Å, c ) 17.099(2) Å, â ) 109.645(2)°, V ) 2976.8(5) Å , Z ) 4, R )
0.0482, R ) 0.1167.
3
NH} {(C
H
6
F
5
)
3
BCH
2
8
(
23BF15N, monoclinic, P2
1
-
3
6 5 3
reported a B-O bond distance of 1.487(3) Å for {(C H ) BOH} {N(H)-
+
8c
Et
3
} .
w

Cocatalysts Modeled by Silsesquioxane-Borato Complexes
Sch em e 2. Activa tion a n d P oison in g of Cp
Organometallics, Vol. 19, No. 5, 2000 813
Zr (CH P h ) by 1a
2
2
2
anion-cation interaction is present in 6.24 Complex 6
is stable at -25 °C, but around room temperature it is
clearly in equilibrium with the neutral 7 and B(C6F5).
Since both 6 and 7 are inactive species, only unreacted
Cp2Zr(CH2Ph)2 activated by the released B(C6F5)3 can
be held responsible for the observed catalytic activity
in ethylene polymerization (Scheme 2). Indeed, when a
polymerization experiment was carried out with Cp2-
Zr(CH2Ph)2 plus a slight excess of 1a , no polyethylene
was formed. However, as soon as additional Cp2Zr(CH2-
Ph)2 was added, rapid polymerization occurred. As a
control experiment, ethylene polymerization was carried
out with Cp2Zr(CH2Ph)2 as catalyst precursor activated
with B(C6F5)3 in the presence of PhNMe2. As expected,
a considerably larger exotherm was observed than when
reported to be the active ethylene polymerization cata-
lyst formed upon treatment of {[(c-C5H9)7Si7O12]ZrCH2-
9
a
Ph}2 with B(C6F5)3. Indeed, the low-molecular-weight
polyethylene formed by the Zr(CH2Ph)4 + 2a system (25
°C, Mw ) 17 000) resembles that of {[(c-C5H9)7Si7O12]2-
+
-
9a
Zr2CH2Ph} {PhCH2B(C6F5)3} (80 °C, Mw ) 7000) (cf.
+
-
25
{Zr(CH2Ph)3} {PhCH2B(C6F5)3} , Mw ) 500 000).
Variable-temperature NMR studies on toluene-d8
solutions of equimolar amounts of Cp Zr(CH Ph) and
2
2
2
+
-
{PhN(H)Me } {(C F ) BOR} (R ) H (4a ), i-Pr (5)) also
showed the formation of considerable amounts of B(C F )
2
6
5 3
6
5 3
as one of the side products. Like the silsesquioxane-
borates, these alkoxy- and hydroxyborates only show
catalytic activity in the presence of an excess of Cp Zr-
2
(CH Ph) .
2
2
1
a was used, since only a fraction of 1a is transformed
into the actual cocatalyst B(C6F5)3. This is in agreement
with the difference in observed activity between Cp2-
Con clu sion s
6
-1
Zr(CH2Ph)2 + 1a (0.4 × 10 g of PE ((mol of [Zr]) h)
)
The silsesquioxane-borates are useful soluble models
that can provide significant information about reactions
taking place at silica surfaces. Although stable in apolar
solvents, the silsesquioxane-borato species reported in
this study show a limited stability toward both Brønsted
and Lewis bases. Ammonium ions can easily be ex-
changed, and with strong nucleophiles, splitting of the
B-O bond is likely to occur. B-O bond breaking by
hydrolysis or alcoholysis is also facile, emphasizing that
the silsesquioxane is more acidic than alcohols and
water and therefore less able to stabilize the high Lewis
acidity of B(C6F5)3. The silsesquioxane-borates are also
unstable toward zirconium alkyl species. Although
protonolysis of the benzyl group by the ammonium
6
and Cp2Zr(CH2Ph)2 + B(C6F5)3/PhNMe2 (1.6 × 10 g of
-
1
PE ((mol of [Zr]) h) ) and may explain the lower
molecular weight and broader molecular weight distri-
bution of the polymer of the latter system (Mw )
1
77 500, Mw/Mn ) 4.5).
Not surprisingly, the B-O bond in the silsesquiox-
ane-borate 2a is also unstable to zirconium alkyls. A
1
19
variable-temperature (-30 to 40 °C) H and F NMR
study on a toluene-d8 solution containing equimolar
amounts of Zr(CH2Ph)4 and 2a showed the formation
+
of B(C6F5)3 and {[(c-C5H9)7Si7O12]2Zr2CH2Ph} {PhCH2B-
-
9a
(
C6F5)3} in a 1:1 ratio. The latter complex has been
(24) (a) Pellecchia, C.; Immirzi, A.; Grassi, A.; Zambelli, A. Orga-
nometallics 1993, 12, 4473. (b) Horton, A. D.; de With, J .; van der
Linden, A. J .; van der Weg, H. Organometallics 1996, 15, 2672.
(25) Bochmann, M.; Lancaster, S. J . Organometallics 1993, 12, 633.

8
14 Organometallics, Vol. 19, No. 5, 2000
Duchateau et al.
cation seems to be the first step for the reaction, the
thus formed cationic alkyl complex is rapidly trans-
formed into the inactive cationic silsesquioxane complex
1b (0.75 g, 0.49 mmol, 20%). Cooling of the mother liquor to
-
30 °C yielded a second crop of 1b (0.69 g, 0.45 mmol, 18%).
1
H NMR (benzene-d
6
, δ): 4.25 (s-br, 1H, HNEt
3
), 1.86 (q, 6H,
CH ), 1.70
2 5 9 2 5 9
m, 28H, CH C H ), 1.48 (m, 14H, CH C H ), 1.29 (t, 9H, HN-
3
HN(CH
(
(
2
3
)
3
, J H-H ) 4 Hz), 1.82 (m, 14H, CH C H
2 5 9
6
. Whereas the facile B-O bond splitting makes the
silsesquioxane-borato systems unsuitable as cocata-
lysts, subsequent B-C bond breaking and formation of
B(C6F5)3 explains the fact that ethylene poly-
merization activity is still observed. On the basis of
these results it is likely that the B-O bond in silica-
grafted borates is also labile. Hence, under influence of
transition-metal alkyls, silica-grafted borates are as-
sumed to be transformed into physisorbed borane, which
can be considered as being the actual cocatalyst.
CH
2
CH
3
)
5
3
, 3J H-H ) 4 Hz), 1.00 (m, 6H, CH C
5
H
9
), 0.72 (m,
1
1
J
H, CH C
H
9
). 13C{ H} NMR (benzene-d
6
6 5
, δ): 148.67 (d, C F ,
1
1
C-F ) 230 Hz), 138.77 (d, C
6
F
5
, J C-F ) 246 Hz), 137.06 (d,
1
C
6
F
5
2 3 3
, J C-F ) 233 Hz), 47.24 (s, HN(CH CH ) ), 28.00, 27.64,
27.52 (s, CH C H ), 23.40, 22.99 (s, CH C H , 3:4 ratio), 8.35
2
5
9
5
9
1
9
(s, HN(CH
2
CH
3
)
3
). F NMR (benzene-d
6
, δ): -56.55 (d, o-C
, J F-F ) 10 Hz), -89.83 (s,
, δ): -66.16, -66.39, -110.15
: C, 46.29; H,
.20; N, 0.92. found: C, 45.88; H, 5.32; N, 0.92.
P h N(H)Me Si (OH) 10]B(C
}+{[(c-C
mixture of B(C (1.42 g, 2.77 mmol) and (c-C
OH) (2.43 g, 2.78 mmol) in toluene (25 mL) was treated with
PhNMe (0.36 mL, 2.84 mmol) at room temperature. The
6 5
F ,
3
3
J
6 5
F-F ) 20 Hz), -86.30 (t, p-C F
2
9
6 5 6
m-C F ). Si NMR (benzene-d
(4:3:1 ratio). Anal. Calcd for C59H79BF15NO13Si
8
5
{
2
5
H
9
)
7
7
2
O
6
F
5
)
5
3
}- (2a ). A
Si
Exp er im en ta l Section
6
F
5
)
3
H
9
)
7
7 9
O -
(
3
Gen er a l Com m en ts. All manipulations were performed
under an argon atmosphere using glovebox (Braun MB-150
GI) and Schlenk techniques. Solvents were distilled from Na
2
mixture was heated to reflux until a clear solution was formed.
The volatiles were evaporated, and the crude product was
thoroughly dried. Crystallization of the product from a hot
toluene-hexane (1:1, 40 mL) mixture yielded 2a as colorless
(
toluene), K (THF), Na/K alloy (ether, hexanes), or CaH
Cl
Na/K alloy (benzene-d
CDCl , CD Cl , C
2
(CH
2
-
2
) and stored under argon. NMR solvents were dried over
6
) or 4 Å molecular sieves (toluene-d
Br). NMR spectra were recorded on Varian
8
,
crystals (2.48 g, 1.64 mmol, 59%). The crystals gradually lost
3
2
2
6
D
5
1
hexane from the lattice. H NMR (toluene-d
1
8
, δ): 8.75 (s-br,
), 6.77 (m, 2H,
C H N(H)Me ), 2.42 (s, 6H, PhN(H)(CH ) ), 1.81 (m, 14H, CH
GEMINI 300 and Varian 400 spectrometers. Chemical shifts
are reported in ppm and referenced to residual solvent
2 6 5 2
H, PhN(H)Me ), 6.91 (m, 3H, C H N(H)Me
1
13
29
resonances ( H, C NMR) or external standards ( Si, SiMe
4
6
5
2
3
2
2
1
9
5 9 2 5 9 2 5 9
C H ), 1.67 (m, 28H, CH C H ), 1.54 (m, 14H, CH C H ), 1.09
at 0 ppm; F, CF
3
CO
2
H at 0 ppm). Elemental analyses were
1
3
1
(
(
m, 4H, CH C
toluene-d , δ): 149.2 (d, C
N(H)Me ), 139.9 (d, p-C
, J C-F ) 236 Hz), 131.48 (s, m-C
N(H)Me ), 120.01 (s, o-C N(H)Me
H)(CH ), 29.82, 28.96, 28.80, 28.69, 28.53, 28.44, 28.35,
5
H
9
), 0.94 (m, 3H, CH C
5
H
9
). C{ H} NMR
carried out at the Analytical Department of the University of
Groningen (Groningen, The Netherlands). The molecular
weights and molecular-weight distributions were measured at
1
8
6 5
F , J C-F ) 237), 142.2 (s, ipso-
1
C
C
p-C
6
6
H
5
2
6
F
5
, J C-F ) 224 Hz), 137.69 (d,
N(H)Me ), 131.35 (s,
), 46.59 (s, PhN-
1
F
5
6
H
5
2
1
35 °C by gel-permeation chromatography (GPC; GPC210,
Polymer Labs) at the University of Groningen, using 1,2,4-
trichlorobenzene as solvent. Silsesquioxanes (c-C Si
were prepared by following
6
H
5
2
6
H
5
2
(
3 2
)
5
H
9
)
7
8 12
O -
9
10
5 9
28.32, 28.28, 28.21, 28.16 (s, CH2 C H ), 25.27, 24.08, 23.63,
(OH) and (c-C
5
H
9
)
7
Si
7
O
9
(OH)
3
2
3.58, 23.49 (s, CH C
8
5
H
5
9
, 1:2:1:1:2 ratio). 19F NMR (toluene-
literature procedures.
3
+
}- (1a ). Solid (c-
d , δ): -55.30 (d, o-C F , J
) 21 Hz), -84.79 (t, p-C F ,
{P h N(H)Me
2
} {[(c-C
5
H
9
)
7
Si
8
O
13]B(C
6
F
5
)
3
6
F-F
6
5
3
3 29
J
F-F ) 21 Hz), -88.90 (t, m-C
toluene-d , δ): -56.07, -62.02, -64.28, -65.07, -67.25 (2:1:
:1:2 ratio). Anal. Calcd for C61 (C
9.54; H, 5.46; N, 0.90. Found: C, 49.53; H, 5.49; N, 0.95.
{N(H)Et Si (OH) 10]B(C
}+{[(c-C }- (2b). NEt
(0.45 mL, 3.25 mmol) was added to a suspension of B(C
(1.42 g, 2.77 mmol) and (c-C Si (OH)
6 5
F , J F-F ) 20 Hz). Si NMR
C
5
H
9
)
7
Si
8
O
12(OH) (2.42 g, 2.64 mmol) was added to a solution
(
1
4
8
of B(C F ) (1.35 g, 2.64 mmol) in toluene (25 mL). The mixture
6 5 3
H
77BF15NO12Si
7
6 14
H )0.5: C,
was stirred and warmed until a clear solution was obtained.
PhNMe (0.35 mL, 2.76 mmol) was then added and the
2
resultant solution warmed to reflux. The volatiles were
evaporated, leaving crude 1a as a white foam. Crystallization
from a 1:5 toluene-hexane mixture (30 mL) yielded 1 as
colorless crystals (1.80 g, 1.16 mmol, 44%). After the mother
liquor was evaporated to dryness, the remaining solid was
dissolved in hot hexane (20 mL). Crystallization at -30 °C gave
3
5
H
9
)
7
7
2
O
6
F
5
)
3
3
3
6
5
F )
5
H
9
)
7
7
O
9
3
(2.43 g, 2.65 mmol)
in toluene (25 mL). The mixture was warmed until a clear
solution was formed. Then the solvent was evaporated and the
crude product suspended in hot hexane (30 mL). Toluene (20
mL) was added until a clear solution was obtained. Slow
cooling of the hot solution to room temperature afforded 2b
a second crop of colorless crystals of 1a (0.8 g, 0.52 mmol, 19%).
1
H NMR (benzene-d
6
, δ): 9.40 (s-br, 1H, PhN(H)Me
), 2.36 (s, 6H, PhN(H)(CH ), 1.80 (m, 14H,
), 1.59 (m, 28H, CH ), 1.46 (m, 14H, CH ),
), 0.94 (m, 3H, CH C ). C{ H} NMR
, J C-F ) 231 Hz), 141.15 (s,
), 139.49 (d, C
, 1J C-F ) 237 Hz), 137.00
, 1J C-F ) 235 Hz), 130.31 (s, p-C
N(H)Me ), 130.12
N(H)Me ), 119.53 (s, o-C N(H)Me ), 46.93 (s, PhN-
), 28.03, 27.87, 27.80, 27.62, 27.53 (s, CH ),
, 1:3:3 ratio). F NMR (benzene-
, J F-F ) 23 Hz), -83.53 (t, p-C
2
), 6.75 (m,
5
CH
1
(
H, C
6
H
5
N(H)Me
2
3
)
2
as a colorless microcrystalline material (2.55 g, 1.71 mmol,
1
C
5
H
9
2
C
5
H
9
2
C
5
H
9
65%). H NMR (toluene-d
8
, δ): 8.26 (s-br, 1H, N(H)Et
3
), 6.85
, J H-H ) 7 Hz), 1.92
9
H ), 1.24 (m, 3H, CH
2
1
3
1
2
.08 (m, 4H, CH C
benzene-d , δ): 148.61 (d, C
N(H)Me
5
H
9
5
H
9
(s-br, 2H, OH), 2.40 (q, 6H, HN(CH
(m, 56 H, CH ), 1.38 (m, 4H, CH C
), 0.89 (t, 9H, HN(CH
(toluene-d , δ): 149.32 (d, C
, J C-F ) 247 Hz), 137.77 (d, C
(s, HN(CH CH ), 29.79, 29.00, 28.82, 28.69, 28.54, 28.44,
28.41, 28.33, 28.18 (s, CH ), 25.44, 24.17, 23.72, 23.67,
23.61 (s, CH C , 1:2:2:1:1 ratio), 8.76 (s, HN(CH
NMR (toluene-d
2
CH
3
)
3
1
F
5
2
C
5
H
9
5
6
6
2
13
1
ipso-C
6
H
5
2
6
F
5
C
5
H
9
2 3 3
CH ) , J H-H ) 7 Hz). C{ H} NMR
1
(d, C
(s, m-C
(H)(CH
6
F
5
6
H
5
2
8
6 5
F , J C-F ) 231 Hz), 139.74 (d,
1
1
H
5
2
6
H
5
2
C
6
F
5
6 5
F , J C-F ) 244 Hz), 46.85
6
)
2
2
C
5
H
9
2
3 3
)
3
1
9
2
d
2.68, 22.60, 22.54 (s, CH C
5
3
H
9
2 5 9
C H
19
, δ): -56.14 (d, o-C
6
F
5
6
F
5
,
5
H
9
2
CH
3
)
3
).
F
6
3
3
29
3
J
F-F ) 21 Hz), -88.28 (t, m-C
benzene-d , δ): -65.92, -65.98, -66.03, -104.30 (1:3:3:1
ratio). Anal. Calcd for C61 : C, 47.25; H, 4.88;
6
F
5
, J F-F ) 19 Hz). Si NMR
8
, δ): -55.30 (d, o-C
, J F-F ) 21 Hz), -89.07 (t, m-C
Si NMR (toluene-d , δ): -56.40, -61.80, -64.49, -65.08,
-67.33 (2:1:1:1:2 ratio). Anal. Calcd for C59 : C,
47.60; H, 5.48; N, 0.94. Found: C, 47.55; H, 5.54; N, 0.98.
(C B‚NC (3). (a) Pyridine (0.3 mL, 3.7 mmol) was
added to a toluene solution (10 mL) of B(C (0.95 g, 1.86
6 5
F , J F-F ) 21 Hz), -85.19
3
3
(
6
(t, p-C
6
F
5
6 5
F , J F-F ) 20 Hz).
2
9
H
75BF15NO13Si
8
8
N, 0.90. Found: C, 46.95; H, 4.75; N, 1.01.
H81BF15NO12Si
7
+
}- (1b). Solid (c-
{
N(H)Et
Si
25 mL) solution of B(C
was stirred and warmed until a clear solution was obtained.
NEt (0.40 mL, 2.88 mmol) was then added. The resultant
3
} {[(c-C
5
H
9
)
7
Si
8
O
13]B(C
6
F
5
)
3
C
(
5
H
9
)
7
8
O
12(OH) (2.24 g, 2.44 mmol) was added to a toluene
(1.25 g, 2.44 mmol). The mixture
6
F
5
)
3
5 5
H
6
F
5
)
3
6 5 3
F )
mmol) at room temperature. The solution was stirred for 1 h,
after which time the volatiles were evaporated, affording a
white solid. The crude product was washed with hexane (2 ×
3
solution was warmed to reflux and evaporated to dryness. The
crude product was dissolved in hot hexane (30 mL) and filtered.
Slow cooling to room temperature yielded colorless crystals of
2 2
5 mL) and recrystallized from CH Cl . Cooling to -30 °C
yielded 3 as large colorless crystals (0.45 g, 0.76 mmol, 41%).

Cocatalysts Modeled by Silsesquioxane-Borato Complexes
Concentration and cooling to -30 °C of the mother liquor
Organometallics, Vol. 19, No. 5, 2000 815
Ta ble 1. Cr ysta llogr a p h ic Da ta for th e X-r a y
Str u ctu r e Deter m in a tion of
1
yielded a second crop of 3 (0.28 g, 0.47 mmol, 25%). H NMR
3
{[(c-C H ) Si O ]B(C F ) }
-
{P h N(H)Me }
3
+
(1a ) a n d
(
6
benzene-d
6
, δ): 7.99 (d, 2H, pyridine o-CH, J H-H ) 5 Hz),
5
9
7
8
13
6
5
3
2
-
+
3
{(C F ) BOH} {Et NH} (4b)
.67 (t, 1H, pyridine p-CH, J H-H ) 8 Hz), 6.32 (t, 2H, pyridine
6
5
3
3
13
1
m-CH, J H-H ) 7 Hz). C{ H} NMR (benzene-d , δ): 148.09
6
1
a
4b
(
(
(
(
d, C
6
F
5
, 1J C-F ) 239 Hz), 146.18 (s, pyridine m-CH), 141.59
formula
fw
C61H75BF15NO13Si8 C24H16BF15NO
1
s, pyridine p-CH), 140.49 (d, C
d, C
benzene-d
6
F
5
, J C-F ) 240 Hz), 137.56
1550.75
631.19
1
19
6 5
F , J C-F ) 247 Hz), 124.87 (s, pyridine o-CH). F NMR
3
cryst syst
space group
a (Å)
monoclinic
P21/c
monoclinic
P21/n
6
, δ): -54.81 (d, o-C
, J F-F ) 22 Hz), -86.12 (t, m-C
Calcd for C23 BF15N: C, 46.74; H, 0.85; N, 2.37. Found: C,
6.29; H, 0.96; N, 2.14.
b) NMR tubes containing benzene-d
a were treated with pyridine (4 equiv). On the basis of
6 5
F , J F-F ) 21 Hz), -79.01 (t,
3
3
p-C
6
F
5
6
F
5
, J F-F ) 19 Hz). Anal.
17.050(3)
20.919(4)
20.046(4)
90.975(4)
7149(2)
11.891(2)
15.397(2)
14.230(2)
107.098(3)
2490.1(7)
4
H
5
b (Å)
c (Å)
4
â (deg)
(
6
solutions of 1a and
3
1
9
V (Å )
2
F
Z
4
NMR, at room temperature approximately 30% of 1a was
converted into 3. For the reaction of 2a with pyridine, 3 was
the only fluorine-containing product, as the silsesquioxane (c-
Dcalcd (g cm-3)
λ(Mo KR) (Å)
1.441
1.681
0.710 73
3216
0.710 73
1260
F(000)
C
5
H
{
9
)
7
Si
P h N(H)Me
mmol) and PhNMe
toluene (15 mL) solution of B(C
7
O
9
(OH)
3
quantitatively precipitated from solution.
µ (mm-1)
cryst size (mm)
T (K)
θ range (deg)
scan type
hkl
0.249
0.179
}+{(C
F
)
BOH} (4a ). H
-
O (0.10 mL, 5.6
0.2 × 0.2 × 0.1
0.2 × 0.2 × 0.2
2
6
5
3
2
238(2)
213(2)
2
(0.3 mL, 2.4 mmol) were added to a
(1.20 g, 2.34 mmol), and
1.83 < θ < 21.97
ω/2θ
h, -17 to +17;
k, 0-22; l, 0-21
56141
1.97 < θ < 28.64
ω/2θ
h, -15 to +14;
k, 0-18; l, 0-18
5659
6
5 3
F )
the resulting mixture was stirred for 2 h at room temperature.
The volatiles were removed under vacuum, leaving a white
microcrystalline solid. Recrystallization from CHCl
3
(10 mL)
no. of rflns total
at -30 °C yielded 4a (0.83 g, 1.28 mmol, 55%) as colorless
no. of data (I > 2σ(I)) 8714
no. of params refined 892
4300
379
1
crystals. H NMR (benzene-d
.81 (m, 3H, PhN(H)Me ), 6.51 (d, 2H, PhN(H)Me
Hz), 1.70 (s, 6H, PhN(H)Me
6
, δ): 7.42 (s-br, 1H, PhN(H)Me
2
),
3
R1 (I > 2σ(I))a
6
2
2
, J H-H ) 8
0.0426
0.1052
1.014
0.438, -0.440
0.0547
0.1186
1.031
0.476, -0.367
1
3
1
wR2 (I > 2σ(I))b
GOF (I > 2σ(I))
diff peak and hole
2
). C{ H} NMR (benzene-d
, J C-F ) 234 Hz), 141.45 (s, ipso-C ), 139.49
, J C-F ) 246 Hz),
), 119.42 (s, C ), 44.68 (s,
, δ): -58.88 (d, o-C
6
, δ):
1
1
48.35 (d, C
6
F
5
6 5
F
1
1
(d, C
6
F
5
, J C-F ) 238 Hz), 137.29 (d, C
30.08 (s, C ), 129.93 (s, C
). F NMR (benzene-d
6 5
F
-
3
(
e Å )
1
CH
6
F
5
6
F
5
6 5
F
1
9
3
a
The structure was refined in Fo2 using all data; the value of
3
6
6
F
5
, J F-F ) 17
3
3
Hz), -82.87 (t, p-C
22 Hz). Anal. Calcd for C26
N, 2.15. Found: C, 47.60; H, 2.04; N, 1.95.
6
F
5
, J F-F ) 20 Hz), 87.77 (t, m-C
6
F
5
, J F-F
R1 is given for comparison with older refinements based on Fo
with a typical threshold of Fo > 4σ(Fo). R1 ) ∑||Fo| - |Fo||/∑|Fo|.
)
H13BF15NO: C, 47.96; H, 2.01;
b
2
2
2
2
2
1/2
2
2
wR2 ) [∑[w(Fo - Fc ) ]/∑[w(Fo ) ]] , where w ) 1/[σ (Fo ) +
2
2
2
(
nP) ], P ) (Fo + 2Fc )/3, and n ) 0.06 for 1a and 0.03 for 4b.
+
-
{
Et
O (0.12 mL, 6.7 mmol) were added to a toluene solution (15
mL) of B(C (1.81 g, 3.53 mmol). The mixture was stirred
3 6 5 3 3
NH} {(C F ) BOH} (4b). NEt (1 mL, 7.2 mmol) and
H
2
NMR Tu be Rea ction of Cp Zr (CH P h ) w ith 1a : F or -
2
2
2
+
-
6
F
5
)
3
5 9 7 8 13 2 2 6 5 3
m a tion of {[(c-C H ) Si O ]Zr Cp } {P h CH B(C F ) } (6)
at room temperature for 3 h, upon which a white precipitate
was formed. After evaporation of the volatiles the crude white
5 9 7 8 13 2 8
a n d [(c-C H ) Si O ]Zr (CH P h )Cp 2 (7). A toluene-d solu-
tion (0.5 mL) of Cp Zr(CH Ph) (26 mg, 64 µmol) was added
2
2
2
product was recrystallized from CH
2
Cl
2
(10 mL). Cooling to
to an NMR tube containing a frozen toluene-d8 solution (0.5
-
30 °C afforded 4b as colorless crystals (1.61 g, 2.55 mmol,
mL) of 1a (100 mg, 64 µmol). The solution was defrosted at
1
1
19
7
6
1
2%). H NMR (CDCl
3
, δ): 11.04 (s-br, 1H, Et
3
NH), 2.91 (q,
BOH),
H-H ) 8 Hz). C{ H} NMR
, J C-F ) 243 Hz), 138.82 (d, C
-40 °C. H and F NMR measured at -25 °C (after 10 min)
3
+
H, HN(CH
.21 (t, 9H, HN(CH
, δ): 147.71 (d, C
2
CH
3
)
3
, J H-H ) 7 Hz), 2.47 (s-br, 1H, (C
6
1
F
5
)
3
showed the formation of {[(c-C H ) Si O ]ZrCp } {PhCH B-
5
9
7
8
13
2
2
3
13
-
1
2
CH
3
)
5
3
,
J
6 5 3
(C F ) } (6) in approximately 90% yield. H NMR (toluene-
1
(
CDCl
3
6
F
6
F
5
,
d , 25 °C, δ): 7.48-7.16 (m, 5H, C H ), 5.98 (s, 10H, C H ),
8
6
5
5
5
1
1
J
C-F ) 236 Hz), 136.60 (d, C
HN(CH CH , 8.20 (s, HN(CH
59.24 (d, m-C
1 Hz), -88.12 (t, o-C
17BF15NO: C, 45.67; H, 2.71; N, 2.22. Found: C, 45.43;
H, 2.79; N, 2.20.
P h N(H)Me
}+{i-P r OB(C
temperature, a toluene (20 mL) solution of B(C
.22 mmol) was treated with i-PrOH (0.4 mL) and PhNMe
0.5 mL). After 15 min at room temperature, hexane (20 mL)
6
F
5
, J C-F ) 209 Hz), 45.95 (s,
2 2 5 9
3.60 (s-br, 2H, BCH ), 2.10 (m, 14H, CH C H ), 1.90 (m, 28H,
)
3
2
CH
3
)
3
). 19F NMR (CDCl
3
, δ):
2 5 9 2 5 9 5 9
CH C H ), 1.74 (m, 14H, CH C H ), 1.39 (m, 7H, CH C H ).
2
3
3
3
19
3
-
2
6
F
5
, J F-F ) 21 Hz), -83.30 (t, p-C
6
F
5
, J F-F
)
F NMR (toluene-d , 25 °C, δ): -53.91 (d, o-C F , J
F-F
) 23
8
6
5
3
3
6
F
5
,
J
F-F ) 20 Hz). Anal. Calcd for
Hz), -86.90 (t, p-C F , J
6
5
F-F
) 21 Hz), -89.87 (m, m-C F ).
6
5
C
24
H
Warming of the solution to room temperature showed the
formation of significant amounts of [(c-C H ) Si O ]Zr(CH -
5
9
7
8
13
2
}-‚0.5C
H
CH
(5). At room
(1.66 g,
Ph)Cp
(7) and B(C
F
)
. On the basis of F NMR at room
19
{
2
6
F
5
)
3
6
5
3
2
6
5
3
F
5
)
3
temperature, the ratio {PhCH
2
B(C was found
6
F
5
)
3
}-:B(C
6 5 3
F )
6
3
(
2
to be 9:1. To prove the presence of 7, this complex was also
prepared independently.
was added. Crystallization at -30 °C yielded 5 as colorless
[(c-C
solution of Cp
-80 °C, and (c-C
added. The mixture was warmed to room temperature. At room
temperature, the solution slowly decolorized. The solvent was
evaporated, and the crude product was washed and suspended
in hexane (10 mL). The pale yellow solution was decanted,
5
H
9
)
7
Si
2
8
O
13]Zr (CH P h )Cp
Zr(CH Ph) (0.40 g, 0.98 mmol) was cooled to
8
Si O12(OH) (0.90 g, 0.98 mmol) was
2
2
(7). A toluene (50 mL)
needles (1.90 g, 2.57 mmol, 80%). Complex 5 contains 0.5 equiv
2
2
1
of toluene in the lattice. H NMR (benzene-d
6
, δ): 9.23 (s-br,
5
H
9
)
7
3
1
H, NH), 6.96 (m, 2H, m-C
6
H
5
), 6.82 (t, 1H, p-C
, J H-H ) 8 Hz), 3.982 (h, 1H, CHMe
H-H ) 6 Hz), 2.14 (s, 6H, PhN(H)(CH ), 0.65 (d, 6H, CH-
, J H-H ) 6 Hz). C NMR (benzene-d , δ): 148.50 (d,
, J C-F ) 246 Hz), 137.26
6
H
5
, J H-H ) 8
3
Hz), 6.69 (d, 2H, i-C
6
H
5
2
,
3
J
CH
3 2
)
3
13
(
3
)
2
1
6
1
1
C
6
F
5
, J C-F ) 246 Hz), 139.74 (d, C
6
F
5
leaving 7 as an off-white powder (0.85 g, 0.69 mmol, 70%). H
3
3
(d, C
6
F
5
, J C-F ) 250 Hz), 129.83 (s, C
N(H)Me ), 117.83 (s, C N(H)Me
4.08 (s, PhN(H)(CH ), 24.73 (s, CH(CH
, δ): -55.59 (d, o-C
6
H
5
N(H)Me
2
), 129.19 (s,
),
). F NMR (benzene-
, J F-F ) 21 Hz), -82.30 (d, p-C
F-F ) 21 Hz), -87.83 (m, m-C ). Anal. Calcd for C29
: C, 52.80; H, 3.14; N, 1.89. Found: C, 52.61;
NMR (benzene-d
6
, δ): 7.37 (t, 2H, m-C
6
H
5
, J H-H ) 8 Hz), 7.19
3
6 5
H
, 3J H-H ) 7 Hz),
C
4
6
H
5
2
6
H
5
2
), 70.60 (s, CHMe
2
2
(d, 2H, o-C
5.78 (s, 10H, C
), 1.50 (m, 14H, CH
{ H} NMR (benzene-d , δ): 152.86 (ipso-C
121.20 (s, C ), 112.33 (s, C ), 51.81 (s, CH
5 9
27.77, 27.41, 27.37 (s, CH ), 22.71, 22.66 (s, CH C H ,
6
H
5
, J H-H ) 7 Hz), 6.98 (t, p-C
), 2.44 (s, 2H, CH Ph), 1.75 (m, 42H, CH
), 1.20 (m, 7H, CH C
), 128.21, 127.26,
Ph), 27.85,
1
9
3
)
2
3
)
5
H
5
2
2
3
13
d
J
6
6
F
5
6
F
5
,
C
5
1
H
9
2
C
5
H
9
5 9
H ). C-
3
6
F
5
H
19
-
6
6 5
H
BF15NO‚0.5C
7
H
8
6
H
5
5
H
5
2
H, 3.27; N, 1.66.
2
C
5
H
9

8
3
16 Organometallics, Vol. 19, No. 5, 2000
:4 ratio). Anal. Calcd for C52 Zr: C, 50.82; H, 6.56.
Duchateau et al.
H
80
O
13Si
8
eters were uniquely consistent with the reported space group.
The structures were solved by direct methods, completed with
difference Fourier syntheses, and refined with full-matrix
Found: C, 50.59; H, 6.60.
Eth ylen e P olym er iza tion Exp er im en ts. Ethylene po-
lymerization reactions were carried out in a 200 mL glass
B u¨ chi autoclave equipped with a mechanical stirrer at room
temperature. In a typical experiment, 5 min before the
cocatalyst was added, a toluene (5 mL) solution of the catalyst
2
least-squares procedures based on F . All non-hydrogen atoms
were refined with anisotropic displacement parameters. All
hydrogen atoms were treated as idealized contributions. All
scatering factors and anomalous dispersion factors are con-
tained in the SHELXTL 5.10 program library.27 The detailed
data are listed in Table 1.
precursor (Cp
into the ethylene-presaturated autoclave charged with toluene
100 mL). After the addition of the cocatalyst (30 µmol)
solution, the ethylene pressure was increased to 5 atm. After
min, the polymerization was quenched by the addition of
2 2 2 2 4
Zr(CH Ph) or Zr(CH Ph) ; 50 µmol) was injected
(
Ack n ow led gm en t. This work was financed by the
Dutch Polymer Institute, which is gratefully acknowl-
edged. A. J . J ekel (University of Groningen, Groningen,
The Netherlands) is gratefully acknowledged for per-
forming the GPC measurements.
5
methanol. The polymer was then collected by filtration, washed
with methanol, and dried overnight under vacuum. The
polymers were characterized by GPC analysis.
X-r a y Str u ctu r a l Deter m in a tion of 1a a n d 4b. Suitable
crystals were selected, mounted on a thin, glass fiber using
paraffin oil, and cooled to the data collection temperature. Data
were collected on a Bruker AX SMART 1K CCD diffractometer
using 0.3° ω scans at 0, 90, and 180° in φ. Unit-cell parameters
were determined from 60 data frames collected at different
sections of the Ewald sphere. Semiempirical absorption cor-
rections based on equivalent reflections were applied.26 Sys-
tematic absences in the diffraction data and unit-cell param-
Su p p or tin g In for m a tion Ava ila ble: Tables of atomic
coordinates, thermal displacement parameters, bond lengths,
and bond angles, in CIF format, for 1a and 4b. This material
is available free of charge via the Internet at http://pubs.acs.org.
OM990855O
(
26) Blessing, R. Acta Crystallogr. 1995, A51, 33.
(27) Sheldrick, G. M. Bruker AXS, Madison, WI, 1997.