J. Am. Chem. Soc. 2000, 122, 6315-6316
6315
Reaction of Vinyl Chloride with a Prototypical
(PVC) is observed, but surprisingly, low-molecular-weight (M
) 500) atactic oligopropylene is formed (95% vs consumed VC).
n
8
Metallocene Catalyst: Stoichiometric Insertion and
+
2
3
No identifiable rac-(EBI)Zr indenyl H or H resonances are
â-Cl Elimination Reactions with rac-(EBI)ZrMe and
1
present in the ambient temperature 500-MHz H NMR spectrum
Catalytic Dechlorination/Oligomerization to
of the red solution. However, low-temperature spectra reveal that
Oligopropylene by rac-(EBI)ZrMe2/MAO
[
{rac-(EBI)ZrCl}
2
(µ-Cl)][MeB(C
6 5 3
F ) ] (2, 10/1 mixture of dia-
Robert A. Stockland, Jr. and Richard F. Jordan*
stereomers) is the major Zr-containing species present (94% vs
1
ZrCl and rac-(EBI)ZrCl
by treatment with 0.5 equiv of [NBu
9
). The dinuclear cation of 2 is formally an adduct of rac-(EBI)-
Department of Chemistry, 5735 South Ellis AVenue,
The UniVersity of Chicago, Chicago, Illinois 60637
+
2
(3). The identity of 2 was confirmed
Bn]Cl (CD Cl , 25 °C, 1
3
2
2
ReceiVed March 16, 2000
min) to quantitatively generate 3; however, 2 could not be isolated
1
in a pure form. The H NMR signals for 2 are sharp below -50
The development of catalysts for the coordination/insertion
polymerization of vinyl chloride (VC) and other polar vinyl
monomers is of interest because of the possibility that polymer
composition, microstructure, and molecular weight can be con-
trolled by manipulation of catalyst structure. Several recent patents
and reports describe the polymerization of VC by group 4 metal
°
C but collapse upon warming of the sample and broaden into
the baseline at ambient temperature. The variable-temperature
1
(
-73 to 25 °C) H NMR spectra of 2 are unaffected by the
addition of 3 (5 equiv), which implies that the fluxional process
involves intramolecular bridge/terminal chloride exchange rather
+
than reversible cleavage of the {rac-(EBI)ZrCl}
Compound 2 decomposes above 40 °C (CD Cl
2
(µ-Cl) cation.
+
single-site catalysts, including rac-(EBI)ZrMe species (EBI )
2
2
) to 3 and other,
1
,2-bis(indenyl)ethylene), rac-(EBI)ZrMe /MAO (MAO ) me-
2
unidentified products which precluded high-temperature NMR
studies. Several related dinuclear metallocene cations have been
1
thylalumoxane), and other metallocene catalysts. However, little
information concerning the mechanisms of these reactions or the
characterized including [{rac-C
(
2
H
4
(C
M ) Ti, Zr) and red [{rac-(EBI)ZrMe}
In the second stage of the reaction of 1 with VC, which is
9
H
10
)
2
MCl}
2
4
(µ-Cl)][AlCl ]
2
characterization of the resulting polymers is available. To probe
10
11
2
(µ-Me)][B(C
6 5 4
F ) ].
these issues, we have investigated the reactions of rac-(EBI)-
+
+
ZrMe complexes with VC. Here we report that rac-(EBI)ZrR
complete after 24 h at 25 °C, the initially formed red solution
evolves to a yellow solution (eq 2). NMR studies establish that
species react with VC by insertion and rapid â-Cl elimination,
and we describe several interesting ramifications of this chemistry.
Little is known about the reactions of early transition metal
complexes with VC or other vinyl halides. The reaction of Cp*
ScMe (Cp* ) C Me ) with vinyl fluoride yields Cp* ScF and
propylene via insertion and subsequent â-F elimination. Treat-
ment of in-situ-generated Cp Zr(butene) with 2-haloalkenes
CH dCRX) yields Cp Zr(CRdCH )X oxidative-addition prod-
ucts (X ) Cl, Br). Additionally, the reaction of Cp
1/4) with CH dCRX substrates yields Cp Ti(CH
allyl species, most likely via AlMe
of Cp Ti(CH CRXCH
) titanacyclobutane intermediates.5
The reaction of VC with rac-(EBI)Zr(Me)(µ-Me)B(C
proceeds in two stages. In the first stage, which is complete within
min at 25 °C in CD Cl solution, 1 reacts with a ca. 15-fold
2
-
5
5
2
3
2
(
2
2
2
4
2
TiCl
CRdCH
2
/AlMe
3
(
2
2
2
2
)X
an additional 0.5 equiv of VC is converted to atactic oligopro-
pylene and that the only organometallic species present in
3
-mediated â-X elimination
2
2
2
significant concentrations in the final reaction mixture are 3 (100%
(1)6,7
1
6
F
5
)
3
by H NMR, 81% isolated) and B(C
6 5
F )
3
(only species observed
1
9
by F NMR). The final yield of the oligopropylene determined
1
5
2
2
by H NMR is >95% vs consumed VC. Thus, the overall reaction
excess of VC to produce a dark red solution (eq 1). NMR studies
in stages 1 and 2 is that given in eq 3.
6 5 3
(6) (a) Use of B(C F ) to generate cationic metal alkyl species: Yang,
X.; Stern, C. L.; Marks, T. J. J. Am. Chem. Soc. 1994, 116, 10015. (b)
Generation of 1: Dagorne, S.; Rodewald, S.; Jordan, R. F. Organometallics
1
997, 16, 5541.
7) Control experiments show that neither rac-(EBI)ZrMe
the precursors of 1, reacts with VC under these conditions.
8) (a) Cheng, H. N. Macromol. Symp. 1994, 86, 77. (b) M
(
2 6 5 3
nor B(C F ) ,
reveal that 1.5 equiv of VC is consumed and a 1:1 mixture of
(
n
values were
-
1
B(C
F
6 5
)
3
and MeB(C
F )
6 5 3
is formed. No poly(vinyl chloride)
determined by H NMR assuming one unsaturated end group per chain.
1
2
3
(
2 2
9) (a) H NMR of 2 (CD Cl , -73 °C, indenyl H and H region, J in Hz)
(1) (a) Matsukawa, T.; Kiba, R.; Ikeda, T. Japan Patent 08208736 (Chisso
major isomer, δ 6.82 (d, J ) 3, 1H), 6.48 (d, J ) 3, 1H), 6.10 (d, J ) 3, 1H),
5.91 (d, J ) 3, 1H); minor isomer, 6.78 (d, J ) 3, 1H), 6.38 (d, J ) 3, 1H),
6.32 (d, J ) 3, 1H), 5.96 (d, J ) 3, 1H). (b) If stage 1 is terminated before
completion (1 min at 25 °C followed by immediate cooling to -78 °C), the
Corp.); Chem. Abstr. 1996, 125, 276902. (b) Taeji, K.; Uozumi, T.; Soga, K.
Polym. Prepr. Jpn. 1995, 44, 2. (c) Kiyoshi, E.; Saitoh, M. Prepr. 7th SPSJ
International Polymer Conference, Yokohama, Japan, October 26, 1999; paper
1
2
7A06.
low-temperature H NMR spectrum contains additional resonances for an
(
2) The free radical polymerization of VC initiated by group 4 metallocenes
intermediate species that is assigned as rac-(EBI)Zr(Cl)(µ-Me)B(C F ) (4).
6 5 3
1
2
3
under photochemical conditions has been reported: Nagy, S. M.; Krishnamurti,
R.; Cocoman, M. K.; Opalinski, W. M.; Smolka, T. F. World Patent WO
9
2 2
H NMR (CD Cl , -73 °C, indenyl H and H and Me regions): δ 7.09 (d,
J ) 3, 1H), 6.42 (d, J ) 3, 1H), 6.34 (d, J ) 3, 1H), 6.05 (d, J ) 3, 1H),
923124 A1 (Occidental Chemical); Chem. Abstr. 1999, 130, 338530.
-0.40 (s, 3H, MeB). Addition of [NBu
3
Bn]Cl to a mixture of 4 and 2 results
(
3) Burger, B. Ph.D. Thesis, California Institute of Technology, 1987.
in complete conversion to 3.
(
4) Takahashi, T.; Kotora, M.; Fischer, R.; Nishihara, Y.; Nadajima, K. J.
(10) Brintzinger, H. H. In Ziegler Catalysts; Fink, G., Mulhaupt, R.,
Brintzinger, H. H., Eds.; Springer-Verlag: New York, 1995; p 181.
(11) Bochmann, M.; Lancaster, S. J. Angew. Chem., Int. Ed. Engl. 1994,
33, 1634.
Am. Chem. Soc. 1995, 117, 11039.
(5) Hanzawa, Y.; Kowase, N.; Taguchi, T. Tetrahedron Lett. 1998, 39,
5
83.
1
0.1021/ja000939k CCC: $19.00 © 2000 American Chemical Society
Published on Web 06/13/2000