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MonomerЦDimer Equilibria in Homo- and Heterodinuclear Cationic Alkylzirconium Complexes and Their Role in Polymerization Catalysis.

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[ X I U. Bierhach. J. Reedijk, unpublished results.
[Y] R. Kuroda. S. Neidle. I. M. Ismail. P. J. Sadlei-. h o r x . ( % m i . 1983. 22. 3620.
[lo] G. Muller. J. Riede. R. Beyerle-Pfnur. B. Lippert. J A m . Clwni. So<,.1984, 106.
7999.
[ I l l S. J. S. Kerricon. P. J. Sadler. J mug^. Rcson. 1978, 3/.321
[12] 1. M. Ismail. P. J. Sadler in Ploiinuin, Goldand Orhw Mrrul ~ / l ~ ~ ~ l l f ~ / / l ~ ~
&!11.s
( A C S Swi?p. Siv. 1983. 209. 171).
[I31 J. Reedijk. Ifforg Chrm. .4rio 1992. 19H-200, 873.
1141 S. C. Dhara. Iniliiiii .1. C'hefii. 1970. K . 193.
~ ~ n l ~ J l ~ l f / ~ i
1 b, M = Hf, Cp' = C5H5
1C. C P ' =
~ Me2Si(lnd)2
Id, C P ' ~= CpH4(lnd)Z
4a - 4d
Scheme 1. Counterion of the complexes 3 and 4 is [B(C,F,),]
Monomer - Dimer Equilibria in Homo- and
Heterodinuclear Cationic Alkylzirconium
Complexes and Their Role in
Polymerization Catalysis**
Manfred Bochmann* and Simon J. Lancaster
Base-free cationic Group 4 metal alkyl complexes of the general formula [Cp,M-R]' (R = alkyl, M = Ti, Zr, Hf) are highly
active catalysts for the polymerization of olefins.[' -'I In conventional homogeneous Ziegler catalyst systems cationic species
of this kind are formed by the reaction of metallocenes with
alkylaluminum activators such as methyIaluminoxane.[". 4. 51
Aluminum-free complexes are best prepared by reacting dialkylated metallocenes [CpZMR2]with triphenylcarbenium salts of
"noncoordinating" anions,[61such as [CPh,][B(C,F,),] (2 in
Scheme 1). It is generally assumed that these reactions lead to
monomeric cationic 14-electron complexes [Eq. (a)] .['I This reaction has found widespread application for the generation o f
cationic polymerization cataIysts.'3. * '1
-
As part of our continuing interest in the characterization of
homogeneous polymerization systems based on cationic alkyl
metal complexes[2.
we have shown recently that monomeric alkyl cations [Cp,ZrR]+ are indeed the only products if
R = CH,Ph. even in the presence of an excess of [Cp,ZrR,],
since the electron deficiency of the metal center is alleviated by
the $-coordination of the benzyl ligand.'', 13' However, we noted earlier in the case of methyltitanium complexes the appearance of a short-lived dimeric intermediate, [(Ind,TiMe),(p-Me)]+ (Ind = indenyl).['0,141 Following the reaction of
methylzirconium and -hafnium complexes with [CPhJ
[B(C,F,),] (2) at low temperature has now shown that the formulation of Equation (a) does not adequately describe the
course of the reaction and that stable dimeric complexes may be
the major products, depending on the reaction conditions.
The reaction of the methyl complexes [Cp;MMe,] ( I a- 1 d)
with 2 at -60°C in CD,CI, led to the formation of dinuclear
methyl-bridged complexes 3 (Scheme 1). The reaction is essentially quantitative. Evidently adduct formation with a neutral
dialkylmetallocene stabilizes the 14-electron cation [CpiMMe]
more effectively than a solvent molecule or anion coordination.
+
[*] Dr. M. Bochmann, S. J. Lancasrer
School of Chemical Sciences. Unkersity of East Anglia
[**I
GB-Norwich N R 4 7TJ ( U K )
Telefix: In[. code + (603)259396
This woi-k was supported by the Science and Engineering Research Council.
We thank Dr. S. Holding (RAPRA Technology Ltd.) for GPC molecular
weight measurements.
1634
3 ' ) VCH Verlugsgesellsrhufi f n h H , 0-69451 Wrifilii+n, 1994
Compounds 3a-[B(C,F5),] and 3b-[B(C,F,),] are obtained
from dichloromethane/hexane mixtures as off-white. very hydrolysis-sensitive needlelike crystals, while the attempted isolation of 3c led to the precipitation of a red oil which could not
be crystallized. For spectroscopic examination the compounds
are generated in situ in CD,C12. Since rac-1 c consists of a mixture of ( R ) and ( S ) enantiomers, the formation of a cationic
dimer results in two diastereomers in a ratio of 2: 1 (Scheme 2).
The cation 3d forms a pair of diastereomers in a ratio of 1.7:1.
2
2
- PhjCMe
rac-1c
0 .a;
%-Me--
Scheme 2 Counterion
3c
g - M e - &
IS [B(Cc,F5)4]-
The stability of the dimers and the rate of reaction with excess
CPh: depends on the nature of the Cp ligands. The reaction of
3a with 2 is essentially complete on warming a solution to
-40 " C ; this gives the monomeric cation 4a.r'51
By contrast, 3c
persists even in the presence of an excess of the triphenylcarbenium salt up to a temperature of about 20°C. Although at
that stage further reaction with 2 does take place, presumably
with formation of 4c, this is quickly followed by decomposition
since 4 c is not stable in chlorinated solvents under these conditions. The cation 3d is slightly less stable than 3c, and conversion to 4d begins already at 0"C.['61 As in the case of 4c, an
unambiguous assignment of the Zr-Me ' H N M R signal of 4d
was not p~ssible.["~The compounds are insufficiently soluble
for N M R studies in toluene.
In the presence of trimethylaluminum the cations
[CpiMMe]' form preferentially the heterodinuclear complexes
[CpiM(p-Me),AlMe,]' (5a-5e) (Scheme 3). The reaction of a
0570-(I#33:94,1515-162'4S 10.00+ , 2 5 0
Angrn. Chem. Inr. Ed. Engl. 1994. 33. No 15/16
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L
5a - 5e
A
6
1'
5e
56, X = CpH4
Scheme 3 . Countenon of complex 5 is [B(C,F,)J.
Flu
=
fluorenyl.
mixture of la. AI,Me,, and 2 in CD,Cl, at -50°C gave 5a[B(C,F,),] as the main product, characterized in the 'H NMR
spectrum by two sharp singlets at 6 = - 0.48 and 6 = 0.68,
besides small quantities of 3a-[B(C,F,),] and residual AI,Me,.
In the absence of 1a there is no reaction between AI,Me, and
[CPh,]' below 20 "C. In contrast to AI,Me,, 5a does not show
fluctuating behavior in CD,CI, up to a temperature of 25°C.
There is no evidence for an intramolecular exchange process
between bridging and terminal methyl ligands of 5a, or for an
intermolecular exchange between 5a, 3a, and AI,Me,. The fluxional behavior of the latter is not influenced by the presence of
the zirconium complexes. Whereas monomeric alkyl cations
such as [Cp,Zr(q2-CH2Ph)]+ decompose slowly in CD,CI,
above -40°C and more rapidly on warming to 20°C,[315 a is
stable in dichloromethane at 20°C for several hours. The
analogous hafnium complex 5b shows similar behavior. Both
complexes are isolated as colorless, pyrophoric needles in 90 and
74 % yield, respectively. Once crystallized the complexes are
only sparingly soluble in dichloromethane or toluene.
The uma-metallocene complexes 5c-5e were obtained similarly and have been characterized in CD,CI, . They are stable in
chlorinated solvents. On cooling to -20 "C 5c-[B(C,F,),] precipitates as an oil which could not be crystallized.
The nature of the interaction between alkylaluminum compounds, such as methylaluminoxane (MAO) , and metallocene
catalysts has been the subject of much debate. While it could be
shown that the reaction of [Cp,ZrMe,] with solid M A 0 generated [Cp2ZrMe]' on the surface,['] the structure of the cationic
species and the nature of the interaction between the catalyst
and M A 0 under catalytic conditions, in other words in solution,
remains uncertain. For example, coordination of an M A 0 oxygen atom to the metal center has been suggested, as in A or
B," '.
and Erker et a]. were able to isolate complex 6 , formally
a n adduct between [Cp,ZrMe]+ and [AI,0,Me4]2 -, which may
6
be regarded as a model for such an i n t e r a ~ t i o n . ~However,
"~
does not possess any readily accessible coordination sites and is
not catalytically active in the absence of excess MAO. Since
M A 0 always contains significant amounts of AlMe, (3.5 f 1 %
have been estimated["]) and is usually employed at AIjZr ratios
Anpw.
('Iicw.
Int. Ed. Engl. 1994, 33, N o . 15/16
of l o 3 to 104,[211it seems likely that the cationic zirconium
species formed under these conditions is not [Cp,ZrMe]' but
the alkylaluminum adduct 5. This assumption is supported by
the finding that a large proportion of M A 0 can be replaced by
AIMe, without loss of productivity.[22.231 Catalysts generated
from [Cp;ZrX,]/2 mixtures in the presence of excess AIR, have
recently been reported (X = CI, Me; R = Me, Et), although the
resulting zirconium complexes have not been identified.[7g3
241
According to the current mechanistic concept olefin polymerizations with the dimeric complexes 3 are only possible if 3
dissociates partially to 1 and the active species 4 (Scheme 4). The
[
CpzZr-Me-ZrCpz
+
'
Me
I
Me
3
CpZZrMe2
11I1
I'
-[CpzZrMezl
+
[CpzZr-Me]+
4
AIMe3
F======
- AIMe?
[
CPzZr\
,,MeMe
Me
5
I+
Scheme 4.
4'
catalytic activity should therefore decrease with increasing concentration of 1, since the equilibrium is shifted towards 3 at the
expense of the productive complex 4'. However, ethylene polymerizations with 1 : 1 mixtures of 1 a and 2 in toluene produce
only traces of polymer, whereas a ratio of 3: 1 gives a productivity of 0.5 x lo6 g PE(mol Zr +)-'bar-'h-'.
We explain this
anomaly by the lack of stability of the unsubstituted cation 4a.
By contrast, complex 4c, generated from a 1 : 1 mixture of rac-1 c
and 2, polymerizes propene with excellent activities (Table I )
which decrease with increasing 1 cj2 ratio, as expected (Fig. 1 ) .
Increasing the metallocene excess from 1 :1 to 16: 1 reduces the
productivity at 20 "C by about one order of magnitude.[251
Since
higher temperatures favor dissociation, this effect is less pronounced at 60 "C but still significant.
Similarly, alkylaluminum adducts 5 are coordinatively saturated and lack a vacant orbital suitable for binding the olefinic
substrate. Initiation of chain growth requires therefore the dis-
g'', VCH Vrrlagsgesellschufi m h H , 0-69451 Wrinhrim, 1994
OS7O-O833/94/1515-1635$ /O.OO+ .-75:fJ
1635
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Table 1. Propene polymerizations with ruc-lc;Z in a inolar ratio o f 1 : l [a]
Temperature Polymer
[ Cl
yield [g]
Productivity [b]
M.p.
10'g P P ( m o l Z r + ) - ' [ C]
[C,HJ'h-'
M,
MdM.
60
21
0
- 20
- 58
98.7 0.7
45.0 i 0 01
1.75 i 0.48
0 97 i 0.13
0.21 f 0.1
13000
48600
78800
76300
121000
2.0
2.4
2.1
2.2
2.3
0.336
0.638
0 049
0.026
0.018
107.8
144.3
151.8
155.8
158.6
[a] At 1 bar C,H, pressure. I c (8.0 pmol). 2 (8.0 pinol) in toluene (20 mL), stirring
speed 1000 rpm. Polymerizations were terminated by methanol injections after 30 s.
[b] Productivities at OiC and below were calculated under the assumption of the
formation of dimeric complexes. that is [Zr'] = 0.8[CPh.T],.
.
10
0
1
1
8
4
lc:2
12
16
Fig. 1. Productivity P [l O6 g PP (mol Z r t ) - [C,H,]
h of propene polymerizations with ruc-l c:2 catalysts as a function of the lc:2 ratio at 20 and 60-C (1 bar
propene pressure).
~
~
sociation of the alkylaluminum (Scheme 4) and should be inhibited by an increase in the concentration of AIMe,. Propene
polymerizations with 1 : 1 mixtures of rac-1 c and 2 in toluene in
the presence of 1 , 10, 50, and 100 equivalents of AIMe, confirm
this assumption (Table 2). The highest productivities are found
Table 2. Propene polymerizations
[B(C,F,),] (Sc):AIMe, [a]
with
ruc-[Me,Si(Ind),Zr(p -Me,)AIMe,]-
Productivity[b]
10'g
PP(molZr+)-'
[C,H,]-'h-'
5
39.7 i 4.2
11.9 i- 0.7
1.95 i 0.23
0.94 i 0.01
107.0 i 1 . 0
94.2 3.8
78.6 i 0.64
56.9 f 2.7
8
5
8
8
8
5
8
20
20
20
20
60
60
60
60
0.847
0.163
0.027
0.013
0.383
0.336
0.271
0.204
*
M,
M,!M,,
144.3
149.0
83000
49100
2.3
1.6
148.4
121.1
1143
113.2
116.1
7400
18200
14900
1.2
2.2
1.9
9800
1.9
M.p
1 ('I
[a] Polymeri7ation conditions as given in Table 1. Polymerizations were terminated
by methanol injection after 30 s. [b] Under the assumption that [CPh:],, = maximimum [Zr'] concentration.
for an AI/Zr ratio of only 1 : 1 ; at 20°C the addition of a 100-fold
excess of AlMe, lowers the productivity by about a factor of 40.
Higher aluminum concentrations also reduce the polymer
molecular weight, probably as the result of chain-transfer reac1636
Experimental Procedure
All manipulations were carried out under dry argon
3a-[B(C,F,),]: 1 a (300 mg, 1.2 mmol) and 2 (400 mg. 0.43 mmol) were dissolved i n
CH,CI, (10 mL) at - 78 .C. The pale yello% solution was layered with hexane
(10 mL) and left to crystallize a t - 16 C. Off-white. very air-sensitive needles of
3a-[B(C6F,),I were obtained (180 mg. 0.13 mmol. 3 0 % ) The elemental analysis of
the compond was low in C due to the sensitivity to hydrolysis (C,,H,9BF,,Zr,.
calcd. C. 48.4: H. 2.8; found C. 46.9, H. 2.3). The crystalline compound was only
sparingly soluble in cold dichloromethane.
The procedure for generating solutions of3-[B(C6F,),] in situ is exemplified below
for 3a-[B(C,F,),]. l a (100mg. 0.39 mmol) and 2 (183 mg, 0.16mmol) were each
dissolved in CD,CI, (0.4 mL), cooled to -78 "C. and transferred to an NMR tube
to give a yellow solution on mixing. The sample was inserted into a JEOL EX270
spectrometer at -60 ' C . The triphenylcarbenium salt was consumed quantitatively
under these conditions. and 3a-[B(C,F,),I was observed besides residual unconverted 1 a. 3c-[B(C6F5)J was obtained as a dark red oily precipitate. In all cases the
assignment of the N M R signals was confirmed by 2D iH:13C COSY experiments.
3a-[B(C,F,),]: 'H NMR (CD,CI,. -60 C): 6 = - 0.76 (s. 3 H. Zr-(CH,)-Zr). 0.28
(s. 6 H. Zr-CH, terminal). 6.30 (5. 20 H, Cp); 13C NMR (CDICI,. -60 C):
6 = 23.81 (q. 'J(C.H) =135.8 Hz. Zr-(CH,)-Zr), 38.81 (4.'J(C,H) =120.2 Hz,
Zr-CH, terminal). 113.06 (Cp). 3b-[B(C,,F,),]. ' H N M R (CD,CI,. -20 C):
d = - 0.72 (s. 3 H. Hf-(CH,)-Hf), 0.09 (s, 6 H. Hf-CH, terminal), 6.24 (s. 20 H,
Cp); "CNMR(CD,CI,. -20"C):d = 24.42(q, 'J(C,H) =l34Hz.Hf-(CH3)-Hf),
40.93 (9. 'J(C.H) =I18 Hz, Hf-CH, terminal). 112.43 (Cp). 3c-[B(C6F,),]: Only
the Zr-CH, and Si-CH, signals were assigned. Signals in the indenyl region overlap
because of the presence of two isomers as well as triphenylethane. 'H NMR
(CD,CI,. -60°C): isomer A: h = - 2.78 (s. 3 H. Zr-(CH,)-Zr). -0.89 (s. 6 H.
Zr-CH, terminal). 0.99 (s. 3 H. Si-CH,). 1.11 (s. 3 H. Si-CH,). Isomer B:
0 = - 2.93 (s. 3 H. Zr-(CH,)-Zr). -0.88 (s, 6 H, Zr-CH, terminal), 0.98 (s, 3 H.
Si-CH,). 1.08 (s, 3 H, Si-CH,). "C N M R (CD,CI,, -60°C) (isomer A):
6 = - 3.05(Si-CH3). -1.96(Si-CH,).25.43(q, 'J(C,H) =136.1 Hz,Zr-(CH3)-Zr).
46.40 (q. 'J(C.H) =118.8 Hz. Zr-CH, terminal). 3 d : ' H N M R (CD,CI,, -60'C):
isomer A : 6 = - 2.99 (s. 3 H, Zr-(CH,)-Zr). -0.87 (s, 6 H, Zr-CH, terminal).
Isomer B: 6 = - 3.10 (s. 3 H, Zr-(CH,)-Zr), -0.96 (s. 6 H, Zr-CH, terminal).
Sa-[B(C,F,),]: AI,Me, (0.7 mmol. 0.7 mL of a 1 mM solution in dichloromethane)
was added to a solution of I a (0.18 g. 0.67 mmol) and 2 (0.8 g. 0.87 mmol) in
dichloromethane (15 mL) at -70 C. The resulting suspension was warmed to
- 20 C with stirring until the yellow-orange color of 2 faded. Addition ofcyclopenlane (10 m L ) produced a white precipitate which was filtered off. washed with
cyclopentane. and dried in vacuo. Yield 0.6 g (0.60 mmol. 90%). The product
contained traces of 3 a . Crystalline Sa was only sparingly soluble in
dichloromethane and could not be recrystallized without decomposition. ' H N M R
(270 MHz, CD,CI,, -60°C): 6 = - 0.48 (a. 6 H. terminal AI-CH,), 0.68 (s, 6 H,
p C H , ) . 6.62 (s. 10 H, Cp). "C N M R (67.8 MHz, CD,CI,. -60
(4. 'J(C,H) =115.4 Hz. AI-CH,). 38.51 (4. 'J(C,H) =113.5 Hz. /I-CH,~).118.96
(CP).
Sb-[B(C,F,),]: l b (0.35 g. 1.0mmol). 2 (0.92 g. 1.0mmol). and AI,Me, (1 mmol)
were treated similarly in dichloromethane at - 78 C to - 20' C to give white, finely
crystalline Sb (0.80 g. 74%). Elemental analysis: calcd. C,,H,,AIBF,,Hf: C. 42.46.
H. 1.78; found C . 43.46: H. 1.75. ' H N M R (270 MHz. CD,CI,. -20 C):
O = - 0 44 (s, 6 H. AI-CH,). 0.98 (5. 6 H. p C H J . 6.49 (s, 10 H, Cp). "C NMR
(67.8MHz.CD,CI2, -60 C ) : 6 = - 6.31 (4.'J(C.H) =114Hz.AI-CH,),38.20(q.
'J(C,H) =114 Hz. [L-CH,), 114.43 (Cp).
~
Ic
AIMe, Temper- PP
[pmol] [pmol] ature
yield
[ C]
[g]
5
80
280
800
8
80
280
800
tions. Ethylene polymerizations with 5 a and 5 b show a similar
trend. Large excesses of alkylaluminum are evidently not an
essential requirement for high catalytic activity and may indeed
be counterproductive.
i' VCH l+rlaysyesellschufi mhH, 0-69451 W~~mliurm,
1994
Sc-[B(C,F,),]. l c (80mg, 0.12mmol) and 2 (120mg. 0.13mmol) were each dissolved in CD,CI, (0.4 mL). The solution of 1 c was transferred into an NMR tube.
cooled to -78 "C. and treated with AI,Me, ( 1 m L of a 0 . 0 5 m ~solution). followed
by the cold (-78°C) solution of 2. Spectra were recorded between -60'C and
20 C. ' H N M R (270 MHz. CD,CI,. - 20 C). d = - 0.81 (s, 6 H, p C H , ) , -0.61
(s, 6 H. AI-CH,), 1.29 (s. 6 H. Si-CH,), 8.91 (d, 2 H. 'J(H,H) = 3.3 Hz. Ind-C,).
6.92 (d, 2 H. 'J(H.H) = 3.3 Hz, Ind-C,). 7.08-7.34 (m, 4 H , Ind-C,, partially
ohscured by Ph,CMei. 7.58 (d, 2 H. 'J(H.H) = 8.6 H7, Ind-C,). 7.77 (d, 2 H.
'J(H.H) = 8.6 Hz. Ind-C,,). " C NMR (67.8 MHz. CD,CI,, -60 C ) . 6 = -7.12
(4, 'J(C.H) =118 Hz, AI-CH,), -2.34 (Si-CH,), 38.27 (9, 'J(C,H) =113.5 Hz,
p C H 3 ) . 85.16 (Si-C,), 116.05 ( C 5 ) . 119.33 ( C 5 ) .124.98. 125.84, 126.43, 128.91.
129.45. 132.65 (C,)
Sd-[B(C,F,),]. 'HNMR(270MHz.CD,C12. -20 C):6 = - 0 . 6 3 ( s . 6 H , , ~ - C H , ) .
-0.88 (s. 6 H, AI-CH,), 4.04 ( 5 . 4 H. -C2H4-).6.20 (d. 2 H. 'J(H,H) = 3.3 HL,
Ind-C,). 6.44 (dd. 2 H, J = 3.3 and 0.7 Hz. Ind-C5). 7.07-7.38 (m. 4 H. Ind-C,.
partially obscured by Ph,CMe). 7.58 (m. 2 H. Ind-C,). 7.90 (dd, 2 H. J = 8.6 and
1.0 Hz. Ind-C,). I3C N M R (67.8 MHz. CD,CI,. -60 C ) : 6 = -7.03 (4.
'J(C,H) =116.4Hz.AI-CH3).30.93(C,H,),37.32(q.
'J(C.H) =113.7Hz.pCH3),
108.30 (C-), 117.05 (CJ. 122.68 (bridgehead-C of C,) 124.49, 128.28, 127.44.
328.82. 129.00, 131.00 (re)
0570-0R33i94;1515-1636
B 10.00+.25;0
Anjien Clirjm. h i . Ed. Enyl. 1994, 33, N o . 15/16
COMMUNICATIONS
Se-[B(C,F,),]: ' H N M R (270 MHz, CD,CI,. 25'C): 6 = - 0.72 (s, 3 H, AI-CH,
terminal). -0.63 (s. 3 H. AI-CH, terminal), -0.57 (s, 6 H, p-CH,), 2.49 (s, 6 H ,
Me,C). 5 58 (t. 2 H. 'J(H.H) = 2.6 Hz, C 5 ) ,6.32 (t. 2 H , 3 J ( H , H ) = 2.6 Hz. C5);
Flu: 7.75 (1. 2 H. 'J(H.H) = 8.58 Hz). 7.34 (t. 2 H, ,J(H,H) = 8.91 Hz), 7.96 (d,
2 H. 3J(H,H) = 8.91 Hz), 8.22 (d. 2 H, ,J(H.H) = 8.58 Hz). "C NMR(67.8 MHz,
CD,CI,, 25 C). d = -7.13 (AI-CH, terminal), -7.01 (AI-CH, terminal). 28.55
(Me,C). 28.63 (Me.,C). 29.02 (Af-CHJ; C,H,: 74.14, 102.75, 117.63; Flu: 111.95,
121.29, 121.94. 124.76. 125.12. 127.22. 131.41. The resonances of the anion are
identical to those of noncoordinated [B(C,F,),]- and have not been listed.
Olefin pol>merizations: low-sulfur toluene (20 mL) was equilibrated a t the stated
temperalure with the olefin under 1 bar pressure. The appropriate amount of a
standard solution of thc dialkyl metallocene (and of AI,Me, where applicable) was
injected. lollowed by a solution of 2 in toluene. Immediate rapid polymerization was
observed. The reactor was stirred magnetically at 1000 rpm. The reactions were
terminated by the injection ofmethanol (2 mL). The polymer was precipitated with
meth;inol'HCI. washed with methanol. and dried at 70 C to a constant weight. The
productibities given in the Tables are the averages of at least two independent
experiments per data point and were calculated by using the propene solubilities in
toluene given in [?lb]. Melting points of polymers were determined with a DuPont
DSC 10 differential scanning calorimeter. Polymers have not been fractionated.
Molecular weights and polydispersities were determined by gel permeation chromatography (polystyrene standard. Ptgel-column. 1,2-dichlorobenzene. 140 "C).
[19] G. Erker. M. Alhrecht, S. Werner,C. Kriiger, 2. Nurucforsrh. B 1990.45.1205
[20] L. Resconi, S. Bossi, L. Abis, Macromolecules 1990, 23, 4489.
[21] See for example: a) N. Herfert. G. Fink, Mukromol. Chem. Mucromol. Symp.
1993,66, 157; b) B. Rieger. X. Mu, D. T. Mallin, M. D. Rausch. J. C. W Chien,
Macromolecules 1990. 23, 3559; c) W A. Herrmann. J. Rohrmann. E.
Herdtweck, W. Spalek, A. Winter, Angeit.. Chern. 1989, 101. 1536; Angew.
Chem. Inl. Ed. Engl. 1989, 28. 1511; d) W. Spalek, M. Antberg, J. Rohrmann,
A. Winter, B. Bachmann, P. Kiprof, J. Behm, W. A. Herrmann. ihrd. 1992, 104,
1373 and 1992, 31. 1347.
[22] J. C. W. Chien, B. P. Wang. J. Polym. Sci. Purr A ; Polym. Chem. 1988.26,3089.
[23] The formation of 5 does not exclude the possibility of Z r - 0 coordinatlon like
that in 6. It IS conceivable. however, that this side reaction may contribute to
the deactivation of the catalyst.
[24] J. C. W. Chien. W. M. Tsai, Mukromol. Chem. Mucromol. $ymp. 1993, 66, 141.
Heterohimetallic lanthanide complexes [Cp,M(pMe),AIMe,] (M = Sc. Y,
Gd, Dy, Ho, Er, Tm. Yb) which are isostructural to 5 a are known: J. Holton.
M. F. Lappert. D. G. H. Baliard, R. Pearce. J. L. Atwood. W. E. Hunter. J.
Chem. Soc. Dullon Trans. 1979, 45.
[25] By contrast, Fink et al. found for ethylene polymerizations with the system
1 c/[HNnBu,][B(C,F,),] a n activity increase with increased 1 c:[HNnBu,] ratio. whereas propene polymerizations showed a maximum at a ratio of I : 1: N.
Herfert, G. Fink, Mukromol. Cheni. Rapid Commun. 1993, 14. 91.
Received: March 4. 1994 [26729/6730IE]
German version: Angew. Chem. 1994. 106, 1715
Review iirticles: a) F. S. Dyachkovskii in Coordinulion Po/vmrrirariun, (Ed.: J.
C. W. Chien). Academic Press, New York, 1975, p . . 199; b) R. F. Jordan. Adv.
Or,cyioriie/. Cliem.1991, 3.7. 325; c) T. J. Marks, Ace. Chem. Res. 1992, 25, 57;
d ) M . Bochmann, Nachr. Chem. Tech. Lnh. 1993, 41, 1220.
M Bochmann. A. J. Jaggar, J. C. Nicholls. A n g e w Chem. 1990. 102. 830;
A n x m Chem. lnr. Ed. EngI. 1990, 29. 780.
M . Bochminn. S. J. Lancaster, Or,qunometal/ics 1993, 12. 633. arid references
therein.
H. Sinn. W. Kaminsky. Ads. OrRunorner. Chern. 1980, 18. 99.
C. Sishtu. R. M. Hathorn, T. J. Marks, J. Am. Chem. Soc. 1992. 114, 1112.
a ) M. Bochmann, Angew Chem. 1992, 104. 2206, Angen.. Chem. I n [ . Ed. Engl.
1992. 31. 1181. b) H. W. Turner (Exxon), EPA. 0277004, 1988 [Chrm. Ah.rtr.
1989. 1 1 0 . 582YOa1: c) A. R. Siedle, W. M . Lamanna. R. A. Newmark, Mukromu1 Clic,m. .Wuuomol. Symp. 1993. 66. 215.
See lor example: a ) K. Hortmann. H. H. Brintzinger, NW J. Chem. 1992, 16,
51. b) P. Burger. K. Hortmann, H. H. Brintzinger, Mukromol. Chem. Macrornol Svnip. 1993, 66, 127: c) M. H. Prosenc, C. Janiak, H. H. Brintzinger,
Orjiaiioin[,/~i//i(,.~
1992. 11. 4036: d) L. Cavallo, G. Guerra, M. Vacatello, P.
1991, 24, 1784; e) L. A. Castonguay, A. K. Rappe.
Corradini, Mucrunn~l~culcs
J. A m Chcm. SOC.1992. 114. 5832, f) J. R. Hart. A. K. Rappe, ibrd. 1993, 115,
6159; g) J. A. Ewen, M. J. Elder, Mukromol. Chem. Mucromol. S.ymp. 1993,66.
179: h) A. R. Siedle. W. M. Lamanna. R. A. Newmark, rhid. 1993, 66, 215.
J A. Ewen. M. J. Elder (Fina Technology Inc.). EPA 0426637, 1990 [ C h t w .
Ahstr. 1991. 1 / 5 . 136988dl
J. C W. Chien, W. M. Tsai, M. D. Rausch, J. Am. Cliem. Soc. 1991, 113, 8570.
M. Bochmann, S. J. Lancaster, J. Orgunomrr. Chem. 1992,434. C1.
a ) J A . Ewen, M . J. Elder. Mukromol. Chem. Macromol. Symp. 1993, 66. 179;
b) J. C . W. Chien. W. M. Tsai, ibid. 1993. 66. 141; c) J. C. W. Chien, B. Xu,
Mukroriiol Clwm. Rapid Conimun. 1993, (4. 109.
a ) M . Bochmann. A. J. Jaggar, L. M. Wilson. M. B. Hursthouse, M. Motevalli,
P o l h ~ d r o n1989,8,1838; b) M. Bochmann. G. Karger, A. J. Jaggar, J. Chem.
So< ('hem Commun. 1990.1038; c) M. Bochmann. A. J. Jaggar, J. Orgunomer.
Cheni. 1992. 424, C5.
Mixturesof[Cp,Zr(CH,Ph),]and[Cp,Zr(CH2Ph)]+inratiosfrom2:1 to 11 : I
between - 20' C and - 60 'C in CD,CI, fail to provide evidence for the formation of dimeric complexes: M. Bochmann. S. J. Lancaster, Organome~allics,
1994. 13, 2235.
A related dimeric thorium complex is known: X. Yang, C. L. Stern. T. J. Marks,
Or,qunnnietul/ics 1991. lo3840.
The Zr-CH, resonance signals of the monomeric complex 4 a could not be
assigned with certainty. Singlets at 6 = 0.76 and 0.77 and a weaker signal at
6 = 0.66 are replaced on addition of [DJpyridine by a single signal at 6 = 0.35
( - 50 'C). The signals a t 6 = 0.76 and 0.77 remain unchanged on warming,
whereas the signal at 6 = 0.66 broadens.
The stability of dimeric methyl complexes of unsu-zirconocenes has consequences for the evaluation of the catalytic activity of these species at low
temperatures. The stability o f 3 c and 3d at low temperature suggests that only
half as many cationic centers are formed as are expected on the hasis of Equation ( a ) .
The 'H N M R spectrum of 4c a t - 30 .C shows signals for Zr-Me a t 6 = - 0.47
and -0.61 which broaden on cooling. This finding may be consistent with the
presence of solvent and anion adducts of 4c, an unambiguous assignment was.
however. not possible.
E. Gannetti. G. M . Nicoletti, R. Mazzocchi, J. Polym. Sci. Purr A : Polym.
Chtw 1985. 23, 2117.
An,yrii.
C'hrni. h r . Ed. Engl. 1994, 33, N o . 15/16
63
The First Decaisopropylmetallocene:
One-Pot Synthesis of [Rh(C,zFr,),]PF,
from [Rh(C,Me,),]PF, by Formation of
20 Carbon- Carbon Bonds **
Dirk Buchholz and Didier Astruc*
Dedicated to Dr. Frangoise Moulines
on the occasion of her 60th birthday
Decamethylmetallocenes [MCpT] (Cp* = C5Me,)[' -31 have
proven highly valuable as magnetic materials['] and catalysts.[']
Transition metal complexes with pentaisopropylcyclopentadienyl ligands show a unique dire~tionality,[~,
51 and form a new
type of chiral metallocene.[61 The remarkable robustness of
these metallocenes suggests their application in chemotherapy
and catalysis. Sitzman et a1.'4,71have shown that the reaction of
pentaisopropylcyclopentadienylsodium with iron chloride does
not lead to decaisopropyl ferrocene, but electron transfer takes
place to give the C,iPr; radical.['] We now report the synthesis
of the first decaisopropylmetallocene and compare the "builtfrom-inside'' route starting from decamethylcobaltocenium and
decamethylrhodocenium.
The homologation of permethylated ligands in cationic 18electron complexes by using excess CH,I and tBuOK has been
shown to work with first-row transition metal sandwich complexes containing only one permethylated ring [Eqs. (1) and (2)J.
[CoCp*Cp]PF,
Me1 + rBuOK
THF, 60 "C
[Co(C,iPr,)Cp]PF,
Attempts to extend this route to first-row transition metal
sandwich complexes in which both rings are permethylated
[*I Prof. D. Astruc. Dr. D. Buchholz
Laboratoire de Chimie Organique et Organometallique
Universite Bordeaux I, U R A CNRS 35
351, cours de la Liberation, F-33405 Talence Cedex (France)
Telefax: Int. code 56846646
[**I This work was supported by the CNRS, the University Bordeaux I. and the
Region Aquitaine. D. B. thanks the Deutsche Forschungsgemeinschaft for a
postdoctoral grant.
+
VCH Verlu~s,qesellschajrmhH, 0-69451 Wiwheim, 1994
0570-0833/94/ISlS-l637$10.00+.25/0
1637
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thein, homo, catalysing, alkylzirconium, role, monomerцdimer, complexes, heterodinuclear, equilibrium, polymerization, cationic
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