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Control of the Molecular Weight of Polyethene in Syntheses with Bis(ylide)nickel Catalysts.

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Control of the Molecular Weight of Polyethene
in Syntheses with Bis(y1ide)nickel Catalysts
By K . Alexander Ostoja StarzewskP and Josef Witte
We recently reported on highly active Ni-catalyst systems for ethene polymerization. These were generated
from bis(cyclooctadiene)nickel(o), Ni(cod),, a carbonylstabilized and a non-stabilized ylide, Ph3PCRiC(0)R2and
R2PCR4RS, respectively.[” In the catalytically active,
square-planar nickel complex, the non-stabilized ylide is
structuraAy intact C-coordinated, whereas the stabilized
ylide is PO-coordinated due to rearrangement. The activity
of the catalyst can be optimized by variation of the intact
ylide ligand; but modification of the substituent R2 in the
carbonyl-stabilized ylide ligand also increases the catalytic
activity in the Ni(cod),/Ph3PCHC(O)R2/Me,PCH, system : On going from the formylmethylene(tripheny1)phosphorane l a via the acetyl derivative l b to the benzoylmethylene(tripheny1)phosphorane l c (R2= H, Me, Ph) the
turnover number increases to ca. 0.5 x lo5 moles ethene
per mole of nickel.[’I
Characterization of the polymers showed that the average chain length of the ethene polymerizates also increases
with increasing catalyst activity. The intrinsic viscosities in
tetralin at 140°C do not, however, exceed 0.2 dL/g, which
corresponds to molecular weights M of about 5 x lo3 g/
mole.[*I We have therefore tried to noticeably increase the
range of molecular weights accessible with this Ni-catalyst
system by further variation of the carbonyl-stabilized ylide
ligand.
With the three ligands 2a-2c, we have indeed been able
to obtain novel, very active bis(y1ide)nickel polymerization
catalysts, which afford access to polyethene (PE) in practically all molecular weight ranges from PE waxes and hard
waxes through high molecular weight high-density polyethene (HDPE) to ultrahigh molecular weight polyethene
(UHMW-PE) with M > lo6 g/mole (Table I).
2b
2a
2c
The new catalysts are obtained in situ by stoichiometric
reaction of the three components in toluene at 40-60°C
(cf. Ref. 111). The triphenylphosphane-maleic anhydride
adduct 2al3I has so far found no use as ligand; the sulfonated benzoylmethylene(tripheny1)phosphorane 2b, R =
C6H5, and the triphenylphosphane-benzoquinoneadduct
2c,131on the other hand, have already been employed successfully in combination with nickel(0) complexes and triphenylphosphane as catalysts for the synthesis of lowmolecular weight PE waxes ( a - o l e f i n ~ ) ,but
~ ~ .nothing
~~
was
known about the formation of high molecular weight PE in
this connection.
The 2a-catalysts are soluble in non-polar solvents,
whereas the 2b- and 2c-catalysts are nearly insoluble. The
2b-catalysts are soluble in dimethylformamide (DMF),
and polymerizations can be initiated with DMFItoluene
solutions; the resulting polyethene, however, has a relatively low molecular weight (Table 1); the intrinsic viscosities usually lie below 1 dL/g, i.e. the molecular weights are
below 5 x lo4 g/mole.
Regarding molecular weight control,[”] the 2c-catalyst
system is the most versatile. Depending upon which nonstabilized ylide is used, the intrinsic viscosities of the PE
samples in tetralin at 140°C reach values of u p to 10 dL/g
and more, from which molecular weights of 2 10” g/mole
can be calculated. In these catalyst systems, which are free
n
a
0
Table I. Polyethene synthesis with bis(yltde)ntckel catalysts prepared from Ni(cod)2, Ph3PCR’C(0)R2 (“R3PoOB”) and R:PCRJR‘ (“R,P-X”).
(For experimental details see Ref. [I].)
n
RiPoOo
U
G
RIP-X
Catalyst
injection [a]
~~
Ib
lc
2a
2b
2b
2c
2c
2r
2c
2c
2c
2c
iPr3PCH2
iPr,PCH2
Ph3PCHMe
Ph3PCH2
Ph,P(CH),Ph [el
Ph,PCHMe
Ph,PNrBu
(PhO),PO
Ph,PO
Ph3PCHMe
PhiPCHMe
Ph3PCHMe
~
Solvent
kl
Polymerization
temperature [b]
I”C1
Intrinsic viscosity
in tetralin at 140°C
W/gl
PE molecular weight M
[g/molel [cl
~~~
m.p.i.
m.p.i.
s.p.i.
m.p.i. [d]
s.p.i. [fl
s.p.i.
s.p.i.
s.p.i.
s.p.i.
s.p.i.
s.p.i.
s.p.i.
cyclohexane
cyclohexane
cyclohexane
cyclohexane
cyclohexane
cyclohexane
cyclohexane
cyclohexane
cyclohexane
ethyl acetate
acetone
DMF
ca. 110
ca. 110
ca. 100
ca. 100
60- 100
0.07
0.10
0.5
0.7
1.5
2.1
3.2
5.8
65-85
9.6
ca. 100
ca. 100
ca. 100
0.2 I
0.16
0.12
12515
1 3 0 1 10
ca. 100
1.3
103
2.1 x 10’
1.87 x 10‘
2.97 x 104
8.44 x 104
1.34~
10‘
2.38 x 10’
5.38 x 10’
1-07x 10’
5.7 x 103
3.9 x 10’
2.7 x 10’
[a] m.p.i. =multi-pulse injection, 2 mmol in 200 mL oftoluene; s.p.i.=single-pulse injection, 2 mmol in 50 rnL of toluene. [b] Polymerization pressure ca. lo2 bar. [ c ]
The PE molecular weight was estimated using the q / M relationship for linear PE: 7 = 3 . 8 x 1 0 - 4 x M”” (see Ref. 191). [dl I n toluene/DMF. [el Ph,P(CH).?Ph
[fJ 1 mmole of catalyst. [gl I L.
denotes Ph,P=CH-CH=CH-Ph.
[*] Dr K. A. Ostoja Starzewski, Dr. J. Witte
Bayer AG. Zentrale Forschung und Entwicklung
Wissenschaftliches Hauptlaboratorium
D-5090 Leverkusen 1 (FRG)
Angew Chem. Inr. Ed. Engl. 26 (1987) No. I
of alkylaluminum c ~ m p o u n d s , ” termination
~
and transfer
reactions can accordingly be suppressed as a function of
the ligand in favor of an uninterrupted growth of the
polymer chains. The second ylide IigandL8]and the polarity
0 VCH Verlagsgesellschafi mbH. 0-6940 Weinheim. I987
0570-0833/87/0101-0063 S 02.50/0
63
of the solvent provide chemical means for tuning the t c -
HO-C
catalyst system.
Received: August 19, 1986;
revised: October 2, 1986 [Z 1906 IE]
German version: Angew. Chem. 99 (1987) 76
I
CH3
H
11.1 K. A. Ostoja Starzewski, J. Witte, Angew. Chem.
97 (1985) 610; Angew.
Chem. Inr. Ed. Engl. 24 (1985) 599.
I21 The polymers with a molecular weight M of ca. lo' g/mole are PE waxes.
Higher molecular weight types are hard waxes ( M S lo4 g/mole), HDPE
( M = 10' g/mole), and UHMW-PE ( M = 10' g/mol).
[3] a) A. Schonberg, A. F. A. Ismail, J. Chem. SOC.1940, 1374; b) R. F. Hudson, P. A. Chopard, Helu. Chim. Acra 46 (1963) 2178; c) G. Aksnes, Acra
Chem. Scand. 15 (1961) 692.
(41 a) D. L. Beach, J . J . Harrison, US-Pat. 4293727 (October 6, 1981), Gulf
Research and Development Company. b) Y. V. Kissin, D. L. Beach, J .
Po1.vm. Sci. Polym. Chem. Ed. 22 (1984) 333.
[5] P. Haussle, DOS 2923206 (December I I , 1980), Chemische Werke Huls
AG.
[6] HDPE molecular weights are usually catalyst-specifically regulated down
to the desired level. This is usually achieved by increasing the temperature or by use of hydrogen, comonomers, or a second metal component,
i.e. generally by termination or transfer agents. Cf., e.g., a) K.-Y. Choi, W.
H. Ray, J . Macromol. Sci. Rev. Macromol. Chem. Phys. C25 (1985) I ; b)
W. Kaminsky, K. Kulper, S. Niedoba, Makromol. Chem.. Macromol.
Symp. 3 (1986) 377; c) J. Boor: Ziegler-Narra-Catalysts and Polymerizarions, Academic Press, New York 1979, Chap. 10.
171 We obtain modified catalysts with organoaluminum compounds.
181 For a comparison of the electronic structure of R,PCH2 ligands with
R3PNX ligands and R3P0 ligands, cf. also K. A. Ostoja Starzewski, H.
tom Dieck, Inorg. Chem. 18 (1979) 3307, and references cited therein.
[9] R. Kuhn, H. Kromer, G. Rossmanith, Angew. Makromol. Chem. 40/4/
(1974) 361.
2
1
3
R
R
4 a , n = 0 , R = CH -CO H
2
2
4b, n = 1 , R = Et
R
R
reactive dialcohol 7, which was allowed to react in situ
(see Scheme 1) at - 60°C. Work-up and chromatographic
purification furnished the 21,24 :22,23-bis-trimethylene2,3,7,8,12,13,17,18-octaethylporphyrinogen8 as the tetrahydrate in the form of fine needles that are stable on drying (m.p. 109oC)."ol According to spectroscopic data, especially MS and 'H-NMR data, 8 is a dimeric condensation
product of 7.
Biomimetic Synthesis of
a Twofold N,N'-Bridged Porphyrinogen**
By Rarf Timmermann. Rainer Mattes, and
Burchard Franck*
Among the reactions of heme biosynthesis,l','l the cyclizing condensation of four molecules of the monopyrrole
precursor porphobilinogen 1 is of particular significance
for the development of biomimetic syntheses. 1 and structurally related pyrrole derivatives undergo highly selective
acid-catalyzed condensation to give the porphyrinogens,
the cyclic tetrapyrrole precursors of the p ~ r p h y r i n s . ' ~In
.~]
continuation of our studies on the practicability of this
biomimetids1cyclotetramerization we were able to synthesize novel, non-planar and fourfold expanded porphyrinogens 4aIb1and 4b"I by acid-catalyzed condensation of
the monopyrroles 2 and 3, respectively, and to convert
them into the corresponding porphyrins. We now report
on the use of this biomimetic principle for the synthesis of
the twofold N. "-bridged porphyrinogens 8 from the trimethylenedipyrrole 7, which can be regarded as a simplified N , "-bridged dimer of porphobilinogen 1.
The readily accessible[81 3,4-diethyl-2-formylpyrrole 5
was alkylated in the form of its potassium salt with 1,3dibromopropane to the dialdehyde 6 using a method described by Burger and Dreier."] For activation prior to
acid-catalyzed condensation, 6 was reduced to the very
[*I
Prof. Dr. B. Franck, DipLChem. R. Timmermann
Organisch~chemischeslnstitut der Universitat
Orleansring 23, D-4400 Munster (FRG)
Prof. Dr. R Mattes
Anorganisch-chemisches lnstitut der Universitat
Corrensstrasse 36, D-4400 Munster (FRG)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen Industrie.
64
0 VCH VerlagsgeseilschaJt mbH. 0-6940 Weinheim. 1987
H
CHO
5
6
8, 9% based on b
7
Scheme I . Synthesis of 8 from 5 IS]. Reaction conditions: a) KOH/dimethyl
sulfoxide, 1,3-dibromopropane, room temperature, 14 h; chromatography on
silica gel (Merck 0.063-0.2 mm), petroleum ether/ether 4 : 1. b) NaBH,/
MeOH, room temperature, 20 min; p-TosOH/AcOH/MeOH, -60°C; chromatography on AII03, Activity I11 (Woelm), petroleum ether/ether 95 : 5
"01.
An isomeric structure with crossed trimethylene bridges,
the 21,23 :22,24-bis-trimethylene derivative, could be ruled
out on the basis of the MS and 'H-NMR data and by the
isolation and structural elucidation of a condensation intermediate. Thus, as expected for 8, preferred splitting of
the molecule into two
took place in the
spectrometer; in the case of crossed coupling this would re-
057#-#833/87/0101-0064 $ 02.50/0
Angew. Chem. Inr. Ed. Engl. 26 (1987) No. I
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nickell, polyether, molecular, synthese, weight, bis, ylide, catalyst, control
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