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Highly Active Ylide-Nickel Catalysts for the Polymerization of Ethylene.

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catalysts, but in this respect had not been studied up to
We have now found that the reaction of bis(cyc1ooctadiene)nickel(o) with benzoylmethylenetriphenylphosphorane and trimethylmethylenephosphorane in toluene yields
a highly active homogeneous catalyst for the polymerization of ethylene. The spectroscopic data for this catalyst
are in accord with the structure 3, which formally arises
via oxidative addition of the Ph3P group of the stabilized
ylide and nucleophilic attack of the carbonyl oxygen atom
and of Me3PCH2 on Ni. The reaction can be followed by
i P-NMR spectroscopy. After a few minutes, a product has
formed that exhibits two doublets ( J = 7 Hz) in the 'H-decoupled 3'P-NMR spectrum (Fig. la); the assignment of
the signals was made by analyzing the undecoupled spectrum (Fig. lb). Concentration of the solution affords a yellow solid whose elemental analysis is in accord with the
composition of 3.
Further details of the crystal structure investigation are available on request from the Fachinformationszentrum Energie Physik Mathematik, D75 14 Eggenstein-Leopoldshafen 2, on quoting the depository number
CSD 51 149, the names of the authors, and the journal citation.
[XI For example, 6a: colorless crystals, m.p. =71 "C (ethyl acetatelether): 'HNMR (200 MHz, CDCI,): 6=2.96 (ddd, l H , 'J(H/H)=7.1, 'J(P/
H)= 11.48. 'J(H/H)=0.75 Hz, 2-H), 3.40 (5, 3 H , OMe), 3.45 (dd, I H,
'J(H/H)=7.1, 'J(P/H)= 10.7 Hz, 8-H), 3.91 (dd, 1 H, 'J(H/H)=2.3,
'J(P/H)= 10.3 Hr, 5-H), 4.41 (br. s, 1 H, 4-H), 6.90-7.85 (m, 14H, areneH): "C-NMR (CDCI,): S=39.62 (dd, 'J(C/H)= 170.7, 2J(P/C)= 1.9 Hz,
C-2). 40.72 (d, 'J(C/H)= 171.0 Hz, C-8). 51.62 (dd, 'J(C/H)= 135.0, 'J(P/
C)=6.7 Hz, C-5), 52.40 (d, 'J(P/C)=99.0 Hz, C-I), 57.27 (4, ' J ( C /
H ) = 143.7 Hz, CHI), 101.30 (dd, 'J(C/H)= 168.2, 'J(P/C)=4.5 Hz, C-4),
120.69-132.71 (arene-C), 136.04 (s, C-3), 151.47, 152.70 (each s, C-6/C7).- 7a : colorless crystals, m.p. = 173°C (decomp.) (ethyl acetate/ether);
'H-NMR (200 MHz, CDCI'): 6=2.76 (dd, I H, 'J(H/H)=9.0, 'J(P/
H)=9.1 Hz, 2-H), 2.84(m, I H , 4 - H ) , 3 , 1 4 ( d d , I H , 'J(H/H)=9.0, 'J(P/
H ) = 9 . 3 Hz, 8-H), 3.93 (d, I H , 'J(P/H)=8.3 Hz, 5-H), 4.74 (dd, 2 H ,
'J(H/H)=6.6, 'J(H/H)=2.7 Hz, allene-CH2), 5.14 (pseudo-q, I H, 4J(H/
H)= 'J(H/H)=6.6 Hz, allene-CH), 7.05-7.85 (m, 14H, arene-H); "CNMR (CDCII): h'=42.14, 42.27 (each d, 'J(C/H)= 175 Hz, C-2/C-8),
48.38 (d. 'J(P/C)= 100.0 Hz, C-l), 51.25 (dd, 'J(C/H)= 147.0, 'J(P/
C)=5.2 Hz, C - 5 ) , 65.8 (d, ]J(C/H)= 141.5 Hr, C-4), 77.3 (t, 'J(C/H)= 172
Hz, allene-CH2), 87.21 (d, 'J(C/H)= 172.0 Hz, allene-CH), 123.69132.57 (arene-C), 138.28 (s, C-6), 146.61 (d, 'J(P/C)=4.2 Hr, C-7), 207.56
( s , allene-C), 209.05 (s, C-3).
[Ni Ph(Ph2PCHCPhO) (Me3PCHz)I
Highly Active Ylide-Nickel Catalysts for the
Polymerization of Ethylene
By K . Alexander Ostoja Starzewski* and Josef Witte
Dedicated to Professor Row Huisgen on the occasion of
his 65th birthday
Ylides are characterized by extremely low first ionization energies and ylide C-atom I3C-NMR signals that are
shifted strongly upfield; this is due to a high-energy occupied MO, usually the H O M O that is strongly localized on
the ylide C atom."]
1 Ph2P'
Fig. 1. "P-NMR spectrum 01' the ylide complex 3 ([D,]benzene. room temperature). a) Broad-band 'H-decoupling; b) undecoupled.
The reaction of the stabilized ylide benzoylmethylenetriphenylphosphorane with Ni(o) in the presence of triphenylphosphane leads to the oligomerization catalyst 1,
which catalyzes the reaction of 6000 moles of ethylene per
mole of complex at 50 bar and 50"C.[21The ylide ligand is
practically no longer present in 1 . Complexes such as
Z,[3,41 in which the ylide ligand remains largely intact, are
of interest concerning their properties as polymerization
room temperature
cod: cyclooctadiene
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. 24 (198s) No. 7
3 is stable u p to ca. 90°C in toluene (NMR). Above
130°C, M a as well as characteristic fragments are observed
in the mass spectrum.[s1In the 'H-NMR spectrum of 3, the
resonances of the methylene protons are shifted downfield
by nickel complexation (6=0.65 in the complex; 6= - 0.78
in the free ylide[61).The double doublet structure (13.115.4
Hz)''] is explained by interaction of the two protons with
two different P atoms. The 'J(PH) coupling in the carbonyl-stabilized ligand is < 0.5 Hz; such small values are typical for free and complexed phosphanes.
The high-resolution room-temperature "C{ 'HJ-NMR
spectrum exhibits sixteen resonances-as expected for 3 which are partly split due to 31P-'3Ccouplings (Table 1).
The Ni-bound ylide C atom is the most strongly shielded C
atom of the molecule (6=7.2). Noticeable in this case, too,
is the double doublet splitting. By comparison with other
ylide-metal complexes,'lf.8' the smaller 3 1-Hz coupling can
be assigned to ' J . We ascribe the 64-Hz coupling to the
special trans arrangement of ylide and phosphane ligands
on square-planar-coordinated nickel. 'J(CH) (129 Hz, from
the undecoupled '%-NMR spectrum) supports a pyramidalization of the ylide C atom['d,f.81due to coordination to
the Ni atom. The position of the signals of 0- and p-C
atoms o n the Ni-bound phenyl group (Table 1) is charac-
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Table I . "C-NMR data [a-d] for 3. Coupling constants in Hz.
Intact ylide ligand
Ni-Ph group
125 4
( 120.3)
'J(PC),,u,,e [el
'J(PC),,, lel
(3 1)
PO chelate ligand
[a] l o - '
( 128.1)
in C6D6/TMS int. [b] 1 0 - I ~in CDZC12/TMSint., values in brackets. [c] Solvent signals overlap. [d] Not resolved. [el Square-planar coordinated nickel.
teristic for a phenyl group that is bound to an electron-rich
center (benzyl Grignard compound,[91 benzylidenephosphorane['O). C-a is still trigonal planar after complexation
according to 'J(CH) (163 Hz).
The double bond in 3 is strongly polarized. The C-a
atom, which bears a partial negative charge, exhibits a signal (6=78.9) that is shifted upfield relative to those of
"normal" sp2-hybridized C atoms (6= 128). The signal of
C-B is correspondingly strongly shifted downfield (6=
182.5). In comparison, the values for benzoylmethylenetriphenylphosphorane are 6 = 50 and 185,
The ylide complex 3 catalyzes the oligomerization of
ethylene at 10 bar and 90°C with an activity of ca. 0.5 x lo5
moles of ethylene per mole of 3. The polyethylene so
formed has a higher molecular weight than that obtained
with 1. We have also synthesized the ylide complexes 4
and examined their ability to catalyze the polymerization
of ethylene. We have observed, among other things, the
marked effect of substituents on the activity of the catalyst.
The activity increases in changing the chelate ligand from
formyl to acetyl and finally to benzoyl (4a- c). The activity of the catalyst can also be influenced by variation of the
intact ylide ligand; this is shown by the complexes 4d-f,
whose activity increases with decreasing first ionization
energy of the ylide (ZE, of Me3PCH2=6.81, of
Ph3PCH2=6.62, of Me,PCHPh as a model for the ylide ligand in 4f = 6.19 ev). Accordingly, the metal-ylide bond
determines the positions of the highest occupied molecular
orbitals, which are metal-d- and metal-C-localized, and
thereby the catalyst's (re)activity.
[Ni Ph(Ph,PCHCHO)( Me3PCH2)]
[Ni Ph(Ph,PCHCMeO)(Me,PCH,)]
[N i Ph( Ph, PC HC M eO)(Ph PCH,)]
[ Ni Ph( Ph,PCHCMeO)(iPr,PCHPh)]
Experimental Procedure
3: Bis(cyclooctadiene)nickel(o) (13.75 g, 50 mmol) in ca. 250 mL of anhydrous N2-saturated toluene is mixed under inert gas with 19.02 g (50 mmol)
of benzoylmethylenetriphenylphosphoraneand 4.50 g (50 mmol) of trime-
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thylmethylenephosphorane. A dark yellowish brown solution is formed upon
intense stirring and is then heated for ca. 1 h at 40 to 60°C. After subsequent
Schlenk filtration, the solution is evaporated under vacuum to half its volume. Upon cooling to 0 to -20"C, an initial fraction of yellow crystals
forms, which is isolated by Schlenk filtration, washed with hexane, and dried
under vacuum. The filtrate is then treated similarly, affording the pure nickel-ylide complex in 90% yield already in the first three crystalline fractions.
Impure fractions can be purified by recrystallization, e.g., from toluendhexane. M.p.= 117- 120°C (decomp.). 'H-NMR (CD2C12, TMS int.): 6=0.65
(dd, 'J(PH)=13.1, 'J(PH)=5.4 Hz, 2H), 1.56 (d, 'J(PH)= 13.9 Hr, 9H), 4.93
(br., 'J(PH)<0.5 Hz, 1 H), 6.56-7.83 (m,20H).
Polymerization of ethylene with 4f as catalyst: 4f (2 mmol) in 250 mL of toluene is injected into an autoclave containing 4 L of toluene at 80°C under a
constant piessure of 10 bar of ethylene parallel to the consumption of ethylene (multipulse injection), air and water being excluded. After ca. l h, the
autoclave is allowed to cool down, the pressure released, and the solid polyethylene (PE) isolated. In the filtrate, (CZH& for n = 2 to ca. 20 can be identified by gas chromatography. The amount of oligomers is determined by solvent evaporation (rotary evaporator), the low-boiling fractions being ignored.
The polymer consists of monoolefins having over 90% terminal double bonds
and high linearity (ratio -CH3/-CH=CH2= 1 by IR spectroscopy). Total
yield: 1366 g (5% oligomers); catalyst activity: 24393 moles of ethylene converted per mole of nickel; m.p. of the P E = I16'C; intrinsic viscosity of the
PE in tetralin at 120°C: 0.11 dL/g.
Received: January 16, 1985;
revised: April 9, 1985 [Z 1136 IE]
German version: Angew. Chem. 97 (1985) 610
CAS registry numbers:
4f, 90569-21-4; Ph,PCHCPhO, 859-65-4; Me,PCH2, 14580-91-7; (C2H,), homopolymer, 9002-88-4: Ni(cod)2, 33221-58-8.
[I] a) K. A. Ostoja Starzewski, H. tom Dieck, K. D. Franz, F. Hohmann, J.
Organomet. Chem. 42 (1972) C 3 5 ; b) K. A. Ostoja Starzewski, H. tom
Dieck, H. Bock, J. Organomet. Chem. 65 (1974) 311; c) K. A. Ostoja
Starzewski, H. Bock, H. tom Dieck, Angew. Chem. 87(1975) 197; Angew.
Chem. Inf. Ed. Engl. 14 (1975) 173; d) K. A. Ostoja Starzewski, M. Feigel, J . Organomet. Chem. 93 (1975) C20; e) K. A. Ostoja Starzewski, W.
Richter, H. Schmidbaur, Chem. Ber. 109 (1976) 473; f) K. A. Ostoja Starzewski, H. tom Dieck, Phosphorus 6 (1976) 177; g) K. A. Ostoja Starzewski, H. Bock, J. A m . Chem. SOC.98 (1976) 8486; h) E. E. Astrup, A.
M. Bouzga, K. A. Ostoja Starzewski, J . Mol. Struct. 51 (1979) 51; i) K. A.
Ostoja Starzewski, H. tom Dieck, Inorg. Chem. 18 (1979) 3307; j j K. A.
Ostoja Starzewski, M . Feigel, 1. Rieser, Phosphorus Sulfur 18 (1983)
[2] a) W. Keim, F. H. Kowaldt, R. Goddard, C . Kriiger, Angew. Chem. 90
(1978) 493; Angew. Chem. I n t . Ed. Engl. 1711978) 466; b) cf. W. Keim,
A. Behr, B. Limbacker, C. Kriiger, ibid. 95 (1983) 505 and 22 (1983) 503;
Angew. Chem. Suppl. 1983, 655.
[ 3 ] H. Schmidbaur, Angew. Chem. 95 (1983) 980; Angew. Chem. Inr. Ed.
Engl. 22 (1983) 907.
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Angew. Chem. Int. Ed. Engl. 24 (1985) No. 7
[4] W. C . Kaska, Coord. Chem. Reu. 48 (1983) I : see [la, f, i].
151 For "Ni: m / z 528 ( M " ) , 438 [Ni(Ph,PCHCPhO)O], 91 [Me,PCH,.H'],
77 [Cc>H?].
[6] H. Schmidbaur, W. Buchner, D. Scheutzow, Chem. Ber. 106 (1973)
[7] The PH coupling constants of the trimethylmethylenephosphorane ligands in 3 have the same sign according to selective homodecoupling
experiments. Their values, - 13.2 (P-CH3) and - 13.1 Hz (P-CH2), are
characteristic for a tetracoordinated phosphorus that is bonded to an approximately sp'-hybridized carbon atom.
[XI a) F. Heidenreich, A. Mollbach, G. Wilke, H. Dreeskamp, E. G. Hoffmann, G. Schroth, K. Seevogel, W. Stempfle, Isr. J . Chem. 10 (1972)
293: b) K. Hildenhrand, H. Dreeskamp, Z. Narurforsch. B28 (1973)
[9] D. Leihfritz, B. 0. Wagner, J. D. Roberts, Juslus Liebigs Ann. Churn. 763
(1972) 173.
(101 a) G. Fronza, P. Bravo, C. Ticozzi, J . Orgnnomer. Chem. 157 (1978) 299;
Freeman, E. E. Schweirer, J . A m .
b) T. A. Albright, M. D. Gordon, W. .I.
Chern. SOC.98 (1976) 6249.
~(qs-CsMes)CrO~l~A Dinuclear 0x0-Complex of Chromium(v)**
By Max Herberhold. * Walter Krernnitz, Abbas Razavi,
H . Schollhorn, and UlfThewalt*
The photoinduced oxidation of [Cp*Re(CO),] to
[Cp*Re03] 8[1-41
has demonstrated that cyclopentadienyl
ligands (q5-C5H, (Cp), q5-C5Me5(Cp*)) can tolerate both
low as well as high oxidation states of a metal. Oxygen attack ought to be favored if the metal in the low oxidation
state bears strong acceptor ligands. We have therefore investigated the oxidation of the nitrosyl complexes l a - c
with oxygen.
On stirring an oxygen-saturated solution of l a in toluene (without irradiation), a red dinuclear complex 2[" is
slowly formed, the structure of which has been elucidated
by X-ray crystallography (Fig. 1). In the complex 2,
chromium does not attain its highest possible oxidation
number, + 6; nevertheless, the formal oxidation state of
+ 5 is two oxidation states higher than in the antiferromagnetic tetranuclear pseudocubane cluster [CpCrO]4,[6-81prepared by mild oxidation of CrCp, in organic solvent^[^.^'
and likewise characterized by a n X-ray structure analys~s.[~'
In contrast to l a , the molybdenum complex l b is oxidized by oxygen to a yellow dinuclear complex 3,l5I
which, according to its I R spectrum (v(Mo=Oj 908 and
879 cm 'j, contains two cis-oriented terminal 0x0-ligands
per metal atom, i.e. the characteristic unit [Mo205]'+ with
molybdenum in the oxidation state +6. N o simple oxocomplex has been isolated from l c under comparable conditions.
Table I contains characteristic data of the new oxo-complexes 2 and 3 and of some reference compounds. 2 and 3
are diamagnetic. In the I3C-NMR spectrum, the signal of
the Cp* ring atoms is shifted by A&= 15 pprn downfield as
a result of the oxidation of the nitrosyl complexes l a and
b ; the methyl groups, however, are barely influenced. In
the IR spectrum, the very strong absorptions of the terminal 0x0-ligands appear in the region 850-950 cm I .
[Cp"M(CO)zNO] 1; a: M = C r ; b: M = Mo; c : M = W
[ Cp" R e 0 3 ]
Dinuclear 0x0-complexes of chromium(v) were hitherto
unknown. On the other hand, some 0x0-complexes have
been isolated in the oxidation of cyclopentadienylmolybdenum compounds;[91these include, inter alia, the brown
molybdenum(v) complex 4 analogous to 2,[9.'01and the
bright-yellow molybdenum(vr) complex 5 analogous to
3[91(Table 1).
An X-ray structure analysis["] of 2 reveals a centrosymmetric molecule with a planar C r 2 0 zfour-membered ring,
the chromium atoms of which have a distorted tetrahedral
environment (Fig. 1). The two Cp*-rings and the two terminal 0x0-ligands are each arranged trans to each other. In
contrast, both in the structurally similar complex 6[I2l as
well as in 4""' the five-membered rings are in the cis posi-
[*I Prof. Dr. M. Herherhold, W. Kremnitz
Laboratorium fur Anorganische Chemie der Universitat
Universitalsstrasse 30, D-8580 Bayreuth (FRG)
Prof. I h . U. Thewalt, Dr. A. Razavi ['I, H. Schollhorn
Sektion fur Rontgen- und Elektronenbeugung der Universitat
Oberer Eselsberg, D-7900 Ulm (FRG)
DAAD (Deutscher Akademischer Austauschdienst) Scholar, 1984. Present address: Sharif, University of Technology, Teheran (Iran).
This work was supported by the Deutsche Forschungsgemeinschaft and
the Fonds der Chemischen lndustrie.
A n y e w Chum. Inr. Ed. Engl. 24 11985) No. 7
Fig. 1. Molecular structure of 2 in the crystal. Selected bond lengths [pm] and
angles ["I: Cr-Cr* 250.5(1), Cr-Ol 181.7(4), Cr-01* l81.3(4), Cr-02
159.4(3), Cr-Z
193.1(6), 01-Cr-01*
92.7(2), 01-Cr-02
107.3(2), Cr-01-Cr* 87.3(2). Z=center of the five-membered
ring. Atoms marked with a n asterisk are centrosymmetrically related to the
corresponding unmarked atom.
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nickell, activ, ethylene, ylide, catalyst, highly, polymerization
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