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Ethene polymerization by binuclear nickel—ylide complexes
JOURNAL OF
MOLECULAR CATALYSIS Journal of Molecular Catalysis 88 ( 1994) 141-150
ELSEVIER
Ethene polymerization by binuclear nickel-ylide complexes K. Kurtev”, A. Tomov Higher Institute of Chemical Technology, Department of Basic Organic Synthesis, 8010 Bourgas, Bulgaria
(Received April 28, 1993; accepted October 29, 1993)
Abstract Binuclear nickel-ylide complexes based upon nine different bis-a-ketoylide ligands were studied as effective catalysts for ethene polymerization. The influence of the moiety linking the metal centers and the distance between them on the catalytic activity was discussed. Key words: binuclear complexes;
ethene; nickel; polymerization;
ylide complexes
1. Introduction The synthesis of nickel-ylide P,O-chelate complexes and their application as catalysts for linear ethene oligomerization in SHOP-process has been reported by Keim et al. [ l-31. On the other hand it has been shown by Beach and Harrison [ 4-61, that the introduction of some functional groups, such as S03M (M = Na, K, NH,) as substituents in the chelate rings of the nickel-ylide complexes, increases their catalytic activity. Later Klabunde and Ittel [ 7,8] reported that these complexes in the presence of phosphine scavengers polymerized ethene in polar or non-polar solvents to linear polyethylene. Ostoja-Starzewski et al. have reported the synthesis and application of the mononuclear bis(ylide)nickel complexes as effective catalysts for ethene polymerization [ 9,101. It is interesting that these catalyst precursors contain two types of ylide ligands: an a-ketoylide and a non-stabilized ylide. Polymer bonded nickel-ylide catalysts are also described in the literature [ 11,121. Their active centers however are located at long distances from each other, which leads to relatively slight electronic and steric interactions between them. * Corresponding
author. Fax. ( + 359-56)686141.
0304-5102/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSD10304-5 102( 93)E0274-K
142
K. Kurtev, A. Tomov/Journal
of Molecular Catalysis 88 (1994) 141-150
In recent years, many more efforts have been made to investigate compounds whose metal atoms are not directly linked by metal-metal bonds, but are held at a close distance with the help of an appropriate ligand system [ 131. We have recently established that the introduction of a second nickel-ylide group into the nickel ylide complexes makes them much more active catalysts for ethene polymerization. Their activity depends on the type of moiety linking the active centers, as well as on the distance between them. In the present paper we discuss the behavior of some binuclear nickel-ylide complexes and their use as effective catalysts for ethene polymerization.
2. Experimental All reactions were carried out under dry argon, using standard Schlenk techniques. Bis( 1,5cyclooctadiene)nickel(O) was prepared by the method of Otsuka and Rossi [ 141. Bis-a-ketoylides were prepared according to [ 151. ‘H NMR-spectra were recorded at 80 MHz on a Tesla BS 587 A or at 270 MHz on a JEOL 270 MHz IT-NMR model spectrometer, using TMS as an internal standard. IRspectra were measured on a Specord M80 spectrophotometer, using KBr discs. FI’-IR spectra were recorded as KBr discs on a Perkin-Elmer 1700 FT-IR spectrophotometer. UV spectra were measured on a Specord UV-VIS spectrophotometer. The elemental analysis for C and H were carried out on a Carlo Erba Elemental analyzer MOD 1104 (using helium as the carrier gas). The nickel content in the complexes was determined by method described in the literature [ 161.
2. I. Synthesis of complexes 1 and 2 To a suspension of 5 mm01 of the corresponding ylide in 100 ml toluene, which contained 10 mm01 of triphenylphosphine, were added 10 mm01 of bis( 1,5-cyclooctadiene)nickel( 0). The reaction mixture was stirred 24 h at room temperature, then for 2 h at 5O”C, and 50 ml hexane were added. The solid was filtered off, washed with 2 X 20 ml toluene/hexane mixture (2: 1) and dried at 0.1 torr for 6 h.
2. I. 1. Analysis 2.1.1.1. Complex 1.Elemental analysis for Cs2H,&,0,P,, calcd. (found), %: C 74.33 (73.41); H 5.03 (4.79); Ni 8.86 (8.33). IR-spectrum (KBr), cm-‘: 1556~ (~c,c~“o ccc-p) ; 152% ( bd; 1428~~ ( vC(Ar)_P + ); 1473~s; 1372s (~c,~); 128Ow; 853s; 69Ovs740s ( &-C(Arj_n). ‘H-NMR: poor solubility. UV-spectrum (methanol), A,,,( lge), nm: 226(4.34); 253(3.99); 275(3.82); 340(3.83). 2.1.1.2. Complex 2. Elemental analysis for C94H74Ni202P4r calcd. (found), %: C 76.43 (76.82); H 5.06 (4.88) ; Ni 7.95 (7.37). IR-spectrum (KBr), cm- ‘: 1552~ ( vc-c in o_ 1338s ( v,--p); 1253m; 836~; 68Ovs-733s C,C-P) ; 1476s ( Q=O) ; 1425~s ( hZ(Ar)-p + );
K. Kurtev, A. Tomov/Joumal
ofMolecular Catalysis 88 (1994) 141-150
). ‘H-NMR: poor solubility. UV-spectrum (%(A+H 222(4.31); 265(4.19); 326(4.04).
(methanol),
h,,(lge),
143
nm:
2.2. Synthesis of complexes 3-8 A solution, cooled to 0°C of 5 mm01 of the corresponding bis-cu-ketoylide and 10 mm01 of triphenylphosphine in 200 ml toluene was added to 10 mm01 bis( l,Scyclooctadiene)nickel( 0). The resulting brown solution was stirred at room temperature for 24 h, heated to 50°C for 1 h and evaporated at 0.1 torr. The residue was dissolved in a small portion of toluene ( 20-40 ml) and 100 ml of hexane were added, to give a solid which was filtered off, washed with hexane (2 X 20 ml) and dried at 0.1 ton-. Recrystallization from toluene/hexane gave dark yellow crystalline solid (red solids for complexes 7 and 8 were obtained). 2.2.1. Analysis 2.2.1.1. Complex 3. Elemental analysis for C9SH86Ni202P4,calcd. (found), %: C 76.19
(75.34); H 5.74 (6.03); Ni 7.76 (7.28). IR-spectrum (KBr), cm-‘: 1564~ ~~~~~~~~ c_c_p); 1515s (v,,o); 1436~s (v~(,,_v,(,,,+); 1335m ( vocp); 1282~; 692vs-742s ); 828~. ‘H-NMR (C,D,), Gppm: 1.19 (m, 8H, 4x(-C&)); 1.88 (m, 4H, (&C(Ar)-H 2XCH,-CH,-C(O)-); 2.50 (t, 4H, 2XC&-C(O)-); 6.53 (m 6H, metu- andpara-H from 2 X C6H5-Ni) ; 6.98 (br.s 44H, meta- and par&H from 10 X CsHS-P; H from 2 X C,H,-C=P; ortho-H from 2 X &I-I,-Ni) ; 7.63 (m, 20H, ortho-H from 10 X C,H,-P) . UV-spectrum (methanol), A,,( lge), nm: 222 (4.72) ; 267 (4.09). 2.2.1.2. Complex 4. Elemental analysis for CBBH,,Ni,O,P,, calcd. (found), %: C 71.55 (71.11)H5.51 (6.24)Ni7.95(8.30).IR-spectrum(KBr),cm~1:2953w(v,H,);2922m ( vCH2); 1680~~ ( vC(0j-0); 1584~ ( VC-C in _=C_p); 1550s ( ~o,o) ; 1429~s ( ~c(h)-p+ ); 1628s ( vccp) ; 8 low; 693vs-747s ( 6C(&)_n) . ‘H-NMR: not determined. W-spectrum (methanol), h_(lge), nm: 226 (4.12); 258 (3.88). 2.2.1.3. Complex 5. Elemental analysis for Cs4H74Ni206P4,calcd. (found), %: C 70.99
(70.43); H 5.26 (5.04); Ni 8.26 (8.41). IR-spectrum (KBr), cm-‘: 2940m (vCH3); 2920 (+H,); 1660~s (I+~,_,); 1557m (r&o); 1460~s; 1429~s (v,-(,,,+); 1283m (v,,,); 1073vs (v,,, ) ; 842~; 69Ovs-750s ( &,,,_,) . ‘H-NMR (C,D,), Gppm: 1.86 (m, 4H, 2X (-CHZ-)); 3.10 (t, 4H, 2 X-CH,(O)-): 3.26 (s, 6H, 2XCH,); 6.49 (m, 34H, metuand paru-H from 2 X CsHS-Ni) ; 7.24 (m, 34H, metu- and paru-H from 10 x C,H,-Ni; ortho-H from 2 X C6H5-Ni) ; 7.43-7.70 (m, 20H, ortho-H from 10 X C,H,-P) . UV-spectrum (methanol), h,,,(lge), nm; 227(4.18); 258(3.99). 2.2.1.4. Complex 6. Elemental analysis for Cq5HY8NiZ02P4, calcd. (found), %: C 76.41 (75.80); H 5.28 (5.09); Ni 7.86 (7.21). IR-spectrum (KBr), cm-‘: 3046m (v,,,,,_ n+ v&H); 1626~ (v,_,); 1560~ (Yc=c in-_-c-p) ; 1509~9sh.; 1489~~ ( ~c,o,,); 1477~~ ( v,,,,~); 1457s, sh.; 1429~s (+(Ar)_p+); 1379m ( v~_~) ; 1260~; 840-853~; 693vs-740s ). ‘H-NMR (C,D,), S, ppm: 1.30 (m, lH, Hsynre,.c_c); 2.81 (d, lH, Ji.r_H=8 (&C(Ar)-H
144
K. Kurtev, A. Tomov /Journal
of Molecular Catalysis 88 (1994) 141-150
HZ, Han,); 2.75 (m, lH, bridgehead H); 3.13 (m, lH, bridgehead H); 3.88 (d, lH, JH_ H=6 Hz, Hendo); 4.52 (d, lH, .&=4 Hz, H,,,); 6.08 (m, 2H, alkene H); 6.57 (m, 6H, metu- and puru-H from 2 X C6H,-Ni) ; 7.13 (m, 40H, metu- and puru-H from 10 X C,H,P; H from 2 X C,H,-C=P); 7.35 (m, 4H, ortho-H from 2 X C6H,-Ni) ; 7.63-7.80 (m, 20H, ortho-H from 10 X C,H,P) . UV-spectrum (methanol), A,,(lge), nm: 222(4.39); 266(3.84); 273(3.81). 2.2.1.5. Complex 7. Elemental analysis for C9sH,,FeNi20,P,, calcd. (found), %: C 74.26 (73.75); H 4.97 (4.31): Ni 7.41 (7.72). IR-spectrum (KBr), cm-‘: 1560~ (vc,eino_ 1253m; 691vs-740s ( &-C(Arj_ c,c_p); 1477vs (r&J; 1431vs (Irc(*,)-p+ ); 1295s (vc-,); u); 510s ( +e+J. ‘H-NMR ( C6Ds), Gppm: 4.08 (s, 4H, H,,Hk ,H,,H$ from 2 X Cp); 4.58 (s, 4H, H1,H{ ,H4,Hi from 2 X Cp) ; 6.43 (m, 6H, metu- and puru-H from 2 X C,H,-Ni); 7.05-7.17 (m, 44H, mefu- and puru-H from 10 X C,H,P; ortho-H from 2 X C,H,-Ni; H from 2XC,H,-C=P); 7.53-7.81 (m, 20H, ortho-H from 10X C,H,-P). UV-spectrum (methanol), h,,,(lge), nm: 223(4.80); 264(4.47); 349(4.05). 2.2.1.6. Complex 8. Elemental analysis for CsaH,,FeNi,O,P,, calcd. (found), %: C 72.35 (71.67);H5.12(4.88);Ni8.04(7.59).1R-spectrum(KBr),cm~‘:2953w(v,,,);1581w ); 1291m (vc=,); 1253~; 813~; 687vs( r&c in o-ccc-P); 14%~ ( +=o) ; 142% ( %(A+H 740s (&(A+H); 513s ( VFe-cp) . ‘H-NMR (C,D,), @pm; 1.43 (s, 6H, 2 X CH,) ; 4.02 (s, 4H, H,,H&,H,,H; from 2XCp); 4.44 (s, 4H, H1,H;, H4, Hi from 2XCp); 6.41 (m, 6H, metu- and puru-H from 2 X&H,-Ni); 7.00-7.15 (m, 34H, metu- and puru-H from 10 X C,H,--P; ortho-H from 2 X C,H,-Ni) ; 7.38-7.68 (m, 20H, ortho-H from 10 X C6H,P). UV-spectrum (methanol), h,,,(lge), nm: 222(4.45); 266(4.23); 334(4.01). 2.3. Synthesis of complex 9. To a suspension of 4.43 g (5 mmol) of disodium{ benzene-l ,6bis [2-0x0-1-( triphenylphosphoranylidene)ethylsulfonate] } in 100 ml toluene which contained 2.63 g (10 mmol) triphenylphosphine were added 2.72 g (10 mmol) bis( 1,5-cyclooctadiene)nickel(O). The reaction mixture was stirred 18 h at room temperature, 10 min at 50°C and after cooling, 20 ml hexane were added. The solid was filtered off, washed with toluene (2 X 20) ml and dried at 0.1 torr for 8 h. Yield: 4.97 g (65%). 2.3.1. Analysis Elemental analysis for Cs2HtiNa,Ni,0sP,S,, calcd. (found), %: C 64.41 (64.85); H 4.23 (4.81); Ni 7.68 (7.95). FT-IR-spectrum (KBr), cm-‘: 1631s ( vsol); 1576~ (~c,~~,o_c=~_~); 1484~s (vc=o); 1438~s (vc(,,,,); 1337s (v,=,); 815~; 693vs-749s ). ‘H-NMR (270 MHz, d,-DMSO), Gppm: 7.50 (v br.s, wO= 243 Hz). UV(&(A+H spectrum (methanol), h,,,(lge), nm: 222(4.75); 255(4.37); 272(4.28); 328(3.99). 2.4. General procedure for ethene polymerization
by the bin&ear
nickel-ylide
complexes
Etbene polymerizations were carried out in a 250 ml thermostated batch stainless steel reactor (Buchi Laborautoclave BEP 280), supplied with a mechanical stirrer, a speed controller and a digital indicator system for temperature, pressure and speed.
K. Kurtev, A. Tomov / Journal of Molecular Catalysis 88 (I 994) 141-150
145
Before every experiment the reactor was cleaned and dried under vacuum at 100°C for 1 h. After cooling it was filled with 100 ml of solvent (purified in the usual way, distilled over metallic sodium, and stored under argon). The catalyst solution, prepared by dissolution of a nickel complex ( 10-150 mg) and the appropriate phosphine scavenger (50-200 mg), was transferred to the reactor. The reactor content was briefly evacuated and then charged with ethene (ethene 99.95%, from the Petrochemical Works, Bourgas, Bulgaria, without further purification) at 3 atm lower, than the reaction pressure. Then the reaction mixture was stirred and heated to the desired temperature. A constant ethene pressure was maintained by a pressure regulator and a pressure transmitter valve (Brooks Instrument B.V.) .
3. Results and discussion 3.1. Catalyst synthesis All binuclear nickel-ylide complexes based upon bis-a-ketoylide ligands, such as those indicated by l-9, were prepared by oxidative addition of phosphorus(V) bis-cu-ketoylides [ 151 to Ni(COD)* in the presence of PPh,, according to Scheme 1. It was found that the synthesis of binuclear nickel-ylide complexes is possible only when the bis-a-ketoylide groups are not linked to vicinal carbon atoms and are not located in one and the same plane. Otherwise decomposition of Ni( COD), occurs. For example, all our attempts to prepare binuclear nickel-ylide complexes from bis- 1,2- [ I-phenyl- 1- ( triphenylphosphoranylideno) acetyl] benzene failed, probably because of the specific O-O coordination of the ylide to the nickel atom. 3.2. Ethene polymerization It is well known that nickel P-O chelate complexes are active catalysts for ethene oligomerization to higher a-alkenes [ 17,181. They can be readily converted into catalysts for ethene polymerization by applying phosphine scavengers [ 81. Some of the binuclear nickel-ylide complexes, for example 3,4 and 6 oligomerize ethene but the product linearity is lower those obtained by the mononuclear ones. Complexes 1,2 and 9 polymerize ethene even without phosphine scavengers thus producing low molecular weight polyethylene. Complexes 7 and 8 are catalytically inactive for ethene polymerization in the absence of catalyst promoters. All the binuclear nickel-ylide complexes (l-9) polymerize ethene in presence of phosphine scavengers to give polyethylene. As effective promoters (COD)$h&l,, ( C2H,),Rh2C1,, Ni( COD)2 and PdCl*( CH,CN), were used. The results from a variety of polymerization reactions are listed in Table 1. Runs 1,3,4,6, 17 and 19 show the influence of the type of phosphine scavenger used on the catalyst productivity. For the majority of the complexes the most effective promoter was Ni( COD),. For catalyst 5, only (C&)&h& binds phosphines more strongly than Ni( COD),. The effectiveness of the phosphine scavengers as catalyst promoters changes in the following sequence:
146
K. Kurtev, A. Tomov /Journal
2Ni
I COD
I2
of Molecular Catalysis 88 (1994) 141-150
+ PPh3
Catalyst
R
RI
Yield
NO
%
l/L - C6HL
H
50
1.3 - C6HL
Ph
5L
I CH2je-
Ph
70
- lCH21e-
C02Me
52
-iCH211-
C02Me
51
-
6 H
+ l,l’-
1y5 - CsH&Fe
l-l’-
(%5 - CsH&
Scheme 1. Preparation
> (C,H,)&h,C12
72
Ph
69
Me
64
SO,Na
65
‘H
l.L-
Ni(COD)2
Ph
Fe
CsHb
of binuclear nickel-ylide
> (COD),Rh,Cl,
complexes.
>PdCl,(CH,CN)2
Runs 12, 15 represent the influence of the distance between both the active centers on the catalyst productivity. Decreasing the distance between them leads to a significant increase of the catalyst productivity, which may be attributed to the mutual influence of the active centers - indirect electronic interactions and stronger spatial repulsion. Runs 5 and 3 1 exhibit the influence of the second substituent R, in the chelate rings on the catalytic activity. Electron withdrawing groups significantly increase the polymerization activity of the catalysts, and vice versa - the rich of electrons ferrocene ring decrease it remarkably (runs 27 and 30). Runs 11 and 22 represent the influence of the distance as well as the type of the moiety, linking the active centers on the catalytic activity. The higher activity of catalyst 6, compared whit that of 3 is apparently due to the shorter distance between the active centers and the higher steric parameter of the norbomene ring, which restricts the free rotation of the active centers and the substrate molecules “know how to find them”.
K. Kurtev, A. Tomov/Journal Table 1 Etbene polymerization
by binuclear nickel-ylide
catalysts
Run No.
Catalyst No.
Phosphine scavenger”
Solvent
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
1 1 1 1 1 1 2 2 2 3 3 4 4 4 5 5 5 5 5 6 6 6 6 6 6 6 7 7 7 8 9 9
Rh-1 Rh-1 Rh-2 Ni Ni Ni Rh-1 Rh-2 Ni Rh-1 Ni Rh- 1 Ni Ni Rh-I Rh-1 Pd Ni Rh-1 Rh-1 Pd Ni Ni Ni Ni Ni Ni Ni Rh-1 Ni Ni Ni
toluene toluene toluene toluene toluene methanol toluene toluene toluene
a.Rh-I is Rha-@Zl,(C,H,),, b 88% methanol.
147
ofMolecular Catalysis 88 (1994) 141-150
toluene toluene toluene toluene toluene toluene toluene toluene methanol toluene toluene toluene toluene toluene methanol methanoP toluene toluene toluene toluene toluene toluene
Rh-2 is Rh,ip-Cl,(COD),,
P
T
Productivity
(atm)
(“C)
(kg PE/S Ni*h)
16.6 25.5 26.0 15.5 4.2 17.5 25.5 24.5 5.5 24.5 25.0 17.0 17.0 25.0 17.0 26.0 17.5 17.0 21.5 15.0 25.0 25.0 5.4 5.0 25.0 14.5 25.0 5.6 25.5 25.0 4.0 17.0
50 50 50 48 50 48 50 50 50 50 50 48 49 50 50 50 50 46 51 44 50 48 48 55 50 50 JO 50 50 51 55 55
2.1 3.9 2.4 4.5 2.7 1.2 1.1 0.6 1.0 0.3 0.9 0.7 1.0 1.9 8.5 11.9 2.4 5.5 0.3 1.9 1.1 13.8 7.0 7.8 8.6 1.5 0.8 0.2 0.2 0.2 35.2 87.5
Pd is PdCla(CH,CN)a,
Ni is Ni(COD),.
In agreement with this proposal, the IR spectrum of complex 6 (2% solution in CHCl,) exhibited two shoulders on the absorption band for the carbonyl groups (Fig. 1). The double bond of the norbomene ring reveals absorption at 1626 cm-‘. When Ph,P was removed from the coordination sphere of the metal ~c-c absorption band was shifted to 1602 cm- ‘. It was assumed to be a result of an intramolecular coordination of the double bond to the nickel atom from the endo-chelate ring, but all our attempts to gain a better insight into the impact of this coordination on the catalyst activity has failed so far. The ability of complex 6 to polymerize ethene in the presence of methanol and watermethanol mixtures is remarkable (runs 2526).
148
K. Kurtev, A. Tomov / Journal
ofMolecular Catalysis 88 (1994) 141-150
1513 cm-’
IL93 cm-’
Y /\
ekzo
- > C=O group
J
lL76cm-’
I
endo
- > C = 0 group
Fig. 1. Carbonyl stretching vibrations band for 6.
Ph
Ph
o\Ni,pPh3 H
I
x
/
o\Ni,PPh3 I
‘Ph
Na03S
IO Productivity
‘Ph
‘Ph 11
= 0.24 kg PE/g
Fig. 2. Productivity
p/
x
ph’
Ph/p\Ph
Ni.h
Productivity
of the mononuclear
= 23.20
kg PE/g
Ni.h
catalysts 10 and 11.
Runs 3 1 and 32 showed the significance of the introduction of a second metal center into the complexes under question on the catalytic activity. To compare the catalytic activities of the binuclear complexes with the mononuclear ones, we have used the experimental data for complexes 10and 11,reported by U. Klabunde et al. [ 81. Runs 5 and 3 1 displayed that the binuclear nickel-ylide complexes exhibited higher catalytic activity than the corresponding mononuclear ones. Runs 2,7 and 5,9 showed the influence of the conjugation between the metal centers on the activity of the catalysts. The presence of a conjugated system, comprising two active centers and the 1,Csubstituted benzene ring was confirmed using UV-spectroscopy. For nm. We suggest that the complex 1 A,,, is at 340 nm, while for complex 2 A,,,=326 higher activity of catalyst 9 is due to the conjugation between the active centers as well as to the presence of the electron withdrawing S03Na substituents in both the chelate rings.
3.3. Polyethylene properties
The properties of the polyethylene produced by the binuclear nickel-ylide complexes in the presence of phosphine scavengers depend strongly on the type of the moiety linking the active centers (Table 2). The crystallinity (DSC determined) of the polyethylene obtained was from 60% to 90% and the density between 0.935 and 0.975.
K. Kurtev, A. Tomov/Journal Table 2 Properties of the polyethylene scavenger
of Molecular
prepared by binuclear nickel-ylide
Catalyst No.
T
P
Productivity
(“C)
(atm)
(kg PE/g Ni*h)
1 4 5” 6 9 9
48 49 50 66 64 60
5.6 17.5 26.5 4.2 4.0 17.0
2.79 2.13 11.88 7.86 35.16 87.50
a Phosphine scavenger:
149
Catalysis 88 (1994) 141-150
catalyst in presence of Ni (COD) 2 as a phosphine
M”
M,
&I%
9000 4300 3 100 5 700 7 800 9900
271000 9700 6 200 40 400 98 400 164300
30.1 2.3 2.0 7.1 12.6 16.6
Rhz-~-C1,(C&),.
4. Conclusion The introduction of a second nickel-ylide group into the nickel P-O chelate complexes, in the presence of phosphine scavengers yields high activity ethene polymerization catalysts resistant to deactivation by oxygenated species. The existence of conjugation and shortening the distance between the active centers makes these complexes much more active ethene polymerization catalysts than the mononuclear ones.
5. Acknowledgement The support of the Bulgarian tude.
National Science Foundation
is acknowledged
with grati-
6. References [I] W. Keim, F.H. Kowaldt, R. Goddard, C. Krtiger, Angew. Chem., 90 ( 1978) 493. [2] W. Keim, A. Behr, B. Gruber, B. Hoffmann, F.H. Kowaldt, U. Kurschner, B. Limbacker, F.P. Sisting, Organometallics, 5 ( 1986) 2356. [3] W. Keim, New J. Chem., 11 ( 1987) 531. [4] D. Beach, J. Harrison, US Pat. 4,293,727 (1981). [5] D. Beach, J. Harrison, US Pat. 4,310,716 (1982). [6] D. Beach, J. Harrison, US Pat. 4,711,969 (1987). [7] U. Klabunde, US Pats. 4,698,403 and 4,716,205 ( 1987). [ 81 U. Klabunde, R. Mulhaupt, T. Herskovitz, A.H. Janowicz, J. Calabrese, S.D. Ittel, J. Polym. Sci., Part A: Polym. Chem., 25 (1987) 1989. [9] K.A. Ostoja-Starzewski, J. Witte, Angew. Chem., 97 ( 1985) 610. [lo] K.A. Ostoja-Starzewski, J. Witte, Angew. Chem., 99 ( 1987) 76. [ 1 l] G. Braca, A. Ricci, G. Sbrana, M. Brunelli, A. Giusti, G. Bertolini, A.M. Raspolli Galletti, Eur. Pat. 0 393 751 A2 (1990). [ 121 G. Braca, Chim. Oggi., ( 1988) 23; 11. [ 131 A. Bader, E. Linder, Coord. Chem. Rev., 27 ( 1991) 108.
150 [ 141 [ 151 [ 161 [ 171 [ 181
K. Kurtev, A. Tomov / Journal of Molecular Catalysis 88 (1994) 141-150 S. Otsuka, M. Rossi, J. Chem. SOL, (1968) 2630. A. Tomov, K. Kurtev, Bulg. Chem. Commun., 25 (1992) 436. M. Toumaire, Ann. Chim. Anal., 27 (1945) 184. W. Keim, Stud. Surf. Sci. Catal., 25 (1986) 201. W. Keim, J. Mol. Catal., 52 (1989) 19.
MOLECULAR CATALYSIS Journal of Molecular Catalysis 88 ( 1994) 141-150
ELSEVIER
Ethene polymerization by binuclear nickel-ylide complexes K. Kurtev”, A. Tomov Higher Institute of Chemical Technology, Department of Basic Organic Synthesis, 8010 Bourgas, Bulgaria
(Received April 28, 1993; accepted October 29, 1993)
Abstract Binuclear nickel-ylide complexes based upon nine different bis-a-ketoylide ligands were studied as effective catalysts for ethene polymerization. The influence of the moiety linking the metal centers and the distance between them on the catalytic activity was discussed. Key words: binuclear complexes;
ethene; nickel; polymerization;
ylide complexes
1. Introduction The synthesis of nickel-ylide P,O-chelate complexes and their application as catalysts for linear ethene oligomerization in SHOP-process has been reported by Keim et al. [ l-31. On the other hand it has been shown by Beach and Harrison [ 4-61, that the introduction of some functional groups, such as S03M (M = Na, K, NH,) as substituents in the chelate rings of the nickel-ylide complexes, increases their catalytic activity. Later Klabunde and Ittel [ 7,8] reported that these complexes in the presence of phosphine scavengers polymerized ethene in polar or non-polar solvents to linear polyethylene. Ostoja-Starzewski et al. have reported the synthesis and application of the mononuclear bis(ylide)nickel complexes as effective catalysts for ethene polymerization [ 9,101. It is interesting that these catalyst precursors contain two types of ylide ligands: an a-ketoylide and a non-stabilized ylide. Polymer bonded nickel-ylide catalysts are also described in the literature [ 11,121. Their active centers however are located at long distances from each other, which leads to relatively slight electronic and steric interactions between them. * Corresponding
author. Fax. ( + 359-56)686141.
0304-5102/94/$07.00 0 1994 Elsevier Science B.V. All rights reserved SSD10304-5 102( 93)E0274-K
142
K. Kurtev, A. Tomov/Journal
of Molecular Catalysis 88 (1994) 141-150
In recent years, many more efforts have been made to investigate compounds whose metal atoms are not directly linked by metal-metal bonds, but are held at a close distance with the help of an appropriate ligand system [ 131. We have recently established that the introduction of a second nickel-ylide group into the nickel ylide complexes makes them much more active catalysts for ethene polymerization. Their activity depends on the type of moiety linking the active centers, as well as on the distance between them. In the present paper we discuss the behavior of some binuclear nickel-ylide complexes and their use as effective catalysts for ethene polymerization.
2. Experimental All reactions were carried out under dry argon, using standard Schlenk techniques. Bis( 1,5cyclooctadiene)nickel(O) was prepared by the method of Otsuka and Rossi [ 141. Bis-a-ketoylides were prepared according to [ 151. ‘H NMR-spectra were recorded at 80 MHz on a Tesla BS 587 A or at 270 MHz on a JEOL 270 MHz IT-NMR model spectrometer, using TMS as an internal standard. IRspectra were measured on a Specord M80 spectrophotometer, using KBr discs. FI’-IR spectra were recorded as KBr discs on a Perkin-Elmer 1700 FT-IR spectrophotometer. UV spectra were measured on a Specord UV-VIS spectrophotometer. The elemental analysis for C and H were carried out on a Carlo Erba Elemental analyzer MOD 1104 (using helium as the carrier gas). The nickel content in the complexes was determined by method described in the literature [ 161.
2. I. Synthesis of complexes 1 and 2 To a suspension of 5 mm01 of the corresponding ylide in 100 ml toluene, which contained 10 mm01 of triphenylphosphine, were added 10 mm01 of bis( 1,5-cyclooctadiene)nickel( 0). The reaction mixture was stirred 24 h at room temperature, then for 2 h at 5O”C, and 50 ml hexane were added. The solid was filtered off, washed with 2 X 20 ml toluene/hexane mixture (2: 1) and dried at 0.1 torr for 6 h.
2. I. 1. Analysis 2.1.1.1. Complex 1.Elemental analysis for Cs2H,&,0,P,, calcd. (found), %: C 74.33 (73.41); H 5.03 (4.79); Ni 8.86 (8.33). IR-spectrum (KBr), cm-‘: 1556~ (~c,c~“o ccc-p) ; 152% ( bd; 1428~~ ( vC(Ar)_P + ); 1473~s; 1372s (~c,~); 128Ow; 853s; 69Ovs740s ( &-C(Arj_n). ‘H-NMR: poor solubility. UV-spectrum (methanol), A,,,( lge), nm: 226(4.34); 253(3.99); 275(3.82); 340(3.83). 2.1.1.2. Complex 2. Elemental analysis for C94H74Ni202P4r calcd. (found), %: C 76.43 (76.82); H 5.06 (4.88) ; Ni 7.95 (7.37). IR-spectrum (KBr), cm- ‘: 1552~ ( vc-c in o_ 1338s ( v,--p); 1253m; 836~; 68Ovs-733s C,C-P) ; 1476s ( Q=O) ; 1425~s ( hZ(Ar)-p + );
K. Kurtev, A. Tomov/Joumal
ofMolecular Catalysis 88 (1994) 141-150
). ‘H-NMR: poor solubility. UV-spectrum (%(A+H 222(4.31); 265(4.19); 326(4.04).
(methanol),
h,,(lge),
143
nm:
2.2. Synthesis of complexes 3-8 A solution, cooled to 0°C of 5 mm01 of the corresponding bis-cu-ketoylide and 10 mm01 of triphenylphosphine in 200 ml toluene was added to 10 mm01 bis( l,Scyclooctadiene)nickel( 0). The resulting brown solution was stirred at room temperature for 24 h, heated to 50°C for 1 h and evaporated at 0.1 torr. The residue was dissolved in a small portion of toluene ( 20-40 ml) and 100 ml of hexane were added, to give a solid which was filtered off, washed with hexane (2 X 20 ml) and dried at 0.1 ton-. Recrystallization from toluene/hexane gave dark yellow crystalline solid (red solids for complexes 7 and 8 were obtained). 2.2.1. Analysis 2.2.1.1. Complex 3. Elemental analysis for C9SH86Ni202P4,calcd. (found), %: C 76.19
(75.34); H 5.74 (6.03); Ni 7.76 (7.28). IR-spectrum (KBr), cm-‘: 1564~ ~~~~~~~~ c_c_p); 1515s (v,,o); 1436~s (v~(,,_v,(,,,+); 1335m ( vocp); 1282~; 692vs-742s ); 828~. ‘H-NMR (C,D,), Gppm: 1.19 (m, 8H, 4x(-C&)); 1.88 (m, 4H, (&C(Ar)-H 2XCH,-CH,-C(O)-); 2.50 (t, 4H, 2XC&-C(O)-); 6.53 (m 6H, metu- andpara-H from 2 X C6H5-Ni) ; 6.98 (br.s 44H, meta- and par&H from 10 X CsHS-P; H from 2 X C,H,-C=P; ortho-H from 2 X &I-I,-Ni) ; 7.63 (m, 20H, ortho-H from 10 X C,H,-P) . UV-spectrum (methanol), A,,( lge), nm: 222 (4.72) ; 267 (4.09). 2.2.1.2. Complex 4. Elemental analysis for CBBH,,Ni,O,P,, calcd. (found), %: C 71.55 (71.11)H5.51 (6.24)Ni7.95(8.30).IR-spectrum(KBr),cm~1:2953w(v,H,);2922m ( vCH2); 1680~~ ( vC(0j-0); 1584~ ( VC-C in _=C_p); 1550s ( ~o,o) ; 1429~s ( ~c(h)-p+ ); 1628s ( vccp) ; 8 low; 693vs-747s ( 6C(&)_n) . ‘H-NMR: not determined. W-spectrum (methanol), h_(lge), nm: 226 (4.12); 258 (3.88). 2.2.1.3. Complex 5. Elemental analysis for Cs4H74Ni206P4,calcd. (found), %: C 70.99
(70.43); H 5.26 (5.04); Ni 8.26 (8.41). IR-spectrum (KBr), cm-‘: 2940m (vCH3); 2920 (+H,); 1660~s (I+~,_,); 1557m (r&o); 1460~s; 1429~s (v,-(,,,+); 1283m (v,,,); 1073vs (v,,, ) ; 842~; 69Ovs-750s ( &,,,_,) . ‘H-NMR (C,D,), Gppm: 1.86 (m, 4H, 2X (-CHZ-)); 3.10 (t, 4H, 2 X-CH,(O)-): 3.26 (s, 6H, 2XCH,); 6.49 (m, 34H, metuand paru-H from 2 X CsHS-Ni) ; 7.24 (m, 34H, metu- and paru-H from 10 x C,H,-Ni; ortho-H from 2 X C6H5-Ni) ; 7.43-7.70 (m, 20H, ortho-H from 10 X C,H,-P) . UV-spectrum (methanol), h,,,(lge), nm; 227(4.18); 258(3.99). 2.2.1.4. Complex 6. Elemental analysis for Cq5HY8NiZ02P4, calcd. (found), %: C 76.41 (75.80); H 5.28 (5.09); Ni 7.86 (7.21). IR-spectrum (KBr), cm-‘: 3046m (v,,,,,_ n+ v&H); 1626~ (v,_,); 1560~ (Yc=c in-_-c-p) ; 1509~9sh.; 1489~~ ( ~c,o,,); 1477~~ ( v,,,,~); 1457s, sh.; 1429~s (+(Ar)_p+); 1379m ( v~_~) ; 1260~; 840-853~; 693vs-740s ). ‘H-NMR (C,D,), S, ppm: 1.30 (m, lH, Hsynre,.c_c); 2.81 (d, lH, Ji.r_H=8 (&C(Ar)-H
144
K. Kurtev, A. Tomov /Journal
of Molecular Catalysis 88 (1994) 141-150
HZ, Han,); 2.75 (m, lH, bridgehead H); 3.13 (m, lH, bridgehead H); 3.88 (d, lH, JH_ H=6 Hz, Hendo); 4.52 (d, lH, .&=4 Hz, H,,,); 6.08 (m, 2H, alkene H); 6.57 (m, 6H, metu- and puru-H from 2 X C6H,-Ni) ; 7.13 (m, 40H, metu- and puru-H from 10 X C,H,P; H from 2 X C,H,-C=P); 7.35 (m, 4H, ortho-H from 2 X C6H,-Ni) ; 7.63-7.80 (m, 20H, ortho-H from 10 X C,H,P) . UV-spectrum (methanol), A,,(lge), nm: 222(4.39); 266(3.84); 273(3.81). 2.2.1.5. Complex 7. Elemental analysis for C9sH,,FeNi20,P,, calcd. (found), %: C 74.26 (73.75); H 4.97 (4.31): Ni 7.41 (7.72). IR-spectrum (KBr), cm-‘: 1560~ (vc,eino_ 1253m; 691vs-740s ( &-C(Arj_ c,c_p); 1477vs (r&J; 1431vs (Irc(*,)-p+ ); 1295s (vc-,); u); 510s ( +e+J. ‘H-NMR ( C6Ds), Gppm: 4.08 (s, 4H, H,,Hk ,H,,H$ from 2 X Cp); 4.58 (s, 4H, H1,H{ ,H4,Hi from 2 X Cp) ; 6.43 (m, 6H, metu- and puru-H from 2 X C,H,-Ni); 7.05-7.17 (m, 44H, mefu- and puru-H from 10 X C,H,P; ortho-H from 2 X C,H,-Ni; H from 2XC,H,-C=P); 7.53-7.81 (m, 20H, ortho-H from 10X C,H,-P). UV-spectrum (methanol), h,,,(lge), nm: 223(4.80); 264(4.47); 349(4.05). 2.2.1.6. Complex 8. Elemental analysis for CsaH,,FeNi,O,P,, calcd. (found), %: C 72.35 (71.67);H5.12(4.88);Ni8.04(7.59).1R-spectrum(KBr),cm~‘:2953w(v,,,);1581w ); 1291m (vc=,); 1253~; 813~; 687vs( r&c in o-ccc-P); 14%~ ( +=o) ; 142% ( %(A+H 740s (&(A+H); 513s ( VFe-cp) . ‘H-NMR (C,D,), @pm; 1.43 (s, 6H, 2 X CH,) ; 4.02 (s, 4H, H,,H&,H,,H; from 2XCp); 4.44 (s, 4H, H1,H;, H4, Hi from 2XCp); 6.41 (m, 6H, metu- and puru-H from 2 X&H,-Ni); 7.00-7.15 (m, 34H, metu- and puru-H from 10 X C,H,--P; ortho-H from 2 X C,H,-Ni) ; 7.38-7.68 (m, 20H, ortho-H from 10 X C6H,P). UV-spectrum (methanol), h,,,(lge), nm: 222(4.45); 266(4.23); 334(4.01). 2.3. Synthesis of complex 9. To a suspension of 4.43 g (5 mmol) of disodium{ benzene-l ,6bis [2-0x0-1-( triphenylphosphoranylidene)ethylsulfonate] } in 100 ml toluene which contained 2.63 g (10 mmol) triphenylphosphine were added 2.72 g (10 mmol) bis( 1,5-cyclooctadiene)nickel(O). The reaction mixture was stirred 18 h at room temperature, 10 min at 50°C and after cooling, 20 ml hexane were added. The solid was filtered off, washed with toluene (2 X 20) ml and dried at 0.1 torr for 8 h. Yield: 4.97 g (65%). 2.3.1. Analysis Elemental analysis for Cs2HtiNa,Ni,0sP,S,, calcd. (found), %: C 64.41 (64.85); H 4.23 (4.81); Ni 7.68 (7.95). FT-IR-spectrum (KBr), cm-‘: 1631s ( vsol); 1576~ (~c,~~,o_c=~_~); 1484~s (vc=o); 1438~s (vc(,,,,); 1337s (v,=,); 815~; 693vs-749s ). ‘H-NMR (270 MHz, d,-DMSO), Gppm: 7.50 (v br.s, wO= 243 Hz). UV(&(A+H spectrum (methanol), h,,,(lge), nm: 222(4.75); 255(4.37); 272(4.28); 328(3.99). 2.4. General procedure for ethene polymerization
by the bin&ear
nickel-ylide
complexes
Etbene polymerizations were carried out in a 250 ml thermostated batch stainless steel reactor (Buchi Laborautoclave BEP 280), supplied with a mechanical stirrer, a speed controller and a digital indicator system for temperature, pressure and speed.
K. Kurtev, A. Tomov / Journal of Molecular Catalysis 88 (I 994) 141-150
145
Before every experiment the reactor was cleaned and dried under vacuum at 100°C for 1 h. After cooling it was filled with 100 ml of solvent (purified in the usual way, distilled over metallic sodium, and stored under argon). The catalyst solution, prepared by dissolution of a nickel complex ( 10-150 mg) and the appropriate phosphine scavenger (50-200 mg), was transferred to the reactor. The reactor content was briefly evacuated and then charged with ethene (ethene 99.95%, from the Petrochemical Works, Bourgas, Bulgaria, without further purification) at 3 atm lower, than the reaction pressure. Then the reaction mixture was stirred and heated to the desired temperature. A constant ethene pressure was maintained by a pressure regulator and a pressure transmitter valve (Brooks Instrument B.V.) .
3. Results and discussion 3.1. Catalyst synthesis All binuclear nickel-ylide complexes based upon bis-a-ketoylide ligands, such as those indicated by l-9, were prepared by oxidative addition of phosphorus(V) bis-cu-ketoylides [ 151 to Ni(COD)* in the presence of PPh,, according to Scheme 1. It was found that the synthesis of binuclear nickel-ylide complexes is possible only when the bis-a-ketoylide groups are not linked to vicinal carbon atoms and are not located in one and the same plane. Otherwise decomposition of Ni( COD), occurs. For example, all our attempts to prepare binuclear nickel-ylide complexes from bis- 1,2- [ I-phenyl- 1- ( triphenylphosphoranylideno) acetyl] benzene failed, probably because of the specific O-O coordination of the ylide to the nickel atom. 3.2. Ethene polymerization It is well known that nickel P-O chelate complexes are active catalysts for ethene oligomerization to higher a-alkenes [ 17,181. They can be readily converted into catalysts for ethene polymerization by applying phosphine scavengers [ 81. Some of the binuclear nickel-ylide complexes, for example 3,4 and 6 oligomerize ethene but the product linearity is lower those obtained by the mononuclear ones. Complexes 1,2 and 9 polymerize ethene even without phosphine scavengers thus producing low molecular weight polyethylene. Complexes 7 and 8 are catalytically inactive for ethene polymerization in the absence of catalyst promoters. All the binuclear nickel-ylide complexes (l-9) polymerize ethene in presence of phosphine scavengers to give polyethylene. As effective promoters (COD)$h&l,, ( C2H,),Rh2C1,, Ni( COD)2 and PdCl*( CH,CN), were used. The results from a variety of polymerization reactions are listed in Table 1. Runs 1,3,4,6, 17 and 19 show the influence of the type of phosphine scavenger used on the catalyst productivity. For the majority of the complexes the most effective promoter was Ni( COD),. For catalyst 5, only (C&)&h& binds phosphines more strongly than Ni( COD),. The effectiveness of the phosphine scavengers as catalyst promoters changes in the following sequence:
146
K. Kurtev, A. Tomov /Journal
2Ni
I COD
I2
of Molecular Catalysis 88 (1994) 141-150
+ PPh3
Catalyst
R
RI
Yield
NO
%
l/L - C6HL
H
50
1.3 - C6HL
Ph
5L
I CH2je-
Ph
70
- lCH21e-
C02Me
52
-iCH211-
C02Me
51
-
6 H
+ l,l’-
1y5 - CsH&Fe
l-l’-
(%5 - CsH&
Scheme 1. Preparation
> (C,H,)&h,C12
72
Ph
69
Me
64
SO,Na
65
‘H
l.L-
Ni(COD)2
Ph
Fe
CsHb
of binuclear nickel-ylide
> (COD),Rh,Cl,
complexes.
>PdCl,(CH,CN)2
Runs 12, 15 represent the influence of the distance between both the active centers on the catalyst productivity. Decreasing the distance between them leads to a significant increase of the catalyst productivity, which may be attributed to the mutual influence of the active centers - indirect electronic interactions and stronger spatial repulsion. Runs 5 and 3 1 exhibit the influence of the second substituent R, in the chelate rings on the catalytic activity. Electron withdrawing groups significantly increase the polymerization activity of the catalysts, and vice versa - the rich of electrons ferrocene ring decrease it remarkably (runs 27 and 30). Runs 11 and 22 represent the influence of the distance as well as the type of the moiety, linking the active centers on the catalytic activity. The higher activity of catalyst 6, compared whit that of 3 is apparently due to the shorter distance between the active centers and the higher steric parameter of the norbomene ring, which restricts the free rotation of the active centers and the substrate molecules “know how to find them”.
K. Kurtev, A. Tomov/Journal Table 1 Etbene polymerization
by binuclear nickel-ylide
catalysts
Run No.
Catalyst No.
Phosphine scavenger”
Solvent
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
1 1 1 1 1 1 2 2 2 3 3 4 4 4 5 5 5 5 5 6 6 6 6 6 6 6 7 7 7 8 9 9
Rh-1 Rh-1 Rh-2 Ni Ni Ni Rh-1 Rh-2 Ni Rh-1 Ni Rh- 1 Ni Ni Rh-I Rh-1 Pd Ni Rh-1 Rh-1 Pd Ni Ni Ni Ni Ni Ni Ni Rh-1 Ni Ni Ni
toluene toluene toluene toluene toluene methanol toluene toluene toluene
a.Rh-I is Rha-@Zl,(C,H,),, b 88% methanol.
147
ofMolecular Catalysis 88 (1994) 141-150
toluene toluene toluene toluene toluene toluene toluene toluene methanol toluene toluene toluene toluene toluene methanol methanoP toluene toluene toluene toluene toluene toluene
Rh-2 is Rh,ip-Cl,(COD),,
P
T
Productivity
(atm)
(“C)
(kg PE/S Ni*h)
16.6 25.5 26.0 15.5 4.2 17.5 25.5 24.5 5.5 24.5 25.0 17.0 17.0 25.0 17.0 26.0 17.5 17.0 21.5 15.0 25.0 25.0 5.4 5.0 25.0 14.5 25.0 5.6 25.5 25.0 4.0 17.0
50 50 50 48 50 48 50 50 50 50 50 48 49 50 50 50 50 46 51 44 50 48 48 55 50 50 JO 50 50 51 55 55
2.1 3.9 2.4 4.5 2.7 1.2 1.1 0.6 1.0 0.3 0.9 0.7 1.0 1.9 8.5 11.9 2.4 5.5 0.3 1.9 1.1 13.8 7.0 7.8 8.6 1.5 0.8 0.2 0.2 0.2 35.2 87.5
Pd is PdCla(CH,CN)a,
Ni is Ni(COD),.
In agreement with this proposal, the IR spectrum of complex 6 (2% solution in CHCl,) exhibited two shoulders on the absorption band for the carbonyl groups (Fig. 1). The double bond of the norbomene ring reveals absorption at 1626 cm-‘. When Ph,P was removed from the coordination sphere of the metal ~c-c absorption band was shifted to 1602 cm- ‘. It was assumed to be a result of an intramolecular coordination of the double bond to the nickel atom from the endo-chelate ring, but all our attempts to gain a better insight into the impact of this coordination on the catalyst activity has failed so far. The ability of complex 6 to polymerize ethene in the presence of methanol and watermethanol mixtures is remarkable (runs 2526).
148
K. Kurtev, A. Tomov / Journal
ofMolecular Catalysis 88 (1994) 141-150
1513 cm-’
IL93 cm-’
Y /\
ekzo
- > C=O group
J
lL76cm-’
I
endo
- > C = 0 group
Fig. 1. Carbonyl stretching vibrations band for 6.
Ph
Ph
o\Ni,pPh3 H
I
x
/
o\Ni,PPh3 I
‘Ph
Na03S
IO Productivity
‘Ph
‘Ph 11
= 0.24 kg PE/g
Fig. 2. Productivity
p/
x
ph’
Ph/p\Ph
Ni.h
Productivity
of the mononuclear
= 23.20
kg PE/g
Ni.h
catalysts 10 and 11.
Runs 3 1 and 32 showed the significance of the introduction of a second metal center into the complexes under question on the catalytic activity. To compare the catalytic activities of the binuclear complexes with the mononuclear ones, we have used the experimental data for complexes 10and 11,reported by U. Klabunde et al. [ 81. Runs 5 and 3 1 displayed that the binuclear nickel-ylide complexes exhibited higher catalytic activity than the corresponding mononuclear ones. Runs 2,7 and 5,9 showed the influence of the conjugation between the metal centers on the activity of the catalysts. The presence of a conjugated system, comprising two active centers and the 1,Csubstituted benzene ring was confirmed using UV-spectroscopy. For nm. We suggest that the complex 1 A,,, is at 340 nm, while for complex 2 A,,,=326 higher activity of catalyst 9 is due to the conjugation between the active centers as well as to the presence of the electron withdrawing S03Na substituents in both the chelate rings.
3.3. Polyethylene properties
The properties of the polyethylene produced by the binuclear nickel-ylide complexes in the presence of phosphine scavengers depend strongly on the type of the moiety linking the active centers (Table 2). The crystallinity (DSC determined) of the polyethylene obtained was from 60% to 90% and the density between 0.935 and 0.975.
K. Kurtev, A. Tomov/Journal Table 2 Properties of the polyethylene scavenger
of Molecular
prepared by binuclear nickel-ylide
Catalyst No.
T
P
Productivity
(“C)
(atm)
(kg PE/g Ni*h)
1 4 5” 6 9 9
48 49 50 66 64 60
5.6 17.5 26.5 4.2 4.0 17.0
2.79 2.13 11.88 7.86 35.16 87.50
a Phosphine scavenger:
149
Catalysis 88 (1994) 141-150
catalyst in presence of Ni (COD) 2 as a phosphine
M”
M,
&I%
9000 4300 3 100 5 700 7 800 9900
271000 9700 6 200 40 400 98 400 164300
30.1 2.3 2.0 7.1 12.6 16.6
Rhz-~-C1,(C&),.
4. Conclusion The introduction of a second nickel-ylide group into the nickel P-O chelate complexes, in the presence of phosphine scavengers yields high activity ethene polymerization catalysts resistant to deactivation by oxygenated species. The existence of conjugation and shortening the distance between the active centers makes these complexes much more active ethene polymerization catalysts than the mononuclear ones.
5. Acknowledgement The support of the Bulgarian tude.
National Science Foundation
is acknowledged
with grati-
6. References [I] W. Keim, F.H. Kowaldt, R. Goddard, C. Krtiger, Angew. Chem., 90 ( 1978) 493. [2] W. Keim, A. Behr, B. Gruber, B. Hoffmann, F.H. Kowaldt, U. Kurschner, B. Limbacker, F.P. Sisting, Organometallics, 5 ( 1986) 2356. [3] W. Keim, New J. Chem., 11 ( 1987) 531. [4] D. Beach, J. Harrison, US Pat. 4,293,727 (1981). [5] D. Beach, J. Harrison, US Pat. 4,310,716 (1982). [6] D. Beach, J. Harrison, US Pat. 4,711,969 (1987). [7] U. Klabunde, US Pats. 4,698,403 and 4,716,205 ( 1987). [ 81 U. Klabunde, R. Mulhaupt, T. Herskovitz, A.H. Janowicz, J. Calabrese, S.D. Ittel, J. Polym. Sci., Part A: Polym. Chem., 25 (1987) 1989. [9] K.A. Ostoja-Starzewski, J. Witte, Angew. Chem., 97 ( 1985) 610. [lo] K.A. Ostoja-Starzewski, J. Witte, Angew. Chem., 99 ( 1987) 76. [ 1 l] G. Braca, A. Ricci, G. Sbrana, M. Brunelli, A. Giusti, G. Bertolini, A.M. Raspolli Galletti, Eur. Pat. 0 393 751 A2 (1990). [ 121 G. Braca, Chim. Oggi., ( 1988) 23; 11. [ 131 A. Bader, E. Linder, Coord. Chem. Rev., 27 ( 1991) 108.
150 [ 141 [ 151 [ 161 [ 171 [ 181
K. Kurtev, A. Tomov / Journal of Molecular Catalysis 88 (1994) 141-150 S. Otsuka, M. Rossi, J. Chem. SOL, (1968) 2630. A. Tomov, K. Kurtev, Bulg. Chem. Commun., 25 (1992) 436. M. Toumaire, Ann. Chim. Anal., 27 (1945) 184. W. Keim, Stud. Surf. Sci. Catal., 25 (1986) 201. W. Keim, J. Mol. Catal., 52 (1989) 19.