J . Am. Chem. SOC.1989, I l l , 2875-2882
2815
Catalytic Dimerization of Ethylene and Propylene by (q6-Arene)NiR2and in Combination with Alkylaluminum Halides. Production of Highly Active Homogeneous Catalysts Seok-Burm Choe, Hiroyoshi Kanai, and Kenneth J. Klabunde* Contribution from the Department of Chemistry, Kansas State University, Manhattan, Kansas 66506. Received August 29, 1988
Abstract: A series of ($-arene)NiR2 and (g6-arene)CoR2(R = SiF3,SiCI,, C,F,; arene = benzene, toluene, mesitylene) complexes were examined for activity as homogeneous catalysts for ethylene and propylene dimerization. Very high activities were encountered especially for M = Ni and R = SiCI,. Kinetic analyses were carried out showing approximately first-order dependence on ethylene and Ni catalyst. Reaction rate changes with variation showed the following: in arene, benzene > toluene > mesitylene; with change in R, SiCI3 >> SiF, > C6F,; with change in M, Ni >> Co. A mechanism and catalytic cycle are proposed, suggesting a Ni-H species as a key catalytic intermediate and the rate-determining step as production of the Ni-H species by Ni-Si bond breaking and elimination of RCH=CH2. Addition of a Lewis acid cocatalyst EtAIC1, had a dramatic effect, causing even higher dimerization rates and longer catalyst lifetimes. Extensive multinuclear NMR studies suggested the formation of a (~6-arene)Ni(SiC13)2.4EtAlC12 adduct where Si-C1 bonds were converted to Si-Et species. With the cocatalyst system propylene could also be dimerized rapidly but with more rapid catalyst degradation. Mechanistic proposals for the effect of EtAICI2 are given.
Ziegler reported in 1954 the so-called "nickel effect" whereby Table I. Dimerization of Ethylene with (06-Arene)NiR2" a small amount of nickel could mediate C2H, insertion into the Droduct ratio.' % A1-C bond of Et,A1 so that the product was 1-butene, rather than max trans-2po1yethylene.l Since this report, other workers have reported on Bu catalysts rateb Nt, s-] 1-Bu cis-2-Bu a variety of transition-metal systems in combination with alkyl25.8 41.6 (~6-benzene)Ni(SiC13)z 1.5 0.025 32.6 aluminums and alkylaluminum halides as catalysts for C2H4 22.6 39.3 (06-toluene)Ni(SiC1!)2 1.4 0.023 38.1 dimerization. Among the early transition metals, titanium and 20.6 37.2 (?6-mesitylene)Ni(SiCI,), 0.8 0.01 3 42.8 zirconium alkoxides24 and halides5v6showed the highest activity (7,-toluene)Ni(SiF,), 0.14 0.0023 78.7 11.8 9.5 for dimerization, oligomerization, and polymerization reactions. In6-toluene~NilCIF,~, 0.09 0.0015 Among the later transition metals, most of the published work "The reaition was carried out in bromobenzene solvent at 0 OC, 200 deals with Ni complexes. Ligands such as acetylacetonato,' olefins, Torr ethylene constant pressure, and 5 X lo-, M initial nickel concendienes,8 s3-allyl group^,^ and others have been employed. High trations. See Experimental Section for details. bunits: mol of ethylactivities for dimerization or oligomerization have been realized ene consumed/mol of catalystamin. 1-Bu = 1-butene. cis-2-Bu = but usually in combination with Lewis acids such as alkylcis-2-butene. ~rans-2-Bu= trans-2-butene. aluminum halide^.^,'^ Activity in the absence of Lewis acid is rare, although there are some systems that have been investithe complexity of these cocatalyst systems has made it difficult gated."J2 to gain the clear understanding desired. Mechanistic investigations have also been r e p ~ r t e d , ~ Jbut ~ ~ ~ ~ - ' ~ During our investigations of a new class of N i complexes, i.e. (@arene)NiR2 ( R = SiF3, SiCI,, C6F5),16-18we have discovered that these materials possess extremely high activities for 1-butene (1) (a) Ziegler, K. Erennst.-Chem. 1954,35, 321. (b) Fischer, K.; Jonas, isomeri~ation'~ as well as ethylene and propylene dimerization K.; Misbach, P.; Stabba, R.; Wilke, G. Angew. Chem., Int. Ed. Engl. 1973, in the absence of a cocatalyst. And, addition of a cocatalyst 12, 943. (2) Martin, H. Angew. Chem. 1956, 68, 306. increases their activities and lifetimes. Herein, we report our (3) Cesca, S.; Marconi, W.; Santostasi, M. L. J . Polym. Sci., Part E 1969, investigations of the dimerization process, both with and without 7, 547. cocatalyst. We have investigated both homogeneous systems as (4) Naatta, G . J . Polym. Sci. 1959, 34, 151. well as a heterogenized (polystyrene)NiR2 system. Throughout (5) Langer, A. W. J . Macromol. Sci., Chem. 1970, 4 , 775. (6) Attrige, C. J.; Jackson, R.; Maddock, S. J.; Thompson, D. P. J . Chem. this work we hoped to gain evidence of catalytically active inSoc., Chem. Commun. 1973, 132. termediates and evidence regarding the role of the cocatalyst. (7) Jones, J. R.; Symes, T. J. J . Chem. SOC.C 1971, 1124. (8) Onsager, 0. T.; Wang, H.; Blindheim, U. Helu. Chim. Acta 1969, 52, Results 187. I. (q6-Arene)NiR2Monocatalyst System (No Cocatalyst). Our (9) Bogdanovic, B.; Henc, B.; Karmann, H. G.; Nussell, H. G.; Walter, D.;Wilke, G. Ind. Eng. Chem. 1970, 62, 34. first series of experiments were designed to lend understanding (10) (a) Maruya, K.-i.; Mizoroki, T.; Ozaki, A. Bull. Chem. SOC.Jpn. of the effect of structural modification to 1 1972, 45, 2255. (b) Ishimaru, Y . ;Maruya, K.-i.; Nakamura, Y . ;Mizoroki, (q6-arene)NiR2catalyst T.; Ozaki, A. Chem. Lett. 1981, 657. (c) Su, C. L.; Collette, J. W. J . Organomet. Chem. 1972, 36, 177. (d) Olive, 0. H.; Olive, S.; Schmidt, E. CH2=CH2 0 o c , solvent J . Organomet. Chem. 1972, 39, 202. (e) BogdanoviE, B.; Spliethoff, B.; Wilke, CH2=CHCH2CH3 + cis/trans-CH3CH=CHCH3 G . Angew. Chem., Int. Ed. Engl. 1980, 19, 622. (f) Onsager, 0. T.; Wang, H.; Blindheim, U. Helu. Chim. Acta 1969, 52, 187. on the rate of ethylene dimerization. Kinetic analyses were carried ( 1 1 ) A series of catalysts prepared by SHOP (Shell High Olefin Process) showed high activity without aluminum cocatalysts. (12) (a) McClure. J. P.; Barnett, K. W. J . Organomer. Chem. 1974, 80, 385. (b) Keim, W.; Hoffmann, B.; Lodewick, R.; Peuchert, M.; Schmitt, G.; (16) Lin, S. T.; Narske, R. N.; Klabunde, K. J. Organomerallics 1985, 4, Fleischhaver, J.; Meier, U. J . Mol. Catal. 1979,6, 79. (c) Keim, W.; Kowaldt, 571. F. H.; Goddard, R.;Kruger, C. Angew. Chem., Int. Ed. Engl. 1978, 17, 466. (17) Groshens, T. J.; Klabunde, K. J. J . Organomet. Chem. 1983,259, 337. ( 1 3) Onsager, 0. T.; Wang, H.; Blindheim, U. Helo. Chim. Acra 1969,52, (18) Janikowski,S. K.; Radonovich, L. J.; Groshens, T. J.; Klabunde, K. 230. J. Organometallics 1985, 4 , 396. (14) Jones, J. R. J . Chem. SOC.c 1971, 1117. (19) Kanai, H.; Choe, S. B.; Klabunde, K. J. J . A m . Chem. Soc. 1986,108, ( 1 5) Sen, A.; Lai, T.W. Organometallics 1983, 2, 1059. 2019. ~~
0002-7863/89/1511-2875$01.50/0
0 1989 American Chemical Society
2816
J . A m . Chem. Soc.. Vol. 1 I I , No. 8, 1989
Choe et ai.
Table 11. Solvent Effects on Ethylene Dimerization Reactionso Droduct ratio? % trans-2-
solvent iodobenzene bromobenzene chlorobenzene fluorobenzene toluene methylene chloride
rateb 1.4 1.4 0.14 0.05
0.001 toluene > mesitylene. This finding is in accord with the lability of the q6-arene determined in previous work from our laboratory.2&22 That is, more electron-rich arenes bind to Ni more strongly and are less labile, and this leads to less active catalysts. This result is also in agreement with our earlier work on 1-butene isomeri~ation.'~ Product distributions derived from the benzene, toluene, and mesitylene complexes are also shown in Table I, varied only slightly, but the mesitylene system gave the best selectivity to 1-butene. More active catalysts generally gave poorer selectivity to 1-butene. B. Variation in R (R = SiF,, SiCI,, C6F5). While $-arzne was kept the same (toluene), the R groups were varied and kinetic analyses of the dimerization again carried In these experiments we observed very large reaction rate differences (Table I). Obviously, the catalytic process is very sensitive to the nature of R. The activity order is R = SiCI, >> SiF, > C6F5. Also, we noted that the induction period to reach maximum reaction rate was shorter for R = SiCI, (6 min for SiCI,; 10 min for SiF3and C6FS). C. Solvent Effect. Solvent effects in alkene dimerization reactions can be drama ti^?^'^,^'^^ However, systematic studies have rarely been reported. Our earlier work showed that solvent does have an important role,19 and this is especially true in ethylene dimerization. We were not able to use alkane solvents due to the relative insolubility of 1 in these. Also, 1 reacts by arene displacement in ethers, sulfides, and other Lewis base solvents. Thus, we were (20) (a) Groshens, T. J.; Klabunde, K. J. Organometallics 1982, 1, 564. (b) Lin, S. T.; Groshens, T. J.; Klabunde, K. J. Inorg. Chem. 1984, 23, 1. (21) Brezinski, M.; Klabunde, K. J. Organometallics 1983, 2, 1116. (22) Choe, S. B.; Klabunde, K. J. J . Organomet. Chem. 1989, 359, 409-418. (23) Syntheses of these compounds have been reported in ref 16 and the following: (a) Brezinski, M.; Klabunde, K. J.; Anderson, B. B. Organomet. S y n f h . 1986, 3, 158. (b) Choe, S. B.; Klabunde, K. J. Organomet. Synth. 1986, 3, 153. (c) Choe, S. B.; Klabunde, K. J. Organomet. Synth. 1986, 3, 156. (d) Lin, S. T.; Klabunde, K. J. Organomet. Synth. 1986, 3, 147. (24) Olive, 0. H.; Olive, S.; Schmidt, E. J . Organomet. Chem. 1972, 39, 202. Kawakami, K.; Mizoroki, T.; Ozaki, A. Bull. Chem. SOC.Jpn. 1978,51, 21. (25) Onsager, 0.T.; Wang, H.; Blindheim, U. Helu. Chim.Acta 1969, 52, 196. (26) Akhmedov, V. M.; Khanmetov, A. A,; Mardanov, M . A,; Zakharkin, L. 1. J . Org. Chem. USSR (Engl. Transl.) 1973, 9, 442.
Table 111. Effect of [Nil and Reaction
P c H ~ ~onHthe ~
Ethylene Dimerization
1.4 x 10-3 2.8 x 10-3 3.8 x 10-3 5.2 x 10-3 3.0 x 10-3 5.0 x 10-3 7.5 x 10-3 9.8 x 10-3 P c H
