Nickel, 1,3-butadiene trimerization with

Some insight into the nature of the coordination and addition steps can be deduced from the cyclo-oligomerization work reported by Wilke (316). Butadiene can be converted into several isomers of cyclododeca-triene using (C2H5)aAlCl/TiCl4, AlEta/Cr02Cl2 and AlEta/nickel acetyl-acetonate catalysts. With the nickel catalysts, open chain, jr-complexed intermediates have been isolated for both the butadiene trimer and the dimer. The open chain dimer structure is shown below, where Do = a bulky Lewis base and the nickel is apparently zero valent. 

Diene Cyclization. In 1952 Reed (157) discovered the catalytic dimerization of butadiene with Reppe catalyst in the presence of acetylene. Important results were obtained by Wilke (200) in the cyclization of butadiene with a nickel(0) catalyst. With bis-7r-allylnickel, biscyclo-i,5-octadienenickel, or cyclododecatrienenickel, he obtained the trimerization of butadiene to cyclododecatetraene while, with a catalyst of the type Ni(PR3)4, in which perhaps one coordination site cannot be replaced, he obtained the dimerization to cycloocta-l,5-diene. The mechanism of these reactions, in which 7r-allyl systems can be in equilibrium with o--7r-allyl systems (Figure 7), have been proved by Wilke and co-workers who isolated the intermediate compounds. It is worth noting that all these catalysts have ligands of weak -acceptor character which are labile and do not prevent butadiene from coordinating. The presence of weak t acceptors on the nickel tends to favor the structure of the diene, as was emphasized by Mason (112). 

The first active catalyst system found was prepared by reaction of nickel ace-tylacetonate with organoaluminum compounds in the presence of phenylacetylene. A dark red solution was obtained which reacted at 80° C. under pressure with butadiene to about 24% cyclo-octadiene, 8% vinylcyclohexene, and 63% all-tmns-cyclododecatriene. The component which stabilizes the reduced nickel was then changed systematically to discover the possibility of directing the synthesis at will in the direction of a trimerization or dimerization. Today we can synthesize cyclo-octadiene in yields of 95% or cyclododecatriene in similarly good yields only by altering the electron-donor molecules used in preparing the catalyst. 

Cooligomerization (hetero-oligomerization) of olefins and acetylenes with butadiene in the presence of nickel complexes prevents the formation of butadiene trimers. During hetero-oligomerization chain and cyclic compounds may be formed see equations (13.87) and (13.88). Dodeca-2,6,10-triene-l,12-diylnickel reacts with allene to give various products. Reaction (13.89) is an example. 

The nickel-catalyzed [4 + 4]-cycloaddition of butadiene to form cyclooctadiene was first reported by Reed in 1954.90 Pioneering mechanistic and synthetic studies largely derived from the Wilke group advanced this process to an industrially important route to cyclodimers, trimers, and other molecules of interest.91-94,943 95,96 While successful with simple dienes, this process is not useful thus far with substitutionally complex dienes as needed in complex molecule synthesis. In 1986, Wender and Ihle reported the first intramolecular nickel-catalyzed [4 + 4]-reaction of... 

Both di- and trimerization of butadiene with soluble nickel catalysts are well-established homogeneous catalytic reactions. The precatalyst having nickel in the zero oxidation state may be generated in many ways. Reduction of a Ni2+ salt or a coordination complex such as Ni(acac)2 (acac = acetylacetonate) with alkyl aluminum reagent in the presence of butadiene and a suitable tertiary phosphine is the preferred method. The nature of the phosphine ligand plays an important role in determining both the activity and selectivity of the catalytic... 

When butadiene is treated with RuCls in 2-methoxyethanol at 100°C, yellow-brown crystals of composition (C4H8)3RuCl2 are obtained 381). Crystal structural analysis has identified 381, 382] the complex as (2,6,10-dodecatriene-l,12-diyl)dichlororuthenium (146), analogous to the nickel complex (194) suggested 608) as the catalytic intermediate in the nickel-catalyzed cyclic trimerization of butadiene. In this complex, the ruthenium atom has a trigonal-bipyramidal configuration with the... 

Two isomeric 1,5,9-cyclododecatrienes, namely, trans,trans,cis-CijH 18 (XLVI) and trans,trans,trans-CuHis (XLVII), are formed in good yield by the cyclic trimerization of butadiene using certain Ziegler-type catalysts 247, 250, 251, 252). The formation of these 12-membered ring hydrocarbons probably proceeds via metal 7r-complexed intermediates. When the cyclic triene (XLVII) is treated with nickel acetylacetonate and... 

Unlike nickel catalysts which form cyclic dimers and trimers (1,5-cyclooctadiene and 1,5,9-cyclododecatriene), palladium compounds catalyze linear dimerization of conjugated dienes. 1,3-Butadiene itself is converted to 1,3,7-octatriene. The reaction most characteristic of palladium is the formation of various telomers. 1,3-Buta-diene dimerizes with incorporation of various nucleophiles to form telomers of the following type ... 

Wilke and his coworkers have shown that zera-valent complexes, especially of nickel, obtained by reduction with aluminium alkyls can be used in a wide variety of polymerizations such as trimerization of butadiene to trans,tran, trans-cyclododecatriene. 

Recent studies on the allylation of alkynes with bis (7r-allyl) nickel have revealed that the Ni(0) generated in this process causes the trimeri-zation and, more importantly, the reductive dimerization of a portion of the alkyne (8). A deuterolytic work-up led to the terminally di-deuter-ated diene (5), supporting the presence of a nickelole precursor (4) (Scheme 1). The further interaction of 4 with 1, either in a Diels-Alder fashion (6) or by alkyne insertion in a C-Ni bond (7), could lead to the cyclic trimer 8 after extrusion of Ni(0), thereby accounting for the trimerizing action of Ni(0) on alkynes. This detection of dimer 5 then provided impetus for the synthesis of the unknown nickelole system to learn if its properties would accord with this proposed reaction scheme. Therefore, E,E-l,4-dilithio-l,2,3,4-tetraphenyl-l,3-butadiene (9) was treated with bis (triphenylphosphine) nickel (II) chloride or l,2-bis(di-phenylphosphino ethane)nickel(II) chloride to form the nickelole 10 (9) (Scheme 2). The nickelole reacted with dimethyl acetylenedicarboxylate to yield 11 and with CO to produce 12. Finally, in keeping with the hypothesis offered in Scheme 1, 10a did act as a trimerizing catalyst toward diphenylacetylene (13) to yield 14. 

Whereas nickel complexes catalyse the trimerization or dimerization of butadiene to cyclic products, palladium catalysts produce linear oligomers. When bis(dibenzoylacetone)palladium is treated with butadiene at low temperature, a yellow air sensitive complex (rj f/ -dodecatrienediyl)palladium is formed initially. It decomposes above — 20T in the absence of butadiene and in its presence actively catalyses its trimerization to linear 1, 3,6, 10-dodecatetraene. In contrast to the corresponding nickel intermediate, the substituents on the allyl groups are syn. Treatment with a diphosphine affords a metallacycle which contains a huge 13-membered ring. If (A) or (B) is allowed to warm above — 20 C or is treated with ligands (Ph P or CO), dodecatetraene isomers are released (Fig. 12.7). 

In the reactions of olefins with olefins, different transition metal catalysts can give rise to markedly different products (Heimbach, 1973 Buchholzer a/., 1972 Kricka and Ledwith, 1974). Certain nickel catalysts, for example, normally trimerize butadiene as shown in Eq. (83) (Bogdanovic et al., 1969). These same catalysts, however, in the presence of suitable ligands, will cyclo-dimerize butadiene to give initially divinylcyclobutane (which can be isolated in 40% yield) and finally 1,5-cyclooctadiene in high yield [Eq. (84) (Brenner etal., 1969)]. 

The precise mechanism of many oligomerization reactions remains open to discussion. We have already mentioned the question of whether cyclodimerization of butadiene, catalysed by nickel complexes, is a concerted or a stepwise process, of polymerization and then cyclization. The cyclo-trimerization of alkynes is often thought to proceed by co-ordination of three alkyne molecules to the metal catalyst, with a subsequent concerted cyclization step. Recent studies of the cyclotrimerization of hexafluorobut-2-yne in the presence of Ni(cod)j or of arsine complexes, however, suggest a stepwise process in which an intermediate (67) is formed, to which... 

If the complex 9.4 is treated with a molecule which acts as a non-labile ligand to the nickel, then instead of trimerization of butadiene only dimerization occurs. Obviously the non-labile ligand prevents the attachment of a third butadiene molecule. The reaction is represented below and... 

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