Butadiene complexes with nickel

Our experimental finding supports the view that the active site of butadiene polymerization in the presence of bis(7r-crotylnickel iodide) is the complex with nickel bound to iodide. Thus, the butadiene addition across syn-7r-allyllic bond produces trans-1,4-polybutadiene. 

Nickel(O) forms a n-complex with three butadiene molecules at low temperature. This complex rearranges spontaneously at 0 °C to afford a bisallylic system, from which a large number of interesting olefins can be obtained. The scheme given below and the example of the synthesis of the odorous compound muscone (R. Baker, 1972, 1974 A.P. Kozikowski, 1976) indicate the variability of such rearrangements (P. Heimbach, 1970). Nowadays many rather complicated cycloolefins are synthesized on a large scale by such reactions and should be kept in mind as possible starting materials, e.g. after ozonolysis. 

One other reaction deserves mention. From bis(cyclooctadiene)nickel and butadiene (31), and in the presence of an isocyanide (RNC, R = cyclohexyl, phenyl, tcrt-butyl) two organic oligomeric products are obtained, 1 -acylimino-11 -vinyl-3,7-cycloundecadiene and 1 -acylimino-3,7,11 -cyclo-dodecatriene. In each, one isocyanide has been incorporated. An analogous reaction with carbon monoxide had been reported earlier. The proposed mechanism of these reactions, via a bis-7r-allyl complex of nickel, is probably related to the mechanism described for allylpalladium complexes above. 

Among transition metal complexes used as catalysts for reactions of the above-mentioned types b and c, the most versatile are nickel complexes. The characteristic reactions of butadiene catalyzed by nickel complexes are cyclizations. Formations of 1,5-cyclooctadiene (COD) (1) and 1,5,9-cyclododecatriene (CDT) (2) are typical reactions (2-9). In addition, other cyclic compounds (3-6) shown below are formed by nickel catalysts. Considerable selectivity to form one of these cyclic oligomers as a main product by modification of the catalytic species with different phosphine or phosphite as ligands has been observed (3, 4). 

Linear oligomerization and telomerization of butadiene take place with nickel complexes in the presence of a proton source (7). In addition, cooligomerization of butadiene with functionalized olefins such as methacrylate is catalyzed by nickel complexes [Eq. (4)] (12, 13) ... 

Similar studies on the reactions of butadiene and bis(ir-allyl)palladium were carried out by Wilke and co-workers (4). Unlike the reactions with nickel complexes, no cyclization took place, and 1,6,10-dodecatriene... 

These telomerization reactions of butadiene with nucleophiles are also catalyzed by nickel complexes. For example, amines (18-23), active methylene compounds (23, 24), alcohols (25, 26), and phenol (27) react with butadiene. However, the selectivity and catalytic activity of nickel catalysts are lower than those of palladium catalysts. In addition, a mixture of monomeric and dimeric telomers is usually formed with nickel catalysts ... 

With nickel complexes, these cocyclizations are not possible. A related reaction is the cocyclization of butadiene with azines to give 12-mem-bered heterocyclic compounds 9 (11) [see Eq. (3)]. 

The interaction of butadiene with nickel afford a gray, intractable, and nonvolatile material together with traces of a volatile yellow oil-containing bis(crotyl)nickel. Further reaction of the nonvolatile fraction with butadiene gives a bis(allyl)-C12 nickel complex (IV) in good yield (709) ... 

The cyclic cooligomerization of 2-vinylthiophene with butadiene, catalyzed by nickel complexes, has given (312) and (313) in a 1 2 ratio (78IZV1469). 

Before discussing hydrocyanation chemistry we will explore the interaction of zero-valent nickel phosphite complexes with various independent components of the catalytic system. Then, in turn, we will examine the catalyzed addition of HCN to butadiene, the isomerization of olefins, and the addition of HCN to monoolefins. Finally, a summary of the mechanism as it is now understood will be presented. 

Consequently, new dilithium-nickel-olefin complexes with tetra- or pentacoordinated nickel atoms are formed, e.g., the Li2Ni complexes Li2Ni[(CH3)2NCH2CHCHCH2N(CH3)2]3 (18), (LiTMEDA)2Ni(C2H4)3 (19), (LiTMEDA NifCVHw (20), and (LiTHF)2Ni(C4H6)3 (21), by reaction with N,N,N, TV -tetramethy lbutene-2-diamine, ethylene, norbor-nene, or butadiene (14, 31-33). 

The biphosphite ligands, (5) and (6), react with [(cod)2Ni] to form nickel complexes of type (7). Nickel phosphite complexes are catalysts in the hydrocyanation of butadiene complex (7) is more robust than the monodentate phosphite analogs. ... 

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... 

Soluble single species catalysts are also known, such as the bis(7r-allyl nickel halides) [7]. These can be prepared separately or in situ by reacting bis-allyl nickel (which is an ologomerization catalyst for butadiene but does not give high molecular weight polymer) with an equimolar quantity of nickel halide, and thus bears some resemblance to the catalysts from titanium subhalides and alkyl titanium halides. It is of interest to note that the active species is the monomeric form of the initiator as TT-complex with butadiene (XII) [61]. 

In coordination polymerization it is generally accepted that the monomer forms a 7r-complex with the transition metal prior to insertion into the growing chain. In general these complexes are insufficiently stable to be isolated although complexes of allene [69] and butadiene [70] have been reported. With allene the complex was formed prior to polymerization with soluble nickel catalysts, and cis coordinated butadiene forms part of the cobalt complex, CoCj 2H19, which is a dimerization cateilyst. 

Catalysts from Group VIII metals have given unsatisfactory results. In the polymerization of butadiene with soluble cobalt catalysts tritium is not incorporated when dry active methanol is employed [115], although it is combined when it has not been specially dried [117, 118]. Alkoxyl groups have been found when using dry alcohol [115, 119] but the reaction is apparently slow and not suited to quantitative work [119]. Side reactions result in the incorporation of tritium into the polymer other than by termination of active chains [118], probably from the addition of hydrogen chloride produced by reaction of the alcohol with the aluminium diethyl chloride [108], Complexes of nickel, rhodium and ruthenium will polymerize butadiene in alcohol solution [7, 120], and with these it has not been possible to determine active site concentrations directly. 

The kinetics of butadiene polymerized by bis(7T-allyl nickel trifluoro-acetate) has been studied by Teyssie et al. [173]. Equilibrium constants for the formation of the complex (with aromatic compounds which give the equibinary polymer), calculated from cryoscopic measurements or polymer micro-structure, are 6—7 and 26—35 respectively for benzene and nitrobenzene. The higher concentration of active centres compared with... 

A remarkable example of the cooperation of different active sites in a polyfunctional catalyst is the one-step synthesis of 2-ethylhexanol, including a combined hydroformylation, aldol condensation, and hydrogenation process [17]. The catalyst in this case is a carbonyl-phosphine-rhodium complex immobilized on to polystyrene carrying amino groups close to the metal center. Another multistep catalytic process is the cyclooligomerization of butadiene combined with a subsequent hydroformylation or hydrogenation step [24, 25] using a styrene polymer on to which a rhodium-phosphine and a nickel-phosphine complex are anchored (cf Section 3.1.5). 

Like nickel, Pt(0) complexes undergo alkene dimerization with allene, and with 1,3-butadiene, but with 2,3-dimethyl-1,3-butadiene simple five-membered ring formation occurs ... 

There is a notable tendency to form oligomers when acetylenic substances interact with compounds of metals, and this tendency is also shown by butadiene 117) (see Section IV, B,d). This is particularly so with the carbonyls of iron and cobalt, and the oligomerization reactions are favored with nickel 121) and with palladium compounds 113, 122, 123). This phenomenon may be related to the hydropolymerization of acetylenes on metal surfaces, and it may be that such polymerization processes would be better described in terms of ir-complexes. 

NMR studies show that the complex carrying the growing chain in the butadiene polymerization with bis[(77 -allyl)nickel-trifluoracetate] is predominantly in the form of a binuclear syn-(Tj -allyl)nickel complex. With [(rj -allyONillj polybutadiene is formed with 97% trans-1,4 microstructure. ... 

The best known example is the cyclization of butadiene and acetylene 121 14°). Butadiene forms cyclooctadiene and cyclododecatriene by the catalytic action of nickel, iron, and other metal complexes. By an experiment using an iron complex with deuterated butadiene, it was proved that no hydrogen shift takes place in the cyclization reaction 70>. 

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