Carbon monoxide with alkenes

Even after Shell announced the closure of their plant for Carilon production and despite the uncertain future of this commercial thermoplastic material, investigations are still being conducted. This is probably a consequence of the growing interest in catalysis by late transition metals for the polymerization and co-poly-merization of olefins. Comprehensive reviews of this subject have appeared [4, 5] and will be taken as the basis for the following discussion. 

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Drent, E. van Broekhoven, J. A. M. Doyle, M. J. Wong, P. K. Palladium Catalyzed Copolymerization of Carbon Monoxide with Alkenes to Alternating Polyketones and Polyspiroketals. Fink, G. Muelhaupt, R. Brintzinger, H. H. Eds. Ziegler Catal. Springer, Berlin, 1995, pp 481 496. 

I 8 Copolyi erization of Carbon Monoxide with Alkenes... 

Nozaki. K. Hiyama, T. Stereoselechve alternating copolymerization of carbon monoxide with alkenes. J. Organomet. Chem. 1998, 576, 248—253. 

Low oxidation states - An important characteristic of transition metal chemistry is the formation of compounds with low (often zero or negative) oxidation states. This has little parallel outside the transition elements. Such complexes are frequently associated with ligands like carbon monoxide or alkenes. Compounds analogous to Fe(CO)s, [Ni(cod)2] (cod = 1,4-cyclooctadiene) or [Pt(PPh3]3] are very rarely encountered outside the transition-metal block. The study of the low oxidation compounds is included within organometallic chemistry. We comment about the nature of the bonding in such compounds in Chapter 6. 

There is a tendency toward alternation in the copolymerization of ethylene with carbon monoxide. Copolymerizations of carbon monoxide with tetrafluoroethylene, vinyl acetate, vinyl chloride, and acrylonitrile have been reported but with few details [Starkweather, 1987]. The reactions of alkenes with oxygen and quinones are not well defined in terms of the stoichiometry of the products. These reactions are better classified as retardation or inhibition reactions because of the very slow copolymerization rates (Sec. 3-7a). Other copolymerizations include the reaction of alkene monomers with sulfur and nitroso compounds [Green et al., 1967 Miyata and Sawada, 1988]. 

Nitrenes are very reactive species and normally not isolated. A nitrene can be trapped by its reaction with carbon monoxide and alkenes. 

AlcoholK and alkenes are also primary products and are not shown in the simplified Eq. 15.182. The overall reaction is complicated and, as a result, its mechanism has been the subject of considerable debate.The reaction may be viewed as the reductive polymerization of carbon monoxide, with molecular hydrogen as the reduc-ii agent. A variety oT heterogeneous catalysts, such as metallic iron and cobalt on alumina, have been used. It is believed that carbon monoxide di.ssociaies on the catalytic surface to ve carbides and that these are in tura hydrogenated to give sur ce carbenes ... 

Dioxepanes have been manufactured by treatment of alkenes in the liquid phase with oxygen and carbon monoxide with PdCyCuCl as a catalyst, for example synthesis of (12 X = CN) from acrylonitrile <94JAP0608778i>, or by oxidation of alkenes with Th(III)-acetate in 1,4-diols <76BCJ3285>. Treatment of perfluoro(2-methyl-2-pentene) with 1,4-butanediol and triethylamine leads to (27)... 

Oxidative coupling and reductive cleavage are yet two additional reaction types in which the names reflect metal-based redox changes.In this regard, the metal-catalyzed reactions of carbon monoxide with other donor molecules such as isonitriles (RNC), carbynes (CR), alkenes, and alkynes, often referred to in the literature as reductive couplings to reflect the transformations affecting the ligands, frequently involve metal-based oxidations and should... 

The stereochemistry from chain-end control and catalyst-control are not necessarily different. More details on the stereochemistry of alkene pol3mnerization are provided in Chapter 22. In brief, however, a symmetric catalyst like the ones used for the copolymerization of carbon monoxide with styrene will generate isotactic polymer, but polymerizations with stereochemistry dictated by chain-end control can form either syndiotactic or isotactic material. Catalysts displaying other symmetries have been designed for other types of polymerizations to generate polymer architectures beyond isotactic. 

The regioselective hydrocarboxylation of alkenes and methylenecycloalkanes to linear carboxylic acids was also achieved in good yields and selectivity by the use of oxalic acid (in place of formic add) as the source of hydrogen and carbon monoxide, with the catalytic system Pd(OAc)2-dppb-PPh3 at 150 C and 20 atm.t ... 

Diene complexes can also be decomplexed by treatment with strong Lewis acids (Scheme 10.10). CO insertion occurs, leading to formation of a cyclopentenone 10.33. This reaction is, formally, a cycloaddition of carbon monoxide with a diene, followed by migration of the resulting alkene into conjugation. 

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