Metathesis reaction organometallic polymers

Although olefin metathesis had soon after its discovery attracted considerable interest in industrial chemistry, polymer chemistry and, due to the fact that transition metal carbene species are involved, organometallic chemistry, the reaction was hardly used in organic synthesis for many years. This situation changed when the first structurally defined and stable carbene complexes with high activity in olefin metathesis reactions were described in the late 1980s and early 1990s. A selection of precatalysts discovered in this period and representative applications are summarized in Table 1. 

As discussed above in the mechanism of the alkene dimerization reaction, the polymerization of simple alkenes proceeds by the basic metathesis mechanism. Since polymers that are prepared from complex monomers require homogeneous catalysts, much of the early organometallic catalyst development has had polymer synthesis as the driving force. Recently, developments in the synthesis of organometal-lic complexes that serve as well-defined catalysts for metathesis have opened many opportunities in the area of polymer synthesis. ... 

Olefin metathesis is a transition-metal-catalyzed reaction commonly applied in organic and polymer chemistry [1], Therefore, application of olefin metathesis in coordination and organometallic chemistry as a synthetic tool might initially appear as something unusual, however providing that (i) the metal-containing substrate is sufficiently stable to withstand the presence of the catalyst and (ii) the ligand(s) feature at least one olefinic moiety, this approach proved to be successful. 

Cross-metathesis was recognized as a convenient route to introduce various functionalities into organometallic frameworks, initially including ferrocenes. For example, catalyst with a methylideneferrocenyl ligand was prepared by a stoichiometric reaction of vinylferrocene (4-1) with the Schrock catalyst (Scheme 12.21) [3]. Polymers with one ferrocenyl redox-active end group were obtained with this unique initiator. 

An impoftant series of catalytic reactions involve some of the intennediates and padiways discussed in previous chapters. Alk ie metathesis (Eq. 12.1), now gaining wide acceptance in organic and polymer synthesis, goes via metal cathene intermediates, Alkene polymerization, a key modem development in polymer synthesis, uses unsaturated alkyl complexes. This catalytic reaction allows an exceptional level of control over the molecular structure and therefore over the polymer properties. The water-gas shift and related reactions are of commercial importance in providing a simple route to H2 and to acetic acid. C—H activation refers to a class of catalytic reactions in which unactivated C-H bonds are broken. Finally, we look at some organometallic materials. 

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