Organometallic compounds ring-opening polymerization

Nevertheless, polymerizations other than the anionic ones have also been carried out using enolates as ligands of transition metal cations. Metal acetalyacetonates are indeed organometallic compounds that directly contributed to the control of radical polymerization, ring-opening polymerization and coordination polymerization of specific monomers, as discussed hereafter. 

The ring-opening polymerization of cyclic unsaturated hydrocarbons has been studied extensively(l-4), following the first report by Eleuterio(5 and subsequent discovery of homogeneous catalyst by Natta et al. (6). Typical catalyst is composed of a tungsten or a molybdenum compound and an organometallic compound. 

There are several types of Ziegler-Natta and ROMP catalysts employed for cycloolefin polymerization, the majority of them being derived from transition metal salts and organometallic compounds [4-7]. These types are grouped into unicomponent, binary, ternary, and multicomponent catalytic systems as a function of the presence or absence of the organometallic cocatalyst or other additives, each of them being differentiated on the catalyst composition and selectivity toward vinylic or ring-opened polymerization. 

A wide variety of binary catalysts of both Ziegler-Natta and ROMP type, consisting of group IV-VII transition metal salts associated with organometallic compounds, have been used in cycloolefin polymerization to manufacture high molecular weight vinylic and ring-opened polymers [4-7]. The activity and selectivity of these catalytic systems depend mainly on the nature of the transition metal and the structure of cycloolefin. 

Dimethyleneoctahydronaphthalene has been polymerized by a great variety of Ziegler-Natta and ROMP catalysts based on transition metal salts of titanium, zirconium, vanadium, molybdenum, tungsten, ruthenium, iridium, osmium, platinum or palladium and organometallic compounds [159]. Depending on the catalyst employed, addition or ring-opened polymers were preferentially formed [Eqs. (99) and (100)]. 

A great number of norbornene-like monomers [e.g., m = 1-3, R] and R2 = alkyl and aryl groups, Eqs. (103) and (104)] with or without substituents have been employed in polymerization reactions induced by Ziegler-Natta and ROMP catalysts derived from ruthenium, osmium, iridium, palladium, platinum, molybdenum, and tungsten halides or vanadium and zirconium halides or acetylacetonate associated with organometallic compounds [162, 163]. Both addition and ring-opened polymers have been obtained by this way depending on the catalyst employed [Eqs. (103) and (104)]. 

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