Polymerization metal-complex-catalyzed

Butadiene) Group 4 metal complexes and (allyl) complex systems derived thereof have also been suggested as reactive intermediates at various homogeneous Group 4 metal complex-catalyzed conjugated diene polymerization reactions.151... 

Metal-Complex-Catalyzed Reactions 383 Ring opening metathesis polymerization in SCCO2... 

Because various important industrial organic processes utilize olefins, convenient methods to convert olefins into various products are vital. Transition metal catalysts with proper ligands have proved most useful in controlling the course of these reactions. Transition metal complexes catalyze skeletal isomerization, double bond isomerization, polymerization, and other processes. Insertion of a terminal olefin into a transition metal hydride bond by 1,2-inserfion or... 

Transition metal complex catalyzed ring-opening polymerization is fairly general and many other types of ferrocenylsilanes have also been polymerized by this methodology. For example, ferrocenophanes containing acetylide substituents as well as etheroxy substituents have been polymerized by the use of Karstedt s catalyst (platinum-divinyltetramethyldisiloxane complex) (Fig. 8.25) [56]. 

A number of reviews with relevant material address K-complexes of various kinds and iiKlude reviews on the syntheses of cationic 7t-complexes of the transition metals, die activation of C-C bonds in unsaturated hydrocarbons by metal complexes, a review on phosphorus heterocycles and phosphorus analogues of unsaturated hydrocarbon transition metal n-omiplexes J metal-complex catalyzed polymerizations of a-alkenes, coordination equilibria and coupling leactitms of unsaturated hydrocarbons at a metal centre, oligomerization of a-alkenes to higher oligomers, an annual survey on the chemistry of selected n-complexes for the year 1989, an annual survey on the chemistry of ferrocene for the year 1989, and in a number of articles in a journal issue devoted to alkene metathesis. 

Cyanoacrylate adhesives cure by anionic polymerization. This reaction is catalyzed by weak bases (such as water), so the adhesives are generally stabilized by the inclusion of a weak acid in the formulation. While adhesion of cyanoacrylates to bare metals and many polymers is excellent, bonding to polyolefins requires a surface modifying primer. Solutions of chlorinated polyolefin oligomers, fran-sition metal complexes, and organic bases such as tertiary amines can greatly enhance cyanoacrylate adhesion to these surfaces [72]. The solvent is a critical component of these primers, as solvent swelling of the surface facilitates inter-... 

A range of rare earth metal complexes were subsequently shown to catalyze ethylene polymerization and, on occasion, living characteristics have been reported.226-228 Dimeric hydrides such as (79)—(82) are extremely active with turnover numbers > 1800 s-1 recorded for (79) at room temperature. The samarium hydride (82) also effects the block copolymerization of methyl methacrylate (MMA) and ethylene 229 further discussion may be found in Section 9.1.4.4. 

Like all controlled radical polymerization processes, ATRP relies on a rapid equilibration between a very small concentration of active radical sites and a much larger concentration of dormant species, in order to reduce the potential for bimolecular termination (Scheme 3). The radicals are generated via a reversible process catalyzed by a transition metal complex with a suitable redox manifold. An organic initiator (many initiators have been used but halides are the most common), homolytically transfers its halogen atom to the metal center, thereby raising its oxidation state. The radical species thus formed may then undergo addition to one or more vinyl monomer units before the halide is transferred back from the metal. The reader is directed to several comprehensive reviews of this field for more detailed information. 

Some transition metal catalysts induce the living polymerization of various acetylenic compounds.68,69 Such polymerizations of phenylacetylene catalyzed by rhodium complexes are used in conjunction with a quantitative initiation and introduction of functional groups at the initiating chain end (Scheme 16).70 The catalyst is prepared from an [RhCl(nbd)]2/Ph2C=C(Ph)Li/PPh3 mixture and proceeds smoothly to give quantitatively the polymer 54 with a low polydispersity ratio. 

Since the discovery by Ziegler and Natta that transition metal complexes, in the presence of aluminum alkyl compounds, can efficiently catalyze the polymerization of ethylene and propylene, significant efforts have been devoted to the development of new catalytic systems for polymerization of olefins. One of the... 

Reaction rates are macroscopic averages of the number of microscopical molecules that pass from the reactant to the product valley in the potential hypersurface. An estimation of this rate can be obtained from the energy of the highest point in the reaction path, the transition state. This approach will however fail when the reaction proceeds without an enthalpic barrier or when there are many low frequency modes. The study of these cases will require the analysis of the trajectory of the molecule on the potential hypersurface. This idea constitutes the basis of molecular dynamics (MD) [96]. Molecular dynamics were traditionally too computationally demanding for transition metal complexes, but things seem now to be changing with the use of the Car-Parrinello (CP) method [97]. This approach has in fact been already succesfully applied to the study of the catalyzed polymerization of olefins [98]. 

The Cu-complex-catalyzed oxidative polymerization of phenol derivatives has been selected here as a model reaction in which a polymer-metal complex acts as a catalyst. The catalytic cycle is illustrated in Scheme 3, the example used being the oxidative... 

The continuous availability of trillions of independent microreactors greatly multiplied the initial mixture of extraterrestrial organics and hydrothermal vent-produced chemicals into a rich variety of adsorbed and transformed materials, including lipids, amphiphiles, chiral metal complexes, amino add polymers, and nudeo-tide bases. Production and chiral amplification of polypeptides and other polymeric molecules would be induced by exposure of absorbed amino adds and organics to dehydration/rehydration cydes promoted by heat-flows beneath a sea-level hydro-thermal field or by sporadic subaerial exposure of near-shore vents and surfaces. In this environment the e.e. of chiral amino adds could have provided the ligands required for any metal centers capable of catalyzing enantiomeric dominance. The auto-amplification of a small e.e. of i-amino adds, whether extraterrestrially delivered or fluctuationally induced, thus becomes conceptually reasonable. 

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