Monomers chelate type

Chelate-Type Monomers in Copiolymeiization with Conventional Monomers... 150... 

From our point of view [8], the most effective classification is based on the type of bond between the metal and the organic part of the monomer molecule. On this principle, MCMs can be classed into the following major types monomers with a covalent, ionic, donor-acceptor, chelate and Ji-bound metal (Fig. 4-1). 

While the types of MCMs described earlier have already received comparatively wide popularity in polymerization practice, polymers based on metal-containing monomers of the chelate type have only been prepared more recently. The methods of assembly of such MCMs, i.e. the simultaneous formation of the ligand and the corresponding complex, have been substantially developed. The synthesis of MCMs from /7-aminostyrene, 2-formylpyrrole and Cu(II) or Co(III) salts is an example of such a method. The last approach is especially characteristic of the preparation of MCMs with macrocyclic chelate nodes, in particular, from porphyrins, phthalocyanines and other macrocycles with exocyclic multiple bonds. It is worth noting that traditional methods of chelation are used for preparing MCMs when scientists want to ensure strong multicenter fixation of metals into monomer molecules, and, thus, into (co)polymers. 

These are the same chelate-type MCMs, but with tetradentate coordination (Table 4-1). Moreover, MCMs with a small strained structure (vinylimine, epoxide) have already been considered above. By considering MCMs with macrocycles in a separate section, we wish to focus attention on monomers of this type because of their widespread use in polymerization practice, especially, porphyrin and phthalocyanine derivatives. As we know, such macrocycles are n-conjugated planar tetradentate ligands and capable of forming rather stable chelates with almost all metals. A basic method of MCM synthesis is based on the incorporation of metal ions into a window of macrocycles completed by an exocyclic multiple bond [45 8]. Examples are 74-76. 

Calcium Chelates (Salicylates). Several successhil dental cements which use the formation of a calcium chelate system (96) were developed based on the reaction of calcium hydroxide [1305-62-0] and various phenohc esters of sahcyhc acid [69-72-7]. The calcium sahcylate [824-35-1] system offers certain advantages over the more widely used zinc oxide—eugenol system. These products are completely bland, antibacterial (97), facihtate the formation of reparative dentin, and do not retard the free-radical polymerization reaction of acryhc monomer systems. The principal deficiencies of this type of cement are its relatively high solubihty, relatively low strength, and low modulus. Less soluble and higher strength calcium-based cements based on dimer and trimer acid have been reported (82). 

The reaction of copper(II) acetate with ethyl aminomethylene cyanoacetate of type H2(L22) (55) provides highly stable polymer 1Cu(L22) (56). The supra-molecular 2D geometry of 56 depends basically on the lateral groups of the chelate ligand. The two cyano donors of monomer [Cu(L22)] (57) coordinate differently, with the result that 56 is rather composed of zig-zag-lD-strands, linked among each other to give a 2D-network (Scheme 21) [167]. 

The dissociation of the dimer [Cp 2Y(/i-H)]2 to the Cp 2YH monomer is an important process in the reactions of the dimer with alkenes. The kinetics and formation of yttrium alkyl complexes from [Cp 2Y(//-I I)]2 and alkenes have been investigated.587 In situ prepared dimeric bis(pentamethylcyclopentadienyl)yttrium hydride reacted rapidly with 3,3-dimethyl-l,4-pentadiene in methylcylohexane-r/ at — 78 °C and formed a bright yellow solution of the t/°-yttrium(m)pentenyl chelate complex Cp 2Y[7/,7/2-CI I2CI I2CMc2CI I=CH2] in 98% yield (Scheme 130). This pentenyl chelate complex was also prepared in toluene-// in 84% yield. The chelate complex was stable for about 2 weeks at — 78 °C but decomposed after a few hours at —50 °C. The complex was characterized without isolation by 1H and 13C NMR spectroscopy at —100 °C such complexes can be regarded as models for the coordination of alkenes to lanthanide and isoelectronic grouop 4 polymerization catalysts.588 Agostic interactions in yttrium alkyls of the type... 

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