Macromolecular metal complexes monomer copolymerization

Unfortunately, the aforementioned problems have not been adequately discussed in literature, although there is considerable interest in the preparation of structurally homogeneous macromolecular metal complexes for catalysis, photochemistry, biological applications, etc. This chapter reports on the specificity of the processes for formation of macromolecular complexes through both routes polymerlike transformations and copolymerization of metal-containing monomers. In addition, the predictive potential of reactions and the ways of preventing some of them will be discussed. 

It should be mentioned that simple metal complexes immobilized on polymer supports were initially used for polymerization (1965/1966) in the Solvay catalysts based on titanium complexes bound to macromolecular ligands with C=0, C=N and C=N groups. Until now the data are mainly available in patent literature, and there are few kinetic studies of polymerization processes involving the action of macromolecular complexes. At the same time the use of metal complexes bound to inorganic supports has been extensively developed in polymerization catalysis. This indicates that there has been inadequate study of the application of metal complexes immobilized on polymer supports to the catalysis of polymerization and copolymerization of different monomers, mainly olefins. 

Different valence states are also a fairly widespread type of unit variability. By analogy with macromolecular complexes (Section II), it may be expected that homopolymerization and copolymerization of metal-containing monomers would prevent or retard redox processes involving participation of metal ions. Experimental data confirm the fact that a polymeric matrix stabilizes complexes of metals in low oxidation states (e.g., Pd" ). Moreover, the stability of the Cu+ state during polymerization (including thermal polymerization) of copper acrylate controls the use of this method for the preparation of coordination compounds of Cu". The polymeric framework plays a stabilizing role, whereas the metal ions that are localized on the surface layer are oxidized to Cu +. However, polymerization of monomers that contain metal ions in high oxidation states is often accompanied by their reduction Fe + ->Fe +, and Mo + ->Mo" (scheme 14). For example, polymerization of Cu " and Fe + acrylates may be accompanied by intramolecular chain termination. This may be attributed to the relatively low standard reduction potentials of these metal ions (7io(Cu + Cu+) = 0.15, o(Fe ->Fe ) = 0.77 V). 

Vinyl polymerization using metallocomplexes commonly proceeds by a radical pathway and rarely involves an ionic mechanism. For instance, metal chelates in combination with promoters (usually halogenated hydrocarbons) are known as initiators of homo- and copolymerization of vinylacetate. Similar polymer-bound systems are also known [3]. The polymerization mechanism is not well understood, but it is believed to be not exclusively radical or cationic (as polymerization proceeds in water). The macrochelate of Cu with a polymeric ether of acetoacetic acid effectively catalyzes acrylonitrile polymerization. Meanwhile, this monomer is used as an indicator for the radical mechanism of polymerization. Mixed-ligand manganese complexes bound to carboxylated (co)polymers have been used for emulsion polymerization of a series of vinyl monomers. Macromolecular complexes of Cu(N03)2 and Fe(N03)3 with diaminocellulose in combination with CCI4 are active in polymerization of MMA, etc. 

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