Polymerization isomerism coordination compounds

The ability of complexes to catalyze several important types of reactions is of great importance, both economically and intellectually. For example, isomerization, hydrogenation, polymerization, and oxidation of olefins all can be carried out using coordination compounds as catalysts. Moreover, some of the reactions can be carried out at ambient temperature in aqueous solutions, as opposed to more severe conditions when the reactions are carried out in the gas phase. In many cases, the transient complex species during a catalytic process cannot be isolated and studied separately from the system in which they participate. Because of this, some of the details of the processes may not be known with certainty. 

In fact, Werner played such a central and almost monopolistic role in coordination chemistry that his name is virtually synonymous with the field. Even today, almost 75 years after his death in 1919, coordination compounds, particularly metal-ammines, are still colloquially called Werner complexes. The coordination theory not only provided a logical explanation for known "molecular compounds, but also predicted series of unknown compounds, whose eventual discovery lent further weight to Werner s controversial ideas. He showed how ammonia could be replaced by water or other groups, and he demonstrated the existence of transition series between ammines, double salts, and hydrates. Werner recognized and named many types of inorganic isomerism such as coordination isomerism, polymerization isomerism, ionization isomerism, hydrate isomerism, salt isomerism, coordination position isomerism, and valence isomerism. He also postulated explanations for polynuclear complexes, hydrated metal ions, hydrolysis, and acids and bases. His view of the two types of chemical... 

Figure 4.12 has interesting properties, as it displays two distinct Amax at 405 and 480 mn [DIE 91], In the presence of a,P-unsaturated compounds and subsequent to irradiation, an exchange of ligands is followed by isomerization to a coordinative unsaturated complex. The complex is a biradical that is capable to initiate the polymerization of unsaturated monomers [FIN 89]. 

Organic compounds with multiple bonds in the presence of complexes containing transition metals (Ti, Rh, W, Mo, Re, Ni, and ofhos) can rmdergo various transformations to afford polymeric, oligomeric, and isomeric products. Despite a variety of catalytic mechanisms, these processes are characterized by several general properties including the stages of formation of low-valence coordinationally unsaturated intermediates, coordination of unsaturated bonds, and intracomplex insertion. In many cases, the activation of the intermediate complex occurs due to the alkylation of the central metal atom. 

---