Solvent Effects
The choice of solvent can play a vital role in the formation of the carbene species. One example of such interactions was reported by Basset, et al. regarding RuCl3 and the effects of various alcohols on its catalytic activity. Depending upon the alcohol used, the mechanistic pathway resulted in either a reactive ruthenium-hydride species or the formation of a ruthenium-carbene. Experimental results demonstrated that by altering the solvent, the molecular weight of the polymer produced was either increased or decreased. This observation could result in increased diversity of the catalytic system enabling the production of polymers of various strengths, as polymers with higher molecular weights are typically stronger than polymers of low molecular weights. Drastic differences in the rate of the reaction were also observed, thereby supporting the conclusion that the solvent plays a role in the formation of the ruthenium-carbene.
Hamilton, et al. report that altering the solvent in metal salt-type catalytic systems can drastically change the microenvironment of the system; these changes affect the tacticity of the polymer, the cis-trans ratio, and can increase the regularity of copolymers.
Read more about this topic: Ring Opening Metathesis Polymerisation
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