Stereochemical Aspects of ADMET

The stereochemical outcome of the metathesis reaction in ADMET with Grubbs catalysts determines the ratio of cis and trans olefins in the polymer, which affects the physical properties of the polymer. In addition, consideration of the formation of metallacyclobutane shows that a great majority of the metathesis events in an ADMET reaction are non-productive, and it is the occurrence of the less favored pathways that cause productive ADMET. 

This preference is not energetic enough to prohibit ADMET, however, and increasing the temperature of the reaction will reduce the preference for the a,a -(Jisubsti-tuted olefins. This may be one factor in the temperature dependence of the rate of ADMET of 1,9-decadiene. The Arrhenius plot for the polymerization of 1,9-decadiene with complex 6 or complex 10 is not hnear (Eig. 6.5), especially for complex 10, indicating that there are more than one temperature-dependent processes occurring, which probably include decomposition, phosphine dissociation, inherent metathesis activities of the Ij species, and ratio of productive and non-productive metathesis. 

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