Catalytic metathesis Hoveyda-type complexes

These studies were extended to the Hoveyda-Grubbs type complexes [59]. Here, Verpoort and coworkers compared the catalytic activity of unsymmetrical complexes 74-79 with the classical Hoveyda-Grubbs complexes 3 and 11 (Figure 11.15). However, no improvement in activity was observed in any of the tested metathesis reactions. In this study, the increase of steric interactions led to a significant decrease in activity thus, 79, the most sterically hindered complex, was the least active catalyst for all olefin metathesis reactions tested. 

The examples presented herewith show that tagged Hoveyda-type catalysts can be successfully applied in aqueous media as well as in IL. Substitution of a benzylidene fragment can be used not only to immobilize the organo-metallic complex in such media, but also to increase its catalytic activity by electronic activation. The high stability and good application profiles of such modified catalysts in conjunction with their faeile removal from organic products can be expected to offer new opportunities in green applications of olefin metathesis. 

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