General mechanism of second generation catalysts

Mechanistic studies show that these second generation catalysts mediate olefin metathesis by a mechanism similar to the first generation bis(phosphine) systems 

In other words, the first generation bis(phosphine) catalysts display excellent initiation properties, and conversion of the pre-catalyst (PR3)2(X)2Ru=CHR to the phosphine-dissociated active species (PR3)(X)2Ru=CHR (A where L = PR3) occurs readily. Once A is generated, it binds olefin and undergoes [2 -I- 2] 

Ligand substitution effects in first and second generation ruthenium olefin metathesis catalysts  

Entry Complex ki (relative) k-i/fe (relative) feoMP (relative) 

Transition Metal-Carbene Complexes in Olefin Metathesis 

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