Decomposition in the Presence of Small Molecules and Functional Groups

Decomposition in the Presence of Small Molecules and Functional Groups 

Ruthenium olefin metathesis systems are widely recognized as functional group tolerant catalysts, as they react selectively with olefins over ketones, aldehydes. 

Ruthenium metathesis catalysts are known to react with electron-rich olefins Fl2C=C(H)ER (where E is N, O, or S) to give Fischer-type, carbene complexes. These Fischer carbenes are considerably more stable and less active in olefin metathesis than the Grubbs systems, with the order of metathesis activity (E = C N S 0) being the reverse of that of complex stabilities [82]. Thus, the development of ruthenium catalysts capable of efficiently catalyzing the 

Similarly, Fischer carbene complexes are formed when Grubbs systems react with vinyl esters, vinyl carbonates, and vinyl halides. However, these Fischer car-benes are known to decompose to give terminal ruthenium carbide species by elimination of HX (X = OjCR, OjCOR, halide) [83-86]. Notably, the formation of the carbide complexes is less favorable in phosphine-free systems, which enables the Hoveyda [56] and Piers [87] catalysts to promote the cross metathesis of vinyl hahdes and terminal or internal olefins [88]. 

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