Mechanistic discussion and conclusion

The catalytic cycle involved in the Stille coupling reaction is generally accepted to involve the following steps  

formation of an active palladium species bearing two ligands ( PdL2 )  

2 oxidative addition of the organic moiety RX to palladium to give RPdXL2  

reaction with R SnR 3 to form a species with an R-Pd-R linkage and R 3SnX  

reductive elimination to give R-R and regenerate the active palladium species. 

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