1.3.5- Hexatrienes palladium complexes

Transmetallation is not restricted to palladium and has been extended to rhodium and copper, so far. [(CODjRhClJj promotes the room-temperature JKOcycli-zation of cross-conjugated chroma- and tungsta-amino-l-metalla-l,3,5-hexatrienes with alkynes to give vinylcyclopentadienes as single isomers [96]. Alternatively, vinylcyclopentadienes are also formed from l-alken-3-ynes and 4-amino-l-metalla-1,3-butadiene complexes of chromium and tungsten RhClj 3 HjO in methanol turns out to be the most efficient (pre)catalyst (Scheme 11.44) [97]. 

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