From triphenylbismuthine and diazo compounds

In 1967, Lloyd et al. claimed the first synthesis of a bismuthonium ylide by heating triphenylbismuthine and diazotetraphenylcyclopentadiene at 140°C. However, experimental details confirming the product are not available [67CC1042, 88JCS(P2)1829], Thermogravimetric analysis of the reaction shows that the carbene, cyclopentadienylidene, is formed at the initial step [72CC912]. 

Bis(hexafluoroacytylacetonato)copper is reported to be an effective catalyst for the preparation of bismuthonium ylides from triphenylbismuthine and diazo compounds [88S319]. 

When a mixture of diazotetraphenylcyclopentadiene and triphenylbismuthine was heated to 140°C under nitrogen, triphenylbismuthonium tetraphenylcyclopentadienylide resulted as a deep blue product (m.p. 195°C, decomp.), which dissolved in ether and precipitated on addition of light petroleum [67CC1042]. 

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