[ReO3(bipy)]+[X]--catalyzed aldehyde olefination: carbene and phosphorane intermediates.

The aldehyde olefination reaction, catalyzed by cationic high-valent oxorhenium complexes, shows evidence of the intermediacy of both carbene complexes and phosphoranes. The solution-phase reaction is facile and amenable to tuning and is, hence, likely to prove to be of practical significance. Individual steps in the catalytic cycle are observed in the gas phase. Catalytic competence of each of the putative intermediates can be demonstrated.