Département de chimie moléculaire

PtII-catalyzed cycloisomerization of a 1,6-enyne proceeds quickly in CHCl3 at room temp., and also in the gas phase. However, calcns. predict a slow reaction, because of the formation of a very stable chelate that undergoes oxidative cyclization at a high energy cost. The electrophilic activation of the alkyne followed by nucleophilic attack of the double bond to generate a cyclopropyl carbene would lead to a faster reaction, but the decomplexation of the double bond to generate an unsatd. platinum species is also energetically disfavored. However, decomplexation can be envisaged if an adventitious mol. of water enters the coordination sphere of the metal. This crucial role of water in PtII-catalyzed cycloisomerization of enynes, initially sensed some years ago is now supported by mass spectrometry studies. [on SciFinder(R)]