Ionic properties of the triethylaluminum and stannic cloride system as stereospecific polymerization catalyst for vinyl isobutyl ether

Polymerization of vinyl isobutyl ether was investigated with the catalytic system triethylaluminum and stannic chloride. The poly(vinyl isobutyl ether) obtained with an equimolar mixture of triethylaluminum and stannic chloride possessed the highest isotacticity. Measurement of the heat of reaction between triethylaluminum and stannic chloride and determination of the gas evolved on hydrolysis of this catalytic system showed that the reaction product of an equimolar amount of triethylaluminum and stannic chloride is an equimolar mixture of aluminum chloride and triethyltin chloride. Cryoscopic measurements and NMR studies indicated definitely that aluminum chloride and triethyltin chloride are highly associated in benzene. Furthermore, the 1:1‐mixture of triethylaluminum and stannic chloride exhibited remarkably high electric conductivity even in a non‐polar solvent like toluene. In the electrolysis of this catalytic system in toluene, both aluminum and tin compounds were deposited at both electrodes. These results lead us to the concept of the formation of multiple ions such as in favor of the hypothesis of the multi‐center catalyst in stereoregular polymerization, previously proposed by us.