Secondary syndiotactic-specific propene insertion in the presence of homogeneous V-based catalysts

Abstract

This paper shows, by terminating the polymerization through deuterolysis with CF 3CH 2OD, that the propyl end groups of syndiotactic polypropylene obtained in the presence of homogeneous catalysts, based on vanadium salts and alkylaluminium halides, such as VCl 4–Al(C 2H 5) 2Cl–Anysole, arise, at least mostly, from termination, thus confirming the Coleman–Fox type of the statistical model of the propagation already proposed in previous papers. Direct evidence is also provided that secondary insertion of propene is the only syndiotactic specific polymerization step. In view of this, the early hypotheses concerning the structure of the active species promoting syndiotactic specific polymerization are critically reconsidered.