Zur stabilität der komplexen anionen bei der kationischen polymerisation

Abstract

The counterions appearing in the mechanism of the cationic polymerization are able to decay according toand so give rise to termination reactions. For the model systems (C,H,),C"MtXf + , (Mt = B, Al, Sn, P, As, Sb,In, Ti, Fe; X = F, C1, Br) the decay has been investigated by spectroscopic and conductometric methods. The overall decay rate constant k, is hardly influenced by traces of water (cH2,, < mol. 1-I ) and by structure variations of the cation. On the other hand, k, increases by decreasing the concentration of the salt. When the structure is vaned k, increases with decreasing donor strength of the ligands X, the sensitivity of the anion to changes in the ligand sphere increases corresponding to the ionization potential of the central atom Mt. Addition of tetracyanoethylene raises the stability of the anions. The results can be. explained by the HSAB principle and fit well in a scheme of stabilization of anions by acceptors.

New telechelic polymers and sequential copolymers by polyfunctional initiator‐transfer agents (inifers). XIII. Influence of lewis acid strength and counteranion stability on the synthesis of telechelic polyisobutylenes

“…Evidently Lewis acid strength and counteranion stability control the course of inifer-initiated isobutylene polymerization. These largely unanticipated observations can be explained by extending the Kennedy-Smith model by considering the role of counteranion stability conceived by Heublein et al 5 Thus it is proposed that the interaction between Lewis acid and initiator controls ion generation:…”