Organolanthanide-Mediated Silanolytic Chain Transfer Processes. Scope and Mechanism of Single Reactor Catalytic Routes to Silapolyolefins

Abstract

This paper reports efficient and selective silanolytic (PhSiH3, n-BuSiH3, C6H5CH2SiH3) chain transfer in organolanthanide-catalyzed homogeneous ethylene polymerization and ethylene copolymerization with several α-olefins. The result is a series of silyl-capped polyolefins which have been characterized by 1H/13C NMR and IR spectroscopy as well as by GPC. In [(Me5C5)2LnH]2/[Me2Si(Me4C5)2LnH]2-mediated ethylene homopolymerization and ethylene copolymerization, both primary arylsilanes (PhSiH3) and alkylsilanes (n-BuSiH3, C6H5CH2SiH3) function as efficient chain-transfer agents. In the case of ethylene polymerization mediated by [(Me5C5)2SmH]2, the mechanism of chain transfer is supported by the observation that Mn of the capped polyethylenes formed at constant [catalyst], [PhSiH3], [ethylene] is inversely proportional to [PhSiH3]. Using silane-activated Me2Si(Me4C5)2LnCH(SiMe3)2 precatalysts, this chain-transfer process also efficiently produces silyl-endcapped ethylene + 1-hexene copolymers and ethylene + styrene copolymers.