Remote Activation of Nickel Catalysts for Ethylene Oligomerization

摘要

An important consideration in the design of homogenous transition-metal initiators for the oligomerization and polymerization of olefins concerns the mode of activation. While neutral initiators are becoming increasingly available,[1] the majority are cationic species generated upon addition of a strong Lewis acid, in the presence or absence of an alkylating agent, to a neutral organometallic precursor. The most typical activators are alkylaluminoxanes[2] and well-defined Lewis acids, such as B(C6F5)3.[3] For example, B(C6F5)3 reacts with [Cp2ZrMe2] (Cp=C5H5) to give [Cp2ZrMe(MeB(C6F5)3)].[4] The dynamics of the resulting cation/anion pair, such as dissociation equilibria or the ability of the olefin to displace the anion, are important in determining the availability of the active site and the overall reactivity towards the unsaturated organic substrate.