1H and 2H NMR Spectroscopic Characterization of Heterobinuclear Ion Pairs Formed upon the Activation of Bis(imino)pyridine Vanadium(III) Precatalysts with AlMe3/[Ph3C]+[B(C6F5)4]− and MAO

Abstract

Until recently, attempts to characterize vanadium(III) species formed upon the activation of vanadium(III) α-olefin polymerization precatalysts with AlMe3/[Ph3C]+[B(C6F5)]4– or MAO were unsuccessful. In this contribution, 1H and 2H NMR spectroscopy was used to study the activation of bis(imino)pyridine vanadium(III) chloride LVIIICl3 {L = [2,6-(ArN═CMe)2C5H3N], Ar = 2,6-iPr2C6H3; 2,6-Me2C6H3; 2,4,6-Me3C6H2; 3,5-F2C6H3} with AlMe3/[Ph3C]+[B(C6F5)]4– or MAO. Formation of heterobinuclear ion pairs of the type [L(R)VIII(μ-R)2AlMe2]+[A]− ([A]– = [B(C6F5)]4– or [MeMAO]−, R = Me or Cl) was observed, which are the most likely direct precursors of active sites of ethylene polymerization.