Autoxidation of alkyl compounds of zirconium and hafnium

Abstract

Autoxidations of alkylzirconocenes of the type Cp₂ZrR₂ and Cp₂Zr(R)X (Cp =π-cyclopentadienyl; R = methyl, benzyl, or substituted benzyl; X = Cl or Br) have been shown to be free-radical chain reactions involving an S_H2-type displacement of an alkyl radical from the metal centre by an alkylperoxyl radical. These autoxidations have been related to those of the tetra-alkyl compounds of the Group IVA metals. The propagation rate constants (k_p) together with the corresponding entropies and enthalpies of activation have been measured for the dibenzyl-zirconocenes.