Factors Affecting the Unusual Reactivity Order in the β-Hydrogen Abstraction of Dialkylzirconocenes

Competitive β-hydrogen abstraction of “mixed” dialkylzirconocenes and kinetic measurements of decomposition of methyl(alkyl)zirconocenes reveal unexpected relative reactivity of alkyl groups as β-hydrogen donors, such as s-Bu > t-Bu ≥ Et > n-Bu > i-Bu, which correlate well in most cases with the reactivity order of: β-methyl > β-methylene > β-methine. Some mechanistically crucial features of the reaction are also discussed.