Kinetic model of olefin hydroalumination by HAlBui2 and AlBui3 in the presence of Cp2ZrCl2 catalyst

The mechanism of α-olefin hydroalumination by HAlBui2, ClAlBui2, and AlBui3 in the presence of Cp2ZrCl2 catalyst has been studied. It was established that the key intermediate of the reaction is a bimetallic complex [Cp2ZrH2 · ClAlBui2]2, which reacts with olefins and yields higher diisobutylalkylalanes. In parallel with this stage, the key complex can readily react with XAlBui2 (X = H, Cl, Bui) and form a stable trihydride complex Cp2ZrH2 · ClAlBui2 · HAlBui2, which does not exhibit reactivity in olefin hydroalumination. A kinetic model of α-olefin hydroalumination with HAlBui2 and AlBui3 has been developed. The model explains the causes of the low stability of the key intermediate [Cp2ZrH2 · ClAlBui2]2 and of the different activities of organoaluminum compounds (OACs) in the olefin hydroalumination reaction. Moreover, the model gives information about the limit stages of the reaction and explains the influence of the length of the initial olefins on the rate of the whole catalytic process. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 333–339, 2007