Reactivity of organometallic compounds and polarizability effect

• The reactivity of organometallics (25 series) has been analysed.
• The log k values of reactions depend on the polarizability effect (Pol) of substituents.
• The reason of Pol is the excess charge on the reaction centre in transition state.
• The presence or absence of Pol is dictated by the type of series.

An elucidation of the factors determining the magnitude of the rate constants, k, is of primary importance in understanding organometallic reactivity. Nevertheless, the influence of substituents bound to the reaction centre on the k is poorly understood. In this work, the literature data on substituent influence on the log k values of reactions involving derivatives of Groups 5–10, 12–14, 16 elements (there are 25 series, in each of them the reaction centre being fixed, and the substituents varying in properties) have been analyzed, using the correlation analysis. Generally not only classic inductive, resonance, and steric effects, as well as the polarizability one have been first established to operate. The presence or absence of certain effects are dictated by the type of series. The polarizability effect is caused by a partial charge appearing on the reaction centre of the activated complex. The contribution of this effect ranges up to 50%. A knowledge of the substituent effects may give a better insight into organometallic reaction mechanisms.

The literature data on the reaction rate constant of reactions involving derivatives of Groups 5–10, 12–14, 16 elements have been considered. The log k were first established to depend not only on the inductive and resonance effects but also on the polarizability and steric effects of substituent.Figure optionsDownload as PowerPoint slide