Reactivity scale for sizeable molecules

Abstract

With a view to evaluating easily the reactivities of an atom or a functional unit in sizable molecules, we define a reactive orbital that is localized around the reaction site. We represent first the characteristics of a reaction by choosing a certain reference orbital function. Then, by projecting it onto the occupied or unoccupied MOs of a molecule, we can generate the reactive orbital that has the maximum amplitude on that reference orbital function. The occupied or unoccupied orbital obtained in this manner for a sizable molecular system interprets the local electron-donating or -accepting ability of an atom or a functional unit. A combination of local electrophilicity and nucleophilicity of the reagent and reactant molecules gives rise to a new reactivity scale. Applications to two types of reaction are shown to give excellent agreement with experimental results. The electronic effect of ligands on the catalytic activities of Pd complexes in the model Wacker process and the activation of a carbene upon co-ordination to transition metals are also discussed.