Doubly charged ions, chemical reactions

In conclusion, one should mention that chemical reactions of doubly charged ions leading to doubly charged ions and neutral reaction products have also been detected, i.e., processes... 

Small hydrocarbons, alkanes, and alkenes in particular, are convenient substrates to estabhsh correlations between the electronic configurations of the reactant ions and the reaction products and mechanisms, and were extensively investigated with both singly and doubly charged rare earth and actinide cations. Hydrocarbon activation by metal ions generally proceeds by oxidative insertion into a C—H or C—C bond, as indicated in Eqs. (1) and (2), which requires two chemically active valence electrons at the metal center, such as in C-M -H or C-M" -C intermediates ... 

The principle of hard and soft Lewis acids and bases, proposed by Pearson (1963), is useful to describe these reactions. A Lewis acid is any chemical species that employs an empty electronic orbital available for reaction, while a Lewis base is any chemical species that employs a doubly occupied electronic orbital in a reaction. Lewis acids and bases can be neutral molecules, simple or complex ions, or neutral or charged macromolecules. The proton and all metal cations of interest in subsurface aqueous solutions are Lewis acids. Lewis bases include H, O, oxyanions, and organic N, S, and P electron donors. A list of selected hard and soft Lewis acids and bases found in soil solutions is presented in Table 6.1. 

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