The isolation and crystallographic characterization of various reactive intermediates such as molecular p-complexes, carbocations, cation radicals, etc. had substantial bearing on our current understanding of the mechanisms of the electrophilic additions to the olefinic bonds, electrophilic aromatic substitution, and a variety of other oxidation-reduction reactions. However, we recognize that, in general, it is not feasible to characterize these reactive intermediates by isolation due to the very rapid subsequent reactions; and the problem is further complicated because of the coexistence (and the rapid interconversion) of various s- and p-complexes as well as of the diamagnetic carobocation and paramagnetic cation radicals in various electrophilic reactions.
By a careful design of substrates, we have successfully isolated and characterized a variety of s- and p-complexes, carobocations, and cation radicals intermediates, derived from aromatic and olefinic donors. by X-ray crystallography. The X-ray structures of a few of these intermediates are depicted below:
We are constantly designing new molecules for the study of electron-transfer reaction mechanisms of a variety of reaction types by isolation of reactive intermediates for X-ray crystallographic characterization.