Synthesis and reactivity of molecules containing strained homonuclear element-element bonds

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Radicals are key intermediates in a number of chemical transformations and their reactivity involves two key steps: 1. Radical formation via breaking of a chemical bond, A-B, to give two highly reactive radical species A(dot) and B(dot). This step occurs spontaneously or through the application of energy in the form of heat or light; 2. Termination of the reaction and this involves the formation of a bond between two similar or dissimilar radicals, A(dot) + B(dot) to give A-B. Most of these radical reactions involve transient species. In contrast, there are some known radicals that are stable enough to be placed in a bottle on the shelf. Unfortunately, because of their stability, many of these species are not reactive enough to participate in a number of chemical transformations. However, there are a handful of compounds that contain weak or strained bonds in the solid state that either partially or fully dissociate in solution through breaking of the element-element bond. These form persistent radicals--i.e. a radical that has a very long lifetime, but is not "bottle-able".