One notable exception is diphenylsilane. When adding diphenylsilane to 3 and heating the solution to 80°C, we observe the exchange of the silane moieties on 3 with the free silane in solution (Figure ). This type of reactivity was also observed for other dicobalt complexes in which the silanes are bound in a similar fashion. Despite the observed silane exchange, which should proceed through a dissociative mechanism, productive exchange with other ligands suitable for low valent cobalt such as PMe 3 and benzophenone imine (BPI) led to either no reaction or to decomposition into a complex mixture of species at higher temperatures as described. It seems that this is a general trend for complexes 3 and 4 in which reactions only take place at higher temperatures due to the stability of the base stabilized silylene motif. If at high temperatures a reaction takes place, that temperature may also lead to decomposition of the new product before the reaction is anywhere near completion. This indicates that the motif in 3 and 4 is more stable than the products that may be formed with other ligands. The somewhat remarkable stability of this silicon binding motif is also reflected in the fact that this motif, or variations on it, is encountered for various dinuclear complexes, especially those with noble metals. We reason that the stability of this motif is grounded in the balance between the two important resonance structures discussed above (Scheme 5). Shifting the balance from R1 to R2 provides several degrees of freedom to tailor the electronic characteristics of this motif to the demands of the metal centers, leading to stable structures.