Theoretical Evidence for the Utilization of Low-Valent Main-Group Complexes as Rare-Synthon Equivalents.

We examine by the means of computational chemistry the ability of two phosphasilenes to transfer the phosphinidene moiety to four double bonded organic functional groups (>C=C<, -N=N-, >C=O, and >C=S) in the presence of different bulky ligands. We show that large bulky groups in the reactants can sterically prohibit the otherwise favored association of reactants and phosphasilenes and instead a new phosphinidene transfer reaction can occur. We find that the transfer reaction mechanism is generally present independent from the functional group and by introducing large enough trimethylsilyl or tert-butyl-dimethylsilyl ligands it can be used to transfer phosphinidene to organic functional groups such as thioformaldehydes or diazenes, respectively. We propose that by exploiting the complex bonding nature of low-valent main group complexes they can act as synthetic equivalents of hitherto unknown very reactive synthons. We encourage experimentalists to explore the reactivity of their main-group complexes by varying the size of the bulky substituents on the reactants that can result in new unexpected chemistry.