Ambident Reactivity of (Selenocarbamoyl)Phosphines: Transformation into a Crystalline (Phosphino)(Seleno)Iminium Salt and Transition-Metal Complexes.

Although various types of selenoamides have already been developed, examples of derivatives bearing a third heteroatom that acts as a second reactive center have remained limited so far. Recently, we reported the synthesis, structure, and fundamental reactivity of (selenocarbamoyl)phosphines, which exhibit ambident reactivity at two principal sites, i.e., the phosphorus and selenium atoms, in reactions with electrophiles. Herein, we report the synthesis of the first crystalline (phosphino)(seleno)iminium salt from a (selenocarbamoyl)phosphine, as well as the double-functionalization of (selenocarbamoyl)phosphines. Notably, the critical importance of the selenium atom for chalcogen-selective methylation was corroborated by a combined experimental and theoretical comparison with its sulfur analogue. Furthermore, the transition-metal complex of a (selenocarbamoyl)phosphine, whose phosphorus and selenium atoms were modified to give the phosphine selenide and the palladium complex, was obtained as a double-functionalized product.