Diverse Reactivity of an Electrophilic Phosphasilene towards Anionic Nucleophiles: Substitution or Metal–Amino Exchange

The reaction of MesLi (Mes=2,4,6‐trimethylphenyl) with the electrophilic phosphasilene R₂(NMe₂)Si‐RSi=PNMe₂ ( 2 , R=Tip=2,4,6‐triisopropylphenyl) cleanly affords R₂(NMe₂)Si‐RSi=PMes and thus provides the first example of a substitution reaction at an unperturbed Si=P bond. In toluene, the reaction of 2 with lithium disilenide, R₂Si=Si(R)Li ( 1 ), apparently proceeds via an initial nucleophilic substitution step as well (as suggested by DFT calculations), but affords a saturated bicyclo1.1.0]butane analogue as the final product, which was further characterized as its Fe(CO)₄ complex. In contrast, in 1,2‐dimethoxyethane the reaction of 1 with 2 results in an unprecedented metal–amino exchange reaction.