Silicon-Phosphorus Analogies the Mechanism of Nucleophilic Substitution at Silicon and Phosphorus Activated by External Nucleophiles Extension of Coordination of the Reactive Species

A comparison is made concerning the mechanism of SN2 reactions of silicon and phosphorus compounds, catalyzed by nucleophiles. The rate-law of the catalyzed solvolysis of halogenophosphorus esters corresponds to a mechanism with extension of coordination of the reactive species. The overall inversion observed with chlorophosphonates affords a distinction between a nucleophilic activated substitution SNA (P) and a nucleophilic double displacement at phosphorus.