Iodine-Induced Stepwise Reactivity of Coordinated White Phosphorus: a Mechanistic Overview

The main role of the Ruthenium metal in the stepwise demolition of the P4 ligand upon the reaction with I2 is to enhance the basicity of the phosphorus atoms. The first step of reaction goes through the ?2 coordination of the P4 moiety. The bounded phosphorus atoms are able to interact with the di-iodine molecule allowing the formation of tri-iodide anions. The latter, once released, may exert their nucleophilic action toward the transient unsaturated coordinated phosphorus centre. Such a vacancy is partially fulfilled by the metal through the formation of a partial Ru=P double bond. A detailed analysis of the evolution of the electronic structure at the various intermediates allows to discriminate in between the possible different initial adducts and to predict the most stable product. In contrast with the unassisted reaction, no concerted mechanism has been pointed out but the process evolves through a stepwise cleavage of the three P-P bonds involving the coordinated phosphorus up to the final PI3 ligand formation and a cyclo-P3I3 moiety.