MECHANISM AND ANION ACTIVATION IN SOLID LIQUID PHASE-TRANSFER REACTIONS CATALYZED BY CYCLOPHOSPHAZENIC POLYPODANDS - COMPARISON WITH CYCLIC ANALOG CROWN ETHERS

A kinetic study of the nucleophilic substitution of the methanesulfonic group by anions (Cl-, Br-, I-, SCN-, C6H5O-, C6H5CH2COO-) catalysed by cyclophosphazenic polypodands has been performed under solid-liquid phase-transfer conditions. The results obtained show that the mechanism of PTC previously found for cyclic ligands (crown ethers, cryptands) also operates in the case of these open-chain ligands: the attack by the anionic nucleophile on the substrate occurs in the organic phase and is' rate determining of the overall process. The nucleophilicity scales found (I- > C6H5O- almost-equal-to SCN- > C6H5CH2COO-; I- > Br- > Cl-) as well as the anion activation are comparable with those found for cyclic crown ethers. This indicates that the anionic reactive species involved are similar in the complexes of both ligands.