Ligand Enabled Disproportionation of 1,2‐Diphenylhydrazine at a P(V)‐Center

Abstract
We present herein the synthesis of a nearly square‐pyramidal chlorophosphorane supported by the tetradentate bis(amidophenolate) ligand, N,N′‐bis(3,5‐di‐tert‐butyl‐2‐phenoxy)‐1,2‐phenylenediamide. After chloride abstraction the resulting phosphonium cation efficiently promotes the disproportionation of 1,2‐diphenylhydrazine to aniline and azobenzene. Mechanistic studies, spectroscopic analyses and theoretical calculations suggest that this unprecedented reactivity mode for PV‐centres is induced by the high electrophilicity at the cationic PV‐center, which originates from the geometry constraints imposed by the rigid pincer ligand, combined with the ability of the o‐amidophenolate moieties to act as electron reservoir. This study illustrates the promising role of cooperativity between redox‐active ligands and phosphorus for the design of organocatalysts able to promote redox processes.

An unprecedented P‐based catalyst able to promote hydrazine disproportionation has been synthesized. The available set of experimental results and theoretical calculations suggest that this reactivity is unlocked by the cooperation between a redox‐active bis(amidophenolate) ligand and the highly electrophilic central P‐atom.

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