Round-Trip Oxidative Addition, Ligand Metathesis, and Reductive Elimination in a P^III/P^V Synthetic Cycle

Abstract

A synthetic cycle for aryl C−F substitution comprising oxidative addition, ligand metathesis, and reductive elimination at a C s -symmetric phosphorus triamide (1, P{N[o-NMe-C 6 H 4 ] 2 }) is reported. Reaction of 1 with perfluoroarenes (Ar F − F) results in C−F oxidative addition, yielding fluorophosphoranes 1•[F][Ar F ]. The P-fluoro substituent is exchanged for hydride by treatment with DIBAL-H, generating hydridophosphoranes 1•[H][Ar F ]. Heating of 1•[H][Ar F ] regenerates 1 by C−H reductive elimination of Ar F −H, where experimental and computational studies establish a concerted but highly asynchronous mechanism. The results provide well-characterized examples of the full triad of elementary mechanistic aryl C−X substitution steps at a single main-group site.

Catalytic Hydrodefluorination via Oxidative Addition, Ligand Metathesis, and Reductive Elimination at Bi(I)/Bi(III) Centers

“…In this regard, C–F OA has been established for low-valent group 13/14 elements, 14 and recently Radosevich has further shown an elegant synthetic cycle for HDF at a phosphorus triamide. 15 Herein, we report that bismuthinidenes with a rationally designed N,C,N -pincer ligand scaffold unlock the catalytic HDF of a variety of polyfluoroarenes ( Figure 1 C). Mechanistic studies suggest a Bi(I)/Bi(III) cycle comprising C–F OA, F/H LM, and C–H RE steps, in a manner akin to a canonical catalytic cycle of transition-metal congeners.…”

Bismuth Redox Catalysis: An Emerging Main-Group Platform for Organic Synthesis

“…These three elementary steps, OA, LM, and RE, are akin to those in a well-defined P(III)/P(V) synthetic cycle for HDF previously demonstrated by Radosevich. 61 While a catalytic OA/LM/RE cycle in a Pn(III)/Pn(V) manifold is considered yet challenging, the Bi(I)/Bi(III) redox cycle has enabled a catalytic cycle of such sequence by a main group complex, which is conventionally confined to TM catalysis.…”

Navigating through the Maze of Homogeneous Catalyst Design with Machine Learning

“…However, not only the metals but also the metalloids and nonmetals are enjoying increased interest. Notably, phosphorus compounds were recently shown to catalyze C-N coupling reactions [113] and undergo both oxidative additions and reductive eliminations in stoichiometric experiments demonstrating potential as catalysts [114]. Main challenges include the design of the coordination sphere of the main-group element to stabilize active catalysts.…”