One- and Two-Electron Carbon-Halide Bond Activation at a Phosphorus Center

Area of Science:

• Organometallic Chemistry
• Main-Group Chemistry
• Catalysis

Background:

• Transition metal catalysis commonly utilizes d-orbitals for switching between single-electron (1e) and two-electron (2e) reaction pathways.
• Achieving similar reactivity switchability with main-group elements is challenging but highly desirable for developing novel catalytic systems.

Purpose of the Study:

• To investigate the potential of main-group elements, specifically phosphorus, in activating small molecules.
• To develop a phosphorus-centered activation strategy that mimics the versatile reactivity of transition metals.

Main Methods:

• Utilized a metallophosphanorcaradiene complex for phosphorus-atom transfer reactions with various organohalides.
• Analyzed the reaction outcomes to identify distinct activation modes (SN2, SNAr, E2, reductive radical coupling).
• Investigated the electronic structure and orbital interactions within the complex to understand the mechanism of reactivity switching.

Main Results:

• Demonstrated phosphorus-centered selective activation of organohalides through a novel phosphorus-atom transfer reaction.
• Observed four distinct reaction modes: SN2 or SNAr-type substitution, E2 elimination, and reductive radical coupling.
• Showcased switchable 1e and 2e pathways depending on the substrate, mirroring transition metal catalysis.
• Established a modular "P + 2E + Nu" strategy for synthesizing diverse organophosphorus compounds.

Conclusions:

• Developed a main-group phosphorus-based system capable of activating organohalides with switchable 1e/2e pathways.
• This work expands the scope of main-group element reactivity, offering a promising alternative to traditional transition metal catalysis.
• The established phosphorus-atom transfer platform provides a new route for the modular synthesis of complex organophosphorus molecules.