Macrocyclic Copper(II) Complexes as Catalysts for Electrochemically Mediated Atom Transfer.

Area of Science:

• Organometallic Chemistry
• Catalysis
• Electrochemistry

Background:

• Copper-catalyzed electrochemical atom transfer radical addition (eATRA) offers a mild route for C-C bond formation.
• N4 macrocyclic copper complexes are investigated as precatalysts for eATRA reactions.
• Understanding catalyst structure-activity relationships is crucial for optimizing eATRA.

Purpose of the Study:

• To evaluate a series of N4 macrocyclic Cu(II) complexes as precatalysts for eATRA.
• To characterize the structural, spectroscopic, and electrochemical properties of these complexes.
• To correlate complex structure with radical activation and catalytic performance in eATRA.

Main Methods:

• Synthesis and full characterization of N4 macrocyclic Cu(II) complexes.
• Electrochemical studies to determine redox potentials and activation pathways.
• Assessment of catalytic activity in eATRA reactions, monitoring radical production and capture.
• Structural analysis of intermediate organocopper species.

Main Results:

• A series of N4 macrocyclic Cu(II) complexes were synthesized and characterized.
• Varied radical activation reactivity was observed across the complex series.
• The [CuI(Me2py2clen)(NCMe)]+ complex demonstrated rapid radical capture, forming an organocopper intermediate.
• This rapid capture, however, led to catalyst self-termination rather than productive radical addition.

Conclusions:

• N4 macrocyclic copper complexes exhibit diverse reactivity in eATRA.
• Rapid radical capture by organocopper intermediates can accelerate catalysis but may lead to undesired self-termination.
• Further catalyst design is needed to prevent self-termination and achieve efficient eATRA.