Ambireactive (R₃ P)₂ BH₂ Groups Facilitating Temperature-Switchable Bond Activation by an Iron Complex

Area of Science:

• Organometallic Chemistry
• Catalysis
• Iron Complexes

Background:

• Pincer complexes are crucial in catalysis due to their unique coordination environment.
• Controlling reactivity through external stimuli like temperature is a key challenge in catalyst design.
• Hemi-labile ligands offer tunable electronic and steric properties for catalytic applications.

Purpose of the Study:

• To investigate the temperature-dependent reactivity of a novel iron pincer complex.
• To elucidate the mechanisms behind switchable B-H and C-H activation pathways.
• To develop an iron-catalyzed protocol for H/D exchange in organic solvents.

Main Methods:

• Synthesis and characterization of the iron pincer complex featuring a (R3P)2BH2 ligand.
• Variable-temperature studies to observe reactivity changes.
• Mechanistic investigations including kinetic and spectroscopic analyses.
• Development and testing of the H/D exchange protocol.

Main Results:

• The iron complex exhibits reversible B-H activation and P-B bond cleavage at room temperature.
• Below 4°C, intra- and intermolecular C-H activation become dominant reaction pathways.
• Ligand lability and exothermic sigma-bond formation drive the switchable bond activation.
• An efficient iron-catalyzed H/D exchange of organic solvents was achieved without oxidants.

Conclusions:

• The hemi-labile (R3P)2BH2 ligand enables temperature-switchable reactivity in iron pincer complexes.
• Understanding these mechanisms allows for precise control over catalytic pathways.
• This work provides a new method for H/D exchange catalysis using earth-abundant iron.