A change in ligand hapticity promotes Lewis base dissociation

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Catalysis

Background:

• Ligand design is crucial for controlling metal complex reactivity.
• Tunable hapticity in ligands offers new avenues for reaction control.
• Reversible substrate coordination is key in catalytic cycles.

Purpose of the Study:

• To introduce and characterize a novel phosphine 1-azaallyl ligand (L2).
• To demonstrate ligand-controlled reversible coordination of Lewis bases.
• To elucidate the mechanism of ligand reorganization and substrate binding/dissociation.

Main Methods:

• Synthesis and characterization of the phosphine 1-azaallyl ligand L2.
• Investigation of palladium methyl complex [Pd(CH3)(L2)] with pyridine.
• Spectroscopic techniques including 13C{1H} and 1H-31P HMBC NMR.
• X-ray absorption spectroscopy (XAS).
• Density-functional theory (DFT) calculations.

Main Results:

• The ligand L2 enables reversible coordination of Lewis bases (e.g., pyridine) by altering its binding mode (hapticity).
• In [Pd(CH3)(L2)], L2 adopts a κ1-P;η3-NCC coordination mode.
• Pyridine binding induces a switch to a κ2-PN mode, facilitating pyridine dissociation upon reversion to the original mode.
• Experimental and computational methods confirmed these interconversions.

Conclusions:

• A ligand-controlled mechanism for reversible substrate coordination has been demonstrated.
• Tunable ligand binding modes offer a strategy for controlling reactivity in organometallic complexes.
• This work provides insights into ligand design for dynamic coordination chemistry.