Novel non-symmetric POCOP-Ni(II) pincer complexes derived from 2,4-dihydroxybenzaldehyde

Area of Science:

• Organometallic Chemistry
• Coordination Chemistry
• Catalysis

Background:

• Pincer ligands, such as POCOP-type, offer rigidity, modularity, and electronic control for stabilizing metal centers.
• Non-symmetric POCOP frameworks are underexplored for discovering novel reactivity patterns.
• Nickel(II) complexes are valuable in catalysis and materials science.

Purpose of the Study:

• To synthesize novel non-symmetric Ni(II)-POCOP pincer complexes.
• To investigate the influence of base and acidity on the formation and structure of these complexes.
• To explore new reactivity pathways enabled by asymmetric ligand design.

Main Methods:

• Synthesis of non-symmetric Ni(II)-POCOP pincer complexes under varying conditions (basic vs. base-free).
• Characterization using spectroscopic methods (NMR, IR, etc.).
• Structural determination via single-crystal X-ray diffraction.

Main Results:

• Selective formation of aldehyde-type Ni(II)-POCOP complexes under basic conditions.
• Formation of imine-type addition complexes under base-free conditions, with partial hydrolysis to aldehyde-type complexes.
• Identification of medium acidity as a key factor influencing complex stability and reactivity.

Conclusions:

• The presence or absence of base during metalation decisively controls the formation of non-symmetric Ni(II)-POCOP complexes.
• Acidic conditions promote ligand activation and the formation of addition complexes.
• Optimized conditions allow for selective synthesis, yielding insights into phosphinite-based pincer systems.