Pd(II) and Ni(II) complexes featuring a "phosphasalen" ligand: synthesis and DFT study

Area of Science:

• Coordination Chemistry
• Organophosphorus Chemistry
• Materials Science

Background:

• Salen ligands are widely used in coordination chemistry due to their versatile coordination properties.
• Developing novel ligands with unique electronic and structural features is crucial for advancing catalysis and materials science.
• Introducing phosphorus into ligand frameworks can significantly alter metal-ligand interactions and complex properties.

Purpose of the Study:

• To synthesize and characterize a novel phosphorus analog of salen ligands, termed phosphasalen.
• To explore the coordination chemistry of phosphasalen with transition metals like Palladium (Pd(II)) and Nickel (Ni(II)).
• To investigate the structural, electronic, and magnetic properties of the resulting metal complexes.

Main Methods:

• Two-step synthesis of the phosphasalen ligand from o-diphenylphosphinophenol.
• Coordination of the ligand to Pd(II) and Ni(II) metal centers.
• Characterization using multinuclear NMR, elemental analysis, X-ray diffraction, cyclic voltammetry, and magnetic moment measurements.
• Density Functional Theory (DFT) calculations for the nickel complex.

Main Results:

• Successful synthesis of the novel tetradentate phosphasalen ligand.
• Formation of neutral Pd(II) and Ni(II) complexes with nearly square-planar geometry.
• Coordination involves all iminophosphorane and phenolate moieties.
• Electronic properties were investigated, showing distinct behavior compared to traditional salens, especially for the nickel complex.

Conclusions:

• Phosphasalen represents a new class of tetradentate ligands with tunable electronic properties.
• The synthesized metal complexes exhibit unique structural and electronic characteristics.
• Further investigation into phosphasalen complexes could lead to new applications in catalysis and materials science.