Solid-phase cyclopalladation in S,C,S'-pincer systems: rising alternative for synthesis in solution

Area of Science:

• Organometallic Chemistry
• Solid-State Synthesis
• Coordination Chemistry

Background:

• Traditional synthesis of organometallic pincer complexes often involves solution-based methods.
• Developing simpler, more efficient synthetic routes is crucial for advancing organometallic chemistry.
• S,C,S'-pincer ligands with thione sulfur donors present unique synthetic challenges.

Purpose of the Study:

• To investigate the feasibility of solid-phase cyclopalladation for synthesizing organometallic pincer complexes.
• To explore a new, solvent-free approach for forming palladium-carbon bonds.
• To evaluate the efficiency and yield of the solid-phase method compared to solution-based synthesis.

Main Methods:

• Manual grinding of S,C,S'-pincer ligands with PdCl2(NCPh)2.
• Heating the solid mixtures in open test tubes without solvent.
• Monitoring the solid-phase transformation using IR spectroscopy and Scanning Electron Microscopy (SEM) analysis.

Main Results:

• Efficient solid-phase cyclopalladation was achieved for various S,C,S'-pincer ligands, yielding pincer-type products in high yields.
• The reaction proceeded even at room temperature for the most active bis(thiocarbamoyl) ligand.
• Using preformed non-metallated complexes enhanced yields for challenging bis(thiophosphoryl) derivatives compared to solution methods.

Conclusions:

• Solid-phase cyclopalladation offers a simple, solvent-free, and efficient method for synthesizing organometallic pincer complexes.
• This methodology provides a powerful alternative to conventional solution-based synthesis.
• The study demonstrates the potential of solid-state reactions in organometallic chemistry.