Pd (II) complexes bearing "SNS" pincer‐type thioether ligands: Application as catalysts in the synthesis of vitamin K3.

The novel four SNS pincer‐type thioether containing Pd (II) complexes were synthesized and characterized by using FT‐IR, UV‐Vis, mass, elemental analysis techniques. The complexes were used as catalysts in the synthesis of vitamin K3 (2‐methyl‐1,4‐naphthoquinone) from 2‐methyl naphthalene. Hydrogen peroxide was used as green oxidant in acetic acid and sulfuric acid medium. L2‐Pd (II) and L3‐Pd (II) complexes showed the best catalytic activity with 62.63% and 61.05% selectivities in the conversions of 82.61% and 87.84%, respectively. Moreover, in silico studies on Pd (II) complexes have shown that L2‐Pd (II) and L3‐Pd (II) complexes have low band gaps between LUMO and HOMO energy levels and their electrostatic energy values are higher than other complex structures. This reveals that they have better chemical activity than other complexes and also supports the experimental studies carried out in this research. The conversions and the selectivities of these complexes are one of the best compared to the literature. Peroxyacetic acid with sulfuric acid is a very important oxidant in the oxidation of 2‐methyl naphthalene to 2‐methyl‐1,4‐naphthoquinone. [ABSTRACT FROM AUTHOR]