Pd(II), Ni(II), Cu(II) and Co(II) complexes bearing ?SNS? pincer type Ligand: Application as catalysts for chemical CO2 conversion to obtain cyclic carbonates

A new tridentate pincer type ligand 2,6-bis[[(4-methylphenyl)thio]carbonyl]pyridine (L),possessing nitrogen donor and two sulfur (SNS) donor set was metallized with Pd(OAc)2, Ni(OAc)2, Cu(OAc)2 and Co(OAc)2, respectively, and the new bidentate (L-Pd) and tridentate SNS pincer type complexes (L-Ni, L-Cu, L-Co) were obtained.The synthesized compounds were characterized by various methods such as X-ray (for ligand), NMR, Mass, UV-Vis, FT-IR, elemental analysis, molar conductivity.The spectral data showed that the molecular structure of Pd(II) complex exhibitsa four-coordinated square planar structure around the metal center, while other complexes exhibit a distorted triangular bipyramidal geometry with five coordination. There are no conductivity characteristics in the complexes showing non-electrolyte nature in solution. Furthermore, the compounds were utilized as catalysts in the synthesis of cyclic carbonates from epoxide and CO2. The tridentate SNS pincer type complex (L-Co) showed the highest catalytic activity (at 100 degrees C and 1.6 MPa of CO2 pressure) for the carboxylation of epichlorohydrin with 90.3% conversion after just 1 h.