The coupling of carbon dioxide with ethene to produce acrylic acid sodium salt in one pot by using Ni(II) and Pd(II)-phosphine complexes as precatalysts

The use of CO₂ as a feedstock for chemical synthesis is considered as a viable alternative option to some traditional processes. One of the most interesting challenge for the industry is represented by the CO₂ coupling with olefins to produce acrylate. Only recently, with the choice of suitable ligands and the use of a sacrificial base, a selective catalytic reaction was established by using Ni(0)-based complexes. The one-pot reaction, which leads to the highest TON (107 mol/mol Ni, in 20 h) reported so far, was successfully developed starting from Ni(0)-based precursors in the presence of disphosphine ligands, a large excess of base and of finely powdered zinc. In the present paper, we carried out the catalytic synthesis of sodium acrylate from CO₂ and ethene, in one-pot, by using Ni(II)-chloride and Pd(II)-chloride phosphine-complexes as precatalyst. The reaction occurs under basic conditions and without adding any external reductants. The Ni(II) complexes lead to higher TON than the respective Pd(II) precursors and the best results are obtained by using diphosphines having high bite angles. Such catalysis is favored by aprotic and polar solvents in which a TON of 290 mol/mol Ni is reached by using the [NiCl₂(dppp)] precursor in DMSO. Furthermore the TON could be increased by increasing the temperature, the base concentration and by using diphosphine ligands having high bite angle.