In situ generated diphenylphosphine-chelated imidazo[1,5-a]pyridin-3-ylidene nickel(0) catalysts for highly efficient acrylate synthesis from ethylene and CO2

Abstract

Diphenylphosphine-chelated imidazo[1,5-a]pyridin-3-ylidene (PPh₂-ImPy) nickel(0) catalysts were synthesized in-situ from imidazolium salts and various commercially available nickel(0) complexes using a base. These catalysts exhibited a highly planar and rigid structure, as confirmed by X-ray crystallographic analysis. Remarkably, the in-situ generated PPh₂-ImPy-Ni(0) catalyst demonstrated a turnover number (TON) of 570 while maintaining a high yield of 82 %, overcoming the typical trade-off between TON and yield often observed in acrylate synthesis reactions, where the use of excess base to achieve high TON typically results in lower product yields. Moreover, the ligand precursors (PPh₂-ImPy∙HCl salts) were stable under open-air conditions, making them easy to handle. The in-situ generation protocol using the ligand precursors and commercially available metal sources, eliminates the need for synthesizing sensitive Ni(0) catalysts. Furthermore, the sodium acrylate product was efficiently isolated from the reaction mixture through a straightforward extraction process.

Keywords

• N-heterocyclic carbene
• Nickel
• Acrylate
• Ethylene
• Carbon dioxide