Rhodium‐Catalyzed Acrylate Synthesis from Carbon Dioxide and Ethylene by using a Guanidine‐Based Pincer Ligand: Perturbing Occupied d‐Orbitals by pπ‐dπ Repulsion Makes a Difference

Rhodium‐catalyzed acrylate synthesis from CO2 and ethylene was accomplished by using a guanidine‐based NCN pincer ligand. The repulsion between pπ‐electron of guanidine sidearms and occupied dπ orbital of rhodium center raised the level of d‐electrons close to those of formerly known d8‐ruthenium catalyst, thereby promoting the metallalactone formation from carbon dioxide and ethylene. This work fills the absence of group‐9 metal based catalyst for the acrylate synthesis and provides a designing approach for pincer‐ligated d8‐metal catalysts to utilize pπ‐dπ interaction for promoting desirable redox processes. Rhodium complexes bearing a guanidine based NCN pincer ligand were designed and successfully applied to catalytic acrylate synthesis from carbon dioxide and ethylene. The repulsion between pπ‐electron of guanidine and filled dπ orbital of Rh center increases the electron density on Rh, allowing the first structural characterization of rhodalactone formation.