Rebuttal to: Polemic against conclusions drawn in “Palladium/iodide catalyzed oxidative carbonylation of aniline to diphenylurea: Effect of ppm amounts of iron salts” (J. Catal. 369 (2019) 257–266)

Abstract

Abstract In the article mentioned in the title, the authors have tried to demonstrate that, in the previously reported Pd/iodide-catalyzed oxidative carbonylations of amines to give ureas, the role of iodide ligands was essentially to “etch” the stainless steel autoclaves where the process was performed, releasing in solution small amounts of iron salts. These latter iron species were, in their opinion, the real co-catalysts of the reaction, through the presumed formation of more active Pd/Fe bimetallic species. However, no solid experimental evidence corroborating this hypothesis has been given in the article, while all previous experimental evidences and literature data tend to exclude the involvement of iron co-catalysis in the Pd/iodide-promoted reactions.