NHC and hydroximate ancillary ligands: a successful combination for olefin metathesis in non-anhydrous media?

The development of more sustainable chemical processes has an inherent relationship with the use of efficient catalysts. With this purpose, this work aims to develop more robust ruthenium(II) catalysts for olefin metathesis reactions in non-anhydrous media. The main compound, [Ru(IMes)(p-cymene)(PhHA)] (Ru4), combines an N-heterocyclic carbene (IMes) and k²-O,O'-hydroxamate chelating ligand derived from benzohydroxamic acid, designed to protect the catalytic species from non-anhydrous reactions. For the development of Ru4, [Ru(CO₃)(IMes)(p-cymene)] (Ru2) and [RuCl₂(IMes)(p-cymene)] (Ru3) were synthesized and characterized by NMR, FTIR, UV-Vis, and, for Ru2, X-ray diffraction, as it is a novel structure. Preliminary evidence by ¹H NMR suggests the formation of Ru4; however, its purification remains challenging due to the lability of the p-cymene ligand. The compounds will be evaluated as pre-catalysts, after activation with ethyl diazoacetate, in the cross-metathesis between estragole and 2-ethylhexyl acrylate under anhydrous and non-anhydrous conditions.