Looking for further possibilities to increase the stability of the stereoretentive complexes while keeping or improving their activity and selectivity, we decided to modify the substituent on the chelating oxygen atom while retaining the structure of Hoveyda-Grubbs catalyst with so far the best dithiocatecholate ligand. To achieve this goal, we prepared and examined-in terms of activity, selectivity, and stability-a series of stereoretentive Ru-catalysts with modified ethereal substituent in benzylidene ligand (depicted in Figure ).