Ruthenium Complexes Containing Bidentate Schiff Base Ligands as Precursors of Homogeneous and Immobilized Catalysts

The paper presents recent work conducted in our group on the synthesis of a novel class of homogeneous and immobilized Rucomplexes containing Schiff bases as O,N-bidentate ligands benefiting from a versatile, quite general and thoroughly exemplified twostep procedure. The new Ru-complexes with improved stability incorporate a variety of Schiff bases, associated with traditional inorganic and organic ligands such as chloride, phosphanes, arenes, cyclodienes, NHC etc., and different carbenes (alkylidene, vinylidene, allenylidene and indenylidene). By a proper choice of the Schiff base, useful physical and chemical properties of the derived Rucomplexes could be induced resulting in tunable catalytic activity for metathesis and related processes. A pertinent example is the latency of selected Schiff base Ru catalysts which by becoming active only under specific conditions (heat or acid activation) are ideal for industrial applications, e.g. reaction injection molding processes. The synthetic approaches that are critically discussed in this artcile have led to a diversity of Ru-complexes of which several members have risen to the rank of commercial catalysts.