Special issue on advances in catalysis in aqueous media

The general perception in the early seventies was that catalytic reactions in aqueous media employing water-soluble organometallic complexes of transition metals to produce commodity chemicals could not take place despite (1) the discovery in 1827 of the first water-soluble transition metal complex, Zeise’s salt, K[PtCl3(η-C2H4)]·H2O [1] and (2) the industrial application in 1959 of water-soluble cobalt sulfonated phthalocyanine catalytic complexes in the UOP Extractive Merox™ thiols oxidation process for upgrading oil refining products [2]. Notwithstanding these early contributions, in 1974 two groups independently showed that water-soluble organometallic complexes of transition metals can catalyze different reactions in this green aqueous reaction medium. The group of F. Joó and M.T. Beck carried out the aqueous-phase hydrogenation of pyruvic acid to lactic acid catalyzed by water-soluble Ru/TPPMS complexes [TPPMS, sodium salt of monosulfonated triphenylphosphine, PPh2(C6H4-m-SO3Na)], while E.G. Kuntz at Rhône-Poulenc achieved the proof of principle showing that the hydroformylation of propene to butyraldehydes catalyzed by water-soluble Rh/TPPTS complexes [TPPTS, sodium salt of trisulfonated triphenylphosphine, P(C6H4-m-SO3Na)3] can be done on a laboratory scale in aqueous/organic biphasic systems. The industrial scale aqueous/organic two-phase propene hydroformylation process using a water-soluble Rh/TPPTS catalyst was developed after successful pilot plant scale tests in 1984 by Cornils et al. at Ruhrchemie which is well known as the Ruhrchemie/Rhône-Poulenc (RCH/RP) process [3], [4]. This first major success was followed by additional industrial biphasic processes that, today, have led to an exponential increase of new applications of several water-soluble transition metal complexes modified by numerous ligands, such as sulfonated and carboxylated phosphines, phosphines containing hydroxy and ether functionalities, phosphines with amino, ammonium, phosphonium, phosphonate and phosphate moieties, sulfonated amines, phthalocyanines, porphyrins, phospholes and thioethers or sulfone-based phosphines, and nitrogen-containing ligands. Also included are tenside ligands that catalyze diverse reactions, such as hydroformylations of lower, midrange, higher and functionalized olefins, hydrocarboxylations, carbonylations, alternating copolymerizations of olefins with CO to polyketones, hydrogenations, hydrogenolyses, oxidations, epoxidations, dehydrations, isomerizations, epimerizations, ring-openings, alkylations, and telomerizations, etc. to produce commodity chemicals in aqueous/organic two-phase systems [3]. [...]