Ruthenium is used in the following sectors of homogeneous catalysis:
Carbonylations are conversions with carbon monoxide (CO) under formation of aldehydes, ketones, or carboxylic acids by inserting a C=O group.
The most important process on a large scale is the carbonylation of methanol to acetic acid ("Monsanto Process"). Besides, there are other product routes, e.g. the manufacture of acetic anhydride from methyl acetate. All these processes are based on rhodium in the presence of iodine-containing compounds. Recent methods are also based on iridium with co-catalysts ("Cativa Process").
Coupling reactions serve to link organic molecules or parts within a molecule mostly by forming carbon-carbon bonds ("C-C Coupling"). Such reactions are popular in the industries of pharmaceuticals, agrochemicals, fine chemicals, and specialties.
Coupling reactions of dienes can also be performed with rhodium or even with ruthenium. A technical rhodium-based process is the reaction of ethene with butadiene forming hexa-1,4-diene. The coupling of dienes is possible, too.
Also some oxidations can be homogeneously carried out on a large scale with precious metals. The best-known case is the "Hoechst-Wacker" process: The synthesis of acetaldehyde from ethene and oxygen in the presence of the catalyst system palladium/copper (in aqueous, chloride-containing solutions).
Ruthenium(VIII) oxide, which is best generated in situ from Ru precursors and suitable oxidizing agents (e.g. hydrogen peroxide), can cleave alkenes into carboxylic acids or oxidize secondary alcohols to ketones. In the presence of oxidizing agents, the oxidation of alcohols is also feasible by using palladium.
Hydrogenations are reactions of unsaturated molecules with hydrogen (H2). Precious metal compounds of rhodium, ruthenium, or iridium rank with the most effective homogeneous hydrogenation catalysts because of their outstanding selectivities.
Catalysts for hydrogenations are often equivalent to those for hydroformylations, where the reactants H2 and CO are applied.
Besides, C=O's, C=N's, and alkynes can be hydrogenated. Ruthenium in particular has an affinity for C=O bonds. Hydrogenations of imine groups could effectively be managed with iridium. On the basis of homogeneous ruthenium catalysts, ring hydrogenations are feasible, too.
Well-known are especially the "Wilkinson's Catalyst" and dichlorotris(triphenylphosphane)ruthenium(II) mainly for the hydrogenation of terminal C=C's.
Hydrogenations lead to chiral centres in prochiral molecules. Like right and left hands, "chiral" molecules of the same constitution (empirical formula, structure) can coincide only with their mirror-images. Chirality is extraordinarily important to modern agents in the field of life science, where almost just one chiral variant is active to a specific purpose. Such "asymmetric hydrogenations" are feasible in a very effective way by using precious metal precursors along with chiral ligands. Heraeus offers a broad range of such precursors relevant to industry, mostly organometallics.
Moreover, Heraeus manufactures new catalysts on a commercial scale and in strict confidence according to customers’ specifications.