A will of iron: An active well‐defined iron complex (see structure; gray C, white H, yellow B, green F, brown Fe, pink P) catalyzes the title reaction (see scheme). The iron‐catalyzed reduction of readily available bicarbonates to formates has also been demonstrated for the first time. This reaction could be an important step in the use of CO2 for hydrogen storage.

A novel selective palladium catalyst system based on bidentate 2,2'-heteroarylarylphosphines and p-TsOH has been developed for hydroformylation reactions (see scheme). By applying optimal conditions good to excellent regioselectivity is obtained for the hydroformylation of aliphatic and aromatic olefins. It is shown that a low acid concentration is crucial for obtaining high degrees of the linear isomer.The palladium-catalyzed hydroformylation of 1-octene has been studied in the presence of different phosphines and acid cocatalysts. The best results are achieved in the presence of in situ-generated palladium complexes with bidentate phosphines. It is demonstrated that the acid concentration is a crucial factor for obtaining high linear selectivity. A novel optimized catalyst based on an arylheteroarylphosphine has been applied for hydroformylation of different aliphatic and aromatic olefins. Good activity and excellent selectivity towards the linear aldehydes is achieved.

Breaking with conventional wisdom: Hydroformylation catalysts are generally based on rhodium; earlier, cobalt was used. Iridium, which is less expensive than rhodium, was considered too unreactive. However, iridium/phosphine complexes have now been shown to form active catalysts for the hydroformylation of olefins under mild conditions (see scheme; R1, R2=H, alkyl, aryl; R3=H, alkyl). Competing hydrogenation side reactions can be suppressed.

Dedicated to Professor Š tefan Toma on the occasion of his 75th birthday Carbonylation reactions of olefins are among the most important industrially applied homogeneous catalytic transformations. [1] Nowadays, especially, lower aliphatic olefins are converted on a million-ton scale by hydroformylation into aldehydes, [2,3] and further on into aliphatic alcohols, which are used as major components of solvents, plasticizers, speciality chemicals, etc. In general, the linear products are preferred for such large-scale applications, whereas branched aldehydes and alcohols are of interest for the fine chemical and lifescience industries. [4] By far the most utilized catalysts for hydroformylation reactions both in industry and academia are based on rhodium; cobalt catalysts are also highly utilized, in particular for the functionalization of higher aliphatic olefins. Other metal catalysts have not received much attention in the past. [5] During our ongoing research in the field of hydroformylation, [6] we became interested in the activities of alternative hydroformylation catalysts. Notably, the accepted order of catalyst activity (Rh > Co > Ir > Ru > Os > Pt > Pd > Fe > Ni) is solely based on fixed reaction conditions and the use of unmodified metal carbonyl complexes. [2a] More recently, we have demonstrated that metals such as palladium [6c] and iridium [6a] can be successfully applied in the hydroformylation of olefins, as they show improved activity under modified reaction conditions. In the case of iridium, for example, the addition of the required amount of hydrogen at the appro-priate reaction temperature proved crucial for the prevention of the undesired competitive hydrogenation of the substrate.Among all the available noble metals used in catalysts for carbonylation reactions, ruthenium is the least expensive metal, and is also becoming increasingly important in homogeneous catalysis. [7] For hydroformylations, the relative activity of ruthenium carbonyl complexes is assumed to be lower by a factor of 10 5 compared with similar rhodium complexes. Although the first ruthenium-catalyzed hydroformylation, which employed [Ru(CO) 3 (PPh 3 ) 3 ] as a catalyst, was reported as early as 1965 by Evans, Osborn, Jardine, and Wilkinson, [8] only a few selective Ru-based catalysts have been described in the decades since then. [9] In general, only a narrow substrate scope could be realized with these systems and the reactions were very often carried out under harsh conditions with high catalyst loadings. Typically, mixtures of aldehydes and alcohols were obtained, with higher temperatures preferred for obtaining the alcohols. In addition, hydrogenation and/or isomerization of the olefin occurred as side reactions. Hence, none of these systems was of practical relevance. Notably, very recently Takahashi, Yamashita, Tanaka, and Nozaki demonstrated a highly regioselective catalytic system based on a specific [RuCp*] complex and bidentate ligands for the transformation of olefins to aldehydes. [10] However, the activity...

Kein altes Eisen: Ein neuer, aktiver, wohldefinierter Eisenkomplex (siehe Struktur; grau C, weiß H, gelb B, grün F, braun Fe, rosa P) katalysiert die Titelreaktion (siehe Schema). Damit gelang erstmals die eisenkatalysierte Reduktion leicht zugänglicher Bicarbonate zu Formiaten. Die Reaktion kann ein wichtiger Schritt hin zur Nutzung von CO2 als Wasserstoffspeicher sein.