Paint formulations, based either on organic solvents or on water, often contain alkyd resins that depend on catalysts for their oxidative curing. Cobalt carboxylates are the most widely used to date, but the use of these compounds is under pressure because classification as carcinogens under the REACh system is probable, and as a consequence there is great interest in the development of alternative driers to cobalt-based ones. A variety of manganese and iron carboxylates have been studied as paint drying catalysts in the last[a] Catexel BV, www.eurjic.org MICROREVIEW coating dries. Metal ions and complexes can facilitate these oxidation reactions and polymerisations. During the autooxidation of alkyd paints the unsaturated fatty acids react with molecular oxygen from the air to form -initiallyalkyl hydroperoxides (Scheme 1). [3,4] Subsequent decomposition of these alkyl hydroperoxides yields alkoxy and per-Johannes W. de Boer received his PhD in chemistry (2008) from the University of Groningen, the Netherlands, under the guidance of Prof. Ben L. Feringa and Dr. Ronald Hage and was awarded the Backer Prize by the Royal Dutch Chemical Society for his thesis on manganese-catalysed oxidation reactions. In 2007 he joined Rahu Catalytics, currently Catexel, where he works as Research Principal. His current research interests include the development of new oxidation catalysts and processes for a wide variety of (industrial) applications, focussing on manganese-and iron-catalysed activation of hydrogen peroxide and oxygen. Philana V. Wesenhagen gained her master's degree in chemistry at the University of Groningen in 2006 and joined the team of Rahu Catalytics from 2007 to 2009. After this she switched her fields of interest from chemistry to biotechnology and obtained a second master's degree, in cellular and molecular biotechnology at Wageningen University, in 2011. Currently she is doing her PhD at the Forschungszentrum in Jülich at the Institut für Bio-und Geowissenschaften. Erica C. M. Wenker gained a master's degree in chemistry (2010) at Leiden University, the Netherlands. During her master's she carried out mechanistic research on paint-drying catalysts at Rahu Catalytics. She is currently doing a PhD in coordination chemistry and catalysis under the guidance of Prof. Dr. Elisabeth Bouwman at Leiden University. Karin Maaijen obtained a bachelor's degree in chemistry in 2007 and a master's degree in chemistry and physics (2009) from Utrecht University (the Netherlands) with a major in inorganic chemistry and catalysis. In 2010 she joined Rahu Catalytics, currently Catexel, where she works as a Research Scientist on iron and manganese catalysts for various industrial applications. Franjo Gol gained a master's degree in chemistry and a Dr. rer. nat. in inorganic and organophosphorus chemistry at Wuppertal University. He has worked in the chemical industry for 26 years, initially on the development of water-borne binders for coatings for Herberts and then on binders, metal carboxylates and paint additives for Abshag...
A systematic library of 24 nickel(II) complexes with bidentate diphosphane ligands was synthesized, and the solid-state structures of five of them were determined with X-ray crystallography. The compounds C1-C3 are common P2Ni(II)X2-type complexes, while C4 contains a unique [P2Ni(II)(NH3)(OAc)](+) square-planar structure with a P2NO donor set and C5 constitutes a rare [(P2Ni(II))2(μ-OH)2](2+) dinuclear compound. The catalytic activity of all complexes was tested in the hydrogenation and/or isomerization of 1-octene in a CH2Cl2/CH3OH reaction medium. Catalyst precursors bearing ligands with o-alkoxy aryl rings selectively hydrogentate 1-octene to n-octane, while catalytic systems comprising ligands without the o-alkoxy functionality selectively isomerize the substrate to a mixture of internal alkenes, mostly cis- and trans-2-octene. The conversion is enhanced by equipping the ligand aryl rings with electron-donating alkoxy groups, by increasing the steric bulk of the backbone and/or the aryl rings, by employing relatively noncoordinating anions, and by adding a base as the cocatalyst. Using the compound [Ni(L3X)I2] as the catalyst precursor and upon application of standard hydrogenation conditions, full conversion of the substrate was achieved in 1 h to isomerization products only (TON = 1940). When a catalytic amount of the base is added, a similar result is obtained even in the absence of H2. A maximum TON of 4500 in 1 h with 96% selectivity for n-octane was achieved by employing [Ni(oMeO-L3X)(NH3)(OAc)]PF6 as the catalyst precursor.
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