oa Editorial [Mini-Hot Topic: Metal Complexes and their Use as Catalysts in Selective Syntheses (Guest Editor: Gyorgy Keglevich)]

Environmentally-friendly (green) chemistry is in focus these days. One of the twelve principles of green chemistry recommends the application of catalysts making possible selective synthesis under milder conditions. The six articles of this minireview issue describe novel complexes and/or the use of such compounds in synthesis. The first paper covers the synthesis and application of -SCS- pincer complexes incorporating thiocarbamoyl or thiophosphoryl coordinating groups and in most cases palladium as the metal. The remark of the late Professor Pascal Le Floch (died at the age of 51 this Spring): “It makes no doubt that the S-C-S-M pincer complexes will lead many researchers to study this highly interesting family of organometallic complexes” underlines the importance of this field. The second article includes novel carbene complexes of (X=P)2C…M type stabilized by two electron-withdrawing iminophosphoryl or thiophosphinoyl groups. It has been shown that the electronic character of the carbon center can be tuned by the substituents and the metal center. This contribution comes from the immediate colleagues of P. Le Floch. The novel platinum complexes including heterocyclic P-ligands, such as phospholene-, phospholane-, dihydro-, and tetrahydrophosphinine-, as well as dibenzooxaphosphorine ligands are summarized, together with catalytic applications. P. Le Floch was highly interested in such complexes. He was seriously ill, but he remained interested in seeing our comprehensive studies. The next two contributions are on the novel catalytic applications of routine catalysts. The first paper describes chemoselective homogeneous catalytic amino-carbonylations of iodoalkenes and iodoarenes made possible by an in situ generated palladium-triphenylphosphine catalyst. The second article on catalytic application shows that reactive ketenes can be obtained from diazoalkanes by the use of cobalt-carbonyl catalysts. Intermediate cobalt complexes were identified in the process and a mechanism was proved. The last paper comprises phase transfer catalyzed enantioselective Michael- and Darzens reactions that could be accomplished in the presence of sugar-based optically active crown ethers or lariat ethers. In these cases, diastereomeric transition states based on cationic complexes are involved. The articles of this minireview series are collectively dedicated to our talented friend, Professor Dr Pascal Le Floch.