Cover Picture: Unusual Influence of the Structures of Transition Metal Complexes on Catalytic C–S and C–Se Bond Formation Under Homogeneous and Heterogeneous Conditions (Eur. J. Org. Chem. 21/2007)

Abstract

AbstractThe cover picture shows that tuning the size of the catalyst particles provides a powerful synthetic tool for controlling not only the selectivity and yield, but also the direction of the chemical transformation. Soluble mononuclear and dinuclear phosphine complexes of palladium are excellent catalysts for stereoselctive E–E (E = S, Se) bond addition to alkynes. However, these complexes are poor catalysts for E–H bond addition to alkynes. Increasing the size of the catalyst particles changes the reactivity: polymeric species of nickel and palladium become efficient catalysts of E–H bond addition under heterogeneous conditions, while they are totally inactive in E?E bond addition. The unique self‐organized catalytic system shown in the background (magnified by scanning electron microscopy) combines the best features on the polynuclear metal complex and supported catalyst. Details are presented in the Microreview by I. P. Beletskaya and V. P. Ananikov on p. 3431 ff.