Ruthenium catalysts for the Kharasch reaction

Recent advances in the development of ruthenium catalysts for the atom transfer radical addition of polyhalogenated compounds to olefins ('Kharasch reaction') are described. Three classes of homogeneous catalysts are discussed: halfsandwich complexes with eta(6)-arene, eta(5)-cyclopentadienyl or eta(5)-carborane ligands, ruthenium complexes with alkylidene- or vinylidene ligands and polynuclear complexes. Furthermore, first attempts to use immobilized ruthenium complexes as heterogeneous catalysts for the Kharasch reaction are summarized.