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Reactions of a series of unsymmetrically substituted N-heterocyclic carbene ligands with Ru3(CO)12afforded a variety of mononuclear (1, 2), trinuclear (3, 4, 5, and 5′), and tetranuclear (6, 7) ruthenium complexes via intramolecular ruthenium-mediated sp2and sp3C–H bond activations. Complexes 6and 7include an octahedral cluster skeleton consisting of four ruthenium atoms and two metalated carbon atoms. The formation of this type of ruthenium clusters is proposed to involve the initial C–C double-bond migration and subsequent sp2C–H bond activations. All new complexes were fully characterized, and the molecular structures of 1, 2, 5, 6, and 7were determined by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

Thermal treatment of indenyl-functionalized imidazolium salts and N-heterocyclic carbenes with Ru3(CO)12gave different products. The normal mononuclear metal complexes (2a, 2b) were obtained viadirect reaction of indenyl-functionalized imidazolium salts (1a, 1b) with Ru3(CO)12. Unexpected intramolecular C–H activated products (3a, 3b, 4a, 4b) were obtained viathermal treatment of corresponding indenyl-functionalized N-heterocyclic carbenes. All complexes were determined by 1H NMR, 13C NMR, IR spectra and elemental analysis. The molecular structures of 2b, 3a, 3band 4bwere determined by X-ray diffraction. [ABSTRACT FROM AUTHOR]