Homobimetallic and heterobimetallic alkylidene complexes of ruthenium containing N-heterocyclic carbene ligands

A complex of ruthenium having the structural formula I,

• where X is an anionic ligand,
• Z is a monodentate, bidentate or tridentate ligand which contains a metal and is nonionically bound to the ruthenium center,
• R1 and R2 are identical or different and are hydrogen or a hydrocarbon group, where the hydrocarbon groups are identical or different and are each a straight-chain, branched or cyclic radical selected from the group consisting of alkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals having from 2 to 50 carbon atoms, alkynyl radicals having from 2 to 50 carbon atoms, aryl radicals having from 6 to 30 carbon atoms and silyl radicals, where one or more of the hydrogen atoms in the hydrocarbon or silyl groups may be replaced by identical or independently different alkyl, aryl, alkenyl, alkynyl, metallocenyl, halogen, nitro, nitroso, hydroxy, alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or sulfonyl groups, or R1 and R2 are identical or different and form a ring,
• L is an N-heterocyclic carbene ligand having one of the formulas II-V:
• where R1, R2, R3 and R4 in the formulas II, III, IV and V are identical or different and are each hydrogen or a hydrocarbon group, where the hydrocarbon groups are identical or different and are each independently cyclic, straight-chain or branched radicals selected from the group consisting of alkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals having from 2 to 50 carbon atoms, alkynyl radicals having from 2 to 50 carbon atoms, and aryl radicals having from 6 to 30 atoms, in which at least one hydrogen may be replaced by a functional group or where R3 and R4 can be replaced by functional groups selected from the group consisting of halogen, nitro, nitroso, alkoxy, aryloxy, amido, carboxyl, carbonyl, thio and sulfonyl.