Alkylidene complexes of ruthenium containing N-heterocyclic carbene ligands; use as highly active, selective catalysts for olefin metathesis

A complex of ruthenium of the structural formula I,

• where X1 and X2 are identical or different and are each an anionic ligand, R1 and R2 are identical or different and are each hydrogen or a hydrocarbon group, where the hydrocarbon groups are identical or different and are selected independently from among straight-chain, branched, cyclic or noncyclic radicals from the group consisting of alkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals having up to 50 carbon atoms, alkynyl radicals having up to 50 carbon atoms, aryl radicals having up to 30 carbon atoms and silyl radicals, or R1 and R2 form a ring,
• where one or more of the hydrogen atoms in the hydrocarbon or silyl groups or both the hydrocarbon and silyl group can be replaced independently by identical or different alkyl, aryl, alkenyl, alkynyl, metallocenyl, halogen, nitro, nitroso, hydroxy, alkoxy, aryloxy, amino, amido, carboxyl, carbonyl, thio or sulfonyl groups or mixtures thereof the ligand L1 is an N-heterocyclic carbene and the ligand L2 is N-heterocyelic carbene of the formulae III-V or an amine, imine, phosphine, phosphite, stibine, arsine, carbonyl compound, carboxyl compound, nitrile, alcohol, ether, thiol or thioether, and wherein formulae (III)-(V) are
• where R1, R2, R3 and R4 in the formulae III, IV and V are identical or different and are each hydrogen or a hydrocarbon group, where the hydrocarbon groups comprise identical or different, cyclic, noncyclic, straight-chain or/and branched radicals selected from the group consisting of alkyl radicals having from 1 to 50 carbon atoms, alkenyl radicals having up to 50 carbon atoms, alkynyl radicals havin up to 50 carbon atoms and aryl radicals having up to 30 carbon atoms, in which at least one hydrogen may be replaced by functional groups, and where one or both of R3 and R4 may be identical or different and are halogen, nitro, nitroso, alkoxy, aryloxy, amido, carboxyl, carbonyl, thio or sulfonyl groups.