Metal complexes for use in metathesis

metal with a coordination number five, a salt, a solvate or an enantiomer thereof, comprising a carbene ligand a multidentate ligand and one or more other ligands, wherein at least one of said other ligands is a complex one ligand steric restriction having a pKa of at least 15, said ligand steric restriction a derivative, wherein one or more hydrogen atoms are substituted with a group providing steric hindrance restriction, a phonic not superbase of profosfatrano or an N-heterocyclic carbene selected from the group consisting of imidazole-2-ylidene, dihydroimidazol-2-on ylidene, oxazole-2-ylidene, the triazol-5-ylidene, the thiazole 2-ylidene, bis (imidazolin-2-ylidene), bis (2-ylidene imidazolidinedione-), the pirrolilideno, the pirazolilideno, the dihidropirrolilideno, the pirrolilidinilideno and fused benzene derivatives thereof.