The invention provides catalytically active compounds for alkyne metathesis comprising a ligand, on his part containing a guanidinate core which is forming a complex with a transition metal atom. Formally, the guanidinate core is a mononegative ligand that binds with the metal atom. One or both of the nitrogen atoms of the guanidiate core, which are not participating in the metal complexing bond, can be substituted with substituents being selected from hydrogen, alkyl, alkenyl, aromatic residues, optionally including hetero atoms, e.g. halogen atoms, preferably fluorine.