The present invention relates to a new class of trinuclear Zirconium complexes comprising of general formula (I)in which the substituents at the cyclohexyl rings exhibit an all-cis configuration, and in which R1, R2, R3, R4, R5, m, n, y and X are as defined in the claims, to methods of preparing said compounds, and to the use of said compounds as X-ray contrast agents.