FDTA [1,1′‐ F errocendiyl d i(methyleneamino) t etra a cetate] – An Organometallic Relative of EDTA The tetrasodium salt of 1,1′‐ f errocendiyl d i(methyleneamino)‐ t etra a cetate (FDTA‐Na 4 ) – a relative of EDTA (ethylene d i‐amino t etra a cetate) – was prepared from the reaction of N,N′ ‐1,1′‐ferrocendiylbismethylenebis(pyridinium) chloride tosylate with tetramethyl iminodiacetate and subsequent saponification with NaOH/CH 3 OH. Potentiometric titrations were performed to determine the stability constants of the complexes of FDTA (= L) with the alkaline earth metal ions Mg 2+ , Ca 2+ , Sr 2+ , and Ba 2+ (β: brutto stability constants): MgL (log β = 4.63), MgL 2 (log β = 8.10), CaL (log β = 4.97), CaLH (log β = 14.20); SrL (log β = 3.91), SrLH (log β = 13.43), and BaL (log β = 3.06). The stability constants are discussed with a view to cooperative effects of the two iminodiacetate groups in FDTA. The nonexistence of M 2 L and ML 2 (M = Ca, Sr) species is considered indicative of a cooperative effect of the donor groups. The X‐ray crystal structure of FDTA‐Na 4 was determined.