Komplexone XXIX. Ein grosser Chelateffekt besonderer Art

Abstract Complexing agents of the type: (HOOCCH 2 )( 2 =N(CH 2 )) n  N = (CH 2 COOH) 2 with n‐values from 2–8 have been investigated. The stability constants of the 1:1 complexes of Ca 2+ , Cd 2+ and Hg 2+ have been determined for nearly the whole series of these complexons and a few values have been obtained also for the complexes of Mg 2+ , Sr 2+ , Ba 2+ and Go 2+ . There is generally a strong decrease in complex stability when n is increased from 2 t o 4, where an almost constant value is reached which does not alter anymore to an appreciable extent hy a further increase of the chain length 11. The mercury complexes behave exceptionally. Replacement of one or two CH 2 ‐groups in the chain connecting the two nitrogens by O, S, and N(CH 2 ) increases the complex stability to a great extent if new 5‐membered chelate rings can be formed by coordination of this heteroatom.