Societd suisse dc chimie, BLle -Socicth svizzcra di chimica, Basilea Nachdruck verboten -Tous droits rdserves --Printcd by Birkhiiuser AG., Hascl, Switzerland Erscheint 9mal jiilirlich -Paraft 9 fois par an XSSN 0018-019X 1 . Etude par RMN. de polyaminocarboxylates de terres rares, 111. Rydroxy4thyliminodiacbtates de prasbodymel) 2, par FraaGois Chastellain ct Andre E. Merbach Institut de chimie mindralc ct analytique de 1' Universitk dc Lausanne (17. X. 74) .Summauy. lH. . NMK. has bccn used to study the chemistry of tho hydroxyethyliminodiacetate complexes of prascodymiurn in aqueous solution. The ligand cxchangev by spontaneous dissociation of thc mctal-bis-hydroxyethyliminodiacctatc (1 : 2 complex) and of the motal-bishydroxycthyliminacliacetate hydroxocomplcx, by acid catalysecl dissociation of the 1 : 2 complcx, and by a himolecular process involving thc frcc ligantf ant1 the 1 : 2 complex or the tcrnary hydroxocomplex. T h e ligand exchange rate constants are given and the mechanisms discussetl.

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