Yttrium , ligand exchange

Ligand exchange reactions of triphenylphosphine oxide complexes of yttrium compounds were studied. ... 

Rate laws for the exchange of Y + with yttrium(m) complexes of the aminocarboxylate ligands edta, cydta, and dtpa have terms in hydrogen ion concentration and in yttrium(in) concentration. The terms in which hydrogen ion concentration, or its square, appears relate to dissociation of mono- and di-protonated forms of the complex. Terms in yttrium(ra) concentration relate to bimolecular attack by the incoming Y +. Yttrium(m) exchange with its hedta complex has a rate law in which the yttrium(m) ion concentration does not appear, so the mechanism here must be purely dissociative. ... 

PisanieUo D, Lincoln S, WUliams E, Jones A. Nuclear magnetic resonance study of ligand exchange on hexakis(l,l,3,3-tetramethylurea)yttrium(III). Aust J Chem. 1981 34 495-500. 

The measurement of stability constants of complexes of yttrium, lanthanide, and actinide ions with oxalate, citrate, edta, and 1,2-diaminocyclohexanetetra-acetate ligands has revealed that there is a slight increase in the stability of complexes of the /-electron elements, relative to the others. A series of citric acid (H cit) complexes of the lanthanides have been investigated by ion-exchange methods and the species [Ln(H2cit)]", [Ln(H2cit)2] , [Ln-(Hcit)], and [Ln(Hcit))2] were detected. Simple and mixed complexes of dl- and jeso-tartaric acid have been obtained with La " and Nd ions, and the stability constants of lactate, pyruvate, and x-alaninate complexes of Eu and Am " in water have been determined. 

It is known from Eigen s technique of temperature jumps that a water molecule remains coordinated to rare earth aqua ions for roughly 10 s for R = La to Sm and for roughly 10 s for yttrium and R = Dy to Lu. There is a marked break from europium to terbium. Unfortunately, these results do not tell us everything we want to know. The problem is that the measured rate may refer to one (or a few) particularly mobile ligands. Thus, copper(II) aqua ions exchange water more... 

The rare earth ions form a variety of types of complexes in both aqueous and non-aqueous solution and these have been studied extensively. The initial impetus for studies of the solution chemistry was centered on the development of more efficient ligands for use in the ion exchange separation of yttrium and the lanthanides. Likewise, a large portion of the work devoted to the study of complexes in non-aqueous solutions was ultimately directed toward improvements in the solvent extraction separation. 

Lanthanide compounds such as yttrium and lanthanum alkoxides have been reported to yield high-molecular-mass polyesters under mild conditions. The yttrium alkoxide-initiated polymerization of CL proceeded rapidly at room temperature [27-29], while the use of bulky groups reduced the transesterification reaction such that polymers with a narrow molecular mass were obtained (Scheme 11.3). For example, the bulky phenoxide ligands of the yttrium or lanthanide catalyst were exchanged for the smaller alcohol (2-propanol), followed by coordination and insertion of the monomer (CL) [27]. 

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