
TY  - JOUR
A1  - Pisaniello, DL 
A1  - Lincoln, SF 
A1  - Williams, EH 
A1  - Jones, AJ 
T1  - Nuclear magnetic resonance study of ligand exchange on hexakis(1,1,3,3-tetramethylurea)yttrium(III)
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1981
VL  - 34
IS  - 3
SP  - 495
EP  - 500
KW  - 
UR  - https://doi.org/10.1071/CH9810495 
N2  - The first reported direct study of monodentate ligand exchange on yttrium(III) shows the rate of 1,1,3,3-tetramethylurea exchange on [Y {O=C(NMe2)2}6]3+ to be independent of free ligand concentration consistent with the operation of either a dissociative mechanism or an interchange mechanism where the encounter complex stability constant is &#8805; 300. Typical data from this 270-MHz 1H n.m.r. study, where  rate of ligand exchange = kex 6[Y {O=C(NMe2)2}63+]  are as follows: kex(250 K) = 25±1 s-1, &#916;H&#8225; = 27.1 ± 0.5 kJ mol-1 and &#916;S&#8225; = -108 ± 2 J K-1 mol-1 for a CD3CN solution in which [Y{O=C(NMe2)2}63+] and free [O=C(NMe2)2] are 0.0039 and 0.028 mol dm-3 respectively. The preparations of [Y(ligand)6] (ClO4)3 where the ligand is O=C(NMe2)2, O=C(Me)(NHMe), O=C(Me)(NMe2), or O=C(Me)(NEt2) are also reported. Solutions of the latter three species and their respective ligands exhibit spectra consistent with ligand exchange being in the fast exchange limit of the n.m.r. time scale down to the lowest accessible temperatures. 
ER  -

