
TY  - JOUR
A1  - Lincoln, SF 
A1  - Pisaniello, DL 
A1  - Spotswood, TM 
A1  - Tkaczuk, MN 
T1  - A phosphorus-31 nuclear magnetic resonance study of triphenylphosphine oxide exchange on magnesium(II) and zinc(II)
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1981
VL  - 34
IS  - 2
SP  - 283
EP  - 289
KW  - 
UR  - https://doi.org/10.1071/CH9810283 
N2  - 31P n.m.r, studies show that the rate of triphenylphosphine oxide exchange on [Zn(O=PPh3)4]2+ in CD2Cl2 solution is independent of [O=PPh3]free. A typical data set is: kex(200 K) = 611 &#177; 37 s-1, &#916;H&#8225; = 32.0 &#177; 0.7 kJ mol-1 and &#916;S&#8225; = -28.3 &#177; 3.4 J K-1 mol-1 for a solution in which [Zn(O=PPh3)42+] and [O=PPh3]free are 0.163 and 0.639 mol dm-3 respectively, where kex = exchange rate/(4[Zn(O=PPh3)42+])= (kBT/h)exp(-&#916;H&#8225;/RT)exp(&#916;S&#8225;/R) Similarly the rate of ligand exchange on [Mg(O=PPh3)5]2+ is shown to be independent of [O=PPh3]free and a typical data set is kex'(220 K) = 38 &#177; 4 s-1, &#916;H&#8225; = 73.7 &#177; 1.8 kJ mol-1 and &#916;S&#8225; = 123 &#177; 8 J K-1 mol-1 for a solution in which [Mg(O=PPh3)52+] and [O=PPh3]free are 0.0813 and 0.276 mol dm-3 respectively. The ligand exchange process on both species is considered to proceed through a D mechanism. The apparent equilibrium constant K = [Mg(O=PPh3)52+]/ ([Mg(O=PPh3)42+][O=PPh3] &#8805; 150 dm3 mol-1 but in contrast [Zn(O=PPh3)2+ appears to be the only stable zinc(II) species in solution. It is concluded that these data probably reflect the hard acid character of magnesium(II) and the intermediate acid characteristics of zinc(II). 
ER  -

