A phosphorus-31 magnetic resonance study of ligand exchange on tetrakis(hexamethylphosphoramide)zinc(II) ion

1980 ◽  
Vol 33 (12) ◽  
pp. 2621 ◽  
Author(s):  
MN Tkaczuk ◽  
SF Lincoln
Keyword(s):  
Magnetic Resonance ◽  
Kinetic Parameters ◽  
Time Scale ◽  
Ligand Exchange ◽  
Exchange Process ◽  
Magnetic Resonance Study ◽  
Fast Exchange

The rate of the associative ligand exchange process on tetrakis (hexamethylphosphoramide)zinc(II) ion in CD2Cl2 solution, determined by 31P n.m.r. spectroscopy, is given by: ������������������� rate = 4k2[O=P(Nme2)3][Zn(O=P(NMe2)3)42+] The characteristic kinetic parameters are: k2(240 K) 304�17 dm3 mol-1 s-1, ΔH2‡ 22.7�0.9 kJ mol-1, and ΔS2‡ -101�4 J K-1 mol-1. ��� The preparations of [Zn(O=P(NMe2)3)4](ClO4)2, [Zn(O=P(OMe)3)5] (ClO4)2 and [Zn {O=P(Me)-(OMe)2}5](ClO4)2 are reported. The rate of ligand exchange upon the last two species was found to be in the fast-exchange limit of the n.m.r. time scale.

A Proton Magnetic Resonance Study of Ligand Exchange on Tetrakis(tetramethylthiourea)zinc(II) Ion

1979 ◽  
Vol 32 (9) ◽  
pp. 1915 ◽  
Author(s):  
MN Tkaczuk ◽  
SF Lincoln
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Time Scale ◽  
Ligand Exchange ◽  
Proton Magnetic Resonance ◽  
Exchange Mechanism ◽  
Magnetic Resonance Study ◽  
Fast Exchange ◽  
Proton Magnetic Resonance Study

The rate of ligand exchange on the tetrakis(tetramethylthiourea) zinc(II) ion, determined by 1H N.M.R. methods, in CD2Cl2 solution is found to be independent of free-tetramethylthiourea concentration. This is consistent with a dissociative ligand-exchange mechanism being operative. Typically for a solution in which [Zn{S=C(NMe2)2}42+] and [S=C(NMe2)2] were 0�00101 and 0�00376 respectively, kex(200 K) = 16�0�0.6 s-1, ΔH‡ = 64�9�O.8 kJ mol-1 and ΔS‡ = 106�4 J K-1 mol-1 where the observed ligand-exchange rate is given by rate = 4kex[Zn {S=C(NMe2)2}42+] The preparations of [Zn(O=CHNMe2)6](ClO4)2, [Zn{O=CMe(NMe2)}6](Cl04)2, and [Zn{O=C- (NMe2)2}4](ClO4)2 are also reported. The rate of ligand exchange upon these three species in CD2Cl2 solution was found to be in the fast-exchange limit of the N.M.R. time scale.

A phosphorus-31 magnetic resonance study of ligand exchange on Hexakis[methyl methyl(phenyl)phosphinate]yttrium(III) ion and the solution chemistry of related yttrium(III) species

1981 ◽  
Vol 34 (6) ◽  
pp. 1195
Author(s):  
DL Pisaniello ◽  
SF Lincoln
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Time Scale ◽  
Ligand Exchange ◽  
Solution Chemistry ◽  
Magnetic Resonance Study ◽  
Coordination Numbers ◽  
Exchange Study ◽  
Fast Exchange ◽  
Methyl Phenyl

A 31P n.m.r, study shows that the species [YLn3+ where n = 4,5,6 for L = OP(NMe2), or OPPh3 n = 5,6 for L = OPMe(0Me)Ph are the major yttrium(III) species formed with these ligands in CD2CI2 solution. A detailed ligand exchange study of the latter species shows the rate law to be: exchange rate = 6(kl+k2[OPMe(OMe)Ph])[Y(OPMe(OMe)Ph)63+] where k1(215 K) = 312�13 s-1, ΔH1‡ = 3l·4 � 1.4 kJmol-1, ΔS1‡ = -48·4�6.6 J K-1 mol-1, k2(215 K) = 455 � 31 dm3 mol-1 s-1, ΔH2‡ = 35·2�2.8 kJmol-1 and ΔS2‡ = -27·6 � 12·7 JK-1 mol-1, where the k1 and k2 terms are assigned to D and A mechanisms respectively. The rate of OP(OMe)3 and OPMe(OMe)2 exchange on yttrium(III) is found to be in the fast exchange limit of the n.m.r. time scale and thus the coordination numbers of the yttrium(III) species formed with these ligands are not directly determined in solution. Qualitatively it appears that the coordination number and the lability of the yttrium(III) species increases as the size of the ligand decreases. The isolation of the crystalline species [Y(OP(NMe2)3)5ClO4](ClO4)2, [Y(OPPh3)4](ClO4)3, [Y(OPMe(OMe)Ph)6] (ClO4)3, [Y(OP(OMe)3)6](ClO4)3 and [Y(OPMe(OMe)2)6](ClO4)3 is reported.

A preparative and phosphorus-31 nuclear magnetic resonance study of the coordination of three phosphate based ligands to dioxouranium(VI)

1982 ◽  
Vol 35 (7) ◽  
pp. 1489
Author(s):  
AE Bakas ◽  
AM Hounslow ◽  
SF Lincoln ◽  
NJ Maeji
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Ligand Exchange ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
The Third ◽  
Nuclear Magnetic

The three species [UO2{OP(OMe)(NMe2)2}4](ClO4)2, [UO2{OP(OMe)2(NMe)}5] (C1O4)2 and [UO2{OPMe2Ph)]5] (ClO4)2 have been isolated and their CD2Cl2 solutions studied by means of 31P n.m.r. An equilibrium between [UO2L52+ and [UO2L4]2+ exists in solutions of the first two species. In solutions of the third species [UO2L5]2+ predominates and ligand exchange proceeds through a dissociative D mechanism for which kex (285 K), characterizing a single ligand, is 1830 � 250 s-1, ΔH‡ 82.15 � 1.8 kJ mol-1 and ΔS‡ 106 � 16 JK-1 mol-1.

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