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 proton magnetic resonance study of ligand exchange on tetrakis(N,N-diethylacetamide)beryllium(II)

1982 ◽  
Vol 35 (8) ◽  
pp. 1555 ◽  
Author(s):  
MN Tkaczuk ◽  
SF Lincoln
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Ligand Exchange ◽  
Proton Magnetic Resonance ◽  
Exchange Mechanism ◽  
Magnetic Resonance Study ◽  
Rate Law ◽  
Proton Magnetic Resonance Study ◽  
Exchange Data

A lH n.m.r. study shows that ligand exchange on tetrakis(N,N-diethylacetamide)beryllium(II) in both CD3NO2 and CD3CN solution is charaterized by the rate law: Exchange rate = 4(k1 + k2[OCMe(NEt2)]free)[Be{OCMe(NEt2)}42+] In CD3NO2 solution k1 (340K) is 2.3 � 0.1 s-1, ΔH‡.76.4 � 2.2 kJ mol-1, ΔS‡ -14.6 � 6.4 JK-1 mol-1, k2 (340K) 19.9 � 0.3 dm3 mol-1s-1, ΔH‡ 68.5 � 0.8kJ mol-1, ΔS‡ -19.6 � 2.4 JK-1 mol-1, and somewhat different magnitudes are observed in CD3CN solution. The k1 term is assigned to a dissociative (D) ligand exchange mechanism, and the k2 term is assigned to either an associative (A) or an interchange (I) mechanism. These data are discussed in conjunction with ligand exchange data for other beryllium(II) systems.

A Proton Magnetic Resonance Study of Ligand Exchange on the Pentakis (N-formylpyrrolidine)dioxouranium (VI) Ion

1979 ◽  
Vol 32 (8) ◽  
pp. 1851 ◽  
Author(s):  
GJ Honan ◽  
SF Lincoln ◽  
EH Williams
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Ligand Exchange ◽  
Proton Magnetic Resonance ◽  
Magnetic Resonance Study ◽  
Rate Law ◽  
Predominant Species ◽  
Proton Magnetic Resonance Study

Pentakis(N-formylpyrrolidine)dioxouranium(VI) perchlorate, [UO2(fpr)5] (ClO4)2, has been isolated from solution. In the presence of excess free fpr the greatly predominant species in CD2Cl2 solutions is [UO2(fpr)5]2+, as shown by 1H N.M.R. spectroscopy, and fpr exchange is characterized by a two term rate law: exchange rate = 5(k1+ k2[fpr])[UO2(fpr)52+] It is found that k1(220 K) = 42�6�0�5 s-1, ΔH‡ = 30�7�1�4 kJ mol-1 and ΔS‡ = -71�6�6�3 J K-1 mol-1, and k2(220 K) = 369�20 dm3 mol-1 s-1, ΔH‡ = 30�5�1�0 kJ mol-1 and ΔS‡ = -54�9�5�0 J K-1 mol-1. The mechanistic implications of these data are discussed.

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 proton magnetic resonance study of ligand exchange on Pentakis(N,N-diethylacetamide)dioxouranium(VI)

1981 ◽  
Vol 34 (12) ◽  
pp. 2543 ◽  
Author(s):  
AM Hounslow ◽  
SF Lincoln ◽  
PA Marshall ◽  
EH Williams
Keyword(s):  
Exchange Rate ◽  
Magnetic Resonance ◽  
Ligand Exchange ◽  
Proton Magnetic Resonance ◽  
Free Ligand ◽  
Ligand Concentration ◽  
Similar Data ◽  
Magnetic Resonance Study ◽  
Rate Law ◽  
Proton Magnetic Resonance Study

Pentakis(N,N-diethylacetamide)dioxouranium(VI) bisperchlorate, [UO2(AcNEt2)5] has been isolated. Proton N.M.R. spectroscopy shows that, in the presence of excess free ligand, [UO2- AcNEt2)5]2+ is the greatly predominant dioxouranium(V1) species in both CD2Cl2 and CD3CN solutions. The rate of ligand exchange is independent of free ligand concentration as shown by the rate law exchange rate = 5k1[UO2(AcNEt2)52+]where in CD2Cl2 solution k1(265 K) = 54.8 � 8.3 s-1, ΔH.‡ = 68.3 � 1.2 kJ mol-1 and ΔS‡ = 47.1 � 4.6 JK-1 mol-1. Somewhat different values for these parameters are obtained in CD3CN solution. These data are compared with similar data for other dioxouranium(VI) systems, and mechanistic comparisons are made.

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.

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