Proton magnetic resonance study of ligand exchange on tetrakis(hexamethylphosphoramide)dioxouranium(VI)

1978 ◽  
Vol 17 (7) ◽  
pp. 1855-1857 ◽  
Author(s):  
Geoffrey J. Honan ◽  
Stephen F. Lincoln ◽  
Evan H. Williams
Keyword(s):  
Magnetic Resonance ◽  
Ligand Exchange ◽  
Proton Magnetic Resonance ◽  
Magnetic Resonance Study ◽  
Proton Magnetic Resonance Study

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 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 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.

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