Nuclear magnetic resonance study of ligand exchange on Hexakis(1,1,3,3-tetramethylurea)lutetium(III)

1982 ◽  
Vol 35 (12) ◽  
pp. 2393 ◽  
Author(s):  
SF Lincoln ◽  
AM Hounslow ◽  
AJ Jones
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Exchange Rate ◽  
Ligand Exchange ◽  
Nuclear Magnetic Resonance Study ◽  
Complex Stability ◽  
Magnetic Resonance Study ◽  
Dissociative Mechanism ◽  
Complex Stability Constant ◽  
Encounter Complex ◽  
Trivalent Lanthanide

A 270-MHz lH n.m.r. study shows the rate of 1,1,3,3-tetramethylurea exchange on [Lu{OC(NMe2)2}6]2+ in CD3CN solution to be independent of [OC(NMe2)2]free consistent with the operation of either a dissociative mechanism or an interchange mechanism characterized by an encounter complex stability constant ≥ 400. For this study ligand exchange rate = 6kex[Lu{OC(NMe2)2}63+] with kex(298.2 K) = 41.9 � 2.7 s-l, ΔH‡ = 41.7 � -0.6 kJmol-1 and ΔS‡ = -74 � JK-1 mol-l. These data are compared with those for the analogous scandium(III) and yttrium(III) systems and also those for some eight-coordinate trivalent lanthanide systems. The preparations of [LuL6] (ClO4)3, where L = OC(NMe2)2, OCMe(NMe2) and OCMe(Net2), are reported.

Nuclear magnetic resonance study of ligand exchange on hexakis(1,1,3,3-tetramethylurea)yttrium(III)

1981 ◽  
Vol 34 (3) ◽  
pp. 495 ◽  
Author(s):  
DL Pisaniello ◽  
SF Lincoln ◽  
EH Williams ◽  
AJ Jones
Keyword(s):  
Ligand Exchange ◽  
Free Ligand ◽  
Nuclear Magnetic Resonance Study ◽  
Monodentate Ligand ◽  
Dissociative Mechanism ◽  
Complex Stability Constant ◽  
Typical Data ◽  
Encounter Complex ◽  
Fast Exchange ◽  
Scale Down

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 ≥ 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, ΔH‡ = 27.1 � 0.5 kJ mol-1 and ΔS‡ = -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.

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.

A 19F nuclear magnetic resonance study of the exchange of the fluoro ligands of the tetrafluoroberyllium(II) ion

1977 ◽  
Vol 30 (2) ◽  
pp. 271 ◽  
Author(s):  
SF Lincoln ◽  
AC Sandercock ◽  
DR Stranks
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Exchange Rate ◽  
Magnetic Resonance ◽  
Exchange Process ◽  
Nuclear Magnetic Resonance Study ◽  
Magnetic Resonance Study ◽  
Rate Law ◽  
The Exchange Rate ◽  
Nuclear Magnetic

A 19F N.M.R. study is reported of the exchange of the fluoro ligands of [BeF4]2-. The exchange rate law is: ����������� rate = kobs4[BeF42-] = k'4[BeF42-]+ k''4[BeF42-][BeF3H2O-] where k'(298 K) = 69�3 s-1, ΔH‡ = 30�3 kJ mol-1, ΔS‡ = -110�10 J mol-1 K-1 and k''(298 K) = (1.6�0.5)×103 dm3 mol-1 s-1, ΔH‡ = 26�3 kJ mol-1, ΔS‡ = - 96�9 J mol-1 K-1. The k' exchange process appears to be predominantly dissociative in nature, and the k'' exchange process apparently proceeds through a fluoro bridged species [Be2F7]2-.

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