13C NMR characterization of actinyl(VI) carbonate complexes in aqueous solution

Clark, David L.; Hobart, David E.; Palmer, Phillip D.; Sullivan, James C.; Stout, Barbara E.

doi:10.1016/0925-8388(93)90319-i

Cited by 12 publications

(20 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This ligand‐exchange reaction is important both technologically and geochemically because oxalate is the conjugate base of one of the simplest acids found in soils, in which it is a product of fungal metabolism, and oxalate is also used in the PUREX process for purifying uranium and plutonium . This research complements the existing study on homoleptic water‐exchange reactions for transition metals and studies of the carbonato complexes of other transuranic elements …”

Section: Introductionmentioning

confidence: 67%

See 1 more Smart Citation

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO₂(C₂O₄)₂]³⁻ Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

et al. 2018

View full text Add to dashboard Cite

The kinetics of ligand exchange between the free oxalate ion, C2O42−, and the bis‐oxalato NpV complex, [NpO2(C2O4)2]3−, in aqueous solution are reported by using 13C and 17O NMR spectroscopy methods. Rates of exchange were measured in the pH regime of 6.5–9.0, at which speciation is shown to be suitably simple. Because the neptunium(V) complex is paramagnetic, the rates of ligand exchange were estimated by following the width of the 13C and 17O signals assigned to the free oxalate ion in solution and by applying the Swift–Connick method for measuring rates of exchange. A set of experiments were conducted in which pH and total oxalate concentration were varied, and the linear dependence of the rate on these parameters was demonstrated. Variable‐temperature NMR spectroscopy was also performed to measure activation parameters of complexation. At pH<8.0, ΔH≠=16.9 ±4.9 kJ mol−1 and ΔS≠=−116.3 ±17.1 kJ mol−1 K−1, whereas at pH>8.0 there is almost no dependence on temperature, which is interpreted to indicate that hydrolysis is coupled to ligand exchange under these conditions.

show abstract

Section: Introductionmentioning

confidence: 67%

“…The Swift–Connick method was used for rate determination with both 13 C‐ and 17 O‐labeled samples . The full‐width at half‐maximum (FWHM) of an NMR signal, if measured for a signal in a system undergoing two‐site exchange, is generally defined by Equation :

true π (FWHM) = 1 / T_{2}^{*} + k_{ex, normali}

…”

Section: Resultsmentioning

confidence: 99%

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO₂(C₂O₄)₂]³⁻ Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

et al. 2018

View full text Add to dashboard Cite

show abstract

“…Three samples from the pH 9.72 stock were also used in studies of serial dilution. These experiments employed a standard Bruker NMR probe, but were diluted from the stock 26 The samples were loaded into quartz NMR tubes (see the Supporting Information) and floated on fluorocarbon oil (poly-(chloro)trifluoroethylene) in order to maximize the number of spins in the NMR coil. A Teflon plug was inserted, and air was bled from the samples.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Pressure Dependence of Carbonate Exchange with [NpO₂(CO₃)₃]^4– in Aqueous Solutions

2016

View full text Add to dashboard Cite

The rates of ligand exchange into the geochemically important [NpO(CO)] aqueous complex are measured as a function of pressure in order to complement existing data on the isostructural [UO(CO)] complex. Experiments are conducted at pH conditions where the rate of exchange is independent of the proton concentration. Unexpectedly, the experiments show a distinct difference in the pressure dependencies of rates of exchange for the uranyl and neptunyl complexes.

show abstract

“…In this paper we extend the work by Stout et al 1 With these solutions, they used the line-broadening method described by Swift and Connick 25 in which NMR peak width and chemical shift differences are assigned to the free carbonate ion with and without the paramagnetic metal, in this case Np(VI). This method is most commonly used when the signal for the reactive species is unobservable due to paramagnetic broadening and fast exchange, such as when 17 O exists in the hydration shell of paramagnetic monomer ions (e.g., [Fe-(OH 2 ) 6 ] 3+ , 19,26,27 ) and exchanges with bulk water. The rate of exchange from the solvation shell is inferred from the effect on the bulk solution 17 O peak.…”

Section: ■ Introductionmentioning

confidence: 99%

Kinetic Studies of the [NpO₂(CO₃)₃]^4– Ion at Alkaline Conditions Using ¹³C NMR

et al. 2014

View full text Add to dashboard Cite

Carbonate ligand-exchange rates on the [NpO2(CO3)3]4– ion were determined using a saturation-transfer 13C nuclear magnetic resonance (NMR) pulse sequence in the pH range of 8.1 ≤ pH ≤ 10.5. Over the pH range 9.3 ≤ pH ≤ 10.5, which compares most directly with previous work of Stout et al.,1 we find an average rate, activation energy, enthalpy, and entropy of kex298 = 40.6(±4.3) s–1, Ea =45.1(±3.8) kJ mol–1, ΔH‡ = 42.6(±3.8) kJ mol–1, and ΔS‡ = −72(±13) J mol–1 K–1, respectively. These activation parameters are similar to the Stout et al. results at pH 9.4. However, their room-temperature rate at pH 9.4, kex298 = 143(±1.0) s–1, is 3 times faster than what we experimentally determined at pH 9.3: kex298 = 45.4(±5.3) s–1. Our rates for [NpO2(CO3)3]4– are also faster by a factor of 3 relative to the isoelectronic [UO2(CO3)3]4– as reported by Brucher et al.2 of kex298 = 13(±3) s–1. Consistent with results for the [UO2(CO3)3]4– ion, we find evidence for a proton-enhanced pathway for carbonate exchange for the [NpO2(CO3)3]4– ion at pH < 9.0.

show abstract

13C NMR characterization of actinyl(VI) carbonate complexes in aqueous solution

Cited by 12 publications

References 15 publications

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO₂(C₂O₄)₂]³⁻ Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO₂(C₂O₄)₂]³⁻ Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

Pressure Dependence of Carbonate Exchange with [NpO₂(CO₃)₃]^4– in Aqueous Solutions

Kinetic Studies of the [NpO₂(CO₃)₃]^4– Ion at Alkaline Conditions Using ¹³C NMR

Contact Info

Product

Resources

About

13C NMR characterization of actinyl(VI) carbonate complexes in aqueous solution

Cited by 12 publications

References 15 publications

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO2(C2O4)2]3− Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO2(C2O4)2]3− Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

Pressure Dependence of Carbonate Exchange with [NpO2(CO3)3]4– in Aqueous Solutions

Kinetic Studies of the [NpO2(CO3)3]4– Ion at Alkaline Conditions Using 13C NMR

Contact Info

Product

Resources

About

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO₂(C₂O₄)₂]³⁻ Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

Rates of Ligand Exchange around the Bis‐Oxalato Complex [NpO₂(C₂O₄)₂]³⁻ Measured by Using Multinuclear NMR Spectroscopy under Neutral to Semi‐Alkaline Conditions

Pressure Dependence of Carbonate Exchange with [NpO₂(CO₃)₃]^4– in Aqueous Solutions

Kinetic Studies of the [NpO₂(CO₃)₃]^4– Ion at Alkaline Conditions Using ¹³C NMR