Ammine Ligand Exchange in Tetraamminepalladium(II) in Aqueous Solution.

Brønnum, Birthe; Johansen, H. Saaby; Skibsted, Leif H.; Lund, Henning; Tekenbergs-Hjelte, Lija; Ohlson, Kristina

doi:10.3891/acta.chem.scand.43-0975

Cited by 19 publications

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“…As has been observed previously for metals deposited in porous Si, the morphology of the metal deposit can be controlled by the chemical nature of the metal precursor. , In the present case, we investigated the morphology of Pd deposited from two different Pd(II) compounds, the chloride salt PdCl 2 and the tetraammine coordination complex [Pd(NH 3 ) 4 ] 2+ . In aqueous solution, PdCl 2 exists as a mixture of aquo-, hydroxy-, and chloride- complexes of Pd(II), whereas [Pd(NH 3 ) 4 ] 2+ is a square planar d 8 coordination complex with high thermodynamic stability and relatively slow ligand exchange kinetics . Treatment of aqueous dispersions of the empty pSiNPs with either of these two Pd complexes in aqueous solution resulted in formation of Pd nanoparticles within and on the porous matrix (Figure B,C for the PdCl 2 and [Pd(NH 3 ) 4 ] 2+ complexes, respectively, and Figure S3 in Supporting Information).…”

Section: Results and Discussionmentioning

confidence: 99%

“…In aqueous solution, PdCl 2 exists as a mixture of aquo-, hydroxy-, and chloride-complexes of Pd(II), 36 whereas [Pd(NH 3 ) 4 ] 2+ is a square planar d 8 coordination complex with high thermodynamic stability and relatively slow ligand exchange kinetics. 63 Treatment of aqueous dispersions of the empty pSiNPs with either of these two Pd complexes in aqueous solution resulted in formation of Pd nanoparticles within and on the porous matrix (Figure 1B,C for the PdCl 2 and [Pd(NH 3 ) 4 ] 2+ complexes, respectively, and Figure S3 in Supporting Information). In general, the [Pd(NH 3 ) 4 ] 2+ complex yielded smaller Pd nanoparticles (6−18 nm) which had more uniform sizes and which were distributed more homogeneously in the porous Si matrix.…”

Section: Resultsmentioning

confidence: 99%

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Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Kim

Warther

et al. 2017

ACS Nano

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Porous silicon nanoparticles containing both Pd and iron oxide nanoparticles are prepared and studied as magnetically recoverable catalysts for organic reductions. The Pd nanoparticles are generated in situ by electroless deposition of Pd(NH), where the porous Si skeleton acts as both a template and as a reducing agent and the released ammonia ligands raise the local pH to exert control over the size of the Pd nanoparticles. The nanocomposites are characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, nitrogen adsorption, X-ray diffraction, superconducting quantum interference device magnetization, and dynamic light scattering. The nanocomposite consists of a porous Si nanoparticle (150 nm mean diameter) containing ∼20 nm pores, uniformly decorated with a high loading of surfactant-free Pd nanoparticles (12 nm mean diameter) and superparamagnetic γ-FeO nanoparticles (∼7 nm mean diameter). The reduction of 4-nitrophenol to 4-aminophenol by sodium borohydride is catalyzed by the nanocomposite, which is stable through the course of the reaction. Catalytic reduction of the organic dyes methylene blue and rhodamine B is also demonstrated. The conversion efficiency and catalytic activity are found to be superior to a commercial Pd/C catalyst compared under comparable reaction conditions. The composite catalyst can be recovered from the reaction mixture by applying an external magnetic field due to the existence of the superparamagnetic iron oxide nanoparticles in the construct. The recovered particles retain their catalytic activity.

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Section: Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Kim

Warther

et al. 2017

ACS Nano

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“…A number of exchange processes at square-planar palladium(II) and platinum(II) complexes with oxygen-, nitrogen-, sulfur-, and carbon-bonded ligands have been studied. − Except for cases where there is extensive transfer of electron density from strongly σ-bonding carbon-donor ligands to the metal center, , these processes, like square-planar substitution reactions in general, seem to take place via associative mechanisms.…”

Section: Introductionmentioning

confidence: 99%

Theoretical Modeling of Water Exchange on [Pd(H₂O)₄]²⁺, [Pt(H₂O)₄]²⁺, and trans-[PtCl₂(H₂O)₂]

1996

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Density functional theory is applied to modeling the exchange in aqueous solution of H(2)O on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)]. Optimized structures for the starting molecules are reported together with trigonal bipyramidal (tbp) systems relevant to an associative mechanism. While a rigorous tbp geometry cannot by symmetry be the actual transition state, it appears that the energy differences between model tbp structures and the actual transition states are small. Ground state geometries calculated via the local density approximation (LDA) for [Pd(H(2)O)(4)](2+) and relativistically corrected LDA for the Pt complexes are in good agreement with available experimental data. Nonlocal gradient corrections to the LDA lead to relatively inferior structures. The computed structures for analogous Pd and Pt species are very similar. The equatorial M-OH(2) bonds of all the LDA-optimized tbp structures are predicted to expand by 0.25-0.30 Å, while the axial bonds change little relative to the planar precursors. This bond stretching in the transition state counteracts the decrease in partial molar volume caused by coordination of the entering water molecule and can explain qualitatively the small and closely similar volumes of activation observed. The relatively higher activation enthalpies of the Pt species can be traced to the relativistic correction of the total energies while the absolute DeltaH() values for exchange on [Pd(H(2)O)(4)](2+) and [Pt(H(2)O)(4)](2+) are reproduced using relativistically corrected LDA energies and a simple Born model for hydration. The validity of the latter is confirmed via some simple atomistic molecular mechanics estimates of the relative hydration enthalpies of [Pd(H(2)O)(4)](2+) and [Pd(H(2)O)(5)](2+). The computed DeltaH() values are 57, 92, and 103 kJ/mol compared to experimental values of 50(2), 90(2), and 100(2) kJ/mol for [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)], respectively. The calculated activation enthalpy for a hypothetical dissociative water exchange at [Pd(H(2)O)(4)](2+) is 199 kJ/mol. A qualitative analysis of the modeling procedure, the relative hydration enthalpies, and the zero-point and finite temperature corrections yields an estimated uncertainty for the theoretical activation enthalpies of about 15 kJ/mol.

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“…The rate constant that was obtained for the reaction of substitution of a water molecule for an ammonia molecule in the Pd ( NH 3 complex at 25°ë in the presence of 1 M (Na, NH 4 ) ClO 4 was equal to 3.0 × 10 -4 s -1 [28].…”

Section: Electroreduction Of Pd(ii) Complexes Without Preceding Chemimentioning

confidence: 99%

Kinetics and mechanism of electroreduction of Pd(II) complexes

Kravtsov

2004

Russ J Electrochem

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The kinetics and mechanism of processes of reduction of Pd(II) complexes with a number of inorganic (NH 3 , Cl -, etc.) and organic (ethylenediamine, glycine, α -alanine, etc.) ligands on a dropping-mercury electrode and a Pd electrode in solutions with various concentrations of ligands, hydrogen ions, and supporting electrolytes are reviewed. The nature of electrochemical and chemical steps of processes of reduction of various complexes of Pd(II) is discussed.

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Ammine Ligand Exchange in Tetraamminepalladium(II) in Aqueous Solution.

Cited by 19 publications

References 0 publications

Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Theoretical Modeling of Water Exchange on [Pd(H₂O)₄]²⁺, [Pt(H₂O)₄]²⁺, and trans-[PtCl₂(H₂O)₂]

Kinetics and mechanism of electroreduction of Pd(II) complexes

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Ammine Ligand Exchange in Tetraamminepalladium(II) in Aqueous Solution.

Cited by 19 publications

References 0 publications

Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Size-Controlled Pd Nanoparticle Catalysts Prepared by Galvanic Displacement into a Porous Si-Iron Oxide Nanoparticle Host

Theoretical Modeling of Water Exchange on [Pd(H2O)4]2+, [Pt(H2O)4]2+, and trans-[PtCl2(H2O)2]

Kinetics and mechanism of electroreduction of Pd(II) complexes

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Theoretical Modeling of Water Exchange on [Pd(H₂O)₄]²⁺, [Pt(H₂O)₄]²⁺, and trans-[PtCl₂(H₂O)₂]