| 1. |
- Drougge, Lise, et al.
(författare)
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Mechanisms for Acceleration of Halide Anation Reactions of Platinum(IV) Complexes. REOA versus Ligand Assistance and Platinu(II) Catalysis without Central Ion Exchange
- 1986
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Ingår i: Inorganica Chimica Acta. - 0020-1693. ; 121:2, s. 175-183
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Tidskriftsartikel (refereegranskat)abstract
- Chloride anation of trans-Pt(CN)4ClOH2− has been studied with and without Pt(CN)42− present at 25.0°C by use of stopped-flow and conventional spectrophotometry and a 1.00 M perchlorate medium. The rate law in the absence of Pt(CN)42− is compatible with a chloride assistance via an intermediate of the type Cl-Cl-Pt(CN)4···OH22−, in which the reactivity of the aqua ligand is enhanced due to a partial reduction of the platinum. This mechanism of halide assistance is in principle the same as the modified reductive elimination oxidative addition (REOA) mechanism proposed by Poë, in which the intermediate is not split into free halogen, platinum(II) and water, and in which electron transfer not necessarily involves complete reduction to platinum(II). To avoid confusion with complete reductive eliminations, reactions without split of the intermediates are here termed halide-assisted reactions. The pH-dependence indicates acid catalysis via a protonated intermediate ClClPt(CN)4···OH3−.Reaction between PtCl5OH2− and chloride is accelerated by Pt(CN)42− and gives PtCl62− as the reaction product. The rate law is derived at 35.0°C and for a 1.50 M perchlorate acid medium. The reaction takes place without central ion exchange. Alternative mechanisms with two consecutive central ion exchanges can be excluded. The role of Pt(CN)42− in this reaction is very similar to that of the assisting halide in the halide assisted anations. [p ]Reaction between trans-Pt(CN)4ClOH2− and PtCl42− gives Pt(CN)42− and PtCl5OH2− as products. The formation of an aqua complex as the primary reaction product and the rate independent of [Cl−] shows that formation of a bridged intermediate of the type Pt(II)Cl4ClPt(IV)(CN)4OH23− is formed in the initial reaction step, not five-coordinated PtCl53−.
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| 2. |
- Elding, Lars Ivar, et al.
(författare)
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A Tetra-Nitrato Complex of Platinum(II), Synthesis and Crystal Structure of K2[Pt(NO3)4].1/2H2O
- 1985
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Ingår i: Inorganica Chimica Acta. - 0020-1693. ; 103:2, s. 127-131
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Tidskriftsartikel (refereegranskat)abstract
- K2[Pt(NO3)4]·Full-size image (<1 K)H2O was prepared from ca 0.4 M solutions of platinum(II) perchlorate in perchloric acid by addition of KHCO3 and KNO3. Its crystal structure was determined from X-ray intensity data collected with a CAD-4 diffractometer. Monochromatic MoKα-radiation was used. The space group is I4/m with Z = 4; a = 7.5277(4) and c = 20.470(3) Å. The refinement converged to R = 0.036. The structure contains discrete complexes, [Pt(NO3)4]2−, with symmetry C4. Pt coordinates four O from different unidentate nitrato groups. The PtO distance is 2.010(5) Å. The coordination around Pt is distorted square-planar, with Pt situated 0.14 Å above the plane formed by four O, so that a very flat, square pyramid is formed. Two such pyramids on each side of the mirror plane are packed together with their bases facing each other. The closest OO distance between them is 3.29(1) Å and the PtPt distance is 3.590(1) Å. The potassium ions are located between the pairs of complexes so that a three-dimensional packing of K+ and 2×[Pt(NO3)4]2− is formed.
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| 3. |
- Elding, Lars Ivar, et al.
(författare)
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Solvent Paths for Square-Planar Substitutions : Part 2. Reactions between Aqua Chloro-Platinates(II) and Ethene
- 1980
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Ingår i: Inorganica Chimica Acta. - 0020-1693. ; 38:1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- The kinetics for the reactions between the complexes PtCln(H2O)4-n 2−n, n = 0,1,2,3,4, (including cis- and trans-isomers for n = 2) and ethene have been studied. In the case of trans-PtCl2(H2O)2, product analysis shows that both the chloride ligand and the aqua ligand are substituted by ethene in two parallel paths, differing in rate by a factor of 1.5 only. The experiments show that ethene, and probably olefins in general, are inefficient entering ligands, similar to dimethyl sulfoxide. Steric reasons might be responsible. Changes in relative cis- and trans-effects are compatible with an associative mechanism. The aqua complexes are sufficiently reactive with ethene to be steady-state intermediates in associative solvent paths. Reaction models and rate laws for associative square-planar substitutions are discussed, with special reference to reported non-reactivity of solvento intermediates in some previously studied systems.
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| 4. |
- Elding, Lars Ivar, et al.
(författare)
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Stabilities, Solubility and Kinetics and Mechanism for Formation and Hydrolysis of some Palladium(II) and Platinum(II) Iodo Complexes in Aqueous Solution
- 1986
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Ingår i: Inorganica Chimica Acta. - 0020-1693. ; 117:1, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- Complex formation between Pd(II), Pt(II) and iodide has been studied at 25 °C for an aqueous 1.00 M perchloric acid medium. Measurements of the solubility of PdI2(s) in aqueous mercury(II) perchlorate and of AgI(s) and PdI2(s) in aqueous solutions of Pd2+(aq) and Ag+(aq) gave the solubility product of PdI2(s) as Kso=(7±3) × 10−32 M3, which is much smaller than previous literature values.The stability constants β1=[MI(H2O)3+]/([M(H2O)42+][I−]) for the two systems were obtained as the ratio between rate constants for the forward and reverse reactions.The following values of k1 (s−1 M−1), k−1 (s−1) and β1 (M−1) were obtained at 25 °C: (1.14±0.11) × 106, (0.92±0.18), (12±4) × 105 for MPd, and (7.7±0.4), (8.0±0.7) × 10−5, (9.6±1.3) × 104 for MPt. Combination with previous literature data gives the following values of log(β1 (M−1)) to log(β4 (M−4)): 6.08, ∼22, 25.8 and 28.3 for MPd, and 4.98, ∼25, ∼28, and ∼30 for MPt. The present results show that the large overall stability constants β4 observed for the M2+I− systems are most likely due to a very large stability of the second complex MI2(H2O)2, which is probably a cis-isomer. A distinct plateau in the formation curve for mean ligand number 2 is obtained both for MPd and Pt. The other iodo complexes are not especially stable compared to those of chloride and bromide.ΔH≠ (kJ mol−1) and ΔS≠ (JK−1 mol−1) for the forward reaction of (i), MPd, are (17.3±1.7) and (−71±5), and for the reverse reaction of (i) MPd, (45±3) and (−95±6), respectively. The kinetics are compatible with associative activation (Ia). The contribution from bond-breaking in the formation of the transition state seems to be less important for Pd than for Pt.
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| 5. |
- Elding, Lars Ivar, et al.
(författare)
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Synthesis and Crystal Structure of Potassium Tetranitrato Palladate(II)
- 1986
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Ingår i: Inorganica Chimica Acta. - 0020-1693. ; 114:1, s. 71-74
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Tidskriftsartikel (refereegranskat)abstract
- K2[Pd(NO3)4] has been prepared and its crystal structure determined by use of a CAD-4 diffractometer with monochromatic Mo Kα radiation. The space group is P21/c with Z = 4; a= 7.940(2); b = 15.469(4); c = 9.453(2) Å; β = 91.10(3)°. The refinement converged to R = 0.023. The structure contains discrete complexes of [Pd(NO3)4]2− with pseudo-symmetry C4. Pd coordinates four oxygens from different unidentate nitrato groups. The average Pd-O distance is 2.000(7) Å. The coordination around Pd is distorted square planar, with Pd situated 0.139 A above the plane through the four coordinated oxygens. Similar to [Pt(NO3)4]2−, but in contrast with [Au(NO3)4]−, all four nitrato ligands are situated on the same side of the coordination plane forming a basket-like structure. This is probably due to interactions between the non-coordinated oxygens of the nitrato ligands and suitably located potassium ions. Comparison with the structure of cis-[Pd- (NO3)2(DMSO)2] indicates strong groundstate trans-influence of dimethyl sulfoxide in palladium complexes.
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| 6. |
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