ChemInform Abstract: Synthesis, Crystal Structure, and Thermal Properties of cis‐Pd(NH3)2Br2.

Blokhin, A. I.; Соловьев, Л. А.; Blokhina, M. L.; Yakimov, Igor S.; Кирик, С. Д.

doi:10.1002/chin.199820041

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“…These precautions were undertaken since it is known that acidic palladium(II) solutions containing oxalate decompose slowly (during 24 h) when illuminated by day or artificial light, forming palladium black, probably due to reactions (A) and (B). 22,38…”

Section: Equilibrium Measurementsmentioning

confidence: 99%

“…[16][17][18][19][20] The mechanism for the reaction between palladium(II) and maleic acid, resulting in formation of a palladium(II) olefin complex, has been studied in some detail. 18 Properties and crystal structures of [21][22][23] as well as those for [Pd(NH 3 ) 4 ][Pd(ox) 2 ]. 24 The structural motif with oxalate acting as a bidentate chelating ligand is retained also in the mixed ternary species K 2 [Pt(ox)Cl 2 ]•H 2 O and in the platinum(IV) compound Na 2 [trans-Pt(OH) 2 (ox) 2 ]•6H 2 O.…”

Section: Introductionmentioning

confidence: 99%

“…27 Solid M 2 [Pd(ox) 2 ]•xH 2 O (M = K, Na) or aqueous solutions of Pd (II) and oxalic acid containing chloride decompose slowly to metallic palladium when exposed to sunlight or laser illumination. 21,22,28 A qualitative study of complex formation between palladium(II) and oxalate using UV/VIS and FTIR spectroscopy at 25 °C and pH ≈ 6-7 as a function of the concentrations of chloride and oxalate has shown that palladium(II)-oxalato complexes are formed already at relatively low oxalato concentrations. 6,29 For [Cl − ] > 1 mol kg −1 , only [PdCl 4 ] 2− and one mono-oxalato complex were observed, whereas two oxalato complexes were found for lower chloride concentrations.…”

Section: Introductionmentioning

confidence: 99%

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Thermodynamics for complex formation between palladium(ii) and oxalate

2014

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Complex formation between [Pd(H2O)4](2+) and oxalate (ox = C2O4(2-)) has been studied spectrophoto-metrically in aqueous solution at variable temperature, ionic strength and pH. Thermodynamic parameters at 298.2 K and 1.00 mol dm(-3) HClO4 ionic medium for the complex formation [Pd(H2O)4](2+) + H2ox ⇄ [Pd(H2O)2(ox)] + 2H3O(+) with equilibrium constant K1,H (in mol dm(-3)) are log10K1,H = 3.38 ± 0.08, ΔH = -33 ± 3 kJ mol(-1), and ΔS = -48 ± 11 J K(-1) mol(-1), as determined from spectrophotometric equilibrium titrations at 15.0, 20.0, 25.0 and 31.0 °C. Thermodynamic overall stability constants β (in (mol dm(-3))(-n), n = 1,2) for [Pd(H2O)2(ox)] and [Pd(ox)2](2-) at zero ionic strength and 298.2 K, defined as the equilibrium constants for the reaction Pd(2+) + nox(2-) ⇄ [Pd(ox)n](2-2n) (water molecules omitted) are log10β = 9.04 ± 0.06 and log10β = 13.1 ± 0.3, respectively, calculated by use of Specific Ion Interaction Theory from spectrophotometric titrations with initial hydrogen ion concentrations of 1.00, 0.100 and 0.0100 mol dm(-3) and ionic strengths of 1.00, 2.00 or 3.00 mol dm(-3). The values derived together with literature data give estimated overall stability constants for Pd(ii) compounds such as [Pd(en)(ox)] and cis-[Pd(NH3)2Cl2], some of them analogs to Pt(ii) complexes used in cancer treatment. The palladium oxalato complexes are significantly more stable than palladium(ii) complexes with monodentate O-bonding ligands. A comparison between several different palladium complexes shows that different parameters contribute to the stability variations observed. These are discussed together with the so-called chelate effect.

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Section: Equilibrium Measurementsmentioning

confidence: 99%