Equilibria in complexes of N-heterocycles. Part 50.1 the formation and properties in solution of the 1:1 adducts of bis(2,2′-bipyridine)platinum(II) and related ions with hydroxide

Armanda Maria Formigao Gameiro, Robert D. Gillard, Norman H. Rees, Jurgen Schulte, Abdurrahman Sengül

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Equilibrium constants are given for addition (mol ratio 1:1) of hydroxide to several palladium(II) and platinum(II) cations. [Pt(bpy)2]2+ (bpy: 2,2′-bipyridine) and hydroxide ion form the well-known 1:1 adduct rapidly in water; the rate is given at 25°C by k = 1.6 × 102 mol-1 dm3 s-1. The equilibrium constants for adding hydroxide to [Pt(bpy)2]2+ and to [Pt(3,3′-[2H]2-bpy)2]2+ are the same, but differ considerably from those for [Pt([2H]8-bpy)2]2+ and for [Pt(6,6′-[2H]2-bpy)2]2+ with hydroxide. In this reaction, the infrared spectrum (1700-900 cm-1) of the cation initially [Pt(bpy)2]2+ in the aqueous solution shows distinct changes between pH = 7.0 and pH = 11.0, notably in the aromatic region, where the intensity of the band due to C=N at ca. 1600 cm-1 is much reduced. At pH = 7.0, the methyl groups in [Pt(5,5′-dmbpy)2]2+ (dmbpy: dimethyl-2,2′-bipyridine) or the 4,4′-isomer are equivalent in 1H magnetic resonance but become inequivalent in the 1:1 adducts with hydroxide. In the presence of (-)-methylbenzylamine, both [Pt(terpy)Cl]Cl (terpy: 2,2′,2″-terpyridine) and [Pt(bpy)2]2+ manifest a strong Pfeiffer effect, but not the 'exciton' coupling characteristic of cis-octahedral ions. These observations are interpreted in terms of addition of hydroxide to the bipyridine ligands.

Original languageEnglish (US)
Pages (from-to)641-665
Number of pages25
JournalCroatica Chemica Acta
Issue number3
StatePublished - Aug 1 2001



  • 1,10-phenanthroline (phen)
  • 2,2′,2″-terpyridine (terpy)
  • 2,2′-bipyridine (bipy)
  • Complexes with pyridine (py)
  • Electronic spectra (UV-Vis, CD)
  • Equilibrium constant with hydroxide
  • Palladium(II)
  • Platinum(II)

ASJC Scopus subject areas

  • Chemistry(all)

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