Abstract
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 language | English (US) |
|---|---|
| Pages (from-to) | 641-665 |
| Number of pages | 25 |
| Journal | Croatica Chemica Acta |
| Volume | 74 |
| Issue number | 3 |
| State | Published - Aug 2001 |
| Externally published | Yes |
Keywords
- 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
- General Chemistry