Gameiro A.M.F. | Gillard R.D. | Rees N.H. | Schulte J. | Sengül A.

Article | 2001 | Croatica Chemica Acta74 ( 3 ) , pp.641 - 665

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 Daha fazlası Daha az