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 degreesC by k = 1.6 x 10(2) mol(-1) dm(3) s(-1). The equilibrium constants for adding hydroxide to [Pt(bpy)(2)](2+) and to [Pt(3,3 '-[H-2](2)-bpy)(2)](2+) are the same, but differ considerably from those for [Pt([H-2](8)-bpy)(2)](2+) and for [Pt(6,6 '-[H-2](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 H-1 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.
-
Kapsamı
Uluslararası
-
Type
Hakemli
-
Index info
WOS.SCI
-
Language
English
-
Article Type
None
-
Keywords
platinum(II) palladium(II) complexes with pyridine (py) 2 2 '-bipyridine (bipy) 1 10-phenanthroline (phen) 2 2 ' 2 ''-terpyridine (terpy) equilibrium constant with hydroxide electronic spectra (UV-Vis CD) NMR spectra (H-1 C-13 Pt-195) deuterium substitution kinetic isotope effect Pfeiffer effect Cotton effect