Equilibria in complexes of N-heterocycles.: Part 50<SUP>1</SUP>: The formation and properties in solution of the 1:1 adducts of Bis(2,2′-bipyridine)platinum(II) and related ions with hydroxide
RD Gillard, AMF Gameiro, NH Rees, J Schulte, A Sengül
article (Uluslararası, Hakemli) | Yazar(lar): RD Gillard, AMF Gameiro, NH Rees, J Schulte, A Sengül | Yıl: 2001 | Dergi/Kurum: CROATICA CHEMICA ACTA | İndeks: WOS.SCI | Anahtar Kelimeler: platinum(II), palladium(II), complexes with pyridine (py), 2,2 '-bipyridine (bipy), 1,10-phenanthroline (phen), 2,2 ',2 ''-terpyridi
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.