Influence of PtII and PdII coordination on the equilibrium of 2,2′-dipyridylketone (dpk) with its hydrated gem-diol form (dpk·H2O)
作者:Anupam Khutia、Pablo J. Sanz Miguel、Bernhard Lippert
DOI:10.1016/j.ica.2010.02.035
日期:2010.10
2,2'-Dipyridylketone (dpk), when acting as a chelating ligand for Pd-II or Pt-II, is in slow equilibrium with its corresponding gem-diol form (dpk center dot H2O). In D2O, equilibrium constants K = (dpk center dot H2O)/(dpk) change from ca. 0.04 for the free ligand to ca. 3 in the corresponding complexes with cis-[Pt(H2O)(2)](2+). In solution, species of both ligands can be identified and differentiated by H-1 NMR spectroscopy, and in the trinuclear mu-OH bridged Pt-II complex [Pt-3(mu-OH)(3)(dpk center dot H2O)(2)(dpk)](NO3)(3)center dot 4.5H(2)O (4), both types of ligands are present simultaneously in a ratio of (dpk center dot H2O):(dpk) = 2. As demonstrated with a series of Pd-II complexes containing dpk center dot H2O and dpk ligands, a straightforward differentiation is possible when DMSO-d(6) is used as solvent, because then also the OH protons of dpk center dot H2O are observable. It is also shown that monocrystalline [PdCl2(dpk center dot H2O)] (1), when dissolved in DMSO-d(6), partially converts, with loss of H2O, to [PdCl2(dpk)]. (C) 2010 Elsevier B. V. All rights reserved.