Coordinating properties of 2-acetylpyridine thiosemicarbazone. Palladium(II) complexes with neutral and deprotonated ligand. X-ray structure of bromo(2-acetylpyridine thiosemicarbazonato) palladium(II)

Publisher Summary This chapter reviews the substituent tautomerism of six-membered heterocycles that has appeared since 1976. The most significant development since 1976 is the enormous emphasis on the computational studies. Recent advances in computer technology in combination with increasingly accurate quantum-chemical methods, allow studies of systems of up to 50 atoms on standard personal computers at relatively high levels. Computational chemistry has become increasingly important in traditional heterocyclic chemistry. It discusses the generalized approach to the tautomerism phenomenon and its studies using theoretical, physical spectroscopic, non-spectroscopic, and chemical methods. The chapter also reviews the effect of introduction of an additional heteroatom; inductive substituents, mesomeric substituents, and the effect of benzannulation on the position of the tautomeric equilibrium of azines with various functional groups were investigated by PMO semiempirical calculations.

The Tautomerism of Heterocycles: Substituent Tautomerism of Six-Membered Ring Heterocycles

Metal complexes of the anti-inflammatory drug sodium [2-[(2,6-dichlorophenyl)amino]phenyl]acetate (diclofenac sodium). Molecular and crystal structure of cadmium diclofenac

Three novel dinuclear palladium(II) complexes with the chelating ligand bis(1-methylimidazol-2-yl) ketone (bmik) as well as pyridine-2-thiolate (pyt), pyrimidine-2-thiolate (pymt), and 1-methylimidazole-2-thiolate (meimt) as bridging secondary ligands were prepared by reactions of diaqua[bis(1-methylimidazol-2-yl) ketone]palladium(II) nitrate with the ligands in aqueous solution. The thiolates bridge the two metal atoms in the μ-N,S mode. The structures of the following compounds were analyzed by single crystal X-ray diffraction: Bis(μ-pyridine-2-thiolato-N,S)-bis{[bis(1-methyl-imidazol-2-yl) ketone]palladium(II)}nitrate [Pd2(bmik)2-(pyt)2](NO3)2 · 5 H2O (1), bis(μ-pyrimidine-2-thiolato-N1,S)- bis{[bis(1-methylimidazol-2-yl) ketone]palladium(II)} nitrate [Pd2(bmik)2(pymt)2](NO3)2 · 5 H2O (2), and bis(μ-1-methyl-imidazole-2-thiolato-N3,S)-bis{[bis(1-methylimidazol-2-yl) ketone]palladium(II)} nitrate [Pd2(bmik)2(meimt)2](NO3)2 · 4.5 H2O (3). In the cases of 1 and 3 the bridging thiolate ligands show head-to-head orientation. For complex 2 a head-to-tail orientation of the pyrimidine-2-thiolates was found. The metal-metal distances vary from 2.963 A in complex 3 and 2.915 A in 1 to the shortest of 2.886 A in 2. In addition to the X-ray crystallography the three compounds were characterized by 1H-NMR and IR spectroscopy.

Novel dinuclear palladium(II) complexes with the chelating ligand bis(1‐methylimidazol‐2‐yl) ketone (bmik) and pyridine‐2‐thiolate, pyrimidine‐2‐thiolate, and 1‐methylimidazole‐2‐thiolate as bridging secondary ligands

The complexes dimethyldi(pyrimidine-2-thiolato)tin(IV) (1) and diphenyldi(pyrimidine-2-thiolato)tin(IV) (2) have been structurally ­characterized by means of X-ray crystallography. Complex 1 exhibits strong π–π stacking interactions and adduct 2 is self-assembled via intermolecular hydrogen bonds, CH–π and π–π stacking interactions. Partial solvolysis occurs in organic solvents for 1 and 2. Copyright © 2000 John Wiley & Sons, Ltd.

Paraskevi Kyrkou

Papers

The synthesis and characterization of pyrimidine-2-thione complexes of palladium(II)