A Proton Transfer Compound of Piperazine with Pyridine‐2,6‐dicarboxylic Acid and Its Palladium(II) and Thallium(III) Complexes – Synthesis, Characterization and Crystal Structure

Abstract

Abstract Three compounds including a proton transfer ion pair LH 2 and its Pd II and Tl III complexes were synthesized and characterized using 1 H NMR, 13 C NMR, IR spectroscopy and single crystal X‐ray diffraction method. The chemical formulae are (pipzH 2 ) 2+ (pydc) 2− for ion pair 1 , (pipzH 2 )[Pd(pydc) 2 ]·2H 2 O for Pd II complex 2 , and (pipzH 2 )[Tl 2 (pydc) 2 Cl 4 (H 2 O) 2 ]·4H 2 O for Tl III complex 3 , respectively (pipz: piperazine, pydc: pyridine‐2,6‐dicarboxylate). The space group and crystal system of all three compounds are P 1 and triclinic. The proton transfer ion pair 1 was prepared by a reaction between piperazine and pyridine‐2,6‐dicarboxylic acid, and the complexes 2 and 3 were synthesized by reaction of 1 with palladium(II) chloride and thallium(III) nitrate, respectively. In complex 2 , two water molecules present in the crystal packing are joined by hydrogen bonds and form a water dimer and similarly in complex 3 , six water molecules apart from the complex and individually form an interesting water hexamer developed in the whole crystal. Hydrogen bonding and ion pairing play an important role in stabilizing the crystals.