Low-dimensional compounds containing bioactive ligands. Part III: Palladium(II) complexes with halogenated quinolin-8-ol derivatives

Four [Pd(XQ)2] complexes (XQ = 5-chloro-quinolin-8-ol (ClQ), 5,7-dichloro-quinolin-8-ol (dClQ), 5,7-dibromo-quinolin-8-ol (dBrQ) or 5,7-diiodo-quinolin-8-ol (dIQ)) were prepared. X-ray structure analysis revealed that the [Pd(dBrQ)2] (3) and [Pd(dIQ)2] (4) complexes are isostructural centrosymmetric molecular coordination compounds with Pd central atoms square-planarly coordinated by nitrogen and oxygen atoms of two trans-arranged bidentate molecules of XQ. Contrary to the analogous composition of 2 ([Pd(dClQ)2]) it is not isostructural with 3 or 4 and its crystal structure is formed by two independent square-planar [Pd(dClQ)2] molecules. One of them is centrosymmetric, while the second one is pseudocentrosymmetric. Non-bonding interactions between parallel neighboring molecules in these three complexes were also investigated. According to the LeBail (profile fitting) mode of the Rietveld analysis, the microcrystalline [Pd(ClQ)2] (1) complex is not isostructural with 2-4. The complexes were characterized by thermal analysis, which revealed that they are stable up to 335 (1), 320 (2), 325 (3) and 280 °C (4) as well as IR spectroscopy, which proved the presence of XQ in all complexes, and by elemental analysis which confirmed composition of the complexes.