Synthesis, characterization and structures of solvent-mediated Na(I)-Pd(II) heterometallic complexes containing [Pd(barb)(4)](2-) units (barb=5,5-diethylbarbiturate)

Abstract

Reaction of Na-2[PdCl4] with the sodium salt of 5,5-diethylbarbituric acid (barbH) led to the formation of two complexes, [PdNa2(-barb)(4)(DMSO)(2)]2H(2)ODMSO (1), and {[PdNa2(-barb)(4)(H2O)]3H(2)O}(n) (2). The complexes were characterized by elemental analysis, FT-IR, NMR, and X-ray crystallography. Complex 1 was crystallized from H2O/DMSO (1:1, v:v) and 2 was crystallized in H2O. Both complexes contain square planar [Pd(barb)(4)](2-) moieties, in which Pd(II) is coordinated by four barb ligands via the negatively charged nitrogens. In addition to the coordination of a DMSO ligand, two Na(I) ions in 1 are bridged by carbonyl O of four barb ligands in the [Pd(barb)(4)](2-) unit, while the Pd(II) and Na(I) ions in 2 are bridged by the barb ligands in a tetradentate bridging fashion leading to a 2-D polymeric network. The bridging of metal centers in both complexes result in a significantly short Na-Pd distance of ca. 2.95 angstrom. Contrary to 2, the coordination of DMSO to Na(I) in 1 avoids the extension of the polymeric structure.