Synthesis and Structure of Heterometallic Compounds with Dimethyl Pyridine-2,6-dicarboxylate

Dimethyl pyridine-2,6-carboxylate (L) was prepared by refluxing pyridine-2,6-dicarbonyl dichloride in methanol. The reactions of L with Ca(II), Sr(II), and Ba(II) salts and with cobalt(II) thiocyanate resulted in the formation of three heterometallic complexes: [CaL3][Co(NCS)(4)] (I), [SrL3][Co(NCS)(4)] (II), and [BaCoL3(mu-NCS)(2)(NCS-kappa N)(2)] (III). The composition and structure of compounds L and I-III were determined by elemental analysis, infrared spectroscopy, and X-ray diffraction (CCDC nos. 2166019-2166022, respectively). It was found that isostructural Ca(II) and Sr(II) compounds are ionic and are formed by the [CaL3](2+) and [SrL3](2+) complex cations and [Co(SCN)(4)](2-) complex anion, while the Ba(II) derivative is a molecular complex in which [BaL3](2+) and [Co(NCS)(4)](2-) moieties are linked by two (NCS)(-) bridging units of the complex anions. In any of the three compounds, three tridentate L ligands are coordinated to the alkaline earth metal ion.