Two-dimensional oxalate-bridged heterometallic coordination polymer: Crystal structure and thermal behavior of [NaCr(pyim)(ox)2(H2O)] · 2H2O (pyim = 2-(2′-pyridyl)imidazole)

A new coordination polymer of formula [NaCr(pyim)(ox)2(H2O)] · 2H2O (pyim = 2-(2′-pyridyl)imidazole, ox = oxalate) has been prepared and it revealed a novel two-dimensional framework generating from the oxalate-bridged heterometallic CrIII–NaI helical chains with alternative P/M arrangement. Within the 2-D layer, a regular alternation of the metal centers is interconnected by two types of oxalate dianions in common bis(bidentate) ligand and an unusual asymmetric monodentate bonding mode towards a sodium atom of a neighboring chain. The thermal behavior of the complex showed that the lattice and coordinated water molecules to Na+ were lost at low temperature, and that the resulting anhydrous [NaCr(pyim)(ox)2] is thermally stable at 633 K.