Dimetric molecules of Co(II) and Zn(II) complexes with furan-2-carboxylate ligands stabilized by the system of interconnected C-H...O-water, O-water-H...O-furan and O-water-H...pi hydrogen bonds

The crystals of cobalt furoate{bis(my-furan-2-carboxylato-O,O')-(my-furan-2-carboxylato-O,O,O')-(furan-2-carboxylato-O)-bis[diaquacobalt(II) dihydrate} are isostructural with the crystals of zinc furoate. They contain dimeric molecules. Two independent metal ions are connected to each other by three carboxylate bridges (one O:O,O and two O:O) from furan-2-carboxylate anions. The distorted octahedral environments of metal ions differ in the way of binding one of the furan-2-carboxylate ligands: monodentate in the case of Co(1) [Zn(1); bidentate in the case of Co(2) [Zn(2)]. The heteroring oxygen atoms do not coordinate directly the metal ions; their electrondonor properties manifest themselves by formation of O-water-H...O-furan contacts. Both structure exhibit intermolecular hydrogen bonds involving all O-water atoms, and also weak contacts to carbon atoms from furan rings as donors. Carbonyl and furan oxygen atoms and pi elecron of the furan rings are proton acceptors in these hydrogen bonds.