_∞~1[M~(II)(ADC)_(2/2)(DMF)_2(H_2O)_2](M~(II) = Mn, Co, Ni, Zn): Four new coordination polymers with acetylenedicarboxylate (ADC~(2-)) as bridging ligand

摘要

Single crystals of _∞~1[M~(II)(ADC)_(2/2)(DMF)_2(H_2O)_2](M~(II) = Mn (1), Co (2), Zn (4)) precipitated from DMF solutions containing Mn(NO_3)_2 - 6H_2O, CoCl_2 - 6H2O or Zn(NO_3)_2 - 6H_2O and acetylenedicarboxylic acid (H_2ADC). Single crystals of _∞~1[Ni(ADC)_(2/2)(DMF)_2(H_2O)_2] (3) formed at the phase boundary of an aqueous silica gel containing H_2ADC and a DMF solution of NiCl_2 - 6H_2O. The crystal structures were solved and refined from X-ray single-crystal data. All compounds crystallize in space group C2/c with Z = 4. _∞~1[M~(II)(ADC)_(2/2)(DMF)_2(H_2O)_2] chains are the characteristic structural feature. Within these chains MnC>6 octahedra are formed, the oxygen atoms belong to two DMF, two water and two ADC~(2-) ligands. The ADC~(2-) ligands are trans coordinating in an unidentate way, thus connecting the octahedral units to chains. The DMF and water molecules are in a cis coordination to each other. Hydrogen bonds (0- 0:2.83-2.845 A) connect two polymeric chains. These double chains are held together by van der Waals interactions to form a 3D structure. Coupled DTA-TG-MS measurements on 3 and 4 show that 3 decomposes at 146 °C and 4 at 114 °C releasing H_2O, C_2H_2, CO, CO_2, and DMF. But the proceeding decomposition reactions in both compounds are quite different, as the residue after heating at 500 °C in an argon atmosphere is elemental Ni and graphite for 3 and ZnO for 4 as proven by XRPD experiments. This is in agreement with a general trend found for the decomposition of metal acetylenedicarboxylates: with noble metals the elements are formed, whereas with less noble metals the respective oxides are found.