Formula omitted](M II = Mn, Co, Ni, Zn): Four new coordination polymers with acetylenedicarboxylate (ADC 2−) as bridging ligand

Abstract

Single crystals of [ M II ( ADC ) 2 / 2 ( DMF ) 2 ( H 2 O ) 2 ] ∞ 1 (M II = Mn ( 1), Co ( 2), Zn ( 4)) precipitated from DMF solutions containing Mn(NO 3) 2 · 6H 2O, CoCl 2 · 6H 2O or Zn(NO 3) 2 · 6H 2O and acetylenedicarboxylic acid (H 2ADC). Single crystals of [ Ni ( ADC ) 2 / 2 ( DMF ) 2 ( H 2 O ) 2 ] ∞ 1 ( 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. [ M II ( ADC ) 2 / 2 ( DMF ) 2 ( H 2 O ) 2 ] ∞ 1 chains are the characteristic structural feature. Within these chains M IIO 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 (O⋯O: 2.83–2.845 Å) 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.