PbADC and PbADC x H2O: Two coordination polymers with acetylenedicarboxylate (ADC2-) as bridging ligand

• Published in: Zeitschrift für anorganische und allgemeine Chemie (1950)
• Main Authors: Ruschewitz, Uwe, Schuy, Andrea, Stein, Irena
• Format: Journal Article
• Language: English
• Published: Wiley-VCH Verlag 12.03.2010
• Subjects: Physical Sciences
• ISSN: 0044-2313; 1521-3749
• DOI: 10.1002/zaac.201000019

Single crystals of PbADC (1) and PbADC x H2O (2) formed at the phase boundary of an aqueous silica gel containing acetylenedicarboxylic acid (HOOC-C≡C-COOH, H2ADC) and an aqueous solution containing Pb(NO3)2. By choosing different concentrations of Pb(NO3)2 1 and 2 were obtained as phase pure products. Additionally, 1 was obtained by grinding Pb(CH3COO)2 x 3 H2O with H2ADC resulting in a polycrystalline sample. The crystal structures of 1 (I41/amd, Z = 4; SrADC type structure) and 2 (P21/c, Z = 4, new structure type) were solved and refined from X-ray single crystal data. 1 exhibits a three-dimensional framework structure: Pb cations with a diamond-like arrangement are interconnected by bridging ADC2- ligands. In 2 double-layers are formed by Pb cations, bridging ADC2- anions and water molecules. These layers are held together by hydrogen bonds via water molecules and oxygen atoms of the ADC2- ligands. Suspending 1 for 24 h in water at ambient conditions leads to the formation of 2, which can be converted to 1 again by careful dehydration at approx. 400 K in vacuum. This reversible reaction can be structurally interpreted as a topochemical reaction, which transforms a 3D coordination network into a 2D network structure and vice versa, as both crystal structures show noticeable structural similarities.