Abstract
Poly[tris-(acetato-κ(2) O,O')(μ2-acetato-κ(3) O,O':O)tetra-kis-(μ3-acetato-κ(4) O,O':O:O')bis-(benzene-1,2-di-amine-κN)tetra-lead(II)], [Pb4(CH3COO)8(C6H8N2)2] n , (I), poly[(acetato-κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(4-chloro-benzene-1,2-diamine-κN)lead(II)], [Pb(CH3COO)2(C6H7ClN2)] n , (II), and poly[(κ(2) O,O')(μ3-acetato-κ(4) O,O':O:O')(3,4-di-amino-benzo-nitrile-κN)lead(II)], [Pb(CH3COO)2(C7H7N3)] n , (III), have polymeric structures in which monomeric units are joined by bridging acetate ligands. All of the Pb(II) ions exhibit hemidirected coordination. The repeating unit in (I) is composed of four Pb(II) ions having O6, O6N, O7 and O6N coordination spheres, respectively, where N represents a monodentate benzene-1,2-di-amine ligand and O acetate O atoms. Chains along [010] are joined by bridging acetate ligands to form planes parallel to (10-1). (II) and (III) are isotypic and have one Pb(II) ion in the asymmetric unit that has an O6N coordination sphere. Pb2O2 units result from a symmetry-imposed inversion center. Polymeric chains parallel to [100] exhibit hydrogen bonding between the amine and acetate ligands. In (III), additional hydrogen bonds between cyano groups and non-coordinating amines join the chains by forming R 2 (2)(14) rings.
Highlights
Metal–organic frameworks (MOFs) are of inherent interest in areas such as gas storage, catalysis, chemical sensors and molecular separation (Dey et al, 2014; Kreno et al, 2012; Farha & Hupp, 2010)
Hemidirected geometry is favored over halodirected geometry for PbII when hard ligands are present, which corresponds to a greater ionic character in the metal–ligand bonding (Shimoni-Livny et al, 1998), or when one or more of the ligands is anionic (EstebanGomez et al, 2006)
The results of a reduced variational space (RVS) analysis suggest that more sterically crowded, hemidirected structures are stabilized by polarization of the lead(II) ion induced by the ligand arrangement (Devereux et al, 2011)
Summary
Metal–organic frameworks (MOFs) are of inherent interest in areas such as gas storage, catalysis, chemical sensors and molecular separation (Dey et al, 2014; Kreno et al, 2012; Farha & Hupp, 2010). We reported the synthesis and structural characterization of two zinc MOFs possessing bridging acetate ligands and monodentate chloro- or cyanosubstituted o-phenylenediamine ligands (Geiger & Parsons, 2014). These complexes possess a ladder–chain structure with an ethanol molecule that occupies a void with a volume of approximately 224 A 3. The results of a reduced variational space (RVS) analysis suggest that more sterically crowded, hemidirected structures are stabilized by polarization of the lead(II) ion induced by the ligand arrangement (Devereux et al, 2011). E70, 566–572 enhancing the volume of void space between chains found in coordination polymers provided the impetus for the synthesis and structural characterization of the compounds reported
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