Zinc(II) polymeric compounds with a chelating ligand bis(2-pyridylmethyl)amine (bispicam) directed by intermolecular C/N/O-H⋯X (X = Cl, Br, I) interactions: Catalytic activities

Abstract

[Zn(bispicam)2]2+ as a hydrogen-bond donor and three free halides (Cl-, Br- and I-) as hydrogen-bond acceptors were employed to investigate the role of non-classical C/N-H⋯X hydrogen bonding for construction of polymeric compounds. Three zinc salts (ZnCl2, ZnBr2 and ZnI2) were reacted with bis(2-pyridylmethyl)amine (bispicam) to produce [Zn(bispicam)2]Cl2 1, [Zn(bispicam)2]Br2 2 and [Zn(bispicam)2]I2 3. Hydrogen bonding interactions between Namine-H and C-H of [Zn(bispicam)2]2+ cations and free halides, and between Owater-H and free halides can play very important roles for construction of molecular packing and crystal structures. In addition, these hydrogen-bonded complexes 1, 2 and 3 were, interestingly, shown to carry out the catalytic transesterification of a range of esters with methanol at 50 °C under the mild conditions, though all these compounds are saturated with two bispicam ligands. To explain this unusual reactivity, it has been proposed that the hydrogen atom of amine N-H moiety in the complexes could do the acid-catalyzed transesterification. © 2008 Elsevier B.V. All rights reserved.