Construction of Zn^II compounds with a chelating 2,2′-dipyridylamine (Hdpa) ligand: Anion effect and catalytic activities

The structures of new compounds containing Zn^II ions and Hdpa (2,2′-dipyridylamine)-chelating ligands were determined. The Hdpa chelating ligands coordinate to Zn^II ions to form mononuclear units (1 and 5), and intermolecular non-classical hydrogen-bond (C-H⋯O or N/C-H⋯I) interactions generate polymeric compounds. The chelating ligands with a bipyridyl moiety form mostly mononuclear complexes of different types (I, II and III), and the combination of this ligand with a sulfate anion can produce polymeric species (Type IV). Interestingly, homogeneous catalyst 1 catalyzed efficiently the transesterification of a variety of esters with different alcohols, and hydrogen-bonded polymer 5 showed the heterogeneous catalytic activity for the transesterification reactions. Preliminary selectivity test of primary over secondary alcohol protection in the presence of 1 provided, exclusively, the primary acetate, which suggests the potential utility of this catalyst to be selective for primary alcohols.