Synthesis and Crystal Structures of Two Monomeric Zinc(II) Complexes Containing Carboxylate and Aqua Ligands

Abstract

Two monomeric zinc(II) complexes of betaine (Me₃N⁺CH₂CO₂¯ = bet), [Zn(bet)₂(H₂O)Cl] (ClO₄) (1) and [Zn(bet)₃(H₂O)] (ClO₄)₂ (2), have been prepared and characterized by single-crystal structural analysis. The zinc atom in both complexes is coordinated in a distorted tetrahedral geometry: the zinc atom in complex (1) is surrounded by one aqua ligand (Zn–O 1·979(3) Å), one chloro ligand (Zn–Cl 2·218(1) Å ) and two monodentate carboxylate groups (Zn–O 1·946(2) Å); the zinc atom in complex (2) is ligated by one aqua ligand (Zn–O 1·997(6) Å) and three monodentate carboxylategroups (Zn–O 1·943(5)–2·106(8) Å). In both complexes, the aqua ligand forms strong donor hydrogenbonds with adjacent carboxylate oxygens (for complex (1), O · · · O is 2·689(2) Å; for complex (2), O · · · O are 2·67(1) and 2·709(8) Å); these interactions are discussed in the context of zinc complexesand enzyme active sites.