Syntheses and characterization of two monomeric zinc complexes containing aqua ligands

Two monomeric zinc complexes, [Zn(H(2)brim)(2)(H2O)(2)](OAc)(2) . OHCH2CH2O H (H(2)biim = 2,2'-biimidazole) (1) and [Zn(bipy)(2)(H2O)(CF3CO2)](ClO4) (b ipy = 2,2'-bipyridine) (2), have been synthesized and characterized by NMR and single-crystal structural analysis. The zinc ions in both complexes are coordinated in a distorted N4O2 octahedral geometry: the zinc ion in compl ex 1 is surrounded by two aqua [Zn-O 2.150 (3) Angstrom] and two H-2 biim l igands (Zn-N 2.150 Angstrom), the acetate groups act as counter-anions and form hydrogen bonds with H(2)biim; the zinc ion in 2 is ligated by two bipy ligands (Zn-N 2.144 Angstrom), one aqua molecule [Zn-O 2.148(2) Angstrom] and one monodentate carboxylate [Zn-O 2.154(2) Angstrom]. In both complexes , the aqua li;:and forms strong donor hydrogen bonds with the hydroxyl or c arboxylate groups, being analogous to those found for the active sites of s everal zinc enzymes. (C) 1999 Elsevier Science Ltd. All rights reserved.