3,5-Lutidine coordinated zinc(II) aryl carboxylate complexes: Precursors for zinc(II) oxide

摘要

The reaction of Zn(κ~2O,O′-OAc)_2· 2H_2O with two equiv of 3,5-lutidine in methanol at room temperature for 12 h afforded [Zn(OAc)_2(3,5-lutidine)_2]· H _2O (1) in 91% yield. The acetate exchange reaction of 1 with two equiv of aryl carboxylic acids in methanol at room temperature for 12 h afforded [Zn(μ_2-κ~1O:κ~1O′-O _2CAr)_2(3,5-lutidine)]_2 [Ar = C _6H_5 (2) and C_6H_4Me-3 (3)], [Zn(OC(O)C_6H_4Me-2)_2(3,5-lutidine)_2] (4) and [Zn(κ~2O,O′-O_2CC_6H _4Me-4)_2(3,5-lutidine)_2] (5) in ≥90% yield. Complexes 1-5 were characterized by microanalytical, IR, solution (~1H and ~(13)C) and solid-state cross-polarization magic angle spinning ~(13)C NMR and X-ray diffraction data. The zinc atom in 1 is surrounded by nitrogen atom of two 3,5-lutidine and oxygen atom of two monodentate acetate moiety and thus attains a tetrahedral geometry. One of the acetate moieties is hydrogen bonded with a water molecule in the crystal lattice. Complexes 2 and 3 possess a dinuclear paddlewheel framework with a square pyramidal geometry around the zinc atom whereas 4 and 5 are mononuclear species with the zinc atom in tetrahedral and an octahedral geometry, respectively. Thermogravimetric analyses of 2-5 suggested ZnO as the decomposed product followed by the confirmation from the powder X-ray diffraction patterns. Enormous gas evolution resulting in porous ZnO during thermal decomposition was evidenced from scanning electron microscopic images.