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

The reaction of Zn(κ2O,O′–OAc)2·2H2O with two equiv of 3,5-lutidine in methanol at room temperature for 12 h afforded [Zn(OAc)2(3,5-lutidine)2]· H2O (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(μ2-κ1O:κ1O′–O2CAr)2(3,5-lutidine)]2 [Ar = C6H5 (2) and C6H4Me-3 (3)], [Zn(OC(O)C6H4Me-2)2(3,5-lutidine)2] (4) and [Zn(κ2O,O′−O2CC6H4Me-4)2(3,5-lutidine)2] (5) in ⩾90% yield. Complexes 1–5 were characterized by microanalytical, IR, solution (1H and 13C) and solid-state cross-polarization magic angle spinning 13C 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.