Thermogravimetric and infrared studies of tetrameric zirconium(IV) compounds derived from oxozirconium(IV) chloride and imidazole,morpholine and their derivatives

Oxozirconium chloride reacts with imidazole, morpholine and their derivatives in acetone medium in the presence of triethylorthoformate to form white amorphous compounds with a high melting point. IR and thermogravimetric measurements as well as analytical data indicate their polymeric formulation in the solid state where the structure is derived from the basic tetrameric dodecahedral structure of the parent ZrOCl₂ ·8H₂O formulated as Zr₄(OH)₈(H₂O)₁₆Cl₈. The unidentate imidazole or morpholine ligands appear to replace some of the coordinated H₂O molecules and deprotonate some other H₂O molecules forming compounds of the type Zr₄(OH)₁₂(H₂O)_12−nL_n]Cl₄ where n = 1 for L = 1-MeIm, 1-EtIm, 1-ViIm, 2-iPrIm, 2-PhIm; n = 2 for L = Im, 2-MeIm, 4-MeMorph and n = 4 for L = Morph. Thermogravimetric studies indicate the stepwise loss of water molecules and the ligands forming complex intermediates with increase in temperature. The stoichiometry of decomposition products is calculated. Based on initial decomposition temperature, an order of thermal stability for the complexes is proposed.