[57] New aryloxide derivatives of monochlorotris(acetylacetonato)zirconium(IV) S.S. Bhatt*, Raj Kumari, Neeraj Sharma and S.C. Chaudhry Deptt. of Chemistry, Himachal Pradesh University, Shimla ABSTRACT A series of tris(acetylacetonato)zirconium(IV) aryloxides of composition Zr(acac) 3 (OAr-X) [where acac = acetylacetonato anion; OAr-X=OC 6 H 2 Cl-2,4,6; OC 6 H 3 Cl-2,6; OC 6 H 3 Cl-2,4; OC 6 H 4 Cl-2, and OC 6 H 4 Cl-4] have been synthesized from the reaction of ZrCl(acac) 3 with one equivalent of the substituted phenol in the presence of diethyl amine. These complexes have been characterized by using elemental analyses, molecular weight determinations, molar conductance measurements and thermo analytical (TG/DTA) studies. Based on limited analytical, physico chemical, spectroscopic and molecular modeling technique, a capped trigonal prismatic geometry has been proposed for these complexes. The addition of sodium aryloxides to CCl 4 +MeOH solution of the monomeric Zr(acac) 3 (OAr-X) derivatives have afforded the complexes of composition Na[Zr(acac) 3 (OAr-X) 2 ], which have also been characterized. Keywords: Zirconium(IV), aryloxides, acetylacetonate, chlorophenols, molecular modeling, TG/DTA INTRODUCTION Literature survey reveals a voluminous documentation on the chemistry of zirconium (β-diketonates(1,2), alkoxides (3,4), mixed β- diketonato-alkoxo complexes (5), and their wide applications in material sciences for making thin films by sol-gel (6,7), MOCVD processes involving the hydrolysis of M-OR bonds (8,9), and as catalyst in polymerization (10-12). Surprisingly, little efforts seem to have been made on the synthesis of the closely related aryloxo complexes of zirconium (IV). Therefore, in continuation of previous on going research on the synthesis of zirconium (IV) complexes, we report here the synthesis of monochlorotris(acetylacetonato) aryloxides. An attempt has also been made to propose a suitable geometry for these complexes using molecular modeling technique. MATERIALS AND METHOD Zirconium tetrachloride (Fluka) was purified by sublimation in a vacuum and substituted chlorophenols (s.d.fine) were used as such without further purification. The purity of phenols was checked by their melting point and chlorine estimation. Monochlorotris (acetylacetonato) zirconium (IV) was synthesized by the reported method (16), of reacting ZrCl 4 and acetylacetone using benzene as solvent under reflux. Zirconium in the complexes was determined gravimetrically as ZrO 2 and chlorine by Volhard's method. Carbon and hydrogen microanalyses were performed on a Coleman CHN analyzer. The conductance measurements in nitrobenzene were made on an NDC-732 Elico Digital conductivity bridge and molecular weights were determined by Rast’s Camphor method. Infrared spectra (KBr) were recorded from 4000-200 cm -1 with Perkin Elmer FTIR spectrophotometer and 1 H NMR spectra on a Jeol JNM PMX 60 SI using CCl 4 as solvent. Thermo grams were recorded on a Shimadzu simultaneous DT-40 DT-TG thermal analyzer, heating rate: 10 °C min -1 ; sample size 5-10 mg; reference Al 2 O 3 ; thermocouple: Pt/Pt-Rh 10%. Preparation of tris(acetylacetonato) zirconium(IV} aryloxides, [Zr(acac) 3 (OAr- X)] (OAr-X=OC 6 H 2 Cl-2,4,6; OC 6 H 3 Cl-2,6; OC 6 H 3 Cl-2,4; OC 6 H 4 Cl-2, and OC 6 H 4 Cl-4) International Journal of Theoretical & Applied Sciences, 1(1): 57-63(2009)