Volatile zirconium bis(acetylacetonato)bis(alcoholato) complexes containing heterosubstituted alcoholato ligands

Two new heteroleptic compounds Zr(acac)(2)(OR)(2), R = SiMe3 and CH(CF3)(2) , have been synthesized by high-yield synthetic routes. Zr(acac)(2)(OSiMe3) (2), 1, is formed by a salt elimination reaction between Zr(acac)(2)Cl-2 an d lithium trimethylsilanolate in pentane, while Zr(acac)(2)(hfip)(2), 2, hf ip OCH(CF3)(2), has been prepared from Zr(acac)(2)Cl-2 and a mixture of 2 e quiv each of 1,1,1,3,3,3-hexafluoroisopropanol and diethylamine in pentane. The reactions are very selective; the formation of products with other tha n the 2:2 stoichiometry was not observed under the conditions applied. Both the liquid 2 and the low-melting solid 1 are monomeric and distillable or sublimable in a vacuum. A measured dipole moment of 3.94 D together with Sp ectroscopic data of 1 confirms a cis-octahedral structure, with the metal i n a six-coordinated environment. Both substances show an improved hydrolysi s stability over homoleptic tetraalcoholates such as Zr(O-t-Bu)(4), while b eing much more volatile than P-diketonates such as Zr(thd)(4) or Zr(hfac)(4 ). According to preliminary experiments, Zr(acac)(2)(hfip)(2) is a promisin g precursor for metal-organic chemical vapor deposition (MOCVD) of zirconia thin films.