Zirconium tetraisopropoxide

Zirconium alkoxides readily hydrolyze to hydrous zirconia. However, when limited amounts of water are added to zirconium alkoxides, they partially hydrolyze in a variety of reactions depending on the particular alkoxide (222). Zirconium tetraisopropoxide [2171 -98-4] reacts with fatty acids to form carboxjiates (223), and with glycols to form mono- and diglycolates (224). 

Hoveyda and Snapper reported that the addition of mixed alkynylzinc reagents to various aryl imines can be catalyzed by Schiff base ligand 52 and zirconium tetraisopropoxide to afford the protected propargylamines in good yields and enantioselectivities [130]. The oxidative removal of the o anisidyl group affords the propargylamine without any racemization (Scheme 1.40). 

The differences in solubility of metal isopropoxides and their alcoholates have led to the crystallization of pure isopropoxide isopropanolates of some tetravalent elements. For example, zirconium tetraisopropoxide is a viscous supercooled liquid which dissolves in excess of isopropyl alcohol and crystallizes out in the form of pure white crystals which were characterized as Zr(OPr )4.Pr OH. Similarly tin tetraisopropoxide and cerium tetraisopropoxide have been obtained as crystalline alcoholates, Sn(OPr )4.Pr OH ° and Ce(OPP)4.Pr OH which were used as the starting materials for the synthesis of a number of new alkoxides. 

There have been many previous studies on zirconium compounds of the so-called fatty acids, which upon analysis are usually found to be oxy species. For example, the reaction of excess steric or palmitic acids with the isopropyl alcohol solvate of tetraisopropoxide zirconium (280, 281) in benzene at reflux temperatures gives final products which are consistent with the composition [(RC00)3Zr]20. Actually this reaction can be carried out so as to isolate the mono- and disubstituted alkoxides, Zr(RCOO)(OPr )3andZr(RCOO)2(OPr )2. Treatment of the disubstituted product with additional fatty acid in benzene gives products for which... 

Hydrolysis studies of secondary and tertiary alkoxides (69) indicate that the degree of polymerization of secondary alkoxides in benzene is lower than for the normal alkoxides, whereas the teritary alkoxides are monomeric. Thus the hydrolysis data on tetraisopropoxide zirconium and tetra-sec-butoxide zirconium are consistent with the model (2) hypothesis, while the hydrolysis data of tetra-ter<-amyloxide fit the model (3) hypothesis. Additionally, crystal structure data on tetraisopropoxide... 

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