Zirconium complexes with halide ligands

Cationic zirconium complexes (88) having diketonato ligands were examined for selective epoxide ring opening (Equation 40) [45]. The catalysts showed higher activity than simple metal halides such as TiCU and ZrCU, and various epoxides (87) were converted into (89) and/or (90) effectively. When R and R" in (87) were alkyl groups, the product selectivity of the catalyst (88) were moderate to low. But with styrene oxide (R =Ph, R" =H), alkoxy alcohol (89) was obtained with high selectivity. 

Reduction of ZrIV in ZrX4-Al2X6 (X = Cl, Br or I) melts, with either zirconium or aluminum metal, yields soluble blue species. These species were not isolated, but they have been formulated as Zr(X2AlX2)3 complexes on the basis of their electronic spectra. Absorption bands at 17 400 (X = C1), 16 000 (X = Br) and 14 000 cm-1 (X = I) may be assigned to the 2t -2es transition of Zr111 in an octahedral environment of halide ions. The solid zirconium(III) halides exhibit ligand-field bands at closely similar frequencies.32... 

Table 4 Complexes of Zirconium(IV) and Hafnium(IV) Halides with N-heterocyclic Ligands...

Zirconium and hafnium tetraalkoxides are highly reactive compounds. They react with water, alcohols, silanols, hydrogen halides, acetyl halides, certain Lewis bases, aryl isocyanates and other metal alkoxides. With chelating hydroxylic compounds HL, such as j8-diketones, carboxylic acids and Schiff bases, they give complexes of the type ML (OR)4 these reactions are discussed in the sections dealing with the chelating ligand. 

Transition metal p-diketiminate complexes are typically prepared by one of three routes. In one, these complexes are prepared by the reaction of a metal halide with an alkali metal P-diketiminate generated from the reaction of the p-diketiminate with an alkali metal base. An example of this synthesis is shown for the scandium system in Equation 4.51 In a second method, these complexes are prepared by the reaction of a transition metal complex containing a basic ligand, such as an alkyl or amido group, with the neutral p-diketimine. Two examples of this route for zirconium systems are shown in Equations 4.52 and 4.53, 3... 

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