Zirconium oxygen donors

No zirconium(III) complexes with oxygen donor ligands have been isolated. However, the electronic absorption spectra of aqueous solutions of Zrl3 have been interpreted in terms of the formation of aqua complexes (equation 4).29 The spectrum of a freshly prepared solution of Zrl3 exhibits a band at 24 400 cm-1, which decays over a period of 40 minutes, and a shoulder at 22000 cm-1, which decays more rapidly. The 24400 cm-1 band has been assigned to [Zr(H20)6]3+, and the 22000 cm-1 shoulder has been attributed to an unstable intermediate iodo-aqua complex. If it is assumed that the absorption band of [Zr(H20)6]3+ is due to the 2T 2Ee ligand-field transition, the value of A is 24 400 cm. This corresponds to a A value of 20 300 cm-1 for [Ti(H20)6]3+ 30 and 17 400 cm-1 for the octahedral ZrCl6 chromophore in zirconium(III) chloride.25... 

Similar behavior is observed for calix[4]arene (see Calixarenes) complexes of the type (89). Moreover, the oxygen donor atoms are particularly appropriate for the oxophilic early transition metals. A rich chemistry has been developed with complexes containing zirconium - carbon bonds. In this area, aryne zirconocene compounds can be thermally generated and isolated withont trimethylphosphane additional coordination. Zirconium-bntadiene chemistry has been explored as well and constitutes a source of zircoiuum complexes. 

Chiral Oxygen Ligands. Among the oxygen donor ligands, the BINOL-type ones are predominant (68). The parent compound and its 3,3 -dibromo-substituted derivatives form efficient catalysts with titanium and zirconium (Fig. 8). Binaphthol-modified titanium(lV) compounds are efficient catalysts for ene reactions of glyoxylic esters and olefins. The replacement of isopropoxide of the titanium precursor, TiCl2(OiPr)2, is a crucial step in the formation of the catalytic species. 

O-Donor Ligands. Table 2 summarizes some of the data reported on zirconates, hafnates, and related mixed oxide systems, and the physicochemical properties of mixed oxide systems involving Zr02 have been reviewed. The corrosion of zirconium metal by liquid sodium containing dissolved oxygen takes place... 

The pores of friendly nanomaterials could be used to store strong adds, even super acids, in some cases. Likewise, weak bases or strong bases could be stored for use as needed in killing or destroying advanced enemy toxins. In addition, the nanomaterial itself could be produced with acidic sites (metal ions and/or certain proton donors) built into the pore walls and crystal faces. For example, titanium or zirconium ions can serve as acid sites if adjacent to sulfate species. Likewise, the proton forms of some transition-metal oxygen-anion clusters (polyoxometalates or POMs ), like some metal oxides, are effective superacids in commercial processes. Polyoxometalates could be physically held within the pores or could be grafted onto the pore walls or onto the outer nanocrystal faces. Basic sites can also be built into the nanostructure, such as oxide anions near a metal cation vacancy. There are many other possibilities, such as sulfide substitution for oxide anions on the surface of the nanocrystals. 

Reaction of dialkyl H-phosphonates with ZrCl4 yields, depending on the ratio of the reagents, complexes with different coordination numbers at the metal center [421]. These complexes contain chlorine- and phosphonate-type bridges that form a polymeric network. In the course of this reaction, partial dealkylation of the dialkyl H-phosphonates takes place, and results in the formation of Zr-O-P links. On the other hand, the phosphoryl oxygen forms additional donor-acceptor bonds with the zirconium atom. 

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