Zirconium structure

K.5 Halide-supported octahedral clusters of zirconium structural and bonding questions... 

The caiculational model described here has been de-velopedas a compromise between accuracy and simplicity for calculating the criticality, power distributions, and temperature coefficients in hi d>ly enriched, water moderated critical assenfolies with zirconium structure. The applications of this model are illustrated in the analysis of various experiments described in this and the following paper. 

The preparation and structure determination of ferrocene marked the beginning of metallocene chemistry Metallocenes are organometallic compounds that bear cyclo pentadiemde ligands A large number are known even some m which uranium is the metal Metallocenes are not only stucturally interesting but many of them have useful applications as catalysts for industrial processes Zirconium based metallocenes for example are the most widely used catalysts for Ziegler-Natta polymerization of alkenes We 11 have more to say about them m Section 14 15... 

This "packing" argument may seem an unnecessary complication. But its advantage comes now. Consider cubic zirconia, ZrOj, an engineering ceramic of growing importance. The structure (Fig. 16.1c) looks hard to describe, but it isn t. It is simply an f.c.c. packing of zirconium with the ions in the tetrahedral holes. Since there are two tetrahedral holes for each atom of the f.c.c. structure, the formula works out at ZrOj. 

Mention has already been made in this chapter of metallocene-catalysed polyethylene (see also Chapter 2). Such metallocene catalysts are transition metal compounds, usually zirconium or titanium. Incorporated into a cyclopentadiene-based structure. During the late 1990s several systems were developed where the new catalysts could be employed in existing polymerisation processes for producing LLDPE-type polymers. These include high pressure autoclave and... 

The precise structure of the zirconium catalyst was examined by NMR analysis. When Zr(Ot-Bu)4 (1 equiv), 8b (2 equiv), and NMI (3 equiv.) were combined in benzene-dg at 23 °C, two independent species which were assigned to a new zirconium catalyst and free 8b were observed. Although the signals of free 8b were still observed when Zr(Ot-Bu)4 (1 equiv), 8b (1 equiv), and NMI (3 equiv.) were stirred at 23 °C, only the signals assigned to the new zirconium catalyst were detected when the mixture was stirred at 80 °C for 2.5 h. These results indicated the formation of 9b as the new zirconium catalyst. The structure was also supported by an experiment in which Zr(Ot-Bu)4 (0.2 equiv), 8a (0.2 equiv), NMI (0.6 equiv), and MS 3 A were combined in benzene and the mixture was stirred for 2.5 h at 80 °C (formation of 9a). Imine Id (1 equiv.) and 7a (1.2 equiv.) were then added to the catalyst solution, and the mixture was stirred for 48 h at 23 °C. After the same work-up procedures as described above, the desired piperidine derivative was obtained in >98% yield with 89% ee, values comparable with those... 

Unlike the PEM, the ionic conduction occurs for the oxygen ion instead of the hydrogen ion. SOFCs are made of ceramic materials like zirconium (Z = 40) stabilized by yttrium (Z = 39). High-temperature oxygen conductivity is achieved by creating oxygen vacancies in the lattice structure of the electrolyte material. The halfcell reactions in this case are... 

Yu.E. Gorbunova Investigation of crystal structure of some carbonate containing hydroxocompounds of zirconium and oxyfluoroniobates -Abstract of dissertation, Moscow 1974 (in Russian). 

The metallocene dichloride of zirconium and hafnium 20b and 20c were also prepared and underwent reduction with potassium to give monomeric metallocene monochloride complexes 21b and 21c (Eq. 8) [39b]. The structure of the zirconocene complex 21 b in the crystal showed a conformation which suggests a less steric strain as compared to 21a due to zirconium s larger atomic size. As a consequence of the coordinative unsaturation an unusually short Zr —Cl bond length was found. 

The structural chemistry of zirconium compounds. T. E. MacDermott, Coord. Chem. Rev., 1973. 

Structural aspects of zirconium chemistry. A. Clearfield, Rev. Pure Appl. Chem., 1964, 14, 91-108 (94). 

Zirconium, cblorotris(acctylacetonc)-stercochemistry, 1, 82 Zirconium, octafluoro-structure, 1, 84... 

Zirconium, tetrakis(acetylacetonate)-stereochemistry, 1, 32, 94 Zi rconium, tris(phenylenedithio)-structure, 1, 63 Zirconium alkoxides oligomeric structure, 2,346 Zirconium chloride... 

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