Hydrogenation zirconium compounds

In rats, the oral LDso of several zirconium compounds ranged from 1.7 to lOg/kg. Animals acutely poisoned by zirconium compounds show progressive depression and decrease in activity until death. Repeated inhalation of zirconium tetrachloride mist by dogs for 2 months at 6 mg zirconium/m caused slight decreases in hemoglobin and in erythrocyte counts, with some increased mortality over that of controls. These effects may have been due to the liberation of hydrogen chloride. Animals exposed to zirconium dioxide dust for... 

Hydroalumination (cj8, 506-507). This zirconium compound can catalyze hydroalumination of alkenes with trialkylalanes containing /5-hydrogens, such as tri-isobutylalane and lri-/-butylalane.5... 

Concomitant with continued olefin insertion into the metal-carbon bond of the titanium-aluminum complex, alkyl exchange and hydrogen-transfer reactions are observed. Whereas the normal reduction mechanism for transition-metal-organic complexes is initiated by release of olefins with formation of hydride followed by hydride transfer (184, 185) to an alkyl group, in the case of some titanium and zirconium compounds a reverse reaction takes place. By the release of ethane, a dimetalloalkane is formed. In a second step, ethylene from the dimetalloalkane is evolved, and two reduced metal atoms remain (119). 

A chiral Ziegler catalyst that effects enantioselective hydrogenation of olefins has been reported . The catalyst is derived from ( —)-[ethylene(4,5,6,7-tetrahydro-l(/ )-indenyl)]zirconium compounds (1) and aluminoxane. 

Other than the binary hydrides 207), which will not be covered in this review, only a few metal-hydrogen-honded compounds of zirconium and hafnium are presently known, the first being the borohydride M(BH4)4. Although its preparation goes back to the work of Hoekstra and Katz 2i0), it is only recently that structural studies have revealed that metal-hydrogen-boron bridges are involved in the structure. The proton NMR spectrum 263, 582) of a benzene solution shows a quartet... 

Relatively few structures of alkoxo zirconium compounds have been reported. Although a dimeric structme [Zr2(/z-OlV)2(OlV)6(l OH)2] had been proposed for the crystalhne zirconium isopropoxide isopropanolate many years ago the edge-shared bi-octahedral structure was not properly determined by X-ray crystallography until 1990. An interesting feature of this structme is the location of the coordinated isopropanol molecules which are each linked by a hydrogen bond to the terminal... 

Lead dioxide Aluminum carbide, hydrogen peroxide, hydrogen sulfide, hydroxylamine, ni-troalkanes, nitrogen compounds, nonmetal halides, peroxoformic acid, phosphorus, phosphorus trichloride, potassium, sulfur, sulfur dioxide, sulfides, tungsten, zirconium... 

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