Zinc dihydride

The solution of aluminum trihydride used in this synthesis is prepared by the reaction of 100% sulfuric acid with lithium tetrahydridoaluminate(l —) in dry tetrahydrofuran.3 Under nitrogen flow, a stoichiometric amount of the sulfuric acid is added dropwise by syringe at 0° to a solution of lithium tetrahydridoaluminate(l —) in dry tetrahydrofuran. The apparatus used is just like that shown in Fig. 2, except that an ice bath is used to cool the reaction flask and thus prevent ether cleavage. As the sulfuric acid is added to the lithium tetrahydridoaluminate(l —), a precipitate of lithium sulfate forms and hydrogen is evolved. For this reason, the reaction must be carried out in a hood. After all the sulfuric acid has been added, the resulting slurry is stirred for 2 hr, then filtered in a glove box.4,5 The filtrate, a clear solution of aluminum trihydride in tetrahydrofuran, is stored in the refrigerator at -20° until it is needed. 

The solution of dimethylzinc in dry tetrahydrofuran is prepared by the method of Noller.6 The methyl iodide is dried over anhydrous magnesium sulfate and distilled prior to use. The Zn/Cu couple was flamed and dried under vacuum overnight prior to use. The reaction of the Zn/Cu couple with methyl iodide was allowed to proceed overnight. The dimethylzinc was distilled from the reaction mixture at atmospheric pressure under nitrogen. 

The apparatus used to carry out the above reaction is shown in Fig. 2. The 50-mL round-bottomed flask G, containing a magnetic stirring bar and a 

The magnetic stirrer is turned on, and by means of syringes, previously dried and flushed with nitrogen, 6.1 mL of a 0.820M solution of dimethyl-zinc (0.005 mol) in dry tetrahydrofuran is added to the flask followed by 

The remaining precipitate of zinc dihydride is washed with three 25-mL portions of freshly distilled tetrahydrofuran. This is accomplished by setting stopcock / at position B with valve L open. The 25-mL portions of tetrahydrofuran are added through stopcock / the mixture is stirred for 5 min, with stopcock / in position C the zinc dihydride is allowed to settle and the supernatant liquid is removed via syringe by returning stopcock / to position B. The wash solution is destroyed in the same way as that described earlier for the more concentrated solution of dimethylaluminum hydride. 

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The washed precipitate is dried under vacuum at room temperature by returning stopcock / to position E. The vacuum must be applied slowly so that the zinc dihydride is not sucked up into the vacuum system (this is the reason for the glass-wool plug). The zinc dihydride is left under vacuum overnight for drying. The yield of zinc dihydride is 0.330 g (0.00493 mol), which is quantitative. Anal. Calcd. for ZnH2 Zn, 97.03 H, 2.97. Found Zn, 75.67 H, 2.35 THF, 22.08. The molar ratio of Zn/H/THF is... 

Zinc dihydride is a white, granular solid which decomposes at 90° to zinc metal and hydrogen. The THF of solvation is liberated gradually during the... 

Tetraphosphorus decasulfide, 4878 Thorium dihydride, 4489 Titanium, 4919 Titanium carbide, 0561 Titanium dihydride, 4490 Zinc stearate, 3897 Zirconium, 4928... 

Tetraphosphorus decasulfide, 4872 Thorium dihydride, 4483 Titanium, 4913 Titanium carbide, 0558 Titanium dihydride, 4484 Zinc stearate, 3891 Zirconium, 4922... 

Magnesium—nickel hydride, 4458 Plutonium(III) hydride, 4504 Poly(germanium dihydride), 4409 Poly(germanium monohydride), 4407 Potassium hydride, 4421 Rubidium hydride, 4444 Sodium hydride, 4438 f Stibine, 4505 Thorium dihydride, 4483 Thorium hydride, 4535 Titanium dihydride, 4484 Titanium—zirconium hydride, 4485 Trigermane, 4415 Uranium(III) hydride, 4506 Uranium(IV) hydride, 4536 Zinc hydride, 4486 Zirconium hydride , 4487 See COMPLEX HYDRIDES, PYROPHORIC MATERIALS See entry LANTHANIDE—TRANSITION METAL ALLOY HYDRIDES... 

Liquid uronititic iiiniiic i. for example aniline or lsiH iiinolinc, ofcen become badly discolored on storage us Ihc rcsull of air oxidation. Distillation from a pinch of zinc dust affords tdmost water-clear liquid. Kuhn and Winterstein" found that the violet carotinoid ester-acid bixin can be reduced very smoothly to its yellow dihydride with zinc dust in pyridine containing a small amount of acetic acid. Thus on addition of... 

Two novel complex hydrides are likely to find applications in steroid chemistry lithium perhydro-9b-boraphen yl hydride affords unusually high proportions of axial alcohols in model compounds sodium bis(methoxyethoxy)aluminium dihydride, Na (MeOCH2CH20)JAlH2, a very safe and convenient substitute for lithium aluminium hydride, readily reduces not only ketones but also acids, nitro-compounds, oximes, amides, lactones, etc. An improved procedure for Clemmensen reduction of steroid ketones involves saturating an ethereal solution with hydrogen chloride while stirring with zinc. 5a-Cholestane was obtained from the 3-one in 89% yield. ... 

Gansauer and coworkers have developed a tandem catalytic approach to reductive epoxide opening that employs H transfer from a dihydride complex (Scheme 1.2) [32, 33]. The carbonepoxide opening with Cp2TiCl abstracts H from the H2 adduct of Wilkinson s catalyst Manganese or zinc metal regenerates the active Ti" species and makes the reaction catalytic. 

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