Trihydridozincate

The apparatus used to carry out this reaction is the same as that shown in Fig. 2. The 50-mL round-bottomed flask G, containing a magnetic stirring 

J Centrifuging is also satisfactory for separating the solid material from the clear solution. 

The resulting solid is then dried under vacuum at room temperature overnight. This drying procedure removes essentially all of the diethyl ether. The apparatus used for drying is the same as that shown in Fig. 2, except that a piece of glass wool H is inserted below stopcock C in order to prevent the solids from being sucked up into the vacuum system. The yield of lithium trihydridozincate(l —) is 0.365 g (0.005 mol), which is quantitative. Anal. Calcd. for Li[ZnH3] Li, 9.2 Zn, 86.9 H, 4.0. Found Li, 9.2 Zn, 86.5 H, 4.30. The molar ratio of Li/Zn/H in the white solid is 1.00 1.00 3.21. Aluminum is absent. 

Lithium trihydridozincate( 1 —) is a white, granular solid which slowly turns black on standing at room temperature. If it is stored at Dry Ice temperature, it remains white for an indefinite period of time. It is not soluble to any extent in ethereal solvents, and it is very sensitive to air and moisture. It is best identified by its x-ray powder diffraction (nickel-filtered CuKa) pattern. The predominant interplanar spacing and the corresponding relative intensities (estimated visually) are d = 6.25 A (m) 4.45 A (vs) 4.30 A (m)  

It decomposes under vacuum at 97° to give lithium tetrahydrido-zincate(2-) and zinc metal. 

---

The reaction of methyllithium with dimethylzinc in 1 1 and 2 1 molar ratios in diethyl ether solution produces lithium tri- and tetramethyl-zincates.1 Two equivalents of lithium trimethylzincate( 1 -) react with three equivalents of lithium tetrahydridoaluminate(l -), and one equivalent of lithium tetramethylzincate(2 —) reacts with two equivalents of lithium tetra-hydridoaluminate(l —) to give lithium trihydridozincate( 1 -) and lithium tetrahydridozincate(2 —), respectively, in quantitative yields. Both reactions proceed in diethyl ether at room temperature and are complete within 5 min. The compounds are air-sensitive and therefore must be prepared in an airfree atmosphere (nitrogen or argon). They may be used as reducing agents in organic syntheses. 

The reaction described here of methylzinc iodide with sodium hydride, to produce Na[Zn2(CH3)2H3], may be pictured as a combination of the two reaction types named above. Unlike many hydride preparations, the synthesis of sodium trihydridodimethyldizincate(l —) is easily performed using ordinary Schlenk-type bench-top techniques and commercially available starting materials.4 Sodium trihydridozincate( 1 —) is easily prepared by exposing Na[Zn2(CH3)2H3]-xTHF to high vacuum.4... 

Na[Zn2(CH3)2H3] -xTHF is sensitive to air, moisture, and heat and must be stored in a closed container at - 78°. At room temperature, the compound slowly decomposes, changing from a white powder to first yellow, then gray, aggregates. It loses dimethylzinc and THF readily at room temperature, eventually becoming sodium trihydridozincate(l -). 

Sodium trihydridozincate( 1 —) is air- and moisture-sensitive, but can be stored at room temperature under vacuum or an inert atmosphere. Because of this stability Na[ZnH3] is a promising compound for the preparation of zinc hydride derivatives. The infrared spectrum and x-ray powder pattern of Na[ZnH3] are reported,4 and an alternate preparation has been mentioned.8... 

---