Trihydridozincate l — and Lithium Tetrahydridozincate

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 diethyl ether used herein is purified and dried prior to use by atmospheric-pressure distillation over lithium tetrahydridoaluminate( 1 — ) under a nitrogen atmosphere. The lithium tetrahydridoaluminate(l —) should be added to the diethyl ether in a nitrogen-filled dry box, and the distillation should not be carried out past the point where the distillation flask is one-quarter full. 

The methyllithium is obtained as a 5% solution in diethyl ether. It is stored in a refrigerator at —20° until ready for use. The solution is standardized by measuring the amount of methane gas evolved when a sample is added to methanol. The gas analyses are carried out by hydrolyzing the sample on a standard vacuum line equipped with a Toepler pump.3 

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