The use of sodium hydride as a reducing agent in nitrogen-containing solvents I. The reduction of chlorosilanes in Hexaalkylphosphoric triamides and tetraalkylureas

Abstract

A variety of chlorosilanes were reduced to the corresponding silicon hydrides with sodium hydride in hexamethylphosphoric triamide (HMPT), tetramethylurea (TMU) and related solvents. In HMPT and TMU, the reductions proceeded rapidly at room temperature under nitrogen in good yield. No side reactions were noted for the simple alkyl-and arylchlorosilanes except for some inhibition periods if air was present and a little reduction of TMU to tetramethylmethylenediamine. Allyldimethyl-and vinyldimethylchlorosilanes were reduced normally in TMU, but in HMPT olefin isomerization and vinyl polymerization occured. These side reactions were shown to be due to the presence of sodium in the sodium hydride. The sodium may be leached out with HMPT, and the resulting sodium hydride gave improved yields for the reduction of tetramethyldichlorodisiloxane. Other solvents either gave no chlorosilane reduction or were too reactive in side reactions. These included dioxane, tetramethylethylenediamine, dimethylformamide and dimethylacetamide. Pyridine, however, appeared to be a suitable solvent although the rate of chlorosilane reduction was slow compared to HMPT and TMU.