POLYLITHIUM COMPOUNDS .3. POLYLITHIUM COMPOUNDS FROM PROPYNE AND 1-BUTYNE, AND THEIR POLYSILICON DERIVATIVES

Propyne reacts with n-butyllithium in hexane to form C3Li4, liberating 4 equiv of n-butane. With trimethylchlorosilane in tetrahydrofuran, C3Li4 gives tetrakis(trimethylsilyl)allene (1) in 70% yield along with some l,3,3-tris(trimethylsilyl)propyne (2) and other products. Partial thermal isomerization of 2 to its allenic isomer, l,3,3-tris(trimethylsilyl)propadiene (3), can be effected. 1-Butyne forms a trilithio derivative with 3 equiv of t-butyllithium; with trimethylchlorosilane, this produces a mixture of l,3,3-tris(trimethylsilyl)-1-butyne (6) and 1,1,3-tris(trimethylsilyl)-l,2-butadiene (7). 6 and 7 are also obtained by lithiation of either 2 or 3 followed by treatment with methyl iodide. The structures of the polylithium compounds in hexane solution have been studied by infrared spectroscopy. They appear to have allenic structures, e.g., Li2C=C=CLi2. © 1969, American Chemical Society. All rights reserved.