An Isolable Disilyne Anion Radical and a New Route to the Disilenide Ion upon Reduction of a Disilyne

The reaction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with tBuLi produced disilenyllithium derivative 2, the product of the formal addition of LiH across the Si⋮Si triple bond through a single electron transfer reaction. The solvent-separated ion pair of the disilenide 3 was characterized by X-ray crystallography. The bulky SiiPr[CH(SiMe3)2]2 groups are arranged in the trans fashion with a silicon−silicon double bond length of 2.2034(9) Å. The reaction of 1 with an equivalent amount of potassium graphite (KC8) in THF produced the disilyne anion radical 4, which was isolated in the form of its potassium salt as extremely air- and moisture-sensitive dark brown crystals. The molecular structure of 4 was established by X-ray crystallography, which showed a trans-bent structure (av 113.4°) with the central Si−Si bond length of 2.1728(14) Å. An electron spin resonance (ESR) study indicates delocalization of the unpaired electron between the two central silicon atoms of 4.