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.