Interaction of π-bonds of the silicon–silicon triple bond with alkali metals: An isolable anion radical upon reduction of a disilyne

The reduction of 1,1,4,4-tetrakis[bis(trimethylsilyl)methyl]-1,4-diisopropyltetrasila-2-yne 1 with an equivalent amount of alkali metal (Li, Na, K, KC8) in THF produced the corresponding disilyne anion radicals 2a–c. Their EPR spectra are independent of the metals used in THF, indicating that the disilyne anion radical species exists as solvent-separated ion pairs in polar solvents. The one-electron reduction also occurred with potassium in toluene to produce the potassium salt of the anion radical 3, which was isolated as extremely air- and moisture-sensitive dark brown crystals. The molecular structure of 3 was established by X-ray crystallography, which showed that the potassium ion is solvated by one toluene molecule. The EPR spectrum of 3 in toluene showed the interaction of the anionic silicon atom with the K+ ion.