A stable compound containing a silicon-silicon triple bond

The reaction of 2,2,3,3-tetrabromo- 1,1,4,4-tetrakis[bis(trimethylsilyl) methyl]-1,4-diisopropyltetrasilane with four equivalents of potassium graphite (KC₈) in tetrahydrofuran produces 1,1,4,4-tetrakis[bis(trimethylsil) methyl]-1,4-diiso-propyl-2-tetrasilyne, a stable compound with a silicon-silicon triple bond, which can be isolated as emerald green crystals stable up to 100°C in the absence of air. The Si≡Si triple-bond length (and its estimated standard deviation) is 2.0622(9) angstroms, which shows half the magnitude of the bond shortening of alkynes compared with that of a[kenes. Unlike alkynes, the substituents at the Si≡Si group are not arranged in a linear fashion, but are trans-bent with a bond angle of 137.44(4)°.