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(trimethylsilyl)methyl]-1,4-diisopropyl-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 alkenes. 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)degrees.