Structure of a Cumulene Bearing Bulky Substituents. X-Ray Study of 1,1,4,4-Tetrakis(trimethylsilyl)butatriene

The structure of cumulene bearing bulky substituents, 1,1,4,4-tetrakis(trimethylsilyl)butatriene, has been determined by an X-ray diffraction method. The molecule is centrosymmetric, and the variation in carbon–carbon double bonds has been observed. The distance of the central C=C bond is 1.276(8) Å, whereas that of the terminal C=C bond is 1.319(6) Å. These bond lengths are very similar to the unsubstituted butatrienes and the influence of bulky trimethylsilyl groups is not recognized in this context. Some distortions have been observed in the bond angles concerning the trimethylsilyl groups; the overcrowded environment of the central C=C bond seems to make this less reactive.