Silicon-carbon double bond length determination

There have now been four experimental determinations of a silicon-carbon double bond length. The first of these was a gas phase electron diffraction study of 1,1-dimethylsilene (173). This study was the subject of much controversy since the experimentally determined bond length, 1.83 A, was much longer than the one predicted by ab initio calculations (1.69-1.71 A, see below) (159). Since the calculations were carried out at a relatively high level of theory and the effects of electron correlation on determining the Si=C bond length were considered, the validity of the data extracted from the electron diffraction study is in serious doubt. 

The second determination of a silicon-carbon double bond length came from the X-ray crystal structure of l,l-bis(trimethylsilyl)-2-(trimethyl-siloxy)-2-(l-adamantyl)-l-silaethene (1) (122). Again, the experimentally... 

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