Group 14 elements alkene analogs

As mentioned above, the chemistry of distannenes, >Sn=Sn<, the tin analogs of ethylene, has the longest history among all heavy alkene analogs of the type > E=E < (E, E are heavier group 14 elements). The first stable compound with an Sn=Sn double bond, 1, was reported by Lappert et al. in 1973. Since then, distannenes 6-17 have been synthesized and characterized, and some of their parameters... 

Only a few years ago, students were taught that silicon and germanium formed no multiple bonds to anything. Textbooks emphasized that these elements, as well as other, heavier main group elements, were simply not able to self-link through double bonds to yield stable compounds analogous to those of alkenes, the important family of unsaturated hydrocarbons with C=C bonds. Now the facile synthesis of multiple bonds in heavier main group elements is routinely reported, and doubtless the detailed thermochemistry will keep apace. 

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