The molecule dynamics and cycloaddition chemistry of tris(1-indenyl)allylsilane Part 1 - Generation of the first crystallographically characterized tris(benzonorbornyl)silane

The preparation, characterization and molecular dynamics of tris(l-indenyl) allylsilane, 5, are presented. Data obtained from single selective inversio n and H-1-H-1 EXSY NMR experiments demonstrate that 5 is indeed fluxional ( Delta G(not equal) similar to 25 kcal mol(-1)). Moreover, a solution of 5 s tirred with three equivalents of tetracyanoethylene yields tris(5,6-benzo-2 ,2,3,3-tetracyanobicyclo[2.2.1]heptan-7-yl)allylsilane, 7, an observation t hat is consistent with the sequential generation and trapping of isoindene intermediates in a [1,5]-silatropic shift mechanism. The triple cycloadduct , 7, represents what is believed to be the first crystallographically chara cterized tris(benzonorbornyl)silane.