MOLECULAR-DYNAMICS OF DL-BIS(INDENYL)DIMETHYLSILANE AND MESO-BIS(INDENYL)DIMETHYLSILANE - REEXAMINATION OF THE MECHANISM OF INTERCONVERSION BY USING SINGLE SELECTIVE INVERSION NMR

In contrast to a previous report, it is found that the interconversion of dl-(indenyl)(2)SiMe(2), 1a, and its meso isomer, 2a, proceeds through sequential [1,5]-suprafacial shifts and that there is only one mechanism operating at a detectable rate below approximate to 150 degrees C. Below 100 degrees C this process is too slow to be detected by NMR line-broadening methods, but it is readily followed by standard kinetic measurements, Above 100 degrees C, the rate of interconversion is conveniently measured by selective inversion NMR methods. The iso-indene intermediate, 3, has been trapped as its double Diels-Alder adduct with TCNE showing that the rearrangement occurs relatively rapidly on the chemical time scale.