STRUCTURES AND MOLECULAR-PROPERTIES OF ST ERICALLY OVERCROWDED MOLECULES .36. (E)-1,1,1,4,4,4-HEXAKIS(TRIMETHYLSILYL)-2-BUTENE [(H3C)3SI]3C-HC=CH-C[SI(CH3)3]3 AND BIS[TRIS(TRIMETHYLSILYL)SILYL]ETHIN [(H3C)3SI]3SI-C-EQUIVALENT-TO-C-SI[SI(CH3)3]3
H. Bock et al., STRUCTURES AND MOLECULAR-PROPERTIES OF ST ERICALLY OVERCROWDED MOLECULES .36. (E)-1,1,1,4,4,4-HEXAKIS(TRIMETHYLSILYL)-2-BUTENE [(H3C)3SI]3C-HC=CH-C[SI(CH3)3]3 AND BIS[TRIS(TRIMETHYLSILYL)SILYL]ETHIN [(H3C)3SI]3SI-C-EQUIVALENT-TO-C-SI[SI(CH3)3]3, Chemische Berichte, 126(10), 1993, pp. 2227-2235
The single crystal structure of an ethylene derivative, in which the t
wo substituent half-shells are separated by a C=C spacer of about 403
pm length, shows C...C distances of 404, 415 as well as 421 pm between
non-adjacent and of 352 pm between adjacent methyl groups, i.e. close
to or within their van der Waals radii sum of 400 pm. The PE-spectros
copically determined vertical first ionization energies of both compou
nds, 7.78 eV and 7.71 eV, are each the lowest ones reported so far for
disubstituted ethylenes and acetylenes. Despite of irreversible cyclo
voltammetric oxidation potentials, the radical cation of the six-fold
R3Si-substituted 2-butene can be generated by SbCl5/H2CCl2 and charact
erized below 230 K by its ESR spectrum.