Kinetic study on thermal syn-anti isomerization of dodecaisopropyltricyclo[4.2.0.02,5]octasilane
摘要:
When heated at 493 K, syn-dodecaisopropyltricyclo[4.2.0.0(2,5)]octasilane (syn-1) isomerizes to anti-dodecaisopropyltricyclo[4.2.0.0(2,5)]octasilane (anti-1); isomerization of anti-1 to syn-1 does not occur at 493 K. Thermodynamic parameters were determined for the one-way isomerization of syn-1 to anti-1: E(a) = 42.3 kcal mol(-1), log A = 15.1 s(-1), Delta H double dagger = 41.4 kcal mol(-1), Delta S double dagger = 7.6 X 10(-3) kcal mol(-1) K-1 and Delta G(493K)double dagger = 37.6 kcal mol(-1). The activation energy is considerably larger than that for the analogous thermal isomerization of syn-bicyclo[4.2.0.0(2,5)]octane (syn-2) to anti-tricyclo[4.2.0.0(2,5)]octane (anti-2), indicating that the bond dissociation energy of the bridgehead Si-Si bond of syn-1 is larger than that of the bridgehead C-C bond of syn-2.
Ring-Opening Reactions of<i>anti</i>-Dodecaisopropyltricyclo[4.2.0.0<sup>2,5</sup>]octasilane. Formation of Novel Bicyclo[3.3.0]octasilane and Bicyclo[4.2.0]octasilane Systems
The reaction of anti-dodecaisopropyltricyclo[4.2.0.02,5]octasilane (1) with PdCl2(PhCN)2 gave bicyclo[3.3.0]octasilane(trans-2) and bicyclo[4.2.0]octasilane (trans-3). In the reaction of 1 with PCl...