Kinetic studies on Brook-type isomerization of acylpolysilanes to silenes

First-order rate constants of Brook-type isomerization of acylpolysilanes (Me3Si)(3)SiCOR (R = iso-Pr, tert-Bu, Ad, 2,6-xylyl, and Mes) leading to silenes (Me3Si)(2)Si=C(OSiMe3)R at various temperatures were determined. Their Eyring plots gave kinetic parameters of Delta H double dagger = 26.6-29.4 kcal mol(-1) and Delta S double dagger = -11.5 to - 14.6 cal mol(-1) K-1. The isomerization was accelerated by introducing an electron-donating alkyl substituent on the carbonyl carbon. These results are in accordance with a concerted mechanism involving a four-centered transition state. (c) 2005 Elsevier B.V. All rights reserved.