Stable Silenolates and Brook-Type Silenes with Exocyclic Structures

Abstract

The first silenolates with exocyclic structures [(Me₃Si)₂Si(Si₂Me₄)₂SiC(R)O]^-K⁺ (<b>2a</b>: R = 1-adamantyl; <b>2b</b>: mesityl; <b>2c</b>: <i>o</i>-tolyl) were synthesized by the reaction of the corresponding acylcyclohexasilanes <b>1a</b>-<b>c</b> with KO<i>t</i>Bu. NMR spectroscopy and single-crystal X-ray diffraction analysis suggest that the aryl-substituted silenolates <b>2b</b>,<b>c</b> exhibit increased character of functionalized silenes as compared to the alkyl-substituted derivative <b>2a</b> due to the different coordination of the K⁺ counterion to the SiC(R)O moiety. <b>2b</b>,<b>c</b>, thus, reacted with ClSi<i>i</i>Pr₃ to give the exocyclic silenes (Me₃Si)₂Si(Si₂Me₄)₂Si=C(OSi<i>i</i>Pr₃)R (<b>3b</b>: R = Mes; <b>3c</b>: <i>o</i>-Tol), while <b>2a</b> afforded the Si-silylated acylcyclohexasilane <b>1d</b>. The thermally remarkably stable compound <b>3b</b>, which is the first isolated silene with the sp² silicon atom incorporated into a cyclopolysilane framework, could be fully characterized structurally and spectroscopically.