Stable Silenolates and Brook-Type Silenes with Exocyclic
Structures
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Abstract
The
first silenolates with exocyclic structures [(Me<sub>3</sub>Si)<sub>2</sub>Si(Si<sub>2</sub>Me<sub>4</sub>)<sub>2</sub>SiC(R)O]<sup>−</sup>K<sup>+</sup> (<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<sup>+</sup> counterion to the SiC(R)O moiety. <b>2b</b>,<b>c</b>, thus, reacted with ClSi<i>i</i>Pr<sub>3</sub> to give the exocyclic silenes (Me<sub>3</sub>Si)<sub>2</sub>Si(Si<sub>2</sub>Me<sub>4</sub>)<sub>2</sub>SiC(OSi<i>i</i>Pr<sub>3</sub>)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 sp<sup>2</sup> silicon atom incorporated into a cyclopolysilane
framework, could be fully characterized structurally and spectroscopically