Stable Silenolates and Brook-Type Silenes with Exocyclic Structures

[Image: see text] The first silenolates with exocyclic structures [(Me(3)Si)(2)Si(Si(2)Me(4))(2)SiC(R)O](−)K(+) (2a: R = 1-adamantyl; 2b: mesityl; 2c: o-tolyl) were synthesized by the reaction of the corresponding acylcyclohexasilanes 1a–c with KOtBu. NMR spectroscopy and single-crystal X-ray diffraction analysis suggest that the aryl-substituted silenolates 2b,c exhibit increased character of functionalized silenes as compared to the alkyl-substituted derivative 2a due to the different coordination of the K(+) counterion to the SiC(R)O moiety. 2b,c, thus, reacted with ClSiiPr(3) to give the exocyclic silenes (Me(3)Si)(2)Si(Si(2)Me(4))(2)Si=C(OSiiPr(3))R (3b: R = Mes; 3c: o-Tol), while 2a afforded the Si-silylated acylcyclohexasilane 1d. The thermally remarkably stable compound 3b, which is the first isolated silene with the sp(2) silicon atom incorporated into a cyclopolysilane framework, could be fully characterized structurally and spectroscopically.