Synthesis and Functionalization of a 1,4-Bis(trimethylsilyl)tetrasila-1,3-diene through the Selective Cleavage of Si(sp²)–Si(sp³) Bonds under Mild Reaction Conditions

Abstract

Although the oxidative coupling of disilenides, i.e., the disilicon analogues of vinyl anions, represents a promising route to extend the conjugation between SiSi double bonds, previously reported synthetic routes to disilenides involve strongly reducing conditions. Herein, we report a novel synthetic route to disilenides from stable disilenes via the selective cleavage of Si­(sp2)–Si­(sp3) bonds under milder reaction conditions. Using this method, a 1,4-bis­(trimethylsilyl)­tetrasila-1,3-diene (5) was synthesized from the corresponding silyl-substituted disilene. Moreover, Et3Si-substituted tetrasila-1,3-diene 7 was synthesized via tetrasila-1,3-dien-1-ide 6, which is the first example of a functionalized tetrasila-1,3-diene.

Synthesis and Functionalization of a 1,2-Bis(trimethylsilyl)-1,2-disilacyclohexene That Can Serve as a Unit of cis-1,2-Dialkyldisilene

“…These results are consistent with a recent theoretical study that two Si=Si in tetrasila-1,3-diene can interact each other even at the dihedral angle of 90 • due to the intrinsic non-planar geometry around the Si=Si double bond [16]. The longest wavelength absorption bands found in 8 (~500 nm) are hypsochromically-shifted compared those of the reported aryl-substituted tetrasila-1,3-dienes D (518 nm) [25], E (531 nm) [12] probably due to the absence of aryl-substituents, but close to that of structurally similar tetrasila-1,3-diene F (510 nm) [26] (Figure 1).…”

“…The 29 Si NMR spectra exhibited two signals due to the unsaturated silicon nuclei at 146.9 ppm (=SiSiMe3) and 219.3 ppm (=Si − ). Similar large differences between the chemical shifts of the unsaturated silicon nuclei have been found in those of structurally related disilenides (Me3Si)TipSi=SiTip[K(thf)n] (101.4 (=Si(SiMe3)Tip), 186.6 (=Si − ) in THF-d8; Tip = 2,4,6-triisopropylphenyl) [16] and reported disilenides [27]. …”

“…Disilene 1 can be effectively converted to the corresponding disilenide through a selective cleavage of the Si(sp 2 )-Si(sp 3 ) bond (Scheme 2) [16]. When 1 was treated with one equivalent of tBuOK in THF, the color of solution gradually turned from yellow to orange.…”

“…Very recently, we found a novel route to a disilenide from a stable disilene under milder conditions [16]. In this route, the disilenide was generated from the reaction of a trimethylsilyl-substituted disilene and potassium t-butoxide [17] via selective cleavage of the Si(sp 2 )-Si(sp 3 ) bond on the Si=Si double bond.…”

A Mixed Heavier Si=Ge Analogue of a Vinyl Anion

“…X‐ray crystallography, UV/Vis and DFT calculations revealed a significant degree of π‐conjugation between the N=C and Si=Ge double bonds in potassium silagermenide. The silagermenide could therefore also be regarded as heavier analogue of a butadienide anion, an example of which was recently documented, [25] but not structurally characterized due to decomposition above −50 °C. Reactions of the silagermenide 3 ⋅K(THF) with a variety of other electrophiles and small molecules are currently underway.…”