One-Electron-Mediated Rearrangements of 2,3-Disiladicarbene

Abstract

A disiladicarbene, (Cy-cAAC)2Si2 (2), was synthesized by reduction of Cy-cAAC:SiCl4 adduct with KC8. The dark-colored compound 2 is stable at room temperature for a year under an inert atmosphere. Moreover, it is stable up to 190 °C and also can be characterized by electron ionization mass spectrometry. Theoretical and Raman studies reveal the existence of a Si═Si double bond with a partial double bond between each carbene carbon atom and silicon atom. Cyclic voltammetry suggests that 2 can quasi-reversibly accept an electron to produce a very reactive radical anion, 2(•-), as an intermediate species. Thus, reduction of 2 with potassium metal at room temperature led to the isolation of an isomeric neutral rearranged product and an anionic dimer of a potassium salt via the formation of 2(•-).

A Stable Dimer of SiS2 Arranged between Two Carbene Molecules

“…The reaction of (Me‐cAAC:) 2 Si 2 12 with elemental sulfur in a 1:4 molar ratio yields (Me‐cAAC:) 2 Si 2 S 4 ( 2 ) (Scheme ). The reaction was conducted in toluene at −78 °C, allowed to come to room temperature very slowly, and continued overnight to give a bright yellow‐colored solution of 2 .…”

“…Furthermore, C1 becomes highly electron deficient during the 1 → 2 transformation, due to the inability of the Si1→C1 back donation (Figure 3 a). Nonetheless the electron deficiency at C1 is reduced by the π‐bonding interaction with N1, as evident from the significant shortening of the N1C1 bond length in 2 (1.306 Å) from 1 (1.343 Å) 12. However it is important to note that weak π‐overlap between N1 and C1 does not satisfy the electron deficiency at the C1 center, since π‐bonding electron densities are primarily localized at the N1 atom (74 %, see NBO results in Tables S4 and S5 in the Supporting Information).…”

“…Method 2 : A mixture of 1 12 (100 mg; 0.159 mmol) and sulfur (20.4 mg; 0.637 mmol) was placed into a 100 mL round bottom flask and THF (50 mL) was added at −78 °C. The reaction mixture was warmed to room temperature within 30–45 min and stirred for another 30 min to afford the bright yellow‐colored solution of 2 .…”

Engineering the Donor Selectivity of D‐Fructose‐6‐Phosphate Aldolase for Biocatalytic Asymmetric Cross‐Aldol Additions of Glycolaldehyde

“…The latter show double‐bond character with the silicon atoms 7. With all the above background knowledge, we reasoned that (Me‐cAAC:) 2 Si 2 12 should be a suitable silicon precursor as it contains both two silylene centers and a silicon–silicon double bond. Herein, we report on the synthesis to stabilize the first molecular dimer of SiS 2 at ambient temperature.…”

The Reactivities of Iminoboranes with Carbenes: BN Isosteres of Carbene–Alkyne Adducts

“…The B1-N2 bond of 6 (1.418 (2) ) is within the standard range for B=N bonds, and the B1-C26 distance of 1.588 (2) is considerably shorter than the carbene-boron bond in 2 (1.660 (3) ), indicating a formal conversion of the dative bond (coordinate covalent) to a conventional covalent (electron-sharing) interaction. [16] The literature on five-membered azaboracycloalkanes is sparse, with only a few reported syntheses. [16] The literature on five-membered azaboracycloalkanes is sparse, with only a few reported syntheses.…”