Isolation and Characterization, Including by X‐ray Crystallography, of Contact and Solvent‐Separated Ion Pairs of Silenyl Lithium Species

Abstract

Reaction of bromoacylsilane 1 (pink solution) with tBu2 MeSiLi (3.5 equiv) in a 4:1 hexane:THF solvent mixture at -78 °C to room temperature yields the solvent separated ion pair (SSIP) of silenyl lithium E-[(tBuMe2 Si)(tBu2 MeSi)C=Si(SiMetBu2 )](-) [Li⋅4THF](+) 2 a (green-blue solution). Removal of the solvent and addition of benzene converts 2 a into the corresponding contact ion pair (CIP) 2 b (violet-red solution) with two THF molecules bonded to the lithium atom. The 2 a⇌2 b interconversion is reversible upon THF⇌ benzene solvent change. Both 2 a and 2 b were characterized by X-ray crystallography, NMR and UV/Vis spectroscopy, and theoretical calculations. The degree of dissociation of the Si-Li bond has a large effect on the visible spectrum (and thus color) and on the silenylic (29) Si NMR chemical shift, but a small effect on the molecular structure. This is the first report of the X-ray molecular structure of both the SSIP and the CIP of any R2 E=E'RM species (E=C, Si; E'=C, Si; M=metal).

The Reactions of Carbon Monoxide with Silyl and Silenyl Lithium – Synthesis and Isolation of the First Stable Tetra‐Silyl Di‐Ketyl Biradical and 1‐Silaallenolate Lithium

“…Recently, we reported the synthesis of silenyl lithium 4 and the corresponding silenyl radical . Addition of CO (1 atm, room temperature) to a toluene solution of 4 leads to an immediate color change (from pink to violet) and to quantitative (determined by NMR spectroscopy) formation of lithium 1‐silaallenolate 5 [Eq.…”

Isolation of a Relatively Air‐Stable, Bulky Silyl‐Substituted, Neutral Silicon‐Centered Radical

“…Unless otherwise stated, all commercially available chemicals were purchased from abcr or Sigma‐Aldrich and used without further purification. The compounds ( t Bu 2 MeSi) 2 SiBr 2 , t Bu 2 MeSiLi, ( t Bu 3 Si)SiCl 2 H, ( t Bu 2 MeSi) 3 Si · [6] and t Bu 3 SiNa · 2THF were prepared according to literature procedures.…”

Reactions of an Isolable Dialkylsilylene with Aroyl Chlorides. A New Route to Aroylsilanes

“…aroyl chlorides providing rather exceptional aroyl(chloro)silanes that cannot be obtained via conventional methods. Very recently, an acyl(halo)silane was utilized to synthesize an isolable silenyllithium (Equation (3)) [31].…”

“…Very recently, an acyl(halo)silane was utilized to synthesize an isolable silenyllithium (Equation (3)) [31].…”