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.

Reactions of carbon monoxide (CO) with tBu MeSiLi and (E)-(tBu MeSi)(tBuMe Si)C=Si(SiMetBu )Li⋅2 THF (4) were studied both experimentally and computationally. Reaction of tBu MeSiLi with CO in hexane yields the first stable tetra-silyl di-ketyl biradical [(tBu MeSi) COLi] (3). Reaction of 4 with CO yields selectively and quantitatively the first reported 1-silaallenolate, (tBu MeSi)(tBuMe Si)C=C=Si(SiMetBu )OLi⋅THF (5).

Generation and EPR Spectroscopy of the First Silenyl Radicals, R C=Si -R: Experiment and Theory.

The first two persistent silenyl radicals (R C=Si -R), with a half-life (t ) of about 30 min, were generated and characterized by electron paramagnetic resonance (EPR) spectroscopy. The large hyperfine coupling constants (hfccs) (a( Si )=137.5-148.

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

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.