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). Both 3 and 5 were characterized by X-ray crystallography and biradical 3 also by EPR spectroscopy. Silaallenolate 5 reacts with Me SiCl to produce siloxy substituted 1-silaallene (tBu MeSi)(tBuMe Si)C=C=Si(SiMetBu )OSiMe . The reaction of 4 with CO provides a new route to 1-silaallenes. The mechanisms of the reactions of tBuMe SiLi and of 4 with CO were studied by DFT calculations.