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 tBu₂MeSiLi and (E)‐(tBu₂MeSi)(tBuMe₂Si)C=Si(SiMetBu₂)Li?2 THF ( 4 ) were studied both experimentally and computationally. Reaction of tBu₂MeSiLi with CO in hexane yields the first stable tetra‐silyl di‐ketyl biradical (tBu₂MeSi)₂COLi]^.₂ ( 3 ). Reaction of 4 with CO yields selectively and quantitatively the first reported 1‐silaallenolate, (tBu₂MeSi)(tBuMe₂Si)C=C=Si(SiMetBu₂)OLi?THF ( 5 ). Both 3 and 5 were characterized by X‐ray crystallography and biradical 3 also by EPR spectroscopy. Silaallenolate 5 reacts with Me₃SiCl to produce siloxy substituted 1‐silaallene (tBu₂MeSi)(tBuMe₂Si)C=C=Si(SiMetBu₂)OSiMe₃. The reaction of 4 with CO provides a new route to 1‐silaallenes. The mechanisms of the reactions of tBuMe₂SiLi and of 4 with CO were studied by DFT calculations.