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 t Bu 2 MeSiLi and ( E )‐( t Bu 2 MeSi)( t BuMe 2 Si)C=Si(SiMe t Bu 2 )Li⋅2 THF ( 4 ) were studied both experimentally and computationally. Reaction of t Bu 2 MeSiLi with CO in hexane yields the first stable tetra‐silyl di‐ketyl biradical [( t Bu 2 MeSi) 2 COLi] . 2 ( 3 ). Reaction of 4 with CO yields selectively and quantitatively the first reported 1‐silaallenolate, ( t Bu 2 MeSi)( t BuMe 2 Si)C=C=Si(SiMe t Bu 2 )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 3 SiCl to produce siloxy substituted 1‐silaallene ( t Bu 2 MeSi)( t BuMe 2 Si)C=C=Si(SiMe t Bu 2 )OSiMe 3 . The reaction of 4 with CO provides a new route to 1‐silaallenes. The mechanisms of the reactions of t BuMe 2 SiLi and of 4 with CO were studied by DFT calculations.