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 tBu2 MeSiLi and (E)-(tBu2 MeSi)(tBuMe2 Si)C=Si(SiMetBu2 )Li⋅2 THF (4) were studied both experimentally and computationally. Reaction of tBu2 MeSiLi with CO in hexane yields the first stable tetra-silyl di-ketyl biradical [(tBu2 MeSi)2 COLi]. 2 (3). Reaction of 4 with CO yields selectively and quantitatively the first reported 1-silaallenolate, (tBu2 MeSi)(tBuMe2 Si)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 Me3 SiCl to produce siloxy substituted 1-silaallene (tBu2 MeSi)(tBuMe2 Si)C=C=Si(SiMetBu2 )OSiMe3 . The reaction of 4 with CO provides a new route to 1-silaallenes. The mechanisms of the reactions of tBuMe2 SiLi and of 4 with CO were studied by DFT calculations.

Radical polymerization of the silene (Me3Si)2Si=CR2 by hydrogen transfer from a trimethylsilyl group.

The silene (Me(3)Si)(2)Si=Ad is polymerized to produce a polycarbosilane with an unusual Si-Si-C repeating backbone, rather than the Si-C or Si-Si-C-C units expected for olefinic radical polymerization. The polymer structure and the polymerization mechanism (see scheme) were studied by GPC, EPR, and NMR spectroscopy and by trapping experiments.