Synthesis of Silenyllithiums Li(R′3Si)SiC(SiR3)(1-Ad) via Transient Silyne–Silylidene Intermediates

The first two lithium silenides, Li­(tBu2MeSi)­SiC­(SiMetBu2)­(1-Ad) (1) and Li­(tBuMe2Si)­SiC­(SiMetBu2)­(1-Ad) (2) were prepared by THF addition to the corresponding lithium-silenolates, [(tBu2MeSi)2SiC­(OLi)­(1-Ad)]·(R3SiLi) (3a: R3SitBu2MeSi, 3b: R3SitBuMe2Si). 1 and 2 were crystallized, and their structures were determined by X-ray crystallography. This process requires the presence of both coaggregated silyllithium (R3SiLi) (3a and 3b) and THF. Based on reaction products and DFT calculations, it is suggested that elimination of tBu2MeSiOLi from 3a (or 3b) produces first the corresponding silyne intermediate which rearranges to the corresponding silylidene, which is then trapped by R3SiLi giving 1 (or 2).