The power of trichlorosilylation: isolable trisilylated allyl anions, allyl radicals, and allenyl anions.

Treatment of hexachloropropene (ClC[double bond, length as m-dash]C(Cl)-CCl) with SiCl and [BuN]Cl (1 : 4 : 1) in CHCl results in a quantitative conversion to the trisilylated, dichlorinated allyl anion salt [BuN][ClC[double bond, length as m-dash]C(SiCl)-C(SiCl)] ([BuN][]). Tetrachloroallene ClC[double bond, length as m-dash]C[double bond, length as m-dash]CCl was identified as the first intermediate of the reaction cascade. In the solid state, [] adopts approximate symmetry with a dihedral angle between the planes running through the olefinic and carbanionic fragments of [] of C[double bond, length as m-dash]C-Si//Si-C-Si = 78.3(1)°. One-electron oxidation of [BuN][] with SbCl furnishes the distillable blue radical ˙. The neutral propene ClC[double bond, length as m-dash]C(SiCl)-C(SiCl)H () was obtained by (i) protonation of [] with HOSOCF (HOTf) or (ii) H-atom transfer to ˙ from 1,4-cyclohexadiene. Quantitative transformation of all three SiCl substituents in to Si(OMe) ( ) or SiMe ( ) substituents was achieved by using MeOH/NMeEt or MeMgBr in CHCl or THF, respectively. Upon addition of 2 equiv. of BuLi, underwent deprotonation with subsequent LiCl elimination, 1,2-SiMe migration and Cl/Li exchange to afford the allenyl lithium compound MeSi(Li)C[double bond, length as m-dash]C[double bond, length as m-dash]C(SiMe) (Li[]), which is an efficient building block for the introduction of Me, SiMe, or SnMe () groups. The trisilylated, monochlorinated allene ClSi(Cl)C[double bond, length as m-dash]C[double bond, length as m-dash]C(SiCl) (), was obtained from [BuN][] through Cl-ion abstraction with AlCl and rearrangement in CHCl (˙ forms as a minor side product, likely because the system AlCl/CHCl can also act as a one-electron oxidant).