Silyl anions or silylenoids?: A DFT study of silyllithium compounds with π-donating substituents

Geometry optimizations at the B3LYP/6-31+G(d) level for a set of X(SiH3)MeSiLi molecules (X=F, OH, NH2, Cl, SH, and PH2) show that the tetrahedral structure prevails in polar solutions; however, it readily isomerizes into a silylenoid with energy barriers of less than 15 kJmol(-1). Inverted structures, which predominate in the gas phase, could not be located in solution. Configuration inversion is unfavorable, with energy barriers between 80 and 220 kJ mol(-1). The alpha elimination into a silylene moiety and the corresponding LiX is only likely to occur in solution, particularly for X=Cl and SH.