Alkalimetalldisupersilylsilanide MSiXR*2 (R*=SitBu3; X=H, Me, Ph, Hal): Synthesen, Charakterisierung, Strukturen, Reaktionen

Alkali metal disupersilylsilanides MSiXR*2 (R*=supersilyl=SitBu3; X=H, Me, Ph, F, Cl, Br) are prepared: (i) by metalation of R*2XSiBr (X=H, Me) with Li, Na or K in heptane, benzene, tetrahydrofuran (THF); (ii) by activated metalation of R*2SiX2 with LiC10H8 in THF at room temperature (X=F) at −100°C (X=Cl) and at −130°C (X=Br); (iii) by transmetalation between R*2XSiBr (X=H, Me) and NaR* in THF; (iv) by insertion of the silylene R*PhSi (from R*PhSiHCl and NaR*) into the NaSi-bond of NaR* in THF. The prepared hydrolysis- and oxidation-labile silanides are colorless to yellow, if donorfree, and yellow to deep-red as C6H6- or THF-adducts (the C6H6-adducts lose the donor in high vacuum, whereas the THF-adducts do not). Due to X-ray structure analyses, the benzene adducts of KSiXR*2 (X=H, Me) exist as monomers in the crystal with two molecules benzene bound to potassium and an exact planar or a flat pyramidal KSiSi2 framework in KSiHR*2 or KSiMeR*2, respectively. There are contacts of K both to Si and H in KSiHR*2, but only to Si and not to Me in KSiMeR*2. Thermolysis of LiSiXR*2 leads at 25°C (X=F), −78°C (X=Cl) or −120°C (X=Br) to the silylene R*2Si as reactive intermediate. The silanides MSiXR*2 (X=H, Me) are strong bases (e.g. deprotonation of C6H5CH3 or SiH2Cl2), good nucleophiles (e.g. formation of R*2XSi–SiF3 or R*2XSi–SiH2Cl with SiF4 or SiH2Cl2), and powerful reduction agents (e.g. conversion of SnCl2 into Sn).