Alkalimetalldisupersilylsilanide MSiXR2* (R* = SitBu(3); X = H, Me, Ph, Hal): Synthesen, charakterisierung, strukturen, reaktionen

Alkali metal disupersilylsilanides MSiXR2* (R* = supersilyl = SitBu(3); X = H, Me, Ph, F, Cl, Pr) are prepared: (i) by metalation of (R2XSiBr)-X-* (X = H, Me) with Li, Na or K in heptane, benzene, tetrahydrofuran (THF); (ii) by activated metalation of R-2*SiX2 with LIC10H8 in THF at room temperature (X = F) at - 100 degreesC (X = Cl) and at - 130 degreesC (X = Br); (iii) b y transmetalation between (R2XSiBr)-X-* (X = H, Me) and NaR* in THF; (iv) b y 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 silanide s 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 T HF-adducts do not). Due to X-ray structure analyses, the benzene adducts of KSiXR2* (X = H, Me) exist as monomers in the crystal with two molecules be nzene bound to potassium and an exact planar or a flat pyramidal KSiSi2 fra mework in KSiHR2* or KSiMeR2* respectively. There are contacts of K both to Si and H in KSiHR2*, but only to Si and not to Me in KSiMaR(2)*. Thermolys is of LiSiXR2* leads at 25 degreesC (X= F), - 78 degreesC (X =Cl) or -120 d egreesC (X = Br) to the silylene R-2*Si as reactive intermediate. The silan ides MSiXR2* (X = H, Me) are strong bases (e.g. deprotonation of C6H5CH3 or SiH2Cl2), good nucleophiles (e.g, formation of R-2*XSi-SiF3 or R-2*XSi-SiH 2Cl with SIF4 or SiH2Cl2), and powerful reduction agents (e.g. conversion o f SnCl2 into Sn). (C) 2001 Elsevier Science B.V. All rights reserved.