Synthesis and Reactivity of New Pyrazolyl‐Functionalized Potassium Silanides

The pyrazolyl-functionalized oligosilanes Si(SiMe2PzR)4 (2a R = tBu; 2b R = iPr) were prepared by the reaction of 3-R-pyrazole (R = iPr, tBu) with Si(SiMe2Cl)4 in the presence of NEt3. By treatment with tBuOK and 18-crown-6 in THF, 2a, b were converted into the new potassium silanides (PzRMe2Si)3SiK(18-crown-6) (3a R = tBu; 3b R = iPr), respectively. Upon adding W(CO)6 to THF solutions of 3a, b the tungsten complexes [(PzRMe2Si)3SiW(CO)5]K(18-crown-6) (4a R = tBu; 4b R = iPr) were readily formed, whereas upon adding MgBr2 fragmentation occurs leading to the formation of [(PzRMe2Si)2Si-SiMe2]25.