Syntheses, structures, and reactivity of poly(pyrazolyl)silanes, -disilanes, and the ambidentate kappa(1)Si/kappa(3)N-coordinating tris(3,5-dimethylpyrazolyl)silanide ligand [Si(3,5-Me2pz)3]- ((Me)Tpsd).

The reaction conditions for the synthesis [Si(2)((Me)pz)(6)] (1) and [Si((Me)pz)(4)] (4) have been investigated in detail in order to obtain suitable precursor compounds for the synthesis of the hitherto unknown Janus-head ligand tris(3,5-dimethylpyrazolyl)silanide ([Si((Me)pz)(3)](-), (Me)Tpsd). Within the monomeric lithium salt [Li(thf)((Me)Tpsd)] (5), the ambidentate silanide ligand is bound in a kappa(3)N-fashion to the Li cation, featuring an uncoordinated, anionic silicon bridgehead. Treatment of the silanide with various electrophiles such as Me(3)SiCl, Me(3)SnCl and Ph(3)SnCl gave in each case the expected salt metathesis reaction with the formation of Si-Si and Si-Sn bonds, respectively. The products [Me(3)Si-Si((Me)pz)(3)] (6) and [Me(3)Sn-Si((Me)pz)(3)] (7) and [Ph(3)Sn-Si((Me)pz)(3)] (8) are the first backbone-functionalized derivatives originating from the tris(pyrazolyl)silanide. Overall, it could be concluded that the anionic ligand backbone of (Me)Tpsd is much more accessible for electrophiles compared to the carbon analogue ([C((Me)pz)(3)](-), (Me)Tpmd).