Syntheses, structures, and reactivity of poly(pyrazolyl)silanes, -disilanes, and the ambidentate κ1Si/κ3N-coordinating tris(3,5-dimethylpyrazolyl)silanide ligand [Si(3,5-Me2pz)3]− (MeTpsd)

Abstract

The reaction conditions for the synthesis [Si₂(^Mepz)₆] (1) and [Si(^Mepz)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(^Mepz)₃]⁻, ^MeTpsd). Within the monomeric lithium salt [Li(thf)(^MeTpsd)] (5), the ambidentate silanide ligand is bound in a κ³N-fashion to the Li cation, featuring an uncoordinated, anionic silicon bridgehead. Treatment of the silanide with various electrophiles such as Me₃SiCl, Me₃SnCl and Ph₃SnCl gave in each case the expected salt metathesis reaction with the formation of Si–Si and Si–Sn bonds, respectively. The products [Me₃Si–Si(^Mepz)₃] (6) and [Me₃Sn–Si(^Mepz)₃] (7) and [Ph₃Sn–Si(^Mepz)₃] (8) are the first backbone-funtionalized derivatives originating from the tris(pyrazolyl)silanide. Overall, it could be concluded that the anionic ligand backbone of ^MeTpsd is much more accessible for electrophiles compared to the carbon analogue ([C(^Mepz)₃]⁻, ^MeTpmd).