3,5‐Dimethylpyrazolyl‐Substituted Di‐ and Trisiloxanes

Abstract

The synthesis and characterization of di‐ and trisiloxanes with 3,5‐dimethylpyrazolyl (pz*) moieties are presented. Disiloxanes of the type O(SiMe3–npz*n)2 (n = 1, 2, and 3 in 2, 3, and 4, respectively) are easily accessible through a trans‐silylation approach. Crystal structure analyses of compound 4 and the two side products 5 and 6 illustrate different coordination motifs of pz* (terminal vs. bridging) in the disiloxane system. The reaction of O2Si3Cl8 with Me3Sipz* led to the unsymmetrically substituted trisiloxane pz*3SiO‐Sipz*2O‐SiCl2pz* (7) with bridging pz* units and tetra‐ and pentacoordinate silicon atoms and the fully pyrazolyl‐substituted trisiloxane O2Si3pz*8 (8), depending on the choice of the reaction conditions. The 29Si NMR properties of 7 were investigated by 29Si CP/MAS NMR spectroscopy and supporting quantum chemical calculations analyzing the principal components of the chemical‐shift tensor for all three silicon atoms in this molecule.

(3,5-Dimethyl-1H-pyrazol-1-yl)trimethylsilane

“…The title compound (3,5-dimethyl-1H-pyrazol-1-yl)trimethylsilane is a key compound in the preparation of different (3,5-dimethylpyrazolyl)silanes by transsilylation (Armbruster et al, 2009;Bitto et al, 2012Bitto et al, , 2013Bitto et al, , 2016a. The solid-state structure of this compound has never been determined, since it is a liquid at room temperature.…”