PUB - Publikationen an der Universität Bielefeld

Silicon(IV) halides [{(Et ₃ B)anIPr}SiHCl ₂ ] ( 4 ) and [{(Et ₃ B)anIPr}SiBr ₃ ] ( 5 ) based on an anionic N ‐heterocyclic carbene (NHC) ligand (i.e., {(Et ₃ B)anIPr} = (Et ₃ B)C=C(H){N(Dipp)} ₂ C, Dip p = 2,6‐ i Pr ₂ C ₆ H ₃ ) are reported as crystalline solids. Compounds 4 and 5 featuring a four‐coordinated Si(IV) atom are prepared by reacting [Li{(Et ₃ B)anIPr}] ( 3 ) with HSiCl ₃ and SiBr ₄ , respectively. 4 and 5 are characterized by spectroscopic and X‐ray diffraction methods. Density functional theory (DFT) calculations have been performed to elucidate the electronic structures as well as the fluoride ion affinities (FIAs) of 4 and 5 . The calculated FIA, a measure of Lewis acidity, of 4 and 5 is about 46 or 55 kJ/mol larger than that of HSiCl ₃ and SiBr ₄ , respectively.