Solid-state and solution structures of some lithium salts of tetraphenyldisiloxanediolate(2–) and the lithium-bridged compounds Li2[M(OSiPh2OSiPh2O)3·3py](py = pyridine, M = Zr or Hf)

Abstract

The compound [{Si₂Ph₄O(OLi)₂}₂·3(C₄H₈O₂)]_∞ was formed in a 2 : 1 reaction between n-butyllithium and tetraphenyldisiloxanediol in dioxane and its solid-state structure was determined by single-crystal X-ray diffraction. Variable-temperature ⁷Li and ambient temperature ²⁹Si NMR studies on [²H₈]toluene solutions of this and the related pyridine (py) adduct [Si₂Ph₄O(OLi)₂·2py]₂ were carried out. The cyclic hafnasiloxane Li₂[[graphic omitted])₃]·3py·3C₆H₆ was isolated from a 3 : 1 reaction between [Si₂Ph₄O(OLi)₂·2thf]₂(thf = tetrahydrofuran) and HfCl₄ and its structure determined by single-crystal X-ray diffraction. The variable-temperature ⁷Li NMR spectra of this and the related zirconium compound show that there is rapid exchange between non-equivalent lithium environments. Lithium hopping between available equivalent environments is inferred by the equilibration of the three distinct silicon environments in the structure as seen by ²⁹Si NMR studies.