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.