Lithium complexes with a [Cp*2Ti2F7]−ligand: 19F NMR probe for lithium solvation

Abstract

Reaction of the in situ prepared lithium fluoride with [Cp*TiF₃]₂ afforded [{Li(Cp*₂Ti₂F₇)}₂(THF)₂]·2THF, 3·2THF. The addition of 12-crown-4 to a THF solution of 3·2THF results in [{Li(Cp*₂Ti₂F₇)}₂(μ₂-η¹:η¹-12-crown-4)]·(12-crown-4), 4·(12-crown-4). In the solid state structures of 3·2THF and 4·(12-crown-4), which consist of dimeric [Li(Cp*₂Ti₂F₇)]₂ units, the lithium atom is coordinated by three fluorine atoms and an oxygen atom from the ether. Dimeric and monomeric (with respect to lithium) species were observed in solution of 3·2THF or 4·(12-crown-4). The solvation of the lithium atom in monomeric species [Li(Cp*₂Ti₂F₇)S_n] with S = CDCl₃, 12-crown-4, THF-d₈, was studied by variable temperature ¹⁹F NMR spectroscopy. Slow exchange of coordinated deuterated trichloromethane and 12-crown-4 on lithium ion was observed in a CDCl₃/12-crown-4 solution of 4·(12-crown-4) by ¹⁹F NMR spectroscopy up to 302 K.