A novel molecular gallium phosphonate cage containing sandwiched lithium ions: synthesis, structure, and reactivity

Abstract

The reaction between tert-butylphosphonic acid and an equimolar quantity of LiGaMe₄ in THF and n-hexane (1:1) yields the first molecular lithium gallium phosphonate Li⁴[(MeGa)₆(μ₃-O)₂(t-BuPO₃)₆]·(THF)₄ (1) in 70% yield. Compound 1 has been fully characterized by means of analytical and spectroscopic techniques as well as a single crystal X-ray diffraction study. Compound 1 represents the first molecular ionic gallophosphonate cage which contains coordinated lithium ions in the form of a one-dimensional wire and can be regarded as a potential precursor for the subsequent synthesis of molecular sieves and ion conductors. Compound 1 is unreactive toward air and moisture at room temperature. Treatment of 1 with D₂O even at 70 °C does not lead to the hydrolysis of the Ga-C bonds. Treatment of a benzene-d₆ solution of 1 with 12-crown-4 followed by D₂O leads to the facile conversion of the product into the neutral cubic gallium phosphonate cage [t-BuPO₃GaMe]₄ (2).