Alkali Metal Di--butyl Phosphates: Single-Source Precursors for Homo- and Heterometallic Inorganic Phosphate Materials.

The reaction of alkali metal acetates, M(OAc)·HO (M = Li, Na, K), with thermally and hydrolytically unstable di--butylphosphate ((BuO)POH, dtbp-H) in a 1:1 molar ratio in MeOH at room temperature leads to clean formation of group 1 metal phosphates [Li(μ-dtbp)] (), [Na(μ-dtbp)] (), and [K(μ-dtbp)(μ-HO)] (). All three compounds are essentially M/L 1:1 complexes. Owing to the presence of larger potassium ions, additional coordinated water molecules are found in , which has been further employed as a precursor for the synthesis of a mixed-metal phosphate polymer [CaK(μ-HO)(μ-dtbp)] () by reacting with Ca(OAc). Compounds - have been characterized by various analytical and spectroscopic techniques. Molecular structures of - have been established in the solid state by single-crystal X-ray diffraction studies, which reveal them to be one-dimensional polymers, where the adjacent metal centers are connected through -O-P-O- bridges formed by the dtbp ligand. These complexes are rare examples of analytically pure alkali metal alkyl phosphates bearing no additional N-donor ligands (other than dtbp ligands, only water molecules are coordinated to the metal centers). Therefore, these compounds can be employed as single-source precursors (SSPs) for nano-sized ceramic phosphates. The thermogravimetric analysis of - reveals the loss of thermally labile -butyl substituents of the organophosphate ligands to form organic-free phosphate materials in the temperature range 300-500 °C. Solvothermal decomposition of - in boiling toluene leads to the formation of corresponding dihydrogen phosphates M(HPO) (M = Li, Na, and K). The thermal decomposition of heterometallic in the temperature range 400-800 °C leads to the formation of phase-pure mixed-metal calcium potassium metaphosphate CaK(PO).