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Alkali Metal Di-tert-butyl Phosphates: Single-Source Precursors for Homo- and Heterometallic Inorganic Phosphate Materials
Journal
Inorganic Chemistry
ISSN
00201669
Date Issued
2022-05-09
Author(s)
Verma, Sonam
Murugavel, Ramaswamy
Abstract
The reaction of alkali metal acetates, M(OAc)· nH2O (M = Li, Na, K), with thermally and hydrolytically unstable di-tert-butylphosphate ((tBuO)2PO2H, 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)]n (1), [Na(μ-dtbp)]n (2), and [K4(μ-dtbp)4(μ-H2O)3]n (3). 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 3, which has been further employed as a precursor for the synthesis of a mixed-metal phosphate polymer [CaK(μ-H2O)3(μdtbp)3]n (4) by reacting 3 with Ca(OAc)2. Compounds 1−4 have been characterized by various analytical and spectroscopic techniques. Molecular structures of 1−4 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 1−4 reveals the loss of thermally labile tert-butyl substituents of the organophosphate ligands to form organic-free phosphate materials in the temperature range 300−500 °C. Solvothermal decomposition of 1−3 in boiling toluene leads to the formation of corresponding dihydrogen phosphates M(H2PO4) (M = Li, Na, and K). The thermal decomposition of heterometallic 4 in the temperature range 400−800 °C leads to the formation of phase-pure mixed-metal calcium potassium metaphosphate CaK(PO3)3
Volume
61