Lipophilic bismuth phosphates: a molecular tetradecanuclear cage and a 1D-coordination polymer. Synthesis, structure and conversion to BiPO4

Abstract

The reaction of the phosphate monoester {(ArO)PO(OH)₂} (Ar = 2,6-i-Pr₂C₆H₃) with BiPh₃ in a 1 : 1 ratio in refluxing toluene afforded a tetradecabismuth-oxo-phosphate cage [{(ArO)PO₃}₁₀{(ArO)PO₂OH}₂(Bi₁₄O₁₀)·2(CH₃OH)]·3C₆H₁₂·3CH₃OH·2H₂O (Ar = 2,6-i-Pr₂C₆H₃) (1). On the other hand the reaction of the phosphate diester {(^tBuO)₂PO(OH)} with BiPh₃ in a 1 : 1 ratio at room temperature in ethanol afforded the 1D-coordination polymer [Bi(C₆H₅)₂(^tBuO)₂PO₂]_n (2). The molecular structure of 1 reveals that the cage is comprised of a central planar Bi₆ rim and two Bi₄ poles. The entire aggregate is held together by multiple coordination of O²⁻, [(ArO)P(O)(OH)]⁻, [(ArO)PO₃]²⁻ and methanol ligands. 2 is a 1D-coordination polymer where adjacent bismuth is bridged by isobidentate [(^tBuO)₂PO₂]⁻ ligands. In solution, however, 2 decomposes into the monomeric repeat unit [Ph₂Bi{(^tBuO)₂PO₂}] which is indicated by ESI-MS studies. Thermolysis of 1 and 2 at 700 °C affords a pure phase of BiPO₄.